Research On Optimal Control Strategy Of Vehicle Magnetorheological Semi Active Suspension System

In today’s era of rapid development of science and technology,the automobile industry will also be in the trend of comprehensive development,people put forward higher requirements for the power performance of the car at the same time,to ensure that the driving process always maintain comfort and stability is essential.As a result,the pursuit is now less about fuel economy and more about handling stability and driving safety.The automobile suspension system is directly related to the comfort and safety of the automobile driving,but also an important part of the automobile structure,the semi-active suspension has the advantages of simple structure,stable performance,low energy consumption,low cost,and so on.At the same time,combined with the intelligent control algorithm,the damping force of the suspension can be changed to achieve the desired damping effect.Due to low power consumption,fast response,variable damping force,low cost and simple manufacturing process,MRD is more suitable for semi-active suspension.In the research process,it is an important step to accurately establish the mathematical model of MRD,and the design of appropriate semi-active suspension control method is the necessary condition to achieve the ideal control effect.The research content of this paper is as follows:1.Establishment of MRD model.The composition of magnetorheological fluid,magnetorheological effects,rheological mechanisms and mechanical properties are described.The main analysis of the working mechanism and working mode of MRD are analysed in detail,and the characteristics of various types of MRD models are explained.A double outlet rod shear valve type MRD is designed and processed.tensile tests are carried out on the home-made MRD using the equipment available in the laboratory,and the variation of the mechanical properties of the MRD is derived.2.The parameters of the MRD model were identified.An improved hyperbolic tangent model was proposed for the hysteresis characteristics of MRD and applied to the non-linear dynamics analysis of MRD,and the unknown parameters were identified using genetic algorithm.Based on Simulink software,the dynamic response simulation model of MRD is constructed.The comparison between the experimental data and the simulated data indicates that the modified hypertangent model can describe the mechanical properties of the MRD exactly.At the same time,the MRD inverse model is built on the basis of BP neural network.,and by analysing its effectiveness,it provides a strong guarantee for the accuracy of the subsequent work.3.Modelling and dynamics characteristics of the vehicle magnetorheological semi-active suspension are studied.The root-mean-square method was used to make a comprehensive assessment of the vehicle suspension,with body droop acceleration,suspension dynamic travel and tyre dynamic displacement as comprehensive performance evaluation indicators.Based on the actual driving conditions,builds an impact road model,and models the random road surface with the filtered white noise method.At the same time,using Simulink platform,the model of1/4 vehicle suspension of two degrees of freedom is built and simulated.4.Simulation study with a magnetorheological semi-active suspension system for 1/4vehicles.Based on modern control theory,the LQG controller is designed to address the problems of low control accuracy,poor dynamic adjustability and difficult to determine the weight matrix coefficients of the LQG controller,etc.By combining intelligent control algorithms with modern control theory,an LQG controller based on gravitational search algorithm is proposed.Using the performance indexes of the suspension as the objective function,the gravitational search algorithm is used to optimise the weight matrix coefficients,and a simulation study of the magnetorheological semi-active suspension under GSA-LQG control is carried out on random and impact road surfaces.The results show that the GSA-LQG controller has a more desirable control effect compared with the LQG controller.5.Tests are carried out on a 1/4 vehicle magnetorheological suspension test rig.In order to verify the correctness of the above designed control strategy and to improve the credibility,a bench test platform for a 1/4 vehicle magnetorheological suspension was built.The passive control,LQG control and GSA-LQG control algorithms were compared and validated on a 1/4vehicle magnetorheological suspension test rig using an STM32 microcontroller as the controller.