Control Approach for a Novel High Power-To-Weight Ratio Actuator Scalable in Force and Length for Robots

One of the research goals in robotics is the development of home-help robots. The development of a control approach for a novel lightweight and multifunctional shape memory alloy (SMA) actuator scalable in force and length for robots is presented in this paper. The SMA actuator is based on lightweight bundles of thin wires of prestrainend shape memory alloy that change their length when heated above their transformation temperature. The design approach of the actuator allows arranging the point of actuation in any direction and ensures a short cool down time to guarantee a frequency of contraction/stress cycles that is high enough to allow fast joint motions. This is needed for the generation of fast joint motions. For the use of the actuator the novel control approach has been experimentally validated. The approach uses the resistance of the actuator as a linear position encoder and there are no additional external sensors needed. The application of the new actuator to a novel lightweight humanoid robot is outlined. One advantage of the actuator over electric motors lies in the large variety of user-defined points of actuation of the in pull-force and length free scalable actuators and the high power-to-weight ratio. The result show that it is possible to build a large humanoid robot actuated with SMA actuator in a new way. Index Terms – sensor systems, smart sensors, artificial muscles