A path planning and precise operation method for unmanned tractor operation

Abstract

The present invention provides a path planning and precise operation method for unmanned tractor operation that can fully cover the operation plot and improve the operation efficiency, thus realizing truly unmanned tractor operation. The present invention can realize full-path full planning for the target operation plot, completely cover the operation area, can adapt to any complex terrain, and the planned path conforms to the actual operation conditions of the current tractor. After the unmanned tractor automatically drives, no manual secondary supplementary operation is required. In view of the actual situation that the tractor has a large turning radius and is difficult to turn to the target operation row, the present invention proposes a variety of cross-row operation methods, so that the tractor can smoothly turn to the target operation row, and the steering wheel will not be turned suddenly during the turning process, making the driving process smoother and safer.

Description

Technical Field

[0001] This patent belongs to the field of agricultural machinery and involves intelligent agricultural machinery technology. More specifically, it involves a path planning and precise operation method for unmanned tractor operations. Background Art

[0002] In recent years, with the rapid development and maturity of satellite positioning technology, many automatic navigation systems based on satellite positioning technology have emerged in the agricultural field, greatly improving agricultural production and operation efficiency. However, at present, most agricultural machinery equipped with automatic navigation system products can only achieve "unmanned straight line" driving. In complex situations such as reversing, turning around, and turning, the driver still needs to manually operate the steering wheel, and has not truly achieved fully unmanned automatic driving.

[0003] The difficulty of fully unmanned autonomous driving agricultural machinery operations lies in the complex and changeable terrain of the fields. Currently, most navigation systems are too rigid and single in path planning for the working areas, resulting in different models often using the same path, which violates the actual working rules. In addition, precise adjustments and controls are not made for working details such as field boundaries, vertices, and corners of planned paths, resulting in frequent missed operations, necessitating manual secondary operations. Summary of the invention

[0004] To solve the above problems, the present invention provides a path planning and precise operation method for unmanned tractor operations that can fully cover the operating plots and improve operating efficiency based on the characteristics of tractors and operating plots, thereby realizing truly fully unmanned tractor operations.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A path planning and precision operation method for unmanned tractor operation, comprising a path planning step and a precision operation step;

[0007] The path planning step includes the following sub-steps:

[0008] Step 1: Get the parameter information of the tractor;

[0009] Step 2: Determine the field boundary according to the boundary point positioning information of the working field;

[0010] Step 3: Determine the path working width d, plan the entry position according to the tractor's starting working position, and plan the working path; the working path includes a plurality of circular outer circles and a plurality of inner circle parallel line segments, the interval between adjacent outer circles is the path working width d, and the distance between the inner circle parallel line segments is the path working width d;

[0011] The precise operation steps include inner circle operation steps and outer circle operation steps:

[0012] The inner ring operation step includes the following sub-steps:

[0013] Step 1: The unmanned tractor enters the inner circle from the side of the current position and selects the Nth path or the N+1th path close to the center of the inner circle to enter the inner circle;

[0014] Step 2: The tractor runs empty to the path near the center of the inner circle and aligns with the N path or the N+1 path. After the tractor runs along the path to a certain distance from the end point of the path, the farm implement is turned on and the operation starts along the current path.

[0015] Step 3: After the unmanned tractor completes the operation along the Nth path or the N+1th path, it ends the operation of this navigation line at the operation stop position of the path; the tractor stops and the agricultural machinery is turned off;

[0016] Step 4: Plan a turning path according to the turning radius of the vehicle, and the tractor backs up to the starting point of the turning path; then the vehicle stops, controls the steering wheel to turn, and starts turning; according to the turning path, it directly drives across M rows or M+1 rows to another path;

[0017] Step 5: After entering another path, the vehicle stops, and based on the vehicle's reverse route, the steering wheel is turned to the specified position. After the wheels are turned to the required angle, the vehicle starts to reverse along the path, so that the agricultural implement position reaches the starting point of the operation position of the most edge path. At this time, the vehicle has aligned with the path, and the tractor engine speed is controlled to reach the working speed. The agricultural implement is turned on, the vehicle moves forward, and the unmanned tractor starts to operate on the path, completing the straight line operation on the path;

[0018] Repeat steps 4-5 to complete each inner circle path operation;

[0019] The outer ring operation step includes the following sub-steps:

[0020] The tractor turns from the stop point of the last path of the inner circle and drives into the innermost outer circle of the outer circle; the tractor works along the outer circle guidance line, and continues to sweep the circle outward after the work of the circle is completed. When changing adjacent outer circles, the tractor drives one more guidance line width at the corner of the current work completion circle and then drives onto the next outer circle until all outer circles are completed;

[0021] At each outer corner, turn by:

[0022] After the tractor completes the operation on one side of the outer circle, turn off the agricultural implement, reverse to the starting point of the turning path, control the steering wheel to turn to the next working row with a safe minimum turning radius, and reverse along the direction of the working row to the starting working position of the working row.

[0023] Furthermore, the inner circle parallel line segments are parallel to the longest side of the field boundary, and both ends of the parallel path are extended to the short side of the outermost sweeping circle, and the distance from the long side of the innermost sweeping circle is d.

[0024] Furthermore, the inner circle parallel line segments include a plurality of inner circle units.

[0025] Furthermore, in step 2 of the inner circle operation step, after the tractor enters the field boundary, it first runs along the short side outer circle. When the tractor travels from the outer circle to the initial path, the vehicle speed is reduced; when the tractor moves forward to the starting point of the turning path calculated according to the turning radius, the vehicle stops, the steering wheel is controlled to turn, and after the wheel steering angle reaches the set value, the vehicle moves forward and turns to the initial path.

[0026] Furthermore, in step 2 of the inner circle operation step, after the unmanned tractor drives to the initial path along the turning path calculated according to the turning radius, the vehicle stops, and the steering wheel is turned to a specified position based on the vehicle's reverse route. After the wheels turn to the required angle, the vehicle starts to reverse and starts to reverse along the initial path, so that the operating position of the agricultural machinery reaches the starting point of the operation.

[0027] Furthermore, both ends of the working path are extended by a certain distance l, where l = width of the agricultural implement * coefficient.

[0028] Furthermore, when the inner circle parallel line segment includes several inner circle units, for each unit, the inner circle operation steps 1-5 are performed until the operation is completed, and then the operation is continued to the next inner circle unit until the operation of all inner circle units is completed.

[0029] Furthermore, when the number of paths in the inner circle unit does not meet 2N, any of the following two special crossing modes is used to achieve adjacent path crossing when entering the last path:

[0030] Interbank method 1:

[0031] Step 1: After the tractor completes the operation along the penultimate straight path of the unit, the operation of this navigation line is ended at the operation stop position of the path, and the tractor stops, and the agricultural machinery stops;

[0032] Step 2: Plan the turning path according to the turning radius of the vehicle, and the tractor backs up to the starting point of the turning path; the vehicle stops, controls the steering wheel to turn, and drives along the turning path to the outermost sweeping path parallel to the outer boundary, and starts turning; when the tractor turns and drives to the outermost sweeping path, the tractor backs up to the starting point of the turning path; the vehicle stops, controls the steering wheel to turn, starts turning, and drives directly to the last path of the unit according to the turning path;

[0033] Step 3: After entering the last path of the unit, the vehicle stops, and based on the vehicle's reverse route, the steering wheel is turned to the specified position, and the wheel is turned to the required angle before starting to reverse, and the vehicle starts to reverse along the last path, so that the rotary tiller's rotary tillage position reaches the starting point of the operation position of the path. At this time, the vehicle has aligned with the route; the tractor engine speed is controlled to reach the working speed, the auxiliary power output is turned on, the agricultural machinery is turned on, the vehicle moves forward, and the unmanned tractor starts to operate on the path;

[0034] Interbank method 2:

[0035] Plan a three-section arc turning path. The tractor stops at the starting point of the first arc. The tractor is controlled to turn forward and away from the destination path. After reaching the connection point of the first arc and the second arc, the tractor is controlled to turn forward and close to the destination path. After reaching the connection point of the second arc and the third arc, the tractor is controlled to turn forward and in the direction of the destination path and enter the destination path. After reaching the end of the third arc, the vehicle stops, the agricultural machinery is opened, and the vehicle moves forward to complete the operation.

[0036] Furthermore, when the outer circle turns, the distance between the starting point of the turning path and the turning point is

[0037] Furthermore, when the tractor travels from the inner circle to the outer circle, it adopts a straddling manner to turn into the outer circle.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] 1. The present invention can realize full-path planning for the target operation plot, completely cover the operation area, adapt to any complex terrain, and the planned path conforms to the actual operation situation of the current tractor. After the unmanned tractor automatically drives the operation, no manual secondary operation is required.

[0040] 2. In view of the actual situation that the tractor has a large turning radius and is difficult to turn to the target working row, the present invention proposes a variety of cross-row operation methods, so that the tractor can be smoothly turned to the target working row, and the steering wheel will not be turned suddenly during the steering process, making the driving process smoother and safer.

[0041] 3. The present invention optimizes the tractor's reversing and steering actions at the corners of the planned path, avoids missing operations, and improves land utilization and operating efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the land boundaries.

[0043] Figure 2 This is a schematic diagram of the first edge sweeping circle in the U-shaped path.

[0044] Figure 3 This is a schematic diagram of the second and third sweeping circles in the U-shaped path.

[0045] Figure 4 This is a schematic diagram of the inner circle parallel line segments.

[0046] Figure 5 This is a schematic diagram of a tractor turning across rows.

[0047] Figure 6 This is a schematic diagram of the overall path planning of the tractor.

[0048] Figure 7 This is a schematic diagram of the tractor's step-by-step process.

[0049] Figure 8 This is a schematic diagram of the tractor's operation after crossing rows.

[0050] Fig. 9 This is a schematic diagram of the tractor traveling across units.

[0051] Fig.10 A step-by-step diagram of the interbank method.

[0052] Fig.11 A step-by-step diagram of the interbank method.

[0053] Fig.12 A step-by-step diagram of the interbank method.

[0054] Fig.13 This is a schematic diagram of the path of the inter-bank method.

[0055] Fig.14 This is a schematic diagram of the second path of the interbank method.

[0056] Fig.15 This is a schematic diagram of working at the corner of the tractor's outer circle.

[0057] Fig.16 It is a schematic diagram of the tractor performing a U-shaped outer circle operation from the inside to the outside in the example.

[0058] Fig.17 This is a schematic diagram of the path planning in the example.

[0059] Fig.18 This is a schematic diagram of the tractor turning to enter path No. 5 in the inner circle unit 1 in the example.

[0060] Fig.19 This is a schematic diagram of the tractor turning from path 5 to path 1 in the example.

[0061] Fig. 20 This is a schematic diagram of the tractor operating on path No. 1 in the example.

[0062] Fig.21It is a schematic diagram of the tractor operating across rows in the inner circle unit 1 in the example.

[0063] Fig. 22 The diagram is a cross-row diagram of the tractor in the example.

[0064] Fig.23 This is a schematic diagram of the tractor adopting the two-row straddling method in the example. DETAILED DESCRIPTION

[0065] The technical solution provided by the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the following specific implementation methods are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0066] The present invention provides a path planning and precision operation method for unmanned tractor operation, which mainly includes path planning steps and precision operation steps, wherein the path planning step includes full path planning of the entire field, including planning of sweeping circles and inner circles, and also includes planning of the tractor's starting point to enter the circle position, the logic of changing circles, the turning methods at different circle corners, and the start and stop actions of the tractor. Specifically, the specific steps of the unmanned tractor operation path planning are:

[0067] Step 1: Obtain the parameter information of the tractor, mainly including the minimum turning radius for left turn, the minimum turning radius for right turn, and the working width of the mounted agricultural implement;

[0068] Step 2: The field outline can be approximately viewed as a polygon. The unmanned tractor positioning module obtains the boundary point positioning information of the working field, and determines the field boundary based on the boundary point positioning information of the working field. Specifically, the longitude and latitude of the boundary points of the working field are obtained in sequence, and the closed figure generated by connecting them is used as the field boundary. Figure 1 The middle boundary points are Z1, Z2, Z3, and Z4, based on which a closed quadrilateral is generated.

[0069] Step 3: Determine the path operation width d, plan the entry position according to the tractor's starting operation position, and plan the operation path;

[0070] Specifically, due to the accuracy error of the automatic driving system, in order to avoid missing operations, the determination of the path operation width should set an appropriate overlap width, that is, the path operation width = the operation width of the tractor mounted agricultural implements - the overlap width;

[0071] The tractor operation path is a combination of a U-shaped path (sweeping circle) and parallel line segments (inner circle). Each line segment path is parallel to its corresponding boundary segment. The overall path is composed of the sweeping circle and inner circle operation units. The interval between the line segment paths is the operation width of the above path.

[0072] The principle of path sweeping circle planning is as follows:

[0073] like Figure 2 As shown, the first sweeping circle is formed by a closed boundary obtained by proportionally reducing the field boundary by half the path operation width; Figure 3 As shown, the second, third, ..., K outer circles are generated in a U-shaped pattern according to the path operation width; that is, the interval between adjacent outer circles is the path operation width d.

[0074] The principle of inner circle planning of the operation path is as follows:

[0075] The inner circle operation path is a number of line segments parallel to the longest side of the field boundary, and the distance between the line segments is the path operation width d.

[0076] Specifically, since the turning radius of the tractor is large, adjacent row operations can easily cause the vehicle to turn too sharply or even get stuck. Therefore, the cross-row operation method is used to make the tractor turn more smoothly. The number of cross-rows of the tractor is determined based on the relative size relationship between the path operation width and the minimum turning radius of the tractor's left turn and the minimum turning radius of the tractor's right turn:

[0077] The tractor's current operation is recorded as row P, the number of rows crossed is M, and N = M + 1. The tractor should then cross to row P + N or PN to operate. Thus, every 2N operation rows is calculated as a basic unit (when the tractor enters the circle from the bottom of the field, the inner circle operation rows are numbered from left to right). Figure 4 As shown, the tractor can achieve turning across M rows in this unit.

[0078] Specifically, the tractor selects a path close to the center of the inner circle to enter the inner circle, namely, path N (the tractor turns right at the end of the path) or path N+1 (the tractor turns left at the end of the path), and path N+1 is described in detail, as shown in FIG. Figure 5 As shown, the cross-line method is: We believe that the tractor can start operation from above or below the inner circle path. Figure 5 Instructions for turning across rows when driving upward in the middle and lower directions: when the tractor starts working from the top of path N+1, it should turn right at the end of the path and cross the row to path 1; when the tractor starts working from the top of path N, it should turn left at the end of the path and cross the row to path 2N...Obviously, when the tractor starts working from the top of the field, the overall path is basically the same as starting working from the bottom of the path, but the tractor is driving in the opposite direction.

[0079] The direction of the parallel path in the inner circle operation unit is consistent with the longest side of the field boundary to reduce the number of cross-rows; the two ends of the parallel path of the inner circle operation unit are extended to the short side of the outermost sweeping circle, and the distance from the long side of the innermost sweeping circle is d. The final planned tractor complete path is as follows: Figure 6 shown.

[0080] As an improvement, the inner circle can be divided into several inner circle units. After the cross-row operation of one unit is completed, the tractor can navigate to the starting point of the Nth path or the N+1th path of another unit through the outer circle navigation line to start the operation. Fig. 9 Obviously, each unit path should be numbered independently, and the number of all inner circle parallel paths within the boundary of a field should preferably be a multiple of 2N, but it is also possible that the number of paths in a unit is less than 2N.

[0081] The specific steps of the precise operation method of the unmanned tractor are:

[0082] First, the unmanned tractor performs inner circle operations, which are detailed as a complete inner circle operation unit, that is, 2N operation paths:

[0083] Step 1: The unmanned tractor enters the inner circle from the side of the current position and selects a path close to the center of the inner circle to enter the inner circle, that is, path N or path N+1, with path N+1 being used for detailed description;

[0084] Step 2: Run the tractor to the bottom of the N+1 path and align it with the path. Figure 7 (1) in ; After the tractor travels along the path to a certain distance from the end point of the path, Figure 7 (2) in; open the farm implements, such as Figure 7 (3) in the figure, start working along the current path;

[0085] Specifically, after the tractor enters the boundary of the field, it first runs idle along the outer circle of the short side. When the tractor travels from the outer circle to the bottom or top of the N+1 path, the vehicle speed is reduced (the power reversing tractor decelerates through the throttle control, and the continuously variable transmission tractor decelerates through the throttle and HST control). Running idle means lifting the agricultural implements mounted on the tractor and turning off the power output (some agricultural machinery does not need to be lifted, just turned off). Since the edge of the outer circle where the tractor is located is nearly perpendicular to the inner circle path at this time, the tractor needs to turn to align with the inner circle path, and the turning path needs to be calculated in advance according to the turning radius. When the tractor moves forward to the starting point of the turning path calculated according to the turning radius, the vehicle stops (the power reversing tractor is in the stop position, the continuously variable transmission control HST is at zero position, and other modified tractors are controlled by the handle motor), and the steering wheel is controlled to turn so that the wheel steering angle is θ 1 ,θ 1 = Maximum steering angle of the wheel * protection factor 0.95 (protection factor is also another value that can be set by yourself. The turning radius is calculated according to the maximum steering angle of the wheel, so the wheel rotation needs to be the maximum when turning according to the minimum turning radius). It is designed to control the wheel steering so that it does not exceed the maximum steering angle of the tractor to avoid damage to the rotating shaft or other parts of the tractor. When the wheel steering angle reaches θ 1After that, the vehicle moves forward (the power shift is changed to the forward gear, and the continuously variable transmission control HST is in the low-speed forward position) and turns to the N+1 path.

[0086] As an improvement, after the unmanned tractor drives along the turning path calculated according to the turning radius to the N+1 path, the vehicle stops and turns the steering wheel to the specified position based on the vehicle's reverse route (in control logic, the protection factor is only needed when turning according to the minimum turning radius and the wheel turning is at the maximum angle. Here, it is a small-angle turn, and the wheel rotation angle can be turned according to actual needs). After the wheels turn to the required angle, they start to reverse and start to reverse along the N+1 path, so that the working position of the agricultural machinery (the agricultural machinery can be a rotary tiller, a pesticide spraying kit, a plow, etc.) reaches the starting point of the operation.

[0087] As an improvement, in order to avoid missing operations, both ends of the operation path are extended by a certain distance to ensure that the path is fully operated. This distance is denoted as l. This length can be manually modified and set according to the mechanical status of the unmanned tractor. It is generally 0.5 times the length of the agricultural machinery (the set value is a coefficient greater than or equal to zero, l = agricultural machinery width * coefficient). The coefficient can be modified according to different needs. The coefficient can be set to 0, that is, this distance will not be extended.

[0088] When working in the inner circle, it is necessary to calculate the positions of the tractor's starting and ending points. When the extended distance is l, the distance between the working position of the agricultural implement and the first outer circle guidance line of the edge sweeping is the extended working distance l (the working position of the agricultural implement exceeds the guidance line l). The single working range of the inner circle is the length from the starting point to the end point multiplied by the width of the agricultural implement to form a straight line strip range.

[0089] When the N+1 navigation line is aligned and the operation position is reached, the engine speed reaches the set working speed, the agricultural implement is turned on, and the unmanned tractor starts to operate on the N+1 path after waiting for a period of time t. The waiting time t is a settable parameter to ensure that the auxiliary power output reaches the rated speed before starting to work, to prevent the engine from stalling due to a sudden increase in load at low speed, which can also easily increase vehicle losses. Figure 7 A hollow square representing a tractor indicates that the implement is raised and the power take-off is off, while a solid square indicates that the implement is lowered and the power take-off is on.

[0090] Step 3: After the unmanned tractor completes the operation along the N+1 straight line path, it ends the operation of this navigation line at the operation stop position of the N+1 straight line. Figure 7 (4) in the tractor stops, raises the rear suspension, and when the rear suspension is raised to a certain height (the agricultural implement is completely off the ground), turns off the auxiliary power output, such as Figure 7(5) (This lifting height can be finely adjusted according to the performance and size of the vehicle itself to ensure compatibility with various tractors). Control the engine speed to drop to the non-operating state requirement. After stopping, turn off the agricultural implement to avoid incomplete operation at the end of the operation. Reducing the engine speed can reduce fuel consumption and slow down the speed, improve the controllability of the vehicle during subsequent turning, and reduce the wear of the agricultural implement to protect the agricultural implement.

[0091] Step 4: Plan the steering path according to the turning radius of the vehicle. The tractor reverses backward to the starting point of the steering path, as Figure 7 in (6). The reversing length is w. The vehicle stops, and the steering wheel is controlled to turn so that the wheel steering angle is θ 1 , and start steering; Drive directly along the steering path to Path 1 (when starting from Path N, drive to Path 2N at this time), as Figure 7 in (7).

[0092] Step 5: After driving into Path 1, the vehicle stops. Based on the vehicle's reverse route, turn the steering wheel to the specified position. After the wheels turn to the required angle, start reversing and reverse along Path 1 until the tilling position of the rotary tiller reaches the starting point of the working position of Path 1. At this time, the vehicle is already aligned with Route 1, and the agricultural implement is at a distance l from the path, as Figure 7 in (8); Control the engine speed of the tractor to reach the working speed and turn on the agricultural implement. After waiting for a certain time t for the auxiliary power output to rotate, the rear suspension descends, as Figure 7 in (9), so that the agricultural implement reaches the set working height (if the agricultural implement does not need to be lifted, this step can be omitted, and only start working after waiting for time t). The vehicle moves forward, and the driverless tractor starts working on Path 1 and completes the straight-line operation on Path 1, as shown in Figure 8.

[0093] Repeat Steps 1 - 5 to complete the operations on Path N + 2 to Path 2 to Path N + 3 to... to Path 2N to Path N, as Figure 5 shown.

[0094] As an improvement, the inner circle is composed of several units. The operation mode of each unit follows the above Steps 1 - 5. After each unit completes the operation, the vehicle automatically crosses the unit (essentially also crosses rows) and drives to the starting straight line of another unit to continue the operation, as Fig. 9 shown.

[0095] Specifically, when the number of paths in a certain unit of the inner circle is less than 2N, there will inevitably be row crossings with a number of row crossings less than M. Still taking Path N + 1 as the starting operation path for detailed description:

[0096] Denote the number of paths in a certain unit of the inner circle as 2N - S (1 ≤ S < N). Taking S = 1 as an example for detailed description:

[0097] When the number of paths in a cell in the inner circle is 2N-1, the cross-row method is:

[0098] in, The number of rows that can be crossed may be less than M, that is, the vehicle cannot enter the next row even if the steering wheel is tightened and the minimum turning radius is turned. Here are two feasible ways to cross rows:

[0099] Interbank method 1:

[0100] Step 1: Perform operations on path N-1, such as Fig.10 (10) in the figure; after the unmanned tractor completes the operation along the N-1 straight line path, it ends the operation of this navigation line at the operation stop position of the N-1 straight line, and the tractor stops. Fig.10 (11) in; Raise the rear suspension. When the rear suspension is raised to a certain height, turn off the auxiliary power output and control the engine speed to drop to the non-operating state requirement, such as Fig.10 (12) in;

[0101] Step 2: Plan the turning path according to the turning radius of the vehicle. The tractor reverses to the starting point of the turning path, as shown in (13) in Figure 11; the vehicle stops and the steering wheel is controlled to turn so that the wheel steering angle is θ 1 , follow the turning path to the outermost sweeping path parallel to the outer boundary, and start turning, such as Fig.11 (14) in ; when the tractor turns and drives to the outermost sweeping path, the tractor reverses to the starting point of the turning path, such as Fig.11 (15) in the figure; the vehicle stops, and the steering wheel is controlled to rotate so that the wheel steering angle is θ 1 , start turning, and drive directly to path N according to the turning path, such as Fig.12 in (16).

[0102] Step 3: After entering the Nth path, the vehicle stops and, based on the vehicle's reverse route, turns the steering wheel to the specified position. After the wheels turn to the required angle, the vehicle starts to reverse along the Nth path until the rotary tiller reaches the starting point of the operation position of the Nth path. At this time, the vehicle has been aligned with the Nth path, and the agricultural implement is l away from the path. Fig.12 (17) in; controlling the tractor engine speed to reach the working speed, turning on the auxiliary power output, such as Fig.12 After the auxiliary power output has been rotated for a certain waiting time t, the rear suspension is lowered, so that the agricultural implement reaches the set working height, the vehicle moves forward, and the unmanned tractor starts to work on path N (19), completing the straight line operation on path N.

[0103] The complete path of interbank method 1 is as follows Fig.14 As shown, the order of the numbers in the path is the order of the tractor's step-by-step movement path across rows.

[0104] Interbank method 2:

[0105] Take L1 turning right into L2 as an example to explain in detail:

[0106] The planned turning path consists of three arcs. The first arc With the second arc The concavity and convexity are opposite, point B is The inflection point of the second arc With the third arc The concavity and convexity are opposite, and point C is The turning point;

[0107] After the unmanned tractor completes the operation along the current straight line L1, the tractor stops at point A and lifts the rear suspension. When the rear suspension is lifted to a certain height, the auxiliary power output is turned off, the engine speed is controlled to drop to the non-operating state requirement, the speed is slowed down, and the tractor is controlled to turn forward and left (essentially the side away from the target direction). After reaching point B, it turns forward and right (essentially the side close to the target direction). After reaching point C, it turns forward and left (essentially the side aligned with the target path) and drives towards L2. After reaching point D, the vehicle stops, the tractor engine speed is controlled to reach the working speed, and the auxiliary power output is turned on. After the auxiliary power output rotation waiting time t is certain, the rear suspension is lowered, so that the agricultural machinery reaches the set operating height, the vehicle moves forward, and the unmanned tractor starts to work on the L2 path, completing the L2 path straight line operation.

[0108] Specifically, in the AB and CD segments, the wheel steering angle is a smaller wheel angle determined according to the actual situation, and the steering wheel is adjusted in real time according to the required wheel angle; in the BC segment, the vehicle turns according to the minimum turning radius, and the steering wheel controls the wheel rotation angle θ 1 To fix it unchanged, complete the turning.

[0109] Through the second crossing method, it is possible to directly turn to the adjacent path.

[0110] Cross-row method 1 involves more operations such as overall turning and reversing, and has more complicated steps. It takes longer to implement than cross-row method 2, but its operating space is small and it is not easy to cover other paths or exceed the field boundaries. Cross-row method 2 requires a longer implementation distance at the field head, but its operating actions are simple and easy to implement, and it is faster and more efficient.

[0111] In the above manner, the tractor can complete automatic navigation operations along all inner circle paths.

[0112] After completing all the inner circle parallel straight paths, the unmanned tractor performs the outer circle operation in a U-shaped pattern from the inside to the outside;

[0113] The tractor turns from the stopping point of the last path of the inner circle to enter the third outer circle which is the innermost. If the distance is appropriate, the conventional steering method can be used. When the distance is short, the straddling method can be used to turn into the outer circle.

[0114] The tractor operates along the outer circle guidance line. After the third outer circle is completed, it continues to sweep the circle outward. When the third outer circle changes to the second outer circle, it drives one more guidance line width at the lower right corner of the third outer circle, and then it can directly drive onto the second outer circle. It continues to sweep and change circles until all outer circles are completed. The operation method at the corner of the outer circle is explained by taking a left turn as an example;

[0115] like Fig.15 As shown in (22), the current operation path is the path where EF is located, the next operation path is the path where FG is located, the turning point of the two paths is point F, the angle between the two paths is α, and the radius of the dotted circle is the minimum turning radius Rl of the tractor turning left, where Rl is θ obtained by multiplying the maximum steering angle of the wheel by the steering safety factor. 1 Calculate the minimum turning radius of the vehicle.

[0116] The dotted circle is tangent to EF and FG at the same time, and the tangent points are point E and point G respectively. Point E is the starting point of the turning path for the tractor to turn at this point. All the turning actions after reversing are to start turning the steering wheel after reversing to this starting point to prepare for turning; point G is the ending point of the turning path for the tractor to turn at this point. After turning according to the turning path, the tractor returns to the correct steering wheel at point G and starts to drive in a straight line.

[0117] After the tractor completes the current operation (22-23), it raises the implement and turns off the power output of the implement, and reverses to a distance of After reaching point E, Fig.15 (24) in the figure; control the steering wheel to turn left until the wheel angle is θ 1 , turn to the next operation line with the safe minimum turning radius, such as Fig.15 (25); reverse along the working row direction to the starting working position of the working row (26), lower the agricultural implement and turn on the power output of the agricultural implement to start working (27).

[0118] It should be noted that the aforementioned “reverse to the distance from the corner point is After reaching point E, control the steering wheel to turn left until the wheel angle is θ 1 , turn to the next working line with the safe minimum turning radius", which means that the distance between the reversing point and the corner point is at least The distance can also be greater than When the distance is greater than When the system controls the steering wheel to turn left to the next operation line, the difference is that the steering wheel does not need to be turned all the way to turn left to the next operation line. The turning radius at this time is greater than R l The θ 1 The maximum turning radius * a freely set coefficient parameter less than 1. The steering angle must be less than the maximum turning angle. This avoids the special situation of unmanned driving of the tractor resulting in the steering wheel being used in the extreme position multiple times, slows down the loss of the steering motor, and reduces the possibility of dangerous accidents.

[0119] Specifically, under the premise that the turning radius is fixed, the larger the angle α between the current working row and the next working row (α∈(0,180)), the shorter the tractor reversing distance, that is, the shorter the EF segment (also known as the FG segment) shown in the figure.

[0120] Examples:

[0121] The following is an example of a quadrilateral field to fully describe the tractor's path planning and operation process:

[0122] Path planning steps:

[0123] Step 1, obtain the parameter information of the tractor, mainly including the limit of the vehicle turning left, the steering safety factor, the safe minimum turning radius, and the working width of the mounted agricultural implements. In this embodiment, an EN954 tractor is selected, the steering is controlled by a steering motor, the maximum steering angle is 40°, the safety factor is 0.9, and the wheel rotation angle θ 1 The angle is 36° and the agricultural implement is a 2.2m wide rotary tiller.

[0124] Step 2, taking a quadrilateral field as an example, use a positioning device to sequentially obtain the latitude and longitude position information of the field boundary points, connect them sequentially to generate the field boundary, and calculate the length of each boundary, recorded as L1, L2, L3, L4.

[0125] Step 3: Determine the path width. The autonomous driving system plans the all-terrain path and the position of the circle according to the land boundary, the starting point of the operation and the width of the operation. Fig.17 As shown, the tractor operates across 3 rows, and the generated inner circle path consists of 2 units, unit 1 consists of 2*(3+1)=8 straight line paths, unit 2 consists of 2 straight line paths, a total of 10 paths, numbered from 1 to 10, and the path planning is a counterclockwise path.

[0126] Precision operation steps:

[0127] Unmanned tractor performs inner circle operations:

[0128] Step 1: Enter the inner circle unit 1 from the left along the outer circle navigation line. At this time, the engine speed is 1000 rpm. Choose a path close to the center of the inner circle unit 1 to enter the inner circle;

[0129] Step 2, such as Fig.18 As shown, the tractor runs to the starting point of the No. 5 path, controls the power reversing at the stop position, controls the steering motor until the wheel turns left 36°, and then starts to turn. After reaching the No. 5 path, controls the steering motor wheel to return to the center, and reverses to the starting point of the No. 5 path operation. Adjust the throttle to increase the engine speed to 2000 rpm, turn on the auxiliary power output, the rotary tiller rotates, the power reversing to the forward gear, lower the rear suspension height to the height where the rotary tiller is immersed in the land (the lowest), and start working along the current path;

[0130] Step 3, after the unmanned tractor completes the operation along the straight path No. 5, it continues to travel along the path No. 5 to extend the operation. After operation l, the farm implement is lifted, the throttle is reduced to lower the engine to 1000 rpm, and the power output of the farm implement is turned off;

[0131] Step 4: The tractor reverses a certain distance, controls the steering motor to turn the wheels 36° to the left, and drives to path 1 according to the steering path. Fig.19 As shown;

[0132] Step 5. After entering Path 1, the tractor reverses until the body is parallel to the No. 1 navigation line, adjusts the wheel angle, and drives in a straight line along Path 1. At the start point of Path 1, adjust the throttle to increase the engine speed to 2000 rpm, turn on the rotary tiller, shift the power to the forward gear, lower the rear suspension height to the height where the rotary tiller is immersed in the land, and complete the Path 1 operation. Fig. 20 shown.

[0133] Repeat steps 1-5 to complete At this point, the paths 1-8 of the inner ring unit 1 have all been completed. Fig.21 shown.

[0134] Cross-unit work:

[0135] The vehicle automatically drives to path 10 of unit 2 to continue the operation. After the operation on path 10 is completed, it turns from path 10 to path 9;

[0136] Way 1 to cross from Route 10 to Route 9:

[0137] Step 1: After the unmanned tractor completes the operation along the current No. 10 straight line, it lifts the farm implement, reduces the throttle and the engine speed drops to 1000 rpm, turns off the auxiliary power output, and stops the rotary tiller;

[0138] Step 2, the tractor power is switched from forward to stop to reverse gear (to avoid vehicle loss caused by direct switching and reduce the bumps caused by drastic changes in speed), reverse to the starting point of the turning path, power switch to stop gear, control the steering motor to turn the wheel left 36°, power switch to forward gear, and start driving. When the steering is perpendicular to the path, the power is switched from forward to stop to reverse gear, reverse to the starting point of the turning path, power switch to stop gear, control the steering motor to turn the wheel left 36°, power switch to forward gear, start driving and control the vehicle to enter path No. 9;

[0139] Step 3. After entering Path No. 9, reverse again until the distance from the end point of the path is l, adjust the throttle to increase the engine speed to 2000 rpm, turn on the rotary tiller, switch the power to the forward gear, lower the rear suspension height to the height at which the rotary tiller is immersed in the ground, and complete the operation on Path No. 9.

[0140] The second way to cross from Route 10 to Route 9:

[0141] After the unmanned tractor completes the operation along the current No. 10 straight line, it lifts the farm implement, reduces the throttle and the engine speed to 1000 rpm, turns off the auxiliary power output, stops the rotary tiller, and controls the steering motor to turn right at a certain small angle of 10° to 20° (adjusted in real time according to the path calculation to ensure that it is on the path). After reaching the first turning point, the steering motor is controlled to turn the wheel 36° to the left and maintain this angle to complete the arc turning. After reaching the second turning point, the steering motor is controlled to return the wheel to the right at a small angle of 10° to 20° to align the tractor with the No. 9 path. After entering the No. 9 path, the throttle is adjusted to increase the engine speed to 2000 rpm, the rotary tiller is turned on, and the rear suspension height is lowered to the height at which the rotary tiller is immersed in the land to complete the No. 9 path operation. The whole process is as follows: Fig.23 shown.

[0142] After completing all the inner circle parallel straight paths, the unmanned tractor performs the outer circle operation in a U-shaped pattern from the inside to the outside, such as Fig.16 As shown:

[0143] When the tractor is operating at the outer steering angle of each circle, after completing the straight line operation of the current edge sweeping navigation line, lift the rotary tiller to the highest position, reduce the throttle and reduce the engine speed to 1000 rpm, turn off the auxiliary power output, stop the rotary tiller, and reverse the power from forward to stop to reverse. The tractor retreats to the starting point of the turn, the power reversal stops, and the steering motor is controlled to turn the wheels to 36° left. The power is reversed to the forward gear and the tractor starts to turn left.

[0144] After turning to the next edge sweeping navigation line, the steering motor controls the wheel to return to the center and corrects the wheel steering angle according to the alignment navigation line. The power is reversed from forward to stop to reverse. After the tractor reverses to the starting point of the operation, the throttle is adjusted to increase the engine speed to 2000 rpm, the rotary tiller is turned on, the power is reversed to the forward gear, the rear suspension height is lowered to the height where the rotary tiller is immersed in the land, and the straight line operation of the current edge sweeping navigation line is started.

[0145] When changing circles Fig.16 As shown, drive one more navigation line width at the lower right corner, move directly from the current loop to the outer loop navigation line, and repeat the operation until all field operations are completed.

[0146] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A path planning and precision operation method for unmanned tractor operation, including a path planning step and a precision operation step; Features: The path planning step includes the following sub-steps: Step 1: Get the parameter information of the tractor; Step 2: Determine the field boundary according to the boundary point positioning information of the working field; Step 3: Determine the path working width d, plan the entry position according to the tractor's starting working position, and plan the working path; the working path includes a plurality of circular outer circles and a plurality of inner circle parallel line segments, the interval between adjacent outer circles is the path working width d, and the distance between the inner circle parallel line segments is the path working width d; The precise operation steps include inner circle operation steps and outer circle operation steps: The inner ring operation step includes the following sub-steps: Step 1: The unmanned tractor enters the inner circle from the side of the current position and selects the Nth path or the N+1th path close to the center of the inner circle to enter the inner circle; Step 2: The tractor runs empty to the path near the center of the inner circle and aligns with the N path or the N+1 path. After the tractor runs along the path to a certain distance from the end point of the path, the farm implement is turned on and the operation starts along the current path. Step 3: After the unmanned tractor completes the operation along the Nth path or the N+1th path, it ends the operation of this navigation line at the operation stop position of the path; Stop the tractor and turn off the farm implements; Step 4: Plan a turning path according to the turning radius of the vehicle, and the tractor backs up to the starting point of the turning path; then the vehicle stops, controls the steering wheel to turn, and starts turning; according to the turning path, it directly drives across M rows or M+1 rows to another path; Step 5: After entering another path, the vehicle stops, and based on the vehicle's reverse route, the steering wheel is turned to the specified position. After the wheels are turned to the required angle, the vehicle starts to reverse along the path, so that the agricultural implement position reaches the starting point of the operation position of the most edge path. At this time, the vehicle has aligned with the path, and the tractor engine speed is controlled to reach the working speed. The agricultural implement is turned on, the vehicle moves forward, and the unmanned tractor starts to operate on the path, completing the straight line operation on the path; Repeat steps 4-5 to complete each inner circle path operation; When the inner circle parallel line segment includes several inner circle units, follow the inner circle operation steps 1-5 for each unit until the operation is completed, then jump to the next inner circle unit and continue the operation until all inner circle units are completed; When the number of paths in the inner circle unit does not meet 2N, when entering the last path, any of the following two special crossing methods is used to achieve adjacent path crossing: Interbank method 1: Step 1: After the tractor completes the operation along the penultimate straight path of the unit, the operation of this navigation line is ended at the operation stop position of the path, and the tractor stops, and the agricultural machinery stops; Step 2: Plan the turning path according to the turning radius of the vehicle, and the tractor backs up to the starting point of the turning path; the vehicle stops, controls the steering wheel to turn, and drives along the turning path to the outermost sweeping path parallel to the outer boundary, and starts turning; when the tractor turns and drives to the outermost sweeping path, the tractor backs up to the starting point of the turning path; the vehicle stops, controls the steering wheel to turn, starts turning, and drives directly to the last path of the unit according to the turning path; Step 3: After entering the last path of the unit, the vehicle stops, and based on the vehicle's reverse route, the steering wheel is turned to the specified position, and the wheel is turned to the required angle before starting to reverse, and the vehicle starts to reverse along the last path, so that the rotary tiller's rotary tillage position reaches the starting point of the operation position of the path. At this time, the vehicle has aligned with the route; the tractor engine speed is controlled to reach the working speed, the auxiliary power output is turned on, the agricultural machinery is turned on, the vehicle moves forward, and the unmanned tractor starts to operate on the path; Interbank method 2: Plan a three-section arc turning path. The tractor stops at the starting point of the first arc, controls the tractor to turn forward and away from the target path, and after reaching the connection point of the first arc and the second arc, controls the tractor to turn forward and toward the target path. After reaching the connection point of the second arc and the third arc, controls the tractor to turn forward and toward the target path, and enters the target path. After reaching the end of the third arc, controls the tractor to stop, opens the agricultural implement, and then controls the tractor to move forward to complete the operation. The outer ring operation step includes the following sub-steps: The tractor turns from the stop point of the last path of the inner circle and drives into the innermost outer circle of the outer circle; the tractor works along the outer circle guidance line, and continues to sweep the circle outward after the work of the circle is completed. When changing adjacent outer circles, the tractor drives one more guidance line width at the corner of the current work completion circle and then drives onto the next outer circle until all outer circles are completed; At each outer corner, turn by: After the tractor completes the operation on one side of the outer circle, turn off the agricultural implement, reverse to the starting point of the turning path, control the steering wheel to turn to the next working row with a safe minimum turning radius, and reverse along the direction of the working row to the starting working position of the working row.

2. The path planning and precision operation method for unmanned tractor operation according to claim 1, characterized in that: The inner circle parallel line segments are parallel to the longest side of the field boundary, both ends of the parallel line segments extend to the short side of the outermost sweeping circle, and the distance between the parallel line segments closest to the long side of the innermost sweeping circle and the long side of the innermost sweeping circle is equal to the path operation width d.

3. The path planning and precision operation method for unmanned tractor operation according to claim 1, characterized in that: In step 2 of the inner circle operation step, after the tractor enters the field boundary, it first runs along the short side outer circle. When the tractor travels from the outer circle to the initial path, the vehicle speed is reduced; when the tractor moves forward to the starting point of the turning path calculated according to the turning radius, the vehicle stops, controls the steering wheel to turn, and after the wheel steering angle reaches the set value, the vehicle moves forward and turns to the initial path.

4. The path planning and precision operation method for unmanned tractor operation according to claim 1, characterized in that: In step 2 of the inner circle operation step, after the unmanned tractor drives to the initial path along the turning path calculated according to the turning radius, the vehicle stops, and the steering wheel is turned to a specified position based on the vehicle's reverse route. After the wheels are turned to the required angle, reverse is started, and reverse is started along the initial path, so that the agricultural machinery operation position reaches the operation start point.

5. The path planning and precision operation method for unmanned tractor operation according to claim 1, characterized in that: Both ends of the working path are extended by a certain distance l, where l = width of agricultural machinery * coefficient.

6. The path planning and precision operation method for unmanned tractor operation according to claim 1, characterized in that: When the outer circle turns at a corner, the distance between the starting point of the turning path and the corner point is Where α is the angle between the current operation path and the next operation path, R l is the minimum turning radius of the vehicle.

7. The path planning and precision operation method for unmanned tractor operation according to claim 1, characterized in that: When the tractor travels from the inner circle to the outer circle, it adopts the straddle method to turn into the outer circle.

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