McKibben artificial muscle using shape-memory polymer

When McKibben artificial muscle actuators are used to drive robotic joints they are typically configured in pairs which act antagonistically to increase joint stiffness However this configuration cannot maintain a fixed position without continuous control The objective of this study is to develop a McKibben artificial muscle which can fix into a rigid shape without the need for continuous control This is achieved by exploiting the inherent properties of shape-memory polymers (SMPs) SMPs can be deformed above their glass transition temperature (T-g) upon the application of a small load They can maintain their shape in a rigid form after they have been cooled to below T-g When heated again above T-g they return to their predefined shape Exploiting these characteristics we impregnate the braided mesh shell of a commercial McKibben artificial muscle with SMP resin When this new actuator is warmed above T-g it can be used as a conventional McKibben muscle When the actuator attains its desirable length it can be cooled to below T-g and the SMP will fix the structure in a rigid actuated state This state is maintained without the need for any air supply or control system The enhanced versatility of this new actuator is shown through a series of experiments conducted on a prototype SMP McKibben actuator (c) 2010 Elsevier B V All rights reserved