A Mechanical Amplifier for Haptic Feedback

Thesis (Master's)--University of Washington, 2013Vibrotactile devices suffer from poor energy efficiency, arising from a mismatch between the device and the impedance of the human skin. This results in over-sized motors and excessive power consumption, and prevents development of more sophisticated, miniaturized and low-power mobile tactile devices. Herein, I investigate the feasibility of improving the energy transfer by placing a passive amplifier between the skin and the motor, dubbed an impedance adapter. I simulate the effects of this impedance adapter using a mathematical model, and evaluate its effect on skin displacement and a parameter I call skin stimulus. Skin stimulus is introduced as a measure of the perceptive effects of a haptic system, and is used to compare results between systems with an impedance adapter and those without. Functional prototypes are constructioned, and the design is experimentally verified. This system is able to quadruple the motion of the skin without increasing power consumption, and produce sensations equivalent to a standard system while consuming 1/2 of the power. By greatly reducing the size and power constraints of vibration motors, this technology offers a means to realize more sophisticated, smaller haptic devices