Stability Control Of Electric Vehicle Based On Adaptive Sliding Mode

In recent years,the automobile industry has developed rapidly under the dependence of people on it,but the environmental pollution and energy consumption caused by automobiles have become increasingly serious.New energy vehicles are widely concerned by scholars at home and abroad due to their low emissions and low noise.With the increase in the number of vehicles,road safety issues are becoming increasingly serious,and the stability control research of electric vehicles has become the focus of research.Among them,the four-wheel independent drive hub electric vehicle does not require an additional transmission device,and the motor used to drive/brake is embedded in the wheels,which can realize effective control of the four wheels.Therefore,this article chooses four-wheel independent drive hub electric vehicle as the research object.During the driving of the vehicle,the driving conditions will change,which will lead to changes in the structural parameters of the vehicle.Among these parameters,the tire cornering stiffness is one of the key parameters,which is closely related to the lateral force.It will be uncertain due to changes in its current state,such as tire slip angle,tire pressure,vertical load,and external factors such as road friction coefficient.When designing the vehicle stability control system,if the tire cornering stiffness is treated as a fixed value,there will be a large error with the actual engineering phenomenon.Therefore,in this paper,considering the uncertainty of cornering stiffness,the following studies are carried out on the stability control of electric vehicles:First,the selected research object is explained,a two-degree-of-freedom vehicle model is established,and a tire dynamics model and a motor torque tracking model are built at the same time.Secondly,in view of the problem of vehicle stability control,a hierarchical control architecture is adopted.The vehicle system is very complex,and there are internal coupling relationships,which have nonlinear characteristics.In a complex driving process,its internal parameters will change with changes in external conditions,including tire cornering stiffness.The cornering stiffness is an important parameter that characterizes the relationship between the coefficient of friction between the tire and the road surface.The change in the cornering stiffness will affect the stability of the vehicle.Therefore,it is necessary to consider the influence of the change in cornering stiffness on vehicle stability.The first is the design of the upper-level controller.Aiming at the problem of parameter uncertainty,the sliding mode controller has better control effects and robustness.However,the upper bound of the uncertain parameter needs to be determined.If the upper bound of the uncertainty cannot be clearly defined,the coefficient of the sign function term needs to be selected with a larger value.This choice can offset the uncertainty of the system,but the larger chattering phenomenon will be brought about Into the system,the control accuracy will also be affected.Aiming at the problem of parameter uncertainty,an adaptive sliding mode controller with an adaptive rate is designed to offset the influence of the uncertainty of the cornering stiffness through the adaptive rate.The lower-level controller is used to realize torque distribution.The expected yaw moment obtained by the upper-level sliding mode controller considering the uncertainty of the cornering stiffness is taken as the optimization objective and the minimum tire utilization rate is used as the optimization objective.Under the constraints,the quadratic programming algorithm is adopted.After solving optimization,it is allocated to four motors.Finally,a joint simulation platform was built through Carsim and Matlab/Simulink to conduct simulation experiments under different road friction coefficients and different speeds,and compare the sliding mode controller and the adaptive sliding mode controller under the condition of considering the uncertainty of tire cornering stiffness.The tracking control effect of the reference value of the state variable verifies the effectiveness of the adaptive sliding mode controller.