Motor grader and method for calculating drawbar attitude of motor grader

Abstract

This motor grader comprises: a front frame; a drawbar; a connection member for swingably connecting the drawbar to the front frame in front of the drawbar; a first identification marker that is attached to a first position of the front frame near the connection member; a camera that is attached to the drawbar and is for imaging the first identification marker; and a controller for calculating the attitude of the drawbar on the basis of first image data, of the first identification marker, obtained by imaging.

Description

Motor grader and method for calculating drawbar attitude of motor grader

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

[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. The first and second cameras are mounted on a front frame.

[0004] US Patent Application Publication No. 2018 / 0061040A1

[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 limiting; 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.

[0007] A motor grader according to one aspect of the present disclosure includes a front frame, a drawbar, a connecting member in front of the drawbar that swingably connects the drawbar to the front frame, a first identification marker attached to a first position on the front frame near the connecting member, a camera attached to the drawbar that captures an image of the first identification marker, and a controller that calculates the attitude of the drawbar based on first image data of the first identification marker obtained by the image capture.

[0008] A motor grader according to another aspect 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.

[0009] According to the present disclosure, the attitude of the drawbar can be calculated using the identification marker.

[0010] 16 is a perspective view schematically showing the configuration of a motor grader. FIG. 17 is a view showing the main parts of a working machine. FIG. 18 is a view showing an image based on image data obtained by imaging with a camera when the working machine is in the state of FIG. 2. FIG. 19 is a view showing a state in which the drawbar has been moved to the right from the state of FIG. 2. FIG. 19 is a view showing an image based on image data obtained by imaging with a camera when the working machine is in the state of FIG. 4. FIG. 20 is a view showing a state in which the drawbar has been moved to the upper right from the state of FIG. 4. FIG. 21 is a view showing an image based on image data obtained by imaging with a camera when the working machine is in the state of FIG. 6. FIG. 22 is a block diagram illustrating the functional configuration of a motor grader. FIG. 23 is a flow diagram for calculating the attitude of the drawbar. FIG. 24 is a side view of the front frame side of a motor grader according to another embodiment. FIG. 25 is a plan view of the front frame side of the motor grader in the state of FIG. 10. FIG. 26 is a block diagram illustrating the functional configuration of a motor grader. FIG. 27 is a flow diagram for calculating the position of the cutting edge of the blade. FIG. 28 is a flow diagram showing details of the processing of step S10 of FIG. 13. FIG. 29 is a flow diagram showing details of the processing of step S20 of FIG. 13. FIG. 29 is a flow diagram in this modified example for calculating the position of the cutting edge of the blade. FIG. 29 is a flow diagram showing details of the processing of step S20A of FIG.

[0011] Hereinafter, motor graders according to embodiments of the present invention will be described 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 descriptions thereof will not be repeated.

[0012] [First Embodiment] Figure 1 is a perspective view that schematically shows the configuration of a motor grader 1 according to this embodiment. As shown in Figure 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.

[0013] In the following description of the drawings, 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 implement 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 implement 4 is referred to as the rear direction.

[0014] The left-right direction of the motor grader 1 is the direction perpendicular to the front-to-rear direction in a plan view. When an operator seated 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-rear 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.

[0015] The body frame 2 extends in the front-rear direction and includes a rear frame 21 and a front frame 22.

[0016] 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.

[0017] 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.

[0018] 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 with respect 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.

[0019] The two front wheels 11, for example, are rotatably attached to the front end 22f of the front frame 22. The front wheels 11 are rotatably attached 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.

[0020] 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.

[0021] 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 gear shift lever, an operating lever for the work implement 4, a brake, an accelerator pedal, an inching pedal, and various switches.

[0022] Fig. 2 is a diagram showing essential parts of the work implement 4. Fig. 2 shows a state in which the work implement 4 is in a neutral position. Note that the "state in which the work implement 4 is in a 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 of the draw bar 40 in the fore-and-aft direction. In other words, the "state in which the work implement 4 is in a 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 of the front frame 22 in the fore-and-aft direction.

[0023] 2 , 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 shaft 402. The rear end 40r of the drawbar 40 is supported on the front frame 22 by lift cylinders 44, 45. The ball shaft 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 (not shown), 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.

[0027] The lift cylinders 44, 45 are attached to the draw bar 40 and a 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 to turn relative to the draw bar 40 in both clockwise and counterclockwise directions as viewed from above the vehicle. The turning circle 41 rotates in the direction of arrow 902. The turning circle 41 rotates in the direction of arrow 902 relative to the draw bar 40 about a rotation axis J2.

[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 on the draw bar 40 via the turning circle 41. The blade 42 is supported on 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. The blade 42 makes a stroke in the direction of the arrow 901. The blade 42 rotates about the rotation axis J2 in accordance with the revolving drive of the revolving circle 41.

[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 allows 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 the axis extending in the longitudinal direction of the blade 42 relative to the turning circle 41, thereby changing 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).

[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 701 to 703. In this example, each of the identification markers 701 to 703 is a subject of the camera 800. Note that the number of markers is not limited to three, and may be one, two, four or more.

[0036] The camera 800 has a lens 801 and a main body 802 that has an image sensor built in. The lens 801 has an angle of view that allows at least one of the three markers 701 to 703 to be in the field of view regardless of the attitude of the work machine 4.

[0037] The camera 800 is attached to the upper surface of the drawbar 40. When the work implement 4 is in the neutral position, the camera 800 is located directly below the front frame 22. The camera 800 is located on the central axis J1 of the drawbar 40.

[0038] The camera 800 is located between the front end 40f and the rear end 40r of the drawbar 40. The camera 800 is located forward of the turning circle 41. The camera 800 is attached to the drawbar 40 so that the optical axis of the camera 800 is parallel to the central axis J1. The camera 800 is attached to the drawbar 40 so that the lens 801 is forward of the main body 802.

[0039] Each of the markers 701 to 703 is attached to the front frame 22. Each of the markers 701 to 703 is attached to the front end portion 22 f of the front frame 22. Each of the markers 701 to 703 is attached in front of the draw bar 40. Each of the markers 701 to 703 is attached near the ball shaft 402.

[0040] Each of the markers 701 to 703 has a plurality of regions (cells) arranged in a matrix, with some of the regions painted black. Each of the markers 701 to 703 has a pattern made up of a plurality of white cells and a plurality of black cells. The pattern of the marker 701, the pattern of the marker 702, and the pattern of the marker 703 are different from one another. Each pattern is created on the surface of a plate-like member or attached to the surface. Note that these patterns are not shown in FIG. 2 and FIGS. 4 to 7, which will be described later.

[0041] The marker 701 is attached to a first predetermined position on the front frame 22, which is near the ball axle 402. The first predetermined position is above the ball axle 402. The marker 701 is provided above the ball axle 402. In this example, the marker 701 is provided directly above the ball axle 402. The marker 701 is provided on the underside of the front frame 22, midway between the left and right front wheels 11.

[0042] Marker 702 is attached to a second predetermined position on the front frame 22 near the ball pivot 402. The second predetermined position is on the right side of the ball pivot 402. Marker 703 is attached to a third predetermined position on the front frame 22 near the ball pivot 402. The third predetermined position is on the left side of the ball pivot 402. In this example, the second predetermined position and the third predetermined position are line-symmetrical with respect to the front frame 22 in a plan view of the work machine 4.

[0043] More specifically, the marker 701 is attached to the front frame 22 in an inclined state, following the shape of the lower surface of the front frame 22. The marker 701 is inclined so that the further away from the ball axis 402 the marker 701 is, the more rearward the marker 701 is from the front frame 22.

[0044] Marker 702 and marker 703 are in a line-symmetric relationship with respect to front frame 22 in a plan view of work machine 4. Like marker 701, markers 702 and 703 are attached to front frame 22 in an inclined state so that the further away from ball pivot 402 they are, the more rearward they are on the front frame 22. The reason each of markers 701 to 703 is inclined as described above is so that each of markers 701 to 703 faces camera 800 when work machine 4 is in a neutral state.

[0045] Each of the markers 701 to 703 is attached to the front frame 22. Therefore, the position (relative position) of each of the markers 701 to 703 with respect to the front frame 22 and the ball shaft 402 does not change. On the other hand, the camera 800 is attached to the drawbar 40. Therefore, when at least the attitude of the drawbar 40 changes, the position (relative position) of each of the markers 701 to 703 with respect to the camera 800 changes.

[0046] In this example, AR (Augmented Reality) markers are used as the markers 701 to 703. However, the markers 701 to 703 are not limited to AR markers. Any markers may be used as long as they can be distinguished from one another.

[0047] It is sufficient that the identifier of each marker 701 to 703 and the orientation of each marker 701 to 703 when the camera 800 is used as a reference can be determined. Specifically, with regard to the orientation of each marker 701 to 703, it is sufficient that the position (position in a three-dimensional Cartesian coordinate system) and the tilt state (Euler angle) of each marker 701 to 703 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 below, based on image data acquired by the camera 800.

[0048] The above-described arrangement of the markers 701 to 703 is an example and is not limited to the above. The ball axle 402 is an example of a "connecting member" in the present disclosure. Any one of the three markers 701 to 703 attached to the front frame 22 is an example of a "first identification marker" in the present disclosure. Any one of the remaining two markers 701 to 703 is an example of a "second identification marker" in the present disclosure.

[0049] Fig. 3 is a diagram showing an image based on image data obtained by imaging by camera 800 when work machine 4 is in the state shown in Fig. 2. As shown in Fig. 3, image 102G includes image 22G of front frame 22, image 40G of drawbar 40, image 402G of ball shaft 402, image 701G of marker 701, image 702G of marker 702, and image 703G of marker 703.

[0050] The entire marker 701 is captured. However, because the drawbar 40 is positioned closer to the camera 800 than the markers 702 and 703, the entire markers 702 and 703 are not captured. The lower left portion of the marker 702 is not captured. The lower right portion of the marker 703 is not captured.

[0051] The virtual line L is a line segment that equally divides the left and right sides of the image 102G. Because the work machine 4 is in a neutral state, the image 701G is located in the center of the left and right sides of the image 102G. The image 701G is symmetrical with respect to the virtual line L. Because the work machine 4 is in a neutral state, the positions of the images 702G and 703G within the image 102G are symmetrical with respect to the virtual line L.

[0052] The posture of the drawbar 40 is calculated based on image data obtained by imaging with the camera 800, as will be described in detail later.

[0053] Fig. 4 is a diagram showing a state in which the drawbar 40 is moved to the right from the state in Fig. 2. As shown in Fig. 4, the positions (relative positions) of the markers 701 to 703 with respect to the camera 800 change from the positions shown in Fig. 2. In this way, the movement of the drawbar 40 changes the positions of the markers 701 to 703 relative to the position of the camera 800.

[0054] Fig. 5 is a diagram showing an image based on image data obtained by imaging by camera 800 when work machine 4 is in the state shown in Fig. 4. As shown in Fig. 5, image 104G includes image 22G, image 40G, image 402G, image 701G, image 702G, and image 703G, similar to image 102G shown in Fig. 3. Image 104G further includes image 51G of counterweight 51.

[0055] 5, at least the postures of the images 701G to 703G of the markers 701 to 703 have changed compared to the image 102G shown in Fig. 3. Specifically, the positions and shapes of the images 701G to 703G in the image (more specifically, image data) have changed from the positions and shapes of the images 701G to 703G shown in Fig. 3.

[0056] Fig. 6 is a diagram showing a state in which the drawbar 40 has been moved to the upper right from the state in Fig. 4. As shown in Fig. 6, the positions (relative positions) of the markers 701 to 703 with respect to the camera 800 further change from the positions shown in Fig. 4. In this case, the entire marker 702 is located in front of the drawbar 40, and the marker 702 is not visible from the camera 800. The marker 702 is not captured by the camera 800.

[0057] Fig. 7 is a diagram showing an image based on image data obtained by imaging by camera 800 when work machine 4 is in the state shown in Fig. 6. As shown in Fig. 7, image 106G includes image 22G, image 40G, image 402G, image 701G, and image 703G. Unlike images 102G and 104G, image 106G does not include image 702G of marker 702.

[0058] 7, at least the postures of the images 701G and 703G of the markers 701 and 703 are different from those of the images 102G and 104G shown in Figures 3 and 5. Specifically, the positions and shapes of the images 701G and 703G in the image (more specifically, image data) are changed from those of the images 701G and 703G shown in Figures 3 and 5.

[0059] 8 and 9, a method for calculating the attitude of drawbar 40 from image data obtained by capturing images of markers 701 to 703 with camera 800 will be described below. Furthermore, a process for calculating the attitude of blade 42 and the position of cutting edge 42a (FIG. 2) of blade 42 based on the calculated attitude of drawbar 40 will also be described.

[0060] It should be noted that if image data of at least one of the three markers 701 to 703 is obtained, it is possible to calculate the attitude of the drawbar 40. If image data of two or more markers is obtained, it is possible to calculate the attitude of the drawbar 40 with higher accuracy.

[0061] Figure 8 is a block diagram illustrating the functional configuration of the motor grader 1. As shown in Figure 8, the motor grader 1 includes a camera 800, a turning circle 41, a blade shift cylinder 47, a tilt cylinder 48, and a controller 150. The motor grader 1 also includes a sensor (not shown) that detects the rotation angle of the turning circle 41 (hereinafter referred to as "sensor #1"), a sensor (not shown) that detects the stroke amount of the blade shift cylinder 47 (hereinafter referred to as "sensor #2"), and a sensor (not shown) that detects the stroke amount of the tilt cylinder 48 (hereinafter referred to as "sensor #3"). Note that a potentiometer can be used as sensor #1.

[0062] The controller 150 has a drawbar attitude calculation unit 151, a blade attitude calculation unit 152, and a cutting edge position calculation unit 153. The drawbar attitude calculation unit 151, the blade attitude calculation unit 152, and the cutting edge position calculation unit 153 are functional block diagrams that are typically implemented 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, and the cutting edge position calculation unit 153 may be implemented only by hardware (integrated circuits) such as an ASIC.

[0063] 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. Note that the period in which the drawbar attitude calculation unit 151 acquires image data from the camera 800 does not have to be the same as the period in which the drawbar attitude calculation unit 151 calculates the attitude of the drawbar 40. The processing of the drawbar attitude calculation unit 151 will be described below.

[0064] 9 is a flowchart for explaining the flow of processing in the drawbar attitude calculation unit 151. FIG. 9 is a flowchart for calculating the attitude of the drawbar 40.

[0065] 9 , in step S1, the drawbar attitude calculation unit 151 calculates the three-dimensional orthogonal coordinates and Euler angles of each of the markers 701, 702, and 703 based on image data acquired from the camera 800. Specifically, the drawbar attitude calculation unit 151 calculates the three-dimensional orthogonal coordinates and Euler angles of each of the markers 701, 702, and 703 from the image data based on the three-dimensional orthogonal coordinates (fixed values) of each of the markers 701, 702, and 703 and the Euler angles (fixed values) of each of the markers 701, 702, and 703 when the work implement 4 is in the neutral position. Note that the fixed values ​​are stored in advance in the controller 150. Each fixed value, which will be described later, is also stored in advance in the controller 150.

[0066] 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.

[0067] In step S2, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the center of the ball axis 402 when the camera 800 is used as a reference and the Euler angles of the ball axis 402 based on the three-dimensional Cartesian coordinates of the marker 701 and the Euler angles of the marker 701. The drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates and the Euler angles using the position of the camera 800 as a reference. 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 701 and the Euler angles (fixed values) of the marker 701 when the work implement 4 is in the neutral position.

[0068] Similarly, in step S3, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the center of the ball axis 402 when the camera 800 is used as a reference and the Euler angles of the ball axis 402, based on the three-dimensional Cartesian coordinates and Euler angles of the marker 702. 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 702 and the Euler angles (fixed values) of the marker 702 when the work implement 4 is in the neutral position.

[0069] In step S4, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the center of the ball axis 402 when the camera 800 is used as a reference and the Euler angles of the ball axis 402 based on the three-dimensional Cartesian coordinates and Euler angles of the marker 703. 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 703 and the Euler angles (fixed values) of the marker 703 when the work implement 4 is in the neutral position. The order of steps S2, S3, and S4 is not particularly limited.

[0070] In step S5, the drawbar attitude calculation unit 151 determines whether or not the three-dimensional orthogonal coordinates and the Euler angles calculated in steps S2 to S4 contain abnormal values. Specifically, the drawbar attitude calculation unit 151 determines whether or not the three-dimensional orthogonal coordinates fall within a preset coordinate range. The drawbar attitude calculation unit 151 determines whether or not the Euler angles fall within a preset Euler angle range. More specifically, the drawbar attitude calculation unit 151 determines whether or not each of the three independent variables 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.

[0071] If it is determined that no abnormal values ​​are included (NO in step S5), the drawbar attitude calculation unit 151 proceeds to step S6. If it is determined that an abnormal value is included (YES in step S5), the drawbar attitude calculation unit 151 deletes the abnormal value in step S8 to improve accuracy. The drawbar attitude calculation unit 151 then proceeds to step S6.

[0072] In step S6, based on the three-dimensional orthogonal coordinates (excluding abnormal values) and the Euler angles (excluding abnormal values) calculated in steps S2 to S4, the drawbar attitude calculation unit 151 determines the coordinates of the center of ball axis 402 when camera 800 is used as the reference and the Euler angles of ball axis 402. For example, the drawbar attitude calculation unit 151 calculates the average of the three-dimensional orthogonal coordinates (excluding abnormal values) to determine the coordinates of the center of ball axis 402 when camera 800 is used as the reference. The drawbar attitude calculation unit 151 calculates the average of the Euler angles (excluding abnormal values) to determine the Euler angles of ball axis 402 when camera 800 is used as the reference.

[0073] In step S7, drawbar attitude calculation unit 151 converts the three-dimensional Cartesian coordinates and Euler angles determined in step S6 into three-dimensional Cartesian coordinates and Euler angles based on the center of ball axis 402, thereby calculating the attitude of drawbar 40. Drawbar attitude calculation unit 151 performs inverse conversion using a predetermined arithmetic expression to calculate the attitude of drawbar 40 based on the center of ball axis 402.

[0074] As described above, the attitude of the drawbar 40 is calculated from the image data obtained by capturing an image with the camera 800. The calculation of the attitude of the drawbar 40 is periodically executed as described above. Information on the calculated attitude of the drawbar 40 (hereinafter also referred to as "drawbar attitude information") is periodically sent to the blade attitude calculation unit 152, as shown in FIG.

[0075] Next, the processing of the blade attitude calculation unit 152 will be described. The blade attitude calculation unit 152 periodically acquires drawbar attitude information from the drawbar attitude calculation unit 151. The blade attitude calculation unit 152 periodically acquires information on the rotation angle of the turning circle 41 from the above-mentioned sensor #1. The blade attitude calculation unit 152 acquires information indicating the stroke amount of the blade shift cylinder 47 from the above-mentioned sensor #2. The blade attitude calculation unit 152 acquires information indicating the stroke amount of the tilt cylinder 48 from the above-mentioned sensor #3.

[0076] The blade attitude calculation unit 152 periodically calculates the attitude of the blade 42 based on the drawbar attitude information, information on the rotation angle of the turning circle 41, information indicating the stroke amount of the blade shift cylinder 47, and information indicating the stroke amount of the tilt cylinder 48. The blade attitude calculation unit 152 periodically sends information indicating the calculated blade attitude (hereinafter referred to as “blade attitude information”) to the cutting edge position calculation unit 153.

[0077] When the blade attitude information is acquired from the blade attitude calculation unit 152, the cutting edge position calculation unit 153 calculates the position of the cutting edge 42a of the blade 42 based on the blade attitude information. The cutting edge position calculation unit 153 calculates the position of the cutting edge 42a based on the blade attitude information and a predetermined design value. The calculated position information of the cutting edge 42a is used for various processes in the controller 150.

[0078] As described above, the motor grader 1 includes, as shown in Fig. 2 and other figures, a marker 701 attached to a first predetermined position on the front frame 22 near the ball pivot 402, a marker 702 attached to a second predetermined position on the front frame 22 near the ball pivot 402, and a marker 703 attached to a third predetermined position on the front frame 22 near the ball pivot 402. As shown in Fig. 2 and other figures, the motor grader 1 further includes a camera 800 attached to the drawbar 40 and capturing images of the markers 701 to 703. As shown in Fig. 8, the motor grader 1 further includes a controller 150 that calculates the attitude of the drawbar 40 based on image data of the markers 701 to 703 obtained by capturing the images.

[0079] According to this configuration, by capturing images of the markers 701 to 703 attached to the front frame 22 with the camera 800 attached to the drawbar 40, information on the attitude of the drawbar 40 can be obtained.

[0080] In particular, with the motor grader 1, multiple markers 701-703 can be captured with a single camera 800. Therefore, the motor grader 1 does not require multiple cameras. The markers 701-703 are attached near the ball axis 402. Therefore, soil and sand scraped by the blade 42 are less likely to adhere to the markers 701-703. Therefore, the markers 701-703 are less likely to become dirty. Therefore, with the motor grader 1, there is little risk of the markers 701-703 failing to be read. Furthermore, the front frame 22 is located above the ball axis 402. Therefore, the front frame 22 can prevent dust from accumulating on the markers 701-703.

[0081] 4 and 6, the motor grader 1 is a work machine that can assume a work machine posture with a very high degree of freedom. However, by arranging the markers 701 to 703 near the ball axis 402, the markers 701 to 703 can be captured by the camera 800 attached to the drawbar 40 even if the posture of the work machine 4 changes in various ways. Therefore, the motor grader 1 can obtain information on the posture of the drawbar 40.

[0082] Although the above description has been given using an example of a configuration in which the motor grader 1 is equipped with three markers 701 to 703, the present invention is not limited to this. The motor grader 1 may be equipped with at least one marker. It is preferable that the motor grader 1 is equipped with at least the central marker 701 in the left-right direction. However, by providing multiple markers 701 to 703, redundancy can be ensured in the event of marker dirt or damage, and the "posture of the drawbar 40" can be calculated with high accuracy (step S6 in FIG. 9).

[0083] The attitude of the drawbar 40 is the attitude of the drawbar 40 with respect to the ball axis 402. As shown in step S6 of Fig. 9, the controller 150 calculates the attitude of the ball axis 402 with respect to the camera 800 based on the image data of each of the markers 701 to 703. As shown in step S7 of Fig. 9, the controller 150 calculates the attitude of the drawbar 40 with respect to the ball axis 402 based on the attitude of the ball axis 402 with respect to the camera 800.

[0084] With this configuration, it is possible to calculate the attitude of the drawbar 40 with respect to the ball shaft 402 based on image data obtained by imaging using the camera 800 attached to the drawbar 40 .

[0085] Camera 800 is attached to the top surface of drawbar 40. This configuration makes it possible to prevent soil and sand scraped by blade 42 from adhering to camera 800, compared to a configuration in which camera 800 is attached to the side or bottom of drawbar 40. Furthermore, this configuration makes it possible to fit at least one of markers 701 to 703 within the angle of view of camera 800, even if the posture of work machine 4 changes in various ways.

[0086] As shown in Figures 1 and 2, the motor grader 1 further includes a slewing circle 41 that supports a blade 42 and is slewingably attached to the drawbar 40. As shown in Figure 2, the drawbar 40 has a front end 40f that is connected to a ball shaft 402. As shown in Figure 2, the camera 800 is located on a central axis J1 of the drawbar 40 that extends from the front end 40f in a direction toward the slewing center C of the slewing circle 41. More specifically, the optical axis of a lens 801 of the camera 800 is located on the central axis J1 of the drawbar 40. The optical axis is parallel to the central axis J1.

[0087] With this configuration, the camera 800 is positioned on the central axis J1 of the drawbar 40, so the camera 800 can capture an image of the periphery of the ball axis 402 regardless of the attitude of the drawbar 40. Therefore, it becomes possible to capture an image of at least one of the three markers 701 to 703.

[0088] Furthermore, when the motor grader 1 is parked with the work implement 4 in the neutral position, the front frame 22 is located directly above the camera 800. Therefore, dust accumulation on the camera 800 can be suppressed compared to when the front frame 22 is not located above the camera 800.

[0089] [Embodiment 2] Next, a motor grader 1A (see Figure 1) according to this embodiment will be described. Figure 10 is a side view of the front frame 22 side of the motor grader 1A. Figure 11 is a plan view of the front frame 22 side of the motor grader 1A in the state shown in Figure 10. Figures 10 and 11 show a state in which the work implement 4 is in the neutral position.

[0090] When the work implement 4 is in the neutral position, the central axis J1 overlaps with the central axis J3 (FIG. 11) which is the axis of the front frame 22 in the fore-and-aft direction in a plan view (top view) of the motor grader 1A.

[0091] The motor grader 1A further includes a camera 800A 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 800A.

[0092] The camera 800A has a lens 801A and a main body 802A with a built-in image sensor. The lens 801A has an angle of view that brings the five markers 711 to 713, 721, and 722 into view regardless of the attitude of the work machine 4. The lens 801A is a wide-angle lens. Preferably, the lens 801A is an ultra-wide-angle lens. In this example, the lens 801A is a fisheye lens, which is a type of wide-angle lens.

[0093] The front frame 22 further has a lower end surface 22u that faces the drawbar 40. The camera 800A is attached to the lower end surface 22u. The camera 800A is attached to the lower end surface 22u so that the optical axis of the lens 801A faces vertically downward. In this example, in a plan view of the motor grader 1A, the camera 800A 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 1A ( FIG. 10 ), the camera 800A is located between the front end 40f and the rear end 40r of the drawbar 40.

[0094] 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.

[0095] However, by attaching multiple markers 711-713 to the drawbar 40, redundancy can be ensured against marker contamination and damage, and the "attitude of the drawbar 40 relative to the camera 800A" described later can be calculated with high accuracy (step S10 in FIG. 13, particularly step S16 in FIG. 14). Similarly, by attaching multiple markers 721 and 722 to the blade 42, redundancy can be ensured against marker contamination and damage, and the "attitude of the blade 42 relative to the camera 800A" described later can be calculated with high accuracy (step S20 in FIG. 13, particularly step S25 in FIG. 15).

[0096] Each of the markers 711 to 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 to 713, 721, and 722 has a pattern consisting 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 affixed to that surface. Details of the attachment positions of the markers 711 to 713, 721, and 722 are described below using specific examples.

[0097] The markers 711 to 713 are attached to the upper surface of the drawbar 40. The markers 711 to 713 are attached to the drawbar 40 so that the markers 711 to 713 (more specifically, the patterns) face upward at least when the drawbar 40 is in the neutral position.

[0098] The marker 711 is installed in front of the camera 800A in a plan view of the motor grader 1A. 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 1A.

[0099] The markers 712 and 713 are installed behind the camera 800A in a plan view of the motor grader 1A. 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.

[0100] The installation positions of the markers 711 to 713 are not limited to the above positions. As long as the markers are located in positions that can be imaged by the camera 800A, there are no particular limitations on the installation positions of the markers 711 to 713. However, from the perspective 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.

[0101] The markers 721 and 722 are attached to the blade 42. The markers 721 and 722 are attached above the blade 42. The markers 721 and 722 are attached to the blade 42 by a support member 790. The markers 721 and 722 are installed at positions spaced apart from the upper end surface of the blade 42. The markers 721 and 722 are located rearward of the three markers 711 to 713 attached to the drawbar 40, at least when the work implement 4 is in the neutral position.

[0102] 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 installed at a position symmetrical to marker 721 with respect to the center of blade 42 in the direction of arrow 901.

[0103] 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.

[0104] The installation positions of the markers 721 and 722 are not limited to the above positions. As long as the markers 721 and 722 are located in positions that can be imaged by the camera 800A, there are no particular limitations on the installation positions of the markers 721 and 722. 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.

[0105] 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.

[0106] On the other hand, camera 800A is attached to front frame 22. Therefore, when the attitude of at least drawbar 40 changes, the positions (relative positions) of markers 711 to 713, 721, and 722 with respect to camera 800A 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 800A change.

[0107] 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. They may be any markers as long as they can be distinguished from one another.

[0108] It is sufficient that the identifier of each marker 711-713, 721, and 722 and the orientation of each marker 711-713, 721, and 722 when the camera 800A is used as a reference can be determined. Specifically, with regard to the orientation of each marker 711-713, 721, and 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, and 722 when the camera 800A is used as a reference can be determined. Note that this determination is performed by the controller 150A (more specifically, a processor) described below based on image data acquired by the camera 800A.

[0109] The markers 711 to 713 attached to the drawbar 40 correspond to the "first identification marker" in the present disclosure. The markers 721 and 722 attached to the blade 42 correspond to the "second identification marker" in the present disclosure.

[0110] Fig. 12 is a block diagram illustrating the functional configuration of the motor grader 1A. As shown in Fig. 12, the motor grader 1A includes a camera 800A and a controller 150A. The controller 150A includes a drawbar attitude calculation unit 151A, a blade attitude calculation unit 152A, a first cutting edge position calculation unit 153A, and a second cutting edge position calculation unit 154.

[0111] The drawbar attitude calculation unit 151A, the blade attitude calculation unit 152A, the first cutting edge position calculation unit 153A, and the second cutting edge position calculation unit 154 are typically functional block diagrams that are implemented by a processor (not shown) executing a program. However, without being limited to this, the drawbar attitude calculation unit 151A, the blade attitude calculation unit 152A, the first cutting edge position calculation unit 153A, and the second cutting edge position calculation unit 154 may be implemented only by hardware (integrated circuits) such as an ASIC.

[0112] The drawbar attitude calculation unit 151A periodically acquires image data obtained by imaging with the camera 800A from the camera 800A. The drawbar attitude calculation unit 151A periodically calculates the attitude of the drawbar 40 based on the acquired image data. The drawbar attitude calculation unit 151A calculates the attitude of the drawbar 40 when the camera 800A 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.

[0113] The drawbar attitude calculation unit 151A periodically sends the calculated attitude (predicted position) of the drawbar 40 to the first cutting edge position calculation unit 153A. Note that the cycle in which the drawbar attitude calculation unit 151A acquires image data from the camera 800A does not have to be the same as the cycle in which the drawbar attitude calculation unit 151A calculates the attitude of the drawbar 40. Details of the processing by the drawbar attitude calculation unit 151A will be described later.

[0114] The blade orientation calculation unit 152A periodically acquires image data obtained by imaging with the camera 800A from the camera 800A. Based on the acquired image data, the blade orientation calculation unit 152A periodically calculates the orientation of the blade 42. The blade orientation calculation unit 152A calculates the orientation of the blade 42 when the camera 800A 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.

[0115] The blade attitude calculation unit 152A periodically sends the calculated attitude (predicted position) of the blade 42 to the first cutting edge position calculation unit 153A. Note that the cycle in which the blade attitude calculation unit 152A acquires image data from the camera 800A does not have to be the same as the cycle in which the blade attitude calculation unit 152A calculates the attitude of the blade 42. Details of the processing by the blade attitude calculation unit 152A will be described later.

[0116] First cutting edge position calculation unit 153A calculates the position of cutting edge 42a relative to camera 800A, based on the attitude (predicted position) of drawbar 40 and the attitude (predicted position) of blade 42, which are periodically received. Note that the calculation of the position of cutting edge 42a is performed periodically. After calculating the position of cutting edge 42a, first cutting edge position calculation unit 153A sends information indicating the calculated position of cutting edge 42a to second cutting edge position calculation unit 154.

[0117] 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 153A indicating the position of the cutting edge 42a relative to the camera 800A. The information on the position of the cutting edge 42a calculated by the second cutting edge position calculation unit 154 is used for various processes in the controller 150A.

[0118] Fig. 13 is a flow diagram for calculating the position of cutting edge 42a of blade 42. As shown in Fig. 13, in step S10, controller 150A calculates the attitude of drawbar 40 with respect to camera 800A based on images of markers 711 to 713 attached to drawbar 40. Drawbar attitude calculation unit 151A of controller 150A calculates the attitude of drawbar 40 when the position of camera 800A is used as a reference.

[0119] In step S20, controller 150A calculates the attitude of blade 42 with respect to camera 800A based on images of markers 721, 722 attached to blade 42. Drawbar attitude calculation unit 151A of controller 150A calculates the attitude of blade 42 when the position of camera 800A is used as a reference.

[0120] In step S30, controller 150A calculates the position of cutting edge 42a relative to camera 800A based on the attitude of drawbar 40 relative to camera 800A calculated in step S10 and the attitude of blade 42 relative to camera 800A calculated in step S20. First cutting edge position calculation unit 153A calculates the position of cutting edge 42a when the position of camera 800A is used as a reference.

[0121] In step S40, based on the position of the cutting edge 42a calculated in step S30, the controller 150A calculates the position of the cutting edge 42a relative to the ball axis 402. The second cutting edge position calculation unit 154 calculates the position of the cutting edge 42a when the position of the ball axis 402 is used as a reference.

[0122] FIG. 14 is a flow diagram showing details of the processing of step S10 in FIG. 13. As shown in FIG. 14, in step S11, the drawbar attitude calculation unit 151A 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. Specifically, the drawbar attitude calculation unit 151A 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 150A. Each of the fixed values ​​described below is also stored in advance in the controller 150A.

[0123] 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.

[0124] 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 151A calculates the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 when the position of the camera 800A is used as a reference, and the Euler angles of the turning circle 41. In detail, the drawbar attitude calculation unit 151A 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.

[0125] More specifically, the drawbar attitude calculation unit 151A calculates the three-dimensional orthogonal coordinates of the turning center C of the turning circle 41 when the position of the camera 800A is used as a reference, using information about the difference (offset) between the three-dimensional orthogonal coordinates (fixed values) of the marker 711 when the work implement 4 is in the neutral position and the three-dimensional orthogonal coordinates (fixed values) of the turning center C. This also applies to the processing in steps S13 and S14 described later.

[0126] 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 151A calculates the three-dimensional Cartesian coordinates of the turning center C of the turning circle 41 when the position of the camera 800A is used as a reference, and the Euler angles of the turning circle 41. In detail, the drawbar attitude calculation unit 151A 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.

[0127] In step S14, the drawbar attitude calculation unit 151A calculates the three-dimensional orthogonal coordinates of the turning center C of the turning circle 41 when the position of the camera 800A is used as a reference, and the Euler angles of the turning circle 41, based on the three-dimensional orthogonal coordinates and Euler angles of the marker 713 calculated in step S11. In detail, the drawbar attitude calculation unit 151A calculates the three-dimensional orthogonal coordinates and the Euler angles using information on the three-dimensional orthogonal coordinates (fixed values) of the marker 713, the Euler angles (fixed values) of the marker 713, and the three-dimensional orthogonal coordinates (fixed values) of the turning center C when the work implement 4 is in the neutral position. Note that the order of steps S12, S13, and S14 is not particularly limited.

[0128] In step S15, the drawbar attitude calculation unit 151A 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 151A determines whether or not each of the three-dimensional orthogonal coordinates falls within a preset coordinate range. The drawbar attitude calculation unit 151A determines whether or not each of the Euler angles falls within a preset Euler angle range. More specifically, the drawbar attitude calculation unit 151A determines whether or not each of the three independent variables described above falls within a preset range. The drawbar attitude calculation unit 151A determines that three-dimensional coordinates and Euler angles that do not fall within the preset ranges are abnormal values.

[0129] If it is determined that no abnormal values ​​are included (NO in step S15), the drawbar attitude calculation unit 151A proceeds to step S16. If it is determined that an abnormal value is included (YES in step S15), the drawbar attitude calculation unit 151A deletes the abnormal value to improve accuracy in step S17. The drawbar attitude calculation unit 151A then proceeds to step S16.

[0130] In step S16, based on the three-dimensional orthogonal coordinates (excluding abnormal values) and the Euler angles (excluding abnormal values) calculated in steps S12 to S14, the drawbar attitude calculation unit 151A 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 800A is used as a reference. In this way, the drawbar attitude calculation unit 151A determines the attitude of the drawbar 40 with respect to the camera 800A.

[0131] For example, the drawbar attitude calculation unit 151A 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 800A is used as the reference. The drawbar attitude calculation unit 151A calculates the average of each Euler angle (excluding abnormal values) to determine the Euler angles of the turning circle 41 when the camera 800A is used as the reference.

[0132] Fig. 15 is a flow diagram showing details of the processing of step S20 in Fig. 13. As shown in Fig. 15, in step S21, the blade attitude calculation unit 152A 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.

[0133] In step S22, the blade attitude calculation unit 152A calculates the position of the blade 42 relative to the position of the camera 800A and the Euler angles of the blade 42, 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 152A 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.

[0134] In step S23, the blade attitude calculation unit 152A calculates the position of the blade 42 relative to the position of the camera 800A 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 152A 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.

[0135] In step S24, the blade attitude calculation unit 152A 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 152A determines whether or not the three-dimensional orthogonal coordinates fall within a predetermined coordinate range. The blade attitude calculation unit 152A determines whether or not the Euler angles fall within a predetermined Euler angle range. More specifically, the blade attitude calculation unit 152A determines whether or not each of the three independent variables described above falls within a predetermined range. The blade attitude calculation unit 152A determines that three-dimensional coordinates and Euler angles that do not fall within the predetermined ranges are abnormal values.

[0136] If it is determined that no abnormal values ​​are included (NO in step S24), the blade attitude calculation unit 152A proceeds to step S25. If it is determined that an abnormal value is included (YES in step S24), the blade attitude calculation unit 152A deletes the abnormal values ​​to improve accuracy in step S26. The blade attitude calculation unit 152A then proceeds to step S25.

[0137] In step S25, the blade attitude calculation unit 152A determines the three-dimensional orthogonal coordinates and Euler angles of the blade 42 relative to the position of the camera 800A, 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 152A determines the attitude of the blade 42 with respect to the camera 800A.

[0138] For example, the blade attitude calculation unit 152A 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 800A is used as the reference. The blade attitude calculation unit 152A calculates the average of each Euler angle (excluding abnormal values) to determine the Euler angles of the blade 42 when the camera 800A is used as the reference.

[0139] 10 and 11, the motor grader 1A includes the markers 711 to 713 attached to the drawbar 40, and a camera attached to the front frame 22 that captures images of at least the markers 711 to 713. As shown in FIG. 12, the motor grader 1A further includes a controller that calculates the attitude of the drawbar 40 relative to the camera 800A based on image data of the markers 711 to 713 obtained by imaging by the camera 800A.

[0140] According to this configuration, by capturing images of the markers 711 to 713 attached to the drawbar 40 with the camera 800A attached to the front frame 22, it is possible to obtain information on the attitude of the drawbar 40 relative to the camera 800A.

[0141] 10 and 11, the motor grader 1A further includes markers 721 and 722 attached to the blade 42. The camera 800A captures images of the markers 711 to 713 and the markers 721 and 722. As shown in step S20 of FIG. 13, the controller 150A calculates the attitude of the blade 42 with respect to the camera 800A based on the image data of the markers 721 and 721.

[0142] With this configuration, by capturing images of the markers 721, 722 attached to the blade 42 with the camera 800A attached to the front frame 22, information on the attitude of the blade 42 relative to the camera 800A can be obtained.

[0143] In particular, with the motor grader 1A, a single camera 800A can capture images of multiple markers 711 to 713, 721, and 722. Therefore, the motor grader 1A does not require multiple cameras.

[0144] Controller 150A calculates the position of cutting edge 42a relative to camera 800A based on the attitude of drawbar 40 relative to camera 800A and the attitude of blade 42 relative to camera 800A. With this configuration, by capturing images of markers 711 to 713 attached to drawbar 40 and markers 721, 722 attached to blade 42 with camera 800A attached to front frame 22, information on the position of cutting edge 42a relative to camera 800A can be obtained.

[0145] Controller 150A calculates the position of cutting edge 42a relative to ball axis 402, which serves as a connecting member, based on the position of cutting edge 42a relative to camera 800A. With this configuration, by capturing images of markers 711 to 713 attached to drawbar 40 and markers 721, 722 attached to blade 42 with camera 800A attached to front frame 22, information on the position of cutting edge 42a relative to ball axis 402 can be obtained.

[0146] Camera 800A is attached to lower end surface 22u (FIG. 10) of front frame 22. With this configuration, camera 800A can capture images of markers 711 to 713 attached to drawbar 40 and markers 721 and 722 attached to blade 42. Furthermore, front frame 22 can prevent dust from accumulating on camera 800A.

[0147] Lens 801A of camera 800A 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.

[0148] Markers 711 to 713 are placed on the upper surface of drawbar 40. With this configuration, when markers 711 to 713 are imaged by camera 800A, drawbar 40 can be prevented from being covered by markers 711 to 713.

[0149] 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.

[0150] <Modifications> (First Modification) In the above, as shown in step S20 of Fig. 13, the attitude of the blade 42 relative to the camera 800A is calculated using two markers 721, 722 attached to the blade 42. Below, a method will be described in which the attitude of the blade 42 relative to the turning center C of the turning circle 41 is calculated using multiple sensors provided on the motor grader 1A. In this example, the markers 721, 722 are not necessary.

[0151] 16 is a flow diagram of this modified example for calculating the position of cutting edge 42a of blade 42. As shown in FIG. 16, in step S10, controller 150A calculates the attitude of drawbar 40 with respect to camera 800A based on images of three markers 711 to 713.

[0152] In step S20A, the controller 150A 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 plurality of sensors (not shown) provided in the motor grader 1A. Specifically, the controller 150A 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.

[0153] In step S30A, controller 150A calculates the position of cutting edge 42a relative to camera 800A based on the attitude of drawbar 40 relative to camera 800A calculated in step S10 and the attitude of blade 42 relative to center of rotation C of turning circle 41 calculated in step S20A. In step S40, controller 150A calculates the position of cutting edge 42a relative to ball shaft 402 based on the position of cutting edge 42a calculated in step S30A.

[0154] Fig. 17 is a flow diagram showing details of the processing of step S20A in Fig. 16. As shown in Fig. 17, in step S28, the controller 150A 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 the sensor that measures the rotation angle of the turning circle 41.

[0155] 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 Euler angles of the blade 42, 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 150A calculates the attitude of the blade 42 with respect to the center of rotation C of the turning circle 41.

[0156] Even with this configuration, information on the position of the cutting edge 42 a relative to the ball shaft 402 can be obtained.

[0157] (Second Modification) In step S10 of FIG. 13 , the attitude (three-dimensional Cartesian coordinates and Euler angles) of the drawbar 40 with respect to the camera 800A is calculated based on the images of the three markers 711 to 713. Below, a process for correcting the attitude of the drawbar 40 with respect to the camera 800A 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.

[0158] Controller 150A calculates the shift amount and tilt amount of blade 42 based on the attitude of drawbar 40 with respect to camera 800A calculated based on markers 711 to 713 (hereinafter referred to as the "first attitude") and the attitude of blade 42 with respect to camera 800A calculated based on markers 721 and 722. Controller 150A calculates the attitude of drawbar 40 with respect to camera 800A (hereinafter referred to as the "second attitude") based on the calculated attitude of blade 42 with respect to camera 800A, the calculated shift amount of blade 42, and the calculated tilt amount of blade 42.

[0159] Controller 150A corrects the first attitude using the second attitude. Controller 150A, for example, determines the average of the first attitude and the second attitude as the attitude of drawbar 40 relative to camera 800A. The correction method is not particularly limited. Controller 150A calculates the position of cutting edge 42a relative to camera 800A using the attitude of drawbar 40 after correction, instead of the "attitude of drawbar 40 relative to camera 800A" (i.e., the first attitude) in step S30 of FIG. 10 .

[0160] This configuration makes it possible to accurately calculate the attitude of drawbar 40. Therefore, the position of cutting edge 42a relative to camera 800A and the position of cutting edge 42a relative to ball axis 402 can be accurately calculated.

[0161] (Third Modification) In the above description, the drawbar attitude calculation unit 151A calculates the three-dimensional orthogonal coordinates of the turning center C of the turning circle 41 when the position of the camera 800A is used as a reference, using information about the difference (offset) between the three-dimensional orthogonal coordinates (fixed values) of the marker 711 when the work implement 4 is in the neutral position and the three-dimensional orthogonal coordinates (fixed values) of the turning center C. However, it is not necessarily necessary to use the offset information.

[0162] 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 the camera 800A.

[0163] 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, thereby making it possible to calculate the three-dimensional orthogonal coordinates of the turning center C of the turning circle 41 even if the markers attached to the swivel joints become unidentifiable.

[0164] 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.

[0165] 1, 1A 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, 22G, 40G, 51G, 102G, 104G, 106G, 701G, 702G, 703G image, 22f front end portion, 22r base end portion, 22u lower end surface, 25 exterior cover, 40 draw bar, 40f front end portion, 40r rear end portion, 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, 150A controller, 151, 151A Drawbar attitude calculation unit, 152, 152A Blade attitude calculation unit, 153 Cutting edge position calculation unit, 153A First cutting edge position calculation unit, 154 Second cutting edge position calculation unit, 402 Ball axis, 701, 702, 703, 711 to 713, 721, 722 Marker, 790 Support member, 800, 800A Camera, 801, 801A Lens, 802, 802A Main body, C Swivel center, J1, J3 Central axis, J2 Rotation axis, L Virtual line.

Claims

1. A motor grader comprising: a front frame; a drawbar; a connecting member that swingably connects the drawbar to the front frame in front of the drawbar; a first identification marker attached to a first position of the front frame that is near the connecting member; a camera attached to the drawbar and that captures an image of the first identification marker; and a controller that calculates the attitude of the drawbar based on first image data of the first identification marker obtained by the image capture.

2. A motor grader as described in claim 1, further comprising a second identification marker attached to a second position of the front frame near the connecting member, wherein the camera captures images of the first identification marker and the second identification marker, and the controller calculates the attitude of the drawbar based on the first image data and second image data of the second identification marker obtained by the image capture.

3. A motor grader as described in claim 1, wherein the attitude of the drawbar is the attitude of the drawbar relative to the connecting member, and the controller calculates the attitude of the connecting member relative to the camera based on the first image data, and calculates the attitude of the drawbar relative to the connecting member based on the attitude of the connecting member relative to the camera.

4. A motor grader according to any one of claims 1 to 3, wherein the camera is attached to the upper surface of the drawbar.

5. The motor grader according to claim 4, further comprising a swivel circle supporting a blade and swivelably attached to said drawbar, said drawbar having an end connected to said connecting member, and said camera located on a central axis of said drawbar extending from said end in a direction toward the center of rotation of said swivel circle.

6. A motor grader comprising: 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 and capturing an image of the first identification marker; and a controller that calculates a first attitude of the drawbar relative to the camera based on first image data of the first identification marker obtained by the image capturing.

7. A motor grader as described in claim 6, further comprising: a swivel circle rotatably attached to the drawbar; a blade supported on the swivel circle; and a second identification marker attached to the blade, wherein the camera captures images of the first identification marker and the second identification marker, and the controller calculates the attitude of the blade relative to the camera based on second image data of the second identification marker obtained by the image capture.

8. The motor grader according to claim 7, wherein the blade has a cutting edge, and the controller calculates the position of the cutting edge 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.

9. The motor grader according to claim 8, further comprising a connecting member that swingably connects the drawbar to the front frame in front of the drawbar, 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.

10. A motor grader according to any one of claims 6 to 9, wherein the front frame has a lower end surface facing the drawbar, and the camera is attached to the lower end surface.

11. The motor grader of claim 10, wherein the camera has an ultra-wide-angle lens.

12. The motor grader according to claim 6, wherein the first identification marker is provided on the upper surface of the drawbar.

13. The motor grader according to claim 7, wherein the second identification marker is installed above the blade.

14. A motor grader as described in any one of claims 6 to 9, wherein the controller calculates a shift amount and a tilt amount of the blade based on a first attitude of the drawbar relative to the camera and an attitude of the blade relative to the camera, and calculates a second attitude of the drawbar relative to the camera based on the attitude of the blade relative to the camera, the shift amount of the blade, and the tilt amount of the blade.

15. A method for calculating the attitude of a drawbar of a motor grader, comprising the steps of: capturing an image of an identification marker attached to a predetermined position on the front frame near a connecting member using a camera attached to a drawbar that is swingably connected to the front frame by a connecting member; and calculating the attitude of the drawbar based on image data of the identification marker obtained by the image capture.

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

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