The Development of Shape Memory Actuators for Anthropomorphic Upper Limb Prostheses

The single crystal Cu-Al-Ni alloys became generally commercialized. It can be observed that response time of any single crystal Cu-Al-Ni-based shape memory alloy (SMA) actuator is greater than the necessary when it is used for human prosthesis. Moreover, the electrical SMA actuator type with better performance than the thermal one is very problematic for this type of crystal due to its low electrical resistance. However, the construction of thermal single crystal Cu-Al-Ni-based SMA actuator can be improved to reduce this disadvantage when compared to the famous Ni-Ti SMA alloy. As option to reduce the time of response of single crystal Cu-Al-Ni-based SMA the heating procedure was developed and tested. To elaborate the heating conditions, the chemical composition of martensitic and austenitic single crystals, Cu-Al-Ni alloy samples were examined. The executed experiments clearly demonstrated the advantage of the preheating phase. The response time of the SMA prototype actuator was reduced to considerably adequate values when compared to those usually used as actuators in human prosthesis .