research @ wolfgang-reinelt.de	modeling, control & safety of active steering systems

Active front steering is a newly developed technology for passenger cars that realises an electronically controlled superposition of an angle to the hand steering wheel angle that is prescribed by the driver. The driver controls the vehicles course via the hand steering wheel. Active front steering actuates an additional angleusing its electric motor. Both angles result in an pinion angle down at the steering rack. The resulting (average) road wheel angle can then be calculated via the pinion angle and a static nonlinearity that accounts for the relation between pinion angle and rack displacement as well as for the steering geometry. Having this basic framework at hand, one can start looking at functions that manipulate the motor angle in order to e.g. achieve a desired overall steering ratio that depends on vehicle speed and pinion angle. This desired motor angle will then be passed to the motor's feedback control algorithm. Details on the system setup, its functionality and components as well as connection to other chassis systems have been published in

• C. Lundquist, W. Reinelt and O. Enqvist. Back driving assistant for passenger cars with trailer. In Proc. of the SAE World Congress. Detroit, MI, USA, April 2006. SAE paper 2006-01-0600.
• W. Klier, G. Reiman and, W. Reinelt. Concept and Functionality of the Active Front Steering System. In Proc. of the Convergence. SAE paper 2004-21-0073. Detroit, MI, USA, October 2004. Invited Contribution.

Some more details on the mathematical modelling an parameter estimation are given in

• W. Reinelt und C. Lundquist. Kapitel: "Mechatronische Lenksysteme: Modellbildung und Funktionalität des Active Front Steering". In Fahrdynamik Regelung - Modellbildung, Fahrassistenzsysteme, Mechatronik (Rolf Isermann, Editor). Vieweg Verlag, September 2006. ISBN 3-8348-0109-7.
• W. Reinelt, W. Klier, G. Reimann, C. Lundquist, W. Schuster and R. Großheim. Active Front Steering for Passenger Cars: System Modelling and Functions. In Proc. of the First IFAC Symposium on Advances in Automotive Control, Salerno, Italy. Apr 2004.

A great deal of functionality that is housed in the electronic control unit is devoted to ensure the overall functional safety of the system. Some general information and overview on system safety are published in

• W. Reinelt, W. Klier und G. Reimann. Systemsicherheit des Active Front Steering. at - Automatisierungstechnik, 53(1):36-43, January 2005. Invited Contribution.
• W. Reinelt, W. Klier, G. Reimann, W. Schuster and R. Großheim. Active Front Steering (part 2): safety and functionality. In Proc. of the SAE World Congress. Detroit, MI, USA, March 2004. SAE paper 2004-01-1101.

Developing such a safety related system properly asks for a safety related development process along with traceble risk assessment from vehicle to component level. This has been described in

• W. Reinelt and C. Lundquist. Chapter: "Controllability of active steering system hazards: From standards to driving tests". In Safety Critical Automotive Systems (Juan R. Pimintel, Editor), pages 173-178. SAE International, 400 Commonwealth Drive, Warrendale, PA, USA, August 2006. ISBN 13:978-0-7680-1243-9.
• A. Neukum und W. Reinelt. Integration des Fahrers bei der Bewertung der Ausfallsicherheit aktiver Lenksysteme. In VDI-Tagung Der Fahrer im 21. Jahrhundert. VDI-Bericht Nr. 1919, S.161-176. Braunschweig, Germany, November 2005.
• W. Reinelt and A. Krautstrunk. Safety related development process for electronic steering systems. In Proc. of the SAE World Congress. Detroit, MI, USA, April 2005. SAE paper 2005-01-0780.

The technical safety concept demands diagnoses of a certain level for safety related components. E.g., beyond usual sensor diagnosis such as analogue signal monitoring, test patterns etc (all of them described in recognised safety standards), more advanced methods are needed in order to detect sensor failures of certain types or in certain situations. This can be handeled using change/fault detection algorithms described in

• S. Malinen, C. Lundquist and W. Reinelt. Fault detection of a steering wheel angle sensor in an active steering system. In Preprints of the IFAC Symposium SAFEPROCESS, pages 547-552. Beijing, China, August 2006.
• W. Reinelt and C. Lundquist. Observer based sensor monitoring in an active front steering system using explicit sensor failure modeling. In Preprints of the 16th IFAC World Congress. Prague, Czech Republic, July 2005. Invited contribution.
• W. Reinelt, C. Lundquist, H. Johansson. On-line sensor monitoring in an Active Front Steering System using Extended Kalman Filtering. In Proc. of the SAE World Congress. Detroit, MI, USA, April 2005. SAE paper 2005-01-1271.

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Last update: Mon May 7 20:57:36 2007 by Wolfgang Reinelt . Legal Disclaimer