Design of an Arm with Double Actuators for High Speed and High Accuracy Manipulation

The design and implementation of a one degree of freedom robot arm with a direct-drive motor and a pair of piezoelectric actuators embedded in the arm link is described. The piezo actuators create a moment to make the arm link bend and thereby move the endpoint slightly. This allows for fine positioning of the arm´s endpoint as well as for improved damping by actively controlling the arm link vibration. First, the architecture of the double actuation mechanism is discussed with regard to dynamics and control performance. A prototype arm is designed and built, and an analytic model of the arm dynamics is obtained. A simple controller using endpoint and strain feedbacks is designed. It is shown that fine positioning and fast, stable control are accomplished with the arm having a double actuation mechanism.