Abstract: Piezoeleclric actuators often work in a close-loop feedback position control system due to hysteresis. The objec-tive is to make an actuator self-sense its output force and dis-placement \vithout using extra sensors. The technique is termed self-sensing actuator/actuation (SSA). A compound circuit is proposed to voltage-drive the piezoelectric actuator and get the resuiting charge concurrently. Based on the circuit, the un-stressed actuator can self-sense its free strain. If the actuator is externally stressed, an Observer is construcied to estitnate the actuator's stress and strain state. The observer-based self-sensing approach depends on tlie fact that the electric field is controllable and the electric displacement is measurable. In order to cornpensate hysteresis, voltage versus charge relation is modeled using generalized Maxwell slip (QMS) model, and the observer is improved to a nonlinear one. The observer-based SSA approach successfiilly bypasses the impedance mismatch-ing problem bothering the bridge-based SSA approach. The self-sensed average strain of piezoelectric bimorph is coincident with the tip displacement measured by proximitor.

Key words: Piezoceramics Actuator State observer/Self-sensing actuator