OFF-EQUILIBRIUM LINEARIZATION AND DESIGN OF GAIN-SCHEDULED CONTROL WITH APPLICATION TO VEHICLE SPEED CONTROL

In conventional gain-scheduled control design, linearisation of a time -invariant nonlinear system and local control design for the resulting set of linear time-invariant systems is performed at a set of equilib rium points. Due to its validity only near equilibrium, such a design may result in poor transient performance. To resolve this problem, one can base the control design on a dynamic linearisation about some nom inal trajectory. However, a drawback with this approach is that contro l design for the resulting linear time-varying system is in general a difficult problem. In this paper it is suggested that linearisation an d local controller design should be carried out not only at equilibriu m states, but also in transient operating regimes. It is shown that th is results in a set of time-invariant linearisations which, when they are interpolated, form a close approximation to the time-varying syste m resulting from dynamic linearisation. Consequently, the transient pe rformance can be improved by increasing the number of linear time-inva riant controllers. The feasibility of this approach, and possible impr ovements in transient performance, are illustrated with results from a n experimental vehicle speed-control application. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.