Propulsion by traction raises several issues, including modeling of the friction force that produces traction and the design of appropriate control laws. The traditional adhesion model and several other static and dynamic friction models are described: Coulomb stiction model, friction models with hysteresis and state-variable friction models. Control laws that account in some manner for the severe nonlinearity of traction are investigated by simulation. A full state feedback control law and an observer were designed. It is shown that ignoring the nonlinear effects can result in an unstable system, but that the instability can be avoided by an appropriate control law design including an observer that accounts for the nonlinear friction model. The investigation suggests that the following considerations are important (1) Slip velocity must be considered when commands can require friction forces near the maximum that the source can produce. (2) If slip velocity cannot be measured, it may be possible to estimate it by means of an observer that incorporates the nonlinearity of friction into its dynamics. (3) If the maximum level of friction is not known, the observer should be based on an under-estimate of this level. (4) The model of friction used in the observer need not be accurately matched to the true friction in the system.
Aspects of traction control
Fahrzeugantriebsregelung mit Reibungskompensation
1999
11 Seiten, 9 Bilder, 4 Quellen
Conference paper
English