2013 Academic Year Seminars
The purpose of this presentation is to study the dynamic stability of the accelerating bicycle. It is shown that time-scale separation can be used to study the oscillatory characteristics of the accelerating machine using time-invariant models. These models are used to explain practically observed wobble-mode bursting oscillations which are associated most frequently with down-hill riding. If the vehicle is cornering under constant acceleration at a fixed roll angle, it is shown that for low values of acceleration (and braking), it follows closely a logarithmic spiral shaped trajectory. The study to be presented is facilitated by a novel adaptive control scheme that centres the machine’s trajectory on any arbitrary point in the ground plane. The influences of longitudinally inclined and cambered road surfaces are also investigated. The bicycle model employed is based on that originally developed by Whipple, and comprises two road wheels and two laterally-symmetric frame assemblies that are free to rotate relative to each other along an inclined steering axis. For the most part the front frame is treated as being flexible and the bicycle is fitted with force generating road tyres, rather than classical nonholonomic rolling constraints. While the dynamics of the bicycle is of interest in its own right, this research provides the theoretical ground work required for generating more complex dynamic models for high-performance motorcycle studies.
David J. N. Limebeer was born in Johannesburg South Africa. He received a B.Sc. (Eng) degree in Electrical Engineering from the University of the Witwatersrand in 1974, and the M.Sc. (Eng) and Ph.D. degrees in 1977 and 1980,respectively, from the University of Natal in South Africa. He then received the D.Sc. (Eng) degree from the University of London in 1992. From 1974 to 1976 he was an assistant engineer at the Johannesburg City Council. In 1980 he moved to England and took up a Research Assistantship at the University of Cambridge England between 1980 and 1983. In 1984 he moved to the Department of Electrical Engineering, Imperial College, London as a lecturer. In 1989 he was promoted to Reader in Control Engineering and to Professor of Control Engineering in 1993. He was head of the Control Group in the Department of Electrical and Electronic Engineering between 1995 and 1999. He is now the Head of the Department of Electrical and Electronic Engineering at Imperial College. He has held several visiting positions at the University of Southern California, the Australian National University and Stanford University. He is a past editor of Automatica and a past associate editor of Systems and Control Letters and the International Journal of Robust and Nonlinear Control. He has served on the Science and Engineering Research Council's control and instrumentation sub-committee and is a current member of the Engineering and Physical Science Research Council’s control and instrumentation college. He was joint recipient of the AACC O. Hugo Schuck award for the best paper presented at the 1983 American Control Conference. He was elected Fellow of the American IEEE in 1992 and Fellow of the British IEE in 1994. He was also elected Fellow of the Royal Academy of Engineering in 1997, and Fellow of the City and Guilds Institute in 2002. His research interests include multivariable system theory, the theory and application of robust control, dynamic system modelling and identification, computer aided control system design, power system stability, the control of tokomaks and the stability of two-wheeled road vehicles.