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.