Construction equipment control system

Abstract: A control system, comprising a rotary laser irradiating system (1) emitting a laser beam and forming a laser beam reference plane. The rotary laser irradiating system tilts the laser beam reference plane. The control system also includes a level sensor (7) installed on a ground levelling tool (5a) photodetection of the laser beam (4) to give an indication of a height of the ground levelling tool (5a). A GPS (global positioning system) receiving system (80) is provided for detecting a position of the construction equipment (2). A control device is provided for controlling the gradient of the laser beam reference plane formed by the rotary laser irradiating system (1) based on the detection result of the position of the construction equipment (1) by the GPS receiving system (80). Using this system, a ground levelling operation for a horizontal, an inclined and a curved surface can be performed by measuring the position of the construction equipment (2) at real time.

Description: The present invention relates to a construction equipment control system for use in civil engineering work such as ground levelling, and in particular, to a construction equipment control system utilizing a laser reference plane formed by rotary irradiation of a laser beam in order to control height during a ground levelling operation. When a ground levelling operation is performed for construction work such as the development of housing areas or roads or pavements using construction equipment for ground levelling, e.g. a grader, bulldozer, etc., it is necessary to have a reference for the height of the ground levelling. In recent years, in order to determine such a height, which serves as a reference in the ground levelling operation, a system using a laser beam has been developed. In one such system there is a control system for construction equipment provided with a rotary laser irradiating system, such as for example disclosed in EP-A-0 727 642. Fig. 6 shows a case where the control system for construction equipment is adopted for a bulldozer. In Fig. 6, reference numeral 1 represents a rotary laser irradiating system, and 2 a bulldozer, and the rotary laser irradiating system 1 is installed on a tripod 3 at a predetermined position in a housing area under development. The rotary laser irradiating system 1 irradiates the laser beam 4 in a horizontal direction and rotates it and to form a reference plane. The bulldozer 2 has a blade 5, which is supported in such a manner that it can be moved up or down, and a pole 6 is erected on the blade 5. A level sensor 7 is mounted on the pole 6. The level sensor 7 receives the laser beam 4 from the rotary laser irradiating system 1 and detects a photodetecting position. The bulldozer 2 is provided with a control device (not shown) which detects the height of the blade 5 based on a photodetection signal from the level sensor 7, and controls the height of the blade 5 based on the result of the detection. As described above, a horizontal reference plane is formed by the laser beam, and it is possible to perform ground levelling and to form a horizontal surface by keeping a distance between the horizontal reference plane and a blade edge 5a of the blade 5. By varying the distance with respect to the blade edge 5a, it is possible to change the height of the ground surface to be levelled. Ground levelling is performed not only to level the ground to a horizontal surface. In many cases, it is necessary to perform ground levelling to form an inclined surface. For example, when constructing a housing area, it is necessary to maintain a gradient suitable for water drainage. When paving a road, it is necessary to keep a gradient suitable for the specific topography and for water drainage. In a conventional type construction equipment control system, it has been practice to perform ground levelling to produce a flat plane at first and then to form an inclined ground surface with a predetermined gradient based on the result of a surveying operation. Using the conventional construction equipment control system described above, it is possible to perform ground levelling and produce a horizontal ground surface without requiring the skill of an experienced operator. However, forming a gradient on the ground surface being levelled is difficult work and requires a high level of skill. The end result of such levelling to form an inclined ground surface depends much on the skill of the operator, and so the progress of the work varies according to the skill of each operator. In addition, problems arise in the finished ground surface and process control. Document WO 97/01005 discloses a construction equipment control system for controlling the position of a ground levelling tool movably connected to a construction machine, e.g. a bulldozer, and for maintaining the tool at a preselected level of ground relative to a geographical surface. The control system includes a GPS receiver system including a base reference station, two receivers being mounted on the construction machine and the tool to determine their position. A processor calculates the actual surface gradient based on the received position signals and the control system provides an control signal in response to a difference between the actual and a preselected desired surface gradient. The control system optionally includes a laser irradiating system adapted to deliver a laser beam defining a horizontal plane at a predetermined elevation in order to provide an additional and accurate elevation coordinate position. Such a control system is designed for ground levelling of inclined surfaces. It is an object of the present invention to provide an alternative construction equipment control system, adapted to be used for performing ground levelling including the levelling of inclined ground surfaces, easily and efficiently without being influenced by the skill and experience of the operator. To attain the above object, the construction equipment control system according to the present invention comprises a rotary laser irradiating system for forming a laser beam reference plane using the laser beam and being capable of tilting the laser beam reference plane, a level sensor installed on a ground levelling tool of construction equipment and for performing photodetection of the laser beam to give instruction on a height of the ground levelling tool, a GPS receiving system for detecting a position of the construction equipment, and a control device for controlling a gradient of the laser beam reference plane formed by the rotary laser irradiating system based on the detection result of the position of the construction equipment by the GPS receiving system. Also, in the construction equipment control system according to the present invention, the control device comprises a storage unit for storing at least working data, and an arithmetic unit for calculating the position of the construction equipment based on the received result of the GPS receiving system, and the rotary laser irradiating system is controlled according to the calculated position of the construction equipment and the working data. Further, in the construction equipment control system according to the present invention, the rotary laser irradiating system forms the laser beam reference plane by performing reciprocal scanning toward the level sensor. In the construction equipment control system according to the present invention, the GPS receiving system has a first GPS receiver and a second GPS receiver, and the first GPS receiver is installed on the construction equipment, and the second GPS receiver is mounted at a known point. Also, the construction equipment control system according to the present invention further comprises another GPS receiving system for detecting a position of the rotary laser irradiating system. Further, in the construction equipment control system according to the present invention, the rotary laser irradiating system forms the reference plane by irradiating the laser beam only within the photodetection range of the level sensor. In the construction equipment control system according to the present invention, the direction of the rotary laser irradiating system is aligned with the level sensor, and the control device is initialized by said alignment. Further, in the construction equipment control system according to the present invention, the rotary laser irradiating system comprises a photodetection unit, the photodetection unit detects a reflected laser beam from the level sensor, the control device aligns the direction of the rotary laser irradiating system with the level sensor based on the result of the detection by the photodetection unit, and the control device is initialized by said alignment. A control system in which the invention is embodied will now be described by way of example only and with reference to the accompanying drawings, of which Fig. 1 is a side view of control system in which the present invention is embodied; Fig. 2 is a cross-sectional view of a rotary laser irradiating system of the system of Figure 1; Fig. 3 is a block diagram of the rotary irradiating laser system of Figure 2; Fig. 4 is a perspective view of a level sensor used together with the rotary laser irradiating system; Fig. 5 is a block diagram of a control system in which the present invention is embodied; and Fig. 6 is a drawing showing a conventional system. In Figs. 1 and 6 like components are referred to using the same symbol. The present invention provides a control system for construction equipment, such as a bulldozer, by combining a rotary laser irradiating system capable of forming a tilted reference plane and a global positioning system (GPS). A rotary laser irradiating system 1 comprises a tilting mechanism for tilting the direction of projection of the laser beam 4 and a control unit for controlling the tilting mechanism. Thus, it is possible to tilt the direction of projection of the laser beam 4, and a tilted reference plane can be formed by the laser beam 4. Further, a radio receiver 10 is provided on the rotary laser irradiating system 1, and receiving data of the radio receiver 10 is sent to a control device 11 that is connected to the rotary laser irradiating system 1. Now, a description will be given of the rotary laser irradiating system 1, referring to Fig. 2 and Fig. 3. A rotary laser irradiating system main unit 20 is installed on a tripod 3 via a levelling unit 21 which is arranged at a lower end of the unit 20. Further, the rotary laser irradiating system main unit 20 primarily comprises a light emitter 23 for emitting the laser beam 4, a rotator 24 for performing rotary irradiation of the laser beam 4 within a reference plane, a rotating unit 22 for rotating the light emitter 23 around a vertical axis, a tilt setting unit 25 for tilting the light emitter 23 around a horizontal axis and for setting the tilt of the reference plane formed by the laser beam 4, and a tilt detecting unit 26 for detecting a tilt angle, a photodetection unit 27 for detecting light reflected from the level sensor 7, and the levelling unit 21 for performing levelling of the rotary laser irradiating system main unit 20. On the top surface of the rotary laser irradiating system main unit 20, a collimator 28 is arranged. Using this collimator 28, it is possible to set roughly the direction of the rotary laser irradiating system main unit 20 with respect to the level sensor 7. On the upper portion of the rotary laser irradiating system main unit 20, there is provided a photodetection window 34, through which the laser beam 4 from the rotator 24 is irradiated. A reflection laser beam 4' reflected by the level sensor 7 enters through the photodetection window 34 and is received by the photodetection unit 27 disposed inside the rotary laser irradiating system main unit 20. At the bottom of a casing 38 of the rotary laser irradiating system main unit 20, a main unit frame 30 is rotably arranged around the vertical axis via a vertical axis unit 29, and a rotating unit gear 31 is mounted concentrically with the vertical axis unit 29, and a rotating unit encoder 32 is also provided. A rotating unit motor 33 is provided at a position closer to the casing 38, and an output shaft of the rotating unit motor 33 is engaged with the rotating unit gear 31. When the rotating unit motor 33 is driven, the main unit frame 30 is rotated via the rotating unit gear 31. A rotation angle is detected by the rotating unit encoder 32, and the result of the detection is inputted to a control unit (CPU) 54. At the bottom of the casing 38, the levelling unit 21 is arranged. The levelling unit 21 comprises a fixed baseplate 39 to be fixed on the tripod 3 and levelling screws 40 provided between the fixed baseplate 39 and the bottom of the casing 38. Three levelling screws 40 are provided, each positioned at a vertex of a triangle. The upper end of each of the levelling screws is engaged with the casing 38, and the lower end is rotably fitted to the fixed baseplate 39. The levelling screws 40 are connected to a levelling motor 42 via a gear train 41. When the levelling screws 40 are rotated by the levelling motor 42 via the gear train 41, a gap between the casing 38 and the fixed baseplate 39 is varied, and the rotary laser irradiating system main unit 20 can be tilted in any direction as desired. Tilting of the rotary laser irradiating system main unit 20 is detected by tilt sensors 44 and 45 provided on the main unit frame 30 and the levelling operation is performed by feedback of the results of the detection by the tilt sensors 44 and 45 to the driving of the levelling motor 42. One of the three levelling screws 40 may not be provided and this one may be used merely as a tiltable supporting point. The light emitter 23 is rotably mounted on the main unit frame 30 via a horizontal tilting shaft 35, and a tilting motor 36 is arranged on the main unit frame 30. The tilting motor 36 and the tilting shaft 35 are connected with each other via a gear train 37. On the tilting shaft 35, a tilt detecting unit 26 for detecting the tilt angle of the light emitter 23 is mounted. The tilt detecting unit 26 comprises an encoder, for example. When the tilting motor 36 is driven, the light emitter 23 can be tilted via the gear train 37, and the tilt angle is detected by the tilt detecting unit 26. On the upper end of the light emitter 23, the rotator 24 is rotably mounted. A scanning gear 16 is disposed on the rotator 24 and is engaged with a driving gear 17 of a scanning motor 18, which is fixed on the light emitter 23. When the driving gear 17 is driven, the rotator 24 is rotated. The rotator 24 is rotated in such a manner that the optical axis of the laser beam 4 entering from the light emitter 23 is deflected by an angle of 90° using a pentagonal prism 14 and a laser plane is formed as the laser beam passes through a projection window 13. The pentagonal prism 14 is positioned on a rotation support member 15, which is rotated around the optical axis of the light emitter 23, and the rotation support member 15 is connected to the scanning motor 18 via the driving gear 17. The rotating condition of the rotation support member 15 is detected by an encoder 19 mounted on the rotation support member 15, and the detection signal of the encoder 19 is inputted to the control unit 54. The tilt angle of the light emitter 23 is detected by the tilt detecting unit 26, which is mounted on the tilting shaft 35 of the light emitter 23. The tilt detecting unit 26 is provided with an encoder, and the output signal from the encoder is inputted to the control unit 54. Based on the signal from the tilt detecting unit 26, the control unit 54 calculates the tilt of the light emitter 23 until it reaches a predetermined tilt angle. The tilting motor 36 is driven by a tilting motor driving unit 59, and the tilt can be set by driving the tilting motor 36 until the output of the tilt detecting unit 26 reaches a predetermined tilt angle. The photodetection unit 27 may be fixed on the casing 38. More preferably, it is mounted on the light emitter 23 so that it can be tilted integrally with the light emitter 23. Now, description will be given on the photodetection unit 27. A condenser lens 48 is provided at a position opposite to the photodetection window 34, and a reflection mirror 49 is arranged on the optical axis of the condenser lens 48. The optical axis of the condenser lens 48 runs in parallel to a reference plane, which is formed by rotation of the laser beam 4. Below the reflection mirror 49, a photodetection element 50 is disposed and the reflected laser beam 4' is converged on the photodetection element 50. In front of the photodetection element 50, a mask 51 is arranged. The mask 51 interrupts incident light noise entering the photodetection element 50, and a slit 52 is formed, which is designed long in a scanning direction of the reflected laser beam 4' (i.e. long in a direction perpendicular to the paper surface). The photodetection signal from the photodetection element 50 is inputted to a reflection light detecting unit 53, and the reflecting condition of the laser beam 4 at the level sensor 7 as detected by the reflection light detecting unit 53 is inputted to the control unit 54. To the control unit 54, a signal from the rotating unit encoder 32 is inputted. The control unit 54 drives a laser diode 56 via a light-emitting element driving unit 55, drives the scanning motor 18 via a scanning motor driving unit 57, drives the rotating unit motor 33 via a rotating unit motor driving unit 58, drives the tilting motor 36 via a tilting motor driving unit 59, and drives the levelling motor 42 via a levelling motor driving unit 64 based on the signals from the tilt sensors 44 and 45. Based on the signal from the reflection light detecting unit 53 or the signal from the tilt detecting unit 26, the encoder 19 and the rotating unit encoder 32, the control unit 54 displays information relating to a reference plane formed by the laser beam 4 such as direction, tilt, etc. of the rotary laser irradiating system main unit 20 on a display unit (not shown) of the rotary laser irradiating system main unit 20. For example, it displays information on which direction and at what angle the rotary laser irradiating system main unit 20 is rotated with respect to the level sensor 7 or tilt angle, tilting direction, etc. of the reference plane. Next, a description will be given of the level sensor 7 referring to Fig. 4. A band-like reflection sector 61 designed long in a vertical direction is arranged on each of the left and right hand sides of the level sensor 7. A portion in between the two reflection sectors 61 is a non-reflection sector 60. On the outer sides of each of the reflection sectors 61 is disposed a photodetection element 62 in band-like shape and extended in the vertical direction. The photodetection element 62 is provided at a certain angle with respect to the reflection sector 61. On the back side, a groove 63 to be engaged with the pole 6 is formed, and the level sensor 7 is installed with the pole 6 engaged with the groove 63. Now, the control device 11 will be described referring to Fig 5. The control device 11 is typically represented by a personal computer. The control device 11 comprises an arithmetic unit 65 and a storage unit 66. A program for arithmetic processing is preset and inputted in the storage unit 66. Also, a program for calculating topographical data based on working drawings, i.e. a height of ground surface with respect to plane coordinates and a position of the bulldozer 2, is preset and inputted. Further, the data such as the height of the rotary laser irradiating system 1, the distance from a blade edge 5a to the standard position of the level sensor 7, etc. are preset and inputted. To the control device 11, a signal received from a second GPS receiver 68 as described later is inputted, and also, a signal received from a radio receiver 10 as described later is inputted. Using the above arithmetic programs, the position of the bulldozer 2 can be calculated from the received signals. Further, from the calculation results and the topographical data based on the working drawings, which are preset and inputted, a tilt angle of the laser beam 4 emitted from the rotary laser irradiating system main unit 20 is calculated, and a command is issued to the control unit 54 of the rotary laser irradiating system main unit 20 based on the results of the calculation. The bulldozer 2 comprises a blade driving unit 71 for controlling a position of the blade 5 and a radio transmitter/receiver 72. First, a description will be given of the blade driving unit 71. The level sensor 7 is mounted on the pole 6. The distance between the blade edge 5a and the standard position of the level sensor 7 is a known value. A detection signal of the laser beam 4 by the level sensor 7 is inputted to an arithmetic unit 73. The arithmetic unit 73 calculates the height of the blade edge 5a and drives a hydraulic cylinder 75 via an electric/hydraulic circuit 74 to move the blade 5 up and down to determine the position. The electric/hydraulic circuit 74 comprises electromagnetic valves. The arithmetic unit 73 issues an open/close control command to the electric/hydraulic circuit 74 in accordance with a predetermined sequence. By opening or closing the electromagnetic valves via the electric/hydraulic circuit 74, supply or discharge of pressure fluid to or from the hydraulic cylinder 75 or flowrate regulation is controlled and the hydraulic cylinder 75 is moved up or down in a desired direction and at a desired speed. A display unit 76 is connected to the arithmetic unit 73, and the position or the digging condition of the blade 5 is displayed. Reference numeral 77 represents an operation unit, and it can directly perform manual operation according to the display on the display unit 76. While watching the display on the display unit 76, a manual positioning operation of the blade 5 is performed. A signal from the operation unit 77 is inputted to the arithmetic unit 73, and the arithmetic unit 73 drives the hydraulic cylinder 75 via the electric/hydraulic circuit 74 based on the input signal. Next, a description will be given of the radio transmitter/receiver 72. A first GPS receiver 80 is installed at a position, e.g. on the roof of the bulldozer 2, where there is no obstacle to interrupt radio waves coming from the satellite. Using a signal processor 82, signal processing such as amplification is performed on the information received by the first GPS receiver 80, and the information is transmitted to the radio receiver 10 from a transmitter 81. A second GPS receiver 68 is installed on a tripod 84 at a position which is closer to the rotary laser irradiating system 1 and serves as a reference point. The receiving result of the second GPS receiver 68 and the receiving result of the radio receiver 10 are inputted to the control device 11. Using the first GPS receiver 80 and the second GPS receiver 68, the position of the bulldozer 2 is detected by cinematic surveying. The first GPS receiver 80, the second GPS receiver 68 and the control device 11 constitute a surveying system, and the radio transmitter/receiver 72, the second GPS receiver 68, and the radio receiver 10 constitute a data communication system. In the following, a description will be given of operation of the system. The second GPS receiver 68 is installed at a known point, and the rotary laser irradiating system 1 is also installed at a known point. After the installation, levelling for the rotary laser irradiating system 1 is performed first. The levelling is performed by cooperative operation of tilt adjustment by the tilt setting unit 25 and horizontal detection of the tilt sensors 44 and 45. When the levelling operation has been completed, the direction of the rotary laser irradiating system main unit 20 is aligned with the level sensor 7 and initialization is performed. The initialization is required because a tilting direction of the rotary laser irradiating system main unit 20 does not agree at first with the setting of the control device 11. For the initialization, the rotary laser irradiating system main unit 20 installed at a known point is directed toward the level sensor 7 of the bulldozer 2, the data of which are already known by the GPS receivers 80 and 68. In order to detect the level sensor 7, the laser beam 4 is rotated for scanning. The reflected laser beam 4' from the level sensor 7 is detected by the photodetection unit 27. Based on the result of detection, the control unit 54 rotates the rotating unit 22 and turns it toward the level sensor 7. When initialization is performed manually, the collimator 28 is collimated, and the rotating unit 22 and the tilt setting unit 25 are operated. In this case, there is no need to use the photodetection unit 27 and the like. The information received by the radio receiver 10 and the signal received by the second GPS receiver 68 are inputted to the control device 11. At the control device 11, the position of the bulldozer 2 is surveyed. The result of the surveying is information on the plane position of the bulldozer 2. The control device 11 calculates a gradient of the laser beam 4 using the arithmetic unit 65 based on the plane position information and the working data inputted in the storage unit 66. The calculation result is inputted to the control unit 54 of the rotary laser irradiating system 1. The control unit 54 drives and controls the tilt setting unit 25 so that the reference plane formed by the laser beam 4 will have the calculated gradient. Based on the signal from the control unit 54, the tilt setting unit 25 drives the tilting motor 36 and tilts the light emitter 23 by rotating the tilting shaft 35 via the gear train 37. By the tilting of the light emitter 23, the laser beam 4 irradiated by rotary irradiation from the rotor 24 is tilted, and the reference plane formed by the laser beam 4 has now the predetermined gradient. When the setting of the tilting direction and the gradient of the laser beam 4 has been completed, positioning of the blade 5 is performed. Based on the signal received from the level sensor 7, the arithmetic unit 73 detects the photodetecting position of the level sensor 7. After comparatively calculating the photodetecting position and the reference position, if there is any deviation, a drive control signal is issued to the electric/hydraulic circuit 74 to correct the deviation. The electric/hydraulic circuit 74 drives the hydraulic cylinder 75 and moves the blade 5 up and down. Because the level sensor 7 is moved up and down integrally with the blade 5, the amount of upward or downward movement of the blade 5 agrees with the amount of upward or downward movement of the level sensor 7. When the photodetecting position on the level sensor 7 concurs with the reference position, the position of the blade 5 is determined. Ground levelling operation is performed by moving the bulldozer 2. The data received by the first GPS receiver 80 is transmitted to the radio receiver 10 by the transmitter 81. Further, receiving data from the second GPS receiver 68 is inputted to the control device 11. As a result, the control device 11 calculates the position of the bulldozer 2. The height and tilt of the levelled ground surface at the position of the bulldozer 2 are calculated according to the working data. Where the levelled ground surface is an inclined surface with a constant gradient, ground levelling can be performed without changing the gradient of the reference plane formed by the rotary laser irradiating system main unit 20. Where it is a curved surface, the ground can be levelled to a curved surface by changing the gradient of the reference plane formed by the laser beam as the bulldozer 2 is moved. According to the present system, it is possible to automatically perform ground levelling in accordance with the working data. Also, the operator may perform ground levelling operation manually based on the data displayed on the display unit 76. In the above embodiment, the level sensor 7 is provided on the blade 5, while the level sensor 7 may be installed on a body of the bulldozer 2 if it is designed in such manner that the position of the blade edge 5a can be detected according to extension or shrinking of the hydraulic cylinder 75 or by the position of an arm which is supporting the blade 5. The above explanation has been given on the GPS measuring system of cinematic type, while it is needless to say that GPS measuring system of any other type may be used if a moving point can be immediately detected. It may be designed in such manner that reciprocal scanning is performed over the full range of the level sensor 7 based on the output of the encoder 19 for detecting rotating position of the rotator 24, or the laser beam may be rotated by limiting the emission of the laser beam within the range of the level sensor 7. As described above, when ground levelling operation is performed in accordance with the reference plane formed by the laser beam, it is possible according to the present invention to easily and reliably produce not only a horizontal surface but also an inclined surface or a curved surface without requiring the skill of an experienced operator. This is done by measuring the position of the construction equipment in real time and by controlling the height of the ground levelling tool based on working data. It is further possible to reduce the time needed for construction work.

Claims: A construction equipment control system, comprising a rotary laser irradiating system (1) for emitting a laser beam (4) and forming a laser beam reference plane, the rotary laser irradiating system further being capable of tilting the laser beam reference plane, a level sensor (7) for installing on a ground levelling tool (5) on construction equipment (2) for performing photodetection of the laser beam to give an indication of a height of the ground levelling tool (5), a GPS receiving system (68, 80) for detecting a position of said construction equipment, and a control device (11) for controlling a gradient of said laser beam reference plane formed by said rotary laser irradiating system (1) based on the detection result of the position of said construction equipment by said GPS receiving system (68, 80). A construction equipment control system according to claim 1, wherein said control device (11) comprises a storage unit (66) for storing at least working data, and an arithmetic unit (65) for calculating the position of said construction equipment based on the receiving result of said GPS receiving system (68, 80), and said rotary laser irradiating system (1) is controlled according to the calculated position of the construction equipment and said working data. A construction equipment control system according to claim 1 or claim 2, wherein said rotary laser irradiating system (1) is adapted to form a laser beam reference plane by performing reciprocal scanning toward the level sensor. A construction equipment control system according to any of the preceding claims, wherein said GPS receiving system (68, 80) comprises a first GPS receiver (80) and a second GPS receiver (68), and said first GPS receiver is mounted on the construction equipment (2), and the second GPS receiver is installed at a known point. A construction equipment control system as claimed in claim 1, further comprising another GPS receiving system for detecting a position of said rotary laser irradiating system. A construction equipment control system as claimed in any of the preceding claims, wherein said rotary laser irradiating system (1) is adapted to form a reference plane by irradiating the laser beam (4) only within photodetection range of the level sensor (7). A construction equipment control system according to any of the preceding claims, wherein the direction of said rotary laser irradiating system (1) is aligned with said level sensor (7), and said control device (11) is adapted to be initialized by said alignment. A construction equipment control system according to claim 7, wherein said rotary laser irradiating system (1) comprises a photodetection unit (27), said photodetection unit being adapted to detect a reflected laser beam (4') from said level sensor (7), said control device (11) being adapted to align the direction of said rotary laser irradiating system (1) with said level sensor (7) based on the result of detection by said photodetection unit (27), and said control device (11) being adapted to be initialized by said alignment.

Inventors: HAYASHI KUNIHIRO, HIRANO SATOSHI, OHTOMO FUMIO, HAYASHI, KUNIHIRO, HIRANO, SATOSHI, OHTOMO, FUMIO, HAYASHI, KUNIHIRO, C/O KABUSHIKI KAISHA TOPCON, Hirano, Satoshi, c/o Kabushiki Kaisha Topcon, OHTOMO, FUMIO, C/O KABUSHIKI KAISHA TOPCON
Applicants: TOPCON CORP, KABUSHIKI KAISHA TOPCON
Application year: 1999
Main classification: G01C23
IPC codes: G01C5, G01C15, E02F9