On non-linear unknown input observers–applied to lateral vehicle velocity estimation on banked roads

Unknown input observers (UIOs) are observers that have stable error dynamics that are independent of unknown inputs. This paper studies such observers for non-linear systems, and shows that the error dynamics for a non-linear UIO has the same structure as the error dynamics of a non-linear observer without unknown inputs. This result is first used to provide synthesis inequalities for UIOs for a class of non-linear systems, and secondly, to inspire the design of an observer for estimation of vehicle lateral velocity on banked roads. Acknowledgements We gratefully acknowledge DaimlerChrysler (Dr. Jens C. Kalkkuhl and Mr. Avshalom Suissa) for discussions and for supplying measurement series and vehicle data for the results in § 5.1. The research is supported by the European Commission STREP project CEMACS, contract 004175.