Novel all-terrain self-adaptive four-wheel independent drive agricultural robot chassis and control method thereof

Abstract

The invention discloses a novel all-terrain self-adaptive four-wheel independent drive agricultural robot chassis and a control method thereof, a power unit is composed of two pairs of hub motors coupled to the two sides of a front steering shaft and the two sides of a rear steering shaft, and a control unit is responsible for real-time drive control of the four hub motors; the differential steering unit consists of a front door-shaped steering axle and a rear door-shaped steering axle, and is connected with the frame through a plane slewing bearing; and the damping unit is arranged on a steering axle between the hub motor and the frame. The invention relates to a novel all-terrain self-adaptive four-wheel independent drive agricultural robot chassis which adopts a front and rear axle synchronous differential steering mode and has the advantages of small steering radius and low torque. Spring damping is adopted to achieve the three-point structural design of the chassis, it is guaranteed that the four driving wheels are adaptive to the terrain, suspension and slipping are avoided, enough driving torque is provided, and the four-wheel-drive four-wheel robot has the advantages of being stable in operation, diverse in operation scene, flexible, high in trafficability and the like, and can meet the requirement for stable operation in the complex agricultural environment.

Description

Technical Field

[0001] The present invention belongs to the fields of intelligent agricultural machinery equipment, agricultural machinery control and agriculture, and specifically relates to a novel all-terrain adaptive four-wheel independently driven agricultural robot chassis. Background Art

[0002] As a major agricultural country, my country's agricultural production mechanization level is of great significance to ensuring food security. With the acceleration of agricultural modernization, traditional agricultural operations are facing severe challenges. At present, the main technical bottlenecks of field operation robots are insufficient terrain adaptability, lack of movement flexibility and limited intelligent control level. Traditional agricultural robots use wheeled or crawler chassis, which generally have problems such as poor passability and easy slipping and sinking in complex farmland environments (such as muddy fields, slopes, ridges, etc.), making it difficult to ensure the passability and stability of farmland operations. In addition, the traditional steering mechanism is limited by the turning radius, making it difficult to turn in narrow fields and low operating efficiency. Existing technologies are difficult to achieve complex movement modes such as zero-radius turning and oblique movement, which restricts the accuracy and efficiency of operations.

[0003] Therefore, developing an agricultural robot chassis with all-terrain adaptability, high motion flexibility, and intelligent control system has become an important technical direction to promote the development of agricultural mechanization towards intelligence. Summary of the Invention

[0004] In response to the technical bottlenecks of existing agricultural robot chassis in terms of adaptability to complex terrain and movement flexibility, the present invention proposes a new all-terrain adaptive four-wheel independent drive agricultural robot chassis. Through innovative mechanical structure and intelligent control system, it can significantly improve the robot's passability and stability in complex farmland environments, providing reliable technical support for the development of modern agricultural mechanization.

[0005] The technical solution of the present invention includes: a new all-terrain adaptive four-wheel independent drive agricultural robot chassis, including a power unit, a control unit and a shock absorption unit:

[0006] The power unit is responsible for executing the movement instructions of the agricultural robot, and includes a hub motor (6), a shock-absorbing long rod (5), a slewing bearing (11), a slewing bearing base (10), and an angle sensor frame (7); the single output shaft of the hub motor (6) is an M24 screw, which can be connected to the shock-absorbing long rod (5) through the screw and screwed with an M24 nut; the inner ring of the slewing bearing (11) is connected and fixed to the fixed square tube (9) through the slewing bearing base (10) through the M5 screw, and the outer ring of the slewing bearing (11) is connected to the frame (1) of the agricultural robot through the M5 screw through the angle sensor frame (7);

[0007] The control unit is responsible for controlling the rotation speed and steering of the four wheels to achieve the movement of the agricultural robot, including:

[0008] Two high-power wheel hub motor drivers, each one dragging two, are connected to the wheel hub motors; an onboard computer, with a built-in main control unit, is connected to the inertial navigation module, the GNSS navigation module, the remote control module, the angle sensor module (12), the 4G communication module, and the motor driver; the motor driver is fixed to the middle area of ​​the vehicle frame (1) by M4 screws, the onboard computer is fixed to the top of the front axle wheel by Velcro, and the angle sensor module (12) is fixed to the angle sensor frame (7) by M3 screws;

[0009] The shock absorbing unit is responsible for adapting to the uneven ground in a complex environment. One end of the shock absorbing long rod (5) is connected to the wheel hub motor (6), and the other end is connected to a connecting round tube (8); the connecting round tube (8) is embedded in the fixed square tube (9) and fixed in a cross manner by M8 screws and cannot be rotated; the shock absorbing long rod (5) can be rotated at the connection with the connecting round tube (8), and the middle part of the shock absorbing long rod (5) is connected to a shock absorber (4) by M8 screws, and the other end of the shock absorber (4) is connected to the square tube clamp (3), and the square tube clamp (3) is fixed on the fixed square tube (9).

[0010] Furthermore, the plane slewing bearing (11) is connected to the vehicle frame (1), the inner ring of the slewing bearing (11) is rigidly connected to the fixed square tube (9) through the slewing bearing base (10), and the outer ring is fixed to the vehicle frame (1), so that the wheel can deflect freely around the center of the bearing, and the steering power is provided by the differential drive of the wheel hub motors (6) on both sides, and the steering angle is formed by the speed difference of the wheels on both sides. At the same time, the shock-absorbing long rod (5) and the slewing bearing (11) work together, and the angle sensor (12) is fixed on the angle sensor frame (7) to monitor the steering angle change in real time to ensure the stability and accuracy of the steering process. The above components constitute a differential steering unit.

[0011] Furthermore, the frame (1) is made of stainless steel; the slewing bearing (11), the fixed square tube (9), the connecting round tube (8), the angle sensor frame (7), the slewing bearing base (10), and the shock-absorbing long rod (5) are made of aluminum alloy; the shock absorber (4) is made of alloy spring steel; in order to ensure that the agricultural robot can be used for a long time in a muddy agricultural environment, the frame (1) is sprayed with anti-rust paint for rust prevention, and the slewing bearing (11) is coated with anti-rust oil.

[0012] Furthermore, the shock absorption system adopts a composite connection structure of a shock absorber (4) and a shock absorption long rod (5), wherein the shock absorber (4) is arranged vertically to absorb ground impact, and the connecting round tube (8) is rigidly connected to the fixed square tube (9) through a cross screw, forming a suspension system with both shock absorption performance and lateral stability; the slewing bearing (11) adopts a precision roller bearing structure, the inner ring of which is connected to the fixed square tube (9), and the outer ring is fixed to the frame (1), and cooperates with a high-precision angle sensor (12) to achieve a steering control accuracy of ±0.1°; the four wheel hub motors (6) are synchronously controlled through the CAN bus and support the electronic differential function, so that the chassis has special maneuvering capabilities such as crab walking and turning in place.

[0013] Furthermore, the control unit adopts a three-level safety protection mechanism: primary protection realizes early warning by real-time monitoring of motor temperature and current; intermediate protection automatically adjusts power distribution when detecting that the wheel speed difference exceeds a threshold; ultimate protection directly cuts off the main circuit by the emergency stop switch; the power management system can automatically optimize the four-wheel torque output according to the terrain resistance and the working load, preferentially activates the two-wheel drive mode on flat roads to reduce energy consumption, and automatically switches to the four-wheel drive mode on complex terrain; the shock absorber (4) realizes passive shock absorption adjustment through mechanical structure design, and its stiffness characteristics are optimized and matched to adapt to the terrain change requirements of common farmland working environments.

[0014] A control method for a novel all-terrain adaptive four-wheel independent drive agricultural robot chassis of the present invention comprises the following steps:

[0015] Step 1: Turn on the power switch and power on all modules of the agricultural robot chassis; the power unit and control unit complete the power-on self-test, and the onboard computer, wheel hub motor driver (7) and angle sensor (12) enter the standby state;

[0016] Step 2, the system performs initialization operations and self-checks each module; detects the communication status and steering freedom of the four wheel hub motors (6), verifies the consistency between the reading of the angle sensor (12) and the actual steering angle of the wheel hub, tests the travel range and response speed of the shock absorber (4), and issues an audible and visual alarm if the self-check fails;

[0017] Step 3: Wait for the operator to select the control mode; two modes are provided: "manual remote control" and "automatic navigation". If there is no operation within one minute, the system will default to "manual remote control" mode;

[0018] Step 4: Wait for the chassis control system to unlock. The agricultural robot needs to release the mechanical lock through the physical switch. After unlocking, the chassis enters the operation-ready state. If there is no operation instruction within five minutes, the system will be locked again.

[0019] Step 5: Wait for the operator to set the operating parameters. Manual remote control mode requires manual control of the reference steering angle and travel speed, while automatic mode operates according to the input GNSS operating path or preset program. If no parameter settings are received within one minute, the system defaults to low-power standby mode.

[0020] Step 6: The system executes the motion control instructions. In the manual remote control mode, the robot needs to respond to the joystick instructions in real time and independently control the steering and speed of the four wheels. In the automatic navigation mode, the robot calculates the path deviation based on the RTK-GNSS positioning data and dynamically adjusts the steering angle of each wheel based on the deviation through the PID algorithm. The system monitors the temperature and load status of the hub motor (6) in real time and automatically reduces the power when the limit is exceeded.

[0021] Step 7: After the task is completed, the robot enters a safe state and automatically executes the following safety instructions: the four-wheel steering angle returns to zero, the motor slows down and stops, and the mechanical brake lock is activated.

[0022] Furthermore, the method also includes adopting a multiple protection design: in automatic navigation mode, the global navigation satellite GNSS positioning system and the inertial navigation unit constitute a main-backup navigation system, which automatically switches to the inertial navigation mode when the satellite signal is lost to ensure positioning continuity; in manual remote control mode, basic safety protection functions are retained, and the output power is automatically limited when motor overload or abnormal steering is detected; path tracking control adopts an improved model predictive control MPC algorithm, and by introducing a terrain resistance coefficient compensation mechanism, the straight-line tracking error is stably controlled within the range of ±5cm, and the path correction response time is shortened to less than 1 second; the system is also equipped with mode switching interlock protection to ensure a smooth transition when switching between automatic and manual modes.

[0023] The present invention has the following advantages:

[0024] 1. Outstanding all-terrain adaptability: The innovative design of four-wheel independent drive and steering, combined with a shock-absorbing system, gives the chassis excellent terrain maneuverability. Each wheel group can independently adjust the steering angle and drive speed, enabling multiple modes including straight-line driving, on-the-spot turning, and diagonal movement.

[0025] 2. Simple structure and low steering torque. Unlike traditional Ackerman and slip differential structures that have to overcome the lateral force generated by the tires and the ground when steering, this chassis achieves synchronous differential steering of the front and rear steering shafts through a collaborative control method. It only needs to overcome the torque difference on both sides of the steering axle generated by the lateral force of the tires to achieve steering.

[0026] 3. The front and rear axles have synchronous steering with a small steering radius. The designed control method can realize omnidirectional movement modes such as turning around on the spot and crab walking to adapt to different working scenarios.

[0027] 4. High-Precision Motion Control: Utilizing a high-precision GNSS / IMU integrated navigation system and an innovative four-wheel coordinated control algorithm, the system achieves a path tracking error of no more than ±5cm. The system is equipped with intelligent terrain recognition, which automatically identifies different terrains—hard surfaces, muddy ground, and slopes—through multi-sensor data fusion, and dynamically adjusts control parameters.

[0028] 5. High Reliability: Key components are made of stainless steel and aluminum alloy, and all exposed metal parts undergo special rust-proofing treatment. The unique waterproof structure design (IP67 protection level) allows it to withstand the demands of heavy rain, and the intelligent power distribution system can save energy by more than 20%.

[0029] 6. The chassis offers excellent scalability: Standardized mechanical interfaces and open communication protocols enable rapid adaptation to a variety of agricultural implements, including planters, rice transplanters, and sprayers. The 5G communication module supports remote monitoring and cloud-based data exchange, providing data support for precision agriculture. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0031] Figure 2 This is a structural diagram of the bearing connection unit of the present invention;

[0032] Figure 3 Schematic diagram of the function of the present invention; (a) is turning; (b) is oblique movement;

[0033] Figure 4 It is a hardware structure diagram of the present invention;

[0034] Figure 5 is a control flow chart of the present invention;

[0035] In the figure, 1-frame; 2-iron wire; 3-square tube clamp; 4-shock absorber; 5-shock absorber rod; 6-wheel hub motor; 7-angle sensor frame; 8-connecting round tube; 9-fixed square tube; 10-slewing bearing base; 11-slewing bearing; 12-angle sensor; 13-coupling; DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the examples of the present invention.

[0037] like Figure 1 The overall structural diagram of the present invention is shown in the figure. The four-wheel independent drive agricultural robot chassis consists of a power unit, a shock absorbing unit and a control unit;

[0038] The power unit adopts a symmetrical frame design and is mainly composed of a frame (1), a slewing bearing (11), a fixed square tube (9), and a connecting round tube (8). A set of independent drive wheels are configured at each of the four corners of the chassis. Each wheel set includes a hub motor (6) and a shock-absorbing long rod (5), and an omnidirectional steering function is achieved through the slewing bearing (11). The inner ring of the slewing bearing (11) is rigidly connected to the fixed square tube (9) through M5 screws, and the outer ring is fixed to the frame (1). This design ensures both steering flexibility and overall structural strength.

[0039] The shock absorption system adopts a unique shock absorber (4) in combination with an inclined shock absorption long rod (5). One end of the shock absorption long rod (5) is connected to the wheel hub motor (6), and the other end is connected to a connecting round tube (8). The connecting round tube (8) is embedded in a fixed square tube (9) and fixed in a cross-staggered manner by M8 screws and cannot be rotated. The shock absorption long rod (5) can rotate at the connection with the connecting round tube (8), and the middle part of the shock absorption long rod (5) is connected to a shock absorber (4) by an M8 screw. The other end of the shock absorber (4) is connected to a square tube clamp (3), and the square tube clamp (3) is fixed on the fixed square tube (9).

[0040] The iron wire (2) of the present invention is used to prevent the shock-absorbing long rod (5) from falling off.

[0041] The hardware layout of the control system fully considers the requirements of waterproofing and dustproofing. Two high-power hub motor drivers are symmetrically installed in the middle area of ​​the frame, and the surface is covered with an aluminum alloy protective cover. The main control computer is fixed directly above the front wheel assembly with shock-proof Velcro to facilitate heat dissipation and maintenance. All electrical connections use waterproof connectors, and the cables are routed along the inside of the fixed square tube (9), which is both beautiful and effectively protects the cables. The angle sensor (12) is precisely installed on the angle sensor frame (7), and the measuring surface is aligned with the axis of the slewing bearing (11), ensuring that the steering angle detection accuracy reaches ±0.5°.

[0042] like Figure 2 The bearing connection unit structure diagram of the present invention is shown. The angle sensor (12) is fixed to the angle sensor frame (7) by M3 screws. At the same time, the angle sensor frame (7) is connected to the outer ring of the slewing bearing (11), and the connection is slightly protruding. The inner ring of the slewing bearing (11) is connected to the slewing bearing base (10) by M5 screws. The small cylindrical body protruding in the middle of the slewing bearing base (10) is connected to the angle sensor (12) by a coupling (13). The inner ring of the slewing bearing (11), the slewing bearing base (10), and the fixed square tube (9) are connected by 6 M5 screws. The outer ring of the slewing bearing (11), the angle sensor frame (7), and the frame (1) are connected by 6 M5 screws.

[0043] like Figure 3The schematic diagram of the present invention when turning is shown. The four-wheel independent drive agricultural robot chassis of the present invention realizes functions such as steering, oblique driving and in-place steering through the differential rotation of the four wheels. Under normal steering conditions, the speed of the outer wheel group (6-1, 6-3) increases and the torque increases to overcome centrifugal resistance; the inner wheel group (6-2, 6-4) synchronously reduces the speed and reduces the torque output. The four-wheel steering angle is dynamically adjusted through the Ackerman steering geometry relationship (front wheel steering angle range ±35°, rear wheel ±25°) to ensure wheel track overlap and reduce steering radius error. During the steering process, the wheel speed difference is synchronously calibrated with a 1ms cycle through the CAN bus to improve the speed control accuracy and reduce the steering angle deviation. Under the coordination of oblique movement, the four wheels are synchronously deflected by an angle of θ (0°<θ≤75°), the steering axis parallelism error, the wheel group (6-1 to 6-4) speed is strictly synchronized, and the torque of the wheel group in the forward direction is increased. The left wheel set (6-1, 6-3) and the right wheel set (6-2, 6-4) steer symmetrically at ±90°, with equal absolute speeds and opposite directions, and with equal torque symmetry. Steering center offset is compensated in real time using inertial measurement unit (IMU) data, improving control accuracy. The system utilizes a torque coupling algorithm, automatically increasing static friction torque on the inner wheel set to prevent steering slip.

[0044] like Figure 4 The hardware structure diagram of the present invention is shown. The highly integrated control system architecture of the four-wheel independently driven agricultural robot chassis of the present invention adopts a master-slave distributed design. The main control unit is built with a high-performance ARM core. Two one-to-two motor drivers and various sensor modules are connected via a dual-channel CAN bus network to form a complete control closed loop. The main control unit integrates an IMU inertial measurement module and a rich communication interface, and cooperates with a dual-antenna RTK-GNSS positioning system to achieve centimeter-level navigation and positioning accuracy. Each driver can independently control two wheel hub motors and monitor key parameters such as motor temperature and current in real time. The power management system is equipped with a 48V battery pack and an intelligent battery management system (BMS) to provide a stable and reliable power supply for each module. The entire hardware architecture adopts a modular design concept. Each functional module maintains relative independence while closely coordinating through standard interfaces. All electrical connections meet the IP67 protection level, and key signal channels are redundant to ensure stable operation of the system in complex farmland environments. This highly integrated and intelligent hardware design not only achieves precise control of the four-wheel independently driven system, but also leaves ample room for future functional expansion, fully demonstrating the innovation and advancement of the present invention in the field of agricultural robot chassis control.

[0045] like Figure 4The control flow chart of the present invention is shown. After powering on, the system first executes an initialization procedure, completing sensor calibration, establishing a communication link, and performing a system self-test. If any self-test anomalies are detected, the system immediately triggers an audible and visual alarm. After passing the self-test, it enters a standby state, awaiting the operator's selection of a control mode. The operator can select "manual remote control" or "autopilot" mode via the control panel. If no selection is made within one minute, the system defaults to manual remote control mode. After selecting the mode, the operator must complete a security verification to release the mechanical lock, and the system status indicator will turn from red to green to indicate successful unlocking. In manual remote control mode, the operator directly controls the chassis movement using the joystick, and the system displays the steering angle and speed of each wheel in real time. In autopilot mode, the system autonomously plans the optimal driving route based on a preset path. During the task, the safety monitoring module continuously monitors operating parameters and immediately activates a hierarchical protection mechanism if an anomaly is detected. Upon completion of the task, the system automatically controls the chassis to return, straightens the four wheels, and activates the mechanical brake lock.

[0046] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0047] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and alterations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A new all-terrain adaptive four-wheel independent drive agricultural robot chassis, characterized by: Including power unit, control unit and shock absorber unit: The power unit is responsible for executing the movement instructions of the agricultural robot, and includes a hub motor (6), a shock-absorbing long rod (5), a slewing bearing (11), a slewing bearing base (10), and an angle sensor frame (7); the single output shaft of the hub motor (6) is an M24 screw, which can be connected to the shock-absorbing long rod (5) through the screw and screwed with an M24 nut; the inner ring of the slewing bearing (11) is connected and fixed to the fixed square tube (9) through the slewing bearing base (10) through the M5 screw, and the outer ring of the slewing bearing (11) is connected to the frame (1) of the agricultural robot through the M5 screw through the angle sensor frame (7); The control unit is responsible for controlling the rotation speed and steering of the four wheels to achieve the movement of the agricultural robot, including: Two high-power wheel hub motor drivers, each one dragging two, are connected to the wheel hub motors; an onboard computer, with a built-in main control unit, is connected to the inertial navigation module, the GNSS navigation module, the remote control module, the angle sensor module (12), the 4G communication module, and the motor driver; the motor driver is fixed to the middle area of ​​the vehicle frame (1) by M4 screws, the onboard computer is fixed to the top of the front axle wheel by Velcro, and the angle sensor module (12) is fixed to the angle sensor frame (7) by M3 screws; The shock absorbing unit is responsible for adapting to the uneven ground in a complex environment. One end of the shock absorbing long rod (5) is connected to the wheel hub motor (6), and the other end is connected to a connecting round tube (8); the connecting round tube (8) is embedded in the fixed square tube (9) and fixed in a cross manner by M8 screws and cannot be rotated; the shock absorbing long rod (5) can be rotated at the connection with the connecting round tube (8), and the middle part of the shock absorbing long rod (5) is connected to a shock absorber (4) by M8 screws, and the other end of the shock absorber (4) is connected to the square tube clamp (3), and the square tube clamp (3) is fixed on the fixed square tube (9).

2. A chassis according to claim 1, characterized in that: The plane slewing bearing (11) is connected to the vehicle frame (1), the inner ring of the slewing bearing (11) is rigidly connected to the fixed square tube (9) through the slewing bearing base (10), and the outer ring is fixed to the vehicle frame (1), so that the wheel can deflect freely around the center of the bearing. The steering power is provided by the differential drive of the wheel hub motors (6) on both sides, and the steering angle is formed by the speed difference of the wheels on both sides. At the same time, the shock-absorbing long rod (5) and the slewing bearing (11) work together. The angle sensor (12) is fixed on the angle sensor frame (7) to monitor the change of the steering angle in real time to ensure the stability and accuracy of the steering process. The above components constitute a differential steering unit.

3. A chassis according to claim 1, characterized in that: The frame (1) is made of stainless steel; the slewing bearing (11), the fixed square tube (9), the connecting round tube (8), the angle sensor frame (7), the slewing bearing base (10), and the shock-absorbing long rod (5) are made of aluminum alloy; the shock absorber (4) is made of alloy spring steel; in order to ensure that the agricultural robot can be used for a long time in a muddy agricultural environment, the frame (1) is sprayed with anti-rust paint for rust prevention, and the slewing bearing (11) is coated with anti-rust oil.

4. A chassis according to claim 1, characterized in that: The shock absorption system adopts a composite connection structure of a shock absorber (4) and a shock absorption long rod (5), wherein the shock absorber (4) is arranged vertically to absorb ground impact, and the connecting round tube (8) is rigidly connected to the fixed square tube (9) through a cross screw, forming a suspension system with both shock absorption performance and lateral stability; the slewing bearing (11) adopts a precision roller bearing structure, the inner ring of which is connected to the fixed square tube (9), and the outer ring is fixed to the frame (1), and cooperates with a high-precision angle sensor (12) to achieve a steering control accuracy of ±0.1°; the four wheel hub motors (6) are synchronously controlled through a CAN bus and support an electronic differential function, so that the chassis has special maneuvering capabilities such as crab walking and turning in place.

5. A chassis according to claim 1, characterized in that: The control unit adopts a three-level safety protection mechanism: the primary protection realizes early warning by real-time monitoring of motor temperature and current; Intermediate protection automatically adjusts power distribution when it detects that the wheel speed difference exceeds a threshold; ultimate protection is achieved by directly cutting off the main circuit by the emergency stop switch; the power management system can automatically optimize the four-wheel torque output according to the terrain resistance and operating load, and preferentially activate the two-wheel drive mode on flat roads to reduce energy consumption, and automatically switch to the four-wheel drive mode on complex terrain; the shock absorber (4) realizes passive shock absorption adjustment through mechanical structure design, and its stiffness characteristics are optimized and matched to adapt to the terrain changes required in common farmland working environments.

6. The control method of a novel all-terrain adaptive four-wheel independent drive agricultural robot chassis according to claim 1 is characterized in that: The following steps are involved: Step 1: Turn on the power switch and power on all modules of the agricultural robot chassis; the power unit and control unit complete the power-on self-test, and the onboard computer, wheel hub motor driver (7) and angle sensor (12) enter the standby state; Step 2, the system performs initialization operations and self-checks each module; detects the communication status and steering freedom of the four wheel hub motors (6), verifies the consistency between the reading of the angle sensor (12) and the actual steering angle of the wheel hub, tests the travel range and response speed of the shock absorber (4), and issues an audible and visual alarm if the self-check fails; Step 3: Wait for the operator to select the control mode; two modes are provided: "Manual remote control" and "Automatic navigation". If there is no operation within one minute, the system will default to "Manual remote control" mode; Step 4: Wait for the chassis control system to unlock. The agricultural robot needs to release the mechanical lock through the physical switch. After unlocking, the chassis enters the operation-ready state. If there is no operation instruction within five minutes, the system will be locked again. Step 5: Wait for the operator to set the operating parameters. Manual remote control mode requires manual control of the reference steering angle and travel speed, while automatic mode operates according to the input GNSS operating path or preset program. If no parameter settings are received within one minute, the system defaults to low-power standby mode. Step 6: The system executes the motion control instructions. In the manual remote control mode, the robot needs to respond to the joystick instructions in real time and independently control the steering and speed of the four wheels. In the automatic navigation mode, the robot calculates the path deviation based on the RTK-GNSS positioning data and dynamically adjusts the steering angle of each wheel based on the deviation through the PID algorithm. The system monitors the temperature and load status of the hub motor (6) in real time and automatically reduces the power when the limit is exceeded. Step 7: After the task is completed, the robot enters a safe state and automatically executes the following safety instructions: the four-wheel steering angle returns to zero, the motor slows down and stops, and the mechanical brake lock is activated.

7. The method according to claim 6, characterized in that The method also includes the use of a multiple-security design: in automatic navigation mode, the global navigation satellite GNSS positioning system and the inertial navigation unit form a main-backup navigation system, which automatically switches to the inertial navigation mode when the satellite signal is lost to ensure positioning continuity; in manual remote control mode, basic safety protection functions are retained, and the output power is automatically limited when motor overload or abnormal steering is detected; path tracking control adopts an improved model predictive control MPC algorithm, and by introducing a terrain resistance coefficient compensation mechanism, the straight-line tracking error is stably controlled within the range of ±5cm, while the path correction response time is shortened to less than 1 second; the system also has a mode switching interlock protection to ensure a smooth transition when switching between automatic and manual modes.

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