Experiments on the Performance of a 2-DOF Pantograph Robot Actuated by Shape Memory Alloy Wires

This paper describes a study of tracking speed and accuracy for a 2-DOF pantograph robotic device actuated by two antagonistic pairs of electrically-heated SMA wires. The objective is to investigate the coupling effect due to the actuation of the two SMA pairs and the dynamics of the pantograph device on the performance of the motion control system. Two different controllers, a two-stage relay controller and a modified proportional controller, have been tested and compared, and experimental results are presented in this paper. The relay controller performs satisfactorily in terms of speed of response, but the large limit cycle phenomenon degrades its accuracy. The modified proportional controller manages to reduce the limit cycle problem and its tracking speed is comparable with the relay controller. Experimental results will also show that the modified proportional controller may not be the best controller for this SMA-actuated pantograph device.