Motor grader and draw bar posture calculation method for motor grader

Abstract

To provide a motor grader that can calculate a draw bar's posture with use of an identification marker.SOLUTION: A motor grader comprises a front frame, a draw bar fitted oscillatably on the front frame, a first identification marker fitted on the draw bar, a camera fitted on the front frame to picture the first identification marker, and a controller that calculates a first posture of the draw bar in relation to the camera based on a first picture data of the first identification marker which is obtained by the picturing.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a motor grader and a method for calculating a drawbar attitude of the motor grader. [Background technology]

[0002] A motor grader is known in the art. The motor grader includes a drawbar to which a turning circle is attached. A blade is attached to the turning circle.

[0003] U.S. Patent Application Publication No. 2018 / 0061040A1 (Patent Document 1) discloses a motor grader capable of tracking the blade. Specifically, the motor grader in Patent Document 1 includes first and second optical targets operably coupled to the blade, a first camera that collects first imaging data of the first optical target within a first field of view, a second camera that collects second imaging data of the second optical target within a second field of view, a selector that selects at least one of the first and second imaging data, and a processor that determines the orientation of the blade based on the selected imaging data. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2018 / 0061040A1 Summary of the Invention [Problem to be solved by the invention]

[0005] In the motor grader of Patent Document 1, the blade attitude is determined by capturing images of multiple optical targets (identification markers) with separate cameras. However, this is not the only method, and the blade attitude can be relatively easily determined from the drawbar attitude. Therefore, if the drawbar attitude can be calculated, the blade attitude can be determined.

[0006] The present disclosure provides a motor grader and a method for calculating the attitude of a drawbar of a motor grader that can calculate the attitude of a drawbar using an identification marker. [Means for solving the problem]

[0007] A motor grader according to one embodiment of the present disclosure includes a front frame, a drawbar swingably attached to the front frame, a first identification marker attached to the drawbar, a camera attached to the front frame for capturing an image of the first identification marker, and a controller for calculating a first attitude of the drawbar relative to the camera based on first image data of the first identification marker obtained by capturing the image. [Effects of the Invention]

[0008] According to the above configuration, the attitude of the drawbar can be calculated using the identification marker. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a motor grader. [Figure 2] FIG. 2 is a side view of the front frame side of the motor grader. [Figure 3] FIG. 3 is a plan view of the front frame side of the motor grader in the state shown in FIG. 2. [Figure 4] FIG. 2 is a block diagram illustrating the functional configuration of the motor grader. [Figure 5] FIG. 10 is a flowchart for calculating the position of the cutting edge of the blade. [Figure 6] FIG. 6 is a flowchart showing details of the process in step S1 of FIG. 5. [Figure 7] FIG. 6 is a flowchart showing details of the process in step S2 of FIG. 5. [Figure 8] FIG. 10 is a flowchart of a modification of the method for calculating the position of the cutting edge of the blade. [Figure 9] FIG. 9 is a flowchart showing details of the process of step S2A in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0010] A motor grader according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, identical parts are designated by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0011] Fig. 1 is a perspective view that shows a schematic configuration of a motor grader 1 according to this embodiment. As shown in Fig. 1, the motor grader 1 mainly includes front wheels 11, rear wheels 12, a body frame 2, a cab 3, and a work implement 4. The work implement 4 mainly includes a drawbar 40, a turning circle 41, and a blade 42. The motor grader 1 uses the blade 42 to perform tasks such as ground leveling, snow removal, light cutting, and material mixing.

[0012] In the following description of the figures, the direction in which the motor grader 1 travels straight ahead is referred to as the fore-and-aft direction of the motor grader 1. In the fore-and-aft direction of the motor grader 1, the side where the front wheels 11 are arranged relative to the work equipment 4 is referred to as the front direction. In the fore-and-aft direction of the motor grader 1, the side where the rear wheels 12 are arranged relative to the work equipment 4 is referred to as the rear direction.

[0013] The left-right direction of the motor grader 1 is the direction perpendicular to the front-to-back direction in a plan view. When an operator sitting in the driver's seat of the motor grader 1 looks forward, the right and left sides of the left-to-right direction are the right and left directions, respectively. The up-to-down direction of the motor grader 1 is the direction perpendicular to the plane defined by the front-to-back and left-to-right directions. In the up-to-down direction, the side with the ground is the bottom side, and the side with the sky is the top side.

[0014] The body frame 2 extends in the front-rear direction and includes a rear frame 21 and a front frame 22.

[0015] The rear frame 21 supports an exterior cover 25 and components such as an engine arranged in the engine compartment 6. The exterior cover 25 covers the engine compartment 6. Each of the above-mentioned four rear wheels 12 is attached to the rear frame 21 so as to be rotatable by driving force from the engine.

[0016] The front frame 22 is attached in front of the rear frame 21. The front frame 22 is rotatably connected to the rear frame 21. The front frame 22 extends in the front-to-rear direction. The front frame 22 has a base end 22r connected to the rear frame 21 and a front end 22f opposite the base end 22r. The base end 22r of the front frame 22 is connected to the front end of the rear frame 21 by a vertical center pin.

[0017] An articulate cylinder (not shown) is attached between the front frame 22 and the rear frame 21. The front frame 22 is provided so as to be rotatable relative to the rear frame 21 by extension and contraction of the articulate cylinder. The articulate cylinder is provided so as to be extendable and contractable by operation of an operating lever provided inside the cab 3.

[0018] The above-mentioned two front wheels 11, for example, are rotatably attached to the front end portion 22f of the front frame 22. The front wheels 11 are attached so as to be able to turn relative to the front frame 22 by extension and contraction of a steering cylinder (not shown). The motor grader 1 can change its direction of travel by extension and contraction of the steering cylinder. The steering cylinder can be extended and contracted by operating a handle or a steering operation lever provided inside the cab 3.

[0019] A counterweight 51 is attached to the front end portion 22f of the front frame 22. The counterweight 51 is a type of attachment that is attached to the front frame 22. The counterweight 51 is located in front of the front frame 22.

[0020] The cab 3 is mounted on the front frame 22. Inside the cab 3, there are provided operating parts (not shown) such as a steering wheel, a gearshift lever, an operating lever for the work equipment 4, a brake, an accelerator pedal, an inching pedal, and various switches.

[0021] Fig. 2 is a side view of the front frame 22 side of the motor grader 1. Fig. 3 is a plan view of the front frame 22 side of the motor grader 1 in the state of Fig. 2. Figs. 2 and 3 show a state in which the work implement 4 is in the neutral position.

[0022] The "state in which the work implement 4 is in the neutral position" refers to a state in which the draw bar 40 is not misaligned to the left or right with respect to the front frame 22, the longitudinal direction (width direction) of the blade 42 is perpendicular to the fore-and-aft direction of the draw bar 40, and the center in the width direction of the blade 42 is located directly below the axis in the fore-and-aft direction of the draw bar 40. In other words, the "state in which the work implement 4 is in the neutral position" refers to a state in which the draw bar 40 is not misaligned to the left or right with respect to the front frame 22, the longitudinal direction of the blade 42 is perpendicular to the fore-and-aft direction of the front frame 22, and the center in the longitudinal direction of the blade 42 is located directly below the axis in the fore-and-aft direction of the front frame 22.

[0023] 2 and 3, the draw bar 40 is disposed below the front frame 22. The draw bar 40 is moved by a pair of lift cylinders 44, 45 in a direction approaching the front frame 22 (a direction in which the blade 42 moves away from the ground) and a direction away from the front frame 22.

[0024] The drawbar 40 has a front end 40f and a rear end 40r. The front end 40f is connected to the front end 22f of the front frame 22 using a ball axle 402. The rear end 40r of the drawbar 40 is supported on the front frame 22 by a lift cylinder 44 and a lift cylinder 45 (FIG. 1). The ball axle 402 connects the drawbar 40 to the front frame 22 in front of the drawbar 40 so that the drawbar 40 can swing relative to the front frame 22. The drawbar 40 is attached to the front frame 22 so that it can swing.

[0025] A central axis J1, which is the longitudinal axis of the drawbar 40, extends from the front end 40f toward the turning center C (a point on the rotation axis J2) of the turning circle 41. When the work implement 4 is in the neutral position, the central axis J1 overlaps with a central axis J3 (FIG. 3), which is the longitudinal axis of the front frame 22, in a plan view (top view) of the motor grader 1.

[0026] The extension and contraction of the lift cylinders 44, 45 allows the rear end 40r of the draw bar 40 to move up and down relative to the front frame 22. The extension and contraction of the lift cylinders 44, 45 allows the draw bar 40 to swing up and down about an axis along the vehicle travel direction. The extension and contraction of the draw bar shift cylinder 46 allows the draw bar 40 to move left and right relative to the front frame 22. The extension and contraction of the draw bar shift cylinder 46 causes the draw bar 40 to move in the direction of arrow 903 ( FIG. 3 ).

[0027] The lift cylinders 44, 45 are attached to the draw bar 40 and the bracket 50. The heads 44h, 45h of the lift cylinders 44, 45 are attached to the bracket 50. The tip of the rod 44r of the lift cylinder 44 and the tip of the rod 45r (FIG. 1) of the lift cylinder 45 are attached to the draw bar 40. The bracket 50 is attached to the front frame 22.

[0028] The drawbar shift cylinder 46 is attached to the drawbar 40 and a bracket 50. The tip of the head 46h of the drawbar shift cylinder 46 is attached to the drawbar 40. The tip of the rod 46r of the drawbar shift cylinder 46 is attached to the bracket 50.

[0029] The turning circle 41 is disposed below the front frame 22. The turning circle 41 is disposed below the draw bar 40. The turning circle 41 is supported at the rear end of the draw bar 40 so as to be able to turn (rotate). The turning circle 41 can be driven by a turning motor 49 (FIG. 1) to turn relative to the draw bar 40 in both the clockwise and counterclockwise directions as viewed from above the vehicle. The turning circle 41 rotates in the direction of arrow 902 (FIG. 3). The turning circle 41 rotates in the direction of arrow 902 relative to the draw bar 40 around a rotation axis J2 (FIG. 2).

[0030] The blade 42 is disposed on the turning circle 41. The blade angle of the blade 42 is adjusted by the turning drive of the turning circle 41. The blade 42 is disposed between the front wheel 11 and the rear wheel 12. The front wheel 11 is disposed forward of the blade 42. The rear wheel 12 is disposed rearward of the blade 42. The blade 42 is disposed between the front end of the body frame 2 and the rear end of the body frame 2. The blade 42 is supported on the turning circle 41. The blade 42 is supported by the draw bar 40 via the turning circle 41. The blade 42 is supported by the front frame 22 via the turning circle 41 and the draw bar 40.

[0031] The blade 42 is supported so as to be movable in the left-right direction relative to the revolving circle 41. The blade 42 moves in the direction of the arrow 901 (FIG. 3). The blade 42 makes a stroke in the direction of the arrow 901. The blade 42 rotates about the rotation axis J2 as the revolving circle 41 is driven to revolve.

[0032] Specifically, the blade shift cylinder 47 is attached to the turning circle 41 and the blade 42, and is disposed along the longitudinal direction of the blade 42. The blade shift cylinder 47 enables the blade 42 to move left and right relative to the turning circle 41. The blade 42 is also movable in a direction intersecting the longitudinal direction of the front frame 22.

[0033] The blade 42 is supported so as to be swingable about an axis extending in the longitudinal direction of the blade 42 relative to the turning circle 41. Specifically, a tilt cylinder 48 is attached to the turning circle 41 and the blade 42. By extending and contracting the tilt cylinder 48, the blade 42 swings about an axis extending in the longitudinal direction of the blade 42 relative to the turning circle 41, and the tilt angle of the blade 42 relative to the traveling direction of the vehicle (the rake angle of the blade 42 relative to the ground) can be changed.

[0034] As described above, the blade 42 is configured to be able to move up and down relative to the motor grader 1, swing around an axis along the vehicle's travel direction, change the tilt angle in the fore-and-aft direction, move left and right, and swing around an axis extending in the longitudinal direction of the blade 42, via the drawbar 40 and the turning circle 41.

[0035] The motor grader 1 further includes a camera 800 and a plurality of identification markers 711 to 713, 721, and 722. In this example, the identification markers 711 to 713, 721, and 722 are subjects of the camera 800.

[0036] The camera 800 has a lens 801 and a main body 802 with a built-in image sensor. The lens 801 has an angle of view that allows the five markers 711 to 713, 721, and 722 to be in the field of view regardless of the attitude of the work machine 4. The lens 801 is a wide-angle lens. Preferably, the lens 801 is an ultra-wide-angle lens. In this example, the lens 801 is a fisheye lens, which is a type of wide-angle lens.

[0037] The front frame 22 further has a lower end surface 22u that faces the drawbar 40. The camera 800 is attached to the lower end surface 22u so that the optical axis of the lens 801 faces vertically downward. In this example, in a plan view of the motor grader 1, the camera 800 is located directly below a central axis J3 that extends in the front-to-rear direction of the front frame 22. In a side view of the motor grader 1 (FIG. 2), the camera 800 is located between the front end 40f and the rear end 40r of the drawbar 40.

[0038] Each of the markers 711 to 713 is attached to the drawbar 40. Each of the markers 721 and 722 is attached to the blade 42. The number of markers attached to the drawbar 40 is not limited to three, and may be one, two, or four or more. The number of markers attached to the blade 42 is not limited to two, and may be one, or three or more.

[0039] However, by attaching multiple markers 711-713 to the drawbar 40, redundancy can be ensured against dirt and damage to the markers, and the "attitude of the drawbar 40 relative to the camera 800," which will be described later, can be calculated with high accuracy (step S1 in FIG. 5, particularly step S16 in FIG. 6). Similarly, by attaching multiple markers 721, 722 to the blade 42, redundancy can be ensured against dirt and damage to the markers, and the "attitude of the blade 42 relative to the camera 800," which will be described later, can be calculated with high accuracy (step S2 in FIG. 5, particularly step S25 in FIG. 6).

[0040] Each of the markers 711-713, 721, and 722 has a plurality of regions (cells) arranged in a matrix, with some of the regions painted black. Each of the markers 711-713, 721, and 722 has a pattern made up of a plurality of white cells and a plurality of black cells. The pattern of the marker 711, the pattern of the marker 712, the pattern of the marker 713, the pattern of the marker 721, and the pattern of the marker 722 are different from one another. Each pattern is created on the surface of a plate-like member or attached to that surface. Details of the attachment positions of the markers 711-713, 721, and 722 will be described below using specific examples.

[0041] Markers 711-713 are attached to the upper surface of drawbar 40. Markers 711-713 are attached to drawbar 40 so that markers 711-713 (more specifically, patterns) face upward at least when drawbar 40 is in the neutral position.

[0042] The marker 711 is installed in front of the camera 800 in a plan view of the motor grader 1. In this example, the marker 711 is located directly above the central axis J1 in a plan view of the work implement 4. When the drawbar 40 is in the neutral position, the marker 711 is located directly below the central axis J3 in a plan view of the motor grader 1.

[0043] The markers 712 and 713 are installed behind the camera 800 in a plan view of the motor grader 1. The markers 712 and 713 are located behind the marker 711. The marker 712 is located at a position spaced apart to the left of the central axis J1 in a plan view of the work machine 4. The marker 713 is located at a position spaced apart to the right of the central axis J1 in a plan view of the work machine 4. The marker 713 is installed at a position that is linearly symmetrical to the marker 712 with respect to the central axis J1.

[0044] The installation positions of the markers 711 to 713 are not limited to the above positions. There are no particular limitations on the installation positions of the markers 711 to 713 as long as they are positions that can be imaged by the camera 800. However, from the viewpoint of ensuring redundancy against dirt and damage to the markers, it is preferable that the markers 711 to 713 are spaced apart by a predetermined distance or more.

[0045] The markers 721, 722 are attached to the blade 42. The markers 721, 722 are attached above the blade 42. The markers 721, 722 are attached to the blade 42 by a support member 790. The markers 721, 722 are installed at positions spaced apart from the upper end surface of the blade 42. The markers 721, 722 are located rearward of the three markers 711-713 attached to the drawbar 40, at least when the work implement 4 is in the neutral position.

[0046] Marker 721 is attached to the left end side of blade 42. Marker 722 is attached to the right end side of blade 42. In this example, marker 722 is placed at a position symmetrical to marker 721 with respect to the center of blade 42 in the direction of arrow 901.

[0047] The markers 721, 722 are attached to the blade 42 so that the patterns of the markers 721, 722 face forward at least when the work implement 4 is in a neutral position. The markers 721, 722 are attached to the blade 42 so that the normal to each pattern (plane) of the markers 721, 722 is parallel to the central axis J1. However, this is not limiting, and the markers 721, 722 may be attached to the blade 42 so that the normal is not parallel to the central axis J1. When the work implement 4 is in a neutral state, the markers 721, 722 (more specifically, the patterns) may face upward.

[0048] The installation positions of the markers 721 and 722 are not limited to the above positions. There are no particular limitations on the installation positions of the markers 721 and 722 as long as they are positions that can be imaged by the camera 800. However, from the viewpoint of preventing contamination by soil and sand scraped by the blade 42, it is preferable to install the markers 721 and 722 above the blade 42 as described above.

[0049] Each of the markers 711 to 713 is attached to the drawbar 40. Therefore, the position (relative position) of each of the markers 711 to 713 with respect to the drawbar 40 does not change. Each of the markers 721 and 722 is attached to the blade 42. Therefore, the position (relative position) of each of the markers 721 and 722 with respect to the blade 42 does not change.

[0050] On the other hand, camera 800 is attached to front frame 22. Therefore, when the attitude of at least drawbar 40 changes, the positions (relative positions) of markers 711-713, 721, and 722 with respect to camera 800 change. Even when the attitude of drawbar 40 is in the neutral position, when the attitude of blade 42 changes, the positions (relative positions) of markers 721 and 722 with respect to camera 800 change.

[0051] In this example, AR (Augmented Reality) markers are used as the markers 711 to 713, 721, and 722. However, the markers 711 to 713, 721, and 722 are not limited to AR markers. It is sufficient that the markers 711 to 713, 721, and 722 can be distinguished from one another.

[0052] It is sufficient that the identifier of each marker 711-713, 721, 722 and the orientation of each marker 711-713, 721, 722 when the camera 800 is used as a reference can be determined. More specifically, with regard to the orientation of each marker 711-713, 721, 722, it is sufficient that the position (position in a three-dimensional coordinate system) and the tilt state (Euler angle) of each marker 711-713, 721, 722 when the camera 800 is used as a reference can be determined. Note that this determination is performed by the controller 150 (more specifically, a processor) described later, based on image data acquired by the camera 800.

[0053] Markers 711 to 713 attached to drawbar 40 correspond to "first identification markers" in the present disclosure. Markers 721 and 722 attached to blade 42 correspond to "second identification markers" in the present disclosure.

[0054] Fig. 4 is a block diagram illustrating the functional configuration of the motor grader 1. As shown in Fig. 4, the motor grader 1 includes a camera 800 and a controller 150. The controller 150 includes a drawbar attitude calculation unit 151, a blade attitude calculation unit 152, a first cutting edge position calculation unit 153, and a second cutting edge position calculation unit 154.

[0055] The drawbar attitude calculation unit 151, the blade attitude calculation unit 152, the first cutting edge position calculation unit 153, and the second cutting edge position calculation unit 154 are typically functional block diagrams that are realized by a processor (not shown) executing a program. However, without being limited to this, the drawbar attitude calculation unit 151, the blade attitude calculation unit 152, the first cutting edge position calculation unit 153, and the second cutting edge position calculation unit 154 may be realized only by hardware (integrated circuits) such as ASIC.

[0056] The drawbar attitude calculation unit 151 periodically acquires image data obtained by imaging with the camera 800 from the camera 800. The drawbar attitude calculation unit 151 periodically calculates the attitude of the drawbar 40 based on the acquired image data. The drawbar attitude calculation unit 151 calculates the attitude of the drawbar 40 when the camera 800 is used as a reference, using image data of three markers 711 to 713 attached to the drawbar 40 out of the five markers 711 to 713, 721, and 722.

[0057] The drawbar attitude calculation unit 151 periodically sends the calculated attitude (predicted position) of the drawbar 40 to the first cutting edge position calculation unit 153. Note that the cycle in which the drawbar attitude calculation unit 151 acquires image data from the camera 800 does not have to be the same as the cycle in which the drawbar attitude calculation unit 151 calculates the attitude of the drawbar 40. Details of the processing by the drawbar attitude calculation unit 151 will be described later.

[0058] The blade attitude calculation unit 152 periodically acquires image data obtained by imaging with the camera 800 from the camera 800. The blade attitude calculation unit 152 periodically calculates the attitude of the blade 42 based on the acquired image data. The blade attitude calculation unit 152 calculates the attitude of the blade 42 when the camera 800 is used as a reference, using image data of two markers 721 and 722 attached to the blade 42 out of the five markers 711 to 713, 721 and 722.

[0059] The blade attitude calculation unit 152 periodically sends the calculated attitude (predicted position) of the blade 42 to the first cutting edge position calculation unit 153. Note that the cycle in which the blade attitude calculation unit 152 acquires image data from the camera 800 does not have to be the same as the cycle in which the blade attitude calculation unit 152 calculates the attitude of the blade 42. Details of the processing by the blade attitude calculation unit 152 will be described later.

[0060] First cutting edge position calculation unit 153 calculates the position of cutting edge 42a relative to camera 800, based on the attitude (predicted position) of drawbar 40 and the attitude (predicted position) of blade 42, which are periodically received. The calculation of the position of cutting edge 42a is periodically performed. After calculating the position of cutting edge 42a, first cutting edge position calculation unit 153 sends information indicating the calculated position of cutting edge 42a to second cutting edge position calculation unit 154.

[0061] The second cutting edge position calculation unit 154 calculates the position of the cutting edge 42a relative to the ball axis 402, based on the information received from the first cutting edge position calculation unit 153 and indicating the position of the cutting edge 42a relative to the camera 800. The information on the position of the cutting edge 42a calculated by the second cutting edge position calculation unit 154 is used in various processes in the controller 150.

[0062] Fig. 5 is a flow diagram for calculating the position of cutting edge 42a of blade 42. As shown in Fig. 5, in step S1, controller 150 calculates the attitude of drawbar 40 with respect to camera 800 based on images of markers 711 to 713 attached to drawbar 40. Drawbar attitude calculation unit 151 of controller 150 calculates the attitude of drawbar 40 when the position of camera 800 is used as a reference.

[0063] In step S2, controller 150 calculates the attitude of blade 42 with respect to camera 800 based on images of markers 721, 722 attached to blade 42. Drawbar attitude calculation unit 151 of controller 150 calculates the attitude of blade 42 when the position of camera 800 is used as a reference.

[0064] In step S3, controller 150 calculates the position of cutting edge 42a relative to camera 800 based on the attitude of drawbar 40 relative to camera 800 calculated in step S1 and the attitude of blade 42 relative to camera 800 calculated in step S2. First cutting edge position calculation unit 153 calculates the position of cutting edge 42a when the position of camera 800 is used as a reference.

[0065] In step S4, based on the position of the cutting edge 42a calculated in step S3, the controller 150 calculates the position of the cutting edge 42a relative to the ball pivot 402. The second cutting edge position calculation unit 154 calculates the position of the cutting edge 42a when the position of the ball pivot 402 is used as a reference.

[0066] Fig. 6 is a flow diagram showing details of the processing of step S1 in Fig. 5. As shown in Fig. 6, in step S11, the drawbar attitude calculation unit 151 calculates the three-dimensional orthogonal coordinates of each of the markers 711 to 713 attached to the drawbar 40 and the Euler angles of each of the markers 711 to 713 based on the image data. In particular, the drawbar attitude calculation unit 151 calculates the three-dimensional orthogonal coordinates and Euler angles of each of the markers 711 to 713 from the image data based on the three-dimensional orthogonal coordinates (fixed values) of each of the markers 711 to 713 and the Euler angles (fixed values) of each of the markers 711 to 713 when the work implement 4 is in the neutral position. Note that each of the above-mentioned fixed values ​​is stored in advance in the controller 150. Each of the fixed values ​​described below is also stored in advance in the controller 150.

[0067] The Euler angles may be, for example, ZYX Euler angles, which are defined by a roll angle φ around the x-axis, a pitch angle θ around the y-axis, and a yaw angle ψ around the z-axis.

[0068] In step S12, based on the three-dimensional Cartesian coordinates and Euler angles of the marker 711 calculated in step S11, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 when the position of the camera 800 is used as a reference, and the Euler angles of the turning circle 41. In detail, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates and the Euler angles using information on the three-dimensional Cartesian coordinates (fixed values) of the marker 711, the Euler angles (fixed values) of the marker 711, and the three-dimensional Cartesian coordinates (fixed values) of the turning center C when the work implement 4 is in the neutral position.

[0069] More specifically, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 when the position of the camera 800 is used as a reference, using information on the difference (offset) between the three-dimensional Cartesian coordinates (fixed values) of the marker 711 when the work implement 4 is in the neutral position and the three-dimensional Cartesian coordinates (fixed values) of the turning center C. This also applies to the processing in steps S13 and S14 described later.

[0070] Similarly, in step S13, based on the three-dimensional Cartesian coordinates and Euler angles of the marker 712 calculated in step S11, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 when the position of the camera 800 is used as a reference, and the Euler angles of the turning circle 41. In detail, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates and the Euler angles using information on the three-dimensional Cartesian coordinates (fixed values) of the marker 712, the Euler angles (fixed values) of the marker 712, and the three-dimensional Cartesian coordinates (fixed values) of the turning center C when the work implement 4 is in the neutral position.

[0071] In step S14, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 when the position of the camera 800 is used as a reference, and the Euler angles of the turning circle 41, based on the three-dimensional Cartesian coordinates and Euler angles of the marker 713 calculated in step S11. In detail, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates and the Euler angles using information on the three-dimensional Cartesian coordinates (fixed values) of the marker 713, the Euler angles (fixed values) of the marker 713, and the three-dimensional Cartesian coordinates (fixed values) of the turning center C when the work implement 4 is in the neutral position. The order of steps S12, S13, and S14 is not particularly limited.

[0072] In step S15, the drawbar attitude calculation unit 151 determines whether or not each of the three-dimensional orthogonal coordinates and each of the Euler angles calculated in steps S12 to S14 contains an abnormal value. Specifically, the drawbar attitude calculation unit 151 determines whether or not each of the three-dimensional orthogonal coordinates falls within a preset coordinate range. The drawbar attitude calculation unit 151 determines whether or not each of the Euler angles falls within a preset Euler angle range. More specifically, the drawbar attitude calculation unit 151 determines whether or not each of the three independent variables described above falls within a preset range. The drawbar attitude calculation unit 151 determines that three-dimensional coordinates and Euler angles that do not fall within the preset ranges are abnormal values.

[0073] If it is determined that no abnormal values ​​are included (NO in step S15), the drawbar attitude calculation unit 151 advances the process to step S16. If it is determined that an abnormal value is included (YES in step S15), the drawbar attitude calculation unit 151 deletes the abnormal value to improve accuracy in step S17. The drawbar attitude calculation unit 151 then advances the process to step S16.

[0074] In step S16, the drawbar attitude calculation unit 151 determines the three-dimensional orthogonal coordinates of the turning center C of the turning circle 41 and the Euler angles of the turning circle 41 when the position of the camera 800 is used as a reference, based on the three-dimensional orthogonal coordinates (excluding abnormal values) and the Euler angles (excluding abnormal values) calculated in steps S12 to S14. In this way, the drawbar attitude calculation unit 151 determines the attitude of the drawbar 40 with respect to the camera 800.

[0075] For example, the drawbar attitude calculation unit 151 calculates the average of each three-dimensional orthogonal coordinate (excluding abnormal values) to determine the three-dimensional orthogonal coordinate of the turning center C of the turning circle 41 when the camera 800 is used as the reference. The drawbar attitude calculation unit 151 calculates the average of each Euler angle (excluding abnormal values) to determine the Euler angle of the turning circle 41 when the camera 800 is used as the reference.

[0076] Fig. 7 is a flow diagram showing details of the processing of step S2 in Fig. 5. As shown in Fig. 7, in step S21, the blade attitude calculation unit 152 calculates the three-dimensional Cartesian coordinates of each of the markers 721, 722 attached to the blade 42 and the Euler angles of each of the markers 721, 722 based on the image data.

[0077] In step S22, the blade attitude calculation unit 152 calculates the position of the blade 42 and the Euler angles of the blade 42 when the position of the camera 800 is used as a reference, based on the three-dimensional orthogonal coordinates and Euler angles of the marker 721 calculated in step S21. In more detail, the blade attitude calculation unit 152 calculates the three-dimensional orthogonal coordinates and the Euler angles using information on the three-dimensional orthogonal coordinates (fixed values) of the marker 721 and the Euler angles (fixed values) of the marker 721 when the work implement 4 is in the neutral position.

[0078] In step S23, the blade attitude calculation unit 152 calculates the position of the blade 42 relative to the position of the camera 800 and the Euler angles of the blade 42 based on the three-dimensional orthogonal coordinates and Euler angles of the marker 722 calculated in step S21. In more detail, the blade attitude calculation unit 152 calculates the three-dimensional orthogonal coordinates and the Euler angles using information on the three-dimensional orthogonal coordinates (fixed values) of the marker 722 and the Euler angles (fixed values) of the marker 722 when the work implement 4 is in the neutral position. The order of steps S22 and S23 is not particularly limited.

[0079] In step S24, the blade attitude calculation unit 152 determines whether or not the three-dimensional orthogonal coordinates and the Euler angles calculated in steps S22 and S23 contain abnormal values. Specifically, the blade attitude calculation unit 152 determines whether or not the three-dimensional orthogonal coordinates fall within a predetermined coordinate range. The blade attitude calculation unit 152 determines whether or not the Euler angles fall within a predetermined Euler angle range. More specifically, the blade attitude calculation unit 152 determines whether or not each of the three independent variables described above falls within a predetermined range. The blade attitude calculation unit 152 determines that three-dimensional coordinates and Euler angles that do not fall within the predetermined ranges are abnormal values.

[0080] If it is determined that no abnormal values ​​are included (NO in step S24), the blade attitude calculation unit 152 proceeds to step S25. If it is determined that an abnormal value is included (YES in step S24), the blade attitude calculation unit 152 deletes the abnormal value to improve accuracy in step S2617. The blade attitude calculation unit 152 then proceeds to step S25.

[0081] In step S25, the blade attitude calculation unit 152 determines the three-dimensional orthogonal coordinates and Euler angles of the blade 42 based on the position of the camera 800, based on the three-dimensional orthogonal coordinates (excluding abnormal values) and the Euler angles (excluding abnormal values) calculated in steps S22 and S23. In this way, the blade attitude calculation unit 152 determines the attitude of the blade 42 with respect to the camera 800.

[0082] For example, the blade attitude calculation unit 152 calculates the average of each three-dimensional orthogonal coordinate (excluding abnormal values) to determine the three-dimensional orthogonal coordinates of the blade 42 when the camera 800 is used as the reference. The blade attitude calculation unit 152 calculates the average of each Euler angle (excluding abnormal values) to determine the Euler angle of the blade 42 when the camera 800 is used as the reference.

[0083] 2 and 3, the motor grader 1 includes the markers 711-713 attached to the drawbar 40, and a camera attached to the front frame 22 that captures images of at least the markers 711-713. The motor grader 1 further includes a controller that calculates the attitude of the drawbar 40 relative to the camera 800 based on image data of the markers 711-713 captured by the camera 800, as shown in FIG.

[0084] According to this configuration, by capturing images of the markers 711 to 713 attached to the drawbar 40 with the camera 800 attached to the front frame 22, information on the attitude of the drawbar 40 relative to the camera 800 can be obtained.

[0085] 2 and 3, the motor grader 1 further includes markers 721 and 722 attached to the blade 42. The camera 800 captures images of the markers 711 to 713 and the markers 721 and 722. The controller 150 calculates the attitude of the blade 42 with respect to the camera 800 based on the image data of the markers 721 and 721, as shown in step S2 of FIG.

[0086] According to this configuration, by capturing images of the markers 721 and 722 attached to the blade 42 with the camera 800 attached to the front frame 22, information on the attitude of the blade 42 relative to the camera 800 can be obtained.

[0087] In particular, the motor grader 1 is capable of capturing images of the multiple markers 711 to 713, 721, and 722 with a single camera 800. Therefore, the motor grader 1 does not require multiple cameras.

[0088] Controller 150 calculates the position of cutting edge 42a relative to camera 800 based on the attitude of draw bar 40 relative to camera 800 and the attitude of blade 42 relative to camera 800. According to this configuration, by capturing images of markers 711 to 713 attached to draw bar 40 and markers 721, 722 attached to blade 42 with camera 800 attached to front frame 22, information on the position of cutting edge 42a relative to camera 800 can be obtained.

[0089] Controller 150 calculates the position of cutting edge 42a relative to ball pivot 402, which serves as a connecting member, based on the position of cutting edge 42a relative to camera 800. According to this configuration, by capturing images of markers 711-713 attached to drawbar 40 and markers 721, 722 attached to blade 42 with camera 800 attached to front frame 22, information on the position of cutting edge 42a relative to ball pivot 402 can be obtained.

[0090] Camera 800 is attached to lower end surface 22u (FIG. 2) of front frame 22. With this configuration, camera 800 can capture images of markers 711-713 attached to drawbar 40 and markers 721, 722 attached to blade 42. Furthermore, front frame 22 can prevent dust from accumulating on camera 800.

[0091] Lens 801 of camera 800 is an ultra-wide-angle lens. With this configuration, markers 711 to 713 attached to drawbar 40 and markers 721 and 722 attached to blade 42 can be accommodated within the viewing angle.

[0092] Markers 711-713 are placed on the upper surface of drawbar 40. With this configuration, when markers 711-713 are imaged by camera 800, drawbar 40 can be prevented from covering markers 711-713.

[0093] The markers 721 and 722 are installed above the blade 42. With this configuration, compared to a configuration in which the markers 721 and 722 are attached somewhere other than above the blade 42, it is possible to prevent soil and sand scraped by the blade 42 from adhering to the markers 721 and 722.

[0094] <Modification> (First Modification) In the above, as shown in step S2 of Fig. 5, the attitude of the blade 42 relative to the camera 800 is calculated using two markers 721, 722 attached to the blade 42. Below, a method for calculating the attitude of the blade 42 relative to the turning center C of the turning circle 41 using multiple sensors provided on the motor grader 1 will be described. In this example, the markers 721, 722 are not necessary.

[0095] 8 is a flow diagram of this modified example for calculating the position of cutting edge 42a of blade 42. As shown in FIG. 8, in step S1, controller 150 calculates the attitude of drawbar 40 with respect to camera 800 based on images of three markers 711-713.

[0096] In step S2A, the controller 150 calculates the attitude of the blade 42 with respect to the center of rotation C of the turning circle 41 based on outputs from multiple sensors (not shown) provided in the motor grader 1. Specifically, the controller 150 calculates the attitude of the blade 42 with respect to the center of rotation C of the turning circle 41 based on outputs from a sensor (typically a potentiometer) that detects the rotation angle of the turning circle 41, a sensor that detects the stroke amount of the blade shift cylinder 47, and a sensor that detects the stroke amount of the tilt cylinder 48.

[0097] In step S3A, controller 150 calculates the position of cutting edge 42a relative to camera 800 based on the attitude of draw bar 40 relative to camera 800 calculated in step S1 and the attitude of blade 42 relative to center of rotation C of turning circle 41 calculated in step S2A. In step S4, controller 150 calculates the position of cutting edge 42a relative to ball shaft 402 based on the position of cutting edge 42a calculated in step S3A.

[0098] Fig. 9 is a flow diagram showing details of the processing of step S2A in Fig. 8. As shown in Fig. 9, in step S28, the controller 150 calculates the rotation angle of the blade 42 around the turning center C and the Euler angles of the blade 42 based on the output of a sensor that measures the rotation angle of the turning circle 41.

[0099] In step S29, the three-dimensional Cartesian coordinates of the blade 42 relative to the center of rotation C of the turning circle 41 and the Euler angles of the blade 42 are determined based on the rotation angle of the blade 42 about the center of rotation C, the output of the sensor that detects the stroke amount of the blade shift cylinder 47, and the output of the sensor that detects the stroke amount of the blade shift cylinder 47. In this way, the controller 150 calculates the attitude of the blade 42 with respect to the center of rotation C of the turning circle 41.

[0100] Even with this configuration, information on the position of the cutting edge 42a relative to the ball shaft 402 can be obtained.

[0101] (Second Modification) In step S1 of Fig. 5, the attitude (three-dimensional Cartesian coordinates and Euler angles) of the drawbar 40 relative to the camera 800 was calculated based on the images of the three markers 711 to 713. Below, a process for correcting the attitude of the drawbar 40 relative to the camera 800 will be described. Note that "correction" in this example means adjusting the attitude of the drawbar 40 calculated based on the images of the three markers 711 to 713 as described above, using the attitude of the drawbar 40 calculated by a different method, from the viewpoint of improving accuracy. Below, the different method will be described.

[0102] The controller 150 calculates the shift amount and tilt amount of the blade 42 based on the attitude of the drawbar 40 with respect to the camera 800 calculated based on the markers 711 to 713 (hereinafter referred to as the "first attitude") and the attitude of the blade 42 with respect to the camera 800 calculated based on the markers 721 and 722. The controller 150 calculates the attitude of the drawbar 40 with respect to the camera 800 (hereinafter referred to as the "second attitude") based on the calculated attitude of the blade 42 with respect to the camera 800, the calculated shift amount of the blade 42, and the calculated tilt amount of the blade 42.

[0103] Controller 150 corrects the first attitude using the second attitude. For example, controller 150 determines the average of the first attitude and the second attitude as the attitude of draw bar 40 with respect to camera 800. The correction method is not particularly limited. Controller 150 calculates the position of cutting edge 42a with respect to camera 800 using the attitude of draw bar 40 after correction instead of the "attitude of draw bar 40 with respect to camera 800" (i.e., the first attitude) in step S3 of FIG. 2.

[0104] This configuration makes it possible to accurately calculate the attitude of drawbar 40. Therefore, the position of cutting edge 42a relative to camera 800 and the position of cutting edge 42a relative to ball axis 402 can be accurately calculated.

[0105] (Third Modification) In the above description, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 when the position of the camera 800 is used as a reference, using information about the difference (offset) between the three-dimensional Cartesian coordinates (fixed values) of the marker 711 when the work implement 4 is in the neutral position and the three-dimensional Cartesian coordinates (fixed values) of the turning center C. However, it is not necessarily necessary to use the offset information.

[0106] The work machine 4 has a swivel joint (not shown) at the center of the turning circle 41. A marker (not shown) may be attached to the upper surface of the swivel joint, and the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 may be calculated by capturing an image of the marker with a camera 800.

[0107] The markers attached to the swivel joints may be damaged or contaminated, reducing the identifiability of the markers. To ensure redundancy in this case, the three-dimensional coordinates (fixed values) of the markers attached to the swivel joints and each of the markers 711 to 713 are saved in a state where each marker is sufficiently identifiable (when the vehicle is clean) when the work implement 4 is in a neutral position. This makes it possible to calculate the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 even if the markers attached to the swivel joints become unidentifiable.

[0108] The embodiments disclosed herein are merely examples and are not limited to the above. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0109] 1 motor grader, 2 body frame, 3 cab, 4 work equipment, 6 engine compartment, 11 front wheel, 12 rear wheel, 21 rear frame, 22 front frame, 22f front end, 22r base end, 22u lower end surface, 25 exterior cover, 40 draw bar, 40f front end, 40r rear end, 41 turning circle, 42 blade, 42a cutting edge, 44, 45 lift cylinder, 46 draw bar shift cylinder, 47 blade shift cylinder, 48 tilt cylinder, 49 turning motor, 50 bracket, 51 counterweight, 150 controller, 151 draw bar attitude calculation unit, 152 blade attitude calculation unit, 153 first cutting edge position calculation unit, 154 second cutting edge position calculation unit, 402 ball axis, 711 to 713, 721, 722 marker, 790 Support member, 800 camera, 801 lens, 802 main body, C swivel center, J1 central axis, J2 rotation axis, J3 central axis.

Claims

1. The front frame and a drawbar attached to the front frame so as to be able to swing; a first identification marker attached to the drawbar; a camera attached to the front frame and configured to capture an image of the first identification marker; a controller that calculates a first attitude of the drawbar with respect to the camera based on first image data of the first identification marker obtained by the imaging.

2. a turning circle pivotally attached to the drawbar; a blade supported on the pivot circle; a second identification marker attached to the blade; the camera captures an image of the first identification marker and the second identification marker; The motor grader according to claim 1 , wherein the controller calculates an attitude of the blade relative to the camera based on second image data of the second identification marker obtained by the imaging.

3. The blade has a cutting edge; The motor grader according to claim 2 , wherein the controller calculates the position of the blade tip relative to the camera based on a first attitude of the drawbar relative to the camera and an attitude of the blade relative to the camera.

4. a connecting member that swingably connects the drawbar to the front frame in front of the drawbar, The motor grader according to claim 3 , wherein the controller calculates the position of the cutting edge relative to the connecting member based on the position of the cutting edge relative to the camera.

5. the front frame has a lower end surface facing the drawbar, The motor grader according to claim 1 , wherein the camera is attached to the lower end surface.

6. The motor grader of claim 5 , wherein the camera has an ultra-wide-angle lens.

7. The motor grader according to claim 1 , wherein the first identification marker is provided on an upper surface of the drawbar.

8. The motor grader according to claim 2 , wherein the second identification marker is installed above the blade.

9. The controller calculating a shift amount of the blade and a tilt amount of the blade based on a first attitude of the drawbar with respect to the camera and an attitude of the blade with respect to the camera; 5. The motor grader according to claim 1, wherein a second attitude of the drawbar relative to the camera is calculated based on the attitude of the blade relative to the camera, a shift amount of the blade, and a tilt amount of the blade.

10. A method for calculating a drawbar attitude of a motor grader, comprising: capturing an image of an identification marker attached to a draw bar swingably connected to a front frame with a camera attached to the front frame; and calculating an attitude of the drawbar relative to the camera based on image data of the identification marker obtained by the imaging.

Images