Research On Control Strategy Of Semi-Active Suspension System Based On Magnetorheological Damper

With the continuous development of the automobile industry,people’s requirements for the performance,safety,and comfort of automobiles are gradually increasing,which also leads to higher and higher performance requirements for suspension systems.Compared with passive suspensions whose parameters such as damping and springs cannot be adjusted actively,semi-active suspensions use smart material technologies such as magnetorheological dampers(MRDs),which can automatically adjust the damping force according to road conditions and vehicle speed to improve driving comfortability,therefore,it has a promising application prospect in the vibration control of automobile suspension.In order to improve the suppression effect of magnetorheological semi-active suspension on vehicle vibration,this paper mainly aims at the problems of low accuracy of MRD model and poor control adaptability of semi-active suspension system,using theoretical analysis and model simulation methods,conducts research on the following aspects:(1)Carry out mechanical property test experiments and theoretical modeling on MRD.First,analyze the working principle of MRD,build a tensile test platform,and test the mechanical properties of MRD.Secondly,analyze the force-displacement and force-velocity relationship through the test results,select the hyperbolic tangent model to describe the mechanical characteristics of MRD,and use the combination of genetic algorithm and least square method to identify the model parameters,then according to the recognition results,the relationship between the parameters and the current is fitted to establish a positive model with strong generality.Finally,the adaptive neuro-fuzzy inference system(ANFIS)is used to generate the training data set with the forward model,and the inverse model of MRD is established.(2)Establish road model and semi-active suspension system model.Firstly,for the road surface with more complex road conditions,a relatively bumpy high-convex and pothole road surface model is established.Secondly,a relatively stable random road surface model is established by white noise filtering method,and then a two-degree-of-freedom model of passive suspension and semi-active suspension is established by taking the vertical motion of the vehicle as the research object.Finally,the evaluation index of suspension system performance is briefly described.(3)Design the PID controller and fuzzy PID controller of the semi-active suspension system.Firstly,the minimum vertical acceleration of the vehicle is taken as the control target,and the PID controller of the semi-active suspension system is designed.Then,aiming at the problem that the PID parameters cannot be adjusted in real time with the system state,the error of the control target and its change rate are tracked by using the fuzzy method,and the fuzzy rules are formulated according to the PID control principle to realize the real-time control of the PID parameters,to improve the adaptability of the suspension system to different road surfaces.Finally,the applicability of the controller is verified by model simulation.(4)Design sliding mode controller and fuzzy adaptive sliding mode controller for semiactive suspension system.Firstly,taking the vehicle’s vertical velocity and displacement as the error vector,a sliding mode controller for the semi-active suspension system is designed,and the exponential reaching law method is used to suppress chattering.Then according to the nature of the sliding mode motion,the fuzzy rules are designed with the sliding mode motion state as a reference,and the fuzzy controller is used to realize the adaptive adjustment of the reaching law parameters to improve the response speed and stability of the suspension system.Finally,the validity of the control strategy is verified by model simulation.