The design and control of a tactile display based on shape memory alloys

A 64 element tactile array has been produced, based on shape memory alloy technology, with a modular construction which allows easy expansion and repair. Resistive feedback is used to give closed loop PI control of the height of each tactel, within a PWM and tactel scanning technique, the closed loop feedback providing insensitivity of all elements to disturbances and changes in ambient conditions. The electronic circuitry is compact with a single microcontroller used to provide all the control. This, allied with the modular construction, gives a design which is readily expandable from its current size. The dynamic performance of the device is described via step responses and some elementary psychophysical experimental results are presented to demonstrate its ability to create identifiable shapes.