Design aspects of shape memory actuators

The need for high performance and at the same time compact actuators has existed for a long time, especially for multi-degree-of-freedom devices like robot hands and walking robots. These devices mostly use electrical actuators. Also for the presented research, the interest in designing actuators based on shape Memory Alloys emerged from a study in the field of multifingered robot hands. Shape Memory Alloy actuation is very attractive because of the very high power density that can be obtained using these materials. When calculating the ratio of actuator output to actuator volume, also called power density, SMA actuators offer even higher values than hydraulic actuation. Nevertheless, controlling these actuators and implementing them in robotic systems is not so straightforward. This paper defines a number of design rules for shape memory alloy based robotic actuators. II is demonstrated that SMA actuation offers very attractive properties for example in space applications and especially in a zero-gravity environment. This paper also shows that, when using an appropriate cooling method, accurate position control for Shape Memory Alloy actuators can be obtained. (C) 1998 Elsevier Science Ltd. All rights reserved.