Grass-cutting robot driving control device

Abstract

To provide a travel control device for a mowing robot that ensures travelling along a planned route even on a slope where a sideslip occurs.SOLUTION: A travel control device for mowing robot is configured to determine a planned travel route for a mowing robot and set an adjustment amount in a running direction to return the mowing robot to the planned travel route if it deviates from the planned travel route, depending on an amount of positional deviation of the mowing robot from the travel route. The travel control device includes: means for learning an amount of positional deviation offset based on a positional deviation of the mowing robot from the planned travel route after the mowing robot has traveled by adjusting the running direction of the mowing robot by the adjustment amount corresponding to the amount of positional deviation (steps S5 to S8); and means for setting the running direction of the mowing robot based on the amount of deviation of the mowing robot from the planned travel route and the amount of positional deviation offset (step S9).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a device for controlling a robot equipped with a grass cutter so as to travel along a travel path, and more particularly to a device for controlling the robot when traveling across a slope. [Background technology]

[0002] Patent Document 1 describes a self-propelled working device with a function of cutting grass such as weeds that grow on the ground. When a moving body equipped with wheels travels across a slope, that is, when traveling in a direction intersecting a line with a maximum slope angle, the moving body travels in a direction that deviates from the intended direction due to skidding or the like. In order to suppress or correct such deviation, the device described in Patent Document 1 is configured to be able to adjust the camber angle of the wheels individually. Then, when the change in the working unit attitude determined based on a signal from the attitude detection unit of the moving body is larger than the working unit attitude model, a signal for adjusting the attitude of the working unit is sent to the working unit attitude variable unit, and the working unit attitude variable unit adjusts the attitude of the working unit so that the change in the working unit attitude is smaller than the working unit attitude model. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-174759 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, the posture of the moving body is detected successively, and the detected result is compared with a posture model prepared in advance to adjust the camber angle of the wheels, and the posture is adjusted. Therefore, if the device is configured as described in Patent Document 1, the posture of the moving body or the grass mower can be set or maintained at a predetermined intended posture. However, it is the posture of the moving body or the grass mower that is adjusted in this way, and it is not possible to correct the deviation of the position of the moving body or the grass mower. In other words, when crossing a slope, the position of the grass mower is usually shifted due to skidding, etc., and if the posture is adjusted, the grass mower will continue to run in the direction of the posture model while remaining in the shifted position. Therefore, for example, if the position is shifted from a place where grass to be cut still remains, it becomes necessary for the operator to operate the moving body to move the moving body to the position where the grass should be cut, and there is still room for improvement in terms of automating grass cutting and reducing the burden on the operator.

[0005] This invention has been made in response to the above technical problems, and aims to provide a control device that can automate grass cutting on slopes by quickly and accurately correcting positional deviations when traveling across a slope. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a travel control device for a grass-mowing robot, which is configured to determine a planned travel path of a grass-mowing robot equipped with a cutter for cutting grass growing on a travel surface, and to set an adjustment amount of the travel direction of the grass-mowing robot for returning the grass-mowing robot to the planned travel path when the grass-mowing robot deviates from the planned travel path, according to an amount of deviation of the position of the grass-mowing robot from the travel path. The position is The traveling direction of the grass-cutting robot is adjusted according to the adjustment amount corresponding to the deviation amount. Before The deviation of the position of the grass-cutting robot from the planned travel path. a means for determining the amount of previous positional deviation, Misalignment offset Quantityand means for setting a running direction of the grass-mowing robot based on an amount of deviation of the grass-mowing robot from the planned running path and the amount of position deviation offset. Effect of the Invention

[0007] In this invention, when the grass mowing robot deviates from the planned travel path, the travel direction of the grass mowing robot is set by an adjustment amount corresponding to the amount of deviation. When traveling across an inclined surface, even if the travel direction is adjusted by the adjustment amount, the deviation from the planned travel path cannot be eliminated due to so-called lateral slip on the slope. In such a case, the position deviation offset amount is learned based on the position deviation after traveling with the travel direction adjusted by the adjustment amount. The travel direction of the grass mowing robot is set based on the position deviation offset amount and the position deviation amount from the planned travel path. Therefore, when the grass mowing robot deviates from the planned travel path again, the travel direction of the grass mowing robot is set based on the adjustment amount corresponding to the amount of deviation of the position plus the position deviation offset amount, so that the position deviation from the planned travel path is corrected based on the adjustment amount corresponding to the amount of deviation, and the lateral slip due to the slope is corrected by the position deviation offset amount, and as a result, the grass mowing robot can be returned to the planned travel path. Furthermore, since there is no positional deviation as described above on the planned travel route, the travel direction of the grass mowing robot is set based on the positional deviation offset amount. This positional deviation offset amount is a correction amount for the travel direction corresponding to lateral slippage caused by crossing a slope, so lateral slippage, i.e., positional deviation, of the grass mowing robot on the planned travel route is avoided or suppressed by the positional deviation offset amount. In other words, although the grass mowing robot will be oriented in a direction deviated from the planned travel route, such deviation prevents lateral slippage, and therefore the grass mowing robot can travel approximately along the planned travel route. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic block diagram for explaining a control system in the embodiment of the present invention. [Diagram 2] 4 is a flowchart illustrating an example of control executed in the embodiment of the present invention. [Diagram 3] 1A to 1C are schematic diagrams for explaining the behavior of a grass mowing robot on a slope when control according to an embodiment of the present invention is carried out. [Figure 4] 10A to 10C are schematic diagrams for explaining the behavior of the grass mowing robot on a slope when the control according to the embodiment of the present invention is not performed. [Diagram 5] 5A to 5C are schematic diagrams for explaining the behavior of the grass mowing robot on a horizontal plane when control according to an embodiment of the present invention is executed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely one example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0010] First, the configuration of the grass-cutting robot 1 in the embodiment of the present invention will be described. The grass-cutting robot 1 is a self-propelled grass-cutting machine, and therefore includes an engine or motor as a driving force source, a transmission mechanism including a gearbox that transmits the output torque of the engine or motor, drive wheels or crawlers that transmit the driving force for traveling to the traveling surface and support the whole machine, and a carriage unit having a steering mechanism that appropriately changes and sets the traveling direction. The grass-cutting robot 1 further includes a grass-cutting unit that includes a cutter that cuts grass growing on the traveling surface, a cutter transmission mechanism that transmits the driving force to the cutter, and a height adjustment mechanism that adjusts the height of the cutter from the traveling surface.

[0011] In addition, as a control device for self-propulsion, a position detection system is provided that detects the self-position, the target position, and appropriate positions between them as positions on a coordinate system. Examples of such a system include a global navigation satellite system (GNSS) and a system (LiDAR) that detects the self-position relative to the target position using laser light. In addition, a system is provided that uses these systems to set a planned travel route between the self-position and a predetermined target position. This system includes map information, and when there is an obstacle obtained from the map information on a linear planned route connecting the self-position and the target position, the system may be configured to set the planned travel route in the vicinity of the obstacle at a position away from the obstacle. The cart unit is controlled by these systems to travel autonomously on the planned travel route toward the target position.

[0012] As devices for controlling the mowing unit, a system for controlling the number of revolutions of the cutter and a system for adjusting the height of the cutter from the traveling surface are provided. The number of revolutions of the cutter may be configured to be controlled by the current of the motor that drives the cutter. The system for adjusting the height of the cutter may include a sensor that detects the height of the cutter and is configured to maintain the cutter at an artificially set cutting height.

[0013] FIG. 1 shows the above-mentioned system in a block diagram. The mowing robot 1 is configured to travel by a cart controller 2. The position detection system is included in the cart controller 2, and detects its own position on an orthogonal coordinate system, for example, a north-south direction and an east-west direction perpendicular to the north-south direction. The target position is manually input as a position on a map, and the position on the map is stored as a position on the orthogonal coordinate system. Then, a planned travel path is calculated based on the own position and the target position. The planned travel path is generally represented by a straight line connecting the self-position and the target position, but is represented by a number of consecutive points for control purposes, and therefore, a position deviation from the planned travel path can be detected by comparing the coordinates of those points with the coordinates of the self-position. That is, the travel control can be performed by determining the travel direction by comparing the self-position with the nearest position on the planned travel path and controlling the steering mechanism. The vehicle speed may be configured to be set manually, or may be configured to be automatically set to an appropriate speed within a predetermined range based on the flatness and inclination of the travel surface.

[0014] Therefore, position information is input to the cart controller 2 from the above-mentioned global navigation satellite system (GNSS) 3, a system (LiDAR) 4 that detects its own relative position using laser light, and the like.

[0015] In the example shown in FIG. 1, the grass cutting robot 1 is a self-propelled vehicle with crawlers 5 as running wheels, and is therefore configured to control the running direction (the orientation or posture of the grass cutting robot 1) and running speed by the number of rotations (rotation speed) of the crawlers 5. For this purpose, a rotation speed controller 6 is provided. That is, the carriage controller 2 outputs a control command signal instructing the target vehicle speed and running direction (facing) to the rotation speed controller 6, and the rotation speed controller 6 controls the number of rotations of the left and right crawlers 5 to achieve the received target vehicle speed and running direction. The rotation speeds of the left and right crawlers 5 may be appropriately set by controlling the number of rotations of motors (not shown) to which the respective crawlers 5 are connected, or a configuration may be adopted in which a drive torque is transmitted to the left and right crawlers 5 via a differential mechanism (not shown), and the differential mechanism is controlled to set a difference in the number of rotations between the left and right crawlers 5. The control of the number of rotations of the crawlers 5 can be performed by feedback control based on the difference between a target number of rotations based on a target vehicle speed or a target direction, and an actual number of rotations detected by a sensor (not shown).

[0016] On the other hand, the control of the grass cutting unit is executed by a cutter rotation speed controller 7 and a cutter height controller 8. The cutter rotation speed is determined by the vehicle speed, the density or type of grass to be cut, etc., and may be input by manual operation, or the optimum rotation speed may be obtained by machine learning (AI control) based on the resistance force during cutting the grass, the degree of entanglement of the grass around the cutter, and the type of grass manually input in advance. In addition, the cutter height is mainly determined by the purpose of cutting the grass, so it may be input by manual operation. Furthermore, the cutter rotation speed and height may be controlled by feedforward control, or by feedback control based on the deviation between the target value and the actual value.

[0017] The above-mentioned carriage controller 2, cutter rotation speed controller 7, and cutter height controller 8 are connected to an integrated controller 9. The integrated controller 9 is a control device for controlling the travel of the grass-cutting robot 1 and the overall mowing while traveling, and is configured to perform calculations based on manually input data, data obtained during grass-cutting, and pre-stored data such as map information, and to output control command signals to the respective controllers 2, 7, 8. In other words, each of the controllers 2, 7, 8, 9 is mainly configured as a microcomputer equipped with a central processing unit, a memory element, an input / output interface, etc.

[0018] An example of travel control of the mowing robot 1 by the above-mentioned system, that is, an example of control in an embodiment of the present invention, will now be described. FIG. 2 is a flow chart for explaining one example of this control, and the routine shown here is repeatedly executed at predetermined short intervals by the integrated controller 9 described above. First, the self-position coordinates are acquired (step S1). This can be obtained by the position detection system as described above. In addition, destination coordinates are acquired (step S2). Since the location where mowing is to be performed is selected manually, the destination is input manually. In this case, a map can be displayed on an appropriate monitor (not shown), and the destination can be selected by touching the destination on the map, and its coordinates can be acquired at the same time.

[0019] Next, a route (planned travel path) from the self-location to the destination is calculated based on the data of the self-location and the destination (step S3). This route can be obtained, for example, as the coordinates of a number of points that are lined up on a line connecting the self-location and the destination. When configured in this way, the grass cutting robot 1 travels so as to trace the number of points in order.

[0020] The deviation amount (positional deviation amount) ΔP of the self-position from the path obtained as described above is calculated (step S4). This positional deviation amount is a distance measured in a direction perpendicular to the path, and can be calculated from the coordinate value of the self-position in the direction perpendicular to the path and the coordinate value of a point on the path located in the perpendicular direction. Alternatively, it may be calculated as the distance between the self-position and a point on the path that is closest to the mowing robot 1.

[0021] FIG. 3A shows a schematic example of an example of a state in which such a positional deviation occurs. In the example shown here, a slope 11 inclined at a predetermined angle θ with respect to a horizontal plane 10 is used as a running surface, and mowing is performed by running across the slope 11. "Crossing" here means running in a direction intersecting a line (generatrix) at the maximum inclination angle of the slope 11. In such a situation, in the process of running from the start point 12 to the target position 13, so-called sideslip occurs according to the inclination angle θ, which causes a positional deviation from the planned path L. Since the grass cutting robot 1 is controlled to run on the planned path L toward the target position 13, when such a positional deviation occurs, the running direction is adjusted so as to return to the planned path L. The amount of adjustment can be an amount corresponding to the positional deviation amount ΔP. More specifically, the adjustment amount (or deflection amount) can be determined in advance by experiment or simulation, assuming, for example, a case in which the grass cutting robot 1 runs on a horizontal running surface, and the amount by which the grass cutting robot 1 can return to the planned path quickly within the range in which the grass cutting robot 1 can change direction mechanically.

[0022] The positional deviation amount ΔP is repeatedly detected at a predetermined short time while the grass mowing robot 1 is in operation, and the current positional deviation amount ΔPi determined in step S4 above is compared with the previously determined positional deviation amount ΔPi-1, and it is determined whether the absolute value of the difference is equal to or less than a predetermined threshold value A (step S5). This threshold value A is a small value of, for example, several centimeters to several tens of centimeters. Note that when the determination in step S5 is made for the first time after starting the control shown in FIG. 2, there is no previously determined positional deviation amount and the routine in FIG. 2 is repeated at short intervals, so the determination result in step S5 is affirmative (YES).

[0023] If the answer is affirmative in step S5, the positional deviation counter Dc is counted up by, for example, "1" (step S6). Then, it is determined whether the count value Dc is equal to or greater than a predetermined judgment reference value α (step S7). That is, steps S6 and S7 determine whether the positional deviation continues despite the adjustment of the running direction based on the positional deviation on the horizontal surface. A situation in which the positional deviation continues without being corrected is shown in FIG. 3B. The adjustment amount of the running direction according to the positional deviation amount ΔP is the adjustment amount when traveling on a running surface assumed in the design, such as a horizontal surface, as described above. The fact that the positional deviation continues even after such an adjustment of the running direction is due to so-called sideslip caused by traveling across the slope 11. Therefore, if the answer to step S7 is affirmative, i.e., if the positional deviation continues to occur, the previous positional deviation amount ΔPi-1 is set as the positional deviation offset amount ΔPo, which is the adjustment amount in the running direction to correct the continuing positional deviation, and the positional deviation counter Dc is reset (step S8).

[0024] Next, the running direction is adjusted based on the current positional deviation amount ΔPi and the positional deviation offset amount ΔPo set in step S8 (step S9). The functional means for controlling this step S9 corresponds to the "means for setting the running direction of the grass mowing robot based on the deviation amount from the planned running path of the grass mowing robot and the positional deviation offset amount" in this embodiment of the invention. Then, the process returns.

[0025] That is, the positional deviation offset amount ΔPo is the amount by which the grass mowing robot 1 is deflected with respect to the direction of the planned route L when traveling along the planned route L so as to cross the slope 11, and in steps S5 to S8, the positional deviation offset amount ΔPo is acquired by learning from the repeated occurrence of positional deviations within a predetermined value. The functional means for controlling steps S5 to S8 corresponds to the learning means in this embodiment of the present invention.

[0026] Then, the travel direction is adjusted based on the current positional deviation amount ΔPi and the positional deviation offset amount ΔPo, and the adjustment amount is therefore increased by the positional deviation offset amount ΔPo. As described above, this positional deviation offset amount ΔPo corresponds to the so-called lateral slippage that accompanies crossing the slope 11, and therefore the positional deviation due to the lateral slippage when returning to the scheduled route L can be corrected by this positional deviation offset amount ΔPo. In this case, the speed is maintained constant.

[0027] Fig. 3C shows a schematic diagram of a situation in which the traveling direction has been adjusted taking into account the positional deviation offset amount ΔPo. Until the positional deviation offset amount ΔPo is set, the adjustment amount of the traveling direction is limited to an amount based on the positional deviation amount ΔP, so the positional deviation caused by so-called sideslip cannot be corrected and the grass mowing robot 1 cannot return to the planned path L. In contrast, when the positional deviation offset amount ΔPo is set, the traveling direction (posture or orientation) of the grass mowing robot 1 is significantly adjusted to correct the positional deviation caused by so-called sideslip. As a result, the grass mowing robot 1 can return to a position on the planned path L.

[0028] FIG. 3C also shows the direction or posture of the mowing robot 1 after it has returned to a position on the planned route L. When the mowing robot 1 returns to the planned route L, the positional deviation between its own position and the planned route L is eliminated, and the current positional deviation amount ΔPi among the positional deviation amounts that determine the direction or posture of the mowing robot 1 becomes "0", so the running direction (posture or orientation) is adjusted based on the positional deviation offset amount ΔPo. In other words, since the positional deviation offset amount ΔPo remains even though the mowing robot 1 is positioned on the planned route L, the running direction (posture or orientation) of the mowing robot 1 is deviated from the planned route L by the positional deviation offset amount ΔPo. However, since the positional deviation offset amount ΔPo is intended to avoid or eliminate positional deviation due to so-called lateral slip on the slope 11, the mowing robot 1 will run along the planned route L even if its direction or posture is deviated from the planned route L. Therefore, it is possible to prevent or suppress repeated occurrence of positional deviations caused by so-called sideslip and adjustments of the traveling direction to correct the deviations.

[0029] If the determination in step S5 is negative, i.e., if the absolute value of the difference between the previous value and the current value of the positional deviation amount ΔP exceeds the threshold value A, the positional deviation counter Dc is reset (step S10), and the process proceeds to step S9, where the traveling direction is adjusted according to the positional deviation amount ΔP, and then the process returns. This is because, when the positional deviation amount ΔP is large, it is difficult to return the grass mowing robot 1 to the planned path L using control that corrects or eliminates the positional deviation due to so-called sideslip, or the cause of the positional deviation may not be so-called sideslip.

[0030] If the result of the determination in step S7 is negative, the process immediately proceeds to step S9, where the traveling direction is adjusted according to the positional deviation amount ΔP, and then the process returns. Although the absolute value of the difference between the previous value and the current value of the positional deviation amount ΔP is equal to or less than the threshold value A, if the number of repetitions is small, it is highly likely that the positional deviation is not due to so-called sideslip on a slope.

[0031] For comparison, the behavior of the mowing robot 1 when control is not performed that takes into account the above-mentioned positional deviation offset amount ΔPo when traveling across a slope to mow will be explained here. Fig. 4 shows a schematic diagram of changes in the relative value between the planned path L and the mowing robot 1. First, as shown in Fig. 4(A), a target position 13 is set at a start point 12, and a planned path L to the target position 13 is also set. At that point, the traveling direction (posture or orientation) of the mowing robot 1 coincides with the planned path L.

[0032] When the mowing robot 1 starts to travel, as shown in FIG. 4B, the mowing robot 1 deviates downward from the planned route L due to so-called lateral slippage. By detecting the amount of positional deviation ΔP, the travel direction (posture or orientation) of the mowing robot 1 is set to be diagonally upward so as to face the planned route L. The amount of adjustment in this case is an adjustment amount that is set in advance assuming that the mowing robot 1 will travel on a horizontal plane. The mowing robot 1 continues to travel with the travel direction adjusted in this way, but since so-called lateral slippage occurs each time the mowing robot 1 travels, the positional deviation is not eliminated. In other words, even if the travel direction of the mowing robot 1 is adjusted, the amount of adjustment is only an amount that corrects the positional deviation when traveling on a horizontal plane, and is not an adjustment that corresponds to the positional deviation due to so-called lateral slippage on the slope 11. Therefore, although the travel direction (posture or orientation) of the mowing robot 1 is diagonally upward with the aim of returning to the planned route L, the actual travel direction is downward by the amount of so-called lateral slippage from the orientation of the mowing robot 1, and the positional deviation from the planned route L cannot be eliminated. In other words, the target position 13 cannot be reached, and the grass cannot be mowed as intended.

[0033] Meanwhile, Fig. 5 shows a schematic diagram of a situation in which the control according to an embodiment of the present invention is executed when the mowing robot 1 travels on a horizontal plane to mow grass. As shown in Fig. 5(A), as in the above-mentioned example, a target position 13 is set at the start point 12, and a planned route L to the target position 13 is also set. At that point, the traveling direction (posture or orientation) of the mowing robot 1 coincides with the planned route L.

[0034] After the grass mowing robot 1 starts traveling, if the orientation of the grass mowing robot 1 temporarily changes due to one of the crawlers 5 entering a depression or running over a fallen object, as shown in FIG. 5B, the grass mowing robot 1 deviates from the planned path L and a positional deviation occurs. As a result, the traveling direction (posture or direction) of the grass mowing robot 1 is adjusted according to the positional deviation amount ΔP. The adjustment amount in this case is an adjustment amount set on the assumption that the grass mowing robot 1 will travel on the horizontal plane on which it is currently traveling. Therefore, the grass mowing robot 1 travels toward the planned path L and stays on the planned path L. In other words, when the traveling direction is adjusted and the grass mowing robot 1 travels, positional deviation does not occur repeatedly, so the above-mentioned positional deviation offset amount ΔPo is not set. Then, in the subsequent travel, the positional deviation amount ΔP becomes "0", so no adjustment according to the positional deviation amount ΔP in the traveling direction is made, and the grass mowing robot 1 travels toward the target position 13 along the planned path L, as shown in FIG. 5C. In other words, the control in the embodiment of the present invention can also be applied to the case where the grass mowing robot 1 travels on a horizontal plane. [Explanation of symbols]

[0035] 1. Grass-cutting robot 2 Cart Controller 3 Global Navigation Satellite System (GNSS) 4. LiDAR 5. Crawler 6 Speed ​​Controller 7 Cutter speed controller 8 Cutter Height Controller 9 Integrated Controller 10 horizontal plane 11 Slope 12 Starting Point 13 Target position ΔP, ΔPi, ΔPi-1 Positional deviation amount ΔPo Position offset amount L Planned route

Claims

[Claim 1] A travel control device for a grass-mowing robot configured to determine a planned travel path of the grass-mowing robot having a cutter for cutting grass growing on a travel surface, and to set an adjustment amount of the travel direction of the grass-mowing robot for returning the grass-mowing robot to the planned travel path when the grass-mowing robot deviates from the planned travel path according to an amount of deviation of the position of the grass-mowing robot from the planned travel path, a means for calculating a previous position deviation amount, which is a deviation of the position of the grass mowing robot from the planned travel path caused by the grass mowing robot traveling while adjusting the travel direction by the adjustment amount corresponding to the deviation amount; a means for determining the previous positional deviation amount as a positional deviation offset amount; a means for setting a travel direction of the grass-mowing robot based on an amount of deviation of the grass-mowing robot from the planned travel path and the amount of position deviation offset; A travel control device for a grass-mowing robot comprising:

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