40 Int. J. Modelling, Identification and Control, Vol. 6, No. 1, 2009 Copyright © 2009 Inderscience Enterprises Ltd. The modelling and estimation of driving forces for unmanned ground vehicles in outdoor terrain Lakmal Seneviratne, Yahya Zweiri, Suksun Hutangkabodee, Zibin Song, Xiaojing Song, Savan Chhaniyara, Said Al-Milli and Kaspar Althoefer* Department of Mechanical Engineering, King’s College London, Strand, London WC2R 2LS, UK E-mail: lakmal.seneviratne@kcl.ac.uk E-mail: yahya.zweiri@kcl.ac.uk E-mail: suksun.hutangkabodee@kcl.ac.uk E-mail: songzibinmaya@yahoo.co.uk E-mail: song.xiaojing@kcl.ac.uk E-mail: savan.chhaniyara@kcl.ac.uk E-mail: said.al-milli@kcl.ac.uk E-mail: k.althoefer@kcl.ac.uk *Corresponding author Abstract: Ground vehicles traversing rough unknown terrain has many applications in a range of industries including agriculture, defence, mining, space exploration and construction. The interaction dynamics between the vehicle and the terrain play a crucial role in determining the mobility characteristics of the vehicle. The two critical parameters that influence the interaction dynamics are the wheel/track slip and the unknown soil parameters. An algorithm for identifying unknown soil parameters based on a dynamic model and sensor feedback is presented. A method for estimating vehicle slip parameters based on an optical flow algorithm and a sliding mode observer is also presented. The last section addresses the traversability prediction for tracked vehicles traversing in circular trajectories. The algorithms are developed for both tracked and wheeled vehicles. The algorithms are tested and evaluated using two specially designed test rigs, and the test results are presented in the paper. Keywords: unmanned ground vehicles; modelling; soil parameter; identification; estimation; driving force prediction; sliding mode observer; optical flow; vision; traversability prediction; vehicle-terrain interactions; unknown terrain. Reference to this paper should be made as follows: Seneviratne, L., Zweiri, Y., Hutangkabodee, S., Song, Z., Song, X., Chhaniyara, S., Al-Milli, S. and Althoefer, K. (2009) ‘The modelling and estimation of driving forces for unmanned ground vehicles in outdoor terrain’, Int. J. Modelling, Identification and Control, Vol. 6, No. 1, pp.40–50. Biographical notes: Lakmal D. Seneviratne received his BSc (Eng.) and PhD in Mechanical Engineering from King’s College London, London, UK. He is currently a Professor of Mechatronics at King’s College London and also the Director of the Centre for Mechatronics and Manufacturing Systems. His research interests include robotics and intelligent autonomous systems. He has published over 175 refereed research papers related to mechatronics. He is a Fellow of both the IET and the IMechE and a member of the IEEE. Yahya H. Zweiri obtained a BSc in Mechanical Engineering from the University of Jordan, Jordan and a PhD in Diesel Engines Modelling and Estimation from King’s College London, England, 2003. He is an Assistant Professor in the Department of Mechanical Engineering, Mu’tah University, Jordan, and is currently on leave from Mu’tah University. He has over 16 years research experience in the modelling, estimation, and control of mechanical systems, and has published over 40 refereed research papers in international journals and conference proceedings. His research interests include non-linear modelling, estimation, and control. Suksun Hutangkabodee obtained his BEng in Mechanical Engineering from Chulalongkorn University, Thailand in 1999. In 2002, he completed his MSc in Computer-Aided Mechanical Engineering from King’s College London, England (with a Distinction). In 2003, he then pursued his doctorate study in the same institution researching on interaction dynamics between vehicles and unstructured terrain. His PhD was sponsored by the Ministry of Defence and the Engineering and Physical Science Research Council. He was awarded his PhD degree in 2007. His research interests focus on parameter estimation, interaction dynamics modelling, and autonomous control. He is a member of the IEEE and IET.