Abstract
The main functions of vehicle suspension system are to minimize the vertical acceleration transmitted to the passengers to provide ride comfort and to maintain the tire-road contact to provide holding characteristic, and to keep the suspension travel small. In general, only a compromise between these two conflicting criteria can be obtained if the suspension is built from passive components. The answer to this problem seems to be found in the development of an active or semi-active suspension system. With semi-active suspension we can prevent bounce, pitch and roll in road disturbances. Furthermore, these systems can improve comfort considerably by the ability to control the vibrations of the sprung mass and vehicle body in an active way. It is a well-known fact that the derivation of the control needs the vehicle dynamics to be accurately expressed as a linear model, whereas the vehicle dynamics generally includes nonlinearities and uncertainties. For the design of active suspension systems for such models, the use of optimal control methods has been proposed, and it has shown satisfactory performance. In the present study, LQR controller was considered to control a semi-active suspension. The main targets are the elimination of body bounce and pitch in normal ride and roll attitude as well as its bounce resulting from road bumps, on individual tires by using suspension system in both sides of the car and both axles. Moreover, in order to have the ability to interpret the results of full model of vehicle in ADAMS, the method of crawl and walk and the simple models with lower degrees of freedom were used. The hydraulic actuator dynamics is also included. The controller structure was designed in MATLAB/Simulink. The full process was implemented using link between ADAMS as a Multi-Body Dynamics Simulator & MATLAB as a control simulation environment.
Keywords: active suspensions, vehicle, optimization, simulation