A HIGH-PRECISION MICROPOSITIONER BASED ON MAGNETOSTRICTION PRINCIPLE

A novel two degree-of-freedom precision micro-positioner has been designed and built using Terfenol-D magnetostrictive material. The device consists of a group of Terfenol-D rods which have been linked together to form a rigid, prism-shaped body. When the coils wrapped around the Terfenol-D rods are supplied with electrical current, the magnetic fields produced will cause the rods to strain, inducing a displacement at the end point. Controlling the electrical currents supplied to the coils allows very precise movements to be obtained. Another degree of freedom can easily be added to make the device capable of precise motions anywhere within a volume. The device discussed here fits into a 3 in. by 3 in. by 1.5 in. space, and is capable of addressing a 100-mu-m by 100-mu-m workspace with a maximum current of 1.5 A applied. The open-loop repeatability of the device is 50 nm over the workspace. With the implementation of a simple closed-loop controller, the accuracy of the device is limited by that of the sensing system, and the resolutions of the 12 bit A/D and D/A boards used. Much higher resolution can be expected if 14 bits or 16 bits A/D and D/A boards are used. Potentially the device can be used for high precision microprobing, cellular biology, microsurgery, and industrial work in the micromechanical area.