Robust Control of Magnetostrictive Actuators With Uncertain System

In this paper, the problem of designing a state feedback controller over a wide frequency range (0 – 1kHz) for a magnetostrictive actuator connected to a mechanical system is discussed. Our model for the magnetostrictive actuator includes hysteresis, classical and excess eddy current losses. The hysteresis nonlinearity is modeled using a classical Preisach operator, and it is assumed that the density function is approximately known. The feedback controller achieves uniform ultimate boundedness — a property weaker than global asymptotic stability when the trajectory to be tracked is zero — in the presence of exogenous disturbances and uncertainty in the model. The main objective of the paper is to demonstrate that knowledge of the induced emf can be used to eliminate the need for hysteresis compensation in the control scheme. The novelty of this work is that we utilize the induced emf in the actuator coil as an observed variable, and also demonstrate how this quantity can be measured in real-time. Most controllers use inverse compensators to cancel out actuator hysteresis nonlinearity. We show that we can achieve uniform ultimate bounded control without an explicit inverse computation (using least squares minimization or otherwise).