Patent Publication Number: US-2022220696-A1

Title: Shovel and controller for shovel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application filed under 35 U.S.C. 111(a) claiming benefit under 35 U.S.C. 120 and 365(c) of PCT International Application No. PCT/JP2020/037216, filed on Sep. 30, 2020 and designating the U.S., which claims priority to Japanese Patent Application No. 2019-180418, filed on Sep. 30, 2019. The entire contents of the foregoing applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to shovels and controllers for shovels. 
     Description of Related Art 
     For shovels, a technique to move a predetermined working part (for example, the teeth tips or back surface) of a bucket along an intended construction plane according as an operator operates an arm has been known. 
     SUMMARY 
     According to an aspect of the present invention, a shovel includes an attachment including a boom, an arm, and a bucket and a hardware processor configured to move the attachment to move the working part of the bucket along an intended construction plane. Multiple regions between which a control command for the movement of the bucket generated by the hardware processor differs are set in the vicinity of a bend of the intended construction plane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a shovel; 
         FIG. 2  is a top plan view of the shovel; 
         FIG. 3  is a diagram illustrating an example configuration of a hydraulic system of the shovel; 
         FIG. 4A  is a diagram illustrating a constituent part of an operation system associated with an arm in the hydraulic system of the shovel; 
         FIG. 4B  is a diagram illustrating a constituent part of an operation system associated with a boom in the hydraulic system of the shovel; 
         FIG. 4C  is a diagram illustrating a constituent part of an operation system associated with a bucket in the hydraulic system of the shovel; 
         FIG. 4D  is a diagram illustrating a constituent part of an operation system associated with an upper swing structure in the hydraulic system of the shovel; 
         FIG. 5  is a diagram illustrating an example of an electric operating device; 
         FIG. 6  is a block diagram illustrating an overview of an example of a configuration related to a machine guidance function and a machine control function of the shovel; 
         FIG. 7A  is a diagram illustrating an example of a motion based on the machine control function of the shovel; 
         FIG. 7B  is a diagram illustrating an example of a motion based on the machine control function of the shovel; 
         FIG. 8A  is a functional block diagram illustrating an example of a detailed configuration related to the machine control function of the shovel; 
         FIG. 8B  is a functional block diagram illustrating an example of a detailed configuration related to the machine control function; and 
         FIG. 9  is a diagram illustrating another example of a motion based on the machine control function of the shovel. 
     
    
    
     DETAILED DESCRIPTION 
     According to the related-art technique, an intended construction plane constituted of a single plane is a target. Therefore, no consideration is given to the presence of a bend where an inclination discontinuously changes between two planes (contacting planes) in the intended construction plane, such as the intersection of a horizontal plane and a slope in an intended construction plane constituted of the horizontal plane and the slope, for example. Therefore, the shovel may be unable to, for example, make an appropriate transition from the state where the shovel moves the working part of the bucket along the horizontal plane to the state where the shovel moves the working part of the bucket along the slope. 
     Therefore, it is desired to provide a technique that makes it possible for a shovel to appropriately move the working part of a bucket along an intended construction plane in the vicinity of a bend of the intended construction plane. 
     According to an embodiment of the present invention, it is possible for a shovel to appropriately move the working part of a bucket along an intended construction plane in the vicinity of a bend of the intended construction plane. 
     An embodiment of the invention is described below with reference to the drawings. 
     [Shovel Overview] 
     First, an overview of a shovel  100  according to this embodiment is given with reference to  FIGS. 1 and 2 . 
       FIGS. 1 and 2  are a side view and a top plan view, respectively, of the shovel  100  according to this embodiment. 
     The shovel  100  according to this embodiment includes a lower traveling structure  1 ; an upper swing structure  3  swingably mounted on the lower traveling structure  1  via a swing mechanism  2 ; a boom  4 , an arm  5  and a bucket  6  that constitute an attachment AT; and a cabin  10 . 
     As described below, the lower traveling structure  1  includes a pair of left and right crawlers  1 C, specifically, a left crawler  1 CL and a right crawler  1 CR. The left crawler  1 CL and the right crawler  1 CR are hydraulically driven by travel hydraulic motors  2 M (specifically, travel hydraulic motors  2 ML and  2 MR), so that the lower traveling structure  1  causes the shovel  100  to travel. 
     The upper swing structure  3  is driven by a swing hydraulic motor  2 A to swing relative to the lower traveling structure  1 . 
     The boom  4  is pivotably attached to the front center of the upper swing structure  3  to be movable upward and downward. The arm  5  is pivotably attached to the distal end of the boom  4  to be pivotable upward and downward. The bucket  6  is pivotably attached to the distal end of the arm  5  to be pivotable upward and downward. The boom  4 , the arm  5 , and the bucket  6  are hydraulically driven by a boom cylinder  7 , an arm cylinder  8 , and a bucket cylinder  9 , respectively, which serve as hydraulic actuators. 
     The bucket  6  includes a concave bottom plate constituted of an upper surface  6 _ 1 , a curved surface  6 _ 2 , a back surface  6 _ 3 , etc., and a left and a right end plate that close the left end and the right end, respectively, of the bottom plate. The bottom plate and the left and right end plates form an inner space for accommodating earth or the like. Furthermore, multiple teeth  6 _ 4  are provided widthwise (laterally) at the leading edge of the bucket  6  (the back surface  6 _ 3 ). 
     The bucket  6  is an example of an end attachment. Instead of the bucket  6 , another end attachment, for example, a slope bucket, a dredging bucket, a breaker or the like may be attached to the distal end of the arm  5  in accordance with the contents of work or the like. 
     The cabin  10  is a cab in which an operator rides, and is mounted on the front left of the upper swing structure  3 . 
     The shovel  100  moves driven elements such as the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , and the bucket  6  in response to operations of the operator riding in the cabin  10 . Furthermore, the shovel  100  may move the driven elements such as the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , and the bucket  6  in response to a remote control signal corresponding to the remote control of an operator of a predetermined external apparatus, received from the external apparatus through a communications device. 
     Furthermore, the shovel  100  implements the function of automatically moving at least one of the driven elements such as the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , and the bucket  6  (hereinafter “automatic operation function”). 
     The automatic operation function may include the function of automatically move a driven element (hydraulic actuator) other than a driven element (hydraulic actuator) to be operated in response to the operator&#39;s operation or remote control of an operating device  26  (so-called “semi-automatic operation function” or “machine control function”). Furthermore, the automatic operation function may also include the function of automatically moving at least one of driven elements (hydraulic actuators) without the operator&#39;s operation or remote control of the operating device  26  (so-called “fully automatic operation function”). Furthermore, the semi-automatic operation function and the fully automatic operation function may include not only a mode in which the motion details of a driven element (hydraulic actuator) to be automatically operated are automatically determined according to predetermined rules but also a mode in which the shovel  100  autonomously performs various determinations and the motion details of a driven element (hydraulic actuator) to be automatically operated are autonomously determined following the determination results (so-called “autonomous operation function”). 
     [Shovel Configuration] 
     Next, a configuration of the shovel  100  is described with reference to  FIG. 3 ,  FIG. 4  ( FIGS. 4A through 4D ) and  FIG. 5  in addition to  FIGS. 1 and 2 . 
       FIG. 3  is a diagram illustrating an example configuration of the hydraulic system of the shovel  100 .  FIGS. 4A through 4D  are diagrams illustrating examples of constituent parts of operation systems associated with the arm  5 , the boom  4 , the bucket  6 , and the upper swing structure  3 , respectively, in the hydraulic system of the shovel  100  according to this embodiment.  FIG. 5  is a diagram illustrating an example of the operating device  26  of an electric type. 
     The hydraulic system of the shovel  100  according to this embodiment includes an engine  11 , a regulator  13 , a main pump  14 , a pilot pump  15 , a control valve  17 , the operating device  26 , discharge pressure sensors  28 L and  28 R, operating pressure sensors  29 LA,  29 LB,  29 RA,  29 RB,  29 DL, and  29 DR, and a controller  30 . Furthermore, as described above, the hydraulic system of the shovel  100  according to this embodiment includes hydraulic actuators such as the travel hydraulic motors  2 ML and  2 MR, the swing hydraulic motor  2 A, the boom cylinder  7 , the arm cylinder  8 , and the bucket cylinder  9  that hydraulically drive the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , and the bucket  6 , respectively. 
     The engine  11  is the main power source of the hydraulic system and is mounted on the back of the upper swing structure  3 , for example. Specifically, the engine  11  rotates constantly at a preset target rotational speed under the direct or indirect control of the controller  30  to drive main pumps  14 L and  14 R and the pilot pump  15 . The engine  11  is, for example, a diesel engine fueled with diesel fuel. 
     Regulators  13 L and  13 R control the discharge quantities of the main pumps  14 L and  14 R, respectively. For example, the regulator  13  adjusts the angle (tilt angle) of the swash plate of the main pump  14  in response to a control command from the controller  30 . 
     The main pump  14 L and  14 R are, for example, mounted on the back of the upper swing structure  3  the same as the engine  11 , and as described above, are driven by the engine  11  to supply hydraulic oil to the control valve  17  through a high-pressure hydraulic line. The main pumps  14 L and  14 R are, for example, variable displacement hydraulic pumps, and their discharge flow rates (discharge pressures) are controlled by the regulator  13  adjusting the tilt angle of the swash plate to adjust a piston stroke length under the control of the controller  30  as described above. 
     The pilot pump  15  is, for example, mounted on the back of the upper swing structure  3  and supplies a pilot pressure to the operating device  26  via a pilot line. The pilot pump  15  is, for example, a fixed displacement hydraulic pump and is driven by the engine  11  as described above. 
     The control valve  17  is a hydraulic control device that is mounted in the center of the upper swing structure  3  and controls a hydraulic drive system according to the operator&#39;s operation or in response to a control command from the automatic operation function of the shovel  100 , for example. As described above, the control valve  17  is connected to the main pump  14  via a high-pressure hydraulic line, and selectively supplies hydraulic oil supplied from the main pump  14  to the hydraulic actuators (the travel hydraulic motors  2 ML and  2 MR, the swing hydraulic motor  2 A, the boom cylinder  7 , the arm cylinder  8 , and the bucket cylinder  9 ) in accordance with the operating state of the operating device  26  or in response to a control command from the automatic operation function of the shovel  100 . Specifically, the control valve  17  includes control valves  171  through  174 ,  175 L,  175 R,  176 L and  176 R that control the flow rate and flow direction of hydraulic oil supplied from the main pump  14  to the individual hydraulic actuators. Hereinafter, the control valves  175 L and  175 R may be collectively or individually referred to as the control valve  175 . Furthermore, the control valves  176 L and  176 R may be collectively or individually referred to as the control valve  176 . 
     The control valves  171  and  172  correspond to the travel hydraulic motor  2 ML and the travel hydraulic motor  2 MR, respectively. The control valve  173  corresponds to the swing hydraulic motor  2 A. The control valve  174  corresponds to the bucket cylinder  9 . The control valve  175  corresponds to the boom cylinder  7 . The control valve  176  corresponds to the arm cylinder  8 . 
     The operating device  26  is provided near the operator seat of the cabin  10  and serves as an operation input device that the operator uses to operate (move) driven elements (such as the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , and the bucket  6 ). In other words, the operating device  26  is an operation input device that the operator uses to operate (move) hydraulic actuators (namely, the travel hydraulic motors  2 ML and  2 MR, the swing hydraulic motor  2 A, the boom cylinder  7 , the arm cylinder  8 , the bucket cylinder  9 , etc.) that drive corresponding driven elements. 
     As illustrated in  FIGS. 4A through 4D , the operating device  26  is, for example, of a hydraulic pilot type to output a pilot pressure commensurate with its operating state to the secondary side. The operating device  26  is connected to the control valve  17  directly or via a below-described shuttle valve  32  provided in a hydraulic line on its secondary side through the hydraulic line on its secondary side. This allows pilot pressures commensurate with the states of operating the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , the bucket  6 , etc., with the operating device  26  to be input to the control valve  17 . Therefore, the control valve  17  can drive their respective hydraulic actuators in accordance with the operating states in the operating device  26 . 
     The operating device  26  includes a left operating lever  26 L and a right operating lever  26 R for operating the attachment AT, namely, the boom  4  (the boom cylinder  7 ), the arm  5  (the arm cylinder  8 ), the bucket  6  (the bucket cylinder  9 ), and the upper swing structure  3 . Furthermore, the operating device  26  includes travel levers  26 D for operating the lower traveling structure  1 . The travel levers  26 D include a left travel lever  26 DL for operating the left crawler  1 CL (the travel hydraulic motor  2 ML) and a right travel lever  26 DR for operating the right crawler  1 CR (the travel hydraulic motor  2 MR). 
     The left operating lever  26 L is used to swing the upper swing structure  3  and operate the arm  5 . The left operating lever  26 L is operated in a forward or a backward direction relative to the operator in the cabin  10  (namely, the forward or the backward direction of the upper swing structure  3 ) to output a control pressure commensurate with the amount of lever operation (pilot pressure) to a secondary-side pilot line connected to a pilot port of the control valve  176 , using hydraulic oil discharged from the pilot pump  15 . Furthermore, the left operating lever  26 L is operated in a rightward or a leftward direction relative to the operator in the cabin  10  (namely, the rightward or the leftward direction of the upper swing structure  3 ) to output a control pressure commensurate with the amount of lever operation (pilot pressure) to a secondary-side pilot line connected to a pilot port of the control valve  173 , using hydraulic oil discharged from the pilot pump  15 . 
     The right operating lever  26 R is used to operate the boom  4  and operate the bucket  6 . The right operating lever  26 R is operated in the forward or the backward direction relative to the operator in the cabin  10  to output a control pressure commensurate with the amount of lever operation (pilot pressure) to a secondary-side pilot line connected to a pilot port of the control valves  175 , using hydraulic oil discharged from the pilot pump  15 . Furthermore, the right operating lever  26 R is operated in the rightward or the leftward direction to output a control pressure commensurate with the amount of lever operation (pilot pressure) to a secondary-side pilot line connected to the control valve  174 , using hydraulic oil discharged from the pilot pump  15 . 
     As described above, the left travel lever  26 DL is used to operate the left crawler  1 CL, and may be configured to work together with an undepicted left travel pedal. The left travel lever  26 DL is operated in the forward or the backward direction relative to the operator in the cabin  10  to output a control pressure commensurate with the amount of lever operation (pilot pressure) to a secondary-side pilot line connected to the control valve  171 , using hydraulic oil discharged from the pilot pump  15 . The secondary-side pilot lines corresponding to the operations of the left travel lever  26 DL in the forward direction and the backward direction may be directly connected to the corresponding pilot ports of the control valve  171 . This reflects the operation details of the left travel lever  26 DL in the spool position of the control valve  171  that drives the travel hydraulic motor  2 ML. 
     As described above, the right travel lever  26 DR is used to operate the right crawler  1 CR, and may be configured to work together with an undepicted right travel pedal. The right travel lever  26 DR is operated in the forward or the backward direction relative to the operator in the cabin  10  to output a control pressure commensurate with the amount of lever operation (pilot pressure) to a secondary-side pilot line connected to the control valve  172 , using hydraulic oil discharged from the pilot pump  15 . The secondary-side pilot lines corresponding to the operations of the right travel lever  26 DR in the forward direction and the backward direction may be directly connected to the corresponding pilot ports of the control valve  172 . That is, the operation details of the right travel lever  26 DR are reflected in the spool position of the control valve  172  that drives the travel hydraulic motor  2 MR. 
     Furthermore, as illustrated in  FIG. 5 , the operating device  26  (the left operating lever  26 L, the right operating lever  26 R, the left travel lever  26 DL, and the right travel lever  26 DR) may be of an electric type that outputs an electrical signal corresponding to its operation details. In this case, an operation signal from the operating device  26  is input to the controller  30 , and the controller  30  controls each of the control valves  171  through  176  in the control valve  17  according to the input operation signal, thereby achieving the operations of various hydraulic actuators corresponding to the operation details of the operating device  26 . For example, the control valves  171  through  176  in the control valve  17  may be electromagnetic solenoid spool valves that are driven by a command from the controller  30 . Furthermore, for example, a hydraulic pressure control valve that operates in response to an electrical signal from the controller  30  (for example, a solenoid proportional valve) (hereinafter, “hydraulic pressure control valve for operation”) may be placed between the pilot pump  15  and the pilot ports of each of the control valves  171  through  176 . In this case, when the operating device  26  of an electric type is manually operated, the controller  30  can operate each of the control valves  171  through  176  according to the operation details of the operating device  26  by controlling the hydraulic pressure control valve for operation to increase or decrease a pilot pressure, using an electrical signal commensurate with its direction of operation and amount of operation (for example, amount of lever operation). 
     The pilot circuit of this example ( FIG. 5 ) includes a solenoid valve  60  for the operation of raising the boom  4  (hereinafter “boom raising operation) and a solenoid valve  62  for the operation of lowering the boom  4  (hereinafter “boom lowering operation”) as the above-described hydraulic pressure control valve for operation. 
     The solenoid valve  60  is configured to be able to control the pressure of hydraulic oil in an oil conduit (pilot line) connecting the pilot pump  15  and the boom-raising-side pilot port of the control valve  17  of a pilot pressure-operated type (specifically, the control valves  175 L and  175 R (see  FIG. 3 )). 
     The solenoid valve  62  is configured to be able to control the pressure of hydraulic oil in an oil conduit (pilot line) connecting the pilot pump  15  and the boom-lowering-side pilot port of the control valve  17  (the control valves  175 L and  175 R). 
     When the boom  4  (the boom cylinder  7 ) is manually operated, the controller  30  generates a boom raising operation signal (electrical signal) or a boom lowering operation signal (electrical signal) in response to an operation signal (electrical signal) output by the right operating lever  26 R (an operation signal generating part  26 Ra). The operation signal (electrical signal) output from the right operating lever  26 R represents its operation details (for example, the amount of operation and the direction of operation). The boom raising operation signal (electrical signal) and the boom lowering operation signal (electrical signal) output by the controller  30  change according to the operation details (the amount of operation and the direction of operation) of the right operating lever  26 R. 
     Specifically, when the right operating lever  26 R is operated in a boom raising direction, the controller  30  outputs a boom raising operation signal (electrical signal) commensurate with the amount of operation to the solenoid valve  60 . The solenoid valve  60  operates in response to the input electrical signal (boom raising operation signal) to control a pilot pressure applied to the boom-raising-side pilot ports of the control valves  175 L and  175 R, namely, a boom raising operation signal as a pressure signal. Likewise, when the right operating lever  26 R is operated in a boom lowering direction, the controller  30  outputs a boom lowering operation signal (electrical signal) commensurate with the amount of operation to the solenoid valve  62 . The solenoid valve  62  operates in response to the input electrical signal (boom lowering operation signal) to control a pilot pressure applied to the boom-lowering-side pilot ports of the control valves  175 L and  175 R, namely, a boom lowering operation signal as a pressure signal. This enables the control valve  17  to cause the boom cylinder  7  (the boom  4 ) to move according to the operation details of the right operating lever  26 R. 
     When the boom  4  is automatically operated by the automatic operation function, the controller  30 , for example, generates a boom raising operating signal (electrical signal) or a boom lowering operation signal (electrical signal) in response to an automatic operation signal (electrical signal) output by an automatic operation signal generating part  30 A. The automatic operation signal may be, for example, either an electrical signal generated by a control device (for example, a control device that controls the automatic operation function) other than the controller  30  as illustrated in  FIG. 5  or an electrical signal generated by the controller  30 . 
     The arm  5  (the arm cylinder  8 ), the bucket  6  (the bucket cylinder  9 ), the upper swing structure  3  (the swing hydraulic motor  2 A), and the lower traveling structure  1  (the travel hydraulic motors  2 ML and  2 MR), whose movements are based on similar pilot circuits, move the same as the boom  4  (the boom cylinder  7 ). 
     The discharge pressure sensors  28 L and  28 R detect the discharge pressures of the main pumps  14 L and  14 R, respectively. Detection signals corresponding to the discharge pressures detected by the discharge pressure sensors  28 L and  28 R are fed into the controller  30 . 
     The operating pressure sensors  29 LA,  29 LB,  29 RA,  29 RB,  29 DL and  29 DR detect the secondary-side pilot pressure of the operating device  26 , namely, pilot pressures commensurate with the states of operating corresponding motion elements (namely, hydraulic actuators) with the operating device  26 . The detection signals of pilot pressures commensurate with the states of operating the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , the bucket  6 , etc., with the operating device  26  generated by the operating pressure sensors  29 LA,  29 LB,  29 RA,  29 RB,  29 DL and  29 DR are fed into the controller  30 . 
     The operating pressure sensor  29 LA detects the details (for example, the direction of operation and the amount of operation) of the operator&#39;s forward or backward operation on the left operating lever  26 L in the form of the pressure of hydraulic oil (hereinafter “operating pressure”) in a secondary-side pilot line of the left operating lever  26 L. 
     The operating pressure sensor  29 LB detects the details (for example, the direction of operation and the amount of operation) of the operator&#39;s rightward or leftward operation on the left operating lever  26 L in the form of the operating pressure of a secondary-side pilot line of the left operating lever  26 L. 
     The operating pressure sensor  29 RA detects the details (for example, the direction of operation and the amount of operation) of the operator&#39;s forward or backward operation on the right operating lever  26 R in the form of the operating pressure of a secondary-side pilot line of the right operating lever  26 R. 
     The operating pressure sensor  29 RB detects the details (for example, the direction of operation and the amount of operation) of the operator&#39;s rightward or leftward operation on the right operating lever  26 R in the form of the operating pressure of a secondary-side pilot line of the right operating lever  26 R. 
     The operating pressure sensor  29 DL detects the details (for example, the direction of operation and the amount of operation) of the operator&#39;s forward or backward operation on the left travel lever  26 DL in the form of the operating pressure of a secondary-side pilot line of the left travel lever  26 DL. 
     The operating pressure sensor  29 DR detects the details (for example, the direction of operation and the amount of operation) of the operator&#39;s forward or backward operation on the right travel lever  26 DR in the form of the operating pressure of a secondary-side pilot line of the right travel lever  26 DR. 
     The operation details of the operating device  26  (the left operating lever  26 L, the right operating lever  26 R, the left travel lever  26 DL, and the right travel lever  26 DR) may also be detected by sensors other than an operating pressure sensor  29  (for example, potentiometers or the like attached to the left operating lever  26 L, the right operating lever  26 R, the left travel lever  26 DL, and the right travel lever  26 DR). Furthermore, when the operating device  26  is of an electric type, the operating pressure sensors  29 LA,  29 LB,  29 RA,  29 RB,  29 DL and  29 DR are omitted. 
     The controller  30  (an example of a control device) is, for example, provided in the cabin  10 , and controls the driving of the shovel  100 . The functions of the controller  30  may be implemented by desired hardware or a desired combination of hardware and software. For example, the controller  30  is constituted mainly of a computer that includes a CPU (Central Processing Unit), a memory unit such as a RAM (Random Access Memory), a non-volatile secondary storage such as a ROM (Read Only Memory), and an external input/output interface unit. The controller  30  implements various functions by running various programs stored in the secondary storage on the CPU, for example. 
     One or more of the functions of the controller  30  may be implemented by another controller (control device). That is, the functions of the controller  30  may be distributed between and implemented by multiple controllers. 
     As illustrated in  FIG. 3 , in the hydraulic system of the shovel  100 , the part of the hydraulic system of a drive system that drives the hydraulic actuators circulates hydraulic oil from the main pump  14  driven by the engine  11  to a hydraulic oil tank by way of center bypass oil passages  40 L and  40 R or parallel oil passages  42 L and  42 R. 
     The center bypass oil passage  40 L starts at the main pump  14 L and ends at the hydraulic oil tank, passing through the control valves  171 ,  173 ,  175 L and  176 L, placed in the control valve  17 , in order. 
     The center bypass oil passage  40 R starts at the main pump  14 R and ends at the hydraulic oil tank, passing through the control valves  172 ,  174 ,  175 R and  176 R, placed in the control valve  17 , in order. 
     The control valve  171  is a spool valve that supplies hydraulic oil discharged from the main pump  14 L to the travel hydraulic motor  2 ML and discharges hydraulic oil discharged by the travel hydraulic motor  2 ML to the hydraulic oil tank. 
     The control valve  172  is a spool valve that supplies hydraulic oil discharged from the main pump  14 R to the travel hydraulic motor  2 MR and discharges hydraulic oil discharged by the travel hydraulic motor  2 MR to the hydraulic oil tank. 
     The control valve  173  is a spool valve that supplies hydraulic oil discharged from the main pump  14 L to the swing hydraulic motor  2 A and discharges hydraulic oil discharged by the swing hydraulic motor  2 A to the hydraulic oil tank. 
     The control valve  174  is a spool valve that supplies hydraulic oil discharged from the main pump  14 R to the bucket cylinder  9  and discharges hydraulic oil in the bucket cylinder  9  to the hydraulic oil tank. 
     The control valves  175 L and  175 R are spool valves that supply hydraulic oil discharged by the main pumps  14 L and  14 R to the boom cylinder  7  and discharge hydraulic oil in the boom cylinder  7  to the hydraulic oil tank. 
     The control valves  176 L and  176 R are spool valves that supply hydraulic oil discharged by the main pumps  14 L and  14 R to the arm cylinder  8  and discharge hydraulic oil in the arm cylinder  8  to the hydraulic oil tank. 
     Each of the control valves  171 ,  172 ,  173 ,  174 ,  175 L,  175 R,  176 L and  176 R controls the flow rate or switches the direction of flow of hydraulic oil discharged from or supplied to a hydraulic actuator according to a pilot pressure applied to its pilot port. 
     The parallel oil passage  42 L supplies hydraulic oil from the main pump  14 L to the control valves  173 ,  175 L and  176 L in parallel with the center bypass oil passage  40 L. Specifically, the parallel oil passage  42 L is configured to diverge from the center bypass oil passage  40 L upstream of the control valve  171  to make it possible to supply hydraulic oil from the main pump  14 L to the control valves  173 ,  175 L and  176 L in parallel. This enables the parallel oil passage  42 L to supply hydraulic oil to a control valve further downstream when the flow of hydraulic oil through the center bypass oil passage  40 L is restricted or blocked by any of the control valves  171 ,  173  and  175 L. 
     The parallel oil passage  42 R supplies hydraulic oil from the main pump  14 R to the control valves  174 ,  175 R and  176 R in parallel with the center bypass oil passage  40 R. Specifically, the parallel oil passage  42 R is configured to diverge from the center bypass oil passage  40 R upstream of the control valve  172  to make it possible to supply hydraulic oil from the main pump  14 R to the control valves  174 ,  175 R and  176 R in parallel. This enables the parallel oil passage  42 R to supply hydraulic oil to a control valve further downstream when the flow of hydraulic oil through the center bypass oil passage  40 R is restricted or blocked by any of the control valves  172 ,  174  and  175 R. 
     The regulators  13 L and  13 R control the discharge quantities of the main pumps  14 L and  14 R by adjusting the tilt angles of the swash plates of the main pumps  14 L and  14 R, respectively, under the control of the controller  30  as described above. 
     The discharge pressure sensor  28 L detects the discharge pressure of the main pump  14 L, and a detection signal corresponding to the detected discharge pressure is fed into the controller  30 . The same is true for the discharge pressure sensor  28 R. This enables the controller  30  to control the regulators  13 L and  13 R according to the discharge pressures of the main pump  14 L and  14 R. 
     Negative control throttles (hereinafter “NC throttles”)  18 L and  18 R are provided between the most downstream control valves  176 L and  176 R and the hydraulic oil tank in the center bypass oil passages  40 L and  40 R, respectively. As a result, the flow of hydraulic oil discharged by the main pumps  14 L and  14 R is restricted by the NC throttles  18 L and  18 R. The NC throttles  18 L and  18 R generate control pressures for controlling the regulators  13 L and  13 R (hereinafter “NC pressures”). 
     NC pressure sensors  19 L and  19 R detect the NC pressures of the NC throttles  18 L and  18 R, respectively, and detection signals corresponding to the detected NC pressures are fed into the controller  30 . 
     The controller  30  may control the regulators  13 L and  13 R to control the discharge quantities of the main pumps  14 L and  14 R according to the discharge pressures of the main pumps  14 L and  14 R detected by the discharge pressure sensors  28 L and  28 R. For example, according as the discharge pressure of the main pump  14 L increases, the controller  30  may reduce the discharge quantity by adjusting the swash plate tilt angle of the main pump  14 L by controlling the regulator  13 L. The same is true for the regulator  13 R. This enables the controller  30  to perform full power control on the main pumps  14 L and  14 R such that the absorbed power of the main pumps  14 L and  14 R expressed as the product of discharge pressure and discharge quantity is prevented from exceeding the output power of the engine  11 . 
     Furthermore, the controller  30  may control the discharge quantities of the main pumps  14 L and  14 R by controlling the regulators  13 L and  13 R according to the NC pressures detected by the NC pressure sensors  19 L and  19 R. For example, the controller  30  reduces the discharge quantities of the main pumps  14 L and  14 R as the NC pressures increase and increases the discharge quantities of the main pumps  14 L and  14 R as the NC pressures decrease. 
     Specifically, in a standby state where none of the hydraulic actuators is operated in the shovel  100  (the state illustrated in  FIG. 3 ), hydraulic oil discharged from the main pumps  14 L and  14 R arrives at the NC throttles  18 L and  18 R through the center bypass oil passages  40 L and  40 R. The flow of hydraulic oil discharged from the main pumps  14 L and  14 R increase the NC pressures generated upstream of the NC throttles  18 L and  18 R. As a result, the controller  30  decreases the discharge quantities of the main pumps  14 L and  14 R to a minimum allowable discharge quantity to reduce pressure loss (pumping loss) during the passage of the discharged hydraulic oil through the center bypass oil passages  40 L and  40 R. 
     In contrast, when any of the hydraulic actuators is operated through the operating device  26 , hydraulic oil discharged from the main pump  14 L or  14 R flows into the operated hydraulic actuator via a control valve corresponding to the operated hydraulic actuator. The same is true for the case where any of the hydraulic actuators is remotely controlled or controlled according to an automatic control function. The flow of hydraulic oil discharged from the main pump  14 L or  14 R that arrives at the NC throttle  18 L or  18 R is reduced in amount or lost, so that the NC pressure generated upstream of the NC throttle  18 L or  18 R is reduced. As a result, the controller  30  can increase the discharge quantity of the main pump  14 L or  14 R to circulate sufficient hydraulic oil to the operated hydraulic actuator to ensure driving of the operated hydraulic actuator. 
     Furthermore, as illustrated in  FIGS. 3 and 4A through 4D , hydraulic system parts related to operation systems in the hydraulic system of the shovel  100  includes the pilot pump  15 , the operating device  26  (the left operating lever  26 L, the right operating lever  26 R, the left travel lever  26 DL, and the right travel lever  26 DR), proportional valves  31 AL,  31 AR,  31 BL,  31 BR,  31 CL,  31 CR,  31 DL and  31 DR, shuttle valves  32 AL,  32 AR,  32 BL,  32 BR,  32 CL,  32 CR,  32 DL and  32 DR, and pressure reducing proportional valves  33 AL,  33 AR,  33 BL,  33 BR,  33 CL,  33 CR,  33 DL and  33 DR. Hereinafter, the proportional valves  31 AL,  31 AR,  31 BL,  31 BR,  31 CL,  31 CR,  31 DL and  31 DR may be collectively or individually referred to as “proportional valve  31 .” Likewise, the shuttle valves  32 AL,  32 AR,  32 BL,  32 BR,  32 CL,  32 CR,  32 DL and  32 DR may be collectively or individually referred to as “shuttle valve  32 .” Likewise, the pressure reducing proportional valves  33 AL,  33 AR,  33 BL,  33 BR,  33 CL,  33 CR,  33 DL and  33 DR may be collectively or individually referred to as “pressure reducing proportional valve  33 .” 
     The proportional valve  31  is provided in a pilot line connecting the pilot pump  15  and the shuttle valve  32 , and is configured to be able to change its flow area (a cross-sectional area through which hydraulic oil can pass). The proportional valve  31  operates in response to a control command input from the controller  30 . This enables the controller  30  to supply hydraulic oil discharged from the pilot pump  15  to pilot ports of corresponding control valves (specifically, the control valves  173  through  176 ) in the control valve  17  via the proportional valve  31  and the shuttle valve  32  even when the operating device  26  is not operated by the operator. 
     The shuttle valve  32  includes two inlet ports and one outlet port, and outputs hydraulic oil having the higher one of pilot pressures input to the two inlet ports to the outlet port. Of the two inlet ports of the shuttle valve  32 , one is connected to the operating device  26  and the other is connected to the proportional valve  31 . The outlet port of the shuttle valve  32  is connected to a pilot port of a corresponding control valve in the control valve  17  through a pilot line. Therefore, the shuttle valve  32  can apply the higher one of a pilot pressure generated by the operating device  26  and a pilot pressure generated by the proportional valve  31  to a pilot port of a corresponding control valve. According to this, by causing a pilot pressure higher than a secondary-side pilot pressure output from the operating device  26  to be output from the proportional valve  31 , the controller  30  can control a corresponding control valve independent of the operator&#39;s operation of the operating device  26  to control the movement of the lower traveling structure  1 , the upper swing structure  3 , or the attachment AT. Therefore, by controlling the proportional valve  31 , the controller  30  can cause a hydraulic actuator to perform an operation corresponding to a control command from remote control performed by an operator of an external apparatus or from the automatic operation function. 
     The pressure reducing proportional valve  33  is provided in a pilot line connecting the operating device  26  and the shuttle valve  32 , and is configured to be able to change its flow area. The pressure reducing proportional valve  33  operates in response to a control command input from the controller  30 . This enables the controller  30  to force reduction of a pilot pressure output from the operating device  26  (specifically, the left operating lever  26 L, the right operating lever  26 R, the left travel lever  26 DL, or the right travel lever  26 DR) when the operating device  26  is operated by the operator. Therefore, even during the operation of the operating device  26 , the controller  30  can forcibly control or stop the movement of a hydraulic actuator corresponding to the operation of the operating device  26 . Furthermore, for example, even during the operation of the operating device  26 , the controller  30  can reduce a pilot pressure output from the operating device  26  to cause the pilot pressure output from the operating device  26  to be lower than a pilot pressure output from the proportional valve  31 . Therefore, by controlling the proportional valve  31  and the pressure reducing proportional valve  33 , the controller  30  can ensure that a desired pilot pressure is applied to a pilot port of a control valve in the control valve  17  irrespective of the operation details of the operating device  26 . 
     As illustrated in  FIG. 4A , the left operating lever  26 L is used in such a manner as to be tilted forward or backward to operate the arm cylinder  8  corresponding to the arm  5  by the operator. That is, when the left operating lever  26 L is tilted forward or backward, the target of operation of the left operating lever  26 L is the motion of the arm  5 . The left operating lever  26 L outputs a pilot pressure commensurate with the details of the forward or the backward operation to a secondary-side pilot line, using hydraulic oil discharged from the pilot pump  15 . 
     The shuttle valve  32 AL has two inlet ports: one connected to a secondary-side pilot line of the left operating lever  26 L corresponding to an operation in a direction to close the arm  5  (hereinafter “arm closing operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 AL, and has an outlet port connected to the right pilot port of the control valve  176 L and the left pilot port of the control valve  176 R. 
     The shuttle valve  32 AR has two inlet ports: one connected to a secondary-side pilot line of the left operating lever  26 L corresponding to an operation in a direction to open the arm  5  (hereinafter “arm opening operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 AR, and has an outlet port connected to the left pilot port of the control valve  176 L and the right pilot port of the control valve  176 R. 
     That is, the left operating lever  26 L applies a pilot pressure commensurate with the details of the forward or the backward operation to pilot ports of the control valves  176 L and  176 R through the shuttle valve  32 AL or  32 AR. Specifically, in response to the arm closing operation, the left operating lever  26 L outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 AL to apply the pilot pressure to the right pilot port of the control valve  176 L and the left pilot port of the control valve  176 R via the shuttle valve  32 AL. Furthermore, in response to the arm opening operation, the left operating lever  26 L outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 AR to apply the pilot pressure to the left pilot port of the control valve  176 L and the right pilot port of the control valve  176 R via the shuttle valve  32 AR. 
     The proportional valve  31 AL operates in response to a control current input from the controller  30 . Specifically, the proportional valve  31 AL outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 AL, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 AL to control a pilot pressure applied to the right pilot port of the control valve  176 L and the left pilot port of the control valve  176 R via the shuttle valve  32 AL. 
     The proportional valve  31 AR operates in response to a control current input from the controller  30 . Specifically, the proportional valve  31 AR outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 AR, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 AR to control a pilot pressure applied to the left pilot port of the control valve  176 L and the right pilot port of the control valve  176 R via the shuttle valve  32 AR. 
     That is, the proportional valves  31 AL and  31 AR can control a pilot pressure output to the secondary side such that the control valves  176 L and  176 R can stop at a desired valve position independent of the operating state of the left operating lever  26 L. 
     The pressure reducing proportional valve  33 AL operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 AL outputs a pilot pressure commensurate with the arm closing operation of the left operating lever  26 L directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 AL reduces the pilot pressure of a secondary-side pilot line corresponding to the arm closing operation of the left operating lever  26 L to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 AL. This enables the pressure reducing proportional valve  33 AL to forcibly control or stop the operation of the arm cylinder  8  corresponding to the arm closing operation on an as-needed basis even during the arm closing operation of the left operating lever  26 L. Furthermore, the pressure reducing proportional valve  33 AL can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 AL to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 AL from the proportional valve  31 AL even during the arm closing operation of the left operating lever  26 L. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the arm-closing-side pilot ports of the control valves  176 L and  176 R by controlling the proportional valve  31 AL and the pressure reducing proportional valve  33 AL. 
     The pressure reducing proportional valve  33 AR operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 AR outputs a pilot pressure commensurate with the arm opening operation of the left operating lever  26 L directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 AR reduces the pilot pressure of a secondary-side pilot line corresponding to the arm opening operation of the left operating lever  26 L to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 AR. This enables the pressure reducing proportional valve  33 AR to forcibly control or stop the operation of the arm cylinder  8  corresponding to the arm opening operation on an as-needed basis even during the arm opening operation of the left operating lever  26 L. Furthermore, the pressure reducing proportional valve  33 AR can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 AR to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 AR from the proportional valve  31 AR even during the arm opening operation of the left operating lever  26 L. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the arm-opening-side pilot ports of the control valves  176 L and  176 R by controlling the proportional valve  31 AR and the pressure reducing proportional valve  33 AR. 
     Thus, the pressure reducing proportional valves  33 AL and  33 AR can forcibly control or stop the operations of the arm cylinder  8  corresponding to the forward and the backward operating state of the left operating lever  26 L. Furthermore, the pressure reducing proportional valves  33 AL and  33 AR can assist in ensuring that the pilot pressures of the proportional valves  31 AL and  31 AR are applied to the pilot ports of the control valves  176 L and  176 R through the shuttle valves  32 AL and  32 AR by reducing pilot pressures applied to the one inlet ports of the shuttle valves  32 AL and  32 AR. 
     The controller  30  may forcibly control or stop the operation of the arm cylinder  8  corresponding to the arm closing operation of the left operating lever  26 L by controlling the proportional valve  31 AR instead of controlling the pressure reducing proportional valve  33 AL. For example, in the case of performing the arm closing operation with the left operating lever  26 L, the controller  30  may control the proportional valve  31 AR to act on the arm-opening-side pilot ports of the control valves  176 L and  176 R from the proportional valve  31 AR via the shuttle valve  32 AR. This applies a pilot pressure to the arm-opening-side pilot ports of the control valves  176 L and  176 R against a pilot pressure applied to the arm-closing-side pilot ports of the control valves  176 L and  176 R from the left operating lever  26 L via the shuttle valve  32 AL. Therefore, the controller  30  can forcibly move the control valves  176 L and  176 R toward a neutral position to forcibly control or stop the operation of the arm cylinder  8  corresponding to the arm closing operation of the left operating lever  26 L. Likewise, the controller  30  may forcibly control or stop the operation of the arm cylinder  8  corresponding to the arm opening operation of the left operating lever  26 L by controlling the proportional valve  31 AL instead of controlling the pressure reducing proportional valve  33 AR. 
     The operating pressure sensor  29 LA detects the details of the operator&#39;s forward or backward operation on the left operating lever  26 L in the form of pressure (operating pressure), and a detection signal corresponding to the detected pressure is fed into the controller  30 . This enables the controller  30  to determine the details of the forward or the backward operation of the left operating lever  26 L. Examples of the details of the forward and the backward operation of the left operating lever  26 L to be detected may include the direction of operation and the amount of operation (the angle of operation). Hereinafter, the same applies to the rightward and the leftward operation of the left operating lever  26 L and the forward and the backward operation and the rightward and the leftward operation of the right operating lever  26 R. 
     The controller  30  can cause hydraulic oil discharged from the pilot pump  15  to be supplied to the right pilot port of the control valve  176 L and the left pilot port of the control valve  176 R via the proportional valve  31 AL and the shuttle valve  32 AL, independent of the operator&#39;s arm closing operation on the left operating lever  26 L. Furthermore, the controller  30  can cause hydraulic oil discharged from the pilot pump  15  to be supplied to the left pilot port of the control valve  176 L and the right pilot port of the control valve  176 R via the proportional valve  31 AR and the shuttle valve  32 AR, independent of the operator&#39;s arm opening operation on the left operating lever  26 L. That is, the controller  30  can automatically control the opening and closing motion of the arm  5 . 
     Furthermore, for example, as illustrated in  FIG. 4B , the right operating lever  26 R is used in such a manner as to be tilted forward or backward to operate the boom cylinder  7  corresponding to the boom  4  by the operator. That is, when the right operating lever  26 R is tilted forward or backward, the target of operation of the right operating lever  26 R is the motion of the boom  4 . The right operating lever  26 R outputs a pilot pressure commensurate with the details of the forward or the backward operation to the secondary side, using hydraulic oil discharged from the pilot pump  15 . 
     The shuttle valve  32 BL has two inlet ports: one connected to a secondary-side pilot line of the right operating lever  26 R corresponding to an operation in a direction to raise the boom  4  (hereinafter “boom raising operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 BL, and has an outlet port connected to the right pilot port of the control valve  175 L and the left pilot port of the control valve  175 R. 
     The shuttle valve  32 BR has two inlet ports: one connected to a secondary-side pilot line of the right operating lever  26 R corresponding to an operation in a direction to lower the boom  4  (hereinafter “boom lowering operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 BR, and has an outlet port connected to the right pilot port of the control valve  175 R. 
     That is, the right operating lever  26 R applies a pilot pressure commensurate with the details of the forward or the backward operation to pilot ports of the control valves  175 L and  175 R through the shuttle valve  32 BL or  32 BR. Specifically, in response to the boom raising operation, the right operating lever  26 R outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 BL to apply the pilot pressure to the right pilot port of the control valve  175 L and the left pilot port of the control valve  175 R via the shuttle valve  32 BL. Furthermore, in response to the boom lowering operation, the right operating lever  26 R outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 BR to apply the pilot pressure to the right pilot port of the control valve  175 R via the shuttle valve  32 BR. 
     The proportional valve  31 BL operates in response to a control current input from the controller  30 . Specifically, the proportional valve  31 BL outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 BL, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 BL to control a pilot pressure applied to the right pilot port of the control valve  175 L and the left pilot port of the control valve  175 R via the shuttle valve  32 BL. 
     The proportional valve  31 BR operates in response to a control current input from the controller  30 . Specifically, the proportional valve  31 BR outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 BR, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 BR to control a pilot pressure applied to the right pilot port of the control valve  175 R via the shuttle valve  32 BR. 
     That is, the proportional valves  31 BL and  31 BR can control a pilot pressure output to the secondary side such that the control valves  175 L and  175 R can stop at a desired valve position independent of the operating state of the right operating lever  26 R. 
     The pressure reducing proportional valve  33 BL operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 BL outputs a pilot pressure commensurate with the boom raising operation of the right operating lever  26 R directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 BL reduces the pilot pressure of a secondary-side pilot line corresponding to the boom raising operation of the right operating lever  26 R to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 BL. This enables the pressure reducing proportional valve  33 BL to forcibly control or stop the operation of the boom cylinder  7  corresponding to the boom raising operation on an as-needed basis even during the boom raising operation of the right operating lever  26 R. Furthermore, the pressure reducing proportional valve  33 BL can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 BL to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 BL from the proportional valve  31 BL even during the boom raising operation of the right operating lever  26 R. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the boom-raising-side pilot ports of the control valves  175 L and  175 R by controlling the proportional valve  31 BL and the pressure reducing proportional valve  33 BL. 
     The pressure reducing proportional valve  33 BR operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 BR outputs a pilot pressure commensurate with the boom lowering operation of the right operating lever  26 R directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 BR reduces the pilot pressure of a secondary-side pilot line corresponding to the boom lowering operation of the right operating lever  26 R to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 BR. This enables the pressure reducing proportional valve  33 BR to forcibly control or stop the operation of the boom cylinder  7  corresponding to the boom lowering operation on an as-needed basis even during the boom lowering operation of the right operating lever  26 R. Furthermore, the pressure reducing proportional valve  33 BR can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 BR to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 BR from the proportional valve  31 BR even during the boom lowering operation of the right operating lever  26 R. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the boom-lowering-side pilot ports of the control valves  175 L and  175 R by controlling the proportional valve  31 BR and the pressure reducing proportional valve  33 BR. 
     Thus, the pressure reducing proportional valves  33 BL and  33 BR can forcibly control or stop the operations of the boom cylinder  7  corresponding to the forward and the backward operating state of the right operating lever  26 R. Furthermore, the pressure reducing proportional valves  33 BL and  33 BR can assist in ensuring that the pilot pressures of the proportional valves  31 BL and  31 BR are applied to the pilot ports of the control valves  175 L and  175 R through the shuttle valves  32 BL and  32 BR by reducing pilot pressures applied to the one inlet ports of the shuttle valves  32 BL and  32 BR. 
     The controller  30  may forcibly control or stop the operation of the boom cylinder  7  corresponding to the boom raising operation of the right operating lever  26 R by controlling the proportional valve  31 BR instead of controlling the pressure reducing proportional valve  33 BL. For example, in the case of performing the boom raising operation with the right operating lever  26 R, the controller  30  may control the proportional valve  31 BR to act on the boom-lowering-side pilot ports of the control valves  175 L and  175 R from the proportional valve  31 BR via the shuttle valve  32 BR. This causes a pilot pressure to be applied to the boom-lowering-side pilot ports of the control valves  175 L and  175 R against a pilot pressure applied to the boom-raising-side pilot ports of the control valves  175 L and  175 R from the right operating lever  26 R via the shuttle valve  32 BL. Therefore, the controller  30  can forcibly move the control valves  175 L and  175 R toward a neutral position to forcibly control or stop the operation of the boom cylinder  7  corresponding to the boom raising operation of the right operating lever  26 R. Likewise, the controller  30  may forcibly control or stop the operation of the boom cylinder  7  corresponding to the boom lowering operation of the right operating lever  26 R by controlling the proportional valve  31 BL instead of controlling the pressure reducing proportional valve  33 BR. 
     The operating pressure sensor  29 RA detects the details of the operator&#39;s forward or backward operation of the right operating lever  26 R in the form of pressure (operating pressure), and a detection signal corresponding to the detected pressure is fed into the controller  30 . This enables the controller  30  to determine the details of the forward or the backward operation of the right operating lever  26 R. 
     The controller  30  can cause hydraulic oil discharged from the pilot pump  15  to be supplied to the right pilot port of the control valve  175 L and the left pilot port of the control valve  175 R via the proportional valve  31 BL and the shuttle valve  32 BL, independent of the operator&#39;s boom raising operation on the right operating lever  26 R. Furthermore, the controller  30  can supply hydraulic oil discharged from the pilot pump  15  to the right pilot port of the control valve  175 R via the proportional valve  31 BR and the shuttle valve  32 BR, independent of the operator&#39;s boom lowering operation on the right operating lever  26 R. That is, the controller  30  can automatically control the rising and lowering motion of the boom  4 . 
     As illustrated in  FIG. 4C , the right operating lever  26 R is used in such a manner as to be tilted rightward or leftward to operate the bucket cylinder  9  corresponding to the bucket  6  by the operator. That is, when the right operating lever  26 R is tilted rightward or leftward, the target of operation of the right operating lever  26 R is the motion of the bucket  6 . The right operating lever  26 R outputs a pilot pressure commensurate with the details of the rightward or the leftward operation to the secondary side, using hydraulic oil discharged from the pilot pump  15 . 
     The shuttle valve  32 CL has two inlet ports: one connected to a secondary-side pilot line of the right operating lever  26 R corresponding to an operation in a direction to close the bucket  6  (hereinafter “bucket closing operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 CL, and has an outlet port connected to the left pilot port of the control valve  174 . 
     The shuttle valve  32 CR has two inlet ports: one connected to a secondary-side pilot line of the right operating lever  26 R corresponding to an operation in a direction to open the bucket  6  (hereinafter “bucket opening operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 CR, and has an outlet port connected to the right pilot port of the control valve  174 . 
     That is, the right operating lever  26 R applies a pilot pressure commensurate with the details of the rightward or the leftward operation to a pilot port of the control valve  174  through the shuttle valve  32 CL or  32 CR. Specifically, in response to the bucket closing operation, the right operating lever  26 R outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 CL to apply the pilot pressure to the left pilot port of the control valve  174  via the shuttle valve  32 CL. Furthermore, in response to the bucket opening operation, the right operating lever  26 R outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 CR to apply the pilot pressure to the right pilot port of the control valve  174  via the shuttle valve  32 CR. 
     The proportional valve  31 CL operates in response to a control current input from the controller  30 . Specifically, the proportional valve  31 CL outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 CL, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 CL to control a pilot pressure applied to the left pilot port of the control valve  174  via the shuttle valve  32 CL. 
     The proportional valve  31 CR operates in response to a control current output by the controller  30 . Specifically, the proportional valve  31 CR outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 CR, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 CR to control a pilot pressure applied to the right pilot port of the control valve  174  via the shuttle valve  32 CR. 
     That is, the proportional valves  31 CL and  31 CR can control a pilot pressure output to the secondary side such that the control valve  174  can stop at a desired valve position independent of the operating state of the right operating lever  26 R. 
     The pressure reducing proportional valve  33 CL operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 CL outputs a pilot pressure commensurate with the bucket closing operation of the right operating lever  26 R directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 CL reduces the pilot pressure of a secondary-side pilot line corresponding to the bucket closing operation of the right operating lever  26 R to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 CL. This enables the pressure reducing proportional valve  33 CL to forcibly control or stop the operation of the bucket cylinder  9  corresponding to the bucket closing operation on an as-needed basis even during the bucket closing operation of the right operating lever  26 R. Furthermore, the pressure reducing proportional valve  33 CL can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 CL to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 CL from the proportional valve  31 CL even during the bucket closing operation of the right operating lever  26 R. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the bucket-closing-side pilot port of the control valve  174  by controlling the proportional valve  31 CL and the pressure reducing proportional valve  33 CL. 
     The pressure reducing proportional valve  33 CR operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 CR outputs a pilot pressure commensurate with the bucket opening operation of the right operating lever  26 R directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 CR reduces the pilot pressure of a secondary-side pilot line corresponding to the bucket opening operation of the right operating lever  26 R to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 CR. This enables the pressure reducing proportional valve  33 CR to forcibly control or stop the operation of the bucket cylinder  9  corresponding to the bucket opening operation on an as-needed basis even during the bucket opening operation of the right operating lever  26 R. Furthermore, the pressure reducing proportional valve  33 CR can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 CR to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 CR from the proportional valve  31 CR even during the bucket opening operation of the right operating lever  26 R. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the bucket-opening-side pilot port of the control valve  174  by controlling the proportional valve  31 CR and the pressure reducing proportional valve  33 CR. 
     Thus, the pressure reducing proportional valves  33 CL and  33 CR can forcibly control or stop the operations of the bucket cylinder  9  corresponding to the rightward and the leftward operating state of the right operating lever  26 R. Furthermore, the pressure reducing proportional valves  33 CL and  33 CR can assist in ensuring that the pilot pressures of the proportional valves  31 CL and  31 CR are applied to the pilot ports of the control valve  174  through the shuttle valves  32 CL and  32 CR by reducing pilot pressures applied to the one inlet ports of the shuttle valves  32 CL and  32 CR. 
     The controller  30  may forcibly control or stop the operation of the bucket cylinder  9  corresponding to the bucket closing operation of the right operating lever  26 R by controlling the proportional valve  31 CR instead of controlling the pressure reducing proportional valve  33 CL. For example, in the case of performing the bucket closing operation with the right operating lever  26 R, the controller  30  may control the proportional valve  31 CR to act on the bucket-opening-side pilot port of the control valve  174  from the proportional valve  31 CR via the shuttle valve  32 CR. This applies a pilot pressure to the bucket-opening-side pilot port of the control valve  174  against a pilot pressure acting on the bucket-closing-side pilot port of the control valve  174  from the right operating lever  26 R via the shuttle valve  32 CL. Therefore, the controller  30  can forcibly move the control valve  174  toward a neutral position to forcibly control or stop the operation of the bucket cylinder  9  corresponding to the bucket closing operation of the right operating lever  26 R. Likewise, the controller  30  may forcibly control or stop the operation of the bucket cylinder  9  corresponding to the bucket opening operation of the right operating lever  26 R by controlling the proportional valve  31 CL instead of controlling the pressure reducing proportional valve  33 CR. 
     The operating pressure sensor  29 RB detects the details of the operator&#39;s rightward or leftward operation of the right operating lever  26 R in the form of pressure (operating pressure), and a detection signal corresponding to the detected pressure is fed into the controller  30 . This enables the controller  30  to determine the details of the rightward or the leftward operation of the right operating lever  26 R. 
     The controller  30  can cause hydraulic oil discharged from the pilot pump  15  to be supplied to the left pilot port of the control valve  174  via the proportional valve  31 CL and the shuttle valve  32 CL, independent of the operator&#39;s bucket closing operation on the right operating lever  26 R. Furthermore, the controller  30  can cause hydraulic oil discharged from the pilot pump  15  to be supplied to the right pilot port of the control valve  174  via the proportional valve  31 CR and the shuttle valve  32 CR, independent of the operator&#39;s bucket opening operation on the right operating lever  26 R. That is, the controller  30  can automatically control the opening and closing motion of the bucket  6 . 
     Furthermore, for example, as illustrated in  FIG. 4D , the left operating lever  26 L is used in such a manner as to be tilted rightward or leftward to operate the swing hydraulic motor  2 A corresponding to the upper swing structure  3  (the swing mechanism  2 ) by the operator. That is, when the left operating lever  26 L is tilted rightward or leftward, the target of operation of the left operating lever  26 L is the motion of the upper swing structure  3 . The left operating lever  26 L outputs a pilot pressure commensurate with the details of the rightward or the leftward operation to the secondary side, using hydraulic oil discharged from the pilot pump  15 . 
     The shuttle valve  32 DL has two inlet ports: one connected to a secondary-side pilot line of the left operating lever  26 L corresponding to an operation to swing the upper swing structure  3  counterclockwise (hereinafter “counterclockwise swing operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 DL, and has an outlet port connected to the left pilot port of the control valve  173 . 
     The shuttle valve  32 DR has two inlet ports: one connected to a secondary-side pilot line of the left operating lever  26 L corresponding to an operation to swing the upper swing structure  3  clockwise (hereinafter “clockwise swing operation”) and the other connected to the secondary-side pilot line of the proportional valve  31 DR, and has an outlet port connected to the right pilot port of the control valve  173 . 
     That is, the left operating lever  26 L applies a pilot pressure commensurate with the details of the clockwise or the counterclockwise swing operation to a pilot port of the control valve  173  through the shuttle valve  32 DL or  32 DR. Specifically, in response to the counterclockwise swing operation, the left operating lever  26 L outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 DL to apply the pilot pressure to the left pilot port of the control valve  173  via the shuttle valve  32 DL. Furthermore, in response to the clockwise swing operation, the left operating lever  26 L outputs a pilot pressure commensurate with the amount of operation to one inlet port of the shuttle valve  32 DR to apply the pilot pressure to the right pilot port of the control valve  173  via the shuttle valve  32 DR. 
     The proportional valve  31 DL operates in response to a control current input from the controller  30 . Specifically, the proportional valve  31 DL outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 DL, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 DL to control a pilot pressure applied to the left pilot port of the control valve  173  via the shuttle valve  32 DL. 
     The proportional valve  31 DR operates in response to a control current output by the controller  30 . Specifically, the proportional valve  31 DR outputs a pilot pressure commensurate with a control current input from the controller  30  to the other inlet port of the shuttle valve  32 DR, using hydraulic oil discharged from the pilot pump  15 . This enables the proportional valve  31 DR to control a pilot pressure applied to the right pilot port of the control valve  173  via the shuttle valve  32 DR. 
     That is, the proportional valves  31 DL and  31 DR can control a pilot pressure output to the secondary side such that the control valve  173  can stop at a desired valve position independent of the operating state of the left operating lever  26 L. 
     The pressure reducing proportional valve  33 DL operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 DL outputs a pilot pressure commensurate with the counterclockwise swing operation of the left operating lever  26 L directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 DL reduces the pilot pressure of a secondary-side pilot line corresponding to the counterclockwise swing operation of the left operating lever  26 L to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 DL. This enables the pressure reducing proportional valve  33 DL to forcibly control or stop the operation of the swing hydraulic motor  2 A corresponding to the counterclockwise swing operation on an as-needed basis even during the counterclockwise swing operation of the left operating lever  26 L. Furthermore, the pressure reducing proportional valve  33 DL can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 DL to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 DL from the proportional valve  31 DL even during the counterclockwise swing operation of the left operating lever  26 L. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the counterclockwise-swing-side pilot port of the control valve  173  by controlling the proportional valve  31 DL and the pressure reducing proportional valve  33 DL. 
     The pressure reducing proportional valve  33 DR operates in response to a control current input from the controller  30 . Specifically, when no control current is input from the controller  30 , the pressure reducing proportional valve  33 DR outputs a pilot pressure commensurate with the clockwise swing operation of the left operating lever  26 L directly to the secondary side. In contrast, when a control current is input from the controller  30 , the pressure reducing proportional valve  33 DR reduces the pilot pressure of a secondary-side pilot line corresponding to the clockwise swing operation of the left operating lever  26 L to an extent corresponding to the control current, and outputs the reduced pilot pressure to the one inlet port of the shuttle valve  32 DR. This enables the pressure reducing proportional valve  33 DR to forcibly control or stop the operation of the swing hydraulic motor  2 A corresponding to the clockwise swing operation on an as-needed basis even during the clockwise swing operation of the left operating lever  26 L. Furthermore, the pressure reducing proportional valve  33 DR can cause a pilot pressure applied to the one inlet port of the shuttle valve  32 DR to be lower than a pilot pressure applied to the other inlet port of the shuttle valve  32 DR from the proportional valve  31 DR even during the clockwise swing operation of the left operating lever  26 L. Therefore, the controller  30  can ensure that a desired pilot pressure is applied to the clockwise-swing-side pilot port of the control valve  173  by controlling the proportional valve  31 DR and the pressure reducing proportional valve  33 DR. 
     Thus, the pressure reducing proportional valves  33 DL and  33 DR can forcibly control or stop the operations of the swing hydraulic motor  2 A corresponding to the rightward and the leftward operating state of the left operating lever  26 L. Furthermore, the pressure reducing proportional valves  33 DL and  33 DR can assist in ensuring that the pilot pressures of the proportional valves  31 DL and  31 DR are applied to the pilot ports of the control valve  173  through the shuttle valves  32 DL and  32 DR by reducing pilot pressures acting on the one inlet ports of the shuttle valves  32 DL and  32 DR. 
     The controller  30  may forcibly control or stop the operation of the swing hydraulic motor  2 A corresponding to the counterclockwise swing operation of the left operating lever  26 L by controlling the proportional valve  31 DR instead of controlling the pressure reducing proportional valve  33 DL. For example, in the case of performing the counterclockwise swing operation with the left operating lever  26 L, the controller  30  may control the proportional valve  31 DR to act on the clockwise-swing-side pilot port of the control valve  173  from the proportional valve  31 DR via the shuttle valve  32 DR. This applies a pilot pressure to the clockwise-swing-side pilot port of the control valve  173  against a pilot pressure applied to the counterclockwise-swing-side pilot port of the control valve  173  from the left operating lever  26 L via the shuttle valve  32 DL. Therefore, the controller  30  can forcibly move the control valve  173  toward a neutral position to forcibly control or stop the operation of the swing hydraulic motor  2 A corresponding to the counterclockwise swing operation of the left operating lever  26 L. Likewise, the controller  30  may forcibly control or stop the operation of the swing hydraulic motor  2 A corresponding to the clockwise swing operation of the left operating lever  26 L by controlling the proportional valve  31 DL instead of controlling the pressure reducing proportional valve  33 DR. 
     The operating pressure sensor  29 LB detects the state of the operator&#39;s operation on the left operating lever  26 L in the form of pressure, and a detection signal corresponding to the detected pressure is fed into the controller  30 . This enables the controller  30  to determine the details of the rightward or the leftward operation of the left operating lever  26 L. 
     The controller  30  can cause hydraulic oil discharged from the pilot pump  15  to be supplied to the left pilot port of the control valve  173  via the proportional valve  31 DL and the shuttle valve  32 DL, independent of the operator&#39;s counterclockwise swing operation on the left operating lever  26 L. Furthermore, the controller  30  can cause hydraulic oil discharged from the pilot pump  15  to be supplied to the right pilot port of the control valve  173  via the proportional valve  31 DR and the shuttle valve  32 DR, independent of the operator&#39;s clockwise swing operation on the left operating lever  26 L. That is, the controller  30  can automatically control the clockwise and counterclockwise motion of the upper swing structure  3 . 
     A configuration that enables the controller  30  to perform automatic control may also be adopted for the lower traveling structure  1 , the same as for the boom  4 , the arm  5 , the bucket  6 , and the upper swing structure  3 . In this case, the shuttle valve  32  may be installed in the pilot line between the left travel lever  26 DL and the control valve  171  and in the pilot line between the right travel lever  26 DR and the control valve  172 , and the proportional valve  31  may be installed at the other inlet port of the shuttle valve  32  via a pilot line. According to this, the controller  30  can automatically control the traveling motion of the lower traveling structure  1  (the left crawler  1 CL and the right crawler  1 CR) by outputting a control current to the proportional valve  31 . 
     Next, the control system of the shovel  100  according to this embodiment includes the controller  30 , a space recognition device  70 , an orientation detector  71 , an input device  72 , a positioning device  73 , a display device D 1 , a sound output device D 2 , a boom angle sensor S 1 , an arm angle sensor S 2 , a bucket angle sensor S 3 , a machine body tilt sensor S 4 , and a swing state sensor S 5 . 
     The space recognition device  70  recognizes an object present in a three-dimensional space surrounding the shovel  100  and obtains information for measuring (calculating) a positional relationship such as the distance from the space recognition device  70  or the shovel  100  to the recognized object. Furthermore, the space recognition device  70  may recognize an object in an area surrounding the shovel  100  and measure the positional relationship between the recognized object and the space recognition device  70  or the shovel  100  based on the obtained information. Examples of the space recognition device  70  may include an ultrasonic sensor, a millimeter wave radar, a monocular camera, a stereo camera, a LIDAR (Light Detecting and Ranging), a distance image sensor, and an infrared sensor. According to this embodiment, the space recognition device  70  includes a forward recognition sensor  70 F attached to the front end of the upper surface of the cabin  10 , a backward recognition sensor  70 B attached to the back end of the upper surface of the upper swing structure  3 , a leftward recognition sensor  70 L attached to the left end of the upper surface of the upper swing structure  3 , and a rightward recognition sensor  70 R attached to the right end of the upper surface of the upper swing structure  3 . Furthermore, an upward recognition sensor that recognizes an object present in a space above the upper swing structure  3  may be attached to the shovel  100 . 
     The orientation detector  71  detects information on the relative relationship between the orientation of the upper swing structure  3  and the orientation of the lower traveling structure  1  (for example, the swing angle of the upper swing structure  3  relative to the lower traveling structure  1 ). 
     The orientation detector  71  may include, for example, a combination of a geomagnetic sensor attached to the lower traveling structure  1  and a geomagnetic sensor attached to the upper swing structure  3 . Furthermore, the orientation detector  71  may also include a combination of a GNSS receiver attached to the lower traveling structure  1  and a GNSS receiver attached to the upper swing structure  3 . The orientation detector  71  may also include a rotary encoder, a rotary position sensor, etc., that can detect the swing angle of the upper swing structure  3  relative to the lower traveling structure  1 , namely, the above-mentioned swing state sensor S 5 , and may be attached to, for example, a center joint provided in relation to the swing mechanism  2  that achieves relative rotation between the lower traveling structure  1  and the upper swing structure  3 . The orientation detector  71  may also include a camera attached to the upper swing structure  3 . In this case, the orientation detector  71  performs known image processing on an image captured by the camera attached to the upper swing structure  3  (an input image) to detect an image of the lower traveling structure  1  included in the input image. The orientation detector  71  may identify the longitudinal direction of the lower traveling structure  1  by detecting an image of the lower traveling structure  1  using a known image recognition technique and derive the angle formed between the direction of the longitudinal axis of the upper swing structure  3  and the longitudinal direction of the lower traveling structure  1 . At this point, the direction of the longitudinal axis of the upper swing structure  3  may be derived from the attachment position of the camera. In particular, the crawlers  1 C protrude from the upper swing structure  3 . Therefore, the orientation detector  71  can identify the longitudinal direction of the lower traveling structure  1  by detecting an image of the crawlers  1 C. 
     In the case where the upper swing structure  3  is configured to be driven to swing by an electric motor instead of the swing hydraulic motor  2 A, the orientation detector  71  may be a resolver. 
     The input device  72  is provided within the reach of the operator seated in the cabin  10 , and receives the operator&#39;s various operation inputs to output signals corresponding to the operation inputs to the controller  30 . For example, the input device  72  includes a touchscreen provided on the display of a display device that displays various information images. Furthermore, for example, the input device  72  may include a button switch, a lever, a toggle, etc., provided around the display device D 1 . Furthermore, the input device  72  may include a knob switch provided on the operating device  26  (for example, a switch NS provided on the left operating lever  26 L). A signal corresponding to the details of an operation on the input device  72  is fed into the controller  30 . 
     The switch NS is a push button switch provided at the top of the left operating lever  26 L, for example. The operator can operate the left operating lever  26 L while pressing the switch NS. The switch NS may also be provided on the right operating lever  26 R or at a different position in the cabin  10 . 
     The positioning device  73  measures the position and the orientation of the upper swing structure  3 . The positioning device  73  is, for example, a GNSS (Global Navigation Satellite System) compass, and detects the position and the orientation of the upper swing structure  3 . A detection signal corresponding to the position and the orientation of the upper swing structure  3  is fed into the controller  30 . Furthermore, among the functions of the positioning device  73 , the function of detecting the orientation of the upper swing structure  3  may be replaced with a direction sensor attached to the upper swing structure  3 . 
     The display device D 1  is provided at such a position as to be easily visible by the operator seated in the cabin  10 , and displays various information images under the control of the controller  30 . The display device D 1  may be connected to the controller  30  via an in-vehicle communications network such as a CAN (Controller Area Network) or may be connected to the controller  30  via a one-to-one dedicated line. 
     The sound output device D 2  is, for example, provided in the cabin  10  and connected to the controller  30  to output a sound under the control of the controller  30 . The sound output device D 2  is, for example, a loudspeaker or a buzzer. The sound output device D 2  outputs various kinds of sound information in response to sound output commands from the controller  30 . 
     The boom angle sensor S 1  is attached to the boom  4  to detect the elevation angle of the boom  4  relative to the upper swing structure  3  (hereinafter, “boom angle”), for example, the angle of a straight line connecting the pivot points of the boom  4  at its both ends to the swing plane of the upper swing structure  3  in a side view. Examples of the boom angle sensor S 1  may include a rotary encoder, an acceleration sensor, a six-axis sensor, and an IMU (Inertial Measurement Unit), which is hereinafter also the case with the arm angle sensor S 2 , the bucket angle sensor S 3 , and the machine body tilt sensor S 4 . A detection signal corresponding to the boom angle detected by the boom angle sensor S 1  is fed into the controller  30 . 
     The arm angle sensor S 2  is attached to the arm  5  to detect the pivot angle of the arm  5  relative to the boom  4  (hereinafter “arm angle”), for example, the angle of a straight line connecting the pivot points of the arm  5  at its both ends to the straight line connecting the pivot points of the boom  4  at its both ends in a side view. A detection signal corresponding to the arm angle detected by the arm angle sensor S 2  is fed into the controller  30 . 
     The bucket angle sensor S 3  is attached to the bucket  6  to detect the pivot angle of the bucket  6  relative to the arm  5  (hereinafter “bucket angle”), for example, the angle of a straight line connecting the pivot point and the leading edge (blade edge) of the bucket  6  to the straight line connecting the pivot points of the arm  5  at its both ends in a side view. A detection signal corresponding to the bucket angle detected by the bucket angle sensor S 3  is fed into the controller  30 . 
     The machine body tilt sensor S 4  detects the tilt state of the machine body (for example, the upper swing structure  3 ) relative to a horizontal plane. The machine body tilt sensor S 4  is, for example, attached to the upper swing structure  3  to detect the tilt angles of the shovel  100  (namely, the upper swing structure  3 ) about two axes in its longitudinal direction and lateral direction (hereinafter “longitudinal tilt angle” and “lateral tilt angle”). Examples of the machine body tilt sensor S 4  may include an acceleration sensor, a gyroscope (angular velocity sensor), a six-axis sensor, and an IMU. Detection signals corresponding to the tilt angles (longitudinal tilt angle and lateral tilt angle) detected by the machine body tilt sensor S 4  are fed into the controller  30 . 
     The swing state sensor S 5  is attached to the upper swing structure  3  to output detection information regarding the swing state of the upper swing structure  3 . The swing state sensor S 5  detects, for example, the swing angular velocity and the swing angle of the upper swing structure  3 . Examples of the swing state sensor S 5  include a gyroscope, a resolver, and a rotary encoder. 
     When the machine body tilt sensor S 4  includes a gyroscope, a six-axis sensor, an IMU or the like that can detect angular velocities about three axes, the swing state (for example, the swing angular velocity) of the upper swing structure  3  may be detected based on a detection signal of the machine body tilt sensor S 4 . In this case, the swing state sensor S 5  may be omitted. 
     The controller  30 , for example, may perform control related to the hydraulic system of the shovel  100  as described above. 
     Furthermore, the controller  30 , for example, may perform control related to the automatic operation function including the machine guidance function and the machine control function. 
     Furthermore, the controller  30 , for example, may perform control related to the surroundings monitoring function of the shovel  100  based on the output of the space recognition device  70 . 
     For example, the controller  30  monitors the presence or absence of a monitoring object entering an area surrounding the shovel  100  monitored by the space recognition device  70 . Specifically, the controller  30  may detect a monitoring object within a predetermined area relative to the shovel  100  (hereinafter, “monitoring area”) based on the output of the space recognition device  70 . Furthermore, the controller  30  may identify (determine) the type and the position of a monitoring object based on the output of the space recognition device  70 , using a known technique such as machine learning. Furthermore, in response to detecting a monitoring object within the monitoring area, the controller  30  may notify the operator and an area surrounding the shovel  100  of the detection of the monitoring target within the monitoring area in a predetermined manner. Furthermore, the controller  30  may notify the operator and the area surrounding the shovel  100  only when the detected monitoring object is determined to be a “person.” For example, the operator in the cabin  10  may be notified visually or aurally through the display device D 1  or the sound output device D 2  (for example, a buzzer or a loudspeaker) in the cabin  10 . Furthermore, for example, the area surrounding the shovel  100  may be notified visually or aurally through a sound output device (for example, a buzzer or an alarm) mounted on the upper swing structure  3  or a lighting device (for example, a headlight or a red lamp). Furthermore, for example, a remote control operator may be notified visually or aurally through a sound output device or a display device installed in an external apparatus that assists remote control by transmitting a notification request signal to the external apparatus. Furthermore, in response to detecting a monitoring object within the monitoring area, the controller  30  may restrict the operation of an actuator (driven part) of the shovel  100  in a predetermined manner. Furthermore, the controller  30  may restrict the operation of an actuator (driven part) of the shovel  100  only when the detected monitoring object is determined to be a “person.” The restriction of the operation of an actuator includes a control mode that slows the operating speed of an actuator relative to an operation. Furthermore, the restriction of the operation of an actuator includes a control mode that maintains the stationary state of an actuator irrespective of the presence or absence of an operation. For example, the restriction of the operation (the maintenance of the stationary state) of an actuator may be achieved by closing a gate lock valve. Furthermore, when the operating device  26  is an electric type, the controller  30  may achieve the restriction of the operation (the maintenance of the stationary state) of an actuator by disabling an operation signal and outputting no signal to the hydraulic pressure control valve for operation even when the operation signal is input. 
     Specifically, in response to determining that a person is present within the monitoring area around the shovel  100  before the operator operates the operating device  26 , the controller  30  may disable the actuator or cause the actuator to operate very slowly even when the operator operates an operating lever. More specifically, in the case of the operating device  26  of a hydraulic pilot type, in response to determining that a person is present within the monitoring area around the shovel  100 , the controller  30  can disable the actuator by putting the gate lock valve in a locking state. In the case of the operating device  26  of an electric type, the controller  30  can disable the actuator by disabling a signal from the controller  30  to a control valve for operation. When it is desired to cause the actuator to operate very slowly, the controller  30  can cause the actuator to operate very slowly by restricting a control signal from the controller  30  to the control valve for operation such that the control signal corresponds to a relatively low pilot pressure. Furthermore, the same applies to the case where the operating device  26  of another type is employed if it is possible to indirectly control a pilot pressure to be applied to a control valve in the control valve  17  using a control valve for operation. 
     Thus, when it is determined that a monitoring object is present within the monitoring area around the shovel  100 , an actuator is prevented from being driven or is driven at a lower operating speed (slower speed) than an operating speed corresponding to an operation input to the operating device  26  even when the operating device  26  is operated. Furthermore, when it is determined that a person is present within the monitoring area around the shovel  100  during the operator&#39;s operation of the operating device  26 , the operation of an actuator may be stopped or decelerated regardless of the operator&#39;s operation. Specifically, in the case of the operating device  26  of a hydraulic pilot type, in response to determining that a person is present within the monitoring area around the shovel  100 , the controller  30  stops an actuator by putting the gate lock valve in a locking state. Furthermore, in the case of using a control valve for operation that outputs a pilot pressure corresponding to a control command from the controller  30  to apply the pilot pressure to a pilot port of a corresponding control valve in the control valve  17 , the controller  30  can disable an actuator or decelerate its operation by disabling a signal to the control valve for operation or outputting a deceleration command to the control valve for operation. 
     Furthermore, the same may be true for the case where the shovel  100  is remotely controlled or operated with a complete automatic operation function. That is, when it is determined that a monitoring object is present within the monitoring area around the shovel  100 , an actuator may be prevented from being driven or may be driven at a lower operating speed (slower speed) than an operating speed corresponding to an input even when a remote control signal or a control command from the automatic operation function is input. 
     Furthermore, for example, when the detected monitoring object is a truck, a control as to the stopping or deceleration of an actuator may be prevented from being executed. In this case, the controller  30  may control an actuator to avoid the detected truck. 
     Thus, the type of a detected monitoring object may be recognized and an actuator may be controlled based on the result of the recognition. 
     [Overview of Machine Guidance Function and Machine Control Function of Shovel] 
     Next, an overview of the machine guidance function and the machine control function of the shovel  100  is given with reference to  FIG. 6 . 
       FIG. 6  is a block diagram illustrating an overview of an example of a configuration related to the machine guidance function and the machine control function of the shovel  100 . 
     The controller  30 , for example, executes a control related to the machine guidance function of the shovel  100  that guides the operator in manually operating the shovel  100 . 
     The controller  30  imparts, for example, work information such as the distance between an intended construction plane and the distal end of the attachment AT, specifically, the working part of the end attachment, to the operator through the display device D 1 , the sound output device D 2 , etc. Specifically, the controller  30  obtains information from the boom angle sensor S 1 , the arm angle sensor S 2 , the bucket angle sensor S 3 , the machine body tilt sensor S 4 , the swing state sensor S 5 , the space recognition device  70 , the positioning device  73 , the input device  72 , etc. The controller  30  may, for example, calculate the distance between the bucket  6  and the intended construction plane based on the obtained information and impart the calculated distance to the operator through an image displayed on the display device D 1  and a sound output from the sound output device D 2 . Data on the intended construction plane are stored in an internal memory, an external storage connected to the controller  30 , or the like, based on settings input through the input device  72  by the operator or by being downloaded from the outside (for example, a predetermined management server). The data on the intended construction plane are expressed in a reference coordinate system. The reference coordinate system is, for example, the world geodetic system. The world geodetic system is a three-dimensional Cartesian coordinate system with the origin at the center of mass of the Earth, the X-axis oriented toward the point of intersection of the prime meridian and the equator, the Y-axis oriented toward 90 degrees east longitude, and the Z-axis oriented toward the Arctic pole. For example, the operator may set any point at a construction site as a reference point and set the intended construction plane based on the relative positional relationship with the reference point through the input device  72 . The working part of the bucket  6  is, for example, the teeth tips  6 _ 5  (see  FIG. 1 ) of the bucket  6 , the back surface  6 _ 3  of the bucket  6 , or the like. Furthermore, for example, when a breaker is employed instead of the bucket  6  as the end attachment, the tip of the breaker corresponds to the working part. This enables the controller  30  to impart work information to the operator through the display device D 1 , the sound output device D 2 , etc., to guide the operator in operating the shovel  100  through the operating device  26 . 
     When the shovel  100  is remotely controlled, the work information may be transmitted to an external apparatus that is the transmitter of a remote control signal and be imparted to an operator through a display device and a sound output device installed in the external apparatus. This enables the controller  30  to impart the work information to the operator of the external apparatus to guide the operator in remotely controlling the shovel  100 . 
     Furthermore, the controller  30 , for example, executes a control related to the machine control function of the shovel  100  that assists the operator in manually operating the shovel  100 . For example, the machine control function is enabled in response to the left operating lever  26 L and the right operating lever  26 R being operated with the switch NS being pressed. Furthermore, in the case of remotely controlling the shovel  100  as well, the machine control function may be enabled in response to an operating device for remote control (hereinafter “remote controller”) used by the operator being operated with a similar knob switch provided on the remote controller being pressed. 
     The controller  30  is configured to obtain a target for a trajectory (hereinafter “target trajectory”) followed by a predetermined part of the attachment that serves as a reference for control (hereinafter simply “control reference”). When there is a target of work that can be contacted by the end attachment (for example, the ground or earth on the bed of a dump truck as described below) as in excavation work, compaction work, etc., the working part of the end attachment (for example, the teeth tips  6 _ 5  or the back surface  6 _ 3  of the bucket  6 , the right or left end of the teeth tips  6 _ 5  of the bucket  6 , the right or left end of the lower end of the back surface  6 _ 3  of the bottom plate, any point on the curved surface  6 _ 2  of the bottom plate, or the like) may be set as the control reference. Furthermore, in the case of a motion without a target of work that can be contacted by the end attachment, such as a boom raising and swing motion, a dumping motion, or a boom lowering and swing motion as described below, any part that can define the position of the end attachment in the motion (for example, the lower end or the teeth tips  6 _ 5  of the bucket  6 ) may be set as the control reference. Furthermore, multiple points in the external shape of the bucket  6  corresponding to the working part may be set as the control reference. For example, the controller  30  derives the target trajectory based on data related to the intended construction plane stored in an internal nonvolatile storage or an external nonvolatile storage with which the controller  30  can communicate. The controller  30  may derive the target trajectory based on information on the terrain of an area surrounding the shovel  100  recognized by the space recognition device  70 . Furthermore, the controller  30  may derive information on the past trajectory of the working part such as the teeth tips  6 _ 5  of the bucket  6  from the past output of a pose detector (for example, the boom angle sensor S 1 , the arm angle sensor S 2 , the bucket angle sensor S 3 , etc.) temporarily stored in an internal volatile storage and derive the target trajectory based on the information. Furthermore, the controller  30  may derive the target trajectory based on the current position of a predetermined part of the attachment and the data on the intended construction plane. 
     For example, when the operator is manually performing an operation to excavate or level the ground, the controller  30  automatically moves at least one of the boom  4 , the arm  5 , and the bucket  6  such that the working part of the bucket  6  (for example, the teeth tips  6 _ 5  or the back surface  6 _ 3  of the bucket  6 ) coincides with the intended construction plane. Specifically, when the operator operates the left operating lever  26 L in a forward or a backward direction while operating (pressing) the switch NS, the controller  30  automatically moves at least one of the boom  4 , the arm  5 , and the bucket  6  in accordance with the operation such that the working part of the bucket  6  coincides with the intended construction plane. More specifically, the controller  30  controls the proportional valve  31  as described above to automatically move at least one of the boom  4 , the arm  5 , and the bucket  6 . The same applies to the case of remote control. This enables the operator to cause the shovel  100  to perform excavating work, leveling work, etc., along the intended construction plane by merely performing an operation to open or close the arm  5  (for example, by merely operating the left operating lever  26 L in a forward or a backward direction). 
     [Details of Machine Control Function of Shovel] 
     Next, the machine control function of the shovel  100  according to this embodiment is described in detail with reference to  FIGS. 7A and 7B ,  FIGS. 8A and 8B , and  FIG. 9 . 
     &lt;Specific Example of Motion Based on Machine Control Function of Shovel&gt; 
       FIGS. 7A and 7B  are diagrams illustrating examples of motions based on the machine control function of the shovel  100 , showing a situation where the shovel  100  is performing leveling work (ground leveling work), moving the back surface  6 _ 3  of the bucket  6  along an intended construction plane  600  with the machine control function. 
     In  FIGS. 7A and 7B , of the attachment AT of the shovel  100 , only the bucket  6  is depicted, and a depiction of the boom  4  and the arm  5  is omitted. Furthermore, in  FIGS. 7A and 7B , in order to depict changes over time with the movement of the bucket  6 , the bucket  6  is conveniently indicated by  6 A,  6 B,  6 C,  6 D,  6 E,  6 F,  6 G and  6 H at predetermined times. 
     As illustrated in  FIGS. 7A and 7B , the intended construction plane  600  includes a horizontal plane  601  (a first intended construction plane), a slope  602  (a second intended construction plane) which is a downslope relative to the horizontal plane  601 , and a bend  603  at which the horizontal plane  601  and the slope  602  intersect (a boundary portion of the intended construction plane). 
     Furthermore, a space above the intended construction plane  600  is divided into regions  610 ,  620  and  630  in accordance with the shape of the intended construction plane  600 . Specifically, the region  610  is part of a spatial region above the horizontal plane  601  which part is on the horizontal plane  601  side (the left side in the drawing) of an extended plane  615  of the slope  602 . The region  620  is part of a spatial region delimited by the extended plane  615  of the slope  602  and an extended plane  625  of the horizontal plane  601  above the bend  603 . The region  630  is part of a spatial region above the slope  602  which part is on the slope  602  side (the lower side in the drawing) of the extended plane  625  of the horizontal plane  601 . The regions  610  through  630  are preset based on the shape of the intended construction plane  600  in the shovel  100 . 
     The method of setting (the method of delimiting) the regions  610  through  630  in  FIGS. 7A and 7B  is an example, and any setting method (delimiting method) may be adopted. The same applies to regions  810  through  830  of  FIG. 9  described below. 
     The shovel  100  automatically moves the boom  4  and the bucket  6  according to the operator&#39;s operation of the arm  5  (hereinafter “arm operation”) to move the bucket  6  such that the back surface  6 _ 3  of the bucket  6  is aligned with the intended construction plane. 
     As illustrated in  FIG. 7A , according to this example, with the machine body (the lower traveling structure  1  and the upper swing structure  3 ) being positioned on the horizontal plane  601  side, the shovel  100  moves the bucket  6 , pushing the bucket  6  away from the machine body. Aligning the back surface  6 _ 3  of the bucket  6  with the intended construction plane  600 , the shovel  100  performs ground leveling work from the horizontal plane  601  (the state of a bucket  6 A) to the bend  603  (the states of buckets  6 B and  6 C) and to the slope  602  (the state of a bucket  6 D). 
     When the bucket  6  is positioned in the region  610  (the state of the bucket  6 A), the controller  30  controls the bucket angle such that the back surface  6 _ 3  of the bucket  6  parallels the horizontal plane  601  or maintains a predetermined angular range relative to parallelism to the horizontal plane  601 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  610  when at least part of the bucket  6  is included in the region  610 . Furthermore, the controller  30  controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the horizontal plane  601 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the horizontal plane  601 . This enables the shovel  100  to move the bucket  6  along the horizontal plane  601 . 
     When the position of the bucket  6  changes from being in the region  610  to being in the region  620  (the state of the bucket  6 B), the controller  30  controls the bucket angle to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  601  to being parallel to the slope  602 . For example, the controller  30  may determine that the position of the bucket  6  is in the region  620  when the entirety of the bucket  6  is included in the region  620  and when the bucket  6  keeps on changing its pose as the bucket  6  enters the region  620 . When at least a part of the bucket  6  that is the control reference is positioned in the region  620 , the controller  30  may determine that the bucket  6  is positioned in the region  620 . Furthermore, the controller  30  controls the boom angle based on the arm angle determined by the details of the arm operation and the bucket angle sequentially determined during the transition of the state of the bucket surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  601  to being parallel to the slope  602 . For example, the controller  30  may control the boom angle such that the teeth tips  6 _ 5  of the bucket  6  contact (coincide with) or are slightly spaced from the slope  602  or the extended plane  615  of the slope  602 . This enables the shovel  100  to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  601  (the state of the bucket  6 B) to being parallel to the slope  602  (the state of the bucket  6 C) while avoiding a situation where the bucket  6  bites the bend  603  or is out of alignment with the shape of the bend  603 . Therefore, the shovel  100  can appropriately shape the intended construction plane  600  in the vicinity of the bend  603  with the back surface  6 _ 3  of the bucket  6 . 
     When the bucket  6  is positioned in the region  630  (the states of the buckets  6 C and  6 D), the controller  30  controls the bucket angle to keep the back surface  6 _ 3  of the bucket  6  parallel to the slope  602 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  630  when the changing of the pose of the bucket  6 , which starts in response to the entry of the bucket  6  into the region  620 , is completed and at least part of the bucket  6  is included in the region  630 . The controller  30  may also determine that the bucket  6  is positioned in the region  630  when at least a part of the bucket  6  that is the control reference is positioned in the region  630 . Furthermore, the controller  30  controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the slope  602 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the slope  602 . This enables the shovel  100  to move the bucket  6  along the slope  602 . 
     According to this example, first, the controller  30  controls the back surface  6 _ 3  of the bucket  6  serving as the control reference (working part) such that the back surface  6 _ 3  is aligned with the horizontal plane  601  as the target trajectory. In this case, the correspondence between the control reference and the target trajectory is set on the back surface  6 _ 3  of the bucket  6  and the horizontal plane  601 . At this point, the controller  30  determines the presence or absence of the bend  603  in the set intended construction plane  600 , and in response to determining the presence of the bend  603 , executes control that accommodates a change in the intended construction plane  600  at the bend  603 . 
     According to this example, as illustrated in  FIG. 7A , the change between the adjoining intended construction planes  600  (the horizontal plane  601  and the slope  602 ) at the bend  603  in the traveling direction of the control reference (working part) is more than 180°. In this case, the controller  30  determines whether the curve surface  6 _ 2  of the bottom plate, which is the leading end of the bucket  6  in the traveling direction, has passed the extended plane  615  of the next intended construction plane (the slope  602 ). In response to determining that the curve surface  6 _ 2  of the bucket  6  has passed the extended plane  615 , the controller  30  further determines whether the teeth tips  6 _ 5 , which are the trailing end of the bucket  6  in the traveling direction, have passed the extended plane  615 . In response to determining that the teeth tips  6 _ 5  of the bucket  6  have passed the extended plane  615 , the controller  30  changes the correspondence between the control reference and the target trajectory to the back surface  6 _ 3  of the bucket  6  and the slope  602 . Then, the controller  30  controls the bucket angle to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  601  to being parallel to the slope  602 . At this point, the bucket angle is controlled such that the back surface  6 _ 3  of the bucket  6  parallels the slope  602  or is within a predetermined angular range relative to parallelism to the slope  602 . 
     Thereafter, the controller  30  controls the back surface  6 _ 3  of the bucket  6  serving as the control reference (working part) to be aligned with the slope  602  as the target trajectory. 
     Furthermore, as illustrated in  FIG. 7B , according to this example, contrary to the case of  FIG. 7A , with the machine body being positioned on the horizontal plane  601  side, the shovel  100  moves the bucket  6 , drawing the bucket  6  toward the machine body. Aligning the back surface  6 _ 3  of the bucket  6  with the intended construction plane  600 , the shovel  100  performs ground leveling work from the slope  602  (the state of a bucket  6 E) to the bend  603  (the states of buckets  6 F and  6 G) and to the horizontal plane  601  (the state of a bucket  6 H). 
     When the bucket  6  is positioned in the region  630  (the state of the bucket  6 E), the controller  30 , the same as in the case of  FIG. 7A , controls the bucket angle to keep the back surface  6 _ 3  of the bucket  6  parallel to the slope  602 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  630  when at least part of the bucket  6  is included in the region  630 . Furthermore, the controller  30 , the same as in the case of  FIG. 7A , controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the slope  602 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the slope  602 . This enables the shovel  100  to move the bucket  6  along the slope  602 . 
     When the position of the bucket  6  changes from being in the region  630  to being in the region  620  (the state of the bucket  6 F), the controller  30  controls the bucket angle to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the slope  602  to being parallel to the horizontal plane  601 . Furthermore, the controller  30  controls the boom angle based on the arm angle determined by the details of the arm operation and the bucket angle sequentially determined during the transition of the state of the bucket surface  6 _ 3  of the bucket  6  from being parallel to the slope  602  to being parallel to the horizontal plane  601 . For example, the controller  30  may control the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) or is slightly spaced from the horizontal plane  601  or the extended plane  625  of the horizontal plane  601 . This enables the shovel  100  to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the slope  602  (the state of the bucket  6 F) to being parallel to the horizontal plane  601  (the state of the bucket  6 G) while avoiding a situation where the bucket  6  bites the bend  603  or is out of alignment with the shape of the bend  603 . Therefore, the shovel  100  can appropriately shape the intended construction plane  600  in the vicinity of the bend  603  with the back surface  6 _ 3  of the bucket  6 . 
     When the bucket  6  is positioned in the region  610  (the states of the buckets  6 G and  6 H), the controller  30  controls the bucket angle to keep the back surface  6 _ 3  of the bucket  6  parallel to the horizontal plane  601 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  610  when the changing of the pose of the bucket  6 , which starts in response to the entry of the bucket  6  into the region  620 , is completed and at least part of the bucket  6  is included in the region  610 . Furthermore, the controller  30  controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the horizontal plane  601 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the horizontal plane  601 . This enables the shovel  100  to move the bucket  6  along the horizontal plane  601 . 
     According to this example, first, the controller  30  controls the back surface  6 _ 3  of the bucket  6  serving as the control reference (working part) such that the back surface  6 _ 3  is aligned with the slope  602  as the target trajectory. In this case, the correspondence between the control reference and the target trajectory is set on the back surface  6 _ 3  of the bucket  6  and the slope  602 . At this point, the controller  30  determines the presence or absence of the bend  603  in the set intended construction plane  600 , and in response to determining the presence of the bend  603 , executes control that accommodates a change in the intended construction plane  600  at the bend  603 . 
     According to this example, as illustrated in  FIG. 7B , the change between the adjoining intended construction planes  600  (the horizontal plane  601  and the slope  602 ) at the bend  603  in the traveling direction of the control reference (working part) is more than 180°. In this case, the controller  30  determines whether the teeth tips  6 _ 5 , which are the leading end of the bucket  6  in the traveling direction, has passed the extended plane  625  of the next intended construction plane (the horizontal plane  601 ). In response to determining that the teeth tips  6 _ 5  of the bucket  6  have passed the extended plane  625 , the controller  30  further determines whether the curved surface  6 _ 2 , which is the trailing end of the bucket  6  in the traveling direction, has passed the extended plane  625 . In response to determining that the curved surface  6 _ 2  of the bucket  6  has passed the extended plane  625 , the controller  30  changes the correspondence between the control reference and the target trajectory to the back surface  6 _ 3  of the bucket  6  and the horizontal plane  601 . Then, the controller  30  controls the bucket angle to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the slope  602  to being parallel to the horizontal plane  601 . At this point, the bucket angle is controlled such that the back surface  6 _ 3  of the bucket  6  parallels the horizontal plane  601  or is within a predetermined angular range relative to parallelism to the horizontal plane  601 . 
     Thereafter, the controller  30  controls the back surface  6 _ 3  of the bucket  6  serving as the control reference (working part) to be aligned with the horizontal plane  601  as the target trajectory. 
     Thus, according to this example ( FIGS. 7A and 7B ), multiple regions (the regions  610  through  630 ) between which a control command for the motion of the bucket  6  (a bucket command value β 3r  as described below) generated by the controller  30  differs are set in the vicinity of the bend  603  of the intended construction plane  600 . Specifically, when the bucket  6  is positioned in the region  610  or the region  630 , the controller  30  generates a control command for the motion of the bucket  6  to keep the bucket angle parallel to the horizontal plane  601  or the slope  602 . In contrast, when the position of the bucket  6  enters the region  620  from the region  610  or the region  630 , the controller  30  generates a control command for the motion of the bucket  6  to change the bucket angle from being parallel to the horizontal plane  601  to being parallel to the slope  602  or from being parallel to the slope  602  to being parallel to the horizontal plane  601 . More specifically, in a situation where the change between the adjoining intended construction planes  600  at the bend  603  in the traveling direction of the control reference (working part) is more than 180°, the controller  30  changes the correspondence between the control reference and the target trajectory when the trailing end of the bucket  6  in the traveling direction passes the extended plane of the next intended construction plane to enter. This enables the shovel  100  to avoid a situation where the bucket  6  bites the ground near the bend  603  or is out of alignment with the shape of the bend  603  to appropriately move the working part of the bucket  6  along the intended construction plane  600  in the vicinity of the bend  603  of the intended construction plane  600 . 
     &lt;Details of Configuration Related to Machine Control Function of Shovel&gt; 
       FIGS. 8A and 8B  are functional block diagrams illustrating the details of an example of a configuration related to the machine control function of the shovel  100  according to this embodiment. Specifically,  FIGS. 8A and 8B  are a specific example of a configuration related to the machine control function for automatically moving the attachment AT of the shovel  100  in response to the operator&#39;s arm operation, namely, the forward and the backward operation of the left operating lever  26 L. 
     A configuration related to the machine control function for automatically moving the attachment AT of the shovel  100  in response to arm remote control is the same as illustrated in  FIGS. 8A and 8B  except that the operating pressure sensor  29 LA of  FIG. 8A  is replaced with a communications device that receives a remote control signal from an external apparatus. Accordingly, a description thereof is omitted. 
     The controller  30  includes an operation details obtaining part  3001 , a current position calculating part  3002 , an intended construction plane obtaining part  3003 , a region determining part  3004 , a target trajectory setting part  3005 , a target position calculating part  3006 , a bucket shape obtaining part  3007 , a movement command generating part  3008 , a pilot command generating part  3009 , and a pose angle calculating part  3010  as functional parts related to the machine control function. For example, when the switch NS is pressed, these functional parts  3001  through  3010  repeatedly execute a below-described operation at predetermined control intervals. 
     The operation details obtaining part  3001  obtains operation details with respect to forward and backward tilting operations on the left operating lever  26 L based on a detection signal fed from the operating pressure sensor  29 LA. For example, the operation details obtaining part  3001  obtains (calculates) the direction of operation (whether it is a forward direction or a backward direction) and the amount of operation as operation details. 
     The current position calculating part  3002  calculates the position (current position) of the working part of the bucket  6  (for example, the teeth tips  6 _ 5  or back surface  6 _ 3  of the bucket  6 ). Specifically, the current position calculating part  3002  may calculate the current position of the control reference of the attachment AT based on a boom angle θ 1 , an arm angle θ 2 , and a bucket angle θ 3  calculated by the below-described pose angle calculating part  3010 . 
     The intended construction plane obtaining part  3003  obtains data on an intended construction plane from the internal memory (nonvolatile secondary storage) of the controller  30 , a predetermined external storage, or the like, for example. 
     The region determining part  3004  determines a region in which the bucket  6  is positioned among regions preset in a space above the intended construction plane. When the intended construction plane includes a bend at which the inclination of a tangent plane discontinuously changes in the direction of the upper swing structure  3  (namely, the direction of the attachment AT), multiple regions for causing the bucket command value β 3r  to differ are set in the vicinity of the bend as described above. For example, the bend includes a part where planes of different inclinations intersect in the direction of the upper swing structure  3 . Furthermore, the bend includes, for example, a part where a plane and a curved plane intersect and where the inclination of the plane to the tangent plane of the curved plane discontinuously changes in the direction of the upper swing structure  3 . Furthermore, the bend includes, for example, a part where the inclination of the tangent plane of the intended construction plane formed of a curved plane discontinuously changes in the direction of the upper swing structure  3 . For example, in the case of the intended construction plane  600 , the regions  610  through  630  are set in a space above the intended construction plane  600  in the vicinity of the bend  603  as described above. In this case, as described above, the region determining part  3004  determines in which of the regions  610  through  630  the bucket  6  is positioned. 
     When the intended construction plane includes no bend, the process of the region determining part  3004  may be omitted. 
     The target trajectory setting part  3005  sets information on a target trajectory for the working part (control reference) of the bucket  6 , such as the teeth tips  6 _ 5  or the back surface  6 _ 3 , for moving the working part along the intended construction plane, based on the data on the intended construction plane. For example, the target trajectory setting part  3005  may set the inclination angle of the intended construction plane in the direction (namely, the longitudinal direction) of the upper swing structure  3  with reference to the machine body (the upper swing structure  3 ) of the shovel  100  as the information on the target trajectory for the working part of the bucket  6 . 
     The target position calculating part  3006  calculates the target position of the working part (control reference) of the bucket  6  based on operation details (the direction of operation and the amount of operation) with respect to a forward or a backward operation on the left operating lever  26 L, the set information on the target trajectory, and the current position of the working part of the bucket  6 . Assuming that the arm  5  moves in response to the direction of operation and the amount of operation of the arm  5  on the left operating lever  26 L, the target position is a position on the target trajectory (in other words, the intended construction plane) that should be a target to be reached during a current control period. The target position calculating part  3006  may, for example, calculate the target position of the working part of the bucket  6  using a map, an arithmetic expression or the like prestored in a secondary storage. 
     Furthermore, the target position calculating part  3006  calculates the target value of the bucket angle (hereinafter “target bucket angle”) based on a region corresponding to the position of the bucket  6  determined by the region determining part  3004 . For example, the target position calculating part  3006  calculates the target bucket angle corresponding to the back surface  6 _ 3  of the bucket  6  parallel to the horizontal plane  601  based on data on the shape of the bucket  6  when the region determining part  3004  determines that the bucket  6  is in the region  610 . Furthermore, for example, when the bucket  6  moves into the region  620  from the region  610  to be determined to be in the region  620  by the region determining part  3004 , the target position calculating part  3006  calculates the bucket angle in a manner in which the back surface  6 _ 3  of the bucket  6  sequentially changes its state from being parallel to the horizontal plane  601  to being parallel to the slope  602 . The same is true for the case where the bucket  6  moves into the region  620  from the region  630  except that the start point and the end point of the changing of the bucket angle are reversed. Furthermore, for example, when the bucket  6  is determined to be in the region  630 , the target position calculating part  3006  calculates the target bucket angle corresponding to the back surface  6 _ 3  of the bucket  6  parallel to the slope  602  based on data on the shape of the bucket  6 . 
     The bucket shape obtaining part  3007  obtains pre-recorded data on the shape of the bucket  6  from an internal memory (for example, a secondary storage), a predetermined external storage, or the like, for example. In this case, the bucket shape obtaining part  3007  may obtain data on the shape of the bucket  6  of a type set by a setting operation through the input device  72  from among pre-recorded data on the shapes of the multiple types of buckets  6 . 
     The movement command generating part  3008  generates a command value β 1r  for the movement of the boom  4  (hereinafter “boom command value”), a command value β 2r  for the movement of the arm  5  (hereinafter “arm command value”), and the command value β 3r  for the movement of the bucket  6  (the bucket command value) based on the target position of the control reference in the attachment AT. For example, the boom command value β 1r , the arm command value β 2r , and the bucket command value β 3r  are a boom angle, an arm angle, and a bucket angle, respectively, at the time when the working part (control reference) of the bucket  6  reaches the target position. The movement command generating part  3008  includes a master command value generating part  3008 A and a slave command value generating part  3008 B. 
     The boom command value β 1r , the arm command value β 2r , and the bucket command value β 3r  may alternatively be the angular velocity of the boom  4  (hereinafter “boom angular velocity”), the angular velocity of the arm  5  (hereinafter “arm angular velocity”), and the angular velocity of the bucket  6  (hereinafter “bucket angular velocity”) necessary for the working part (control reference) of the bucket  6  to reach the target position. Furthermore, the boom command value β 1r , the arm command value β 2r , and the bucket command value β 3r  may alternatively be angular accelerations or the like necessary for the working part (control reference) of the bucket  6  to reach the target position. 
     The master command value generating part  3008 A generates the arm command value β 2r  for the movement of a master element (the arm  5 ) that is an object of the operator&#39;s operation among the constituent motion elements (the boom  4 , the arm  5 , and the bucket  6 ) of the attachment AT. The generated arm command value β 2r  is output to an arm pilot command generating part  3009 B. Specifically, the master command value generating part  3008 A generates the arm command value β 2r  corresponding to the operation details (the direction of operation and the amount of operation) of the left operating lever  26 L. For example, the master command value generating part  3008 A may generate the arm command value β 2r  based on a predetermined map, conversion equation, or the like that defines the relationship between the operation details of the left operating lever  26 L and the arm command value β 2r . 
     Assuming that the operator operates the left operating lever  26 L forward and backward, the master command value generating part  3008 A may be omitted. This is because when the left operating lever  26 L is operated forward or backward, a pilot pressure commensurate with the operation details is applied to the control valves  176 L and  176 R via the shuttle valve  32 AL or  32 AR as described above to allow the arm  5  to move as a master element. 
     The slave command value generating part  3008 B generates command values for the movements of slave elements (the boom  4  and the bucket  6 ) (the boom command value β 1r  and the bucket command value β 3r ) that operate in accordance with (namely, in synchronization with) the movement of the master element among the constituent motion elements of the attachment AT. The generated boom command value β 1r  and bucket command value β 3r  are output to a boom pilot command generating part  3009 A and a bucket pilot command generating part  3009 C, respectively. The slave command value generating part  3008 B generates the boom command value β 1r  and the bucket command value β 3r  such that the slave elements move in accordance with (in synchronization with) the movement of the arm  5  corresponding to the arm command value β 2r  to allow the working part (control reference) of the bucket  6  to reach the target position (namely, to move along the intended construction plane). According to this, the controller  30  can move the working part (control reference) of the bucket  6  along the intended construction plane by moving the two slave elements (the boom  4  and the bucket  6 ) in accordance with (in synchronization with) the movement of the master element (the arm  5 ) corresponding to forward and backward operations on the left operating lever  26 L. 
     The slave command value generating part  3008 B first generates the bucket command value β 3r  corresponding to the pose of the bucket  6  (the bucket angle) at the target position of the working part of the bucket  6 . That is, the slave command value generating part  3008 B generates the bucket command value β 3r  corresponding to the target bucket angle. For example, when the bucket  6  is positioned in the region  610  or the region  630 , the slave command value generating part  3008 B generates the bucket command value β 3r  such that the back surface  6 _ 3  of the bucket  6  is parallel to the horizontal plane  601  or the slope  602 . Furthermore, in response to the entry of the bucket  6  into the region  620  from the region  610  or the region  630 , the slave command value generating part  3008 B generates the bucket command value β 3r  corresponding to the sequentially changing bucket angle during the transition of the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  601  to being parallel to the slope  602  or from being parallel to the slope  602  to being parallel to the horizontal plane  601 . Then, the slave command value generating part  3008 B generates the boom command value β 1r  such that the working part of the bucket  6  reaches the target position, based on the generated arm command value β 2r  and bucket command value β 3r . 
     The pilot command generating part  3009  generates command values for pilot pressures to be applied to the control valves  174  through  176  (hereinafter “pilot pressure command values”) for achieving the boom angle, the arm angle, and the bucket angle corresponding to the boom command value β 1r , the arm command value β 2r , and the bucket command value β 3r . The pilot command generating part  3009  includes the boom pilot command generating part  3009 A, the arm pilot command generating part  3009 B, and the bucket pilot command generating part  3009 C. 
     The boom pilot command generating part  3009 A generates a pilot pressure command value to be applied to the control valves  175 L and  175 R corresponding to the boom cylinder  7  that drives the boom  4 , based on the difference between the boom command value β 1r  and the value of the current boom angle calculated (measured) by a boom angle calculating part  3010 A described below. Then, the boom pilot command generating part  3009 A outputs a control current commensurate with the generated pilot pressure command value to the proportional valve  31 BL or  31 BR. As a result, as described above, a pilot pressure commensurate with the pilot pressure command value output from the proportional valve  31 BL or  31 BR is applied to corresponding pilot ports of the control valves  175 L and  175 R via the shuttle valve  32 BL or  32 BR. Then, through the operations of the control valves  175 L and  175 R, the boom cylinder  7  operates, so that the boom  4  moves to achieve the boom angle corresponding to the boom command value β 1r . 
     The arm pilot command generating part  3009 B generates a pilot pressure command value to be applied to the control valves  176 L and  176 R corresponding to the arm cylinder  8  that drives the arm  5 , based on the difference between the arm command value β 2r  and the value of the current arm angle calculated (measured) by an arm angle calculating part  3010 B described below. Then, the arm pilot command generating part  3009 B outputs a control current commensurate with the generated pilot pressure command value to the proportional valve  31 AL or  31 AR. As a result, as described above, a pilot pressure commensurate with the pilot pressure command value output from the proportional valve  31 AL or  31 AR is applied to corresponding pilot ports of the control valves  176 L and  176 R via the shuttle valve  32 AL or  32 AR. Then, through the operations of the control valves  176 L and  176 R, the arm cylinder  8  operates, so that the arm  5  moves to achieve the arm angle corresponding to the arm command value β 2r . 
     The bucket pilot command generating part  3009 C generates a pilot pressure command value to be applied to the control valve  174  corresponding to the bucket cylinder  9  that drives the bucket  6 , based on the difference between the bucket command value β 3r  and the value of the current bucket angle calculated (measured) by a bucket angle calculating part  3010 C described below. Then, the bucket pilot command generating part  3009 C outputs a control current commensurate with the generated pilot pressure command value to the proportional valve  31 CL or  31 CR. As a result, as described above, a pilot pressure commensurate with the pilot pressure command value output from the proportional valve  31 CL or  31 CR is applied to a corresponding pilot port of the control valve  174  via the shuttle valve  32 CL or  32 CR. Then, through the operation of the control valve  174 , the bucket cylinder  9  operates, so that the bucket  6  operates to achieve the bucket angle corresponding to the bucket command value β 3r . 
     The pose angle calculating part  3010  calculates (measures) the (current) boom angle, arm angle, and bucket angle, etc., based on detection signals of the boom angle sensor S 1 , the arm angle sensor S 2 , and the bucket angle sensor S 3 . The pose angle calculating part  3010  includes the boom angle calculating part  3010 A, the arm angle calculating part  3010 B, and the bucket angle calculating part  3010 C. 
     The boom angle calculating part  3010 A calculates (measures) the boom angle, etc., based on a detection signal fed from the boom angle sensor S 1 . 
     The arm angle calculating part  3010 B calculates (measures) the arm angle, etc., based on a detection signal fed from the arm angle sensor S 2 . 
     The bucket angle calculating part  3010 C calculates (measures) the bucket angle, etc., based on a detection signal fed from the bucket angle sensor S 3 . 
     Thus, according to this embodiment, multiple regions between which a control command (the bucket command value β 3r  for the movement of the bucket  6  generated by the controller  30  differs are set in the vicinity of a bend of an intended construction plane. Specifically, a region (for example, the region  610 ) corresponding to a first part of the intended construction surface (for example, the horizontal plane  601 ) bordering on the bend (for example, the bend  603 ), a region (for example, the region  620 ) corresponding to the bend, and a region (for example, the region  630 ) corresponding to a second part of the intended construction surface (for example, the slope  602 ) bordering on the bend are set. 
     This enables the shovel  100  to control the bucket  6  differently between the multiple regions so that the working part of the bucket  6  appropriately moves along the intended construction plane. In particular, in the region corresponding to the bend, it is possible to appropriately change the pose of the bucket  6  (change the bucket angle) as required with the movement of the bucket  6  between the first part of the intended construction plane and the second part of the intended construction plane whose boundary is the bend. Therefore, the shovel  100  can avoid a situation where the bucket  6  bites the bend  603  or is out of alignment with the shape of the bend  603  and appropriately shape the intended construction plane  600  in the vicinity of the bend  603  with the working part of the bucket  6 . 
     Furthermore, when the position of the bucket  6  moves from a first region into a second region among the set regions, the controller  30  may generate a control command for the movement of the bucket  6  corresponding to the second region. For example, in response to the entry of the bucket  6  into the region  620  from the region  610  or the region  630 , the controller  30  generates a control command corresponding to the region  620 , namely, a control command for the movement of the bucket  6  for changing the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  601  to being parallel to the slope  602  or from being parallel to the slope  602  to being parallel to the horizontal plane  601 . Furthermore, for example, in response to the entry of the bucket  6  into the region  610  from the region  620 , the controller  30  generates a control command corresponding to the region  610 , namely, a control command for the movement of the bucket  6  for keeping the back surface  6 _ 3  of the bucket  6  parallel to the horizontal plane  601 . Furthermore, for example, in response to the entry of the bucket  6  into the region  630  from the region  620 , the controller  30  generates a control command corresponding to the region  630 , namely, a control command for the movement of the bucket  6  for keeping the back surface  6 _ 3  of the bucket  6  parallel to the slope  602 . 
     This enables the shovel  100  to cause the mode of controlling the bucket  6  to specifically differ between the multiple regions. 
     Furthermore, the controller  30  may generate a control command for the movement of the boom  4  (the boom command value β 1r ) based on a control command for the movement of the bucket  6  (the bucket command value β 3r ). Specifically, the controller  30  may generate a control command for the movement of the boom  4  based on a control command for the movement of the arm  5  corresponding to the arm operation (the arm command value β 2r ) and a control command for the movement of the bucket  6  that is generated earlier. The controller  30 , for example, may generate a control command for the movement of the bucket  6  earlier to achieve the target pose of the bucket  6  (the target bucket angle) relative to the intended construction plane. 
     This enables the controller  30  to control the working part of the bucket  6  to move along the intended construction plane by determining the movement of the boom  4  based on the movement of the arm  5  corresponding to the arm operation and the movement of the bucket  6  determined earlier. 
     &lt;Another Specific Example of Motion Based on Machine Control Function of Shovel&gt; 
       FIG. 9  is a diagram illustrating another example of a motion based on the machine control function of the shovel  100 , showing a situation where the shovel  100  is performing leveling work (ground leveling work), moving the back surface  6 _ 3  of the bucket  6  along an intended construction plane  800  with the machine control function. 
     In  FIG. 9 , of the attachment AT of the shovel  100 , only the bucket  6  is depicted, and a depiction of the boom  4  and the arm  5  is omitted. Furthermore, in  FIG. 9 , in order to depict changes over time with the movement of the bucket  6 , the bucket  6  is conveniently indicated by  6 I,  6 J,  6 K and  6 L at predetermined times. 
     As illustrated in  FIG. 9 , the intended construction plane  800  includes a slope  801  (a first intended construction plane), a horizontal plane  802  (a second intended construction plane) positioned on the base side of the slope  801 , and a bend  803  at which the slope  801  and the horizontal plane  802  intersect (a boundary portion of the intended construction plane). 
     Furthermore, a space above the intended construction plane  800  is divided into the regions  810 ,  820  and  830  in accordance with the shape of the intended construction plane  800 . Specifically, the region  810  is part of a spatial region above the slope  801  which part is on the slope  801  side (the right side in the drawing) of a vertical plane  815  that passes through the bend  803  and is perpendicular to the horizontal plane  802 . The region  820  is part of a spatial region delimited by the vertical plane  815  and a vertical plane  825  perpendicular to the slope  801  above the bend  803 . The region  830  is part of a spatial region above the horizontal plane  802  which part is on the horizontal plane  802  side (the left side in the drawing) of the vertical plane  825 . The regions  810  through  830  are preset based on the shape of the intended construction plane  800  in the shovel  100 . 
     The same as in the specific examples of  FIGS. 7A and 7B , the shovel  100  automatically moves the boom  4  and the bucket  6  according to the operator&#39;s operation of the arm  5  (hereinafter “arm operation”) to move the bucket  6  such that the back surface  6 _ 3  of the bucket  6  is aligned with the intended construction plane. 
     According to this example, with the machine body being positioned on the horizontal plane  802  side, the shovel  100  moves the bucket  6 , drawing the bucket  6  toward the machine body. Aligning the back surface  6 _ 3  of the bucket  6  with the intended construction plane  800 , the shovel  100  performs ground leveling work from the slope  801  (the state of a bucket  6 I) to the bend  803  (the states of buckets  6 J and  6 K) and to the horizontal plane  802  (the state of a bucket  6 L). 
     When the bucket  6  is positioned in the region  810  (the state of the bucket  6 I), the controller  30  controls the bucket angle to keep the back surface  6 _ 3  of the bucket  6  parallel to the slope  801 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  810  when the entirety of the bucket  6  is included in the region  810 . Furthermore, the controller  30  controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the slope  801 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the slope  801 . This enables the shovel  100  to move the bucket  6  along the slope  801 . 
     When the position of the bucket  6  changes from being in the region  810  to being in the region  820  (the state of the bucket  6 J), the controller  30  controls the bucket angle to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the slope  801  to being parallel to the horizontal plane  802 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  820  when at least part of the bucket  6  is included in the region  820  and when the bucket  6  keeps on changing its pose as the bucket  6  enters the region  820 . Furthermore, the controller  30  controls the boom angle based on the arm angle determined by the details of the arm operation and the bucket angle sequentially determined during the transition of the state of the bucket surface  6 _ 3  of the bucket  6  from being parallel to the slope  801  to being parallel to the horizontal plane  802 . This enables the shovel  100  to appropriately shape the intended construction plane  800  in the vicinity of the bend  803  with the back surface  6 _ 3  of the bucket  6 . 
     When the bucket  6  is positioned in the region  830  (the states of the buckets  6 J and  6 K), the controller  30  controls the bucket angle to keep the back surface  6 _ 3  of the bucket  6  parallel to the horizontal plane  802 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  830  when the changing of the pose of the bucket  6 , which starts in response to the entry of the bucket  6  into the region  820 , is completed and at least part of the bucket  6  is included in the region  830 . Furthermore, the controller  30  controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the horizontal plane  802 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the horizontal plane  802 . This enables the shovel  100  to move the bucket  6  along the horizontal plane  802 . 
     According to this example, first, the controller  30  controls the back surface  6 _ 3  of the bucket  6  serving as the control reference (working part) such that the back surface  6 _ 3  is aligned with the slope  801  as the target trajectory. In this case, the correspondence between the control reference and the target trajectory is set on the back surface  6 _ 3  of the bucket  6  and the slope  801 . At this point, the controller  30  determines the presence or absence of the bend  803  in the set intended construction plane  800 , and in response to determining the presence of the bend  803 , executes control that accommodates a change in the intended construction plane  800  at the bend  803 . 
     According to this example, as illustrated in  FIG. 9 , the change between the adjoining intended construction planes  800  at the bend  803  in the traveling direction of the control reference (working part) is less than 180°. In this case, the controller  30  determines whether the teeth tips  6 _ 5 , which are the leading end of the bucket  6  in the traveling direction, have reached a bent portion (the bend  803 ) to the next intended construction plane (the horizontal plane  802 ). In response to determining that the teeth tips have reached the bend, the controller  30  changes the correspondence between the control reference and the target trajectory to the back surface  6 _ 3  of the bucket  6  and the horizontal plane  802 . Then, the controller  30  controls the bucket angle to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the slope  801  to being parallel to the horizontal plane  802 . At this point, the bucket angle is controlled such that the back surface  6 _ 3  of the bucket  6  parallels the horizontal plane  802  or is within a predetermined angular range relative to parallelism to the horizontal plane  802 . 
     Thereafter, the controller  30  controls the back surface  6 _ 3  of the bucket  6  serving as the control reference (working part) to be aligned with the horizontal plane  802  as the target trajectory. 
     Furthermore, the same as in the specific example of  FIG. 7A , with the machine body being positioned on the horizontal plane  802  side, the shovel  100  may move the bucket  6 , pushing the bucket  6  away from the machine body. In this case, aligning the back surface  6 _ 3  of the bucket  6  with the intended construction plane  800 , the shovel  100  performs ground leveling work from the horizontal plane  802  (the state of the bucket  6 L) to the bend  803  (the states of the buckets  6 K and  6 J) and to the slope  801  (the state of the bucket  6 I). 
     When the bucket  6  is positioned in the region  830  (the state of the bucket  6 L), the controller  30  controls the bucket angle to keep the back surface  6 _ 3  of the bucket  6  parallel to the horizontal plane  802 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  830  when the entirety of the bucket  6  is included in the region  830 . Furthermore, the same as in the case of  FIG. 9 , the controller  30  controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the horizontal plane  802 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the horizontal plane  802 . This enables the shovel  100  to move the bucket  6  along the horizontal plane  802 . 
     When the position of the bucket  6  changes from being in the region  830  to being in the region  820  (the state of the bucket  6 K), the controller  30  controls the bucket angle to change the state of the back surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  802  to being parallel to the slope  801 . Furthermore, the controller  30  controls the boom angle based on the arm angle determined by the details of the arm operation and the bucket angle sequentially determined during the transition of the state of the bucket surface  6 _ 3  of the bucket  6  from being parallel to the horizontal plane  802  to being parallel to the slope  801 . This enables the shovel  100  to appropriately shape the intended construction plane  800  in the vicinity of the bend  803  with the back surface  6 _ 3  of the bucket  6 . 
     When the bucket  6  is positioned in the region  810  (the states of the buckets  6 J and  6 I), the controller  30  controls the bucket angle to keep the back surface  6 _ 3  of the bucket  6  parallel to the slope  801 . For example, the controller  30  may determine that the bucket  6  is positioned in the region  810  when the changing of the pose of the bucket  6 , which starts in response to the entry of the bucket  6  into the region  820 , is completed and at least part of the bucket  6  is included in the region  810 . Furthermore, the controller  30  controls the boom angle such that the back surface  6 _ 3  of the bucket  6  contacts (coincides with) the slope  801 , based on the arm angle determined by the details of the arm operation and the bucket angle determined in relation to the slope  801 . This enables the shovel  100  to move the bucket  6  along the slope  801 . 
     Thus, according to this example, the same as in the specific examples of  FIGS. 7A and 7B , multiple regions (the regions  810  through  830 ) between which a control command for the movement of the bucket  6  (the bucket command value β 3r ) generated by the controller  30  differs are set in the vicinity of the bend  803  of the intended construction plane  800 . Specifically, when the bucket  6  is positioned in the region  810  or the region  830 , the controller  30  generates a control command for the movement of the bucket  6  to keep the bucket angle parallel to the slope  801  or the horizontal plane  802 . In contrast, when the position of the bucket  6  enters the region  820  from the region  810  or the region  830 , the controller  30  generates a control command for the movement of the bucket  6  to change the bucket angle from being parallel to the slope  801  to being parallel to the horizontal plane  802  or from being parallel to the horizontal plane  802  to being parallel to the slope  801 . This enables the shovel  100  to appropriately move the working part of the bucket  6  along the intended construction plane  800  in the vicinity of the bend  803  of the intended construction plane  800 , the same as in the specific examples of  FIGS. 7A and 7B . [Operation] According to this embodiment, as the control reference (working part) moves, the controller  30  switches the correspondence between the control reference (working part) and the target trajectory (intended construction plane) at a bent portion on the target trajectory. Specifically, the controller  30  may change the manner of switching the correspondence between the control reference (working part) and the target trajectory (the intended construction plane) according to how the target trajectory changes at the bent portion (bend). For example, when the change between adjoining intended construction planes at the bend is less than 180°, the controller  30  may switch the correspondence between the control reference and the target trajectory to the next target trajectory (intended construction plane) in response to the leading end of the end attachment along the target trajectory arriving at the bend. In contrast, for example, when the change between adjoining intended construction planes at the bend is more than 180°, the controller  30  may switch the correspondence between the control reference and the target trajectory to the next target trajectory (intended construction plane) in response to the trailing end of the end attachment along the target trajectory passing the extended plane of the next target trajectory at the bend. 
     This enables the controller  30  to appropriately cause the control reference (working part) of the end attachment to perform tracking according to a change in the target trajectory (intended construction plane) at the bent portion (bend). 
     VARIATIONS AND MODIFICATIONS 
     An embodiment is described in detail above. The present disclosure, however, is not limited to the specifically disclosed embodiment, and variations and modifications may be made without departing from the scope of the present disclosure. 
     For example, while the shovel  100  moves the working part of the bucket  6  along the intended construction plane with the machine control function (semi-automatic operation function) according to the above-described embodiment, the bucket  6  may be similarly moved by a complete automatic operation function or an autonomous operation function. 
     Furthermore, according to the above-described embodiment, the shovel  100  is configured such that various motion elements such as the lower traveling structure  1 , the upper swing structure  3 , the boom  4 , the arm  5 , and the bucket  6  are all hydraulically driven. The shovel  100 , however, may also be configured such that one or more of them are electrically driven. That is, according to the above-described embodiment, one or more of the driven elements of the shovel  100  may be driven by electric actuators (for example, an electric motor, etc.).