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, a connection member that oscillatably connects the draw bar to the front frame in the forward side of the draw bar, a first identification marker fitted at a first position in the vicinity of the connection member on the front frame, a camera fitted on the draw bar to picture the first identification marker, and a controller that calculates a posture of the draw bar based on a first image 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. The first and second cameras are mounted on a front frame. [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, 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 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. [Effects of the Invention]

[0008] According to the present disclosure, 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. [Figure 3] 3 is a diagram showing an image based on image data obtained by imaging using a camera when the work machine is in the state shown in FIG. 2. FIG. [Figure 4] FIG. 3 is a diagram showing a state in which the drawbar has been moved to the right from the state in FIG. 2. [Figure 5]5 is a diagram showing an image based on image data obtained by imaging using a camera when the work machine is in the state shown in FIG. 4. FIG. [Figure 6] FIG. 5 is a diagram showing a state in which the drawbar has been moved to the upper right from the state shown in FIG. 4. [Figure 7] 7 is a diagram showing an image based on image data obtained by imaging using a camera when the work machine is in the state shown in FIG. 6. FIG. [Figure 8] FIG. 2 is a block diagram illustrating the functional configuration of the motor grader. [Figure 9] FIG. 10 is a flowchart for calculating the attitude of the drawbar. 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 diagram showing a main part of the work implement 4. Fig. 2 shows a state in which the work implement 4 is in a neutral position. Note that "a 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, "a 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.

[0022] 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.

[0023] 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 lift cylinders 44, 45. 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 the 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.

[0029] 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.

[0030] 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 as the revolving circle 41 is driven to revolve.

[0031] 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.

[0032] Blade 42 is supported so as to be swingable about an axis extending in the longitudinal direction of blade 42 relative to turning circle 41. Specifically, tilt cylinder 48 is attached to turning circle 41 and blade 42. By extending and contracting tilt cylinder 48, blade 42 swings about an axis extending in the longitudinal direction of blade 42 relative to turning circle 41, and the tilt angle of blade 42 with respect to the traveling direction of the vehicle (the rake angle of blade 42 with respect to the ground) can be changed.

[0033] 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.

[0034] 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. The number of markers is not limited to three, and may be one, two, four or more.

[0035] 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.

[0036] The camera 800 is attached to the upper surface of the draw bar 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 draw bar 40.

[0037] 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.

[0038] 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 22f 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.

[0039] 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.

[0040] 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.

[0041] Marker 702 is attached to a second predetermined position on front frame 22 near ball pivot 402. The second predetermined position is on the right side of ball pivot 402. Marker 703 is attached to a third predetermined position on front frame 22 near ball pivot 402. The third predetermined position is on the left side of ball pivot 402. In this example, the second predetermined position and the third predetermined position are line-symmetrical with respect to front frame 22 when viewed from above the work implement 4.

[0042] 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 pivot 402 the marker 701 is, the more rearward the marker 701 is from the front frame 22.

[0043] Marker 702 and marker 703 are in a line-symmetric relationship with respect to front frame 22 in a plan view of work implement 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 implement 4 is in a neutral state.

[0044] 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 axis 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.

[0045] 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, as long as the markers 701 to 703 can be distinguished from one another.

[0046] It is sufficient that the identifier of each marker 701-703 and the orientation of each marker 701-703 when the camera 800 is used as a reference can be determined. Specifically, with regard to the orientation of each marker 701-703, it is sufficient that the position (position in a three-dimensional Cartesian coordinate system) and the tilt state (Euler angle) of each marker 701-703 when the camera 800 is used as a reference can be determined. Note that this determination is performed by a controller 150 (more specifically, a processor) described later, based on image data acquired by the camera 800.

[0047] The above-described arrangement of the markers 701 to 703 is merely an example, and is not limited to the above. The ball shaft 402 is an example of the "connecting member" of the present disclosure.

[0048] 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 of 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 axis 402, image 701G of marker 701, image 702G of marker 702, and image 703G of marker 703.

[0049] The entire marker 701 is captured. As viewed from the camera 800, the drawbar 40 is positioned closer to the markers 702 and 703, so 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.

[0050] The virtual line L is a line segment that equally divides the left and right sides of the image 102G. Because the work implement 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 implement 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.

[0051] 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.

[0052] 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 with respect to the position of the camera 800 as the reference.

[0053] Fig. 5 is a diagram showing an image based on image data obtained by imaging using camera 800 when work implement 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.

[0054] 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.

[0055] 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.

[0056] Fig. 7 is a diagram showing an image based on image data obtained by imaging by camera 800 when work implement 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.

[0057] 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.

[0058] 8 and 9, a method for calculating the attitude of the drawbar 40 from image data obtained by capturing images of the markers 701 to 703 with the camera 800 will be described below. Furthermore, a process for calculating the attitude of the blade 42 and the position of the cutting edge 42a (FIG. 2) of the blade 42 based on the calculated attitude of the drawbar 40 will also be described.

[0059] 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.

[0060] FIG. 8 is a block diagram illustrating the functional configuration of the motor grader 1. As shown in FIG. 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.

[0061] The controller 150 has a drawbar attitude calculation unit 151, a blade attitude calculation unit 152, and a cutting edge position calculation unit 153. Note that 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. Note that, 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 ASIC.

[0062] 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 and the period in which the drawbar attitude calculation unit 151 calculates the attitude of the drawbar 40 do not have to be the same. The processing of the drawbar attitude calculation unit 151 will be described below.

[0063] 9 is a flowchart for explaining the flow of processing in drawbar attitude calculation unit 151. FIG. 9 is a flowchart for calculating the attitude of drawbar 40.

[0064] 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. In particular, 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. The fixed values ​​are pre-stored in the controller 150. Each fixed value, which will be described later, is also pre-stored in the controller 150.

[0065] 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.

[0066] 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.

[0067] Similarly, in step S3, the drawbar attitude calculation unit 151 calculates the three-dimensional Cartesian coordinates of the center of the ball axis 402 and the Euler angles of the ball axis 402 when the camera 800 is used as a reference, 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.

[0068] In step S4, the drawbar attitude calculation unit 151 calculates the three-dimensional orthogonal 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 orthogonal coordinates and Euler angles of the marker 703. In detail, the drawbar attitude calculation unit 151 calculates the three-dimensional orthogonal coordinates and the Euler angles using information on the three-dimensional orthogonal 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.

[0069] In step S5, 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 S2 to S4 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 calculated 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 range are abnormal values.

[0070] If it is determined that no abnormal values ​​are included (NO in step S5), the drawbar attitude calculation unit 151 advances the process 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 to improve accuracy in step S8. The drawbar attitude calculation unit 151 then advances the process to step S6.

[0071] In step S6, drawbar attitude calculation unit 151 determines the coordinates of the center of ball axis 402 when camera 800 is used as a reference and the Euler angles of ball axis 402 based on the three-dimensional orthogonal coordinates (excluding abnormal values) and the Euler angles (excluding abnormal values) calculated in steps S2 to S4. For example, drawbar attitude calculation unit 151 determines the coordinates of the center of ball axis 402 when camera 800 is used as a reference by calculating the average of the three-dimensional orthogonal coordinates (excluding abnormal values). Drawbar attitude calculation unit 151 determines the Euler angles of ball axis 402 when camera 800 is used as a reference by calculating the average of the Euler angles (excluding abnormal values).

[0072] In step S7, drawbar attitude calculation unit 151 calculates the attitude of drawbar 40 by converting the three-dimensional orthogonal coordinates and Euler angles determined in step S6 into three-dimensional orthogonal coordinates and Euler angles based on the center of ball axis 402. Drawbar attitude calculation unit 151 calculates the attitude of drawbar 40 based on the center of ball axis 402 by performing inverse conversion using a predetermined arithmetic expression.

[0073] 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.

[0074] 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.

[0075] 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 attitude of the blade (hereinafter referred to as "blade attitude information") to the cutting edge position calculation unit 153.

[0076] 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 predetermined design values. The calculated information on the position of the cutting edge 42a is used in various processes in the controller 150.

[0077] As described above, the motor grader 1 includes the marker 701 attached to the first predetermined position of the front frame 22 near the ball pivot 402, the marker 702 attached to the second predetermined position of the front frame 22 near the ball pivot 402, and the marker 703 attached to the third predetermined position of 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. 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, as shown in Fig. 8.

[0078] 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.

[0079] 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 not being read properly. 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.

[0080] 4 and 6, the motor grader 1 is a work machine that can assume a work machine posture with an extremely high degree of freedom. However, by arranging the markers 701-703 near the ball axis 402, the markers 701-703 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.

[0081] In the above description, an example has been given in which the motor grader 1 is configured to have three markers 701 to 703, but the present invention is not limited to this. The motor grader 1 may be provided with at least one marker. It is preferable that the motor grader 1 is provided with at least the central marker 701 in the left-right direction. However, by providing multiple markers 701 to 703, redundancy can be ensured against dirt and damage to the markers, and the "posture of the drawbar 40" can be calculated with high accuracy (step S6 in FIG. 9).

[0082] The attitude of the drawbar 40 is the attitude of the drawbar 40 with respect to the ball pivot 402. As shown in step S6 of Fig. 9, the controller 150 calculates the attitude of the ball pivot 402 with respect to the camera 800 based on the image data 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 pivot 402 based on the attitude of the ball pivot 402 with respect to the camera 800.

[0083] According to this configuration, it is possible to calculate the attitude of the drawbar 40 with respect to the ball axis 402 based on image data obtained by imaging using the camera 800 attached to the drawbar 40.

[0084] 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 701-703 within the angle of view of camera 800, even if the posture of work machine 4 changes in various ways.

[0085] As shown in FIGS. 1 and 2, the motor grader 1 further includes a slewing circle 41 that supports a blade 42 and is slewingably attached to a drawbar 40. As shown in FIG. 2, the drawbar 40 has a front end 40f that is connected to a ball shaft 402. As shown in FIG. 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.

[0086] According to this configuration, camera 800 is positioned on center axis J1 of drawbar 40, so camera 800 can capture an image of the periphery of ball pivot 402 regardless of the attitude of drawbar 40. Therefore, it becomes possible to capture an image of at least one of three markers 701 to 703.

[0087] Furthermore, when the motor grader 1 is parked with the work implement 4 in the neutral position, the front frame 22 is positioned 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.

[0088] 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]

[0089] 1 motor grader, 2 body frame, 3 cab, 4 work equipment, 6 engine compartment, 11 front wheels, 12 rear wheels, 21 rear frame, 22 front frame, 22G, 40G, 51G, 102G, 104G, 106G, 701G, 702G, 703G image, 22f front end portion, 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 controller, 151 draw bar attitude calculation unit, 152 blade attitude calculation unit, 153 cutting edge position calculation unit, 402 Ball axis, 701, 702, 703 markers, 800 camera, 801 lens, 802 main body, C rotation center, J1 central axis, J2 rotation axis, L virtual line.

Claims

1. The front frame and With 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 in the vicinity of the connecting member; a camera attached to the drawbar and configured to capture an image of the first identification marker; a controller that calculates an attitude of the drawbar based on first image data of the first identification marker obtained by the imaging.

2. a second identification marker attached to a second position of the front frame that is adjacent to the connecting member; 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 the attitude of the drawbar based on the first image data and second image data of the second identification marker obtained by the imaging.

3. the attitude of the drawbar is an attitude of the drawbar with respect to the connecting member, The controller calculating an attitude of the connecting member relative to the camera based on the first image data; The motor grader according to claim 1 , wherein an attitude of the drawbar relative to the connecting member is calculated based on an attitude of the connecting member relative to the camera.

4. The motor grader according to claim 1 , wherein the camera is attached to an upper surface of the drawbar.

5. a swivel circle supporting a blade and pivotally attached to the drawbar; the drawbar has an end connected to the connecting member, The motor grader according to claim 4 , wherein the camera is located on a central axis of the drawbar that extends from the end toward a turning center of the turning circle.

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

Images