Improving the global performance of a fuzzy gain-scheduler by supervision

• The fundamental issue in gain scheduling along a desired reference trajectory is the question of guaranteed stability of the overall gain-scheduled closed-loop system. Since the gain-scheduled design is based on linear-time-invariant approximation of the open-loop system, and since this system is actually nonlinear, the design guarantees only local stability. This requires a further restriction, namely that the desired reference trajectory should vary slowly. The design of a fuzzy gain scheduler requires a conventional model of the nonlinear system under control and a partition of the state space into a ®nite number of fuzzy regions. The nonlinear system is Lyapunov-linearized at the center of each fuzzy region. Then linear controllers intended to locally stabilize the linearized system, and consequently the original nonlinear system, at the center of a fuzzy region are designed. In that way, gain-scheduling control of the original nonlinear system can be designed to cope with any (unknown in advance) slowly time-varying desired trajectory. This paper shows how the stability and robustness analysis of the gainscheduled closed-loop sysem in terms of sliding-mode control techniques can be used for the design of a supervisory system which avoids unstable behavior outside the region in which local stability is guaranteed.

Nyckelord

gain scheduling

fuzzy gain schedulers

Sliding-mode control

Supervision

Datateknik

Computer Engineering

Reglerteknik

Automatic Control

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)