Multi-axis distributed driving vehicle torque distribution method based on conditional solution method
Through the torque distribution method of multi-axis distributed drive vehicle based on the conditional solution method, the torque optimization distribution equation is designed and solved, and the problem of difficult to obtain real-time optimal feasible solutions of torque distribution of multi-axis distributed drive vehicle in the prior art is solved, and the rationality, reliability and safety of torque distribution are realized.
Patent Information
- Application Number
- CN202510456158.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-11
- Publication Date
- 2025-06-20
AI Technical Summary
The prior art is difficult to obtain real-time optimal feasible solutions for torque distribution of multi-axis distributed drive vehicles in real time while considering multiple constraints, and the calculation time is relatively long.
The torque distribution method of multi-axis distributed driving vehicle based on conditional solution is adopted. Through the initialization module, the torque optimization distribution equation design module and the torque optimization distribution equation solution module based on conditional solution method, the torque optimization distribution equation is designed and solved to ensure the rationality, reliability and safety of torque distribution under nonlinear operating conditions.
It is realized that a real-time optimal feasible solution for torque distribution of multi-axis distributed drive vehicles is obtained while considering multiple constraints, and the accuracy, stability and robustness of torque control are improved.
Smart Images
Figure CN120171315A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an electric vehicle drive system, in particular to a torque distribution method for a multi-axis distributed drive vehicle based on a conditional solution method. Background Art
[0002] A distributed vehicle driven by independent in-wheel motors has significant actuator redundancy characteristics and is a typical over-driven system. In terms of underlying torque distribution, methods based on rules and optimization functions are often used.
[0003] The method based on rule distribution is simple and direct with small computational complexity, but it is difficult to effectively handle constraint conditions and cannot fully utilize the advantages of independent controllability of electric wheels. The method based on an optimization function cannot guarantee a real-time optimal feasible solution and has a long computational time. Therefore, it is necessary to design a solution method that can obtain a real-time optimal feasible solution while considering various constraint conditions. Summary of the Invention
[0004] To solve the above problems existing in the prior art, the purpose of the present invention is to provide a torque distribution method for a multi-axis distributed drive vehicle based on a conditional solution method, which can obtain a real-time optimal feasible solution while considering various constraint conditions and optimization.
[0005] To achieve the above purpose, the technical solution of the present invention is as follows:
[0006] A torque distribution method for a multi-axis distributed drive vehicle based on a conditional solution method is used for distribution by a torque distribution system for a multi-axis distributed drive vehicle based on a conditional solution method. The torque distribution system for a multi-axis distributed drive vehicle based on a conditional solution method includes an initialization module, a torque optimization distribution equation design module, and a torque optimization distribution equation solving module based on a conditional solution method. The torque distribution system for a multi-axis distributed drive vehicle based on a conditional solution method is hereinafter referred to as the system, and the multi-axis distributed drive vehicle is a heavy-duty vehicle with four axles.
[0007] The initialization module is responsible for checking whether the signal transceiver of the CAN communication module and the actuator module is normal, loading the total torque demand of the electric wheels and the front wheel steering angle signal, loading the dynamic model parameters of the multi-axis distributed drive vehicle, and loading the parameters of the torque distribution optimization problem.
[0008] The torque optimization distribution equation design module analyzes that under the influence of the tire adhesion ellipse and non-linear working conditions, the vehicle is prone to instability, and there is a certain coupling relationship between the longitudinal driving force and the lateral force of the tire, and designs the objective function, constraint conditions, and equation of torque optimization distribution.
[0009] The torque optimization distribution equation solving module based on the conditional solution method solves the torque optimization distribution equation with constraints obtained by the torque optimization distribution equation design module by using the conditional solution method to obtain the output torque of each electric wheel.
[0010] The control method includes the following steps:
[0011] Step 1: Initialization;
[0012] Step 2: Design the torque optimization distribution equation;
[0013] Step 3: Solve the torque optimization distribution equation;
[0014] Step 4: Perform torque control; Further, determine whether the multi-axle distributed drive vehicle reaches the control target. If so, the vehicle completes the control task; otherwise, go to Step 1.
[0015] Further, the method of initialization in Step 1 is as follows:
[0016] The initialization module is responsible for loading the total torque T required by the electric wheels F and the steering wheel angle signal δ i , loading the multi-axle distributed drive vehicle model parameters, and loading the parameters in the torque optimization distribution equation. The multi-axle distributed drive vehicle model parameters include the vehicle wheelbase, and the wheelbase is the distance between two wheels on the same axle; the parameters in the torque optimization distribution equation include the relaxation factor and the weight coefficient of the relaxation factor.
[0017] Further, the method of designing the torque optimization distribution equation in Step 2 is as follows:
[0018] According to the total torque T F , the steering wheel angle signal δ i , the multi-axle distributed drive vehicle model parameters, and the parameters in the torque optimization distribution equation, establish the relationship between the longitudinal driving force and the yaw moment of the vehicle and the torque distribution in the form of a mathematical equation as follows:
[0019]
[0020] In the formula, F x is the total longitudinal driving force of the vehicle tires, M z is the yaw moment of the vehicle, i is the serial number of the i-th axle of the multi-axle distributed drive vehicle, F xil and F xir are the longitudinal driving forces received by the left and right tires on the i-th axle respectively, D b is the wheelbase, and all wheelbases are equal, δ i is the steering wheel angle of the i-th axle.
[0021] Further rewrite the above formula into the following form:
[0022] A d U d =b d
[0023] In the formula:
[0024] b d =[F x M z T , F x =T F / R w , R w is the tire radius;
[0025] U d =[F x1l F x1r F x2l F x2r F x3l F x3r F x4l F x4r T ;
[0026]
[0027] Affected by the tire adhesion ellipse, under non-linear conditions, the vehicle is prone to instability, and there is a certain coupling relationship between the longitudinal driving force and the lateral force of the vehicle tires. Therefore, to reasonably solve the problem of torque distribution optimization, the following objective function J d is designed:
[0028]
[0029] In the formula, μ is the adhesion coefficient of the tire. n is the serial number of the nth tire of the multi-axle distributed drive vehicle, F xn , F yn and F zn are respectively the longitudinal driving force, the lateral driving force and the vertical driving force of the nth tire of the multi-axle distributed drive vehicle.
[0030] At the same time, to consider the road adhesion coefficient and the maximum torque output capacity of the in-wheel motor, the following constraint conditions are designed:
[0031]
[0032] In the formula, T nmax is the maximum torque of the in-wheel motor in the nth tire.
[0033] According to the above formula, the following torque optimization distribution equation is designed:
[0034]
[0035] In the formula, H is the weighted matrix of U d , diag() refers to the mathematical symbol of a diagonal matrix, and U u and U l are the maximum and minimum values of U d respectively; c dn is the longitudinal driving force weight coefficient of the nth tire; is an 8-row and 1-column matrix; ρ is a relaxation factor used to ensure that there is always a feasible solution for the objective function; θ ρ is the weight coefficient of the relaxation factor.
[0036] Furthermore, the method for solving the torque optimization distribution equation described in step 3 is as follows:
[0037] Solve the torque optimization distribution equation by the conditional solution method. First, transform the torque optimization distribution equation into the following form:
[0038]
[0039] In the formula:
[0040]
[0041]
[0042]
[0043] A dc =[A d I 2×1 ;
[0044]
[0045] ρ max and ρ min are the maximum and minimum values of the relaxation factor respectively.
[0046] Furthermore, solve the stationary point ξ d of the objective function J * :
[0047]
[0048] Let to get:
[0049]
[0050] Then, judge the stationary point ξ *Whether the constraint conditions \(g1(\xi)=0\) and \(g2(\xi)\leq0\) are satisfied:
[0051] 1) If satisfied, select \(\xi\) * in \(U\) d as the optimal longitudinal driving force \(F\) x , and its mathematical expression is as follows:
[0052] \(F\) x =\(\nu1\xi\) *
[0053] In the formula, the stationary point \(\xi\) * is the optimal value of \(\xi\), and \(F\) x is the matrix composed of the longitudinal driving force required by the tire; \(\nu1 = [I\) 8×8 , \(O\) 8×1 .
[0054] 2) Otherwise, use the Lagrange multiplier method to construct the following Lagrangian function:
[0055] \(J\) l = \(f(\xi)+g1(\xi) T Q l g1(\xi)+g2(\xi) T \(R l g2(\xi)+\lambda l g1(\xi)+\mu l g2(\xi)
[0056] In the formula, \(Q\) l and \(R\) l are the quadratic term Lagrange multiplier matrices of the equality constraint and inequality constraint corresponding to \(\xi\) respectively, and \(\lambda\) l and \(\mu\) l are the linear term Lagrange multiplier matrices of the equality constraint and inequality constraint respectively.
[0057] Further organize the above formula to get:
[0058]
[0059] In the formula,
[0060] From the gradient equation \(\nabla J\) l / \(\nabla\xi = 0\), the equality constraint \(g1(\xi)=0\) and the complementary slackness condition \(\lambda\) l g2(\xi)=0, the following equations are obtained:
[0061]
[0062] Therefore, the stationary point is obtained according to the above formula as follows:
[0063]
[0064] In the formula,
[0065] Similarly, select U in d as the optimal longitudinal driving force:
[0066]
[0067] In the formula, v2 = [I 8×8 , O 8×21
[0068] Then, the output torque of each electric wheel is calculated by the following equation:
[0069] T wi = R w F xi
[0070] Furthermore, the method for torque control described in step 4 is as follows:
[0071] Apply control constraints and perform filtering processing on the output torque T wi of each electric wheel, and use it as a control signal to be sent to the multi-axle distributed drive vehicle at a fixed frequency. The execution module of the multi-axle distributed drive vehicle controls the movement of the multi-axle distributed drive vehicle according to the output torque of each electric wheel.
[0072] The present invention has the following beneficial effects:
[0073] 1. Based on the relationship between the longitudinal driving force and yaw moment of the vehicle and torque distribution, considering the influence of the tire adhesion ellipse, the coupling problem of the longitudinal driving force and lateral force of the tire, and the problem that the vehicle is prone to instability under non-linear working conditions, the present invention designs a torque optimization distribution equation considering safety constraints such as road adhesion coefficient and maximum torque output capacity of the hub motor, ensuring the rationality, reliability and safety of the multi-axle distributed drive vehicle in torque optimization distribution.
[0074] 2. The present invention uses the conditional solution method to solve the torque optimization distribution equation, providing a solution idea for solving torque distribution with real-time optimal feasible solutions, and ensuring the distribution optimality, solution real-time performance, torque control accuracy, stability and robustness of the torque optimization distribution of the multi-axle distributed drive vehicle. BRIEF DESCRIPTION OF THE DRAWINGS
[0075] Figure 1 is the schematic diagram of the principle of the present invention.
[0076] Figure 2 is the schematic diagram of the torque distribution system of the multi-axle distributed drive vehicle based on the conditional solution method of the present invention.
[0077] Figure 3 This is the implementation flowchart of the present invention. Detailed implementation manners
[0078] The present invention will be further described below with reference to the accompanying drawings.
[0079] As Figures 1-3 shown, the present invention mainly consists of two parts:
[0080] (1) Design the torque optimization distribution equation: The real-time state information of the multi-axis distributed drive vehicle, including the total torque demand of the vehicle, the steering wheel angle, the road surface adhesion coefficient, and the maximum torque output capacity of the hub motor, is sent to the torque optimization distribution equation design module. Considering the influence of the tire adhesion ellipse and the certain coupling relationship between the longitudinal driving force and the lateral force of the tire, the torque optimization distribution equation is designed according to the safety constraints such as the road surface adhesion coefficient and the maximum torque output capacity of the hub motor.
[0081] (2) Solve the torque optimization distribution equation based on the conditional solution method: After receiving the torque optimization distribution equation determined by the torque optimization distribution equation design module, the torque optimization distribution equation solving module based on the conditional solution method will solve the optimal feasible solution of the output torque of each electric wheel in real time.
[0082] As Figure 1 shown, a torque distribution method for a multi-axis distributed drive vehicle based on the conditional solution method uses a torque distribution system for a multi-axis distributed drive vehicle based on the conditional solution method to perform torque distribution. The specific design steps of the torque distribution method for a multi-axis distributed drive vehicle based on the conditional solution method are as follows:
[0083] Step 1: Initialize;
[0084] Step 2: Design the torque optimization distribution equation;
[0085] Step 3: Solve the torque optimization distribution equation;
[0086] Step 4: Perform torque control.
[0087] As Figure 2 shown, a torque distribution system for a multi-axis distributed drive vehicle based on the conditional solution method includes an initialization module, a torque optimization distribution equation design module, and a torque optimization distribution equation solving module based on the conditional solution method.
[0088] As Figure 3 shown, the implementation steps of the present invention are consistent with the steps of the invention content.
[0089] The present invention is not limited to the details of the above embodiments, and any equivalent conceptions or changes within the technical scope disclosed by the present invention are included in the protection scope of the present invention.
Claims
1. A torque distribution method for a multi-axis distributed drive vehicle based on a conditional solution method, characterized in that: The torque distribution system of a multi-axis distributed drive vehicle based on a conditional solution method is used for distribution. The torque distribution system of a multi-axis distributed drive vehicle based on a conditional solution method includes an initialization module, a torque optimization distribution equation design module and a torque optimization distribution equation solution module based on a conditional solution method. The torque distribution system of a multi-axis distributed drive vehicle based on a conditional solution method is hereinafter referred to as a system. The multi-axis distributed drive vehicle is a heavy-duty vehicle with four axles. The initialization module is responsible for checking whether the signal transmission and reception of the CAN communication module and the actuator module are normal, loading the total torque required by the electric wheel and the front wheel angle signal, loading the multi-axis distributed drive vehicle dynamics model parameters, and loading the parameters of the torque distribution optimization problem; The torque optimization distribution equation design module analyzes that the vehicle is prone to instability under the influence of the tire adhesion ellipse and nonlinear working conditions, and there is a certain coupling relationship between the tire longitudinal driving force and the lateral force, and designs the objective function, constraint conditions and equations for torque optimization distribution; The torque optimization distribution equation solving module based on the conditional solution method solves the torque optimization distribution equation with constraint conditions obtained by the torque optimization distribution equation design module, and obtains the output torque of each electric wheel by using the conditional solution method; The control method comprises the following steps: Step 1: Initialization; Step 2: Design torque optimization distribution equation; Step 3: Solve the torque optimization distribution equation; Step 4: perform torque control; further, determine whether the multi-axis distributed drive vehicle has achieved the control target, if so, the vehicle completes the control task, otherwise go to step 1.
2. The method for distributing torque of a multi-axis distributed drive vehicle based on a conditional solution method according to claim 1, characterized in that: The initialization method described in step 1 is as follows: The initialization module is responsible for loading the total torque T required by the electric wheel F and steering wheel angle signal δ i , load the multi-axis distributed drive vehicle model parameters, load the parameters in the torque optimization distribution equation; the multi-axis distributed drive vehicle model parameters include the vehicle wheelbase, and the wheelbase is the distance between two wheels on the same axle; the parameters in the torque optimization distribution equation include the relaxation factor and the weight coefficient of the relaxation factor.
3. The method for distributing torque of a multi-axis distributed drive vehicle based on a conditional solution method according to claim 1, characterized in that: The method for designing the torque optimization distribution equation in step 2 is as follows: According to the total torque T F , steering wheel angle signal δ i , the parameters of the multi-axis distributed drive vehicle model and the parameters in the torque optimization distribution equation, and the relationship between the longitudinal driving force and yaw moment of the vehicle and the torque distribution is established in the form of a mathematical equation as follows: In the formula, F x is the total longitudinal driving force of the vehicle tire, M z is the yaw moment of the vehicle, i is the serial number of the i-th axis of the multi-axis distributed drive vehicle, F xil and F xir are the longitudinal driving forces on the tires on the left and right sides of the i-th axis, D b is the wheelbase, and the wheelbases are equal, δ i is the steering wheel angle of the i-th axis; Further rewrite the above formula into the following form: A d U d =b d Where: b d =[F x M z ] T , F x =T F / R w , R w is the tire radius; U d =[F x1l F x1r F x2l F x2r F x3l F x3r F x4l F x4r ] T ; Affected by the tire adhesion ellipse, the vehicle is prone to instability under nonlinear conditions, and there is a certain coupling relationship between the longitudinal driving force and lateral force of the vehicle tire; therefore, in order to reasonably solve the torque distribution optimization problem, the following objective function J is designed: d : Where μ is the tire adhesion coefficient; n is the serial number of the nth tire of the multi-axle distributed drive vehicle, and F xn 、F yn and F zn are the longitudinal driving force, lateral driving force and vertical driving force of the nth tire of the multi-axle distributed drive vehicle respectively; At the same time, in order to consider the road adhesion coefficient and the maximum torque output capacity of the hub motor, the following constraints are designed: Where, T nmax is the maximum torque of the hub motor in the nth tire; According to the above formula, the following torque optimization distribution equation is designed: Where H is U d The weight matrix of diag() refers to the mathematical symbol for a diagonal matrix. u and U l U d The maximum and minimum values of c dn is the longitudinal driving force weight coefficient of the nth tire; is a matrix with 8 rows and 1 column; ρ is the relaxation factor, which is used to ensure that the objective function always has a feasible solution; θ ρ is the weight coefficient of the relaxation factor.
4. The method for distributing torque of a multi-axis distributed drive vehicle based on a conditional solution method according to claim 1, characterized in that: The method for solving the torque optimization distribution equation in step 3 is as follows: The torque optimization distribution equation is solved by the conditional solution method; first, the torque optimization distribution equation is converted into the following form: Where: A dc =[A d I 2×1 ]; ρ max and ρ min are the maximum and minimum values of the relaxation factor, respectively; Further, solve the objective function J d The stationary point ξ * : make have to: Then, determine the stationary point ξ * Whether the constraints g1(ξ)=0 and g2(ξ)≤0 are satisfied: 1) If satisfied, select ξ * U d As the optimal longitudinal driving force F x , its mathematical expression is as follows: F x =ν1ξ * Where, the stationary point ξ * is the optimal value of ξ, F x is the matrix composed of the longitudinal driving force required by the tire; v1 = [I 8×8 ,O 8×1 ]; 2) Otherwise, use the Lagrange multiplier method to construct the following Lagrange function: J l =f(ξ)+g1(ξ) T Q l g1(ξ)+g2(ξ) T R l g2(ξ)+λ l g1(ξ)+μ l g2(ξ) In the formula, Q l and R l are the quadratic Lagrange multiplier matrices of the equality and inequality constraints corresponding to ξ, λ l and μ l are the first-order Lagrange multiplier matrices of equality constraints and inequality constraints respectively; Further rearrangement of the above formula yields: In the formula, From the gradient equation The equality constraint g1(ξ)=0 and the complementary relaxation condition λ l g2(ξ)=0, we get the following equation: Therefore, according to the above formula, the stationary point is obtained as follows: In the formula, Similarly, choose U d As the optimal longitudinal drive: In the formula, v2=[I 8×8 ,O 8×21 ] Then, the output torque of each electric wheel is calculated by the following equation: T wi =R w F xi 。 5. The method for distributing torque of a multi-axis distributed drive vehicle based on a conditional solution method according to claim 1, characterized in that: The method for performing torque control described in step 4 is as follows: Output torque T to each electric wheel wi Control constraints are imposed and filtering is performed, which are sent to the multi-axis distributed drive vehicle at a fixed frequency as control signals. The multi-axis distributed drive vehicle execution module controls the movement of the multi-axis distributed drive vehicle according to the output torque of each electric wheel.