ICNPAA 2010: Mathematical Problems in
Engineering, Aerospace and Sciences

In this paper two control strategies are addressed - the Linear Quadratic Regulator (LQR) and the Internal Model Control (IMC). These techniques were tested in a system where saturation is present, the semi-active suspension problem. They are then evaluated by some performance indexes that characterize the problem as optimization problems, and solved by the use of some specific tools of the MATLAB software. The main goal is to obtain optimal performance, in order to minimize the sprung mass (chassis) acceleration and to ensure road-holding characteristics, while minimizing the number of feedback sensors used. To make-up for the minimum sensor usage, state observers are designed. A comparison is then made, by means of numerical simulation, using a quarter-car model and real road profiles as well.