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CN-121989702-A - Turning braking coordination control strategy for angle module vehicle electromechanical braking system

CN121989702ACN 121989702 ACN121989702 ACN 121989702ACN-121989702-A

Abstract

The invention belongs to the technical field of intelligent electric automobile chassis control and wire control, and particularly relates to a turning braking coordination control strategy of an angle module vehicle electromechanical braking system. The invention innovatively provides a layered cooperative control architecture oriented to the overdrive characteristic of an angle module by taking a 4WID-4WIS angle module vehicle as a research object, and realizes deep fusion optimization of longitudinal-transverse-yaw dynamics through real-time information interaction and decision cooperation among four-wheel independent control units, thereby breaking through the limitation of traditional centralized control.

Inventors

  • YAN YUNBING
  • SHI ZHEN
  • ZHANG SEN

Assignees

  • 武汉科技大学

Dates

Publication Date
20260508
Application Date
20260410

Claims (8)

  1. 1. The turning brake coordination control strategy of the angle module vehicle electromechanical brake system is characterized by comprising the following steps of: s1, building a three-degree-of-freedom vehicle dynamics model comprising longitudinal, transverse and yaw motions, a tire model describing longitudinal and transverse force coupling of a tire, and an EMB braking model; S2, constructing an upper controller, wherein the upper controller distributes four-wheel corners by adopting a feed-forward and feedback composite control strategy based on an Ackerman steering principle, and solves the target lateral force by combining a Model Predictive Control (MPC) method and a tire friction ellipse constraint; S3, constructing a lower controller, wherein the lower controller receives target lateral force issued by the upper controller, dynamically solves the target clamping force of each wheel through a self-adaptive braking force distribution algorithm based on braking intensity, steering intensity and real-time lateral stability, and drives an EMB actuator to output corresponding braking torque through closed-loop control based on an EMB system model.
  2. 2. The corner module vehicle electro-mechanical brake system turning brake coordination control strategy of claim 1, wherein in S1, the EMB brake model adopts a two-stage identification method comprising: The off-line identification stage comprises the steps of identifying key parameters of a motor by adopting a least square method based on EMB test bed data, and fitting a nonlinear relation between the clamping force of a brake disc and the axial displacement of a ball screw; And in the online self-adaptive correction stage, a recursive least square RLS algorithm with forgetting factors is introduced, and friction torque model parameters and transmission efficiency are updated in real time based on armature current, motor rotation speed and wheel vertical load.
  3. 3. The corner module vehicle electro-mechanical brake system turning brake coordination control strategy of claim 1, wherein the specific operation of S2 is as follows: s2.1, receiving steering wheel angle input and real-time yaw rate and vehicle speed signals of a vehicle; S2.2, calculating and distributing four-wheel turning angles by adopting a feed-forward and feedback composite control strategy based on an Ackerman steering principle; S2.3, constructing a multi-objective optimization function with the tire force utilization rate as an optimization target and the tire friction ellipse as a hard constraint by taking a three-degree-of-freedom vehicle dynamics model as a prediction model and combining the distributed four-wheel corners; S2.4, adopting a model predictive control method to solve in a rolling way to obtain the optimal target lateral force which meets the steering requirement and does not exceed the tire attachment limit.
  4. 4. The corner module vehicle electro-mechanical brake system turning brake coordination control strategy of claim 3, wherein the specific step of S2.2 comprises the following steps: s2.2.1, converting steering wheel angle input into front axle angle reference; s2.2.2, determining a feedforward coefficient of the rear axle rotation angle relative to the front axle rotation angle based on a steady-state steering condition that the vehicle mass center slip angle is zero; S2.2.3, acquiring the real-time yaw rate of the vehicle, and determining a feedback coefficient by combining the vehicle speed; s2.2.4, summing the feedforward term and the feedback term to obtain a rear axle rotation angle; s2.2.5, calculating the independent rotation angles of the four wheels according to the Ackerman steering geometric relationship by using the rotation angles of the front axle and the rotation angles of the rear axle.
  5. 5. The corner module vehicle electro-mechanical brake system turning brake coordination control strategy of claim 1, wherein the specific operation of S3 is as follows: s3.1, receiving target lateral force issued by the upper controller, and acquiring a real-time motion state of the vehicle; s3.2, dynamically solving the target clamping force of each wheel through an adaptive braking force distribution algorithm based on the braking strength, the steering strength and the centroid slip angle and the yaw rate representing the transverse stability; s3.3, the self-adaptive braking force distribution algorithm comprises a hierarchical adaptation function psi (z, sigma), and the hierarchical adaptation function distributes different braking force distribution weights for weak, medium and strong three-level working conditions according to different combinations of braking intensity and steering intensity; And S3.4, driving an EMB actuator to output braking torque corresponding to the target clamping force through closed-loop control based on the EMB system model.
  6. 6. The electronic mechanical braking system turning braking coordination control strategy of the angle module vehicle according to claim 5, wherein the specific operation of S3.3 is as follows, the hierarchical adaptation function psi (z, sigma) is divided into a weak working condition, a medium working condition and a strong working condition according to the braking intensity z and the steering intensity sigma, and different weight coefficients are set for different working conditions, wherein weight balance is allocated under the weak working condition, braking efficiency and tracking requirements are balanced under the medium working condition, and transverse stability is preferentially ensured under the strong working condition.
  7. 7. The electric mechanical brake system turning brake coordinated control strategy of the corner module vehicle according to claim 6, wherein in step S3.3, the adaptive braking force distribution algorithm further comprises a lateral stability correction function ζ (β, ω) that reduces the braking force distribution weight of the corresponding wheel when the centroid slip angle β or the yaw rate ω z deviates from its expected value by more than a preset threshold value, so as to preferentially secure lateral stability.
  8. 8. The corner module vehicle electro-mechanical brake system turning brake coordination control strategy of claim 5, wherein in S3.4, said lower level controller drives the EMB actuator with position-speed-force three closed loop control, wherein: The force closed loop is an outer loop, deviation between a target clamping force and the clamping force estimated based on the EMB system model is taken as input, and the target rotating speed of the motor is output through the PID controller; The speed closed loop is an intermediate loop, takes the deviation between the target rotating speed and the actual rotating speed of the motor as input, and outputs target current through the PI controller; the position closed loop is an inner loop, and the driving voltage is generated by using the target current and the motor rotor position feedback signal through space vector pulse width modulation SVPWM, so as to control the motor output torque.

Description

Turning braking coordination control strategy for angle module vehicle electromechanical braking system Technical Field The invention belongs to the technical field of intelligent electric automobile chassis control and wire control, and particularly relates to a turning braking coordination control strategy of an angle module vehicle electromechanical braking system. Background With the evolution of the automobile industry to a software defined chassis, the integration and intellectualization of a chassis system has become a core trend of the development of intelligent electric automobiles. Distributed drive technology has evolved from traditional in-wheel motor drive "corner module" architecture as a critical path for achieving chassis global control. The power unit, the steer-by-wire actuator (SBW) and the electronic mechanical brake system (EMB) are highly integrated into a physical form of an independent unit, so that independent driving, turning, braking and suspending capabilities are provided for four corners of a vehicle, and a typical multiple-input multiple-output (MIMO) overdrive system (Over-actuated System) is formed. However, the increase in physical integration also presents unprecedented control challenges, particularly under the typical compound operating regime of ‌ Turn-Brake (Brake-in-Turn) ‌. The complexity of this regime arises from its remarkable longitudinal-lateral dynamic strong coupling characteristics, with fundamental competing contradictions between longitudinal braking force and lateral force under the "friction ellipse" constraint. The compact design of the corner modules often results in unintended dynamic disturbances of the steering system by the brake system, exacerbating the control difficulties. The research of the corner module vehicle turning braking coordination control can be divided into three aspects of longitudinal and transverse decoupling control, dynamic coordination distribution of braking force and accurate control of an EMB system. The longitudinal and transverse decoupling control is used for solving the problems of longitudinal and transverse force coupling interference and multi-steering mode adaptation under the turning braking working condition, and the longitudinal and transverse control targets are separated through a decoupling algorithm, so that the control precision and the response speed are improved. Yan et al propose an angle module vehicle layered motion control framework, front and rear axle corners are distributed through feedforward-feedback control, four-wheel corners are optimized by combining an Ackerman principle, internal decoupling of a steering system is achieved, but strong coupling constraint of longitudinal and transverse forces under a braking working condition is not fused deeply, and general decoupling adaptation of a 2WS mode and a 4WS mode is not achieved. The Hang et al design a four-wheel steering vehicle path tracking controller based on a linear parameter change system by combining an LQR algorithm with feedforward control, and realize partial decoupling by parameter self-adaption, and adapt to different longitudinal speeds and friction coefficients, but do not relate to longitudinal and transverse dynamics decoupling under a braking working condition. Li et al adopts a sliding mode control design and a layered four-wheel steering path tracking control to convert path tracking into yaw rate tracking and combine lateral stability control to realize lateral internal decoupling without considering the influence of the integration characteristic of the angle module on the decoupling effect. Under the limit working condition, the nonlinear and multidimensional coupling effect of the vehicle is obviously enhanced, the existing decoupling control strategy focuses on a single steering mode or a pure steering working condition, the coupling decoupling of braking and steering is not considered enough, the overdrive advantage of the angle module vehicle cannot be fully exerted in the decoupling control, and the adaptability of external disturbance compensation and a variable attachment road surface still needs to be improved. The key point of dynamic coordination and distribution of braking force is to adapt the overdrive characteristic of the angle module and balance the braking efficiency and steering stability on the basis of longitudinal and transverse decoupling. Wu et al solve the maximum longitudinal force on line by combining with the attached ellipse constraint based on a 2-degree-of-freedom vehicle model to realize dynamic braking force distribution, but do not combine the front-rear wheel steering angle difference optimization distribution coefficient in a 4WS mode, and do not fully adapt to the decoupled dynamic load change. The ZHANG Z et al propose a lateral stability and braking performance cooperative control strategy to optimize the cornering braking effect, but do not introduce a lateral stability correction mecha