On variable structure actuator saturation compensators

Abstract

Most existing actuator saturation compensators are fixed structure with constant parameters. As the linear system now becomes nonlinear when the actuator saturates, using only one linear compensator may not be adequate to produce acceptable response. To overcome this problem, a class of variable structure compensators that switches between several linear compensators is proposed in this paper. The choice of the timing and the method to switch compensators is discussed. The stability of the compensated system using a variable structure compensator is derived. It is shown here that existing variable structure schemes such as the limiting integrators, and the P-band method are included as special cases. Hence the stability of systems using these schemes can be analyzed using the stability results derived here. The performance of the proposed compensators is illustrated by an example.