Independent Control of Force & Displacement Using Shape Memory Alloy Tactile Display

Abstract

This paper proposes one of the possible techniques for interacting for shape memory alloy (SMA) actuator based tactile display, which can act as demonstrator devices. This work is focused on developing a model of a pair of antagonistic high strain SMA tension actuators with independent control of force and displacement. The technology employed utilizes two Flexinol 100 micron heat actuated wires of Titanium-Nickel (NiTi) shape-memory alloy which contract when heated under pre-stress and produces up to 5% strain recovery. This phenomenon, which provides a unique mechanism for actuation, is associated with the unique interaction between the martensite and austenite crystal structures of the SMA. Physical measurements of the behaviour of the actuator elements were performed using a laser displacement sensor to verify the fidelity of response to software commands, and to measure step response to pulse-width modulated (PWM) current control at different frequencies and duty cycles. Results yielded high accuracy across a wide range of frequencies and duty cycles, proving the SMA actuation technique has potential to present and convey useful tactile information of surface deformation for virtual environment applications.