Active/Semi-Active Vibration Control And Application In Automobile Suspension System

With the development of advanced technology,various types of cars have become an important means of transportation in the modern life,and their requirements for comfort and safety are getting higher.As an extremely important part of the vehicle structure,the performance of the suspension system directly determines the damping effect.In the field of vehicle research,a large number of cars use passive suspension system which consists of the springs and the dampers.Passive suspension is mainly designed for specific road conditions and vehicle driving conditions,and the vibration characteristics are fixed.Hence passive suspension may not be unable to meet higher requirements for the vehicle overall performance,especially under the poor road conditions.Therefore,in order to solve the problem of passive suspension,some scholars put forward the active and semi-active suspension systems,which can monitor and control the vibration of the vehicle body in real time according to the running state of the vehicle,so that the vehicle can maintain a good running condition on different road conditions.Although the active and semi-active suspension system has great potential in vehicle vibration reduction,there are several difficult problems need to be solved.First,as a complex mechanical body,the simplified model of the suspension system needs to maintain the original mechanical motion mechanism.Second,the control strategy can heavily determine the suspension response of systems,which require to design a reasonable and effective controller.Third,since the cost of real vehicle test is too high,it is preferable to simulate the actual conditions in the road simulation and vehicle model modeling and control,and to improve the feasibility of the controller.This thesis addresses the above issues,and carries out in-depth analysis and research for the active and semi-active suspension systems.First of all,this thesis establishes the dynamic model of a quarter-active/semi-active suspension system,which the semi-active suspension system use MR damper as semi-active vibration device.At the same time,to ensure the authenticity of the road input,the road of the Carsim software is input into the system model.To obtain fast and high precision parameter estimation of suspension systems,an adaptive parameter estimation algorithm based on parameter error information is proposed,and an adaptive law is designed to accurately and quickly estimate the uncertain parameters in the system model.This method improves the performance of the active/semi-active suspension systems and achieves the purpose of suppressing vibrations while the suspension performance requirements are also ensured in the controller design process.The simulation results show that the proposed adaptive control algorithm is better than other control algorithm.Since the quarter-active/semi-active suspension model does not represent the performance of the whole vehicle during the running process,we further analyze the active and semi-active control of vehicle suspension systems.In order to make the characteristics of the vehicle model closer to the actual vehicle,we adopt a realistic vehicle model embedded in Carsim,which defines the characteristic parameters of the vehicle systems,and we then simulate the controller in MATLAB combining with Carsim.A new PPF(Prescribed performance function)control algorithm is proposed for guarantee the transient and steady performance of the suspension system.In the vertical,roll and pitch directions of the vehicle,this method can accurately prescribe the convergence rate,over-shoot,error and so on,and ensure the suspension system transient and steady-state response.Finally,according to the closed-loop simulation results based on the built simulator,we find that the performance of the control algorithm is better than other algorithms.This study finds that the active and semi-active suspension system effectively improves the ride comfort and driving safety of the passengers.Through the study of the active suspension system and the semi-active suspension system,we find that the active suspension has better control effect than the semi-active suspension,while the structure of semi-active suspension is simpler and the cost is lower.