Research On Control Strategy Of Electric Vehicle Compound Regenerative Braking System Based On MRPP

With the increasingly prominent problems of air pollution and energy depletion,the production of electric vehicles with zero emissions,high efficiency and low noise has become a development trend in the automotive industry.However,electric vehicles still have technical shortcomings such as insufficient battery life,poor braking safety and long charging time.Regenerative braking technology is one of the effective ways to improve the battery life of electric vehicles,especially in urban conditions.This thesis takes the problems of insufficient braking energy recovery and poor braking performance of the traditional regenerative braking system as the breakthrough point,and based on the maximum regenerative power point(MRPP)of permanent magnet synchronous motor,a layered control strategy for composite regenerative braking system is proposed.This control strategy utilizes the maximum feedback power under normal braking conditions and emergency braking conditions,and ensures the braking stability and safety of the compound braking system.This thesis firstly analyzes the principle of permanent magnet synchronous motor regenerative braking,and then defines the permanent magnet synchronous motor MRPP through the motor mathematical model,and finally verifies the feasibility and realization conditions of MRPP.In order to clarify the regenerative braking limit of the permanent magnet synchronous motor,I conducted relevant research on the MRPP-based regenerative braking torque limit curve,and designed the dynamic parameters of the four-wheel hub electric vehicle.In addition,in order to achieve the maximum regenerative power under normal braking conditions,I used the MRPP regenerative braking torque distribution strategy.For the problem of low motor regenerative power under low braking intensity,I proposed a 5-segment front and rear axle Brake torque distribution strategy.This strategy improves the motor feedback power by reducing the number of motors involved in the braking process,and finally achieves the maximum feedback power under low braking intensity.In order to further expand the working range of the motor regenerative braking mode,I propose a "big front and small back" drive scheme.Combined with the two distribution strategies under normal operating conditions,I propose a regenerative braking control strategy based on sliding mode control theory,so as to effectively achieve driver braking command tracking and maximize braking energy recovery.Aiming at the problem of poor braking stability of the braking system under emergency braking conditions,I adopted the optimal slip rate control algorithm based on sliding mode control theory,which effectively achieved optimal slip rate tracking.And in order to ensure the stability and real-time performance of the composite regenerative braking system,I use the extended state observer to estimate the road-tire friction.At the same time,I use the MRPP regenerative braking torque distribution strategy to achieve the maximum feedback power under emergency braking conditions.Finally,combined with the proposed regenerative braking control strategies under the two braking conditions,I designed a layered control strategy for the composite regenerative braking system.Through co-simulation,the effectiveness of the control strategy of the designed compound regenerative braking system under different working conditions is successfully verified.