Research On Control Strategy Of Vehicle Magnetorheological Semi Active Suspension System

With the development of economy and the progress of science and technology,people’s quality of life has gradually improved and cars have become a necessary travel tool.At the same time,the dirving comfort of the vehicle have become the focus of people’s attention,among which suspension which can restrain the vibration of the vehicle plays an important role.Magnetorheological damper(MRD)is a new intelligent vibration isolation device.It has many advantages,such as low energy consumption,fast response,adjustable output,low price,simple manufacturing process and good damping effect,etc.Due to the high manufacturing cost of the active suspension,it replaces the damping elements and air springs of the passive suspension with the active actuator,which leads to energy consumption increase,and researchers at home and abroad have not solved this problem.Therefore,the semi-active suspension based on MR damper has just solved the defects of passive suspension and active suspension,which makes the research of semi-active suspension become a hot spot at home and abroad.Based on this,this paper takes air suspension system as the research object,and carries out the following research:1.The principle of MR fluid and MR damper is described.On this basis,a double rod MR damper with shear valve mode was designed and fabricated.The vibration test system of damping suspension was built,and the performance of damper was tested and analyzed.The forward dynamic model of MR damper was summarized in detail,and the modified hyperbolic tangent model was selected.The parameters of the model were identified by genetic algorithm,and the agreement between the identification results and the experimental data was compared,which manifests the the modified hyperbolic tangent model can be used in the subsequent semi-active control.The ANFIS was adopted to construct the inverse model of MR damper and its effectiveness was verified by simulation.2.Considering the actual vehicle driving conditions,the input models of random pavement and impact pavement were established respectively.The stiffness of air spring was modeled,and the air suspension model of 1/4 vehicle was established.The dynamic characteristics in time domain were obtained by simulation.At the same time,the transfer function of suspension performance index was obtained by Laplace transformation of air suspension model.The influence of suspension damping,suspension stiffness and tire stiffness on the damping effect is analyzed by using amplitude frequency characteristic curve.3.The fuzzy PID controller was designed combining the MRF damper model and air suspension model.In fuzzy PID control strategy,the tuning of parameters of PID controller was complex and the fuzzy rules were uncertain.A fuzzy PID switch switching control strategy(FPSC)was proposed.When the error is small,PID control can reduce the overshoot of the system and make the system stable as soon as possible;when the error is large,fuzzy control can obtain good dynamic characteristics,so as to improve the control effect of semi-active suspension.Finally,through the time-domain and frequency-domain simulation under random road surface and the time-domain simulation analysis under impact road surface,it can be seen that fuzzy PID controller and fuzzy PID switch switching control strategy can effectively improve the performance of suspension,and fuzzy PID switch switching control strategy has better effect.In addition,based on the ANFIS inverse model of MR damper,the sliding mode controller is designed.Aiming at the chattering phenomenon of sliding mode variable structure control,the fuzzy control strategy is introduced and the fuzzy sliding mode controller is designed.Through the simulation analysis in time domain and frequency domain under random road surface,it can be seen that the combination of fuzzy control and sliding mode variable structure control can effectively suppress the influence of chattering on control accuracy and ensure the stability of the system.Finally,the comparison and analysis of the four control algorithms show that the proposed fuzzy PID switch switching control and fuzzy SMC are better than the conventional fuzzy PID and sliding mode control in suspension damping effect.