Ultra Precision Control of Piezo-electric Actuators

Piezoelectric actuators are finding increasing application in areas demanding high precision and fast response. Properties of the actuators that make them desirable for such demanding applications are their low mass, low heat generation, non-magnetic nature. The low mass implies that the response of the actuators to a given control input is very quick. The low heat generation enables the actuators to achieve high positioning accuracy over extended periods of operation. The non-magnetic nature makes such actuators immune to any electromagnetic disturbance that might affect the positioning accuracy. Moreover, the physical nature of the drive being linear implies that the errors like play and backlash that are unavoidable in conventional geared drives can be eliminated. Such errors are a major consideration particularly when large capacity drives are being used for motion control.

Some applications of piezoelectric devices and actuators are in disk drive head positioning and disk drive testing, micro-stabbers and micro-pipettes in cellular biology, optical lens and mirror positioning, micromanipulation in fabrication in semiconductor industries (one unconventional use of piezoelectric crystals is in cigarette lighters!).

To study fundamental problems associated with the control of piezoelectric actuator, a nanopositioner stage driven by a piezo-electric actuator shown in Fig.5 has been set-up. The stage has a built-in integrated capacitive sensor with a resolution less than 1 nanometer. The piezoelectric actuator is powered by a high accuracy voltage amplifer and will be controlled through a fast dSPACE system.

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Fig.5 Nanometer Positioning Stage