Research On Key Technology Of Yaw Stability Control Strategy For Wheel-driven Electric Bus Based On Reference Model

With the increasing global climate,energy and environmental issues,new energy electric vehicles have become the focus of the development and research of the global automotive industry.Since the control units of the electric vehicle are relatively independent and have a very fast response,they have obvious control advantages,especially the four-wheel independent drive electric vehicle,which can realize the power of the whole vehicle by controlling the braking/driving torque of each wheel.Adjustments such as output and body posture.However,due to the complexity of its control system,more state parameters are required to ensure that the control system makes precise control based on real-time vehicle status.As one of the important technologies for the active safety of the vehicle,the yaw stability control can correct the yaw posture of the vehicle body during the running of the vehicle,effectively reducing the occurrence of dangerous situations such as side slip and tail of the vehicle,and facing the four-wheel independent driving electric motor.The yaw stability control of automobiles has become a research hotspot.Therefore,the accurate acquisition of the state parameters during the driving process and the yaw stability control based on the reference model have become the starting point and key point of the research content of this paper.Based on a research project with a certain enterprise,this paper takes a modified fourwheel-driven electric bus as the object,and carries out online estimation of vehicle state parameters and vehicle yaw stability control algorithm based on sliding mode control theory.the study.The main contents are as follows:According to the test vehicle parameters,the vehicle dynamics model was built by TruckSim and verified.Collect and comprehensively judge the information such as wheel speed,vehicle center of mass acceleration,steering wheel angle,acceleration/brake pedal opening,and gear position.And the equivalent vehicle centroid acceleration concept is proposed based on the wheel linear acceleration,and compared with the actual vehicle centroid acceleration.The judgment of the stability of the individual wheels is realized,and the multi-mode vehicle speed estimation is performed according to the four-wheel stability state.At the same time,the road surface adhesion coefficient was estimated online.A classic two-degree-of-freedom vehicle model and an extended three-degree-offreedom vehicle model considering longitudinal motion are established.Based on the accuracy and reliability of the model,the applicable conditions are studied.It is determined that the two models are used as the vehicle transverse direction under different steering wheel angles and vehicle speeds.The rationality of the ideal reference model for the pendulum stability control algorithm.Based on the synovial control theory,a composite reference model vehicle yaw stability control algorithm is proposed.The main vehicle selection speed or steering wheel angle is determined by the main selection two-degree-of-freedom or extended three-degree-offreedom vehicle model as the reference model of the control algorithm.The vehicle state parameter estimation algorithm and the yaw stability control algorithm are built in Simulink,and the estimation and control effects of the above algorithms are verified by reference to the current FMVSS 136 standard in the United States.And based on the dSPACE/CarSim hardware on the ring platform for hardware-in-the-loop experimental verification.The experimental results show that the vehicle state estimation algorithm designed in this paper can accurately estimate the vehicle speed and road surface adhesion coefficient.At the same time,the composite reference model vehicle yaw stability control algorithm can effectively improve the vehicle yaw stability.