OPTIMAL CONTROLLER DESIGN FOR ACTIVE SUSPENSION SYSTEM ON CARS

Abstract

Suspension system is one of the most important parts when designing a car, playing a key element in comfort of drivers and passengers (comfort criteria) and keep the contact of the tyres with road surface (road holding criteria). This paper presents a two-degree-of-freedom quarter car model using active suspension system with two optimal controllers: Linear Quadratic Regulator and Linear Quadratic Gaussian. By using the Kalman-Bucy observer, the number of sensors used to measure the input signals of the linear quadratic regulator controller has been minimized to only conventional sensors such as the sprung mass acceleration. In order to evaluate the effectiveness, the comfort and road holding criteria when using those controllers are compared to the case of the passive suspension system through the sprung mass displacement and its acceleration. The simulation results clearly show that the root mean square value of the sprung mass acceleration with the linear quadratic regulator, linear quadratic gaussian controllers has been reduced by about 20% when compared to a car using a passive suspension system.