Abstract olsson, c. 2005. Active Vibration control of Multibody Systems. Application to Automotive Design. Acta Universitatis Upsaliensis. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 59. 35 pp. Uppsala. ISBN 91Y554Y6267Y7.

Active vibration control to reduce vibrations and structure borne noise is considered using a powerful multiYdisciplinary virtual design environment which enables control system design to be considered as an integral part of the overall vehicle design. The main application studied is active automotive engine vibration isolation where, first, the potential of large frequency band multiYinput multiYoutput H2 feedback control is considered. Facilitated by the virtual environment, it is found necessary to take nonYlinear characteristics into account to achieve closedYloop stability. A physical explanation to why receiver structure flexibility insignificantly affect the open and closedYloop characteristics in case of total force feedback in contrast to acceleration feedback is then given. In this context, the inherent differences between model order reduction by modal and by balanced truncation are being stressed. Next, applying stateYofYtheYart algorithms for recursive parameter estimation, timeYdomain adaptive filtering is shown to lack sufficient tracking performance to deal with multiple spectral components of transient engine excitations corresponding to rapid car accelerations. Finally, plant nonYlinearity as well as transient excitation are successfully handled using narrow band control based on feedback of disturbance states estimates. To deal with the nonYlinear characteristics, an approach to generate linear parameter varying descriptions of nonYlinear systems is proposed. Parameter dependent quadratic stability is assessed using a derived affine closedYloop system representation. This thesis also considers actuator saturation induced limit cycles for observerYbased state feedback control systems encountered when dealing with the active isolation application. It is stressed that the fundamental observerYbased antiYwindup technique could imply severely deteriorated closedYloop characteristics and even sustained oscillations. That is in the case when the observer is fed by the saturated control signal in contrast to the computed one. Based on piecewise affine system descriptions, analytical tools to conclude about limit cycles and exponential closedYloop stability are provided for the two observer implementations.