A Novel SMA Driven Compliant Rotary Actuator Based on Double Helical Structure

This paper proposed the new SMA driven compliant rotary actuator, which is able to perform both passive and self-actuated motions. This kind of actuator can be used as redundant actuation part in parallel robot's joint to help for the singularity postures that the robot might lose the ability to maintain the position and orientation of the end effector. So this kind of redundant actuation can compensate the error due to some external disturbances. It requires rotating both forward and backward sides as passive revolute joint to achieve 1DOF motion and energizing itself to generate compensating motion. The Double Helical Compliant Joint, DHCJ was chosen as a candidate mechanism, which can act as a soft compliance with linear characteristics and wide range of motion. The SMA leaves were used for actuation parts. The prototype was fabricated and tested to determine the necessary parameters of model. This actuator achieved 40 degrees range of motion for both sides by using feed forward controller.