A six-wheel lunar rover motion control method and system based on a hierarchical control structure

Abstract

This invention discloses a motion control method for a six-wheeled lunar rover based on a hierarchical control structure. The method includes establishing a six-wheeled lunar rover model and a hierarchical control framework comprising a state reference layer, a torque decision layer, and a torque distribution layer. In the state reference layer, a two-degree-of-freedom single-track model is constructed to calculate the ideal yaw rate and center-of-gravity sideslip angle. In the torque decision layer, a double-power-law approach is designed to calculate the longitudinal velocity tracking error, yaw rate tracking error, and center-of-gravity sideslip angle tracking error; a sliding mode control method is used to calculate the generalized longitudinal force, lateral force, and yaw moment. In the torque distribution layer, an objective function is constructed based on the optimal control principle, and the torque distribution for the six wheels is optimized under the constraints of minimizing tire load rate and total motor energy consumption. This invention achieves motion stability control and collaborative optimization through a hierarchical control architecture, a sliding mode variable structure algorithm, and dynamic torque optimization distribution, providing an effective solution for torque control strategies in lunar exploration missions.

Description

Technical Field

[0001] This invention belongs to the field of lunar rover control technology, specifically relating to a motion control method and system for a six-wheeled lunar rover based on a hierarchical control structure, which is particularly suitable for lateral stability control and longitudinal motion co-optimization under complex lunar surface terrain. Background Technology

[0002] Lunar rovers face multiple challenges during lunar exploration missions, including soft soil, rugged terrain, and low-gravity environments. Their motion stability and energy efficiency directly impact mission success. Current lunar rover control methods typically employ a centralized control architecture, which suffers from the following problems: High model complexity: Traditional multi-degree-of-freedom dynamic models involve large computational loads, poor real-time performance, and difficulty adapting to dynamic conditions; Insufficient stability: Single control strategies struggle to balance yaw stability and longitudinal motion tracking accuracy, especially prone to instability during turns or climbs; Uneven torque distribution: Static distribution methods fail to consider tire adhesion limits and motor dynamic characteristics, leading to localized slippage or excessive energy consumption; Poor economy: Lack of coordinated optimization of stability and energy consumption results in underutilization of motor efficiency.

[0003] To address the aforementioned issues, this invention proposes a hierarchical control architecture that combines sliding mode variable structure algorithm with dynamic torque optimization allocation to achieve coordinated control of lateral stability and longitudinal motion, while simultaneously reducing energy consumption. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a motion control method and system for a six-wheeled lunar rover based on a hierarchical control structure. By combining a sliding mode variable structure algorithm with dynamic torque optimization allocation, it achieves coordinated control of lateral stability and longitudinal motion while reducing energy consumption.

[0005] To achieve the above objectives, this invention provides a motion control method for a six-wheeled lunar rover based on a hierarchical control structure. The control method includes: Build a six-wheeled lunar rover model; Establish a hierarchical control structure, which includes a state reference layer, a torque decision layer, and a torque distribution layer. In the state reference layer, a linear two-degree-of-freedom single-track model for front and rear axle steering is established to calculate the ideal yaw rate and ideal centroid sideslip angle of the six-wheeled lunar rover. The linear two-degree-of-freedom single-track model has the degree of freedom for lateral motion and the degree of freedom for yaw motion. In the torque decision layer, based on the ideal yaw rate and ideal centroid sideslip angle, and combined with the ideal longitudinal rate set in the six-wheeled lunar rover model, a double power-law approach is designed to calculate the longitudinal rate tracking error, yaw rate tracking error, and centroid sideslip angle tracking error of the six-wheeled lunar rover. The generalized longitudinal force, lateral force, and yaw moment of the six-wheeled lunar rover are calculated using the sliding mode control method to design the torque decision layer. In the torque distribution layer, an objective function is constructed based on the generalized longitudinal force, lateral force, yaw moment, and optimal control principle. Constraints are set according to the ground conditions and motor characteristics. The control objectives are to minimize the tire load rate of the six-wheeled lunar rover and the total energy consumption of the six-wheeled lunar rover's motors. Dynamic optimization of torque distribution for the six wheels is carried out in the torque distribution layer.

[0006] In some embodiments, the six-wheeled lunar rover model is a 22-DOF dual-track vehicle dynamics model. The 22 degrees of freedom include longitudinal, lateral, vertical, roll about the longitudinal axis of the vehicle coordinate system, pitch about the lateral axis of the vehicle coordinate system, yaw about the vertical axis of the vehicle coordinate system, rotation and vertical sway of the six wheels about the axis, and steering of the four wheels of the front and rear axles.

[0007] In some embodiments, during the calculation of the ideal yaw rate and the center-of-mass eccentricity angle, according to Newton's second law, the differential equation of lateral motion for the six-wheeled lunar rover is: ; In the formula, For the six-wheeled lunar rover's curb weight, , These represent the longitudinal velocity and the lateral velocity of the six-wheeled lunar rover, respectively. This indicates that the derivative with respect to the lateral velocity is taken. The yaw rate of the six-wheeled lunar rover. , These represent the steering angles of the first and third axle wheels of the six-wheeled lunar rover, respectively. , , These represent the lateral forces on the first axle wheel, the second axle wheel, and the third axle wheel of the six-wheeled lunar rover, respectively. According to Euler's second law, the differential equation for the yaw motion of the six-wheeled lunar rover is: ; In the formula, Let be the moment of inertia of the six-wheeled lunar rover body about the vertical axis of the body coordinate system. This indicates the derivative of the yaw rate. , These represent the distances from the center of mass of the six-wheeled lunar rover to the first axis and the third axis, respectively.

[0008] In some embodiments, the design torque decision layer includes: Reconstruct the differential equations of motion for the six-wheeled lunar rover in the longitudinal, lateral, and yaw directions at the torque decision level: ; ; ; In the formula, This indicates taking the derivative with respect to the longitudinal velocity. and These represent the lateral forces on the left and right wheels of the i-th axis of the six-wheeled lunar rover, respectively. and These are the steering angles of the left and right wheels of the i-th axis of the six-wheeled lunar rover, respectively. To control the generalized longitudinal force of the six-wheeled lunar rover in its longitudinal motion, To control the generalized lateral force of the six-wheeled lunar rover during lateral motion, The generalized yaw moment for controlling the six-wheeled lunar rover's yaw motion; Based on the design double power-law approach, the longitudinal velocity tracking error, yaw rate tracking error, and center of mass sideslip angle tracking error are calculated. The longitudinal velocity is controlled by the generalized longitudinal force, and the longitudinal velocity tracking error is calculated using the switching function formula: ; In the formula, The tracking error is for the longitudinal velocity of the six-wheeled lunar rover. This refers to the ideal longitudinal speed of a six-wheeled lunar rover, or in other words, the target speed of a six-wheeled lunar rover. Differentiate the above equation and combine it with the longitudinal motion differential equation of the six-wheeled lunar rover shown: ; Introducing the double-power reaching law with a saturation function, the formula is: ; In the formula, , , , For the design parameters in the double power-law approaching law, Let represent the saturation function in the double power reaching law. The formula for the saturation function in the double power reaching law is: ; In the formula, The boundary layer thickness is set in the saturation function; According to the double power-law of the saturation function, the generalized longitudinal force Represented as: ; In the formula, , , , For the design parameters in the double power-law approaching law, This represents the saturation function in the double power approach law; The generalized lateral force and the generalized yaw moment are expressed as follows: ; ; In the formula, The tracking error of the centroid sideslip angle of the six-wheeled lunar rover. This represents the tracking error of the yaw rate of the six-wheeled lunar rover.

[0009] In some embodiments, in the torque distribution layer, the generalized longitudinal force, generalized lateral force, and generalized yaw moment are used as the control targets of the torque distribution layer in the six-wheeled lunar rover torque distribution and stability control method: ; In the formula, The target control force required for a six-wheeled lunar rover to track the motion of a target; Force analysis of the six-wheeled lunar rover: ; In the formula, For target control , For the longitudinal force of the tire, The coefficient matrix is ​​given by the following formula: ; ; ; In the formula, , , They are represented as follows: ; ; .

[0010] In some embodiments, the longitudinal force of the tires is constrained by the tire adhesion limit and the motor output limit of the six-wheeled lunar rover. The tire adhesion limit constraint is as follows: ; In the formula, The equivalent adhesion coefficient on the lunar surface; The motor output limit constraint is given by the following formula: ; In the formula, This is the maximum output torque of the motor. The radius of the six-wheeled lunar rover's wheels; Combining the tire adhesion limit constraint and the motor output limit constraint, the constraint condition for the tire longitudinal force is expressed as: ; In the formula, , These are the lower and upper limits of the tire's longitudinal force, respectively: ; ; Based on the constraint of the longitudinal force of the tires, an objective function is established within the constraint range. By approximating the objective function, the optimal solution for controlling the longitudinal force of the tires is obtained. In order to achieve coordinated control allocation for the stability and economy of the six-wheeled lunar rover, the objective functions are established separately, taking into account the approximation error and the motor drive efficiency. by square representation of norm right The approximation error, and with The objective function for minimizing the error is as follows: ; In the formula, Let be the sign of the objective function for approximation error. The variable represents the value that minimizes the objective function of the approximation error. These are the weighting coefficients. It is a weighted matrix that takes into account tire utilization. and The formulas are as follows: ; ; In the formula, , , These are the weighting coefficients for the generalized longitudinal force, generalized lateral force, and generalized yaw moment, respectively. , , , , , This indicates the wheel load coefficients of the front left, front right, middle left, middle right, rear left, and rear right wheels of the lunar rover; After optimization calculations, the longitudinal force of each wheel after stability optimization was obtained. The final torque optimization distribution result of each wheel drive motor is expressed as follows: ; In the formula, This represents the optimal torque distribution result for each hub motor. The longitudinal force of each wheel after stability optimization; With the goal of maximizing motor energy efficiency, the overall efficiency of the drive motors for the six wheels of the lunar rover is expressed as follows: ; In the formula, The total torque required for the six-wheeled lunar rover. , , , , , This indicates the drive torque of the hub motors in the front left, front right, center left, center right, rear left, and rear right wheels of the six-wheeled lunar rover. , , , , , This indicates the rotational speeds of the front left, front right, middle left, middle right, rear left, and rear right wheels of the six-wheeled lunar rover. , , , , , This indicates the drive efficiency of the hub motors in the front left, front right, middle left, middle right, rear left, and rear right wheels of the six-wheeled lunar rover. To maximize the overall efficiency of the motor while minimizing the objective function value, the objective function for motor drive efficiency is defined as follows: ; After optimization calculations, the longitudinal force of each wheel after economic optimization was obtained. The final torque optimization distribution result of each wheel drive motor is expressed as follows: ; In the formula, This represents the optimal torque distribution result for each hub motor. The longitudinal force of each wheel after economic optimization.

[0011] In some embodiments, based on the approximation error objective function and the motor drive efficiency objective function, and according to the control objective of improving energy efficiency while ensuring sufficient driving stability of the six-wheeled lunar rover, a torque distribution coordination control module is designed. This module includes a judgment module and a switching module. In the judgment module, an adhesion margin threshold coefficient is introduced to mark whether the tire force meets the power requirements. The formula is: ; In the formula, Indicates the margin threshold coefficient; Based on the judgment module, the torque stability threshold is defined by the following formula: ; In the formula, Indicates correspondence The torque stability threshold; After optimal stability control allocation, the torque allocated to each drive motor and the torque stability threshold of each wheel are obtained. The switching module is used to design coordinated control of driving stability and energy economy. If the torque allocated to each drive motor is less than or equal to the torque stability threshold of each wheel, the driving environment of the six-wheeled lunar rover is considered sufficiently ideal to fully meet the vehicle stability requirements. Then, economic optimization is performed, and the optimal economic control allocation is obtained based on the aforementioned calculation method. The output is the given torque for each wheel drive motor, and the formula is: ; If the torque of a drive motor exceeds the torque stability threshold, the torque distribution layer considers stability optimization and directly outputs the torque of the drive motor as the given torque for each wheel drive motor. The formula is as follows: .

[0012] In some embodiments, a switching parameter is introduced to achieve the switching of different target controls in the form of a weighted summation. The weighting function is expressed as: ; In the formula, To switch parameters; Define intermediate variables: ; ; Switch parameters Represented as: ; Based on the coordinated control and allocation method of lunar rover stability and energy consumption economy, the dynamic optimization allocation result of the torque of the six-wheeled lunar rover is obtained through quadratic programming.

[0013] Some embodiments of this application also provide a lunar rover motion control system, including a controller and a six-wheeled lunar rover. The controller is communicatively connected to the six-wheeled lunar rover and is configured to execute the control method described in any of the above embodiments. A six-wheeled lunar rover model is used to perform scenario verification on the controller.

[0014] Some embodiments of this application also provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the program to implement the steps of the control method described in any of the above embodiments.

[0015] Some embodiments of this application specifically relate to a motion control method and system for a six-wheeled lunar rover based on a hierarchical control structure. By designing a hierarchical architecture with a state reference layer (model simplification), a torque decision layer (sliding mode control), and a torque distribution layer (dynamic optimization), the computational complexity is reduced and real-time performance is improved. By combining a sliding mode control algorithm with saturation functions, chattering is significantly reduced, and tracking accuracy and robustness are improved. By dynamically coordinating allocation based on tire adhesion margin thresholds and motor efficiency curves, smooth switching control between stability and energy consumption is achieved. A 22-DOF six-wheeled lunar rover dynamic model is set up to accurately describe the rover's vertical sway and pitch / roll coupling effects, providing a high-fidelity simulation environment for control. Attached Figure Description

[0016] Figure 1 This is a flowchart of a motion control method for a six-wheeled lunar rover based on a hierarchical control structure, provided in some embodiments of this application. Figure 2 For based on Figure 1 The diagram shows a dynamic model of a six-wheeled lunar rover provided by a motion control method based on a hierarchical control structure. Figure 3 For based on Figure 1 The diagram shows a two-degree-of-freedom monorail model provided by a motion control method for a six-wheeled lunar rover based on a hierarchical control structure. Figure 4 For based on Figure 1 The diagram shows a saturation function in sliding mode control provided by a motion control method for a six-wheeled lunar rover based on a hierarchical control structure. Figure 5 This is a schematic diagram of an electronic device in some embodiments of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," etc., indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product of the invention is in use. They are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0018] like Figure 1 As shown, this invention provides a motion control method for a six-wheeled lunar rover based on a hierarchical control structure. The control method includes: S1. Establish a six-wheeled lunar rover model. In some embodiments, such as... Figure 2 As shown, the six-wheeled lunar rover model can be a 22-DOF dual-track vehicle dynamics model. The 22 degrees of freedom can include the vehicle's longitudinal, lateral, and vertical directions; roll around the x-axis of the vehicle's coordinate system; pitch around the y-axis of the vehicle's coordinate system; yaw around the z-axis of the vehicle's coordinate system; rotation and vertical sway of the six wheels around their axes; and steering of the four wheels on the front and rear axles. It is understandable that, as... Figure 2 As shown in the embodiments of this application, the vehicle's longitudinal direction can be parallel to the X-axis, the vehicle's lateral direction can be parallel to the Y-axis, and the vehicle's vertical direction can be parallel to the Z-axis. Wherein, as... Figure 2 As shown in this embodiment, the portion further forward along the direction of travel of the six-wheeled lunar rover is defined as the front section. The front axle of the six-wheeled lunar rover is located at the front of the rover and serves as its steering axle. It is connected to the steering system via a steering knuckle to control the direction of travel by turning the wheels. The front axle not only bears the weight of the front of the six-wheeled lunar rover but also withstands longitudinal forces, lateral forces, and related torques. The rear axle of the six-wheeled lunar rover is located at the rear of the vehicle and primarily undertakes power transmission and load-bearing tasks. The rear axle transmits engine torque to the left and right wheels through a differential, half-shafts, etc., ensuring consistent wheel speeds during straight-line travel and automatically adjusting the inner and outer wheel speeds during cornering to reduce tire wear and power loss. The coordinated work of the front and rear axles ensures the stability and handling of the vehicle.

[0019] In addition, this application provides a six-wheeled lunar rover model, the specific body parameters of which can be referred to Table 1. In other embodiments, the specific body parameters can also be adapted, and this application does not limit them.

[0020] Table 1 Vehicle Body Parameters

[0021] S2. Establish a hierarchical control structure, which includes a state reference layer, a torque decision layer, and a torque distribution layer. In the state reference layer, establish a linear two-degree-of-freedom single-track model for front and rear axle steering. This can simplify the six-wheeled lunar rover model, retaining the degrees of freedom in the lateral and yaw motion directions of the six-wheeled lunar rover. Then, derive and calculate the state-space equations for the ideal yaw rate and the sideslip angle of the center of mass of the six-wheeled lunar rover.

[0022] Among them, the ideal yaw angle of a six-wheeled lunar rover refers to the yaw angle of the lunar rover around its longitudinal axis under ideal conditions (i.e., Figure 2 The angular velocity of the rotation along the Z-axis (as shown), and the sideslip angle of the six-wheeled lunar rover's center of mass are the angle between the vehicle's center of mass velocity direction and the vehicle's longitudinal axis (i.e., the angle between the vehicle's center of mass velocity direction and the longitudinal axis of the vehicle body). Figure 2 The angle between the Z-axis and the Z-axis (as shown) is a core parameter for evaluating vehicle dynamic stability and handling.

[0023] It is understandable that, such as Figure 3 The box 1 shown is a simplified representation of the first axis. In this embodiment, the first axis can also be understood as the front axis. Figure 3 Box 2 shown is a simplified representation of the second axis. Figure 3 The box 3 shown is a simplified representation of the third axis. In this embodiment, the third axis can also be understood as the rear axis.

[0024] Specifically, the state-space equations for calculating the ideal yaw rate and the sideslip angle are as follows: According to Newton's second law, the differential equation for the lateral motion of the lunar rover is: ; In the formula, For the six-wheeled lunar rover's curb weight, , These represent the longitudinal velocity and lateral velocity of the six-wheeled lunar rover, respectively. This indicates that the derivative with respect to the lateral velocity is taken. The yaw rate of the six-wheeled lunar rover. , These represent the steering angles of the first and third axle wheels of the six-wheeled lunar rover. , , This represents the lateral force of the first axle wheel, the lateral force of the second axle wheel, and the lateral force of the third axle wheel; According to Euler's second law, the differential equation for the yaw motion of the lunar rover is: ; In the formula, Let Z be the moment of inertia of the six-wheeled lunar rover body about the z-axis. This indicates the derivative of the yaw rate. , This indicates the distance from the lunar rover's center of mass to the first axis (front axis) and the third axis (rear axis); The six-wheeled lunar rover uses a front-to-rear axle steering mode. According to Ackermann's steering law, the geometric relationship between the steering angles of the front and rear axle wheels is as follows: ; Based on the assumption that the wheel steering angle remains very small during the steering process, that is Third axle wheel steering angle Steering angle of the first axle wheel The formula is as follows: ; In the formula, The formula for the wheel steering angle proportionality coefficient between the first and third axles is: ; Based on the assumption that the longitudinal speed of the six-wheeled lunar rover remains constant and the wheel steering angle is always very small during the turning process, the lunar rover's center of gravity sideslip angle... The speed can be measured by the lateral speed of the vehicle body. and longitudinal velocity The ratio is expressed by the formula: ; according to Figure 3 The geometric relationship in the figure, tire slip angle It can be represented as: ; ; ; Based on the assumption that the tire's lateral slip characteristics always remain in the linear region, the tire's lateral force can be expressed as: ; In the formula, Let be the lateral stiffness of the i-th axis, which is the sum of the lateral stiffnesses of the left and right wheels of the i-th axis. In this invention, the lateral stiffnesses of the six wheels of the lunar rover are equal, expressed as: ; In the formula, Let be the wheel lateral stiffness. Through the above formula derivation, the state-space equations of the linear two-degree-of-freedom monorail model can be obtained, expressed as: ; ; ; ; By solving the state-space equations, the ideal yaw rate of the six-wheeled lunar rover can be obtained. And the ideal centroid side slip angle .

[0025] S3. Establish a torque decision layer. In the torque decision layer, based on the ideal yaw rate and sideslip angle from step S2, and combined with the ideal longitudinal rate set in the vehicle model, design a double power-law approaching law to calculate the longitudinal velocity tracking error, yaw rate tracking error, and sideslip angle tracking error of the six-wheeled lunar rover. Use sliding mode control to calculate the generalized longitudinal force, lateral force, and yaw moment. Specifically: The torque decision layer is designed using a sliding mode control algorithm, and the motion of the six-wheeled lunar rover in the longitudinal, lateral, and yaw directions is reconstructed. The specific formulas are as follows: ; ; ; In the formula, This indicates taking the derivative with respect to the longitudinal velocity. and These represent the lateral forces on the left and right wheels of the i-th axis of the six-wheeled lunar rover, respectively. and These are the steering angles of the left and right wheels of the i-th axis of the lunar rover, respectively. To control the longitudinal resultant force of the lunar rover's longitudinal movement, To control the lateral resultant force of the lunar rover's lateral movement, Yaw moment for controlling the yaw motion of a vehicle; The design incorporates a double power-law approach to calculate the longitudinal velocity tracking error, yaw rate tracking error, and center of mass sideslip angle tracking error. A sliding mode control algorithm is also designed to calculate these errors. , and Taking longitudinal motion as an example: Longitudinal velocity It can be determined by generalized longitudinal force Control is achieved by using the longitudinal velocity tracking error as the switching function, as shown in the formula: ; In the formula, For the longitudinal velocity tracking error of the lunar rover, The ideal longitudinal speed for the lunar rover; Differentiating the above equation and combining it with the differential equation of the longitudinal motion of the six-wheeled lunar rover, we get: ; Chattering is a significant problem in sliding mode control. This invention improves upon the traditional power-law approach law by employing a double-power-law approach law to address the chattering issue. The double-power-law approach law with a saturation function is constructed as follows: ; In the formula, , , , For the design parameters in the double power-law approaching law, The saturation function in the double power reaching law, such as Figure 4 As shown, its formula is: ; In the formula, The boundary layer thickness is set in the saturation function. When the system is in the boundary layer, the saturation function makes it a continuous system, which can reduce chattering to a certain extent. According to the double power-law of the saturation function, the generalized longitudinal force It can be represented as: ; In the formula, , , , For the design parameters in the double power-law approaching law, This represents the saturation function in the double-power reaching law. The stability of sliding mode motion is verified by constructing a Lyapunov function, the formula of which is: ; The first derivative of the Lyapunov function is expressed as: ; In some embodiments, the first derivative of the Lyapunov function is always less than or equal to 0, and the sliding motion constructed in this invention has stability; The design of the double power-law approach law for calculating yaw rate tracking error and center of mass sideslip angle tracking error is similar to that for longitudinal velocity, and the generalized lateral force... and generalized yaw moment Represented as: ; .

[0026] In the formula, The tracking error of the centroid sideslip angle of the six-wheeled lunar rover. This represents the tracking error of the yaw rate of the six-wheeled lunar rover.

[0027] S4. Establish a torque distribution layer. In the torque distribution layer, construct an objective function based on the generalized longitudinal force (torque), lateral force, yaw moment and optimal control principle in step S3. Set constraints based on ground conditions and motor characteristics. With the minimization of tire load rate and total motor energy consumption as the control objectives, perform dynamic optimization distribution of torque for six wheels.

[0028] In step S3, the target control force (torque) required for the movement of the six-wheeled lunar rover was calculated. And the target control force (torque) The effect is achieved by tire force. Force analysis of the six-wheeled lunar rover shows that the target control force (torque) can be expressed as: ; In the formula, For target control force (torque) , For the longitudinal force of the tire, For the coefficient matrix, according to The assumption that it is small and considered constant when the sampling time is short. It can be viewed as a constant coefficient matrix, represented as: ; ; ; In the formula, , , They are represented as follows: ; ; ; In some embodiments, the wheels are independent of each other, and the number of unknowns is greater than the number of equations, making it impossible to directly calculate the longitudinal force of each tire using these equations. In this embodiment of the application, tire adhesion limit constraints and motor output limit constraints can be added, which are expressed as follows: (1) Tire adhesion limit constraints As can be seen from the establishment of the ground mechanics model, when the six-wheeled lunar rover travels on the lunar surface, the maximum adhesion force that the lunar surface can provide is related to the vertical load of each wheel. Therefore, the tire adhesion limit constraint condition is obtained as follows: ; In the formula, The equivalent adhesion coefficient on the lunar surface is taken as 0.5 in this study.

[0029] (2) Motor output limit constraints In the process of establishing the wheel model, the differential equation for wheel rolling is expressed as: ; In the formula, the rolling resistance torque It is the longitudinal force of the tire. The function is based on the assumption that the change in tire rotational angular velocity is ignored when the sampling time is small, i.e. Then the above equation can be transformed into: ; As can be seen from the above formula, the longitudinal force of the tire is determined by the output torque of the hub motor. The maximum torque that the hub motor can output can be obtained by looking up a table. Therefore, the motor output limit constraint of the longitudinal force of the tire is expressed as: ; In the formula, The maximum output torque of the motor is obtained by looking up a table based on the motor's external characteristic curve. The radius of the six-wheeled lunar rover's wheels.

[0030] Taking into account both tire adhesion limit constraints and motor output limit constraints, the final constraint condition for the tire longitudinal force is expressed as follows: ; In the formula, , These represent the lower and upper limits of the tire's longitudinal force, respectively, and the formula is: ; ; Based on the aforementioned tire longitudinal force constraint, an objective function needs to be established within the constraint range. The control input is then obtained by approximating the objective function. To achieve the optimal solution for the coordinated control allocation of the six-wheeled lunar rover's stability and economy, and considering both approximation error and motor drive efficiency, objective functions are established as follows: (1) Approximation error objective function by square representation of norm right The approximation error is calculated, and its minimum is taken as the objective. The formula is: ; In the formula, Let be the sign of the objective function for approximation error. The variable represents the value that minimizes the objective function of the approximation error. This is a weighting coefficient, used to adjust the target control force (torque). The weights of each element in the equation. It is a weighted matrix that considers tire utilization rate, and its function is to adjust the weight of the longitudinal force of each tire according to the utilization rate of each tire. and The formulas are as follows: ; ; In the formula, , , These are the weighting coefficients for the generalized longitudinal force, generalized lateral force, and generalized yaw moment, respectively. , , , , , This indicates the wheel load coefficients of the front left, front right, middle left, middle right, rear left, and rear right wheels of the lunar rover; After optimization calculations, the longitudinal force of each wheel after stability optimization was obtained. The final torque optimization distribution result of each wheel drive motor is expressed as follows: ; In the formula, This represents the optimal torque distribution result for each hub motor. The longitudinal force of each wheel after stability optimization.

[0031] (2) Objective function of motor drive efficiency With the goal of maximizing motor energy efficiency, the overall efficiency of the drive motors for the six wheels of the lunar rover is expressed as follows: ; In the formula, The total torque required for the six-wheeled lunar rover. , , , , , This indicates the drive torque of the hub motors in the front left, front right, center left, center right, rear left, and rear right wheels of the lunar rover. , , , , , This indicates the rotational speeds of the front left, front right, center left, center right, rear left, and rear right wheels of the lunar rover. , , , , , This indicates the drive efficiency of the hub motors in the front left, front right, middle left, middle right, rear left, and rear right wheels of the lunar rover. To maximize the overall efficiency of the motor while minimizing the objective function value, the objective function for motor drive efficiency is defined as follows: ; After optimization calculations, the longitudinal force of each wheel after economic optimization was obtained. The final torque optimization distribution result of each wheel drive motor is expressed as follows: ; In the formula, This represents the optimal torque distribution result for each hub motor. The longitudinal force of each wheel after economic optimization; Based on the approximation error objective function and the motor drive efficiency objective function, and according to the control objective of improving energy efficiency while ensuring the driving stability of the six-wheeled lunar rover, a torque distribution coordination control module is designed. This module includes a judgment module and a switching module, with an adhesion margin threshold coefficient introduced in the judgment module. This is used to mark the limit of whether the tire force meets the power requirements, and the formula is: ; Based on the judgment module, the torque stability threshold is defined by the following formula: ; In the formula, Indicates correspondence The torque stability threshold, Indicates the margin threshold coefficient; The switching module is used to design and coordinate the control of driving stability and energy economy, specifically: After optimal stability control allocation, the torque distributed to each drive motor is obtained. and the torque stability threshold of each wheel If the torque allocated to each drive motor is less than or equal to the torque stability threshold of each wheel, that is... If we believe that the current driving environment of the lunar rover is ideal enough to fully meet the vehicle stability requirements, then we will optimize the economy based on this.

[0032] If the torque of any drive motor is greater than the torque stability threshold of each wheel, that is... If the current situation does not fully meet the vehicle stability requirements, then the torque distribution layer should abandon economic optimization and only consider stability optimization, directly outputting... The formula for the given torque of each drive motor is: ; If economic optimization is performed, the result of the economically optimal control allocation can be obtained according to the aforementioned calculation method. The output is the given torque for each wheel drive motor, and the formula is: ; In some embodiments, when switching between multiple targets, if a "switch" structure of the switching module is used, the smoothness of control will deteriorate. In this embodiment, a switching parameter is introduced. The switching between different target controls is achieved through a weighted summation, and the weighting function is expressed as: ; In the formula, Define the switching parameters. and As an intermediate variable, switch parameters Represented as: ; Based on the aforementioned method for coordinated control and allocation of lunar rover stability and energy economy, the dynamic optimization allocation result of the six-wheel torque of the lunar rover is obtained through quadratic programming. .

[0033] In some embodiments of this application, a motion control method based on a hierarchical control structure design is used to achieve the division of labor and cooperation among the state reference layer (model simplification), torque decision layer (sliding mode control), and torque distribution layer (dynamic optimization), thereby reducing computational complexity and improving real-time performance. Furthermore, by using a sliding mode control algorithm based on a double power-law approach combined with a saturation function, chattering is significantly reduced, and tracking accuracy and robustness are improved. Dynamic coordination and allocation, based on tire adhesion margin thresholds and motor efficiency curves, achieves smooth switching control between stability and energy consumption. A 22-DOF six-wheeled lunar rover dynamic model is designed to accurately describe the rover's vertical sway and pitch / roll coupling effects, providing a high-fidelity simulation environment for control.

[0034] In some embodiments, this application also provides a lunar rover motion control system, including a controller. The controller is communicatively connected to a six-wheeled lunar rover model. The controller is configured to execute the six-wheeled lunar rover motion control method based on a hierarchical control structure described above. The six-wheeled lunar rover model can perform multi-scenario verification of the controller.

[0035] like Figure 5 As shown, in some embodiments, this application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the numerical simulation, analysis, or control steps in any of the methods described above.

[0036] At the hardware level, this electronic device includes a processor, internal bus, network interface, memory, and non-volatile storage, and may also include other hardware required for the business logic. The processor reads the corresponding computer program from the non-volatile storage into memory and then executes it to achieve the above-mentioned functions. Figure 1 The method described herein. Of course, besides software implementation, this specification does not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. That is to say, the execution entity of the following processing flow is not limited to individual logic units, but can also be hardware or logic devices. It is understood that by simply performing some logic programming on the method flow using a hardware description language and programming it into an integrated circuit, the hardware circuit implementing the logic method flow can be obtained.

[0037] The above method can be implemented by a controller in any suitable manner. For example, the controller can take the form of a microprocessor or processor and a computer-readable medium storing computer-readable program code (e.g., software or firmware) executable by the (micro)processor, logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers. Examples of controllers include, but are not limited to, microcontrollers. A memory controller can also be implemented as part of the control logic of a memory. It is understood that, in addition to implementing the controller in purely computer-readable program code form, the same functionality can be achieved by logically programming the method steps to make the controller take the form of logic gates, switches, ASICs, programmable logic controllers, and embedded microcontrollers. Such a controller can be considered a hardware component, and the means included therein for implementing various functions can also be considered as structures within the hardware component. Or even, the means for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0038] The systems, devices, modules, or units in the above embodiments can be implemented by computer chips or entities, or by products with certain functions.

[0039] For ease of description, the above devices are described in terms of function, divided into various modules. Of course, in implementing this specification, the functions of each module can be implemented in one or more software and / or hardware.

[0040] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this specification may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0041] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this specification. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0042] In some embodiments, this application may also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the prediction method described in any of the preceding claims.

[0043] In some embodiments, these computer program instructions may also be stored in a computer-readable storage medium capable of directing a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means implemented in a process. Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0044] In some embodiments, these computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0045] In some embodiments, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0046] In some embodiments, memory may include non-persistent memory in a computer-readable medium, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

[0047] In some embodiments, computer-readable media, including permanent and non-permanent, removable and non-removable media, can be used to store information by any method or technology. The information can be computer-readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device.

[0048] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A motion control method for a six-wheeled lunar rover based on a hierarchical control structure, characterized in that, The control method includes: Build a six-wheeled lunar rover model; A hierarchical control structure is established, which includes a state reference layer, a torque decision layer, and a torque distribution layer. In the state reference layer, a linear two-degree-of-freedom single-track model for front and rear axle steering is established, and the ideal yaw rate and ideal centroid sideslip angle of the six-wheeled lunar rover are calculated. The linear two-degree-of-freedom single-track model has degrees of freedom for lateral motion and yaw motion. In the torque decision layer, based on the ideal yaw rate and the ideal centroid sideslip angle, and combined with the ideal longitudinal rate set in the six-wheeled lunar rover model, a double power-law approach is designed to calculate the longitudinal rate tracking error, the yaw rate tracking error, and the centroid sideslip angle tracking error of the six-wheeled lunar rover. The generalized longitudinal force, lateral force, and yaw moment of the six-wheeled lunar rover are calculated using a sliding mode control method to design the torque decision layer. In the torque distribution layer, an objective function is constructed based on the generalized longitudinal force, the lateral force, the yaw moment, and the optimal control principle. Constraints are set according to the ground conditions and motor characteristics. The control objective is to minimize the tire load rate of the six-wheeled lunar rover and the total energy consumption of the six-wheeled lunar rover's motor. Dynamic optimization of torque distribution for the six wheels is performed in the torque distribution layer.

2. The motion control method for a six-wheeled lunar rover based on a hierarchical control structure as described in claim 1, characterized in that, The six-wheeled lunar rover model is a 22-degree-of-freedom dual-track vehicle dynamics model. The 22 degrees of freedom include longitudinal, lateral, vertical, roll around the longitudinal axis of the vehicle coordinate system, pitch around the lateral axis of the vehicle coordinate system, yaw around the vertical axis of the vehicle coordinate system, rotation and vertical sway of the six wheels around the axis, and steering of the four wheels on the front and rear axles.

3. The motion control method for a six-wheeled lunar rover based on a hierarchical control structure according to claim 2, characterized in that, In calculating the ideal yaw rate and the eccentricity angle of the center of mass, according to Newton's second law, the differential equation of the lateral motion of the six-wheeled lunar rover is: ； In the formula, The curb weight of the six-wheeled lunar rover. , These represent the longitudinal velocity and the lateral velocity of the six-wheeled lunar rover, respectively. This indicates that the derivative of the lateral velocity is taken. The yaw rate of the six-wheeled lunar rover is given by [reference to a specific value]. , These represent the steering angles of the first axle wheel and the third axle wheel of the six-wheeled lunar rover, respectively. , , These represent the lateral forces on the first axle wheels, the second axle wheels, and the third axle wheels of the six-wheeled lunar rover, respectively. According to Euler's second law, the differential equation for the yaw motion of the six-wheeled lunar rover is: ; In the formula, Let be the moment of inertia of the six-wheeled lunar rover body about the vertical axis of the body coordinate system. This indicates that the derivative of the yaw rate is taken. , These represent the distances from the center of mass of the six-wheeled lunar rover to the first axis and the distances from the third axis, respectively.

4. The motion control method for a six-wheeled lunar rover based on a hierarchical control structure according to claim 3, characterized in that, The design of the torque decision layer includes: The motion differential equations of the six-wheeled lunar rover in the longitudinal, lateral, and yaw directions are reconstructed at the torque decision layer: ； ； ； In the formula, This indicates that the derivative of the longitudinal velocity is taken. and These are the lateral forces on the left and right wheels of the i-th axis of the six-wheeled lunar rover, respectively. and These are the steering angles of the left and right wheels of the i-th axis of the six-wheeled lunar rover, respectively. To control the generalized longitudinal force of the six-wheeled lunar rover during its longitudinal motion, To control the generalized lateral force of the six-wheeled lunar rover during its lateral motion, The generalized yaw moment for controlling the movement of the six-wheeled lunar rover in the yaw direction; Based on the designed double power-law approach, the longitudinal velocity tracking error, the yaw rate tracking error, and the center of mass sideslip angle tracking error are calculated. The longitudinal velocity is controlled by the generalized longitudinal force. The longitudinal velocity tracking error is calculated using the switching function formula: ； In the formula, The tracking error of the longitudinal velocity of the six-wheeled lunar rover. The ideal longitudinal velocity of the six-wheeled lunar rover; Differentiate the above equation and combine it with the longitudinal motion differential equation of the six-wheeled lunar rover shown: ； Introducing the double-power reaching law with a saturation function, the formula is: ； In the formula, , , , For the design parameters in the double power-law approaching law, Let represent the saturation function in the double power reaching law, and the formula for the saturation function in the double power reaching law is: ； In the formula, The boundary layer thickness is set in the saturation function; According to the double-power approach law with saturation function, the generalized longitudinal force Represented as: ； In the formula, , , , For the design parameters in the double power-law approaching law, This represents the saturation function in the double power approach law; The generalized lateral force and the generalized yaw moment are expressed as follows: ； ； In the formula, The tracking error of the centroid sideslip angle of the six-wheeled lunar rover. The tracking error is the yaw rate of the six-wheeled lunar rover.

5. The motion control method for a six-wheeled lunar rover based on a hierarchical control structure according to claim 4, characterized in that, In the torque distribution layer, the generalized longitudinal force, the generalized lateral force, and the generalized yaw moment are used as the control targets for the torque distribution layer of the six-wheeled lunar rover torque distribution and stability control method: ； In the formula, The target control force required for the six-wheeled lunar rover to track the target's motion state; Force analysis of the six-wheeled lunar rover: ； In the formula, For target control , For the longitudinal force of the tire, The coefficient matrix is ​​given by the following formula: ； ； ； In the formula, , , They are represented as follows: ； ； 。 6. The motion control method for a six-wheeled lunar rover based on a hierarchical control structure according to claim 5, characterized in that, The longitudinal force of the tires is constrained by the tire adhesion limit and the motor output limit of the six-wheeled lunar rover. The tire adhesion limit constraint is as follows: ； In the formula, The equivalent adhesion coefficient on the lunar surface; The motor output limit constraint is given by the following formula: ； In the formula, This is the maximum output torque of the motor. The radius of the six-wheeled lunar rover's wheels; Combining the tire adhesion limit constraint and the motor output limit constraint, the constraint condition for the tire longitudinal force is expressed as follows: ； In the formula, , These are the lower and upper limits of the tire's longitudinal force, respectively: ； ； Based on the constraints of the longitudinal force of the tires, an objective function is established within the constraints. By approximating the objective function, the optimal solution for controlling the longitudinal force of the tires is obtained. In order to achieve coordinated control allocation for the stability and economy of the six-wheeled lunar rover, and considering the approximation error and the motor drive efficiency, objective functions are established respectively. by square representation of norm right The approximation error, and with The objective function for minimizing the error is as follows: ; In the formula, Let be the sign of the approximation error objective function. The variable represents the value that minimizes the approximation error objective function. These are the weighting coefficients. It is a weighted matrix that takes into account tire utilization. and The formulas are as follows: ； ； In the formula, , , These are the weighting coefficients for the generalized longitudinal force, the generalized lateral force, and the generalized yaw moment, respectively. , , , , , This indicates the wheel load coefficients of the front left, front right, middle left, middle right, rear left, and rear right wheels of the lunar rover; After optimization calculations, the longitudinal force of each wheel after stability optimization was obtained. The final torque optimization distribution result of each wheel drive motor is expressed as follows: ； In the formula, This represents the optimal torque distribution result for each hub motor. The longitudinal force of each wheel after stability optimization; With the goal of maximizing motor energy efficiency, the overall efficiency of the drive motors for the six wheels of the lunar rover is expressed as follows: ； In the formula, This represents the total torque required by the six-wheeled lunar rover. , , , , , This indicates the drive torque of the hub motors in the front left, front right, middle left, middle right, rear left, and rear right wheels of the six-wheeled lunar rover. , , , , , This indicates the rotational speeds of the front left, front right, middle left, middle right, rear left, and rear right wheels of the six-wheeled lunar rover. , , , , , This indicates the drive efficiency of the hub motors in the front left, front right, middle left, middle right, rear left, and rear right wheels of the six-wheeled lunar rover. To maximize the overall efficiency of the motor while minimizing the objective function value, the objective function for motor drive efficiency is defined as follows: ； After optimization calculations, the longitudinal force of each wheel after economic optimization was obtained. The final torque optimization distribution result of each wheel drive motor is expressed as follows: ； In the formula, This represents the optimal torque distribution result for each hub motor. The longitudinal force of each wheel after economic optimization.

7. The motion control method for a six-wheeled lunar rover based on a hierarchical control structure as described in claim 6, characterized in that, Based on the approximation error objective function and the motor drive efficiency objective function, and according to the control objective of improving energy efficiency while ensuring the driving stability of the six-wheeled lunar rover, a torque distribution coordination control module is designed. This module includes a judgment module and a switching module. The judgment module introduces an adhesion margin threshold coefficient to mark whether the tire force meets the power requirements. The formula is: ； In the formula, Indicates the margin threshold coefficient; Based on the aforementioned judgment module, a torque stability threshold is defined using the following formula: ； In the formula, Indicates correspondence The torque stability threshold; After optimal stability control allocation, the torque allocated to each drive motor and the torque stability threshold of each wheel are obtained. The switching module is used to design coordinated control of driving stability and energy economy. If the torque allocated to each drive motor is less than or equal to the torque stability threshold of each wheel, the driving environment of the six-wheeled lunar rover is considered sufficiently ideal to fully meet the vehicle stability requirements. Then, economic optimization is performed, and the result of the optimal economic control allocation is obtained based on the aforementioned calculation method. The output is the given torque for each wheel drive motor, and the formula is: ； If the torque of the drive motor exceeds the torque stability threshold, the torque distribution layer considers stability optimization and directly outputs the torque of the drive motor as the given torque for each wheel drive motor, as shown in the formula: 。 8. The motion control method for a six-wheeled lunar rover based on a hierarchical control structure according to claim 7, characterized in that, A switching parameter is introduced to achieve the switching between different target controls in the form of a weighted summation. The weighting function is expressed as: ； In the formula, To switch parameters; Define intermediate variables: ； ； The switching parameters Represented as: ； Based on the aforementioned coordinated control and allocation method for the stability and energy economy of the six-wheeled lunar rover, the dynamic optimization allocation result of the torque of the six-wheeled lunar rover is obtained through quadratic programming.

9. A lunar rover motion control system, characterized in that, The system includes a controller and a six-wheeled lunar rover, the controller being communicatively connected to the six-wheeled lunar rover, the controller being configured to perform the control method as described in any one of claims 1-8, and the six-wheeled lunar rover model performing scenario verification on the controller.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the control method as described in any one of claims 1-8.

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