This thesis deals with the modeling, control and estimation of semi-active automotive suspensions in order to improve the comfort and roadholding level of the vehicles. The main contribution is a complete observer and controller design methodology, allowing to improve the performance of the vehicle while using a reduced number of sensors. The proposed strategy is based on an observer, a main controller, and local controllers for each suspension. The controllers and observers are synthesized to take the actuators limitations and their bandwidth into account. The H? synthesis method, applied to Linear Parameter Varying (LPV) systems is used to develop the controllers. This formulation, applied to the damper models, allow to take their nonlinearities into account during the synthesis. Furthermore, the H? method suits this application, since the suspensions performance specifications are generally given in the frequency domain. Various experimental results are given and commented for the observer, and some simulations are presented for the vehicle controllers.