Research On States Observation And Lateral Stability Control Of Distributed Drive Electric Vehicle

The revolution of replacing traditional vehicles driven by internal combustion with new energy vehicles is promoting vigorously due to double constraints of oil resources depletion and environmental pollution gradually.It is no doubt pure electric vehicles are the most promising alternative solutions for the problem in future.Distributed drive electric vehicle(DDEV)is driven by in-wheel motor directly.It has unattainable dynamic control advantages as a redundant dynamic system comparing to that vehicle with other power-transmission structure.This paper focus on states observation and lateral stability control for DDEV.3 degree of freedom model,7 degree of freedom model and Dugoff tire model were established respectively as basis of vehicle states observer and lateral stability controller designing.DDEV simulation model was established based on vehicle simulation software veDYNA,including steering system model,suspension system model,in-wheel motor model,distributed drive system model,longitudinal speed tracking module.A DDEV states observer was designed for measuring yaw rate,sideslip angle and longitudinal speed based on a noise adaptation-extended Kalman filter(NA-EKF)algorithm.Performance validation of the states observer were carried out in DDEV simulation platform by means of simulation.Results indicate that the observer can solve the problem of declining observation accuracy,maximum mean absolute error of observer is no more than 34.23%,maximum root mean square error of observer is no more than 25.22%,peak absolute error is smaller,comparing to EKF observer.Hierarchical DDEV lateral stability control system was designed with yaw rate and sideslip angle as controlled variable,which based on collecting observed states of the proposed DDEV states observer.Adaptive law of control gain was proposed for twisting sliding mode algorithm.Upper controller with “feedback + feedforward” structure of DDEV lateral stability control system was designed based on the proposed adaptive twisting sliding mode(ATSM)algorithm to calculate direct yaw moment for maintaining vehicle lateral stability.Stability conditions of upper controller was derived from Lyapunov stability analysis.Then lower controller was designed to calculate output torque distribution of four wheels with direct yaw moment based on the proposed optimal longitudinal force distribution method.Simulation model of DDEV lateral stability control system was established in DDEV simulation model.Simulation was carried out at medium speed and high speed slalom test with high and low road friction coefficients,and high speed double lane change test with high and low road friction coefficients.Results indicate that the proposed DDEV lateral stability control system can make vehicle tracking desired motion states with high accuracy.It is reasonable that torque distribution of four wheels can guarantee vehicle lateral stability by imposing a direct yaw moment effectively.At the same time,tire force of on side would not be saturation easily,which would make vehicle lose lateral stability.The DDEV lateral stability control system can maintain vehicle lateral stability and enhance vehicle lateral margin effectively.