LPV based robust H∞ control of vehicle vibrations

Conventional passive suspension systems that employ a spring and damper between the carbody and wheel assembly represent a tradeoff between performance metrics such as passengercomfort, road holding and suspension deflection.Research activities in control design for active suspension systems which would beimplemented by adding an actuator controlled by feedback into passive suspensions areintensively continuing in both trading area and academic area.In this thesis, titled ?LPV Based Robust H∞ Control of Vehicle Vibrations?, a linearparameter varying (LPV) based H∞ controller which is sensitive to the body mass variationsand which stiffens on bad road conditions is designed.In chapter one, a general literature research in matter of active suspension control is fulfilled.In chapter two, how performance metrics are influenced by nonlinearities and parameteruncertainties in the models is investigates. In chapter three, firstly, the basics of H∞ controlare given. Then H∞ and Kalman Filter Based (KFB) controller are designed for quarter carmodel. At the end of the chapter, it is seen that H∞ controller gave very good results in spite ofthe changes of body mass. In chapter four, parameter-dependent weighting functions are usedto design active suspensions that stiffen as the suspension limits are reached for quarter carmodel. In chapter five, three different assembly strategies are considered in a half car model.Firstly, active suspension assembly which is mounted only to the driver seat, then the activesuspension assemblies which are mounted between the wheels and the car body. And finally atopology which includes both active wheel and active seat assemblies is considered. At theend of the chapter five, if one considers the cost performance relations, it is concluded thatsuspension topology that only includes active components on the wheels is the best structure.In chapter six, firstly, LPV full car model which is body mass varying is considered in isestablished as an original control strategy. Then LPV based H∞ controller which is stiffened inbad road conditions is designed. At the end of the chapter six, LPV based H∞ controller isapplied to nonlinear full car model and simulated in various load conditions and roadconditions.At the end of the thesis, according to passenger comfort and suspension deflectionperformance metrics, the LPV controller?s performance and good improvements in closedloop responses compared to passive system responses are discussed.Keywords: Vehicle vibrations, H∞ control, LPV control, Nonlinear control, LQG controller,Suspension systems, Automotive