Patent Publication Number: US-2022219954-A1

Title: Work machine and video display control method for work machine

Description:
TECHNICAL FIELD 
     The present invention relates to a work machine and an image display control method for the work machine. 
     BACKGROUND ART 
     A work machine such as a crane includes a movable part such as a stewing body and a winch drum, and a hydraulic actuator that drives the movable part such as a hydraulic motor. Furthermore, the work machine may include a camera that captures images around the movable part. 
     In the above-described case, the work machine includes a controller that causes a display device in a cab to selectively display one of a plurality of candidate images including, for example, a monitoring image of the movable part. With this configuration, an operator can confirm on a screen of the display device whether there is a dangerous situation in which the movable part is likely to come into contact with an obstacle such as a person. 
     For example, a technique is known in which the work machine includes a plurality of cameras and a plurality of proximity sensors corresponding to the plurality of cameras, and the controller automatically causes the display device to display the captured image of the camera corresponding to the proximity sensor that detects the obstacle (see, for example, Patent Literature 1). With this technique, the operator can quickly check the image of an area where the obstacle is detected with the display device without time and effort. 
     In that connection, when an operator is checking information about various states on the screen of the display device in the cab at a work site, another worker than the operator may perform various preparatory work around the movable part of the work machine. 
     In the above-described case, if the captured image of the camera is automatically displayed on the display device every time the proximity sensor detects the worker, the work of checking the information on the screen of the display device by the operator may be hindered. 
     Meanwhile, if a function of automatic control of the image display in response to the detection of the obstacle is stopped in response to the manipulation by the operator in order to avoid hindrance of the checking work, the operator may forget to perform the manipulation of releasing stop of the automatic control function of the image display after the checking work. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent Application Laid-Open No. 2002-327470 
       
    
     SUMMARY OF INVENTION 
     An object of the present invention is to provide a work machine and an image display control method for the work machine that can avoid unnecessary, automatic switching of display contents of the display device even unless the operator stops the function of automatic control of the image display. 
     A work machine according to one aspect of the present invention includes a movable part, an actuator, a drive manipulation unit, a drive control unit, a preparatory manipulation unit, a state switching unit, a display device, an obstacle detection device, a state determination unit, and a display control unit. The actuator drives the movable part. The drive manipulation unit receives a drive manipulation instructing the actuator to operate. The drive control unit controls the operation of the actuator in response to the drive manipulation. The preparatory manipulation unit receives a preparatory manipulation instructing the actuator to prepare for the operation. The state switching unit shifts a state of the actuator in response to the preparatory manipulation from a suspended state in which the actuator is blocked from being started by control of the drive control unit to a standby state in which the actuator is able to be started by the control of the drive control unit. The display device is configured to display an image. The obstacle detection device detects an obstacle existing in one or more monitoring areas that are set to correspond to the movable part. The state determination unit determines whether the state of the actuator is the standby state or the suspended state under circumstances where the actuator is at a stop. On determination that the state of the actuator is the standby state, the display control unit executes automatic image output that is processing for causing the display device to display a monitoring image that is an image corresponding to a monitoring area in which the obstacle is detected out of the one or more monitoring areas, and on determination that the state of the actuator is the suspended state, the display control unit stops the execution of the automatic image output. 
     An image display control method for a work machine according to another aspect of the present invention is a control method for the work machine including the movable part, the actuator, the drive manipulation unit, the drive control unit, the preparatory manipulation unit, the state switching unit, the display device, and the obstacle detection device. The image display control method includes: as processes to be executed by a processor included in the work machine, a first process of determining whether the state of the actuator is the standby state or the suspended state under circumstances where the actuator is at a stop; and a second process. On determination in the first process that the state of the actuator is the standby state, automatic image output is executed in the second process, the automatic image output being processing for causing the display device to display a monitoring image corresponding to a monitoring area in which the obstacle is detected out of the one or more monitoring areas. On determination in the first process that the state of the actuator is the suspended state, the execution of the automatic image output is stopped in the second process. 
     The work machine and the image display control method make it possible to provide a work machine and an image display control method for the work machine that can avoid unnecessary, automatic switching of display contents of the display device even unless the operator stops the function of automatic control of the image display. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a crane according to an embodiment. 
         FIG. 2  is a block diagram showing a configuration of control-related devices in the crane according to the embodiment. 
         FIG. 3  is a block diagram showing a configuration of a controller in the crane according to the embodiment. 
         FIG. 4  is a block diagram showing a configuration of TOF sensor units in the crane according to the embodiment. 
         FIG. 5  is a layout diagram of an obstacle detection device and monitoring cameras in the crane according to the embodiment. 
         FIG. 6  is a flowchart showing one example of a procedure for first monitoring control in the crane according to the embodiment. 
         FIG. 7  is a flowchart showing one example of a procedure for second monitoring control the crane according to the embodiment. 
         FIG. 8  is a flowchart showing one example of a procedure for invalid area setting processing in the crane according to the embodiment. 
         FIG. 9  is a plan view showing a first monitoring area in the crane according to the embodiment. 
         FIG. 10  is a plan view showing a second monitoring area in the crane according to the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is one example of embodying the present invention, and does not limit the technical scope of the present invention. 
     [Schematic Configuration of Crane  10 ] 
     A crane  10  according to the embodiment of the present invention is one example of a stewing work machine. The crane  10  is a work machine that hoists and moves a hoist load  9 . Hereinafter, an example in which the crane  10  is a mobile crane will be described. 
     As shown in  FIG. 1 , the crane  10  includes a lower travelling body  11 , an upper stewing body  12 , a boom  21 , a hook  30 , a luffing rope  31 , and a hoisting rope  32 . The upper stewing body  12  includes a stewing frame slewably supported by the lower travelling body  11 , a cab  13 , a gantry  15 , winch devices  16 , and a counterweight  17 . The winch devices  16  include a first winch device  161  and a second winch device  162 . 
     The gantry  15  is fixed to the stewing frame in a standing up state from the stewing frame of the upper stewing body  12 . The counterweight  17  is coupled with the stewing frame of the upper stewing body  12  and is disposed at the rear of the stewing frame. 
     The lower travelling body  11  is a pedestal that supports the upper stewing body  12  to be able to slew. The upper stewing body  12  is located on an upper part of the lower travelling body  11  to be able to slew with respect to the lower travelling body  11 . The upper stewing body  12  is driven to slew by a slewing motor  441  located on the lower travelling body  11  (see  FIG. 2 ). The lower travelling body  11  is one example of a lower base. 
     The cab  13  is a control cabin. The cab  13  is coupled with the slewing frame of the upper slewing body  12  and is disposed at the front of the stewing frame. 
     The upper slewing body  12 , the boom  21 , the hook  30 , the luffing rope  31 , and the hoisting rope  32  constitute a slewing part  120  that slews integrally. 
     The slewing motor  441  is a hydraulic motor. The crane  10  also includes a slewing brake device  440  that exerts braking force on the slewing motor  441  (see  FIG. 2 ). The stewing brake device  440  is a so-called negative brake, and exerts braking force on the slewing motor  441  under circumstances where no hydraulic pressure is applied. 
     The crane  10  shown in  FIG. 1  is a mobile crane. Therefore, the lower travelling body  11  includes a travelling device  14 . The travelling device  14  is coupled with a frame of the lower travelling body  11 .  FIG. 1  shows an example in which the travelling device  14  is a crawler type device. 
     The boom  21  is supported by the upper slewing body  12  by coupling a root thereof with the slewing frame of the upper slewing body  12 . The boom  21  is formed to extend in one direction from the slewing frame of the upper slewing body  12  and supports the hoisting rope  32  that suspends the hoist load  9 . The boom  21  is configured to tuff around the root coupled with the upper slewing body  12 . 
     The hoisting rope  32  is hung on a boom point idler sheave  22  provided at the tip of the boom  21 . The luffing rope  31  is hung on a gantry sheave  23  provided at the tip of the gantry  15 . 
     The first winch device  161  supports the boom  21  via the lulling rope  31 . Meanwhile, the second winch device  162  supports the hook  30  via the hoisting rope  32 . 
     The first winch device  161  changes an elevation angle of the boom  21  by winding or unwinding the luffing rope  31 . That is, the boom  21  is driven by the first winch device  161  and the luffing rope  31  such that the elevation angle can be changed. 
     The second winch device  162  causes the hook  30  to move up and down by winding or unwinding the hoisting rope  32 . 
     The hoist load  9  is hung on the hook  30 . The counterweight  17  balances loads of the boom  21 , the hook  30 , and the hoist load  9 . 
     As shown in  FIG. 2 , the crane  10  includes: drive-system devices such as an engine  41 , a hydraulic pump unit  42 , a hydraulic control valve  43 , a pilot pressure valve  43   x , and a plurality of hydraulic actuators  44 ; a manipulation device  5 ; a controller  6 ; and a display device  7 . 
     Devices for human interface such as the manipulation device  5  and the display device  7  are located in the cab  13 . Furthermore, the crane  10  also includes a state detection device  45  that detects states of various devices included in the crane  10 , a plurality of cameras  46 , and an image switch  47 . 
     The manipulation device  5  is a device that receives manipulations of an operator. The display device  7  is a device that displays information, for example, a panel display device such as a liquid crystal display unit. In addition, the display device  7  can also display a monitoring image captured by the camera  46 . 
     The manipulation device  5  includes a boarding and alighting cutoff device  51 , a stewing manipulation device  52 , a slewing brake manipulation device  53 , a manipulation input device  54 , and the like. 
     The boarding and alighting cutoff device  51  includes a boarding and alighting cutoff lever  511 . In response to two types of manipulations on the boarding and alighting cutoff lever  511 , the boarding and alighting cutoff device  51  outputs, to the controller  6 , a signal instructing a state of the pilot pressure valve  43   x  to be switched. The controller  6  outputs a pilot pressure control signal according to details of the manipulation on the boarding and alighting cutoff lever  511  to the pilot pressure valve  43   x.    
     The slewing manipulation device  52  includes a slewing lever  521  that can be displaced in two directions from a neutral position. The slewing manipulation device  52  is one example of a drive manipulation unit. According to a manipulating direction and manipulating amount on the slewing lever  521 , the slewing manipulation device  52  outputs, to the controller  6 , a manipulation signal instructing a rotation direction and rotation speed of the slewing motor  441 . According to details of the manipulation on the slewing lever  521 , the controller  6  controls a part of the hydraulic control valve  43  corresponding to the slewing motor  441 . Specifically, the control is as follows. 
     In the present embodiment, the hydraulic control valve  43  includes a slewing switching valve and one pair of electromagnetic proportional valves. The hydraulic pump unit  42  includes a main pump that discharges working oil and a pilot pump that discharges pilot oil. The slewing switching valve is interposed between the main pump and the slewing motor  441 . The slewing switching valve is a pilot-operated hydraulic switching valve including one pair of pilot ports. The slewing motor  441  includes one pair of ports that receive the supply of working oil. The one pair of electromagnetic proportional valves is interposed between the pilot pump and the one pair of pilot ports of the slewing switching valve. One of the one pair of electromagnetic proportional valves is connected to one of the one pair of pilot ports of the slewing switching valve, and the other of the one pair of electromagnetic proportional valves is connected to the other of the one pair of pilot ports of the slewing switching valve. The pilot pressure valve  43   x  is interposed between the pilot pump and the one pair of electromagnetic proportional valves. 
     On receipt of input of the manipulation signal corresponding to the manipulating direction and manipulating amount on the slewing lever  521 , the controller  6  outputs a drive control signal according to the manipulating amount to one of the one pair of electromagnetic proportional valves corresponding to the manipulating direction. The one electromagnetic proportional valve to which the drive control signal is input performs an opening and closing operation to allow the pilot pressure according to the drive control signal to be supplied to the pilot port corresponding to the one electromagnetic proportional valve out of the one pair of pilot ports of the slewing switching valve. 
     By displacement of a spool in a direction according to the pilot port with a stroke according to the pilot pressure, the slewing switching valve selectively guides the working oil for driving the slewing motor  441  from the main pump to one of the one pair of ports of the slewing motor  441 , and adjusts a slewing flow rate, which is a flow rate of the working oil supplied to the slewing motor  441 , to the flow rate according to the stroke. 
     The slewing brake manipulation device  53  includes a brake button  531 . In response to an ON manipulation or OFF manipulation on the brake button  531 , the slewing brake manipulation device  53  outputs, to the controller  6 , a signal instructing the slewing brake device  440  to be switched to the brake ON state or brake OFF state. 
     According to details of the manipulation on the brake button  531 , the controller  6  switches the slewing brake device  440  to the brake ON state or brake OFF state. The brake ON state is a state of applying braking force to the slewing motor  441 , and the brake OFF state is a state of releasing the braking force on the slewing motor  441 . 
     Note that the brake ON state means the brake state of the slewing brake device  440 , and the brake OFF state means the brake release state of the slewing brake device  440 . In addition, the ON manipulation and the OFF manipulation on the brake button  531  are one example of the brake manipulation and the brake release manipulation, respectively. 
     The manipulation input device  54  receives information input by the operator. For example, the manipulation input device  54  is a touch panel integrally configured with the display device  7 , or the like. In addition, the manipulation input device  54  may be a device that receives information input by a voice manipulation of the operator. 
     The state detection device  45  includes a load meter  451 , a luffing angle detection device  452 , a slewing angle detection device  453 , and an obstacle detection device  454 . The controller  6  is configured to communicate with other devices such as the state detection device  45  and the manipulation device  5  through a vehicle-mounted network  100  such as a controller area network (CAN). Various detection results of the state detection device  45  are transmitted to the controller  6  through the vehicle-mounted network  100 . 
     The load meter  451  detects weight of the hoist load  9 . The lulling angle detection device  452  includes a sensor that detects a luffing angle of the boom  21 , that is, an elevation angle of the boom  21 . The slewing angle detection device  453  includes a sensor that detects an angle at which the upper slewing body  12  slews from a reference direction of the lower travelling body  11 . 
     The obstacle detection device  454  includes at least one sensor that detects an obstacle existing in a plurality of monitoring areas T 0  set in advance with respect to the upper slewing body  12 . The obstacle is mainly a person. 
     In the present embodiment, the obstacle detection device  454  is configured to individually detect the obstacle existing in each of eight monitoring areas T 0  including a front area Ta 0 , front and left area Tb 0 , left side area Tc 0 , rear and left area Td 0 , front and right area Te 0 , right side area Tf 0 , rear and right area Tg 0 , and lower center area Th 0 . 
     The front area Ta 0 , front and left area Tb 0 , left side area Tc 0 , rear and left area Td 0 , front and right area Te 0 , right side area Tf 0 , and rear and right area Tg 0  are areas around the upper slewing body  12 . In the following description, these seven monitoring areas T 0  may be referred to as outer peripheral monitoring areas. 
     Meanwhile, the lower center area Th 0  is an area in a maintenance hole  12   a  formed at the bottom of the upper slewing body  12 . 
     In the present embodiment, the obstacle detection device  454  includes seven time of flight (TOF) sensor units  454   a  to  454   g  corresponding to the seven monitoring areas T 0  (the outer peripheral monitoring areas), and a motion sensor  454   h  corresponding to the lower center area Th 0 . 
     Each of the TOF sensor units  454   a  to  454   g  detects the obstacle existing in a designated area set within a unique monitoring range, and detects the three-dimensional position of the obstacle. 
     As shown in  FIG. 4 , each of the TOF sensor units  454   a  to  454   g  includes a TOF sensor  4541  that uses infrared light to detect the distance to the obstacle for each two-dimensional pixel in the visual field range. That is, the TOF sensor  4541  is configured to detect the three-dimensional position of the obstacle in the visual field range. The visual field range is one example of the unique monitoring range. In the present embodiment, each TOF sensor  4541  is attached to the upper slewing body  12 , but the attachment position of the TOF sensor  4541  is not limited to the upper slewing body  12 . 
     Furthermore, each of the TOF sensor units  454   a  to  454   g  includes a data processing device  4542  and a communication interface  4543 . The communication interface  4543  is a device that communicates with other devices such as the controller  6  through the vehicle-mounted network  100 . 
     The data processing device  4542  acquires data of the designated area from the controller  6 , and outputs the detection result of the position of the obstacle closest to the TOF sensor  4541  out of the obstacles detected in the designated area in the visual field range by the TOF sensor  4541  to the controller  6  through the vehicle-mounted network  100 . 
     Since the amount of information in the detection result of the TOF sensor  4541  is large, if detection data of the TOF sensor  4541  is transmitted as it is via the vehicle-mounted network  100 , communication of other data may be hindered. The communication load for transmitting the detection result of the obstacle detection device  454  is reduced by the above-described processing by the data processing device  4542 . 
     The motion sensor  454   h  detects a person existing in the lower center area Th 0 . The motion sensor  454   h  is, for example, an infrared sensor, an optical sensor, or the like. Note that the person existing in the lower center area Th 0  is one example of the obstacle. 
     The plurality of cameras  46  is disposed on the upper slewing body  12  and captures images of the eight monitoring areas T 0 . In the present embodiment, the crane  10  includes eight cameras  46  corresponding to the eight monitoring areas T 0 . In the following description, the image of the monitoring area T 0  captured by the camera  46  is referred to as a monitoring image. Note that one camera  46  may capture images of a plurality of monitoring areas T 0 . 
     In response to an image selection signal transmitted from the controller  6  through the vehicle-mounted network  100 , the image switch  47  outputs, to the display device  7 , an image signal of one of a plurality of candidate images including the monitoring images of the eight monitoring areas T 0 . That is, the controller  6  controls the image switch  47  to cause the display device  7  to display one of the plurality of candidate images. That is, by controlling the image switch  47 , the controller  6  may cause the display device  7  to display two or more images of the plurality of candidate images. 
     The engine  41  is a diesel engine that drives the hydraulic pump unit  42 . The pilot pressure valve  43   x  switches from one of the ON state (one example of allowable state) and the OFF state (one example of blocking state) to the other in response to the pilot pressure control signal supplied from the controller  6 . 
     The pilot pressure valve  43   x  causes the pilot pressure to act on the hydraulic control valve  43  in the ON state, and cuts off the pilot pressure on the hydraulic control valve  43  (specifically, the slewing switching valve of the hydraulic control valve  43 ) in the OFF state. The pilot pressure is pressure of a pressure oil (pilot oil) output from the pilot pump of the hydraulic pump unit  42 . Specifically, in the present embodiment, the pilot pressure valve  43   x  includes a solenoid valve capable of switching between the ON state and the OFF state by the pilot pressure control signal output from the controller  6  according to details of the manipulation on the boarding and alighting cutoff lever  511 . 
     Two types of manipulations on the boarding and alighting cutoff lever  511  are a manipulation of instructing the pilot pressure valve  43   x  to switch to the OFF state, and a manipulation of instructing the pilot pressure valve  43   x  to switch to the ON state. 
     The manipulation of instructing the pilot pressure valve  43   x  to switch to the ON state is one example of a preparatory manipulation of instructing the slewing motor  441  to prepare for an operation. The boarding and alighting cutoff lever  511  is one example of a preparatory manipulation unit that receives the preparatory manipulation. The manipulation of instructing the pilot pressure valve  43   x  to switch to the OFF state is one example of a suspend manipulation. 
     When the pilot pressure valve  43   x  is in the OFF state to block the pilot pressure from acting on the hydraulic control valve  43 , the hydraulic control valve  43  cannot supply the working oil to the hydraulic actuator  44  such as the slewing motor  441  even if the hydraulic control valve  43  receives, from the controller  6 , the drive control signal instructing the upper slewing body  12  to slew. Specifically, when the pilot line, which is a line between the pilot pump and the one pair of electromagnetic proportional valves, is cut off by switching the pilot pressure valve  43   x  to the OFF state, even if the drive control signal is input from the controller  6  to one of the one pair of electromagnetic proportional valves in response to a slewing manipulation on the slewing lever  521 , the pilot pressure is not supplied to the pilot port of the slewing switching valve. Therefore, when the pilot pressure valve  43   x  is in the OFF state, the slewing switching valve of the hydraulic control valve  43  cannot supply the working oil discharged from the main pump to the slewing motor  441 . As will be described later, the hydraulic control valve  43  is controlled by a stewing control unit  63 , which is a part of the controller  6 . 
     In the present embodiment, when the pilot pressure valve  43   x  is in the OFF state to block the pilot pressure from acting on the hydraulic control valve  43 , whereby the slewing motor  411  cannot receive the supply of the working oil, the state of the slewing motor  411  is referred to as a suspended state. When the state of the slewing motor  411  is the suspended state, the slewing motor  411  cannot be started by the control of the slewing control unit  63 . That is, the suspended state is a state in which the slewing motor  411  is blocked from being started by the control of the slewing control unit  63  of the controller  6 . 
     Meanwhile, when the pilot pressure valve  43   x  is in the ON state to allow the pilot pressure to act on the hydraulic control valve  43 , the hydraulic control valve  43  can supply the working oil to the hydraulic actuator  44  such as the slewing motor  441  when the hydraulic control valve  43  receives, from the controller  6 , the drive control signal instructing the upper slewing body  12  to slew. Specifically, in a case where the cutoff of the pilot line is released by switching the pilot pressure valve  43   x  to the ON state, when the drive control signal is input from the controller  6  to one of the one pair of electromagnetic proportional valves in response to the slewing manipulation on the stewing lever  521 , the pilot pressure is supplied to the pilot port of the stewing switching valve. Therefore, when the pilot pressure valve  43   x  is in the ON state, the slewing switching valve of the hydraulic control valve  43  can supply the working oil discharged from the main pump to the slewing motor  441 . 
     In the present embodiment, when the pilot pressure valve  43   x  is in the ON state to allow the pilot pressure to act on the hydraulic control valve  43 , thereby allowing the slewing motor  411  to receive the supply of the working oil, the state of the slewing motor  411  is referred to as a standby state. When the state of the slewing motor  411  is the standby state, the slewing motor  411  can be started by the control of the slewing control unit  63 . That is, the standby state is a state in which the slewing motor  411  can be started by the control of the slewing control unit  63  of the controller  6 . 
     In addition, as will be described later, a main control unit  61 , which is another part of the controller  6 , controls the pilot pressure valve  43   x  in response to a manipulation on the boarding and alighting cutoff lever  511 . The main control unit  61  and the pilot pressure valve  43   x  are one example of a state switching unit that shifts the state of the slewing motor  441  from the suspended state to the standby state in response to the preparatory manipulation. Note that a mechanical mechanism that changes the state of the pilot pressure valve  43   x  according to displacement of the boarding and alighting cutoff lever  511  may be adopted instead of the main control unit  61 . 
     The hydraulic control valve  43  controls supply of the working oil to the hydraulic actuator  44  in response to the drive control signal supplied from the controller  6 . However, the hydraulic control valve  43  can operate only when the pilot pressure valve  43   x  is in the ON state to allow the pilot pressure to act on the hydraulic control valve  43 . The working oil is a pressure oil supplied from the main pump of the hydraulic pump unit  42 . 
     The hydraulic actuators  44  include the stewing motor  441  that drives the upper stewing body  12  to rotate. The slewing motor  441  is a hydraulic motor. Furthermore, the hydraulic actuators  44  also include another hydraulic motor that drives the winch device  16 . The stewing motor  441  is one example of an actuator. The upper stewing body  12  is one example of a movable part driven by the actuator. 
     The controller  6  starts the engine  41  by an engine starting manipulation performed on the manipulation device  5 . Furthermore, the controller  6  outputs a control signal to a control target such as the hydraulic control valve  43  in response to a manipulation on the manipulation device  5  or various detection results of the state detection device  45 . In addition, the controller  6  controls the display device  7 . 
     As shown in  FIG. 3 , the controller  6  includes a micro processing unit (MPU)  601 , a random access memory (RAM)  602 , a non-volatile memory  603 , a communication interface  604 , and the like. Note that the RAM  602  and the non-volatile memory  603  are computer-readable storage devices. 
     The MPU  601  is one example of a processor that executes various data processing and control by executing a program stored in the non-volatile memory  603  in advance. 
     The RAM  602  is a volatile memory that temporarily stores the program to be executed by the MPU  601  and data to be calculated or referenced by the MPU  601 . 
     The non-volatile memory  603  stores in advance the program to be executed by the MPU  601  and the data to be referenced by the MPU  601 . For example, it is considered that the non-volatile memory  603  is an electrically erasable programmable read only memory (EEPROM), a flash memory, or the like. 
     The communication interface  604  is a device that communicates with other devices such as the state detection device  45  through the vehicle-mounted network  100 . The MPU  601  acquires the detection result of the state detection device  45  through the communication interface  604 . Furthermore, the MPU  601  outputs the control signal to another device through the communication interface  604 . 
     By the MPU  601  of the controller  6  executing a predetermined control program, the controller  6  operates as the main control unit  61 , a state determination unit  62 , the stewing control unit  63 , a display control unit  64 , and the like. 
     The main control unit  61  performs processing for acquiring the detection result of the state detection device  45  through the vehicle-mounted network  100 . Furthermore, the main control unit  61  switches the pilot pressure valve  43   x  to the pilot pressure OFF state or the pilot pressure ON state in response to the manipulation on the boarding and alighting cutoff device  51 . 
     The state determination unit  62  determines various states of the crane  10  based on the detection result of the state detection device  45 . 
     The slewing control unit  63  controls the operation of the slewing motor  441  included in the hydraulic actuators  44  by controlling the hydraulic control valve  43 . The slewing control unit  63  and the hydraulic control valve  43  are one example of a drive control unit that controls the operation of the actuator. 
     The display control unit  64  generates output screen data in response to the manipulation on the manipulation input device  54 , and causes the display device  7  to display a screen according to the output screen data. Furthermore, the display control unit  64  selects the monitoring image to be displayed on the display device  7  by controlling the image switch  47 . 
     In addition, the controller  6  also operates as a winch control unit (not shown). The winch control unit controls the hydraulic motors that drive the winch devices  16 . 
     In that connection, when the operator is checking various states on the screen of the display device  7  in the cab  13  at a work site, the operator may perform various preparatory work around the upper slewing body  12  of the crane  10 . 
     In the above-described case, if the monitoring image corresponding to the monitoring area T 0  in which the worker is detected is automatically displayed on the display device  7  every time the obstacle detection device  454  detects the worker, the operation of checking information on the screen of the display device  7  by the operator may be hindered. 
     Meanwhile, if a function of automatic control of display of the monitoring image in response to the detection of the obstacle is stopped in response to the manipulation by the operator, the operator may forget to perform the manipulation of releasing stop of the automatic control function of display of the monitoring image after the checking work. 
     In the crane  10 , the controller  6  executes first monitoring control and second monitoring control to be described later. By the control, unnecessary, automatic switching of display contents of the display device  7  is avoided even if the operator does not stop the function of automatic control of display of the monitoring image. 
     [First Monitoring Control] 
     Hereinafter, one example of a procedure for the first monitoring control will be described with reference to the flowchart shown in  FIG. 6 . 
     The main control unit  61  of the controller  6  starts the first monitoring control when the engine  41  starts. When the engine  41  starts, the state of the slewing motor  441  is the suspended state, and each of the hydraulic actuators  44  including the slewing motor  441  is at a stop. 
     The first monitoring control is executed under circumstances where each of the hydraulic actuators  44  including the stewing motor  441  is at a stop. In the following description, symbols such as S 101  and S 102  represent identification symbols for a plurality of processes in the first monitoring control. 
     &lt;Process S 101 &gt; 
     In the first monitoring control, to begin with, for each of the TOF sensor units  454   a  to  454   g  of the obstacle detection device  454 , the slewing control unit  63  sets first monitoring areas T 1  that are set in advance with respect to the upper slewing body  12  as the designated area (see  FIG. 9 ). 
     In the present embodiment, by the processing of process S 101 , seven first monitoring areas T 1 , which are areas including inner portions of the seven monitoring areas T 0  (the outer peripheral monitoring areas), are set as the designated area. Furthermore, the stewing control unit  63  also treats the lower center area Th 0  as the first monitoring area T 1 . 
     The eight first monitoring areas T 1  are areas inside a circular range Tx 0  set in advance with respect to the upper slewing body  12  out of the eight monitoring areas T 0 . This circular range Tx 0  is set to overlap at least part of the eight monitoring areas T 0  in plan view. In the example shown in  FIGS. 9 and 10 , the circular range Tx 0  is a range represented by a circle having a radius determined in advance centered on a slewing center P 0  of the upper slewing body  12 . 
     The circular range Tx 0  is a range where the upper stewing body  12  passes when the upper slewing body  12  slews. That is, the first monitoring areas T 1  are areas for detecting the obstacle that is likely to come into contact with the upper slewing body  12  when the upper stewing body  12  slews. 
     In the present embodiment, the three monitoring areas T 0  of the front area Ta 0 , the front and left area Tb 0 , and the rear and right area Tg 0  are associated in advance with the left slewing direction of the upper slewing body  12 . The three first monitoring areas T 1  in these three monitoring areas T 0  are areas in which extra caution needs to be exercised about a collision accident between the upper slewing body  12  and the obstacle when the upper stewing body  12  slews in the left slewing direction. 
     Similarly, the two monitoring areas T 0  of the rear and left area Td 0  and the front and right area Te 0  are associated in advance with the right slewing direction of the upper slewing body  12 . The two first monitoring areas T 1  in these two monitoring areas T 0  are areas in which extra caution needs to be exercised about a collision accident between the upper slewing body  12  and the obstacle when the upper slewing body  12  slews in the right slewing direction. 
     In the present embodiment, the obstacle detection device  454  can detect the obstacle individually in five first monitoring areas T 1  corresponding to the two slewing directions of the upper slewing body  12 . Note that the right slewing direction and the left slewing direction are two slewing directions of the upper slewing body  12 . 
     By the processing of process S 101  being performed, in each of the TOF sensor units  454   a  to  454   g , the data processing device  4542  acquires data representing the first monitoring area T 1  from the controller  6  as data of the designated area. Furthermore, the data processing device  4542  outputs, to the controller  6 , the detection result of the position of the obstacle closest to the TOF sensor  4541  out of the obstacles detected in the first monitoring area T 1  in the visual field range by the TOF sensor  4541 . 
     Note that the motion sensor  454   h  outputs the detection result of a person in the lower center area Th 0  to the controller  6  regardless of setting of the designated area. 
     &lt;Process S 102 &gt; 
     Next, the state determination unit  62  acquires the detection result of the obstacle detection device  454  and determines whether the obstacle is detected in each of the eight first monitoring areas T 1 . 
     Then, on determination that the obstacle is detected in at least one first monitoring area T 1  out of the eight first monitoring areas T 1 , the state determination unit  62  shifts the processing to process S 103 . Meanwhile, on determination that the obstacle is not detected in any of the eight first monitoring areas T 1 , the state determination unit  62  shifts the processing to process S 109 . 
     In process S 102 , when part of the plurality of monitoring areas T 0  is set as an invalid area by the invalid area setting processing described later, the state determination unit  62  determines whether the obstacle is detected without taking into consideration the detection result of the obstacle in the invalid area. 
     &lt;Process S 103 &gt; 
     In process S 103 , the slewing control unit  63  sets a slewing interlock flag to ON and shifts the processing to process S 104 . The stewing interlock flag is a flag indicating whether to prohibit or allow the start of the slewing motor  441 . 
     When the slewing motor  441  is at a stop and the slewing manipulation device  52  receives the slewing manipulation on the slewing lever  521 , the slewing control unit  63  starts the slewing motor  441  only when the stewing interlock flag is OFF. That is, the slewing interlock flag being ON means that the start of the slewing motor  441  is prohibited, and the slewing interlock flag being OFF means that the slewing motor  441  is allowed to start. 
     The processing of process S 103  for setting the slewing interlock flag to ON is one example of slewing interlock processing for prohibiting the start of the slewing motor  441 . 
     &lt;Process S 104 &gt; 
     In process S 104 , the state determination unit  62  determines whether the state of the slewing motor  441  is the standby state or the suspended state. 
     Then, on determination that the state of the slewing motor  441  is the standby state, the state determination unit  62  shifts the processing to process S 105 , and on determination that the state of the stewing motor  441  is the suspended state, the state determination unit  62  shifts the processing to process S 112 . 
     &lt;Process S 105 &gt; 
     In process S 105 , the state determination unit  62  determines whether the position of the slewing lever  521  is the neutral position. Then, on determination that the position of the slewing lever  521  is the neutral position, the state determination unit  62  shifts the processing to process S 106 . Meanwhile, on determination that the position of the slewing lever  521  is not the neutral position, the state determination unit  62  shifts the processing to process S 107 . 
     &lt;Process S 106 &gt; 
     In process S 106 , the display control unit  64  executes first automatic image output and then shifts the processing to process S 108 . 
     The first automatic image output is processing for automatically causing the display device  7  to display the monitoring image corresponding to the first monitoring area T 1  in which the obstacle is detected in response to the detection of the obstacle in the first monitoring area T 1  by the obstacle detection device  454 . 
     The display control unit  64  performs the processing of process S 106  when the slewing interlock processing prohibits the start of the slewing motor  441  and the stewing manipulation on the slewing lever  521  is not performed. 
     In process S 106 , when the obstacle is detected in each of two or more first monitoring areas T 1  out of the plurality of first monitoring areas T 1 , the display control unit  64  causes the display device  7  to display the monitoring image corresponding to the obstacle detected at a position closest to the position of the slewing center P 0  of the upper slewing body  12  out of the obstacles detected in the two or more first monitoring areas T 1 . The position of the slewing center P 0  is one example of a predetermined reference position in the upper slewing body  12 . 
     For example, the data processing device  4542  of each of the TOF sensor units  454   a  to  454   g  may be configured to convert primary coordinate data representing the position of the obstacle with respect to the position of the TOF sensor  4541  into secondary coordinate data with respect to the position of the stewing center P 0  and to transmit the secondary coordinate data to the controller  6 . 
     In addition, the data processing device  4542  may be configured to transmit the primary coordinate data to the controller  6 , and the main control unit  61  may be configured to convert the primary coordinate data into the secondary coordinate data. 
     The display control unit  64  calculates the distance from the position of the stewing center P 0  to each obstacle based on the secondary coordinate data. 
     By the processing of process S 106 , the presence of the nearest obstacle that is likely to come into contact with the upper slewing body  12  if the upper slewing body  12  slews is promptly notified to the operator by the display of the monitoring image. 
     &lt;Process S 107 &gt; 
     In process S 107 , the display control unit  64  executes the first automatic image output in a similar manner to process S 106 , and then shifts the processing to process S 108 . 
     In a case where the stewing interlock processing prohibits the start of the slewing motor  441 , the display control unit  64  performs the processing of process S 107  of  FIG. 6  when the slewing manipulation of instructing the slewing lever  521  to drive the upper slewing body  12  is performed. The slewing manipulation is one example of the drive manipulation of instructing the actuator to operate. 
     In process S 107 , under circumstances where the obstacle is detected in each of two or more first monitoring areas T 1  out of the plurality of first monitoring areas T 1 , out of the two or more first monitoring areas T 1 , the display control unit  64  causes the display device  7  to display the monitoring image of the first monitoring area T 1  corresponding to the instruction direction of slewing the upper slewing body  12  by the slewing manipulation in preference to other monitoring images. 
     For example, when the instruction direction is a left stewing direction, the display control unit  64  causes the display device  7  to display the monitoring images of the three monitoring areas T 0  of the front area Ta 0 , the front and left area Tb 0 , and the rear and right area Tg 0  in preference to other monitoring images. 
     Similarly, when the instruction direction is a right slewing direction, the display control unit  64  causes the display device  7  to display the monitoring images of the two monitoring areas T 0  of the rear and left area Td 0  and the front and right area Te 0  in preference to other monitoring images. 
     By the processing of process S 107 , the presence of the obstacle that is likely to come into contact with the upper slewing body  12  if the upper slewing body  12  stews in the slewing direction according to the intention of the operator is promptly notified to the operator by the display of the monitoring image. 
     Note that when the obstacle is detected in each of the plurality of first monitoring areas T 1  corresponding to the instruction direction, out of the plurality of obstacles detected in the plurality of first monitoring areas T 1  corresponding to the instruction direction, the display control unit  64  causes the display device  7  to preferentially display the monitoring image corresponding to the obstacle detected at the position closest to the position of the slewing center P 0  of the upper slewing body  12 . 
     &lt;Process S 108 &gt; 
     In process S 108 , the display control unit  64  outputs a predetermined alarm corresponding to the detection of the obstacle through the display device  7  and a buzzer (not shown), and then shifts the processing to process S 102 . With this operation, the processing after process S 102  is repeated with the first monitoring areas T 1  still set as the designated area. 
     Note that the crane  10  may include a plurality of alarm devices (not shown) located in monitoring areas T 0  respectively. In this case, in process S 108 , the main control unit  61  may be configured to perform danger notification processing through the alarm device corresponding to the monitoring area T 0  in which the obstacle is detected. For example, one or both of a speaker that outputs a danger notification sound and an alarm light that emits danger notification light are adopted as the alarm devices. 
     &lt;Process S 109 &gt; 
     In process S 109 , the state determination unit  62  starts a timer that measures elapsed time from determination that the obstacle is not detected in any of the plurality of first monitoring areas T 1 . Thereafter, the state determination unit  62  shifts the processing to process S 110 . 
     &lt;Process S 110 &gt; 
     In process S 110 , the state determination unit  62  determines whether the state of the slewing motor  441  is the standby state or the suspended state. 
     Then, on determination that the state of the slewing motor  441  is the standby state, the state determination unit  62  shifts the processing to process S 111 , and on determination that the state of the slewing motor  441  is the suspended state, the state determination unit  62  shifts the processing to process S 112 . 
     &lt;Process S 111 &gt; 
     In process S 111 , the state determination unit  62  determines whether the slewing brake device  440  is in the brake ON state or the brake OFF state. 
     Then, on determination that the slewing brake device  440  is in the brake ON state, the state determination unit  62  shifts the processing to process S 112 , and on determination that the slewing brake device  440  is in the brake OFF state, the state determination unit  62  shifts the processing to process S 113 . 
     &lt;Process S 112 &gt; 
     In process S 112 , the display control unit  64  returns the image to be displayed on the display device  7  to the original image, and then shifts the processing to process S 102 . With this operation, the processing after process S 102  is repeated with the first monitoring areas T 1  still set as the designated area. 
     The original image is a image that has been displayed on the display device  7  before the display control unit  64  automatically causes the display device  7  to display the monitoring image in response to the detection of the obstacle. 
     Note that before the monitoring image is automatically displayed on the display device  7  in response to the detection of the obstacle, the display state of the image of the display device  7  at that time is maintained as it is. 
     &lt;Process S 113 &gt; 
     In process S 113 , the slewing control unit  63  starts the second monitoring control described below. When the second monitoring control is finished, the slewing control unit  63  shifts the processing to process S 101 . With this operation, the first monitoring areas T 1  are set again as the designated area (S 101 ), and then the processing after process S 102  is repeated. 
     As described above, at least when the obstacle is detected in the first monitoring area T 1  under circumstances where the slewing motor  441  is at a stop, the slewing control unit  63  performs the slewing interlock processing for prohibiting the start of the slewing motor  441  (see processes S 101  to S 103  of  FIG. 6 ). 
     By the slewing interlock processing, it is possible to avoid slewing of the upper slewing body  12  under circumstances where the worker exists in the first monitoring area T 1  near the upper slewing body  12 . 
     [Second Monitoring Control] 
     Next, one example of a procedure for the second monitoring control will be described with reference to the flowchart shown in  FIG. 7 . 
     The second monitoring control is started when the state of the slewing motor  441  is the standby state and the slewing brake device  440  is in the brake OFF state under circumstances where each of the hydraulic actuators  44  including the slewing motor  441  is at a stop. In the following description, symbols such as S 201  and S 202  represent identification symbols for a plurality of processes in the second monitoring control. 
     &lt;Process S 201 &gt; 
     In the second monitoring control, to begin with, for each of the TOF sensor units  454   a  to  454   g  of the obstacle detection device  454 , the slewing control unit  63  sets second monitoring areas T 2  that are set in advance at places remoter from the upper slewing body  12  than the first monitoring areas T 1  as the designated area (see  FIG. 10 ). 
     In the present embodiment, by the processing of process S 201 , a remaining part of the seven monitoring areas T 0  (the outer peripheral monitoring areas) excluding the seven first monitoring areas T 1 , that is, the seven second monitoring areas T 2 , which are areas including outer portions of the seven monitoring areas T 0 , are set as the designated area. These seven second monitoring areas T 2  are areas corresponding to the seven TOF sensor units  454   a  to  454   g.    
     The seven second monitoring areas T 2  are areas outside the circular range Tx 0  set with respect to the upper slewing body  12  out of the eight monitoring areas T 0 . 
     By the processing of process S 201  being performed, in each of the TOF sensor units  454   a  to  454   g , the data processing device  4542  acquires data representing the second monitoring areas T 2  from the controller  6  as data of the designated area. Furthermore, the data processing device  4542  outputs, to the controller  6 , the detection result of the position of the obstacle closest to the TOF sensor  4541  out of the obstacles detected in the second monitoring areas T 2  in the visual field range by the TOF sensor  4541 . 
     In the second monitoring control, the processing corresponding to the detection of the obstacle by the motion sensor  454   h  is not particularly performed. 
     &lt;Process S 202 &gt; 
     Next, the state determination unit  62  acquires the detection result of the obstacle detection device  454  and determines whether the obstacle is detected in each of the seven second monitoring areas T 2 . 
     Then, on determination that the obstacle is detected in at least one second monitoring area T 2  out of the seven second monitoring areas T 2 , the state determination unit  62  shifts the processing to process S 203 . Meanwhile, on determination that the obstacle is not detected in any of the seven second monitoring areas T 2 , the state determination unit  62  shifts the processing to process S 206 . 
     In process S 202 , when part of the plurality of monitoring areas T 0  is set as an invalid area by the invalid area setting processing described above, the state determination unit  62  determines whether the obstacle is detected without taking into consideration the detection result of the obstacle in the invalid area. The invalid area setting processing will be described later. 
     &lt;Process S 203 &gt; 
     In process S 203 , the display control unit  64  executes second automatic image output and then shifts the processing to process S 204 . 
     The second automatic image output is processing for automatically causing the display device  7  to display the monitoring image corresponding to the second monitoring area T 2  in which the obstacle is detected in response to the detection of the obstacle in the second monitoring area T 2  by the obstacle detection device  454 . 
     In process S 203 , when the obstacle is detected in each of two or more second monitoring areas T 2  out of the plurality of second monitoring areas T 2 , the display control unit  64  causes the display device  7  to display the monitoring image corresponding to the obstacle detected at a position closest to the position of the slewing center P 0  of the upper slewing body  12  out of the obstacles detected in the two or more second monitoring areas T 2 . 
     By the processing of process S 203 , the presence of the obstacle that may enter the first monitoring area T 1  from the second monitoring area T 2  is promptly notified to the operator by the display of the monitoring image. 
     &lt;Process S 204 &gt; 
     In process S 204 , the slewing control unit  63  sets operation limitation of the slewing motor  441  and shifts the processing to process S 205 . The operation limitation setting is processing for limiting the operation of the slewing motor  441  in response to the manipulation of slewing instruction on the slewing manipulation device  52  (the slewing manipulation) after the start of the stewing motor  441  is allowed. The operation limitation is a limitation other than prohibition of starting the slewing motor  441 . 
     For example, in process S 204 , the slewing control unit  63  may be configured to set the operation limitation by performing speed limiting processing, which is processing for limiting a rotation speed of the slewing motor  441 . Specifically, the slewing control unit  63  sets the operation limitation by setting a speed limit flag to ON in the speed limiting processing. When the speed limit flag is set to ON, the slewing control unit  63  operates the stewing motor  441  in response to a manipulation of a stewing instruction (the slewing manipulation) on the slewing manipulation device  52  within a range that does not exceed the predetermined speed limit. 
     Note that the limitation of the rotation speed of the slewing motor  441  may be directly implemented by feedback of a measured value of the operating speed of the stewing motor  441  or the upper slewing body  12 . In addition, the limitation of the rotation speed of the stewing motor  441  may be indirectly implemented by limiting the opening degree of the hydraulic control valve  43  corresponding to the slewing motor  441  or limiting the hydraulic pressure acting on the slewing motor  441 . 
     In addition, the slewing control unit  63  may be configured to set the operation limitation by performing direction limiting processing in process S 204 . The direction limiting processing is processing for prohibiting the operation of the slewing motor  441  that stews the upper slewing body  12  in the slewing direction corresponding to the second monitoring area T 2  in which the obstacle is detected, while for allowing the operation of the slewing motor  441  that slews the upper stewing body  12  in the slewing direction corresponding to the second monitoring area T 2  in which the obstacle is not detected. Specifically, the control is as follows. 
     As described above, out of the eight monitoring areas T 0 , the three monitoring areas T 0  of the front area Ta 0 , the front and left area Tb 0 , and the rear and right area Tg 0  are associated in advance with the left slewing direction, which is one of the two slewing directions of the upper slewing body  12 , and the two monitoring areas T 0  of the rear and left area Td 0  and the front and right area Te 0  are associated in advance with the right slewing direction, which is the other of the two slewing directions. Therefore, the three second monitoring areas T 2  corresponding to the three monitoring areas T 0  are set to correspond to the left slewing direction, and the two second monitoring areas T 2  corresponding to the two monitoring areas T 0  are set to correspond to the right stewing direction. For example, when the obstacle is detected in at least one of the three second monitoring areas T 2  and the obstacle is not detected in either of the two second monitoring areas T 2 , the slewing control unit  63  prohibits the operation of the slewing motor  441  that slews the upper slewing body  12  in the left slewing direction, while allows the operation of the slewing motor  441  that slews the upper slewing body  12  in the right slewing direction. 
     Furthermore, the stewing control unit  63  may perform both the speed limiting processing and the direction limiting processing. In this case, the slewing control unit  63  limits the rotation speed of the slewing motor  441  when the upper stewing body  12  is slewed in the allowed slewing direction. 
     &lt;Process S 205 &gt; 
     In process S 205 , the display control unit  64  outputs a predetermined alarm corresponding to the detection of the obstacle through the display device  7  and a buzzer (not shown), and then shifts the processing to process S 208 . 
     Note that when the crane  10  includes the plurality of alarm devices (for example, the speaker, the alarm light, and the like), in process S 205 , the main control unit  61  may be configured to perform the danger notification processing through the alarm device corresponding to the monitoring area T 0  in which the obstacle is detected out of the plurality of alarm devices. 
     &lt;Process S 206 &gt; 
     Meanwhile, in process S 206 , in a similar manner to process S 112 , the display control unit  64  returns the image to be displayed on the display device  7  to the original image, and then shifts the processing to process S 207 . 
     Note that before the monitoring image is automatically displayed on the display device  7  in response to the detection of the obstacle, the display state of the image of the display device  7  at that time is maintained as it is. 
     &lt;Process S 207 &gt; 
     In process S 207 , the slewing control unit  63  releases the operation limitation of the slewing motor  441  and shifts the processing to process S 208 . 
     &lt;Process S 208 &gt; 
     In process S 208 , the state determination unit  62  determines whether the stewing lever  521  exists at the neutral position. 
     Then, on determination that the slewing lever  521  exists at the neutral position, the state determination unit  62  shifts the processing to process S 209 . Meanwhile, on determination that the slewing lever  521  does not exist at the neutral position, the state determination unit  62  shifts the processing to process S 212 . 
     &lt;Process S 209 &gt; 
     In process S 209 , the slewing control unit  63  sets the stewing interlock flag to OFF and shifts the processing to process S 210 . 
     When the slewing manipulation device  52  receives the slewing manipulation on the slewing lever  521  under circumstances where the slewing motor  441  is at a stop and the slewing interlock flag is OFF, the slewing control unit  63  starts the slewing motor  441 . 
     &lt;Process S 210 &gt; 
     In process S 210 , the state determination unit  62  determines whether the stewing motor  441  is at a stop. Then, on determination that the stewing motor  441  is at a stop, the state determination unit  62  shifts the processing to process S 211 . Meanwhile, on determination that the stewing motor  441  is not at a stop, the state determination unit  62  shifts the processing to process S 213 . 
     &lt;Process S 211 &gt; 
     In process S 211 , the state determination unit  62  determines whether a predetermined allowed time has elapsed from determination that the obstacle is not detected in any of the plurality of first monitoring areas T 1 . 
     On determination that the allowed time has elapsed, the state determination unit  62  finishes the second monitoring control. With this operation, the first monitoring control shown in  FIG. 6  is executed again. 
     Meanwhile, on determination that the allowed time has not elapsed, the state determination unit  62  shifts the processing to process S 202 . With this operation, the processing after process S 202  is repeated with the second monitoring areas T 2  still set as the designated area. 
     &lt;Process S 212 &gt; 
     In process S 212 , the display control unit  64  outputs a neutral notification, which is a notification for prompting the operator to return the stewing lever  521  to the neutral position, through the display device  7  and the buzzer (not shown), and shifts the processing to process S 202 . 
     The processing of processes S 208 , S 209 , and S 212  is, for the slewing motor  441 , processing for preventing the slewing motor  441  from suddenly starting at a timing delayed from the manipulation of the slewing lever  521  by the release of the interlock. 
     &lt;Process S 213 &gt; 
     The processing of process S 213  is performed after the stewing motor  441  starts. In process S 213 , the state determination unit  62  stands by while determining whether a predetermined resumption condition is satisfied. 
     The resumption condition is a condition for resuming the first monitoring control after the slewing motor  441  starts, and includes as an essential condition that the stewing motor  441  has stopped. For example, the resumption condition may include a brake ON condition in which the stewing motor  441  has stopped and the stewing brake device  440  has changed to the brake ON state. 
     In addition, the resumption condition may include a stop continuation condition that the state in which the slewing motor  441  has stopped continues for a predetermined time. The resumption condition may include at least one of the brake ON condition and the stop continuation condition. 
     In addition, the resumption condition may include a suspend shift condition in which the state of the slewing motor  441  has shifted from the standby state to the suspended state. The resumption condition may include at least one of the brake ON condition, the stop continuation condition, and the suspend shift condition. 
     Then, on determination that the resumption condition is satisfied, the state determination unit  62  shifts the processing to process S 214 . 
     &lt;Process S 214 &gt; 
     In process S 214 , the stewing control unit  63  releases the operation limitation of the stewing motor  441  and finishes the second monitoring control. With this operation, the first monitoring control shown in  FIG. 6  is executed again. 
     As described above, when the stewing motor  441  is at a stop, the stewing control unit  63  of the controller  6  sets one or more first monitoring areas T 1  set with respect to the upper stewing body  12  as the designated area, and then controls, depending on whether the obstacle is detected in the one or more first monitoring areas T 1 , whether to prohibit or allow the start of the stewing motor  441  in response to the stewing manipulation on the stewing lever  521  (see processes S 101  to S 103  of  FIG. 6  and process S 209  of  FIG. 7 ). The stewing control unit  63  that executes this control is one example of a first stewing control unit. 
     Furthermore, the stewing control unit  63  sets one or more second monitoring areas T 2  that are set at places remoter from the upper stewing body  12  than the first monitoring areas T 1  as the designated area, and then controls, depending on whether the obstacle is detected in the one or more second monitoring areas T 2 , whether to limit the operation of the stewing motor  441  in response to the stewing manipulation on the stewing lever  521  after the start of the stewing motor  441  is allowed (processes S 201 , S 202 , S 204 , S 207 , and S 209  of  FIG. 7 ). The stewing control unit  63  that executes this control is one example of a second stewing control unit. That is, the stewing control unit  63  includes the first stewing control unit and the second stewing control unit. 
     That is, in order to achieve both safety and work efficiency, the stewing control unit  63  of the controller  6  individually takes measures in response to the detection of the obstacle in each of the first monitoring areas T 1  near the upper stewing body  12  and the second monitoring areas T 2  therearound. 
     Specifically, safety check is sufficiently performed in the first monitoring areas T 1  around the upper stewing body  12  by the first monitoring control of the stewing control unit  63  before the upper stewing body  12  starts. 
     Furthermore, even in a case where the obstacle exists n the monitoring area T 0 , the start of the upper stewing body  12  is not prohibited by the second monitoring control of the stewing control unit  63  even when the obstacle exists in the second monitoring area T 2  in which the obstacle does not come into contact with the upper slewing body  12 . Therefore, deterioration of the work efficiency of the crane  10  is avoided. 
     However, when the obstacle exists in the second monitoring area T 2  in which the obstacle does not come into contact with the upper stewing body  12 , the hoist load  9  or the boom  21  that supports the hoisting rope  32  may come into contact with the obstacle. In this case, the stewing control unit  63  limits the operation of the stewing motor  441  as a measure different from the prohibition of start of the upper stewing body  12  in the second monitoring control (see process S 204  of  FIG. 7 ). With this operation, safety is ensured while a decrease in the work efficiency is avoided. 
     In addition, each of the TOF sensor units  454   a  to  454   g  detects the obstacle individually in the first monitoring area T 1  and the second monitoring area T 2  by changing the setting of the designated area. With this operation, the crane  10  can take appropriate measures in response to the detection of the obstacle in each of the first monitoring area T 1  and the second monitoring area T 2  therearound by using as few TOF sensors  4541  as possible. 
     In addition, when the slewing motor  441  starts with the operation of the slewing motor  441  limited, the stewing control unit  63  releases the limitation on the operation of the slewing motor  441  on condition that the slewing motor  441  stops after the slewing motor  441  starts (see processes S 213  and S 214  of  FIG. 7 ). Therefore, acceleration of the upper slewing body  12  against the intention of the operator is avoided. 
     The slewing control unit  63  that performs processing of processes S 213  and S 214  is one example of the second stewing control unit. Note that in the example shown in  FIG. 7 , the resumption condition also serves as a condition for releasing the limitation on the operation of the slewing motor  441 . However, the condition for releasing the limitation on the operation of the slewing motor  441  may be determined separately from the resumption condition. 
     In addition, on determination that the state of the slewing motor  441  is the standby state, the display control unit  64  executes the first automatic image output or the second automatic image output that is processing for automatically causing the display device  7  to display the monitoring image corresponding to the monitoring area T 0  in which the obstacle is detected (see processes S 104  to S 107 , S 110 , and S 113  of  FIG. 6  and processes S 202  and S 203  of  FIG. 7 ). These processes are one example of the second process of causing the display device  7  to selectively display one monitoring image out of the plurality of monitoring images of the plurality of monitoring areas according to the determination result of the state of the actuator. The display control unit  64  causes the display device  7  to selectively display one monitoring image out of the plurality of monitoring images of the plurality of monitoring areas according to the determination result of the state of the actuator. However, this second process may cause the display device  7  to selectively display two or more monitoring images out of the plurality of monitoring images of the plurality of monitoring areas according to the determination result of the state of the actuator. That is, the display control unit  64  may cause the display device  7  to selectively display two or more monitoring images out of the plurality of monitoring images of the plurality of monitoring areas according to the determination result of the state of the actuator. 
     Meanwhile, on determination that the state of the stewing motor  441  is the suspended state, the display control unit  64  does not perform the first automatic image output and the second automatic image output (see processes S 104 , S 110 , and S 112  of  FIG. 6 ). These processes are one example of the second process. 
     Generally, under circumstances where the state of the slewing motor  441  is maintained in the suspended state, the worker performs various preparatory work around the upper slewing body  12  of the crane  10 . 
     Therefore, in the crane  10 , when the preparatory work is performed, the monitoring image is not automatically displayed on the display device  7  every time the obstacle detection device  454  detects the worker. Therefore, the work of checking information on the screen of the display device  7  by the operator is not hindered. That is, unnecessary, automatic switching of display contents of the display device  7  is avoided even if the operator does not stop functions of automatic control of image display. 
     Meanwhile, when the state of the slewing motor  441  is the standby state, the first automatic image output or the second automatic image output is executed in response to the detection of the obstacle without the need for the switching manipulation of the image control by the operator. 
     In addition, when the slewing motor  441  is at a stop and the slewing brake device  440  is in the brake ON state, the display control unit  64  executes the first automatic image output (see processes S 111 , S 102 , S 106 , and S 107  of  FIG. 6 ). The first automatic image output is automatic image output in response to the detection of the obstacle in the first monitoring area T 1 . 
     Meanwhile, when the slewing motor  441  is at a stop and the slewing brake device  440  is in the brake OFF state under circumstances where the start of the slewing motor  441  is not prohibited, the display control unit  64  executes the second automatic image output without executing the first automatic image output (see processes S 209 , S 210 , S 211 , S 202 , and S 203  of  FIG. 7 ). The second automatic image output is automatic image output in response to the detection of the obstacle in the second monitoring area T 2 . 
     Generally, when the operator finishes checking the situation around the upper slewing body  12  and then determines to start slewing the upper slewing body  12 , the operator performs a manipulation of switching the slewing brake device  440  from the brake ON state to the brake OFF state. 
     Therefore, when the operator is checking the situation around the upper stewing body  12 , the display control unit  64  appropriately assists the safety checking work of the operator by executing the first automatic image output. 
     Meanwhile, from the time when the operator determines to start slewing the upper slewing body  12  until the slewing of the upper slewing body  12  starts, the display control unit  64  executes the second automatic image output. With this operation, the display control unit  64  appropriately assists the safety checking work of the second monitoring area T 2  to be performed next by the operator without requiring the switching manipulation by the operator. 
     [Invalid Area Setting Processing] 
     As shown in  FIG. 2 , the controller  6  may further include an invalid area setting unit  65 . In this case, the MPU  601  of the controller  6  executes a predetermined program, whereby the invalid area setting unit  65  of the controller  6  performs invalid area setting processing. 
     Hereinafter, with reference to the flowchart shown in  FIG. 8 , one example of the procedure for the invalid area setting processing performed by the invalid area setting unit  65  will be described. 
     The invalid area setting processing is processing for setting an area where it is determined that the obstacle is not detected regardless of the detection result of the obstacle detection device  454 . 
     The invalid area setting unit  65  performs the invalid area setting processing when the engine  41  is operating and the slewing motor  441  is at a stop. In the following description, symbols such as S 301  and S 302  represent identification symbols for a plurality of processes in the invalid area setting processing. 
     &lt;Process S 301 &gt; 
     In the invalid area setting processing, the invalid area setting unit  65  determines whether the display device  7  is displaying a notable image, which is the monitoring image of the monitoring area T 0  in which the obstacle is detected. 
     Then, on determination that the display device  7  is displaying the notable image, the invalid area setting unit  65  shifts the processing to process S 302 . Meanwhile, on determination that the display device  7  is not displaying the notable image, the invalid area setting unit  65  shifts the processing to process S 304 . 
     &lt;Process S 302 &gt; 
     In process S 302 , under circumstances where the notable image is displayed on the display device  7 , the invalid area setting unit  65  determines whether a predetermined invalid setting manipulation on the manipulation input device  54  is detected. 
     Then, when the invalid setting manipulation on the manipulation input device  54  is detected, the invalid area setting unit  65  shifts the processing to process S 303 , and when the invalid setting manipulation is not detected, the invalid area setting unit  65  shifts the processing to process S 304 . 
     &lt;Process S 303 &gt; 
     In process S 303 , the invalid area setting unit  65  sets the invalid area including the position of the obstacle detected in the monitoring area T 0  corresponding to the notable image. Thereafter, the invalid area setting unit  65  shifts the processing to process S 301 . 
     For example, the invalid area setting unit  65  may be configured to set an area of a part of a range of a predetermined distance from the position of the obstacle or the entire range as the invalid area in the first monitoring area T 1  or the second monitoring area T 2  corresponding to the notable image. 
     In addition, the invalid area setting unit  65  may be configured to set the entire first monitoring area T 1  or second monitoring area T 2  corresponding to the notable image as the invalid area. 
     As described above, the invalid area is excluded from a target of determining whether the obstacle is detected (see process S 102  of  FIG. 6  and process S 202  of  FIG. 7 ). 
     Therefore, when the invalid area is set, the slewing control unit  63  does not prohibit the start of the slewing motor  441  or limit the operation of the slewing motor  441  in response to the detection of the obstacle in the invalid area. That is, the slewing control unit  63  is configured not to execute control for prohibiting the start of the slewing motor  441  in response to the detection of the obstacle in the invalid area when the invalid area is set, and is configured not to execute control for limiting the operation of the slewing motor in response to the detection of the obstacle in the invalid area. 
     Similarly, when the invalid area is set, the display control unit  64  does not execute the first automatic image output or the second automatic image output in response to the detection of the obstacle in the invalid area. That is, the display control unit  64  is configured not to execute the first automatic image output or the second automatic image output in response to the detection of the obstacle in the invalid area when the invalid area is set. 
     &lt;Process S 304 &gt; 
     In process S 304 , the invalid area setting unit  65  determines whether a predetermined invalidation release condition is satisfied. Then, on determination that the invalidation release condition is satisfied, the invalid area setting unit  65  shifts the processing to process S 305 . Meanwhile, on determination that the invalidation release condition is not satisfied, the invalid area setting unit  65  repeats the processing from process S 301 . 
     The invalidation release condition is a condition for releasing the setting of the invalid area. For example, the invalidation release condition may be the same condition as the suspend shift condition in the resumption condition. In addition, the invalidation release condition may include at least one of the brake ON condition and the suspend shift condition in the resumption condition. 
     &lt;Process S 305 &gt; 
     In process S 305 , the invalid area setting unit  65  releases the setting of the invalid area, and then repeats the processing from process S 301 . 
     As described above, the invalid area setting unit  65  performs the processing of process S 302  and process S 303  under circumstances where the obstacle is detected in the first monitoring area T 1  or the second monitoring area T 2  when the slewing motor  441  is at a stop, and the notable image, which is the monitoring image of the area where the obstacle is detected, is displayed on the display device  7 . 
     The obstacle detected in the first monitoring area T 1  or the second monitoring area T 2  is the obstacle detected in one of the designated areas on the TOF sensor units  454   a  to  454   g  or in the lower center area Th 0 . 
     In process S 302  and process S 303 , when the predetermined invalid setting manipulation is detected, the invalid area setting unit  65  sets the invalid area including the position of the obstacle detected in the first monitoring area T 1  or the second monitoring area T 2  corresponding to the notable image displayed on the display device  7 . 
     Therefore, when a thing that does not cause any particular problem in operating the crane  10  is detected as the obstacle, it is possible to avoid deterioration of the work efficiency of the crane  10  by setting the invalid area. 
     In addition, since the invalid area can be set only when the operator can check the image, safety is also ensured. 
     Furthermore, the invalid area setting unit  65  automatically releases the setting of the invalid area when the predetermined invalidation release condition is satisfied (see process S 305  of  FIG. 8 ). With this operation, unnecessary maintenance of the setting of the invalid area is avoided, and safety is ensured. 
     First Application Example 
     Hereinafter, a first application example of the crane  10  will be described. In addition to the configuration of the crane  10 , the crane according to this application example further includes a motion sensor and a camera corresponding to a first winch monitoring area, and a motion sensor and a camera corresponding to a second winch monitoring area. 
     The first winch monitoring area is an area including the first winch device  161  and surroundings thereof, and the second winch monitoring area is an area including the second winch device  162  and surroundings thereof. 
     In this application example, the state determination unit  62  also makes determination similar to determination of the suspended state and the standby state about the slewing motor  441  on the hydraulic motor of each of the first winch device  161  and the second winch device  162 . 
     Furthermore, on determination that the state of the hydraulic motor corresponding to the first winch device  161  or the second winch device  162  is the standby state, the display control unit  64  in this application example executes automatic image output to automatically cause the display device  7  to display the monitoring image corresponding to the first winch monitoring area or the second winch monitoring area in which the obstacle is detected. 
     Meanwhile, on determination that the state of the hydraulic motor corresponding to the first winch device  161  or the second winch device  162  is the suspended state, the display control unit  64  in this application example does not execute the automatic image output. 
     When this application example is adopted, effects obtained in the monitoring around the upper slewing body  12  are similarly obtained in the monitoring around the first winch device  161  or the second winch device  162 . 
     Second Application Example 
     Hereinafter, a second application example of the crane  10  will be described. The crane according to this application example has a configuration in which the seven TOF sensor units  454   a  to  454   g  in the crane  10  are replaced with a stereo camera device that measures the three-dimensional position of the obstacle. 
     The stereo camera device includes one pair of cameras that captures the monitoring area T 0  from different directions, and an image processing device that calculates the three-dimensional position of an object (moving object or stationary object) by image processing on one pair of captured images obtained by the one pair of cameras. 
     When the calculated three-dimensional position is within the designated area, the image processing device outputs the three-dimensional position as the position of the obstacle to the controller  6 . 
     In this application example, one of the one pair of cameras in the stereo camera device may be configured to also serve as the camera  46  that captures the monitoring image. 
     Third Application Example 
     Hereinafter, a third application example of the crane  10  will be described. The crane according to this application example has a configuration in which the hydraulic pump unit  42 , the pilot pressure valve  43   x , and the hydraulic actuator  44  in the crane  10  are replaced with a generator, a power supply circuit, a power supply cutoff circuit, and an electric actuator, respectively. In this application example, the slewing motor  441  is an electric motor. 
     The generator generates electric power by being driven by the engine  41 , and supplies the electric power to the power supply circuit and the power supply cutoff circuit. 
     The slewing control unit  63  in this application example controls power supply from the power supply circuit to the electric motor such as the slewing motor  441  in response to the slewing manipulation on the slewing manipulation device  52 . The power supply cutoff circuit switches from one of a cutoff state for cutting off a power supply line from the power supply circuit to the slewing motor  441  and a connection state for connecting the power supply line to the other in response to the control by the main control unit  61 . 
     The main control unit  61  switches the power supply cutoff circuit from the connection state to the cutoff state in response to the cutoff manipulation on the boarding and alighting cutoff lever  511 , and switches the power supply cutoff circuit from the cutoff state to the connection state in response to the connection manipulation on the boarding and alighting cutoff lever  511 . 
     In this application example, the main control unit  61  and the power supply cutoff circuit are one example of a state switching unit that shifts the state of the slewing motor  441  from the suspended state to the standby state in response to the preparatory manipulation on the boarding and alighting cutoff lever  511 . Note that a mechanical mechanism that changes the state of the power supply cutoff circuit according to displacement of the boarding and alighting cutoff lever  511  may be adopted instead of the main control unit  61 . 
     Note that in the embodiment and the application example thereof, the work machine is a crane, but the work machine may be another work machine such as a hydraulic excavator. 
     In addition, in the embodiment and the application example thereof, the upper slewing body  12  constitutes the movable part in the present invention, but is not limited to such an aspect. The movable part may include parts of the upper slewing body  12  excluding, for example, at least one of the cab  13 , the gantry  15 , the winch device  16 , and the counterweight  17 . In addition, the movable part may be another part other than the upper slewing body  12 .