AU2021203787B2

AU2021203787B2 - Wheeled agricultural robot with self-adaptive wheel track adjusting function and adjusting method thereof

Info

Publication number: AU2021203787B2
Application number: AU2021203787A
Authority: AU
Inventors: Chen Chen; Longfei CUI; Suming DING; Wei Gu; Yongkui JIN; Feixiang LE; Tao Sun; Zhu SUN; Yang Xu; Xinyu XUE; Ling Zhang; Songchao ZHANG; Lixin Zhou
Original assignee: Nanjing Research Institute for Agricultural Mechanization Ministry of Agriculture
Current assignee: Nanjing Research Institute for Agricultural Mechanization Ministry of Agriculture
Priority date: 2020-05-27
Filing date: 2021-04-07
Publication date: 2022-09-08
Anticipated expiration: 2041-04-07
Also published as: CN111645777A; WO2021238421A1; CN111645777B; AU2021203787A1; JP7377379B2; JP2023522430A

Abstract

The present invention discloses a wheeled agricultural robot with a self adaptive wheel track adjusting function and an adjusting method thereof. The wheeled agricultural robot comprises a control system, a vehicle body provided with four driving wheel legs, and a wheel track adjusting actuator. The wheeled agricultural robot of the present invention can adjust the wheel track adaptively according to the changes in the crop row spacing and the terrain to greatly reduce seedling pressing, thereby broadening the applicable terrain range for the agricultural robot to carry out operations, improving working efficiency, and reducing operation costs. Moreover, the present invention has various wheel track adjustment modes such as synchronous adjustment, independent two-wheel adjustment, and independent four-wheel adjustment, which can ensure the smooth pass of chassis when encountering obstacles, narrow road sections and other complex terrains; the present invention also has a reasonable structure, is easy to operate and maintain, and is suitable for popularization and use.

Description

WHEELED AGRICULTURAL ROBOT WITH SELF-ADAPTIVE WHEEL TRACK ADJUSTING FUNCTION AND ADJUSTING METHOD THEREOF

TECHNICAL FIELD The present invention belongs to the technical field of agricultural machinery, and particularly relates to a wheeled agricultural robot with a self-adaptive wheel track adjusting function and an adjusting method thereof.

BACKGROUND With the increasing contradiction between the increasing population and the shortage of water and soil resources for agricultural production and labor, the improvement of agricultural production efficiency is urgently needed. It is an inevitable trend for the development of agricultural mechanization to replace humans completely or partially with the agricultural robot to complete complex tasks efficiently, safely and reliably. For example, in China, the pest and weed control of crops has been such a part of the agricultural production that is characterized by the largest labor consumption, the highest labor intensity and the highest frequency. However, the spaying of pesticides such as insecticides and herbicides and liquid fertilizers can not only cause waste, but also seriously contaminate the environment. Therefore, the intelligent field management robot has become a research hot spot in the industry, and fine field management operations such as pesticide application, fertilizer application, weeding, and crop information acquisition can be performed by means of the robot. In the aspect of pesticide/fertilizer application, the intelligent field management robot detects weeds by computer vision technique using the concept of accurate spraying, and then sprays the herbicides in a targeted manner, so that the amount of herbicides used in the crop growth can be significantly reduced. However, in China, the arable lands are hilly and mountainous, and the planting line spacing for crops sown or transplanted by the planting machine will be inconsistent due to the precision of the machine, uneven ground and the like. Manned boom sprayers and cultivators as well as autonomously-driving agricultural robots all cause seedling pressing by wheels. In most cases, the driver drives the machine along crop row, and the autonomous navigation robot adjusts the course of the chassis in real time according to crop row, but these field management machines do not have a self-adaptive wheel track adjusting function, which causes that ground obstacles such as bumps and pits can still jolt the chassis, or the small agricultural robot cannot pass through the ground obstacles.

SUMMARY The technical purpose of the present invention is to provide a wheeled agricultural robot with a self-adaptive wheel track adjusting function and an adjusting method thereof, which ensures that the wheel track of the robot can be adjusted adaptively with the crop row spacing to greatly reduce the seedling pressing in the operation process, and ensures the smooth pass of chassis when encountering obstacles and narrow road sections. For the above technical purpose, the present invention provides the following technical scheme. A wheeled agricultural robot with a self-adaptive wheel track adjusting function comprises a control system, a vehicle body provided with four driving wheel legs, and a wheel track adjusting actuator; wherein the four driving wheel legs of the vehicle body are each connected with a chassis frame through corresponding rocker arms, each of the driving wheel legs comprises a wheel and a steering device, each wheel is driven by an independent hub motor, and a driving circuit of the hub motor is connected with the control system; the steering device comprises a steering motor controlling the steering of the wheel and a motor mounting base connected with the wheel below through a wheel leg support; the outer end of the rocker arm is fixedly connected with the motor mounting base, and the inner end thereof is connected with the chassis frame through a revolute pair comprising a rocker arm rotating shaft, so that the rocker arm can swing transversely relative to the longitudinal axis of the vehicle body with the rocker arm rotating shaft as a center, changing the distance between a corresponding wheel and the longitudinal axis of the vehicle body; the wheel track adjusting actuator comprises a driving device, a first electromagnetic clutch, a second electromagnetic clutch, and a front linear sliding rail device and a rear linear sliding rail device, the two linear sliding rail devices are paved on the chassis frame along the longitudinal axis of the vehicle body, a sliding block of each linear sliding rail device is driven by the driving device through a transmission mechanism, power is transmitted to the sliding block of the front linear sliding rail device by the driving device through the first electromagnetic clutch and transmitted to the sliding block of the rear linear sliding rail device by the driving device through the second electromagnetic clutch, control signal input ends of the driving device and the two electromagnetic clutches are each connected with the control system with start/stop and connection/disconnection controlled by the control system; the left and right driving wheel legs in the front of the vehicle body are each connected with the sliding block on the front linear sliding rail device through a connecting rod structure, and the left and right driving wheel legs in the rear of the vehicle body are each connected with the sliding block on the rear linear sliding rail device through a connecting rod structure; the connecting rod structure consists of a driving connecting rod and a rocker arm extending rod, one end of the driving connecting rod is connected with one end of the rocker arm extending rod through a revolute pair and a self-locking connector, the other end of the rocker arm extension rod is fixedly connected with the rocker arm to drive the rocker arm to rotate, the other end of the driving connecting rod is hinged with a corresponding sliding block through the revolute pair to convert the linear movement of the sliding block into the rotary movement driving the rocker arm extending rod to rotate with the rocker arm rotating shaft as a center; the self-locking connector consists of a first connecting block, a second connecting block and a positioning pin electromagnet; one of the connecting blocks is provided with a locking electromagnet, and after the locking electromagnet is energized, the two connecting blocks are fixedly connected by magnetic adsorption and the self-locking connector is in a connected state; the first connecting block is fixedly mounted at the end of the rocker arm extending rod, and the second connecting block is connected with the driving connecting rod through a revolute pair; the second connecting block is provided with a limiting hole, and a positioning pin electromagnet is mounted on the driving connecting rod; when the locking electromagnet is de-energized, the first and second connecting blocks are out of the limitation of the magnetic adsorption, then the self-locking connector is disconnected, and the positioning pin electromagnet is controlled to act simultaneously by the control system to allow the extending pin rod of the positioning pin electromagnet to be inserted into the limiting hole of the second connecting block, so that the second connecting block is prevented from freely rotating; the wheeled agricultural robot comprises the following four wheel track adjustment modes: A) synchronous four-wheel track adjustment mode: the first and second electromagnetic clutches and all the self-locking connectors are in a connected state, and the wheel tracks of the front wheels and the rear wheels are adjusted synchronously by the driving device through the two linear sliding rail devices; B) independent front-wheel track adjustment mode: the first electromagnetic clutch and all the self-locking connectors are in a connected state, the second electromagnetic clutch is disconnected, and the wheel track of the front wheels is adjusted by the driving device through the front linear sliding rail device; C) independent rear-wheel track adjustment mode: the second electromagnetic clutch and all the self-locking connectors are in a connected state, the first electromagnetic clutch is disconnected, and the wheel track of the rear wheels is adjusted by the driving device through the rear linear sliding rail device; D) independent four-wheel position adjustment mode: the first and second electromagnetic clutches and all the self-locking connectors are in a disconnected state, and the distances between the four wheels and the longitudinal axis of the vehicle body can be independently adjusted; wherein, A), B) and C) are active adjustment modes, which mean that the rocker arm is driven to swing transversely by controlling the driving device; D) is a passive adjustment mode, which mean that a corresponding wheel is driven to move forward or backward by independently controlling the hub motor to rotate, so that the rocker arm is driven to swing transversely, changing the distance between the wheel and the longitudinal axis of the vehicle body. On the basis of the above scheme, the further improved or preferred scheme also comprises the following. Further, the second connecting block is a convex block with a convex structure mounted on a surface abutting the first connecting block, the first connecting block is a concave block with a concave structure adapted to the convex structure mounted on the abutting surface thereof; a pressure sensor and a stroke switch are arranged in the concave structure, the signal output ends of the pressure sensor and the stroke switch are connected with the control system; when the first and second connecting blocks are connected by the magnetic adsorption, the convex structure is embedded in the concave structure and can be contacted with the pressure sensor and the stroke switch; if the signal fed back by the pressure sensor is not less than a preset threshold value, the fixation of the connecting rod structure is determined as firm by the control system, and a proper active adjustment mode is selected from the modes A)-C) to start a corresponding sliding block. Further, the first connecting block is provided with two inserting plates positioned on the left side and the right side of the concave structure and protruding out of the abutting surface of the first connecting block, and the second connecting block is provided with adaptable inserting grooves at the corresponding positions; when the first connecting block and the second connecting block are connected by the magnetic adsorption, the inserting plates of the first connecting block are jammed in the inserting grooves of the second connecting block, and the inner sides of the two inserting plates are provided with chamfer slopes facing the convex structure. Preferably, the driving device is a servo motor, the linear sliding rail device is a lead screw electric sliding rail device, and the servo motor is mounted to the middle of the chassis frame and positioned between the two lead screw electric sliding rail devices; the two electromagnetic clutches are mounted at the power input ends of the two lead screw electric sliding rail devices near the center of the chassis, and the output shafts of the servo motor are connected with the input shafts of the two electromagnetic clutches through the transmission mechanism, that is, the power is transmitted to the front and rear lead screw electric sliding rail devices through the two electromagnetic clutches. Further, the side of the linear sliding rail device is provided with a grating ruler to measure the stroke of the sliding block on the rail, and connected with the control system, so that the wheel track is accurately controlled by the control system through the control of the stroke of the sliding block. Further, the wheeled agricultural robot is provided with a navigation system, and the wheel track adjusting actuator is controlled to act by the control system according to a signal fed back by the navigation system; the navigation system comprises a terrain detection sensor, a satellite positioning receiver and an inertial sensor, and according to the terrain information detected by the terrain detection sensor, the vehicle body position information received by the satellite positioning receiver and the vehicle body attitude information fed back by the inertial sensor, the crop row position and the crop row spacing in front of the vehicle body is analyzed by the control system, and an adaptable wheel track adjustment amount is calculated to output a corresponding control signal to the wheel track adjusting actuator. A manual wheel track adjusting method based on the wheeled agricultural robot applied in a passive adjustment mode D) and performed in a non-driving state of the vehicle body, comprises the following steps:

1) the wheel track adjustment amount of each driving wheel leg is planned in advance by an operator according to the terrain or the crop row spacing in front of the vehicle body, and an adjusting instruction is sent to the control system of the robot through a remote control terminal based on the wheel track adjustment amount; 2) after receiving the adjusting instruction, firstly, all the self-locking connectors are controlled to be disconnected by the control system; secondly, the driving device of the wheel track adjusting actuator is controlled to start to push the sliding block on each linear sliding rail device to the initial position; then the first and second electromagnetic clutches are controlled to be disconnected simultaneously; finally, corresponding control instructions are output to the hub motor and the steering motor to drive the wheel to move forward or backward around the rocker arm rotating shaft, so that the vertical distance between the wheel and the longitudinal axis of the vehicle body is changed; after the wheel is adjusted in place, the hub motor is controlled to stop rotating, and an electric band-type brake at the rocker arm rotating shaft is controlled to act immediately to fix the wheel track. An automatic wheel track adjusting method based on the wheeled agricultural robot applied in the active adjustment modes A), B) orC), comprises the following steps: 1) a three-dimensional laser radar is mounted in the front of the vehicle body as the terrain detection sensor, in the running process of the agricultural robot, the ground and crops in front of the vehicle body are scanned using the three-dimensional laser radar, a field scene three-dimensional point cloud map based on the vehicle body is established using the vehicle body position data sent by the satellite positioning system and the chassis frame attitude data fed back by the inertial sensor, and the field scene three-dimensional point cloud map is converted into a point cloud map based on a geodetic coordinate system OXYZ, wherein a vertical Z coordinate represents the height from the ground of a three-dimensional point, an X direction represents the longitudinal direction of a horizontal plane, namely the running direction of the robot, and a Y direction represents the transverse direction of the horizontal plane perpendicular to the X direction; 2) a reasonable height threshold value of the crops is preset according to the type of crops and the growth stage of the crops, and points with a height coordinate greater than the height threshold value in the field scene three-dimensional point cloud map are determined as points of crop row clusters, so that the point clouds of the crop row clusters are separated from the three-dimensional point cloud map, then a middle point of each of the crop row clusters is calculated, and the longitudinal connecting line of the middle points is a central line of the crop row; 3) after obtaining the central line of the crop row, the crop row spacing in front of the vehicle body is calculated in real time according to the current position of the vehicle body of the robot, and the theoretical width of the front wheels and the rear wheels, namely the target width of wheel track adjustment, is calculated based on the position between the lines where the left and right wheels of the vehicle body are positioned or the number of lines spanned; 4) the actual width of the wheel track is obtained, the difference value between the actual width of the wheel track and the target width of the wheel track adjustment is calculated, a corresponding control instruction is output to a linear sliding rail device by the control system based on a control strategy with a change dependency of the wheel track and the crop row, the rocker arm is driven to rotate by a certain yaw angle through the movement of the sliding block, and the distance between the front/rear wheels and the longitudinal axis of the vehicle body is adjusted to adapt to the crop row spacing in front of the vehicle body. Further, in the step 1), a Hessian plane equation is fitted by the RANSAC algorithm based on the field scene three-dimensional point cloud map, and the detected ground is refined and reconstructed by the least square fitting. Beneficial effects: The wheeled agricultural robot of the present invention can adjust the wheel track adaptively according to the changes in the crop row spacing and the terrain to greatly reduce seedling pressing, thereby broadening the applicable terrain range for the agricultural robot to carry out operations, improving working efficiency, and reducing operation costs. Moreover, the present invention has various wheel track adjustment modes such as synchronous adjustment, independent two-wheel adjustment, and independent four-wheel adjustment, which can ensure the smooth pass of the chassis when encountering obstacles, narrow road sections and other complex terrains, and the present invention also has a reasonable structure, is easy to operate and maintain, and is suitable for popularization and use.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the overall structure of a specific embodiment of an agricultural robot according to the present invention; FIG. 2 is a schematic structural diagram of driving wheel legs of the agricultural robot of FIG. 1; FIG. 3 is a schematic diagram of crop rows; FIG. 4 is a schematic structural diagram of a wheel track adjusting actuator; FIG. 5 is a topological structure diagram of the agricultural robot in the embodiment of FIG. 1 for realizing automatic wheel track adjustment; FIG. 6 is a control schematic diagram of self-adaptive wheel track adjustment; FIG. 7 is a schematic structural diagram of a connecting rod structure; FIG. 8 is a schematic diagram I of a self-locking connector; FIG. 9 is a schematic diagram II of the self-locking connector; FIG. 10 is a schematic structural diagram of a convex block; FIG. 11 is a schematic structural diagram of a concave block; FIG. 12 is a mounting schematic diagram of a pressure sensor and a stroke switch; FIG. 13 is a five-view of a convex block; FIG. 14 is a schematic structural diagram I of a wheel track adjusting actuator and driving wheel legs; FIG. 15 is a schematic structural diagram II of the wheel track adjusting actuator and driving wheel legs;

FIG. 16 is a schematic diagram of the local structure of the wheel track adjusting actuator and driving wheel legs; FIG. 17 is a structural schematic diagram of the wheel track adjusting actuator, chassis frame and driving wheel legs; and FIG. 18 is a control schematic diagram of the wheel track of a chassis.

DETAILED DESCRIPTION In order to explain the technical solutions of the present invention, the present invention are further described in detail below with reference to drawings and specific embodiments. A wheeled agricultural robot with a self-adaptive wheel track adjusting function as shown in FIG. 1 comprises a vehicle body 3, a control system, a navigation system, a wheel track adjusting actuator and a pesticide application system. The vehicle body 3 is provided with four driving wheel legs in front, back, left and right sides, a wheel 10 of each of the driving wheel legs is driven by an independent hub motor 14 to realize the four-wheel differential, and each wheel 10 is provided with an independent steering device 8. The navigation system, the wheel track adjusting actuator, the pesticide application system, the hub motor 10 and the steering device 8 are each connected with the control system with the start/stop controlled by the control system. The pesticide application system comprises a pesticide box 4, a spray boom 1 and an infusion line, the pesticide box 4 is mounted on the vehicle body 3, and the spray boom 1 is hooked to the rear of the vehicle body 3 through a self-balancing spray boom suspension 2. The navigation system comprises a terrain detection sensor 6, a satellite positioning receiver 4, an inertial sensor, a wheel odometer and other components. The terrain detection sensor 6 is mounted in the front of the vehicle body to detect the terrain information including the ground and crops, and a three-dimensional laser radar (a three-dimensional scanning laser sensor) is preferably adopted; the satellite positioning receiver 4 is connected with a satellite positioning system to provide running position information of the vehicle body 3 in real time; the inertial sensor is mounted on the vehicle body to detect the attitude of the vehicle body or the chassis frame of the vehicle body, including pitch angle, roll angle and other data; the wheel odometer can be a rotary encoder to measure the rotation angle and the rotation speed of the wheels, and further calculating the running distance of each wheel. A farmland scene is required to be sensed by the robot when running in the field to generate a course reference track, the target rotation speeds of the four hub motors are calculated from the course reference track, the rotation speeds of the four hub motors are controlled by the control system in real time to track the target rotation speeds, and the rotation speeds of the wheels are measured by the wheel odometer as the feedback input to the control system, then a real-time closed-loop control is performed. According to the data fed back by the navigation system, the crop row position and the crop row spacing in front of the vehicle body 3 is analyzed by the control system, and the adaptable wheel track adjustment amount is calculated to output a corresponding control signal to the wheel track adjusting actuator. The four driving wheel legs of the vehicle body 3 are each connected with the chassis frame through a rocker arm 7. Each of the driving wheel legs comprises a wheel 10 and a steering device 8 for individually controlling the wheel 10. The steering device 8 consists of a steering motor and a motor mounting base. The motor mounting base is arranged above a wheel leg support 9, the upper part of the wheel leg support 9 is connected with the motor mounting base through a vertically arranged support rotating shaft, and the steering motor is started to drive the wheel leg support 9 and the wheels 10 to steer. The outer end of the rocker arm 7 is fixedly connected with the motor mounting base, and the inner end thereof is connected with the chassis frame through a first revolute pair. The rotating shaft of the first revolute pair is a rocker arm rotating shaft 12 vertically arranged on the chassis frame and fixedly connected with a rocker arm 7. The rocker arm 7 can drive the driving wheel legs to swing transversely when rotating round the central line of the first revolute pair, thereby changing the distance between the wheel 10 and the longitudinal axis (longitudinal center line) of the vehicle body. Meanwhile, an angle sensor 11 for detecting the rotation angle of the rocker arm rotating shaft 12 is mounted on the rocker arm rotating shaft 12 or the chassis frame, the angle sensor 11 is connected with the control system to feed back the yaw angle of the rocker arm, and the rotary encoder is preferably adopted. The wheel track adjusting actuator comprises a first electromagnetic clutch 17-1, a second electromagnetic clutch 17-2, a driving device 18, a gear reduction box, and a front linear sliding rail device and a rear linear sliding rail device. The two linear sliding rail devices are paved on the chassis frame along the longitudinal axis of the vehicle body. In this embodiment, the driving device 18 is a servo motor, and the linear sliding rail device is a lead screw electric sliding rail device. The lead screw electric sliding rail device is composed of a lead screw 15-1, guide rails 15-2, sliding blocks 15-3 and other components, the two guide rails 15-2 are arranged on the left side and the right side of the screw rod 15-1, and are parallel to the lead screw; the sliding blocks 15-3 are arranged on the two guide rails 15-2 and connected with lead screw nuts, and when the lead screw is driven by the servo motor to rotate, the lead screw nuts drive the sliding blocks 15-3 to make a linear reciprocating movement along the guide rails. The control signal input end of the servo motor is connected with the control system with the start/stop controlled by the control system. As shown in FIG. 4, the servo motor is mounted in the middle of the chassis frame and positioned between the two lead screw electric sliding rail devices. The two electromagnetic clutches 17-1 and 17-2 are mounted at the power input ends of the two lead screw electric sliding rail devices near the center of the chassis. The gear reduction box is provided with a power input end (driving bevel gear) and two power output ends (driven bevel gears), an output shaft of the servo motor is connected with the power input end of the gear reduction box, the two power output ends of the gear reduction box are connected with the power input ends of the two electromagnetic clutches, and the power output ends of the two electromagnetic clutches are connected with the corresponding lead screw shafts. Considering that the output shaft of the servo motor is perpendicular to the lead screw, bevel gears are adopted by the gear reduction box to transmit power. The control signal input ends of the two electromagnetic clutches are connected with the control system with the connection/disconnection controlled by the control system. When the first/second electromagnetic clutch is disconnected, the power of the servo motor is only transmitted to the rear/front lead screw, and an independent two-wheel adjustment is performed for the rear/front driving wheel leg; when the two electromagnetic clutches are both connected, a synchronous four-wheel adjustment is performed. The sides of the front and rear lead screw electric sliding rail devices are provided with grating rulers to measure the stroke of their respective sliding blocks on the rail, and connected with the control system to control the current wheel track of the chassis of the vehicle body. The left and right driving wheel legs in the front of the vehicle body 3 are each connected with the sliding block on the front lead screw electric sliding rail device through a connecting rod structure, and the left and right driving wheel legs in the rear of the vehicle body are each connected with the sliding block on the rear lead screw electric sliding rail device through a connecting rod structure. As shown in FIGs. 4, 14 and 17, the connecting rod structure consists of a rocker arm extending rod 13-2 and a driving connecting rod 13-1, one end of the rocker arm extending rod is connected with one end of the driving connecting rod through a self-locking connector and a second revolute pair, the other end of the rocker arm extending rod 13-2 is fixedly connected with the rocker arm 7 to drive the rocker arm 7 to rotate with the rocker arm rotating shaft 12 as a center, and the other end of the driving connecting rod 13-1 is hinged with the corresponding sliding block through a third revolute pair to convert the linear movement of the sliding block into the rotary movement driving the rocker arm extending rod 13-2 to rotate with the rocker arm rotating shaft 12 as a center. As shown in FIGs. 7 to 13, the self-locking connector comprises a first connecting block 13-3, a second connecting block 13-5, a positioning pin electromagnet 13-4, and other components. The second connecting block 13-5 is provided with a locking electromagnet 13-5-3, and the two connecting blocks are connected by magnetic adsorption after the locking electromagnet 13-5-3 is energized. The first connecting block 13-3 is fixedly mounted at the end of the rocker arm extending rod 13-2, and the second connecting block 13-5 is hinged with the driving connecting rod 13-1 through the second revolute pair; the second connecting block 13-5 is provided with a kidney-shaped limiting hole 13-5-2, the positioning pin electromagnet 13-4 is mounted at the end of the driving connecting rod 13-1, the end of the driving connecting rod 13-1 is provided with a circle of uniformly distributed pin holes. When the locking electromagnet 13-5-3 is de-energized, the positioning pin electromagnet 13-4 is controlled to act by the control system to allow the extending pin rod of the positioning pin electromagnet to pass through the pin holes of the driving connecting rod 13-1 and to be inserted into the limiting hole 13-5-2 of the second connecting block 13-5, so that the second connecting block 13-5 can be prevented from freely rotating. After the locking electromagnet 13-5-3 is de-energized, the self-locking connector is disconnected, the driving connecting rod 13-1 and the rocker arm extending rod 13-2 are disconnected, so that the wheel tracks of the four wheels from the longitudinal axis of the vehicle body can be independently adjusted. The second connecting block 13-5 is a convex block with a convex structure mounted on a surface abutting the first connecting block, as shown in FIG. 10, the convex structure consists of an upper semi-cylinder and a lower semi-cone, and a rotating shaft 13-5-1 of the second revolute pair is mounted on the second connecting block 13-5. The first connecting block 13-3 is a concave block with a concave structure adapted to the convex structure mounted on the abutting surface thereof, as shown in FIG. 11, the first connecting block 13-3 is further provided with two inserting plates 13-3-2 positioned on the left side and the right side of the concave structure and protruding out of the abutting surface of the first connecting block 13-3, and the second connecting block 13-5 is provided with two adaptable inserting grooves at the corresponding positions. When the first connecting block 13-3 and the second connecting block 13-5 are connected by magnetic adsorption, the convex structure is embedded in the concave structure, and the inserting plates 13-3-2 are inserted into the inserting grooves. Based on the concave structure, the convex structure, the inserting plates and inserting grooves, the two connecting blocks in the adsorption state will not be easily staggered in the direction perpendicular to the magnetic force. The inner corners of the two inserting plates 13-3-2 are arranged as chamfers, and the two connecting blocks can be quickly and accurately positioned in the abutting process using the chamfer slopes 13-3-3 facing the convex structure. Meanwhile, a pressure sensor 19 for determining the connection firmness of the first connecting block and the second connecting block and a stroke switch 20 for determining the in-place connection of the first connecting block and the second connecting block are arranged in the concave structure. The signal output ends of the pressure sensor 19 and the stroke switch 20 are connected with the control system. When the first and second connecting blocks are connected by the magnetic adsorption, the convex structure is embedded in the concave structure and can be contacted with the pressure sensor 19 and the stroke switch 20. After signals sent by the stroke switch 20 and the pressure sensor 19 are received by the control system, the electromagnetic clutches are controlled to be connected. If the data fed back by the pressure sensor 19 is greater than a preset threshold value, the fixation of the connecting rod structure is determined as firm by the control system, and the servo motor is started to drive the sliding block. The wheeled agricultural robot in this embodiment comprises the following four wheel track adjustment modes: A) synchronous four-wheel track adjustment mode: the first and second electromagnetic clutches and all the self-locking connectors are in a connected state, and the wheel tracks of the front wheels and the rear wheels are adjusted synchronously by the driving device (18) through the two linear sliding rail devices; B) independent front-wheel track adjustment mode: the first electromagnetic clutch and all the self-locking connectors are in a connected state, the second electromagnetic clutch is disconnected, and the wheel track of the front wheels is adjusted by the driving device (18) through the front linear sliding rail device; C) independent rear-wheel track adjustment mode: the second electromagnetic clutch and all the self-locking connectors are in a connected state, the first electromagnetic clutch is disconnected, and the wheel track of the rear wheels is adjusted by the driving device (18) through the rear linear sliding rail device; D) independent four-wheel position adjustment mode: the first and second electromagnetic clutches and all the self-locking connectors are in a disconnected state, and the distances between the four wheels and the longitudinal axis of the vehicle body are independently adjusted; wherein, A), B) and C) are active adjustment modes, D) is a passive adjustment mode, and the four modes A), B), C) and D) can be closed-loop automatic control or open-loop manual control. Preferably, the agricultural robot in this embodiment can start the active adjustment mode in the automatic control in the running process, and the automatic wheel track adjusting method thereof comprises the following steps: 1) in the running process of the robot in the field, the ground and crops in the front of the vehicle body are scanned using a three-dimensional laser radar, and a field scene three-dimensional point cloud map based on a geodetic coordinate system OXYZ is established using the vehicle body position data sent by the satellite positioning system and the chassis frame attitude data fed back by the inertial sensor, then a Hessian plane equation is fitted by a RANSAC algorithm, and the detected ground is refined and reconstructed by the least square fitting; in the geodetic coordinate system, a vertical Z coordinate represents the height from the ground of a three-dimensional point, an X direction represents the longitudinal direction of a horizontal plane, namely the running direction of the robot, and a Y direction represents the transverse direction of the horizontal plane perpendicular to the X direction; 2) a reasonable height threshold value of the crops is preset in the control system according to the type of crops and the growth stage of the crops, and points with a height coordinate (z coordinate) greater than the height threshold value in the field scene three-dimensional point cloud map are determined as points of crop row clusters, so that the point clouds of the crop row clusters are separated from the point cloud map, then a middle point of each of the crop row clusters is calculated, and the longitudinal connecting line of the middle points is considered as a central line of the crop row; 3) after obtaining the central line of the crop row, the crop row spacing in front of the vehicle body is calculated in real time according to the current running position of the vehicle body of the robot, and the theoretical width of the front wheels and the rear wheels, namely the target width of wheel track adjustment, is calculated based on the position between the lines where the left and right wheels of the vehicle body are positioned or the number of lines spanned; 4) the actual width of the wheel track is obtained, the difference value between the actual width of the wheel track and the target width of the wheel track adjustment is calculated, a corresponding control instruction is output to a linear sliding rail device by the control system based on a control strategy (an optimal control method or a proportional-integral-derivative control method (PID)) with a change dependency of the wheel track and the crop row, the rocker arm is driven to rotate by a certain yaw angle through the movement of the sliding block, and the distance between the wheels and the longitudinal axis of the vehicle body is adjusted to adapt to the crop row spacing in front of the vehicle body. After the yaw angle of the rocker arm is adjusted in place, the electric band-type brake 21 at a rocker arm rotating shaft is controlled to act to prevent the rocker arm rotating shaft from rotating relative to the chassis frame, so as to fix the wheel track.

Before implementing the automatic wheel track adjusting method, a wheel track adjustment threshold value should be set, and in the adjustment process, if the target track width requested to be adjusted exceeds the threshold value, the robot stops running for safety, and the wheel track is adjusted after the robot stops moving forward. In this way, the connection stress between the rocker arm and the vehicle body of the robot can be minimized. For the passive adjustment mode D), the agricultural robot in this embodiment preferably adopts an open-loop manual wheel track adjusting method, which specifically comprises the following steps: 1) the wheel track adjustment amount of a driving wheel leg to be adjusted is planned in advance by an operator according to the terrain or the crop row spacing in front of the vehicle body, and an adjusting instruction is sent to the control system of the robot through a remote control terminal based on the wheel track adjustment amount; the remote control terminal is provided with a user interface for the operator to select an adjustment mode and input the adjusting instruction for the wheel track; 2) after sending the adjusting instruction, firstly, for a driving wheel leg to be adjusted, a locking electromagnet of a locking connector corresponding to a control system is de-energizing by the control system, so that a first connecting block 13-3 and a second connecting block 13-5 of the locking electromagnet are out of the limitation of the magnetic adsorption, a driving connecting rod 13-1 and a rocker arm extending rod 13-2 are disconnected, and the action of a positioning pin electromagnet 13-4 is controlled when a locking electromagnet 13-5-3 is de energized, to allow the pin rod extending out of the positioning pin electromagnet to be inserted into a limiting hole of the second connecting block, so that the freedom degree of the movement of the second connecting block is limited, and the failure of the in-time and accurate abutting of the two connecting blocks when the wheel track is adjusted using a sliding block is avoided; secondly, the servo motor is controlled to rotate by the control system to push the sliding block of each lead screw electric sliding rail device to the initial position, so that the driving connecting rod of the lead screw rod electric sliding rail device are reset to be parallel to the lead screw, and the contact with other components is avoided; then the simultaneous disconnection of the first electromagnetic clutch and the second electromagnetic clutch is controlled by the control system, so that the two do not involve in the wheel track adjustment; finally, corresponding control instructions are output to a hub motor 14 and a steering motor 8 by the control system to drive the wheel 10 to move around the rocker arm rotating shaft 12, and the wheel 10 can move forward and backward to drive the rocker arm to swing and rotate; the rotation angle of the rocker arm can be observed by the operator through a control terminal instrument, or the vertical distance between the wheel center and the longitudinal axis of the vehicle body can be acquired by the operator through other sensing equipment, and the changes in the distance parameters of the 4 wheels are displayed on the user interface in real time; after the yaw angle of the rocker arm is adjusted in place, the hub motor 14 is controlled to stop rotating, the action of the rocker arm is locked by the electric band type brake immediately, so that the rocker arm rotating shaft is fixed at a specific angle, and the wheel track of the wheel 10 is adjusted independently (after the vehicle body is started, the steering motor 8 is used for controlling the in-situ steering of the wheel according to the next driving direction). The passive adjustment mode D) is suitable for complex road conditions, and allows the robot to pass through ditches and obstacles in the field or long and narrow passages smoothly. In the process of implementing the passive adjustment mode, before controlling the wheels to rotate, users control the control system, and the independent adjustment of the four driving wheel legs in combination with the connection/disconnection control of the corresponding electromagnetic clutches and the locking electromagnets can be performed using a servo motor and a lead screw electric sliding rail device, preferably adopting the above manual wheel track adjusting method, and preferably in a state where the vehicle body stops running. In each adjustment mode, the control principle of the wheel track of the chassis is as follows. As shown in FIG. 18, an absolute value encoder is mounted at each of the 4 rocker arm rotating shafts for the wheel track adjustment to measure the rotation angles al, a2, 3 and a4 of the rocker arms relative to the longitudinal axis of the vehicle body. As shown in FIG. 18, the center distance between the left and right arm rotating shafts is W1; the center distance between the front and rear rocker arm rotating shafts is Ll; the length of the wheel track adjusting rocker arm is D (the horizontal distance between a rocker arm main shaft and a rotating shaft at the upper part of a wheel leg support); then according to the angle measured by the rotary encoder in real time, the corresponding wheel track W2 of the front wheels and the corresponding wheel track W3 of the rear wheels can be obtained by the following formulas: W2 = W1 + D-sin(a 1) + D-sin(a2) W3 = W1 + D-sin(a3) + D-sin(a4) The corresponding wheel base L2 of the front wheels and the corresponding wheel base L3 of the front wheels are obtained by the following formulas: L2=L1 +D-cos(al)+D-cos(a2) L3 =L1 + D-cos(a3)+ D-cos(a4) In the synchronous four-wheel adjustment mode, the rotation angles of the rocker arms relative to the longitudinal axis of the vehicle body are equal, namely a = c2= a3= c4, and W2= W3.

In the independent front-wheel track adjustment mode or the independent rear wheel track adjustment mode, the rotation angles of the two front wheel rocker arms relative to the longitudinal axis of the vehicle body are equal, and the rotation angles of the two rear wheel rocker arms relative to the longitudinal axis of the vehicle body are equal, namely a = a2 and 3 = a4. In a special case, in the independent four-wheel position adjustment mode, the rotation angles of the rocker arms relative to the longitudinal axis of the vehicle body are different. Taking an active adjustment mode as an example, point cloud data of the crops, the ground and the like in front of the vehicle is measured by the agricultural robot through the three-dimensional laser radar, the point clouds are converted to the geodetic coordinate system through the inertial attitude sensor and the satellite positioning system, the self-adaptive wheel track adjustment is performed according to the running position coordinates of the chassis of the robot, and a spacing Wd of the left and right wheels of the chassis closest to the spacing of two crop rows is measured by the control system according to the point cloud data, and then a difference value between W2 and Wd and a difference value between W3 and Wd are used as the input of the control system. The output of the control system is a rotation speed control instruction of the servo motor and the on-off command of the two electromagnetic clutches. After the wheel track is adjusted in place, the electric band type brake 21 on the rocker arm rotating shaft is locked. The control system of the agricultural robot is provided with a plurality of special control units such as a motor controller, a navigation control unit, and an operation machine control unit, and except that the motor controller is connected through a CAN bus, different sensors and function control units are each connected through Ethernet and communicated using TCP/IP. The general principles, principal features, and advantages of the present invention are revealed and described in the above embodiment. It should be understood by those skilled in the art that the present invention is not limited to the above embodiment, which are merely illustrative of the principles of the invention. Various changes and modifications may be made without departing from the spirit and scope of the present invention, and the protection scope of the present invention is defined by the appended claims, the description and the equivalents thereof.

Claims

CLAIMS:

1. A wheeled agricultural robot with a self-adaptive wheel track adjusting function, comprising a control system, a vehicle body (3) provided with four driving wheel legs, and a wheel track adjusting actuator; wherein the four driving wheel legs of the vehicle body (3) are each connected with a chassis frame through corresponding rocker arms (7), each of the driving wheel legs comprises a wheel (10) and a steering device (8), each wheel (10) is driven by an independent hub motor (14), and a driving circuit of the hub motor (14) is connected with the control system; the steering device (8) comprises a steering motor controlling the steering of the wheel (10) and a motor mounting base connected with the wheel (10) below through a wheel leg support (9); the outer end of the rocker arm (7) is fixedly connected with the motor mounting base, and the inner end thereof is connected with the chassis frame through a revolute pair comprising a rocker arm rotating shaft (12), so that the rocker arm (7) can swing transversely relative to the longitudinal axis of the vehicle body with the rocker arm rotating shaft (12) as a center, changing the distance between a corresponding wheel and the longitudinal axis of the vehicle body; the wheel track adjusting actuator comprises a driving device (18), a first electromagnetic clutch (17-1), a second electromagnetic clutch (17-2), and a front linear sliding rail device and a rear linear sliding rail device, the two linear sliding rail devices are paved on the chassis frame along the longitudinal axis of the vehicle body, a sliding block of each linear sliding rail device is driven by the driving device (18) through a transmission mechanism, power is transmitted to the sliding block of the front linear sliding rail device by the driving device (18) through the first electromagnetic clutch (17-1) and transmitted to the sliding block of the rear linear sliding rail device by the driving device through the second electromagnetic clutch (17-2), control signal input ends of the driving device (18) and the two electromagnetic clutches are each connected with the control system with start/stop and connection/disconnection controlled by the control system; the left and right driving wheel legs in the front of the vehicle body are each connected with the sliding block on the front linear sliding rail device through a connecting rod structure, and the left and right driving wheel legs in the rear of the vehicle body are each connected with the sliding block on the rear linear sliding rail device through a connecting rod structure; the connecting rod structure consists of a driving connecting rod (13-1) and a rocker arm extending rod (13-2), one end of the driving connecting rod is connected with one end of the rocker arm extending rod through a revolute pair and a self-locking connector, the other end of the rocker arm extension rod (13-2) is fixedly connected with the rocker arm (7) to drive the rocker arm (7) to rotate, the other end of the driving connecting rod (13-1) is hinged with a corresponding sliding block through the revolute pair to convert the linear movement of the sliding block into the rotary movement driving the rocker arm extending rod (13-2) to rotate with the rocker arm rotating shaft (12) as a center; the self-locking connector consists of a first connecting block (13-3), a second connecting block (13-5) and a positioning pin electromagnet (13-4); one of the connecting blocks is provided with a locking electromagnet (13-5-3), and after the locking electromagnet (13-5-3) is energized, the two connecting blocks are fixedly connected by magnetic adsorption and the self-locking connector is in a connected state; the first connecting block (13-3) is fixedly mounted at the end of the rocker arm extending rod (13-2), and the second connecting block (13-5) is connected with the driving connecting rod (13-1) through a revolute pair; the second connecting block (13-5) is provided with a limiting hole (13-5-2), and a positioning pin electromagnet (13-4) is mounted on the driving connecting rod (13-1); when the locking electromagnet (13-5-3) is de-energized, the first and second connecting blocks are out of the limitation of the magnetic adsorption, then the self-locking connector is disconnected, and the positioning pin electromagnet (13-4) is controlled to act simultaneously by the control system to allow the extending pin rod of the positioning pin electromagnet to be inserted into the limiting hole (13-5-2) of the second connecting block (13-5), so that the second connecting block (13-5) is prevented from freely rotating; the wheeled agricultural robot comprises the following four wheel track adjustment modes: A) synchronous four-wheel track adjustment mode: the first and second electromagnetic clutches and all the self-locking connectors are in a connected state, and the wheel tracks of the front wheels and the rear wheels are adjusted synchronously by the driving device (18) through the two linear sliding rail devices; B) independent front-wheel track adjustment mode: the first electromagnetic clutch and all the self-locking connectors are in a connected state, the second electromagnetic clutch is disconnected, and the wheel track of the front wheels is adjusted by the driving device (18) through the front linear sliding rail device; C) independent rear-wheel track adjustment mode: the second electromagnetic clutch and all the self-locking connectors are in a connected state, the first electromagnetic clutch is disconnected, and the wheel track of the rear wheels is adjusted by the driving device (18) through the rear linear sliding rail device; D) independent four-wheel position adjustment mode: the first and second electromagnetic clutches and all the self-locking connectors are in a disconnected state, and the distances between the four wheels and the longitudinal axis of the vehicle body can be independently adjusted; wherein, A), B) and C) are active adjustment modes, which mean that the rocker arm (7) is driven to swing transversely by controlling the driving device (18); D) is a passive adjustment mode, which mean that a corresponding wheel is driven to move forward or backward by independently controlling the hub motor to rotate, so that the rocker arm (7) is driven to swing transversely, changing the distance between the wheel and the longitudinal axis of the vehicle body.

2. The wheeled agricultural robot with a self-adaptive wheel track adjusting function according to claim 1, wherein: the second connecting block (13-5) is a convex block with a convex structure mounted on a surface abutting the first connecting block (13-3), the first connecting block (13-3) is a concave block with a concave structure adapted to the convex structure mounted on the abutting surface thereof; a pressure sensor (19) and a stroke switch (20) are arranged in the concave structure, the signal output ends of the pressure sensor (19) and the stroke switch (20) are connected with the control system; when the first and second connecting blocks are connected by the magnetic adsorption, the convex structure is embedded in the concave structure and can be contacted with the pressure sensor (19) and the stroke switch (20); if the signal fed back by the pressure sensor is not less than a preset threshold value, the fixation of the connecting rod structure is determined as firm by the control system, and a proper active adjustment mode is selected from the modes A)-C) to start a corresponding sliding block.

3. The wheeled agricultural robot with a self-adaptive wheel track adjusting function according to claim 2, wherein: the first connecting block (13-3) is provided with two inserting plates (13-3-2) positioned on the left side and the right side of the concave structure and protruding out of the abutting surface of the first connecting block (13-3), and the second connecting block (13-5) is provided with adaptable inserting grooves at the corresponding positions; when the first connecting block (13-3) and the second connecting block (13-5) are connected by the magnetic adsorption, the inserting plates (13-3-2) of the first connecting block (13-3) are jammed in the inserting grooves of the second connecting block (13-5), and the inner sides of the two inserting plates (13-3-2) are provided with chamfer slopes (13-3-2) facing the convex structure.

4. The wheeled agricultural robot with a self-adaptive wheel track adjusting function according to claim 1, wherein: the driving device (18) is a servo motor, the linear sliding rail device is a lead screw electric sliding rail device, and the servo motor is mounted to the middle of the chassis frame and positioned between the two lead screw electric sliding rail devices; the two electromagnetic clutches are mounted at the power input ends of the two lead screw electric sliding rail devices near the center of the chassis, and the output shafts of the servo motor are connected with the input shafts of the two electromagnetic clutches through the transmission mechanism, that is, the power is transmitted to the front and rear lead screw electric sliding rail devices through the two electromagnetic clutches.

5. The wheeled agricultural robot with a self-adaptive wheel track adjusting function according to claim 1, wherein: the side of the linear sliding rail device is provided with a grating ruler (16) to measure the stroke of the sliding block on the rail, and connected with the control system, so that the wheel track is accurately controlled by the control system through the control of the stroke of the sliding block.

6. The wheeled agricultural robot with a self-adaptive wheel track adjusting function according to any of claims 1-5, further comprising a navigation system, wherein the wheel track adjusting actuator is controlled to act by the control system according to a signal fed back by the navigation system; the navigation system comprises a terrain detection sensor (6), a satellite positioning receiver (5) and an inertial sensor, and according to the terrain information detected by the terrain detection sensor, the vehicle body position information received by the satellite positioning receiver and the vehicle body attitude information fed back by the inertial sensor, the crop row position and the crop row spacing in front of the vehicle body is analyzed by the control system, and an adaptable wheel track adjustment amount is calculated to output a corresponding control signal to the wheel track adjusting actuator.

7. A manual wheel track adjusting method based on the wheeled agricultural robot according to any of claims 1-6 applied in a passive adjustment mode D) and performed in a non-driving state of the vehicle body, comprising the following steps: 1) the wheel track adjustment amount of each driving wheel leg is planned in advance according to the terrain or the crop row spacing in front of the vehicle body, and an adjusting instruction is sent to the control system of the robot by an operator through a remote control terminal based on the wheel track adjustment amount; 2) after receiving the adjusting instruction, firstly, all the self-locking connectors are controlled to be disconnected by the control system; secondly, the driving device of the wheel track adjusting actuator is controlled to start to push the sliding block on each linear sliding rail device to the initial position; then the first and second electromagnetic clutches are controlled to be disconnected simultaneously; finally, corresponding control instructions are output to the hub motor (14) and the steering motor to drive the wheel (10) to move forward or backward around the rocker arm rotating shaft (12), so that the vertical distance between the wheel and the longitudinal axis of the vehicle body is changed; after the wheel is adjusted in place, the hub motor (14) is controlled to stop rotating, and an electric band-type brake (21) at the rocker arm rotating shaft is controlled to act immediately to fix the rocker arm.

8. An automatic wheel track adjusting method based on the wheeled agricultural robot according to claim 6 applied in the active adjustment modes A), B) or C), comprising the following steps: 1) a three-dimensional laser radar is mounted in the front of the vehicle body as the terrain detection sensor, in the running process of the agricultural robot, the ground and crops in front of the vehicle body are scanned using the three-dimensional laser radar, a field scene three-dimensional point cloud map based on the vehicle body is established using the vehicle body position data sent by the satellite positioning system and the chassis frame attitude data fed back by the inertial sensor, and the field scene three-dimensional point cloud map is converted into a point cloud map based on a geodetic coordinate system OXYZ, wherein a vertical Z coordinate represents the height from the ground of a three-dimensional point, an X direction represents the longitudinal direction of a horizontal plane, namely the running direction of the robot, and a Y direction represents the transverse direction of the horizontal plane perpendicular to the X direction; 2) a reasonable height threshold value of the crops is preset according to the type of crops and the growth stage of the crops, and points with a height coordinate greater than the height threshold value in the field scene three-dimensional point cloud map are determined as points of crop row clusters, so that the point clouds of the crop row clusters are separated from the three-dimensional point cloud map, then a middle point of each of the crop row clusters is calculated, and the longitudinal connecting line of the middle points is a central line of the crop row; 3) after obtaining the central line of the crop row, the crop row spacing in front of the vehicle body is calculated in real time according to the current position of the vehicle body of the robot, and the theoretical width of the front wheels and the rear wheels, namely the target width of wheel track adjustment, is calculated based on the position between the lines where the left and right wheels of the vehicle body are positioned or the number of lines spanned; 4) the actual width of the wheel track is obtained, the difference value between the actual width of the wheel track and the target width of the wheel track adjustment is calculated, a corresponding control instruction is output to a linear sliding rail device by the control system based on a control strategy with a change dependency of the wheel track and the crop row, the rocker arm is driven to rotate by a certain yaw angle through the movement of the sliding block, and the distance between the front/rear wheels and the longitudinal axis of the vehicle body is adjusted to adapt to the crop row spacing in front of the vehicle body.

9. The automatic wheel track adjusting method according to claim 8, wherein in step 1), a Hessian plane equation is fitted by a RANSAC algorithm based on the field scene three-dimensional point cloud map, and the detected ground is refined and reconstructed by the least square fitting.