C. LAUWERYS, Control of active and semi-active suspension systems for passenger cars, 2005

Abstract

This thesis deals with the design of controllers for active and semi-active suspension systems for passenger cars. The focus is on simple yet efficient design approaches, that lead to flexible and intuitively tunable control structures. The thesis mainly consists of thwo parts: the modeling, identification and control of a prototype of an active suspension system recently developed by Tenneco Automotive, in a quarter car test rig, and the design and tuning of a flexible control structure for a semi-active suspension system of a real car.

The aim of the control design for the active suspension is to compare the performance that can be achieved with this new system, with the performace of a standard passive shock absorber. The control design methods applied involve an inner loop to linearize the system, and an outer linear control loop to improve the system dynamics. The inner loop linearization is based on a nonlinear input transformation. The outer loop is designed using both classical methods, such as loop shaping and LQG, as well as robust control design methods based on H_∞ and μ-synthesis.

In a second part of this thesis, a flexible and transparent control structure is developed for a complete semi-active suspension system, aiming to improve comfort and handling characteristics of a real car. In order to avoid designing a complete dynamic car model, a model free control structure is proposed, which is derived from physical insights in the car and semi-active shock absorber dynamics. This approach leads to a controller with a limited number of physically interpretable parameters that can be tuned online based on the comments of an experienced test-pilot as he/she drives the car over calibrated test-tracks. Parameter adaption mechanisms and nonlinear gains introduced in the control structure lead to extra flexibility required to fine tune the behavior of the car for a wide range of road excitations and handling events.

Both parts of this research are performed in cooperation with Tenneco Automotive Europe (St-Truiden, Belgium).

Order Code

Code: 05D4