A high-obstacle hilly farm machine universal power chassis and an automatic leveling control method thereof

Abstract

A high-obstacle hilly farm machine universal power chassis and an automatic leveling control method thereof, the high-obstacle hilly farm machine universal power chassis adopts the automatic leveling control method of the farm machine universal power chassis, and automatically adjusts the chassis posture in complex terrains through a virtual control model, comprising: constructing a virtual control model architecture of a wheel-leg type all-terrain chassis; performing adaptive force tracking control, based on the virtual control model of the wheel-leg type all-terrain chassis, dynamically adjusting control parameters to realize adaptive control to suppress system disturbance, and through error feedback, optimizing impedance characteristics in real time, minimizing force tracking error, and compensating for system uncertainty; and performing posture guidance control, based on the virtual control model of the wheel-leg type all-terrain chassis, calculating a posture deviation; calculating virtual forces and torques of the all-terrain chassis base, and converting them into contact forces between the leg ends and the ground; according to the posture deviation and the contact forces, controlling the driving wheels of the chassis to adjust the chassis posture to keep the chassis stable.

Description

Technical Field

[0001] This invention relates to all-terrain vehicle chassis control technology, and in particular to a general-purpose power chassis for agricultural machinery in high-altitude obstacle-crossing hills and its automatic posture leveling control method for wheel-leg type all-terrain chassis based on a virtual control model. Background Technology

[0002] Hilly and mountainous terrain is complex with significant elevation changes. Existing agricultural machinery, due to its fixed chassis or simple suspension structure, is unable to adapt to complex terrains such as gullies and steep slopes, resulting in insufficient mobility and difficulty in adapting to the working environment. Furthermore, when operating on inclined ground, the chassis of existing agricultural machinery is prone to tilting or pitching, affecting operational safety and accuracy. Wheel-leg chassis combine the mobility of wheels with the adaptability of legs. Hydraulic cylinders drive the outriggers to rotate around the chassis, while the extension and retraction of the hydraulic cylinders adjust the chassis posture, making it an ideal solution for hilly terrain. However, the PID control used in existing wheel-leg chassis has a slow response speed, making it difficult for the chassis to cope with posture fluctuations caused by sudden changes in terrain. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies of the prior art by providing a general-purpose power chassis for agricultural machinery in hilly terrain with high obstacle crossing capabilities and its automatic leveling control method.

[0004] To achieve the above objectives, this invention provides an automatic leveling control method for a general-purpose power chassis for agricultural machinery, applicable to the automatic leveling of wheel-leg all-terrain chassis. The method utilizes a virtual control model to automatically adjust the chassis posture in complex terrain, ensuring stability during movement. The method includes the following steps:

[0005] A virtual control model for a wheel-leg all-terrain chassis is constructed. By describing the chassis attitude and the attitude of the control base, a virtual control model under the base coordinate system {B} is established. At the same time, virtual forces are allocated so that the virtual forces are transformed into contact forces between each drive leg and the environment. The contact forces are then mapped to the torque in the joint space using the Jacobian matrix.

[0006] Adaptive force tracking control is implemented by dynamically adjusting control parameters based on the virtual control model of this wheel-leg all-terrain chassis. To achieve adaptive control and suppress system disturbances, and to optimize impedance characteristics in real time through error feedback, minimizing force tracking error and compensating for system uncertainties; and

[0007] Attitude guidance control is performed based on the virtual control model of the wheel-leg all-terrain chassis. The actual roll angle, pitch angle, and yaw angle of the base are acquired in real time through the inertial measurement unit and compared with the preset horizontal attitude to calculate the attitude deviation. The virtual force and torque of the all-terrain chassis base are calculated and distributed to each support leg, which is converted into the contact force between the end of the support leg and the ground. According to the calculated attitude deviation and contact force, the wheels of the drive chassis are controlled to adjust the chassis attitude to maintain chassis stability.

[0008] The aforementioned automatic leveling control method for a general-purpose power chassis of agricultural machinery, in the adaptive force tracking control step, establishes a second-order dynamic equation for the force error based on the mass matrix, damping matrix, and stiffness matrix, and introduces a time-varying coefficient. and auxiliary functions An error equation containing time-varying parameters is constructed, and the impedance parameters are dynamically adjusted to compensate for system uncertainties.

[0009] The aforementioned automatic leveling control method for general-purpose power chassis of agricultural machinery also includes verifying the stability of the closed-loop system through the Lyapunov energy function to ensure the convergence of force tracking error.

[0010] The above-mentioned automatic leveling control method for a general-purpose agricultural machinery chassis involves establishing a 6-DOF virtual joint between the world coordinate system {W} and the chassis base coordinate system {B}. The system pose is described by parametrically transforming the base coordinate system through this virtual joint and coupling the outrigger joint coordinates. The virtual control model for the wheel-leg all-terrain chassis is as follows:

[0011] ;

[0012] in, The RPY angle of the base coordinate system {B} relative to the world coordinate system {W}, including the roll angle. Pitch angle and deflection angle ; Let {B} be the position vector of the origin of the base coordinate system {B} in the world coordinate system {W}; These are the joint coordinates of the chassis outriggers.

[0013] The above-mentioned automatic leveling control method for general-purpose power chassis of agricultural machinery includes a posture guidance control step in which virtual components are constructed in the three-dimensional movement direction and the three-dimensional rotation direction of the base for posture guidance control. Force and torque are simulated by virtual springs and damping components. The required virtual force and torque are calculated based on the desired posture, angle and angular velocity and the actual posture, angle and angular velocity during travel. The virtual force is then distributed to the contact force at the end of each outrigger to drive the chassis to automatically level.

[0014] The above-mentioned automatic leveling control method for general-purpose agricultural machinery chassis, wherein the virtual force and virtual torque acting on the chassis center of gravity are respectively:

[0015] ;

[0016] ;

[0017] ;

[0018] in, It is the virtual force generated by the virtual component on the Z-axis. and These are the virtual moments at the roll angle and pitch angle, respectively. The elastic coefficient, Let h be the damping coefficient, and h be the real-time height corresponding to the Z-axis coordinate, and its derivative be... The rate of change of chassis height. and These are the angles and velocities of the roll and pitch angles, respectively, fed back by the sensors. d The desired height is the center of mass of the chassis base, with the subscript d indicating the desired value.

[0019] The aforementioned automatic leveling control method for general-purpose agricultural machinery chassis involves determining the desired machine position based on the terrain. and posture and its expected speed and attitude angular velocity The actual position z and attitude angle of the chassis during movement are combined with feedback. ,speed and attitude angular velocity Calculate the virtual forces on the all-terrain chassis base. and torque The virtual force and torque of the chassis base are then distributed to each support leg, which is converted into the contact force between the end of the support leg and the ground, so as to achieve the desired motion control of the base and the automatic leveling of the chassis.

[0020] To better achieve the above objectives, the present invention also provides a general-purpose power chassis for agricultural machinery in hilly areas with high obstacle crossing capabilities, including a frame and traveling steering wheel legs, a power mechanism, a hydraulic system, and an electronic control system mounted on the frame. The electronic control system is connected to the traveling steering wheel legs, the power mechanism, and the hydraulic system respectively. The electronic control system controls the raising and lowering of the traveling steering wheel legs to achieve climbing and obstacle crossing, and adopts the above-mentioned automatic leveling control method of the general-purpose power chassis for agricultural machinery to achieve automatic adjustment of the chassis posture in complex terrain, so as to adapt to the needs of operation in complex terrain in hilly areas.

[0021] The aforementioned general-purpose power chassis for high-altitude obstacle-crossing agricultural machinery in hilly areas comprises a frame that is an integral structure, with the walking and steering wheel legs respectively located at the four corners of the frame. Each walking and steering wheel leg includes a walking wheel, a steering knuckle, a hydraulic motor, a steering cylinder, a boom, a forearm, and a swing arm. The boom, forearm, and swing arm together with the frame form a parallelogram structure, and the walking wheel is driven to vertically displace via a lifting cylinder to achieve terrain-adaptive obstacle crossing. The steering knuckle is connected to the swing arm, the hydraulic motor is integrated into the steering knuckle and drives the walking wheel to rotate, and the steering cylinder is connected to the steering knuckle and pushes the steering knuckle to rotate relative to the swing arm.

[0022] The aforementioned general-purpose power chassis for high-altitude obstacle-crossing agricultural machinery in hilly areas includes a first rotary encoder at the hinge point between the boom and the forearm, used to calculate the wheel leg height in real time through angle changes; and a second rotary encoder at the pin connecting the steering knuckle and the steering cylinder, used to detect the steering angle of each walking wheel.

[0023] The technical effects of this invention are as follows:

[0024] 1) The high obstacle-crossing general-purpose power chassis for hilly agricultural machinery of the present invention is suitable for complex terrains such as hills and mountains. Through the wheel-leg composite structure, the chassis can effectively overcome various terrain obstacles, improving the passability of hilly agricultural machinery and its balance and anti-tipping performance on steep slopes.

[0025] 2) This invention is an automatic leveling control method for wheel-leg all-terrain chassis with virtual control model. It is an adaptive force tracking control method that does not require complex inverse kinematics and inverse dynamics models. It only needs to construct a virtual spring damping component at the center of mass of the base to generate the virtual force and torque required for control, which significantly reduces the complexity of the algorithm.

[0026] 3) In response to the various complex terrains that agricultural machinery may encounter during travel, the optimized distribution of contact force at the end of the outriggers effectively avoids problems such as outriggers lifting off the ground or chassis diagonal swaying. At the same time, it can significantly reduce the sudden peak values ​​of pitch angle, roll angle and height, thereby improving chassis stability and adaptability.

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a universal power chassis structure for high-altitude obstacle-crossing agricultural machinery in hilly terrain according to an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of a frame structure according to an embodiment of the present invention;

[0030] Figure 3This is a schematic diagram of the walking steering wheel leg structure according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of a power mechanism according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of an electronic control system according to an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram illustrating the automatic leveling control principle of a wheel-leg all-terrain chassis according to an embodiment of the present invention.

[0034] Figure 7 This is a schematic diagram of an adaptive force tracking control principle based on a virtual control model according to an embodiment of the present invention.

[0035] Among them, the attached figures are labeled

[0036] 1 rack

[0037] 11 Hydraulic oil tank

[0038] 12 Power Battery Installation Section

[0039] 13-wheel leg steering hinge shaft

[0040] 14 Installation Interface

[0041] 2. Walking and steering wheel legs

[0042] 21. Walking wheels

[0043] 22 Hydraulic motor

[0044] 23 Steering knuckle

[0045] 24 Steering cylinder

[0046] 25 swing arm

[0047] 26 Upper arm

[0048] 27 forearms

[0049] 28 First Rotary Encoder

[0050] 29 Second Rotary Encoder

[0051] 3. Power mechanism

[0052] 31 motor

[0053] 32 Shock Absorbing Pads

[0054] 33 stents

[0055] 34 Hydraulic piston pump

[0056] 35 Load-sensitive pump

[0057] 4. Hydraulic System

[0058] 5. Electrical Control System

[0059] 51 batteries

[0060] 52 Vehicle Controller

[0061] 53 Motor Driver Detailed Implementation

[0062] The structural and working principles of the present invention will be described in detail below with reference to the accompanying drawings:

[0063] See Figure 1 , Figure 1 This is a schematic diagram of a universal power chassis structure for high-obstacle-crossing hilly agricultural machinery according to an embodiment of the present invention. Hilly and mountainous areas are characterized by complex topography, undulating terrain, and numerous gullies, necessitating an all-terrain chassis capable of automatically adjusting its posture according to the hilly terrain. The universal power chassis for high-obstacle-crossing hilly agricultural machinery of the present invention is suitable for enabling stable movement of agricultural machinery in complex terrains such as hills and mountains. It includes a frame 1 and, mounted on the frame 1, walking and steering wheel legs 2, a power mechanism 3, a hydraulic system 4, and an electronic control system 5. The electronic control system 5 is connected to the walking and steering wheel legs 2, the power mechanism 3, and the hydraulic system 4. The electronic control system 5 controls the raising and lowering of the walking and steering wheel legs 2 to achieve climbing and obstacle crossing, and employs an automatic leveling control method for the universal power chassis to automatically adjust the chassis posture in complex terrains, adapting to the operational needs of hilly areas.

[0064] See Figure 2 , Figure 2 This is a schematic diagram of the frame 1 according to an embodiment of the present invention. In this embodiment, the frame 1 is preferably an integrated structure as the core load-bearing structure. The frame 1 integrates the wheel leg steering hinge shaft 13 and the mounting interface 14 for key components such as the power mechanism 3, hydraulic system 4 and electronic control system 5. The front end of the frame 1 is a sealed hydraulic oil tank 11, and the rear end is reserved with a semi-enclosed space as a power battery mounting part 12. The four independent walking steering wheel legs 2 are respectively set at the four corners of the frame 1 and pivotally connected to the frame 1 to realize omnidirectional movement of the chassis and integrate the lifting mechanism. The power mechanism 3 is centrally arranged on the upper platform of the frame 1, and the hydraulic system 4 and electronic control system 5 are distributed around the power mechanism 3. They are connected to the remote control terminal through a wireless communication module to realize integrated control of chassis movement, steering and lifting actions.

[0065] See Figure 3 , Figure 3This is a schematic diagram of the walking steering wheel leg 2 according to an embodiment of the present invention. The walking steering wheel leg 2 of this embodiment includes a walking wheel 21, a steering knuckle 23, a hydraulic motor 22, a steering cylinder 24, a boom 26, a forearm 27, and a rotating arm 25. The boom 26, forearm 27, and rotating arm 25, together with the frame 1, form a parallelogram structure. The walking wheel 21 is driven to vertically displace via a lifting cylinder to achieve terrain-adaptive obstacle crossing. The steering knuckle 23 is connected to the rotating arm 25. The hydraulic motor 22 is integrated into the steering knuckle 23 and drives the walking wheel 21 to rotate. The steering cylinder 24 is connected to the steering knuckle 23 and pushes the steering knuckle 23 to rotate relative to the rotating arm 25. In this embodiment, a dual-sensor system is installed at key locations. A first rotary encoder 28 is installed at the hinge point between the swing arm 25 and the forearm 27 to calculate the wheel leg height in real time based on angle changes. A second rotary encoder 29 is installed at the pin connecting the steering knuckle 23 and the steering cylinder 24 to accurately detect the deflection angle of each traveling wheel 21. Based on this feedback, the vehicle controller 52 can coordinate the steering angle of each wheel, and through its coordination with the steering cylinders 24 on the four wheel legs, achieve vehicle steering. This embodiment adopts a modular structure for power transmission and steering execution of the power chassis. A steering knuckle 23 is connected to the other end of the swing arm 25, and a hydraulic motor 22 is integrated on it to drive the traveling wheels 21 to rotate. Simultaneously, the steering cylinders 24 push the steering knuckle 23 to rotate relative to the swing arm 25. Based on the feedback data from the first rotary encoder 28 and the second rotary encoder 29, the lifting cylinders of the four wheel legs are coordinated to achieve terrain-adaptive obstacle crossing.

[0066] See Figure 4 , Figure 4 This is a schematic diagram of the power mechanism 3 according to an embodiment of the present invention. The power mechanism 3 in this embodiment includes a motor 31, a hydraulic piston pump 34, and a load-sensitive pump 35, which are connected in series. The motor 31 and the hydraulic piston pump 34 are fixed together by a bracket 33 and connected by a flexible coupling to transmit power. A shock-absorbing pad 32 is provided at the bottom of the bracket 33, and the bracket is fixed to the frame 1 via the shock-absorbing pad 32. The hydraulic system 4 adopts a modular valve group structure, including various functional valve groups and pipelines. Through multi-way control valves, the hydraulic oil flow direction is precisely adjusted to drive the actuator to complete the switching of the vehicle's travel direction, the deflection of the steering cylinder 24, and the extension and retraction of the lifting cylinder. In addition, the hydraulic system 4 also includes an air cooler, which can integrate a forced air cooling unit to actively control the temperature of the hydraulic medium in the closed-loop circulation to ensure that the oil temperature remains stable within the allowable range under operating conditions.

[0067] See Figure 5 , Figure 5This is a schematic diagram of an electronic control system 5 according to an embodiment of the present invention. The electrical control system of this embodiment can control the lifting and lowering of the chassis wheel legs to achieve climbing and obstacle crossing. It includes a battery 51, a motor driver 53, a vehicle controller 52, a panel, a remote control box, etc. The battery 51 provides power to the vehicle. The vehicle controller 52 (ECU) is connected to various sensors, valve group electromagnets, and motor driver 53 of the chassis via CAN communication, and outputs commands to each actuator via a remote control.

[0068] See Figure 6 and Figure 7 , Figure 6 This is a schematic diagram illustrating the automatic leveling control principle of a wheel-leg all-terrain chassis according to an embodiment of the present invention. Figure 7 This is a schematic diagram of an adaptive force tracking control principle based on a virtual control model according to an embodiment of the present invention. The automatic leveling control method for a general-purpose agricultural machinery chassis of the present invention is applicable to the automatic leveling of the attitude of wheel-leg type all-terrain chassis. It achieves automatic adjustment of the chassis attitude in complex terrain through a virtual control model, ensuring that the chassis attitude remains stable throughout the journey. The method includes the following steps:

[0069] A virtual control model for a wheel-leg all-terrain chassis is constructed. By describing the chassis attitude and the attitude of the control base, a virtual control model under the base coordinate system {B} is established. At the same time, virtual forces are allocated so that the virtual forces are converted into contact forces between each drive leg and the environment. In order for the wheel-leg all-terrain chassis to be able to automatically level, the contact forces need to be mapped to the torques in the joint space using the Jacobian matrix.

[0070] Adaptive force tracking control is implemented based on the virtual control model of this wheel-leg all-terrain chassis. System uncertainties are compensated by suppressing disturbances and minimizing force tracking errors, i.e., by dynamically adjusting control parameters. To achieve adaptive control and suppress system disturbances, and to optimize impedance characteristics in real time through error feedback, minimizing force tracking error and compensating for system uncertainties; and

[0071] Attitude guidance control is performed based on the virtual control model of the wheel-leg all-terrain chassis. The actual roll angle, pitch angle, and yaw angle of the base are acquired in real time through the inertial measurement unit and compared with the preset horizontal attitude to calculate the attitude deviation. Then, the virtual force and torque of the all-terrain chassis base are calculated and distributed to the four support legs, which are converted into the contact force between the end of the support legs and the ground. According to the calculated attitude deviation and contact force, the wheels of the drive chassis are controlled to adjust the chassis attitude to maintain chassis stability.

[0072] In the adaptive force tracking control step, a second-order dynamic equation for the force error is established based on the mass matrix, damping matrix, and stiffness matrix, and a time-varying coefficient is introduced. and auxiliary functions An error equation containing time-varying parameters is constructed, and the impedance parameters are dynamically adjusted to compensate for system uncertainties.

[0073] This embodiment also includes verifying the stability of the closed-loop system using the Lyapunov energy function to ensure the convergence of force tracking error.

[0074] In this embodiment, a 6-DOF virtual joint is established between the world coordinate system {W} and the chassis base coordinate system {B}. The pose transformation of the base coordinate system is parameterized through this virtual joint, and the system pose is described by coupling the outrigger joint coordinates. The virtual control model of the wheel-leg all-terrain chassis is as follows:

[0075] ;

[0076] in, The RPY angle of the base coordinate system {B} relative to the world coordinate system {W}, including the roll angle. Pitch angle and deflection angle ; Let {B} be the position vector of the origin of the base coordinate system {B} in the world coordinate system {W}; These are the joint coordinates of the chassis outriggers.

[0077] In the attitude guidance control steps of this embodiment, virtual components are constructed in the three-dimensional movement and three-dimensional rotation directions of the base for attitude guidance control. Forces and torques are simulated using virtual springs and damping components. The required virtual forces and torques are calculated based on the desired attitude, angle, and angular velocity, as well as the actual attitude, angle, and angular velocity during movement. The virtual forces are then distributed to the contact forces at the ends of each outrigger, driving the chassis to automatically level itself. The virtual forces and virtual torques acting on the chassis center of gravity are as follows:

[0078] ;

[0079] ;

[0080] ;

[0081] in, It is the virtual force generated by the virtual component on the Z-axis. and These are the virtual moments at the roll and pitch angles, respectively. The elastic coefficient, Let h be the damping coefficient, and h be the real-time height corresponding to the Z-axis coordinate, and its derivative be... The rate of change of chassis height. and These are the angles and velocities of the roll and pitch angles, respectively, fed back by the sensors. dThe desired height is the center of mass of the chassis base, with the subscript d indicating the desired value.

[0082] Among these, the desired fuselage position is determined based on the terrain. and posture and its expected speed and attitude angular velocity The actual position z and attitude angle of the chassis during movement are combined with feedback. ,speed and attitude angular velocity Calculate the virtual forces on the all-terrain chassis base. and torque The virtual force and torque of the chassis base are then distributed to each support leg, which is converted into the contact force between the end of the support leg and the ground, so as to achieve the desired motion control of the base and the automatic leveling of the chassis.

[0083] In one embodiment of the present invention, the wheel-legged all-terrain chassis is a multi-rigid-body floating base system, whose topological configuration is similar to that of a quadruped robot. The automatic leveling control method of this agricultural machinery general-purpose power chassis includes:

[0084] Step S100: Construct a virtual control model for a wheel-legged all-terrain chassis:

[0085] Since the chassis base coordinate system {B} floats relative to the world coordinate system {W}, relying solely on the 12 joint coordinates of the four outriggers in the chassis is insufficient to fully characterize the system's global pose. Therefore, a 6-DOF virtual joint is established between {W} and {B}. This virtual joint is used to parameterize the pose transformation of the base coordinate system, and coupled with the outrigger joint coordinates, a complete description of the system's pose is achieved, as shown below:

[0086] ;

[0087] in, The RPY angle of the base coordinate system {B} relative to the world coordinate system {W}, including the roll angle. Pitch angle and deflection angle , for:

[0088] ;

[0089] in, Let be the rotation angle about the X-axis. Let be the rotation angle about the Y-axis. The rotation angle is about the Z-axis;

[0090] Let {B} be the position vector of the origin of the base coordinate system {B} in the world coordinate system {W}.

[0091] ;

[0092] Coordinates of the 12 joints of the chassis outriggers:

[0093]

[0094] The 18-dimensional generalized coordinate vector can represent the chassis posture of the general-purpose power chassis for high-altitude obstacle-crossing and hilly agricultural machinery in detail. At the same time, based on the feedback data from the sensors, the virtual force at the center of mass of the agricultural machinery chassis is calculated. The virtual force and torque at the center of mass of the base are distributed to the four outriggers and transformed into the contact force between the outrigger ends and the ground. Then, the contact force is mapped to the joint torque through the Jacobian matrix to drive the joint movement, thereby constructing a virtual control model for the wheel-leg all-terrain chassis.

[0095] Step S200: Adaptive force tracking control based on a virtual control model:

[0096] Virtual control models for wheel-mounted all-terrain chassis operating on rugged terrain, such as... Figure 7 As shown, based on the obtained environmental perception data and terrain height change data, adaptive control suppresses system disturbances, tracks the desired force, and integrates force tracking error compensation and terrain pre-adjustment to output control and convert wheel position commands to drive chassis leveling, minimizing force tracking error and ensuring chassis stability on rough terrain. The differential equation for the tracking error can be expressed as:

[0097] ;

[0098] Among them, force error For reference With environmental forces The difference, Let these represent the mass matrix, damping matrix, and stiffness matrix of the desired impedance model, respectively. The additional stiffness gain introduced for adaptive control is used to dynamically adjust the system response, and its derivative is... These represent velocity and acceleration, respectively.

[0099] Therefore, the second-order dynamic expression based on the mass-stiffness-damped system is:

[0100] ;

[0101] In the formula, and These are the reference position and the current position, respectively. The control expression for this adaptive tracking control method can then be calculated as follows:

[0102] ;

[0103] in, For Expectation With actual force The error between them Auxiliary function representing changes over time. , is the time-varying coefficient.

[0104] Combining the above expressions, we obtain the following equation:

[0105] ;

[0106] Among them, the definition , , Define the variation parameters of the force error equation above; The above error function can be further simplified, and the simplified mathematical expression is as follows:

[0107] ;

[0108] Similarly, and Here is the parameter matrix of the state equation. Used to describe the time-varying characteristics of error dynamics. This equation characterizes external disturbances. It transforms the nonlinear error equation into a state-space form, making it easier to analyze and control the stability of wheel-leg chassis.

[0109] To clearly describe the force tracking state, let As the state vector of the total error state equation, the new error state vector equation of the reference model of the total error state equation and the actual force error model of the system can be expressed as:

[0110] ;

[0111] To ensure the stability of the closed-loop adaptive system in the Lyapunov sense, the adaptive control can be:

[0112] ;

[0113] in, These are variable parameters, typically combining position error and velocity feedback; This is a correction factor to prevent excessive parameter drift; For adaptive gain, it is usually taken as a positive integer and is used to control the parameter update rate.

[0114] To verify the stability of the chassis adaptive system, a Lyapunov energy function was established. and its derivative as follows:

[0115] ;

[0116] ;

[0117] in, , The value of is positive, because and All are positive numbers, and calculations can yield... That is, the derivative of the energy function satisfies the requirement, and the system remains stable.

[0118] By dynamically adjusting control parameters This allows the system to maintain stability and tracking performance even under unknown disturbances. Unlike traditional control methods that focus on adjusting impedance parameters, this embodiment optimizes impedance characteristics in real time through error feedback.

[0119] Step S300: Attitude guidance control based on virtual control model:

[0120] To address the motion requirements of automatic chassis leveling, a virtual control model method is used to construct virtual components in the three-dimensional movement and rotation directions of the base for attitude guidance control. A virtual component connected to the environment is constructed vertically at the base's center of mass, generating a virtual force in the vertical direction. This ensures the chassis base maintains a desired position in the vertical height without significant deviation, thereby improving chassis stability. The mathematical representation of this virtual force is as follows:

[0121] ;

[0122] in, It is the virtual force generated by the virtual component on the Z-axis. The elastic coefficient, Let h be the damping coefficient, and h be the real-time height corresponding to the Z-axis coordinate, and its derivative be... The rate of change of chassis height. The desired height is the center of mass of the chassis base, with the subscript d indicating the desired value.

[0123] To overcome the roll and pitch angles caused by various unstable terrains encountered by agricultural machinery chassis during travel, virtual components are constructed in the roll and pitch directions of the chassis base to generate virtual torques, thereby controlling the roll and pitch angles of the chassis base and ensuring the stability of the chassis.

[0124] Furthermore, during chassis movement, based on motion control requirements, the pitch and roll angles of the base must always remain horizontal, meaning it is desirable for both the roll and pitch angles to remain constant at 0°. Therefore, the control methods for the base in the pitch and roll directions can be obtained as follows:

[0125] ;

[0126] ;

[0127] in, and These are the virtual moments at the roll angle and pitch angle, respectively. and These are the angles and velocities of the roll and pitch angles, respectively, fed back by the sensors. The elastic coefficient, d represents the damping coefficient, and the subscript d represents the expected value.

[0128] In this attitude guidance control based on a virtual control model, the all-terrain chassis needs to determine the desired fuselage position according to the terrain. and posture and its expected speed and attitude angular velocity Simultaneously, it combines the actual position z and attitude angle fed back by the chassis during movement. and its actual speed and attitude angular velocity Based on the virtual control model, the virtual forces and moments of the all-terrain chassis base are calculated. The virtual force and torque of the chassis base are then distributed to the four support legs, which are converted into contact force between the end of the support legs and the ground, thereby realizing the desired motion control of the base and automatic leveling of the chassis.

[0129] This invention uses a virtual control model to achieve automatic attitude adjustment of the chassis in uneven and complex terrain. It enables the chassis to automatically adjust its base attitude to adapt to uneven terrain during travel, ensuring that the chassis maintains a stable and level attitude at all times, thereby improving work efficiency and safety.

[0130] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. An automatic leveling control method for a general-purpose power chassis for agricultural machinery, applicable to the automatic leveling of the attitude of wheel-leg type all-terrain chassis, characterized in that, The chassis attitude is automatically adjusted in complex terrain using a virtual control model to maintain stability during travel. This includes the following steps: A virtual control model for a wheel-leg all-terrain chassis is constructed. By describing the chassis attitude and the attitude of the control base, a virtual control model under the base coordinate system {B} is established. At the same time, virtual forces are allocated so that the virtual forces are transformed into contact forces between each drive leg and the environment. The contact forces are then mapped to the torque in the joint space using the Jacobian matrix. Adaptive force tracking control is implemented by dynamically adjusting control parameters based on the virtual control model of this wheel-leg all-terrain chassis. Achieve adaptive control to suppress system disturbances, and optimize impedance characteristics in real time through error feedback to minimize force tracking error and compensate for system uncertainties; and Attitude guidance control is performed based on the virtual control model of the wheel-leg all-terrain chassis. The actual roll angle, pitch angle, and yaw angle of the base are acquired in real time through the inertial measurement unit and compared with the preset horizontal attitude to calculate the attitude deviation. The virtual force and torque of the all-terrain chassis base are calculated and distributed to each support leg, which is converted into the contact force between the end of the support leg and the ground. According to the calculated attitude deviation and contact force, the wheels of the drive chassis are controlled to adjust the chassis attitude to maintain chassis stability. In the attitude guidance control step, virtual components are constructed in the three-dimensional movement direction and three-dimensional rotation direction of the base to carry out attitude guidance control. Force and torque are simulated by virtual springs and damping components. The required virtual force and torque are calculated based on the desired attitude, angle and angular velocity and the actual attitude, angle and angular velocity during travel. The virtual force is then distributed to the contact force at the end of each outrigger to drive the chassis to automatically level. The virtual force and virtual torque acting on the chassis center of gravity are as follows: ； ； ； in, It is the virtual force generated by the virtual component on the Z-axis. and These are the virtual moments at the roll angle and pitch angle, respectively. The elastic coefficient, Let h be the damping coefficient, and h be the real-time height corresponding to the Z-axis coordinate, and its derivative be... The rate of change of chassis height. and These are the angles and velocities of the roll and pitch angles, respectively, fed back by the sensors. d The desired height is the center of mass of the chassis base, with the subscript d indicating the desired value.

2. The automatic leveling control method for the general-purpose power chassis of agricultural machinery according to claim 1, characterized in that, In the adaptive force tracking control step, a second-order dynamic equation for the force error is established based on the mass matrix, damping matrix, and stiffness matrix, and a time-varying coefficient is introduced. and auxiliary functions An error equation containing time-varying parameters is constructed, and the impedance parameters are dynamically adjusted to compensate for system uncertainties.

3. The automatic leveling control method for the general-purpose power chassis of agricultural machinery according to claim 2, characterized in that, It also includes verifying the stability of the closed-loop system using the Lyapunov energy function to ensure the convergence of force tracking error.

4. The automatic leveling control method for the general-purpose power chassis of agricultural machinery according to claim 1, characterized in that, A 6-DOF virtual joint is established between the world coordinate system {W} and the chassis base coordinate system {B}. The pose transformation of the base coordinate system is parametrically transformed through this virtual joint, and the system pose is described by coupling the outrigger joint coordinates. The virtual control model of the wheel-leg all-terrain chassis is as follows: ； in, The RPY angle of the base coordinate system {B} relative to the world coordinate system {W}, including the roll angle. Pitch angle and deflection angle ; Let {B} be the position vector of the origin of the base coordinate system {B} in the world coordinate system {W}; These are the joint coordinates of the chassis outriggers.

5. The automatic leveling control method for the general-purpose power chassis of agricultural machinery according to claim 1, characterized in that, Determine the desired fuselage position based on the terrain. and posture and its expected speed and attitude angular velocity The actual position z and attitude angle of the chassis during movement are combined with feedback. ,speed and attitude angular velocity Calculate the virtual forces on the all-terrain chassis base. and torque The virtual force and torque of the chassis base are then distributed to each support leg, which is converted into the contact force between the end of the support leg and the ground, so as to achieve the desired motion control of the base and the automatic leveling of the chassis.

6. A general-purpose power chassis for agricultural machinery used in high-altitude obstacle-crossing hills, comprising a frame and traveling steering wheel legs, a power mechanism, a hydraulic system, and an electronic control system mounted on the frame, wherein the electronic control system is connected to the traveling steering wheel legs, the power mechanism, and the hydraulic system respectively, characterized in that, The electronic control system controls the raising and lowering of the walking steering wheel legs to achieve climbing and obstacle crossing, and adopts the automatic leveling control method of the agricultural machinery general power chassis as described in any one of claims 1-5 to achieve automatic adjustment of the chassis posture in complex terrain, so as to adapt to the operation needs of complex terrain in hilly areas.

7. The universal power chassis for high-altitude obstacle-crossing hilly agricultural machinery as described in claim 6, characterized in that, The frame is an integral structure, and the walking steering wheel legs are respectively located at the four corners of the frame. Each walking steering wheel leg includes a walking wheel, a steering knuckle, a hydraulic motor, a steering cylinder, a boom, a forearm, and a swing arm. The boom, forearm, and swing arm together with the frame form a parallelogram structure, and the walking wheel is driven to move vertically through a lifting cylinder to achieve terrain-adaptive obstacle crossing. The steering knuckle is connected to the swing arm, the hydraulic motor is integrated into the steering knuckle and drives the walking wheel to rotate, and the steering cylinder is connected to the steering knuckle and pushes the steering knuckle to rotate relative to the swing arm.

8. The universal power chassis for high-altitude obstacle-crossing hilly agricultural machinery as described in claim 7, characterized in that, A first rotary encoder is provided at the hinge point between the boom and the forearm to calculate the wheel leg height in real time by means of angle changes; a second rotary encoder is provided at the pin connecting the steering knuckle and the steering cylinder to detect the steering angle of each of the traveling wheels.

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