Design of a partially compliant crank rocker mechanism using Ionic Polymer Metal Composite for path generation

Four-bar mechanisms traditionally are made of rigid links and they are used for path, motion or function generation. Actively changing the length of the rocker in a crank rocker four-bar mechanism results in the tip of the rocker following a closed path. In this paper a crank rocker mechanism has been designed with a variable length rocker using an Ionic Polymer Metal Composite (IPMC). A pseudo rigid body model is used to represent the IPMC bending during path generation and a dynamic model is developed to relate the position of the rocker tip and the input voltage required to bend the IPMC. A simple control system has been designed that can apply a desired voltage to the IPMC using pulse width modulation, for obtaining a particular deformation. Experimental results of a path generated using the proposed mechanism is presented. This mechanism has wide application in micro robots for pick and place applications, actively controllable partially complaint mechanisms, adaptive structures, etc. (C) 2009 Elsevier Ltd. All rights reserved.