Study on observer based piezoelectric self-sensing actuator

Piezoelectric actuators often work in a close-loop feedback position control system due to hysteresis. Our objective is to make an actuator self-sense its output force and displacement without using extra sensors, which is termed self-sensing actuator/actuation (SSA). A compound circuit was proposed to voltage-drive the piezoelectric actuator and get the resulting charge concurrently. Based on the circuit, the unstressed actuator can self-sense its free strain. If the actuator is externally stressed, an observer was constructed to estimate the actuator's stress and strain state. The observer-based self-sensing approach is akin to state estimation techniques, depending on the fact that the electric field is controllable and the electric displacement is measurable. In order to compensate hysteresis, voltage versus charge relation was modeled using Generalized Maxwell Slip (GMS) model; and the observer was improved to a nonlinear one. The observer-based SSA approach successfully bypasses the impedance mismatching problem bothering the bridge-based SSA approach. Experiments validated the approach.