Static display of shape

Abstract
Among the mechanical parameters that are important for dexterous manipulation, shape is useful for both object recognition and control purposes. To investigate the role of shape information in telemanipulation we have created a tactile shape display. This prototype consists of a regular 6 X 4 array of pin elements or `tactors' which rest against the operator's finger tip. Shape memory alloy wires raise individual tactors to approximate the desired surface shape on the skin. We have implemented a feedforward control law and air- cooling that improves the bandwidth of the otherwise slow SMA wires. The hysteretic and nonlinear nature of the SMA actuators has also led us to implement a closed loop controller with position feedback using an optical emitter-receiver pair. The resulting performance of the SMA actuators has a -3 dB bandwidth point between 6 and 7 Hz. We have interfaced the display with a capacitive tactile array sensor and we are able to convey simple shapes from a remote environment through the display. The results of simple tactile feature localization experiments show the ability of the shape relay system to convey shape information.