Method for depositing material

Abstract

A method of depositing payload material from an implement of a work machine to a dump region. The method comprises defining a base perimeter of the dump region 110. The method comprises determining a maximum allowed volume of deposited material for the dump region 120, wherein the maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points. For each of the plurality of test points, the method comprises determining a remaining allowed height by subtracting a current height of material from a maximum height of material at each of the test points 130. Based on the plurality of remaining allowed heights, the method comprises determining a deposit path for the implement of the work machine 140. The method comprises executing the deposit path to deposit payload material from the implement to the dump region while moving the implement along the deposit path 150, wherein the deposit path is such that deposited payload material is within the maximum allowed volume. A device to perform the above method is also defined.

Description

Field of the disclosure The disclosure relates to the field of work machines, and in particular to work machines configured to excavate or move material. Background It is known to use a work machine to move material from one location to another. The work machine may excavate the material and then dump the material to a dump location, or may simply move material to a dump location. The dump location may be on the ground, in a truck or vehicle, or elsewhere. The work machine may be operated by a user in the work machine, by a remote user, or autonomously. A human operating a work machine from the cab of the work machine may choose where to deposit material from an implement of the work machine. The operator may make visual observations of the type of material being moved and / or of the quantity and distribution of material already at the dump location. Based on their judgment, the human operator may choose where to deposit the material at the dump location, and may choose whether to continue moving an implement of the work machine while dumping the material. These decision are based on visual observations and prior knowledge of the behaviour of material. Increasingly, work machines are being automated or operated remotely. Visual observations of material or of the dump location may not be available, meaning that a remote operator may not be able to rely on such observations when deciding where to deposit material. Similarly, automated systems for depositing material at dump locations currently operate on limited inputs. An automated work machine may often be configured to move an implement carrying a payload of material from a first region to a dump region, stop the motion of the implement, and discharge the payload of material. The implement is then moved back to the first region to collect more material. Stopping and starting the movement of the implement in this way may result in a longer dump cycle of the implement than might be desired. An automated work machine would conventionally dump material to a fixed location, resulting in a cone or pile of material developing. A cone or pile of material may obstruct motion of a linkage or other part of the work machine. In an event that the cone of material exceeds a certain height, there may be a risk of material falling from the cone. Furthermore, drainage from a tall cone of material may be impeded. It would be beneficial to spread material over a larger area. It is an object of the present disclosure to provide a method of depositing payload material from a work machine that does not require the visual observations of an in-situ operator, while achieving a similar or better efficiency of dump cycle and distribution of material that would be achieved by an in-situ operator. Summary of the disclosure Against this background, there is provided a method of depositing payload material from an implement of a work machine to a dump region, the method comprising: a) defining a base perimeter of the dump region; b) determining a maximum allowed volume of deposited material for the dump region, wherein the maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points on the dump region and wherein each maximum height is relative to a reference point; c) for each of the plurality of test points, determining a remaining allowed height by subtracting a current height of material from the maximum height of material at each of the plurality of test points; d) based on the plurality of remaining allowed heights, determining a deposit path for the implement of the work machine; and e) executing the deposit path to deposit payload material from the implement to the dump region while moving the implement along the deposit path, wherein the deposit path is such that deposited payload material is within the maximum allowed volume. In this way, it is possible to obtain a more even distribution or more gradual slope of deposited payload material, even without visual inputs or operation by a human operator in the cab. As a result, movement of the implement of the work vehicle is not obstructed when moving over the dump region, such as when moving back to a dig region or when depositing further payload material. Furthermore, avoiding a pile of payload material that is above a certain height or that will spill outside of the dump region is advantageous for safety reasons. A more even distribution or more gradual slope of deposited payload material within a dump region also improves drainage over deposited payload material having a rough surface or a broken surface or a surface with deep recesses. Implementing a deposit path rather than a deposit point allows a linkage connecting the implement to the work machine to keep moving while depositing the payload material, keeping cycle times (of digging and depositing material) low and increasing productivity. There is also provided a device for determining a deposit path for depositing payload material from an implement of a work machine to a dump region, wherein the device is configured to: f) define a base perimeter of the dump region; g) determine a maximum allowed volume of deposited material for the dump region, wherein the maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points on the dump region and wherein each maximum height is relative to a reference point; h) for each of the plurality of test points, determine a remaining allowed height by subtracting a current height of material from the maximum height of material at each of the plurality of test points; i) based on the plurality of remaining allowed heights, determine a deposit path for the implement of the work machine; and j) execute the deposit path to deposit payload material from the implement to the dump region while moving the implement along the deposit path, wherein the deposit path is such that deposited payload material is within the maximum allowed volume. Brief description of the drawings A specific embodiment of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a flowchart illustrating a method according to an embodiment of the present disclosure. Figure 2 shows a schematic of a dump region relative to a horizontal plane according to an embodiment of the present disclosure. Figure 3 shows a schematic of a dump region relative to a horizontal plane according to an embodiment of the present disclosure. Figure 4 shows a schematic cross-section of a maximum allowed volume of a dump region according to an embodiment of the present disclosure, wherein the dump region is parallel to a horizontal plane. Figure 5 shows a schematic cross-section of a maximum allowed volume of a dump region according to an embodiment of the present disclosure, wherein the dump region is at an angle to a horizontal plane. Figure 6 shows a schematic cross-section of a maximum allowed volume of a dump region according to an embodiment of the present disclosure, wherein the dump region is at an angle to a horizontal plane. Figure 7 shows a schematic cross-section of a maximum allowed volume of a dump region according to an embodiment of the present disclosure, wherein the dump region is parallel to a horizontal plane. Figure 8 shows a schematic cross-section of a maximum allowed volume of a dump region according to an embodiment of the present disclosure, wherein the dump region is at an angle to a horizontal plane. Figure 9 shows a schematic cross-section of a dump region after depositing payload material at a dump region according to an embodiment of the present disclosure. Figure 10 shows a schematic cross-section of a dump region after depositing payload material at a dump region according to an embodiment of the present disclosure. Detailed description A method is provided of depositing payload material from an implement of a work machine to a dump region. The implement may comprise any implement (also referred to herein as a tool) configured to carry a load, including but not limited to a bucket. The implement may, optionally, further comprise one or more components connecting the implement or tool configured to carry a load to the work machine. For example, the implement may further comprise an arm connecting a tool to the work machine, wherein a first distal end of the arm is connected to the work machine and the tool is connected to a second distal end of the arm. In another example, the implement may further comprise a boom and a stick, wherein a first distal end of the boom is connected to the work machine, a first distal end of the stick is connected to a second distal end of the boom, and the implement or tool is connected to a second distal end of the stick. With reference to Figure 1, the method comprises defining a base perimeter of the dump region at step 110. The base perimeter may be defined in two or three dimensions. At step 120, the method comprises determining a maximum allowed volume of deposited material for the dump region. The maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points on the dump region, wherein each maximum height is relative to a reference point. The reference point may be the same for each test point or may vary between test points. For each of the plurality of test points, the method comprises determining a remaining allowed height by subtracting a current height of material from the maximum height of material at each of the plurality of test points (step 130). Based on the plurality of remaining allowed heights, the method further comprises determining a deposit path for the implement of the work machine (step 140). At step 150, the method comprises executing the deposit path to deposit payload material from the implement to the dump region while moving the implement along the deposit path. The deposit path is such that deposited payload material is within the maximum allowed volume. Executing the deposit path may comprise spreading the payload material from the implement of the work machine over the deposit path. The deposit path may comprise a line or 2D path within the dump region, or a sector or polygon of the dump region. The deposit path may be defined by one or more test points, wherein the deposit path passes through each of the one or more test points or within a threshold distance of each of the one or more test points or within a grid cell around each of the one or more test points. A location of a test point may be provided by a radius and angle from the work machine or by a coordinate based on the base perimeter of the dump region, or by another coordinate. The location of the test point may be provided in two dimensions. The vertical location (along a gravity vector) of the test point may be undefined. Otherwise, the location of the test point may be provided in three dimensions. The vertical location of the test point may be at a base surface (wherein the base surface of the dump region is a surface of the dump region within the base perimeter prior to depositing payload material at the dump region) or at another vertical location. A test point may be projected along a test axis perpendicular to a horizontal inertial frame, wherein horizontal is defined as being perpendicular to a gravity vector. A maximum height, current height and remaining allowed height of deposited material at a test point may each be defined along the test axis, from the reference point. Where the deposit path is described as intersecting a test point, the deposit path may intersect any location on the test axis. For example, the deposit path may be executed such that the implement passes above the test point. The test points may be arranged in an array or grid, such that a gird cell area is associated with each test point. A test axis multiplied by the grid cell area for each test point may comprise a test volume. Where the deposit path is described as intersecting a test point, the deposit path may intersect any location within the test volume. Step 110 of defining the base perimeter may comprise defining a new base perimeter of the dump region, or step 110 may comprise defining the base perimeter as the base perimeter defined in a previous iteration of the method. In certain embodiments, a first iteration of the method may comprise defining a new base perimeter of the dump region at step 110, and determining a maximum allowed volume of deposited material at step 120. At step 130, a remaining allowed height is determined for each test point. Based on the plurality of remaining allowed heights, the method further comprises determining a deposit path for the implement of the work machine (step 140), and at step 150 the deposit path is executed. A second iteration of the method may comprise defining the base perimeter as the base perimeter of the first iteration at step 110, and determining the maximum allowed volume to be the maximum allowed volume of the first iteration at step 120. At step 130, the method comprises determining updated remaining allowed heights, using updated current heights for each test point. For each subsequent iteration, the base perimeter and the maximum allowed volume may be defined as the base perimeter and the maximum allowed volume, respectively, of the first iteration of the method. Alternatively, second and subsequent iterations of the method may repeat steps 130 to 150, as indicated by the dashed arrow in Figure 1. For example, in use, a work machine may arrive at or be located at a dig site to begin excavating or moving material from a dig region to the dump region (wherein the term excavating as used herein may include excavating material from the ground, picking up material from a pile of material, or otherwise adding material to the implement of the work machine). The work machine may excavate or pick up payload material from the dig region and deposits the payload material at the dump region, then repeat the excavation-dump cycle to continue picking up payload material from the dig region and depositing the payload material at the dump region. When or before the work machine carries out the first excavation-dump cycle at a particular dig site, step 110 of the method may comprise defining a new base perimeter of the dump region. When carrying out a subsequent excavation-dump cycle at the dig site, step 110 may comprise defining a base perimeter based on the new base perimeter of the first excavation-dump cycle. When or before the work machine carries out the first excavation-dump cycle at a particular dig site, step 120 of the method may comprise defining a new maximum allowed volume of the dump region. When carrying out a subsequent excavation-dump cycle at the dig site, step 120 may comprise defining a maximum allowed volume based on the new maximum allowed volume of the first excavation-dump cycle. In certain embodiments, defining a base perimeter of the dump region may be carried out by a human operator. For example, an operator may define a base perimeter of the dump region prior to initiating an excavation using the work machine (wherein the work machine may be operated remotely, or may carry out the excavation autonomously). In other embodiments, the base perimeter of the dump region may be pre-defined, for example based on a mapped worksite. The base perimeter may be defined based on a base perimeter or other perimeter of a previous iteration of depositing payload material. The base perimeter may be defined using one or more perception sensors of the work machine. The base perimeter may be defined by any other suitable method. In certain embodiments, the base perimeter may be defined without defining any properties of the dump region within the base perimeter. A height of one or more points of a base surface of the dump region (wherein the base surface of the dump region is a surface of the dump region within the base perimeter prior to depositing payload material at the dump region) may be inferred from the base perimeter. In other embodiments, defining the base perimeter may further comprise defining properties of the base surface within the base perimeter such as a height of one or more points of the base surface relative to the calibration point. For example, defining a base perimeter may further comprise one or more of defining the base surface as planar; defining whether a planar base surface is flat (relative to ground level or relative to a horizontal plane orthogonal to the gravity vector) or at an angle (relative to ground level or relative to a horizontal plane orthogonal to the gravity vector); determining a height of one or more points of the base surface relative to the calibration point; defining properties of the base surface visually; defining properties of the base surface using one or more measurements; defining properties of the base surface using a drone scan or other scan; or defining properties of the base surface using prior knowledge of the dump region (such as from depositing payload material from a prior excavation). The base perimeter may be indicative of an edge of base surface of the dump region, prior to depositing the payload material in the dump region. The base perimeter may be continuous or may be defined via discrete perimeter points. The base perimeter may be indicative of at least a lateral extent of the dump region on the base surface. The base perimeter may also be indicative of a height of the edge of the base surface relative to a calibration point (so that, in other words, the base perimeter is indicative of a height of the edge of the base surface relative to a plane containing the calibration point). An example is illustrated in Figure 2, which shows a calibration point 210. A plane 220 contains the calibration point. The base perimeter 230 surrounding the base surface 240 is indicative of a height of the edge of the base surface 240 relative to the plane 220 containing the calibration point 210, as indicated by the arrows. The calibration point may be a point on the base perimeter, within the base perimeter, or outside the base perimeter. In certain embodiments, the calibration point may be defined by resting the implement on the base surface or on a surface outside of the base perimeter. The calibration point may be defined by an offset from a known positioning system; or by using data from a sensor on the work machine; or by using data from a sensor separate to the work machine. The plane 220 containing the calibration point 210 may, for example, be parallel to ground level or be parallel to a horizontal plane orthogonal to the gravity vector or be parallel to the ground surrounding the dump region. The base perimeter may be defined in two dimensions, such that the base perimeter lies within a plane as illustrated in Figure 2. Otherwise, as shown in Figure 3, the base perimeter 330 may be defined in three dimensions. In Figure 3, the base perimeter 330 is indicative of a height of the edge of the base surface 340 relative to the plane 320 containing the calibration point 310, as indicated by the arrows. The base surface may be any surface on which the payload material may be deposited, including but not limited to the ground, a pre-existing pile of deposited payload material and a loading portion of a vehicle. The base perimeter may comprise a perimeter on or adjacent to ground on which payload material will be deposited. The ground may be planar or may not be planar. The base perimeter may comprise a perimeter on or adjacent to an upper edge of an existing pile of deposited payload material. The base perimeter may be on, in or adjacent to a vehicle configured to transport deposited payload material. For example, the base perimeter may be in or on a loading portion of a truck. At step 120, the maximum allowed volume of deposited material is determined for the dump region, comprising a maximum height of deposited material at each of a plurality of test points on the dump region. The maximum allowed volume may be defined by an enclosed surface that is fit to the maximum height for each test point and the base surface. Each maximum height is relative to a reference point. The reference point may be at the same height the same for each of the test points. The reference point may be defined based on the base perimeter, or by resting the implement on the base surface, or based on an offset from a known positioning system; or by using data from a sensor on the work machine; or by using data from a sensor separate to the work machine, or by any other suitable method. The reference point may be different to or may be equivalent to the calibration point. With reference to Figure 4, a cross-sectional view of a maximum allowed volume 440 is illustrated. In the illustrated example, the base surface 430 of the dump region is in a plane 420 containing the calibration point 410. Each reference point (each corresponding to a test point) are illustrated by the solid circles in the dump region. Four exemplary reference points are labelled as 450. There may be more or fewer reference points (and, therefore, test points) than are shown in Figure 4. The maximum height for each test point is illustrated by an arrow from each reference point (one arrow is labelled as 460 as an example). The maximum heights for each test point define the maximum allowed volume 440. Each reference point 450 is at the same height as the calibration point 410. With reference to Figure 5, a cross-sectional view of a maximum allowed volume 540 is illustrated. In the illustrated example, the base surface 530 is at an angle to a plane 520 containing the calibration point 510. Each reference point (each corresponding to a test point) are illustrated by the solid circles on the plane 520. Each reference point 550 is at the same height as the calibration point 510. Four exemplary reference points are labelled as 550. There may be more or fewer reference points (and, therefore, test points) than are shown in Figure 5. The maximum height for each test point is illustrated by an arrow from each reference point (one arrow is labelled as 560 as an example), wherein the maximum height for each test point is relative to the calibration point. An enclosed surface fit to the maximum heights for each test point and the base surface 530 defines the maximum allowed volume 540. Otherwise, the reference point may vary between test points. In an example, the reference point for each test point may be based on the base perimeter. In another example, the reference point for each test point may be at the base surface, such that the maximum height of material at each of the plurality of test points is relative to the base surface. With reference to Figure 6, a cross-sectional view of a maximum allowed volume 640 is illustrated. In the illustrated example, the base surface 630 is at an angle to a plane 620 containing the calibration point 610. Each reference point (each corresponding to a test point) are illustrated by the solid circles on the base surface 630. Four exemplary reference points are labelled as 650. There may be more or fewer reference points (and, therefore, test points) than are shown in Figure 6. The maximum height for each test point is illustrated by an arrow from each reference point (one arrow is labelled as 660 as an example), wherein the maximum height for each test point is relative to a corresponding point on the base surface. An enclosed surface fit to the maximum heights for each test point and the base surface 630 defines the maximum allowed volume 640. The maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points in the dump region, wherein each maximum height is relative to a reference point. The maximum allowed volume may comprise only the maximum heights at each test point, or the maximum allowed volume may comprise heights at points between the test points. For example, a maximum allowed volume may be extrapolated between the test points. Or, the maximum allowed volume may be determined as a continuous shape, and the maximum height of each test point may be determined from the maximum allowed volume. Determining the maximum allowed volume of deposited material may be based on a threshold allowed height of deposited material, wherein the threshold allowed height of deposited material may be maximum allowed height of deposited material at any point on the dump region. Determining the maximum allowed volume of deposited material may be based on the base perimeter of the dump region. Determining the maximum allowed volume of deposited material may be based on an angle of repose of the payload material. The angle of repose of a material comprises a steepest angle relative to a horizontal plane at which the material can be deposited or piled without slumping, wherein the horizontal plane is orthogonal to the gravity vector. The angle of repose may be estimated. For example, the angle of repose may be estimated based on an average angle of repose for certain payload materials, or for previous dump regions at the same worksite, or for the particular payload material being deposited. The angle of repose may be based on prior data for the payload material or for the worksite. The angle of repose may be entered as a system input at the work machine by an operator. In certain embodiments, determining the maximum allowed volume of deposited material may be based on a threshold allowed height of deposited material, the base perimeter of the dump region and an angle of repose of the payload material. In certain embodiments, determining the maximum allowed volume of deposited material may comprise using the threshold allowed height of deposited material and the base perimeter of the dump region to determine a volume having the threshold allowed height across the whole dump region. The volume may then be eroded adjacent to the base perimeter based on the angle of repose of the payload material, for example by reducing the maximum height of one or more test points, until the maximum allowed volume is such that the maximum height of the maximum allowed volume does not exceed the threshold allowed height and such that in an event that the maximum allowed volume was filled with payload material, the payload material would not slump outside of the base perimeter of the dump region. In other embodiments, the maximum allowed volume may be determined by starting at the base perimeter of the dump region and applying the angle of repose incrementally inwards and upwards from the base perimeter until either a peak is reached or a threshold height is reached. The maximum allowed volume may have a cross-section similar to that shown in Figure 7. Figure 7 illustrates a cross-section of a maximum allowed volume 720 on a base surface 710, wherein sides 721, 722 of the maximum allowed volume 720 are at the angle of repose a relative to a horizontal plane orthogonal to the gravity vector (in the example shown, the base surface 710 is in the horizontal plane) and a top 723 of the maximum allowed volume 720 is at the threshold height 724 relative to the horizontal plane. Figure 8 illustrates a cross-section of a maximum allowed volume 820 on a base surface 810, wherein the base surface 810 is at a finite angle to a horizontal plane 830 orthogonal to the gravity vector. Sides 821, 822 of the maximum allowed volume 820 are at the angle of repose a relative to the horizontal plane 830 and a top 823 of the maximum allowed volume 820 is at the threshold height 824 relative to the horizontal plane 830. At step 130, a remaining allowed height is determined for each of the plurality of test points. In other words, a delta grid map may be determined wherein the remaining allowed height is determined across the dump region, discretised by the test points. The remaining allowed height is determined by subtracting a current height of material from the maximum height of material at each of the plurality of test points. The current height of material at a test point may be obtained by any suitable means. In a first iteration of the method, if no payload material has been deposited at the dump region, the current height at a given test point may be zero. In a subsequent iteration of the method, or if payload material has previously been deposited at the dump region, the current height at one or more test points may be larger than zero. The current height may be based on a deposit path of a previous iteration of the method. For example, a given test point may have a first current height in a first iteration of the method. In an event that the deposit path determined at step 140 of the current iteration of the method does not pass through the test point (or within a threshold distance of the test point or within a grid cell area around the test point), the current height of the test point for a second iteration of the method may be kept at the first current height. In an event that the deposit path determined at step 140 of the current iteration of the method passes through the test point (or within a threshold distance of the test point or within a grid cell area around the test point), the current height of the test point for a second iteration of the method may be updated to a second current height that is larger than the first current height. The amount by which the second current height is larger than the first current height may be determined by any suitable means. For example, an amount by which the second current height is larger than the first current height may be based on an average volume of material deposited during an iteration of the method, or on a volume of payload material deposited at the test point during the first iteration of the method. A volume of payload material deposited at the test point during the first iteration of the method may be determined using a measured mass of material deposited and a known or estimated density of the material. The volume of payload material deposited at the test point during the first iteration of the method may be further determined using a length of the deposit path selected in the first iteration of the method. For example, in an event that the deposit path selected in the first iteration of the method passes through more than one test point, the deposited payload material may be split between the more than one test point. A mass of material deposited may comprise a mass of payload material on or in the implement prior to executing the deposit path, the mass of payload material being obtained from a sensor of the work machine. The deposit path determined at step 140 may intersect one or more test point having a positive remaining allowed height. As defined herein, intersecting with a test point may comprise passing through the test point, or passing within a threshold distance of the test point, or passing within a grid cell area around the test point. In other words, the deposit path may be such that when executed, the payload material is deposited in a part of the dump region that contains a test point where the current height of deposited material is lower than the maximum height of deposited material. In certain embodiments, the deposit path may intersect one or more test point having a positive remaining allowed height above a threshold remaining allowed height, such that after the deposit path has been executed a height of material at said test point is at or below the maximum height. In certain embodiments, the deposit path may start at a centre point of the dump region and may travel outwards from the centre point, wherein the deposit path ends prior to or at a boundary of the dump region. The deposit path may start at a boundary of the dump region and end within the boundary of the dump region. For example, a deposit path may be directed from the boundary towards a centre point of the dump region, or from a first side of the boundary towards a second side of the boundary. Inside the boundary the test points may each have a positive remaining allowed height or a remaining allowed height that is above a threshold. Outside the boundary the test points may each have a remaining allowed height that is below the threshold. In certain embodiments, the deposit path may intersect a test point having the largest remaining allowed height of the plurality of test points. The deposit path may be selected from more than one candidate deposit path. Each candidate deposit path may intersect with only test points having a positive remaining allowed height. In certain embodiments, each candidate deposit path may intersect only test points having a positive remaining allowed height above a threshold remaining allowed height, such that after the deposit path has been executed a height of material at said test points is at or below the maximum height. In certain embodiments, each candidate deposit path may intersect a test point having the largest remaining allowed height of the plurality of test points. Each candidate deposit path may intersect the same test point having the largest remaining allowed height of the plurality of test points, or each candidate deposit path may intersect one of more than one test point having the largest remaining allowed height of the plurality of test points. The deposit path may be selected from the candidate deposit path based on one or more optimisation factors. The one or more optimisation factors may include the remaining allowed height of the other test points or test points on each candidate deposit path (i.e. the test points on the candidate deposit path that have a remaining allowed height that is less than the largest remaining allowed height). The one or more optimisation factors may include a time taken for the work machine to execute the deposit path to deposit the payload material. In certain embodiments, each candidate deposit path may have a summed remaining allowed height comprising a sum of each remaining allowed height of each test point through which the candidate deposit path passes. The selected deposit path may have the largest summed remaining allowed height of the candidate deposit paths. Optionally, one or more candidate deposit paths may intersect a test point having the largest remaining allowed height of the plurality of test points. The deposit path may be selected from the candidate deposit path based on one or more optimisation factors. The one or more optimisation factors may include a time taken for the work machine to execute the deposit path to deposit the payload material. As discussed above with reference to Figure 1, second and subsequent iterations of the method may repeat steps 130 to 150. In certain embodiments, the deposit path determined at step 140 of a particular iteration of the method may be based on one or more optimisation factors associated with one or more subsequent iterations of steps 130 to 150. For example, determining the deposit path for a current iteration of the method may take into account candidate deposit paths that would be available for a subsequent iteration of the method if a certain deposit path was selected in the current iteration of the method. Determining the deposit path for a current iteration of the method may take into account an outcome of selecting a first deposit path for the current iteration of the method followed by a second deposit path for the next iteration of the method. The outcome may include a time taken for the work machine to execute the first and second deposit paths. The outcome may include a height of material at one or more test points that would be present after executing the first and second deposit paths. More than one candidate deposit path may be considered for each of the first and second deposit paths. Determining the deposit path for a current iteration of the method may take into account more than one possible outcome, wherein each possible outcome is for selecting a different combination of candidate deposit paths for the first deposit path and the second deposit path. Determining the deposit path for a current iteration of the method may take into account an outcome of selecting a first deposit path for the current iteration of the method followed by a plurality of deposit paths for a plurality of subsequent iterations of the method. The outcome may include a time taken for the work machine to execute the first deposit path and the plurality of subsequent deposit paths. The outcome may include a height of material at one or more test points that would be present after executing the first deposit path and the plurality of subsequent deposit paths. More than one candidate deposit path may be considered for each of the first deposit path and the plurality of subsequent deposit paths. Determining the deposit path for a current iteration of the method may take into account more than one possible outcome, wherein each possible outcome is for selecting a different combination of candidate deposit paths for the first deposit path and the plurality of subsequent deposit paths. The deposit path may be selected based on a tree of one or more subsequent deposit paths for one or more subsequent iterations of steps 130 to 150, such as by using a Monte Carlo tree search or using a gradient descent, or using another appropriate optimisation algorithm. In certain embodiments, selecting a deposit path may prioritise other optimisation factors. For example, a deposit path that is closer to the work machine or the dig region may be prioritised over a deposit path that is further from the work machine or the dig region. This benefits from gravity spreading the payload material down the pile away from an edge nearest to the work machine or dig region, such that payload material is deposited in parts of the dump region further from the work machine without the work machine needing to execute a deposit path through the part further from the work machine. With reference to Figure 9, a cross-section of a dump region is illustrated with the payload material deposited after a first dump cycle 910, a second dump cycle 920 and a third dump cycle 930. For each dump cycle, deposit path passes through an axis indicated by arrow 940 in the centre of the dump region, such that the peak of each of 910, 920 and 930 is in the centre of the dump region. With reference to Figure 10, a cross-section of a dump region is illustrated with the payload material deposited after a first dump cycle 1010, a second dump cycle 1020 and a third dump cycle 1030. For each of the first, second and third dump cycles, the deposit path passes through an axis 1040, 1050 and 1060, respectively. Axes 1040 and 1050 are offset from a centre of the dump region and from each other, and are closer to the work machine or dig region than axis 1060. Material deposited at axis 1050 from the second dump cycle flows from axis 1050 towards the centre of the dump region, away from the work machine or dig region. After step 150, the method may further comprise determining a model of the terrain of the dump region after executing the deposit path to deposit the payload material. This may comprise updating the current height of each test point, as described above. Updating each current height may be based on the deposit path and an estimated volume of deposited material. The estimated volume may be based on an average deposited volume, a measured mass of deposited material (and an estimated density of the material), or other factor. The model may by further based on material characteristics, such as material cohesivity. Material cohesivity may, for example, affect how the payload material leaves the implement (such as in clumps or free-flowing), and a spread of the material once deposited. In certain embodiments, determining the deposit path may take into account a slope or gradient of a model of the terrain. The model of the terrain may comprise the current height for each test point. For example, material may be expected to slide further if deposited on a steeper slope than on a shallower slope. Similarly, determining a model of the terrain after executing the deposit path may take into account a slope or gradient of a model of the terrain prior to executing the deposit path, since the deposited material may slide away from the deposit path. Determining an extent to which material may slide may further be based on material cohesivity. In some embodiments, the material may be assumed to be free-flowing low friction material. In certain examples, the model of the terrain comprising the current height for each test point may be more sloped adjacent to edges of the base perimeter, and relatively flat or shallower in a central region of the dump region (similar to the shape of the example of maximum allowed volume illustrated in Figure 4). The deposit path for the next iteration of the method may, in certain embodiments, be confined to the central region having a zero or shallow gradient. Material characteristics such as density and cohesivity may be estimated, or based on prior knowledge of the worksite, or based on averages, or determined based on sensor data from the work machine, or determined in some other way. For example, material characteristics such as density and cohesivity may be estimated based on monitoring of kinematics of the work machine. In an event that a payload sticks to an implement, the payload material is likely to be more cohesive. In an event that a material is harder to penetrate using the implement, or is harder to move, the payload material is likely to be denser and more compact. A dump cycle as referred to herein may be a cycle of picking up payload material from a dig region and depositing the payload material at the dump region, wherein depositing the payload material at the dump region may comprise at least steps 130 to 150 of the method described herein. A device is provided for determining a deposit path for depositing payload material from an implement of a work machine to a dump region using any of the methods described herein. The device is configured to define a base perimeter of the dump region. The device is further configured to determine a maximum allowed volume of deposited material for the dump region, wherein the maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points on the dump region and wherein the maximum height is relative to a reference point. For each of the plurality of test points, the device is configured to determine a remaining allowed height by subtracting a current height of material from the maximum height of material at each of the plurality of test points. Based on the plurality of remaining allowed heights, the device is configured to determine a deposit path for the implement of the work machine. The device is further configured to execute the deposit path to deposit payload material from the implement to the dump region while moving the implement along the deposit path, wherein the deposit path is such that deposited payload material is within the maximum allowed volume.

Claims

1. A method of depositing payload material from an implement of a work machine to a dump region, the method comprising:a) defining a base perimeter of the dump region;b) determining a maximum allowed volume of deposited material for the dump region, wherein the maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points on the dump region and wherein each maximum height is relative to a reference point;c) for each of the plurality of test points, determining a remaining allowed height by subtracting a current height of material from the maximum height of material at each of the plurality of test points;d) based on the plurality of remaining allowed heights, determining a deposit path for the implement of the work machine; ande) executing the deposit path to deposit payload material from the implement to the dump region while moving the implement along the deposit path, wherein the deposit path is such that deposited payload material is within the maximum allowed volume.

2. The method of claim 1, wherein determining the maximum allowed volume of deposited material is based on:a threshold allowed height of deposited material;the base perimeter of the dump region; and an angle of repose of the payload material.

3. The method of any preceding claim, wherein the deposit path intersects one or more test points having a positive remaining allowed height.

4. The method of any preceding claim, wherein the deposit path is selected from more than one candidate deposit path, wherein:each candidate deposit path intersects a test point having the largest remaining allowed height; and / oreach candidate deposit path has a summed remaining allowed height comprising a sum of each remaining allowed height of each test point through whichthe candidate deposit path passes, wherein the selected deposit path has the largest summed remaining allowed height of the candidate deposit paths.

5. The method of claim 4 wherein determining the deposit path further comprises selecting the deposit path from the candidate deposit paths based on one or more optimisation factors.

6. The method of claim 5, wherein the one or more optimisation factors comprises a time taken for machine to execute the deposit path.

7. The method of any preceding claim, wherein steps (c) to (e) are repeated.

8. The method of claim 7 when dependent on claim 5 or 6, wherein the one or moreoptimisation factors comprises one or more factors associated with subsequent iterations of steps (c) to (e).

9. The method of claim 8, wherein the deposit path is selected based on a tree of deposit paths for subsequent iterations of steps (c) to (e).

10. The method of any preceding claim, wherein the deposit path is updated at each iteration of step (d).

11. The method of any of claims 7 to 10, wherein the deposit path determined at step (d) is used to update the current height of material for each test point used at step (c) of a subsequent iteration of the method.

12. The method of any preceding claim, wherein a volume of payload material deposited at step (e) is used to update the current height of material at a subsequent iteration of step (c).

13. The method of any preceding claim, wherein the reference point is defined by: moving the implement to the base perimeter of the dump region; or an offset from a known positioning system; or using data from a sensor on the work machine; or using data from a sensor separate to the work machine.

14. A device for determining a deposit path for depositing payload material from an implement of a work machine to a dump region, wherein the device is configured to:f) define a base perimeter of the dump region;g) determine a maximum allowed volume of deposited material for the dump region, wherein the maximum allowed volume comprises a maximum height of deposited material at each of a plurality of test points on the dump region and wherein each maximum height is relative to a reference point;h) for each of the plurality of test points, determine a remaining allowed height by subtracting a current height of material from the maximum height of material at each of the plurality of test points;i) based on the plurality of remaining allowed heights, determine a deposit path for the implement of the work machine; andj) execute the deposit path to deposit payload material from the implement to the dump region while moving the implement along the deposit path, wherein the deposit path is such that deposited payload material is within the maximum allowed volume.

15. The device of claim 14, wherein determining the maximum allowed volume of deposited material is based on:a threshold allowed height of deposited material;a base perimeter of the dump region; andan angle of repose of the deposited material.

Images