Vehicle drive anti-skid control method considering semi-axle characteristics and actuator hysteresis

Abstract

This invention discloses a vehicle drive anti-slip control method considering half-shaft characteristics and actuator hysteresis, relating to the field of vehicle dynamics control, and comprising the following steps: S1, signal processing; S2, determination of drive anti-slip entry conditions; S3, calculation of feedforward control torque value; S4, torque adjustment based on half-shaft elastic dynamics model; S5, obtaining the target drive torque by outputting torque compensation results. The control method inputs vehicle wheel speed signals, motor speed signals, accelerator pedal signals, longitudinal acceleration signals, and motor torque signals; by constructing a transmission system dynamics model including a half-shaft dynamics model, and combining feedforward and feedback control strategies, drive torque adjustment is achieved. This invention can effectively suppress half-shaft torsional vibration and slip oscillation, improve vehicle driving stability and control robustness under complex operating conditions, thereby solving the slip oscillation problem caused by transmission system elasticity and actuator hysteresis.

Description

Technical Field

[0001] This invention relates to the field of vehicle dynamics control, and more particularly to a vehicle drive anti-slip control method that takes into account the elasticity of the transmission system and the hysteresis of the actuator. Specifically, it is a drive anti-slip control method that can suppress half-shaft torsional vibration and improve slip control stability. Background Technology

[0002] Vehicle traction control (TCS) is a crucial control technology for ensuring vehicle longitudinal stability. Its core objective is to maintain the wheel slip ratio within an optimal range by adjusting the drive torque, thereby fully utilizing road surface adhesion and improving vehicle dynamics and safety. Existing traction control methods are mostly based on slip ratio control, which offers advantages such as fast response and high control precision.

[0003] However, existing TCSs typically employ a rigid transmission system model, assuming that the motor output torque can be transmitted to the wheels without lag or deformation. But in an electric drive axle structure, the half-shaft, as a crucial transmission component between the motor and the wheels, possesses significant torsional elasticity and damping characteristics. Under dynamic conditions, this elasticity introduces typical torsional vibration modes, the frequency of which is determined by the half-shaft stiffness and the equivalent rotational inertia on the motor and wheel sides. In actual vehicles, this mode frequency is generally distributed in the range of several Hz to over ten Hz. On the other hand, the motor and its controller in an electric drive system inevitably exhibit actuator dynamic lag, which can be equivalent to a first-order inertial element, and its response frequency is mainly determined by the time constant. Engineering experience shows that this dynamic response frequency is usually on the same order of magnitude as the half-shaft torsional mode frequency. When the two frequencies are close, coupling effects can easily form during closed-loop control. Specifically, when the vehicle is in TCS (Traction Control System) mode, changes in motor torque excite the half-shaft to produce torsional vibration. This vibration, in turn, affects the actual driving force at the wheel end, causing periodic fluctuations in wheel-end torque. Under closed-loop control, these fluctuations are further fed back to the slip ratio control system, resulting in an amplified oscillation effect. In severe cases, this can lead to slip ratio oscillations, control non-convergence, and even periodic instability of the driving force, directly impacting the vehicle's traction performance and driving safety.

[0004] Compared to electric vehicles, traditional gasoline vehicles have slower engine torque response and lower system bandwidth, making it difficult to excite high-frequency torsional modes of the half-shaft. Meanwhile, components such as clutches, gearboxes, and torque converters in the transmission system have significant buffering and damping effects, naturally filtering torque fluctuations. Furthermore, traditional TCS systems are mostly implemented through braking intervention or slow engine torque adjustment, with control frequencies far lower than the half-shaft vibration mode frequencies, making it difficult to form coupled oscillation conditions.

[0005] Meanwhile, in electric drive systems, the combined effect of high-bandwidth control and low-damping transmission structures, along with the elastic effect of the half-shaft and actuator hysteresis, significantly reduces the system stability margin and increases the risk of slip control oscillations. Existing control strategies generally do not explicitly consider half-shaft elastic dynamics and lack mechanisms to suppress torsional vibrations, making it difficult to guarantee control performance under complex road conditions or rapid dynamic operating conditions. Summary of the Invention

[0006] To address the slip oscillations and control instability caused by the elastic effect of the half-shaft in the prior art, this invention provides a vehicle drive anti-slip control method that considers half-shaft characteristics and actuator hysteresis. The aim is to introduce half-shaft torsional state information into the control process and combine it with a robust control strategy to achieve synergistic suppression of half-shaft torsional vibrations and slip oscillations, thereby improving system stability, control accuracy, and overall vehicle dynamics performance, and meeting the control requirements of high-performance electric drive vehicles.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: The present invention provides a vehicle drive anti-slip control method that considers half-shaft characteristics and actuator hysteresis, characterized by comprising the following steps: Step 1: Acquire vehicle wheel speed signals, motor speed signals, accelerator pedal signals, longitudinal acceleration signals, and motor torque signals. Based on the relationship between vehicle wheel speed signals, longitudinal acceleration signals, and vehicle dynamics, calculate the vehicle's longitudinal speed. Based on the vehicle dynamics model and longitudinal acceleration signal, estimate the vehicle's vertical load. ; Step 2: Only when the current operating condition is driving condition, based on the vehicle's longitudinal speed Given the vehicle wheel speed signal, calculate the slip ratio of the i-th wheel. Only when the slip ratio of the right rear wheel is... Or left rear wheel slip ratio Exceeding the target slip ratio At that time, drive anti-slip control is executed; Step 3: Based on the target slip ratio And road surface adhesion conditions, combined with vehicle longitudinal speed and vehicle vertical load Calculate the feedforward torque It is used to characterize the target driving force level required by the vehicle drive system under the current operating conditions; Step 4: Construct a dynamic model of the transmission system including a half-shaft dynamic model to obtain the target slip ratio. The difference between the actual slip ratio and the actual slip ratio Integral of the difference Half-shaft torsion angle Speed ​​difference between the two ends of the half shaft and the actual torque of the motor The system state Therefore, the feedback torque is calculated based on equation (1). ,in, For transpose; (1) In equation (1), This is the gain matrix; Step 5: Based on feedback torque With feedforward torque To obtain the target driving torque In conjunction with the accelerator pedal signal, the output torque of the vehicle is limited to ensure that it does not exceed the maximum available torque corresponding to the road surface adhesion.

[0008] The characteristic of the vehicle drive anti-skid control method considering half-shaft characteristics and actuator hysteresis described in this invention is that, in step three, the relationship between the slip ratio S and the road surface adhesion coefficient μ in the road surface adhesion conditions is established using equation (1): (2) In equation (1), There are 3 tire model parameters.

[0009] Furthermore, a semi-axis dynamic model is constructed using equation (2): (3) In formula (2) For the half-shaft stiffness; For half-axis damping; This refers to the torque of the half-shaft.

[0010] Furthermore, in step four, the gain matrix... The optimal gain at each operating point is obtained using the H∞ robust control method and the H2 robust control method, and includes: Step 4.1: Construct using equation (4) State feedback equations for robust control methods; (4) In equation (4): This is the first auxiliary matrix. Indicates the second auxiliary matrix; Denotes the perturbation matrix, and , , For two matrix elements; , There are two state matrices; , for Two weight matrices for robust control; Let be a constant greater than 0; and we have: (5) (6) (7) (8) In equations (5)-(6), This is the motor delay factor; , , , , , , , It consists of eight matrix elements; In equations (7)-(8), for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; Step 4.2: Construct using equation (9) Performance constraint equations for robust control methods; (9) In equation (9), , for The robust control method uses two weight matrices; and we have: (10) (11) In equations (10) and (11), for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; Step 4.3: Solve equations (4) and (9) to obtain the gain matrix. .

[0011] Furthermore, in step five, equation (12) is used to limit the output torque of the vehicle: (12) In equation (12), For minimum output torque, For maximum output torque, For minimum torque change rate, The maximum torque change rate, This represents the rate of change of the vehicle's output torque.

[0012] The present invention provides an electronic device, including a memory and a processor, characterized in that the memory is used to store a program that supports the processor in performing the method described therein, and the processor is configured to execute the program stored in the memory.

[0013] The present invention discloses a computer-readable storage medium storing a computer program, characterized in that the computer program is executed by a processor to perform the steps of the method described thereon.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. By introducing a half-shaft elastic dynamics model, this invention incorporates the half-shaft torsional angle and speed difference into the control feedback, thereby achieving active suppression of torsional vibration in the transmission system, reducing torque transmission lag and oscillation, making the wheel-end torque smoother, and improving the slip ratio control accuracy and system stability.

[0015] 2. By combining robust control and gain scheduling mechanisms, this invention achieves adaptive adjustment of control parameters while considering the elasticity of the half-shaft and the hysteresis of the actuator. This effectively suppresses slip ratio oscillations, improves system convergence and anti-disturbance capabilities, and thus enhances vehicle driving stability and safety under complex working conditions. Attached Figure Description

[0016] Figure 1 This is an overall flowchart of the drive anti-slip control method proposed in this invention; Figure 2 This is a flowchart illustrating the calculation of longitudinal vehicle speed, wheel acceleration, and actual slip ratio proposed in this invention. Figure 3 This is a flowchart illustrating the calculation of vertical load, road surface conditions, and optimal slip ratio proposed in this invention. Figure 4 Here are the μ-S curves of the four standard road surfaces proposed in this invention; Figure 5 This is a structural diagram of the semi-axial elastic dynamics model used in this invention; Figure 6 This is a diagram showing the overall logic architecture of the anti-slip control algorithm of this invention. Detailed Implementation

[0017] The technical solution of this patent will be further described in detail below with reference to specific embodiments.

[0018] In this embodiment, a method for controlling the anti-skid mechanism of a hub motor-driven vehicle involves obtaining a scheduling table through robust gain calculation and then using this table, along with the vertical load and longitudinal vehicle speed changes acquired through signal processing, to obtain corresponding gain values. This achieves robust control of the slip ratio while suppressing half-shaft vibration, thereby improving the control effect of the anti-skid technology. For more details, please refer to... Figure 1 The method includes the following steps: like Figure 2 As shown, the longitudinal speed of the vehicle is obtained by fusing wheel speed and acceleration using equation (1). : (1) In equation (1), The vehicle speed is calculated based on wheel speed. The vehicle speed is obtained by integrating the vehicle's longitudinal acceleration signal. For fusion weighting coefficients.

[0019] The vehicle speed is calculated by weighting the wheel speeds of each wheel using equation (2). : (2) In equation (2), For the number of wheels, The radius of the wheel's rolling motion. Let be the rotational speed of the i-th wheel.

[0020] like Figure 2 As shown, the slip ratio of the i-th wheel is obtained by calculating the vehicle speed signal and the estimated vehicle speed signal using equation (3). : (3) like Figure 3 As shown, the vertical load on the drive wheel is obtained using equation (4) based on the longitudinal acceleration signal. : (4) In equation (3), For the overall vehicle weight; This refers to the sprung mass of the entire vehicle. For the mass of the wheel; The longitudinal acceleration of the vehicle; For vehicle center of gravity quality; This refers to the wheelbase; It is the acceleration due to gravity; This is the distance from the center of mass to the front axle.

[0021] Based on the Burckhardt empirical μ-S model, the relationship between the slip ratio S and the road surface utilization adhesion coefficient μ is obtained using equation (5): (5) In equation (5), These are three tire model parameters, related to the adhesion conditions of the road surface in contact with each wheel. The relationship curve between slip ratio and adhesion coefficient is shown below. Figure 4 As shown.

[0022] This invention selects four different standard road surfaces as reference road surfaces for road surface identification, and the optimal slip ratio of the four road surfaces. and maximum road adhesion coefficient The values ​​are: 0.03 and 0.05 for icy surfaces; and 0.065 and 0.19 for snowy surfaces. The wet asphalt concentrations are 0.131 and 0.8; the dry asphalt concentrations are 0.170 and 1.171. Optimal slip ratio: Target slip ratio for four standard road surfaces and maximum adhesion coefficient The expression is: (6) In practical applications, it can be obtained by a one-dimensional search method based on the relationship between the slip ratio S and the road surface adhesion coefficient μ, which will not be elaborated here.

[0023] The slip ratio of the right rear wheel is calculated using equation (3) only when the current operating condition is a driving condition. and left rear wheel slip ratio When one of them exceeds the current target slip ratio of the road surface When the traction control is engaged, the robust controller determines that the traction control has intervened. After the wheels enter the traction control system, the controller calculates the difference between the target slip ratio and the actual slip ratio. Integral of the difference Half-shaft torsion angle Speed ​​difference between the two ends of the half shaft and the actual torque of the motor As the input, it is shown in equation (7): (7) In formula (7) This refers to the motor speed; This represents the overall transmission ratio of the transmission system.

[0024] like Figure 5 As shown, the semi-axis dynamic model can be constructed using equation (8): (8) In equation (8), For the half-shaft stiffness; For half-axis damping; This refers to the torque of the half-shaft.

[0025] like Figure 6 As shown, the gain calculation process is as follows: The robust gain calculation method involves using the combination of H∞ and H2 to obtain the optimal gain at each operating point, where the gain matrix... The expression to be solved is as follows: Step 4.1: Construct using equation (9) State feedback equations for robust control methods; (9) In equation (9): This is the first auxiliary matrix. Indicates the second auxiliary matrix; Denotes the perturbation matrix, and , , There are two matrix elements, and their values ​​are... ,in The moment of inertia of the half-axis; The moment of inertia of the wheel; , There are two state matrices; , for Two weight matrices for the robust control method; and: (10) (11) (12) (13) In equations (10)-(11), This is the motor delay factor; , , , , , , , There are 8 intermediate variables, and their values ​​are as follows:

[0026] ; ; ; ; ; ; ; ; is a constant greater than 0; where, This is the total moment of inertia between the motor and the half-shaft.

[0027] In equations (12)-(13), for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for Robust control method for winning drive torque The weight value.

[0028] Step 4.2: Construct using equation (9) Performance constraint equations for robust control methods; (9) In equation (9), , for The robust control method uses two weight matrices; and we have: (10) (11) In equations (10) and (11), for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; comprehensive Status feedback and The gain matrix is ​​obtained by solving for performance constraints. .

[0029] like Figure 6 As shown, feedforward control torque As shown in equation (11): (11) The gain matrix obtained through gain calculation Feedback torque can be obtained by matching with the robust controller input. As shown in equation (12): (12) In equation (12): State variables Control parameters calculated using robust control; State variables Control parameters calculated using robust control; State variables Control parameters calculated using robust control; State variables Control parameters calculated using robust control; State variables The control parameters are calculated using robust control.

[0030] Step 4.3, the target driving torque can be obtained using equation (13): (13) In equation (13), This is the proportionality coefficient.

[0031] like Figure 6 As shown, the output torque of the vehicle is limited by equation (14), and the final output torque is obtained: (14) In equation (14), For minimum output torque, For maximum output torque, For minimum torque change rate, The maximum torque change rate, This represents the rate of change of the vehicle's output torque.

[0032] After updating the gain value, the motor drive torque is adjusted to ensure the output torque meets the requirements. .

[0033] In summary, the control method proposed in this invention, by introducing a half-shaft elastic dynamics model and incorporating the half-shaft torsional angle and speed difference into the control feedback, achieves active suppression of torsional vibration, reduces torque transmission lag and oscillation, and improves wheel-end torque smoothness. Through a combination of robust control and gain scheduling, it achieves adaptive adjustment of control parameters under different vehicle speeds and vertical loads, improving system robustness and convergence. By introducing an actuator dynamic model, the controller design is made more closely aligned with the characteristics of actual electric drive systems, effectively avoiding slip rate oscillations caused by hysteresis. Under complex road conditions and high-torque drive conditions, when significant wheel slippage occurs, the controller can effectively control the drive wheel slip rate within the target range.

Claims

1. A vehicle drive anti-skid control method considering half-shaft characteristics and actuator hysteresis, characterized in that, Includes the following steps: Step 1: Acquire vehicle wheel speed signals, motor speed signals, accelerator pedal signals, longitudinal acceleration signals, and motor torque signals. Based on the relationship between vehicle wheel speed signals, longitudinal acceleration signals, and vehicle dynamics, calculate the vehicle's longitudinal speed. ; Estimate vehicle vertical load based on vehicle dynamics model and longitudinal acceleration signal. ; Step 2: Only when the current operating condition is driving condition, based on the vehicle's longitudinal speed Given the vehicle wheel speed signal, calculate the slip ratio of the i-th wheel. Only when the slip ratio of the right rear wheel is... Or left rear wheel slip ratio Exceeding the target slip ratio At that time, drive anti-slip control is executed; Step 3: Based on the target slip ratio And road surface adhesion conditions, combined with vehicle longitudinal speed and vehicle vertical load Calculate the feedforward torque It is used to characterize the target driving force level required by the vehicle drive system under the current operating conditions; Step 4: Construct a dynamic model of the transmission system including a half-shaft dynamic model to obtain the target slip ratio. The difference between the actual slip ratio and the actual slip ratio Integral of the difference Half-shaft torsion angle Speed ​​difference between the two ends of the half shaft and the actual torque of the motor The system state Therefore, the feedback torque is calculated based on equation (1). ,in, For transpose; (1) In equation (1), This is the gain matrix; Step 5: Based on feedback torque With feedforward torque To obtain the target driving torque In conjunction with the accelerator pedal signal, the vehicle's output torque is limited to ensure that it does not exceed the maximum usable torque corresponding to the road surface adhesion capability.

2. The vehicle drive anti-skid control method considering half-shaft characteristics and actuator hysteresis according to claim 1, characterized in that, In step three, the relationship between the slip ratio S and the road surface utilization adhesion coefficient μ in the road surface adhesion conditions is established using equation (1): (2) In equation (1), There are 3 tire model parameters.

3. The vehicle drive anti-skid control method considering half-shaft characteristics and actuator hysteresis according to claim 1, characterized in that, In step four, the semi-axis dynamic model is constructed using equation (2): (3) In formula (2) For the half-shaft stiffness; For half-axis damping; This refers to the torque of the half-shaft.

4. The vehicle drive anti-skid control method considering half-shaft characteristics and actuator hysteresis according to claim 1, characterized in that, In step four, the gain matrix The optimal gain at each operating point is obtained using the H∞ robust control method and the H2 robust control method, and includes: Step 4.1: Construct using equation (4) State feedback equations for robust control methods; (4) In equation (4): This is the first auxiliary matrix. Indicates the second auxiliary matrix; Denotes the perturbation matrix, and , , For two matrix elements; , There are two state matrices; , for Two weight matrices for robust control; Let be a constant greater than 0; and we have: (5) (6) (7) (8) In equations (5)-(6), This is the motor delay factor; , , , , , , , It consists of eight matrix elements; In equations (7)-(8), for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; Step 4.2: Construct using equation (9) Performance constraint equations for robust control methods; (9) In equation (9), , for Two weight matrices in the robust control method; and: (10) (11) In equations (10) and (11), for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; for In robust control methods The weight value; Step 4.3: Solve equations (4) and (9) to obtain the gain matrix. .

5. The vehicle drive anti-skid control method considering half-shaft characteristics and actuator hysteresis according to claim 1, characterized in that, Step five involves using equation (12) to limit the vehicle's output torque: (12) In equation (12), For minimum output torque, For maximum output torque, For minimum torque change rate, The maximum torque change rate, This represents the rate of change of the vehicle's output torque.

6. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports a processor in executing the method of any one of claims 1-5, the processor being configured to execute the program stored in the memory.

7. A computer-readable storage medium storing a computer program thereon, characterized in that, The computer program is executed by the processor to perform the steps of the method according to any one of claims 1-5.

Images