PI Control of a Piezoelectric Bending Micro-actuator for Precision Positioning Applications

The primary focus of this thesis is to develop a control strategy for a piezoelectric bending actuator. This actuator exhibits hysteresis between the driving voltage and the displacement, characterized by high nonlinearity and a noticeable phase shift as the frequency increases. The aim is to design a controller that is easily implementable, incorporating some calculation simplifications. The chosen controller is a PI (Proportional-Integral) controller, widely recognized and utilized in industry. Two PI controller designs are developed, each considering different model identifications. One model is based on a port-Hamiltonian system identified for sinusoidal response, while the other is based on identification for step response. Several tests are presented for both PI controllers, involving both step and sinusoidal input signals at different amplitudes and frequencies. The testing of the PI controllers on real device was conducted at the Advanced Center of Electrical and Electronic Engineering (AC3E) of the Federico Santa María Technical University (UTFSM) in Valparaíso, Chile, where this thesis was developed. The hardware setup and testing enabled the concretization of the theoretical analysis. The piezoelectric actuator exhibits different behavior with the two PI controllers. There is no definitive superiority of one controller over the other, but each PI controller performs better when working with the type of response its model identification was based on. This implies that the PI controller designed for the port-Hamiltonian system performs better with sinusoidal input signals, while vice versa for the other PI controller, which works better with step input signals.