Effect of Pulse Width Modulation Current Control on Shape Memory Alloy Actuators
Keywords:
Shape Memory Alloy SMA, Pulse Width Modulation PWM, Displacement, Force, Tactile DisplayAbstract
This paper proposes the design, construction and performance of a single element based tactile display. The technology employed utilizes a 100?m diameter heat actuated wire of Nickel-Titanium (NiTi) shape-memory alloy (SMA) which contracts when pulsed with an electrical current (in effect heating the metal) under pre-stress. The display can produce a maximum pin deflection of 5mm which can be raised and lowered to approximate the desired output signal. In other words, SMA materials can directly convert thermal energy to mechanical work. 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 material. The paper discusses the design and evaluation leading to the dynamic performance of the system via step responses as well as the control of tactile sensor length and displacement using pulse width modulated current control technique.
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