Smart materials for microrobotics motion control and power harvesting

Abstract

[eng] This thesis focuses on the use of smart materials in microrobotic applications. The development of materials with the capabilities to mechanically respond to electrical stimuli or, at the same time, to electrically respond to mechanical stimuli, has entailed the microrobotics rapid evolution. Along this thesis the use of three smart materials families in the filed of microrobotics is studied. The materials used are the piezoelectric ceramics, the piezoelectric polymers and the ionic polymers metal composites IPMC. The similitude in the way they respond to external stimuli has motivated this study. The three materials respond with an induced mechanical strain under the application of an electric field and respond with an induced electrical charge variation when a mechanical pressure is applied. Although these materials respond similarly, their application in microrobotic systems entails different problems. In this thesis their use in different applications is studied and the problems enclosed with their use are treated. First of all in this thesis the use of piezoelectric polymers and ionic polymers as materials for motion control of microrobots is studied. Their flexibility opens the door to new applications for microrobot systems as is the case of biomimetics. The first application regards the use of piezoelectric polymers in insect-like mm3 microrobot. The microrobot is composed with three legs and one antenna or tool for object collision based on piezoelectric polymers. The object collision tool is used as a sensor for motion control to avoid collisions with other objects. The work presented consists on the development of theoretical models to predict the motion of he leg and the tool of the microrobot. The second application regards the development of a control system for controlling the motion of an ionic polymer IPMC underwater. It is difficult to obtain physical models that describe the motion of these materials, thus it is important to design control strategy to work with IPMCs. Furthermore in this thesis, the problem of manufacturing electrodes for IPMC is also treated. In the second part of the thesis the use of piezoelectric ceramics to harvest power from mechanical vibrations is studied. Piezoelectric ceramics have higher energy densities compared with other methods for power harvesting from vibrations. In comparison with the piezoelectric polymers, the piezoelectric ceramics produce voltages and current levels more acceptable. From the study performed in this thesis the conditions for a maximum power generation are obtained and an optimum electronic circuit for energy storage and management is designed. At the end of the thesis the capabilities to harvest power using ionic polymers are studied. KEY WORDS: Smart Materials, Microrobotic, Harvesting, Motion Control, Fonic Polimer, FPMC Piezoelectric, Modelling

[cat] Aquesta tesis es centra en l'ús de materials "smart" o intel·ligents en aplicacions de microrobòtica. Al llarg de la tesi treballem amb tres famílies de materials "smart" diferents: les ceràmiques piezoelèctriques, els polímers piezoelèctrics i els polímers iònics coneguts com Ionic Polymer Metal Composites (IPMC). Aquests materials tenen en comú que al aplica'ls-hi un camp elèctric pateixen una deformació mecànica mentre que si els sotmetem a una deformació mecànica, aquests materials pateixen una variació en la seva càrrega elèctrica interna. Degut a aquestes propietats aquests materials poden ser utilitzats com a sensors o com a actuadors. A la primera part de la tesi estudiem l'ús dels polímers piezoelèctrics i dels polímers iònics per al control del moviment dels microrobots. La primera aplicació que es presenta tracta d'un microrobot de dimensions mm3 que utilitza els polímers piezoelèctrics com a potes i com a sensors de col·lisió. Tot seguit presentem una aplicació a on els IPMCs són utilitzats com a microposicionadors treballant sota de l'aigua. A la segona part de la tesis estudiem la viabilitat d'utilitzar les ceràmiques piezoelèctriques i els polímers iònics per a generar energia a partir de vibracions mecàniques residuals ambientals. L'estudi presentat determina els nivells de potència generats i les condicions òptimes per a la generació de la màxima potencia.