Optimal observability-based modelling, design and characterization of piezoelectric microactuators

Abstract

This paper deals with the optimal design of monolithic piezoelectric microactuators with integrated proprioceptive sensors. Dedicated to the microrobotic and micromechatronic fields, this work details the modelling and the characterization of compliant structures with integrated actuating and sensing elements. The proposed optimal design procedure addresses not only static criteria but also dynamic ones. This leads to microdevices which are better performing with regards to mechanical (displacement, force, etc) and control (dynamics, stability, precision) characteristics. The efficient design of such devices is achieved using a flexible building block method. A topological optimization method combined with an evolutionary algorithm is used to optimize the design of a truss-like planar structure. This method chooses the best location among the different piezoelectric elements. Different mechanical, actuation or sensing elements are accordingly chosen from a data bank. From the control point of view, optimization criteria are considered, to enforce the observability of the vibrational dominant modes of the structure. Therefore, control and observation Gramians are exploited in the optimal design to shape the open-loop frequency response of both actuation and sensing functions of the integrated device. In the last part of the paper, based on these results, the optimal design and manufacture of an innovative piezoelectric flexible microgripper is proposed. The prototype is manufactured from a monolithic piezoelectric material (PIC 151). Its reduced size (15 mm × 18 mm) fits the requirements of both microrobotic and micromechatronic applications, and it is suitable for micromanipulation tasks. Closing the paper, the characterization and the performance of this integrated microactuator and the efficiency of the optimal design procedure for micromechatronic applications are shown.