Research On Control Of Electric Vehicle Suspention System With Fractional-order Driven By In-wheel Motors

Hub motor drive electric vehicle has many advantages,such as high transmission efficiency,good controllability and so on,so it will be widely used.The unsprung mass of the wheel motor increases significantly,which not only worsens the ride comfort of the vehicle,but also affects the handling stability of the vehicle;the deterioration of the tire grounding performance not only impacts the wheel motor,but also affects the driving safety of the electric vehicle.In the process of driving,due to the random excitation of the road and the change of driving conditions,the vehicle produces strong vibration,which affects the handling stability and driving safety of the vehicle.Therefore,it is necessary to optimize and design the parameters of the suspension system,and study the effective active control strategy,which is of great significance to improve the driving safety,handling stability and riding comfort.In this paper,based on the suspension model of electric vehicle with fractional wheel hub motor,the passive control of suspension system and the active suspension controlled by sliding mode are simulated and analyzed.The research contents of this paper are as follows:Firstly,The hub motor is elastically isolated from the spring mass and parallel to the spring mass.The vibration isolation material is built between the tire and the motor to reduce the influence of the road excitation on the motor and to improve the deterioration of the road excitation and electromagnetic excitation.A three degree of freedom nonlinear suspension system model with fractional order is established.According to the definition and properties of fractional calculus,the high-order integer order transfer function model is used to approximate the fractional differential operator,and the influence of the increase of unsprung mass on the performance of suspension system is simulated and analyzed.Secondly,taking the electric vehicle suspension with vibration isolation material as the research object,the particle group algorithm and the genetic algorithm were optimized,comparing the root mean square value of the vertical acceleration,suspension deflection,tire load and motor vertical acceleration of different optimization algorithms.Then,the linear optimal active control suspension model is selected as the reference model,the error equation is written between the controlled model and the reference model,and the switching surface function is designed to realize the sliding mode motion of the system,and the fractional exponential reaching law similar to the exponential reaching law is constructed to obtain the active control rate.The simulation results show that the model following variable structure control model can track the selected reference model,and the fractional exponential reaching law is better than the integer exponential reaching law in stability and chattering reduction.