Shape memory alloy actuator controller design for tactile displays

This paper describes the design of a controller for a tactile shape display for dexterous telemanipulation applications. This device consists of an array of pin elements which rest against the human finger tip. Shape memory alloy (SMA) wire actuators raise individual pins to approximate the desired surface shape on the skin. To overcome the slow response times of SMA actuators we have implemented a feedforward derivative compensator and pneumatic cooling. The hysteretic and nonlinear response of the SMA actuators required the use of a closed loop controller with position feedback using an optical emitter-receiver pair. This also improves robustness to the load variations which result from human interaction