Intelligent Control Of Semi-active Suspension Of Off-road Vehicles

Vehicle systems are complex dynamic systems.Vibration caused by road excitation is transmitted to the occupants through the vehicle body.Which has very serious impact on the riding comfort of the occupants.It will affects working ability of the occupants even threatens their physical health.Especially for off-road vehicles driving on complex roads for a long time,its vehicle mobility and off-road performance will become worse.Therefore,in the field of vehicle engineering,reducing the impact of vibration on passengers is an urgent problem.Suspension system as a link between the human body and the vehicle,it plays a very important role in reducing the vibration transmitted from the vehicle to the passengers.This thesis mainly puts forward an adjustable magnetorheological damper and corresponding semi-active suspension system.Finally,the control strategy of the semi-active suspension was simulated.This thesis details the rheological properties of magnetorheological fluids and working principle of damper.Bouc-Wen model is modeled and simulated.This thesis also analyzes the effects of different factors such as current,excitation speed,and excitation frequency on the damping force.Semi-active suspension model is built based on this damper.It was simulated in MATLAB/Simulink.This thesis analyzes the impact of model parameters on the amplitude-frequency characteristics of the system.Which provides theoretical basis for suspension system design.This thesis also focuses on the control strategy of semi-active suspension.Based on the quarter semi-active suspension model,designs H_∞guaranteed output feedback control law and state feedback control law with lyapunov theory.Considering the response delay(input time delay)of the magnetorheological damper in a semi-active suspension,controllers are designed to reduce negative effects of input time delay on suspension system.This problem is transformed into a convex optimization problem of LMI for solving.This thesis presents a robust H_∞control method based on time delay.Incorporats delay conditions into Lyapunov-Krasovskii and solves the controller problems.