Research On Lateral Stability Control For Four-Wheel Independently Actuated Vehicle

The four-wheel independently actuated vehicle is a class of electric vehicles with driving power provided by wheel hub motors.Compared with the vehicles with traditional internal combustion engine,each wheel motor can be independently controlled,and the response time of the motor is much shorter than that of a traditional internal combustion engine.Therefore,the dynamic performance of the four-wheel independently actuated vehicle is more flexible,and it has more advantages in controller design,which is an important development direction in the future.For modern cars,safety performance is one of the most important characteristics,and maintaining the lateral stability of the vehicle can prevent dangerous situations such as sideslip and roll effectively.Therefore,this paper takes four-wheel independently actuated vehicles as the research object,and designs a controller that can improve the vehicle’s lateral stability and handling performance for its power system.Based on the individually controllable hub motor,a layered control structure is designed.The main work is listed as follows:First,the dynamic characteristics of the four-wheel independently actuated vehicles are analyzed,and a 7-degree-of-freedom vehicle model is established to describe the dynamic performance of the vehicle.Some simplifications are made based on the vehicle driving conditions,and a two-degree-of-freedom vehicle model is established for the controller design.Secondly,considering various practical situations,the upper layer of controller is designed.Considering the vehicle longitudinal speed as the system’s uncertain parameter and actuator saturation,a multi-objective controller based on state-feedback is designed with using the homogeneous polynomial parameter dependence method.Considering that the vehicle sideslip angle is difficult to measure,a static output feedback controller is designed.And a two-stage heuristic algorithm is used to solve the controller gain.Considering the time-varying longitudinal vehicle velocity,the area of the polytope which used to represent the uncertain parameters is reduced,and the controller gain disturbance is considered.The non-fragile multi-objective linear parameter varying controller is designed.The effect of the designed controller is verified through simulations.Finally,the optimization algorithm for the distribution of desired external yaw moment is designed in the lower layer.Considering the distribution error from the upper layer to the lower layer and the workload of the tires,the distribution result is optimized by minimizing their values,and the torque that each wheel motor should output is solved.The simulation results under various steering conditions indicate that the designed controller can effectively control the vehicle sideslip angle and yaw rate in a reasonable range,and close to their reference values.At the same time,the designed control torque distribution algorithm ensures a small distribution error and a low tire utilization rate.Based on the control strategy designed in this paper,the vehicle lateral stability and handling performance can be effectively improved.