Sliding mode control based disturbance compensation and external force estimation for a piezoelectric actuator

In this paper a sliding mode algorithm for total disturbance estimation and control of piezoelectric stack actuator is proposed. The disturbance observer is based on the lumped parameters model of mechanical motion so it allows the summary action of nonlinear hysteresis disturbance, external forces acting on the system as well as parameters variation to be estimated. Furthermore, using a nonlinear differential equation the internal hysteresis disturbance is removed from the total disturbance in an attempt to estimate the external force acting on the actuator. It is then possible to use this external force estimate as a means of observer based force control of the actuator. Simulation and experiments are compared for validating the disturbance and external force estimation technique. Experiments that incorporate disturbance compensation in a closed-loop SMC control algorithm are also presented to prove the effectiveness of this method in producing high precision motion.