Study On Electronic Stability Control Of In-Wheel Motor EV

Under the dual pressures of energy and environment, the electric vehicle hasbecome a key point of current automotive industry.And among them, the electricvehicle with four motorized wheels has become a hot spot. Moreover, the research onthe performance and fuel economy of electric vehicle is more and more mature, whichleads that people play more and more attention to the dynamic performance of it.In this paper, the vehicle modeling, stability control strategy and controlalgorithm are researched, which are all based on the domestic and internationalresults.This article aims at the four-wheel-independent-drive electric vehicle, and thedynamic models of vehicle and wheel rotation, as well as models of steering system,drive motor and tire, are all established. Then the stability control accuracy of thismodel under several conditions including high speed and high or low adhesion road isverified, meanwhile the simulation results are compared with Carsim’s.The side slip angle and yaw velocity of electric vehicle are chosen as the controlvariables, which are based on the analysis of the relationship between state andstability of vehicle. Through the contrastive analysis of open loop and closed loop ofthe reference models including front-wheel steering, direct yaw moment control andfour-wheel steering, finally the direct yaw control model is chosen as the referenceone. The stability controller with layered structure is designed, and the upper motioncontroller is used to generate the generalized force of longitudinal and yaw element totrack driver’s goal. The longitudinal force is regulated by using PID controller, whichtakes the deviation of demand speed and actual speed as the input variable. On theside the yaw moment is calculated by using linear quadratic regulator after thecomparison of reference state and actual state.For the redundancy control allocation problem that the number of actuators isgreater than the general resultant force, the road adhesion conditions and motor driveability are considered, and then the allocation algorithms of respective longitudinal force are designed on the basis of stability and maneuverability optimization goal. Theweightiness of longitudinal force is established according to the above two goals bybringing in the dynamic ratio of vehicle centroid side-slip angle and its cap. Besides,the control algorithm based on the axle load distribution is proposed in case that theoptimal allocation conditions are not established.Finally, the sine steering and speeding up conditions in high adhesion road, lowadhesion road are chosen to verify this control strategy. And it shows thatoptimization allocation can control the vehicle centroid side-slip angle in a smallrange, as well as effectively follow the target speed and yawing velocity, in additionthe tire with larger vertical load is allocated a larger driving/braking force, which canadequately use the tire adhesion ability, make the utilization rate of each tire roughlyequal, and retain greater road friction allowance. In the end it proves that the stabilitycontrol algorithm in this paper can improve the stability of electric vehicle.