Influence of Initial State on Position Regulation of Hysteretic Actuators

ABSTRACT: Actuators made from so-called smart materials have been proposed in the literature, for use in shape control of various surfaces. At the lowest level, this shape control problem can be thought of as a distributed regulation problem. Because of the hysteresis nonlinearity present in these actuators, there are an infinite number of input values corresponding to a particular output regulation setpoint. One might then ask the question, not relevant to memory-less systems, whether there is some advantage to regulating about one of these states in particular. This work proposes, based on observations from the Preisach model, that for any desired output there is one state in particular at which the system has a better natural (open-loop) rejection of uniformly-distributed noise at its input. This proposition is tested in both simulation and experiment. The reachability of this so-called ‘neutral state ’ is discussed, as is the generation of an input to drive the system to the appropriate neutral state. It is demonstrated that closed-loop regulation schemes will also benefit from starting in the appropriate neutral state, requiring less control effort for regulation. Key Words: hysteresis, shape control, regulation, intelligent materials