Experimental performance and feasibility of a miniature single-degree-of-freedom rotary joint with integrated IPMC actuator

Ionic Polymer Metal Composite (IPMC) materials are bending actuators that can achieve large tip displacements at voltages less than 10V, but with low force output. Their advantages over traditional actuators include very low mass and size; flexibility; direct conversion of electricity to mechanical energy; biocompatibility; and the potential to build integrated sensing/actuation devices, using their inherent sensing properties. It therefore makes sense to pursue them as a replacement to traditional actuators where the lack of force is less significant, such as micro-robotics; bio-mimetics; medical robotics; and non-contact applications such as positioning of sensors. However, little research has been carried out on using them to drive mechanisms such as the rotary joints. This research explores the potential for applying IPMC to driving a single degree-of-freedom rotary mechanism, for a small-force robotic manipulator or positioning system. Practical issues such as adequate force output and friction are identified and tackled in the development of the mechanical apparatus, to study the feasibility of the actuator once attached to the mechanism. Rigid extensions are then applied to the tip of the IPMC, as well as doubling- and tripling the actuators in a stack to increase force output. Finally, feasibility of the entire concept is considered by comparing the maximum achievable forces and combining the actuator with the mechanism. It is concluded that while the actuator is capable of moving the mechanism, it is non-repeatable and does not achieve a level that allows feedback control to be applied.