avhandling marro 2007/01/14 20:34phd_andjo page2005/08/17 iii 13:51 page 1 Link¨oping Studies in Science and Technology. Dissertations Linköping StudiesNo. in Science1068 and Technology. Marcus Rösth Dissertations No.1068 965 DesignHydraulic Principles Power Steering for Noise System Reduction Design in in HydraulicHydraulicRoad Power PistonVehicles Steering Pumps SystemSimulation,Analysis, Optimisation Design Testing and in andEnhanced Road Experimental Functionality Vehicles Verification Analysis, TestingarcuMarcuss andRs Enhancedth Rösth Functionality RoadVehicles Hydraulic Power Steering System Design in Marcus R¨osth Linköping 2005 Hydraulic Piston Pumps Design Principles for NoiseAndreas Reduction Johansson in Division of Fluid and Mechanical Engineering Systems Department of Mechanical Engineering Division of FluidLink and¨oping Mechanical University Engineering Systems DepartmentSE–581 83 of Link Mechanical¨oping, Sweden Engineering 2007 Linköpings universitet SE–581 83 Linköping, Sweden Link¨oping 2007 Linköping 2005 August 17, 2005 1 avhandling marro 2007/03/07 20:41 page i Hydraulic Power Steering System Design in Road Vehicles Analysis, Testing and Enhanced Functionality avhandling marro 2007/03/07 20:41 page ii avhandling marro 2007/03/07 20:41 page iii Link¨oping Studies in Science and Technology. Dissertations No. 1068 Hydraulic Power Steering System Design in Road Vehicles Analysis, Testing and Enhanced Functionality Marcus R¨osth Division of Fluid and Mechanical Engineering Systems Department of Mechanical Engineering Link¨oping University SE–581 83 Link¨oping, Sweden Link¨oping 2007 avhandling marro 2007/03/07 20:41 page iv ISBN 978-91-85643-00-4 ISSN 0345-7524 Copyright c 2006 by Marcus R¨osth Department of Mechanical Engineering Link¨oping University SE-581 83 Link¨oping, Sweden Printed in Sweden by LTAB Link¨opings Tryckeri AB, 2007.445 avhandling marro 2007/03/07 20:41 page v To my wife Jennifer M¨angden tror att allt sv˚arfattligt ¨ar djupsinnigt, men s˚a ¨ar det icke. Det sv˚arfattliga ¨ar det ofull- g˚angna, oklara, och ofta det falska. Den h¨ogsta vis- domen ¨ar enkel, klar, och g˚ar rakt genom skallen i hj¨artat. August Strindberg, 1908, ”En ny bl˚a bok” avhandling marro 2007/03/07 20:41 page vi avhandling marro 2007/03/07 20:41 page vii Abstract Demands for including more functions such as haptic guiding in power steering systems in road vehicles have increased with requirements on new active safety and comfort systems. Active safety systems, which have been proven to have a positive effect on overall vehicle safety, refer to systems that give the driver assistance in more and less critical situations to avoid accidents. Active safety features are going to play an increasingly important roll in future safety strategies; therefore, it is essential that sub systems in road vehicles, such as power steering systems, are adjusted to meet new demands. The traditional Hydraulic Power Assisted Steering, HPAS, system, cannot meet these new demands, due to the control unit’s pure hydro-mechanical so- lution. The Active Pinion concept presented in this thesis is a novel concept for controlling the steering wheel torque in future active safety and comfort applications. The concept, which can be seen as a modular add-on added to a traditional HPAS system, introduces an additional degree of freedom to the control unit. Different control modes used to meet the demands of new func- tionality applications are presented and tested in a hardware-in-the-loop test rig. This thesis also covers various aspects of hydraulic power assisted steering systems in road vehicles. Power steering is viewed as a dynamic system and is investigated with linear and non-linear modeling techniques. The valve design in terms of area gradient is essential for the function of the HPAS system; therefore, a method involving optimization has been developed to determine the valve characteristic. The method uses static measurements as a base for calculation and optimization; the results are used in both linear and the non- linear models. With the help of the linear model, relevant transfer functions and the underlying control structure of the power steering system have been derived and analyzed. The non-linear model has been used in concept validation of the Active Pinion. Apart from concept validation and controller design of the active pinion, the models have been proven effective to explain dynamic phenomena related to HPAS systems, such as the chattering phenomena and hydraulic lag. vii avhandling marro 2007/03/07 20:41 page viii viii avhandling marro 2007/03/07 20:41 page ix Acknowledgements The work presented in this thesis has been carried out at the Division of Fluid and Mechanical Engineering Systems at Link¨oping University and has been financed by ProViking and Volvo Car Corporation. There are a great number of people that I would like to mention. First of all, I would like to thank my supervisor and head of the division, Prof. Jan-Ove Palmberg, for his support and outstanding ability to come up with new ideas. I would also like to give special thanks to my industrial supervisor and co-author of the three appended papers Dr. Jochen Pohl, Volvo Car Corporation, for inspiring discussions and optimism. I do not want to forget Prof. Karl-Erik Rydberg, who is always available for short intensive discussions, which are of great importance. Many thanks to all members and former members of the Division of Fluid and Mechanical Engineering Systems for more and less serious discussions in between work, which are an important part of the research process called brainstorming. I owe many thanks to Anders Zachrison for his invaluable help throughout the research process. Many other people have also been involved in research not necessarily presented in this thesis: P¨ar Degerman, Andreas Jo- hansson, Ronnie Werndin, Johan Olvander,¨ Andreas Renberg, Cristian Dumb- rava and Sten Ragnhult. I would also like to mention the technical staff at the Department of Me- chanical Engineering and thank them for invaluable help with the prototype design and the manufacturing of the Active Pinion and Power Steering Test Rig; a special thanks to Ulf Bengtsson, Thorvald ”Tosse” Thoor and Magnus ”Mankan” Widholm. Finally, I would like to thank my wife Jennifer, who has held my hand throughout the entire process and put up with my on occasion absent- mindedness, and my family, Leif, Siv and Kristina, for their great support during the years. Link¨oping in December, 2006 Marcus R¨osth ix avhandling marro 2007/03/07 20:41 page x x avhandling marro 2007/03/07 20:41 page 1 Papers The following six papers are appended and will be referred to by their Roman numerals. All papers are printed in their originally published state with the exception of minor errata and changes in text and figure layout. In papers [II, IV, V], the first author is the main author, responsible for the work presented, with additional support from other co-authors. In paper [III, VI], the work is equally divided between the first two authors, with additional support from other co-authors. Paper [I] is submitted for publication at the 10th Scandinavian International Conference on Fluid Power, SICFP’07, in the Tampere, Finland. [I] Rosth¨ M. and Palmberg J-O., “Robust Design of a Power Steer- ing Systems with Emphasis on Chattering Phenomena” Submitted and accepted to The 10th Scandinavian International Conference on Fluid Power, SICFP’07, Tampere, Finland, 21th–23th May, 2007. [II] Rosth¨ M. and Palmberg J-O., “Modeling and Validation of Power Steering System With Emphasis on Catch-Up Effect,” in Proc. of The 9th Scandinavian International Conference on Fluid Power, SICFP’05, (Eds. J-O Palmberg), CD publication, Link¨oping University (LIU) Print, Link¨oping, Sweden, 1st–3rd June, 2005. [III] Rosth¨ M., Pohl J. and Palmberg J-O., “Modeling and Simulation of a Conventional Hydraulic Power Steering System for Passenger Cars,”in Proc. of The 8th Scandinavian International Conference on Fluid Power, SICFP’03, (Eds. K.T. Koskinen and M. Vilenius), pp. 635–650, vol. 1, Tampere University of Technology (TUT) Print, Tampere, Finland, 7th– 9th May, 2003. [IV] Rosth¨ M., Pohl J. and Palmberg J-O., “Active Pinion - A Cost Effective Solution for Enabling Steering Intervention in Road Vehicles,” Submitted and accepted to The Bath Workshop on Power Transmis- sion & Motion Control, PTMC’03, Bath, United Kingdom, 10th-12th September, 2003. 1 avhandling marro 2007/03/07 20:41 page 2 [V] Rosth¨ M., Pohl J. and Palmberg J-O., “Increased Hydraulic Power Assisted Steering Functionality Using the Active Pinion Concept,” in Proc. of 5th International Fluid Power Conference Aachen, IFK2006, Aachen, Germany, 20th-22nd March, 2006. [VI] Rosth¨ M., Pohl J. and Palmberg J-O., “Parking System Demands on the Steering Actuator,” in Proc. of ASME 2006 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, ESDA 2006, Torino, Italy, 4th-7th July, 2006. Papers not included The following papers are not included in the thesis but constitute an important part of the background. Paper [X] is a working paper. [VII] Degerman P., Rosth¨ M. and Palmberg J-O., “A Full Four- Quadrant Hydraulic Steering Actuator Applied to a Fully Automatic Passenger Vehicle Parking System,” in Proc. of Fluid Power Net In- ternational - PhD Symposium , 4th FPNI-PhD 2006, CD-Publication, Sarasota, FL, USA, 13th-17th July, 2006. [VIII] Zachrison A., Rosth¨ M., Andersson A. and Werndin R.,“Evolve – A Vehicle-Based Test Platform for Active Rear Axle Camber and Steering Control” in Journal of SAE TRANSACTIONS, pp 690–695, vol. 112, part 6, USA, 2003. [IX] Rosth¨ M., Pohl J. and Palmberg J-O., “Linear Analysis of a Con- ventional Power Steering System for Passenger Cars,” in Proc. of The 5th JFPS International Symposium on Fluid Power, (Eds.