Multi-Freedom Tube Type Manipulator with SMA Plate

Abstract

The tube type multiple link micromanipulator using SMA (Shape Memory Alloy) has been conducted. The conceptual model of this manipulator has five linked pipes with 1 mm in diameter. On each link, a temperature/strain sensor and a control IC chip are equipped for position and/or force feedback control. We have successfully fabricated a prototype. This tube type manipulator, which is 2 mm in diameter, has two links. This prototype manipulator has two flexible SMA plate links which are given all direction shape memory effect over 60 degrees in vending angle. These links mutually bend at a right-angle. These SMA plates are fixed SUS pipes through which a silicon rubber tube is arranged. By using the technology of semiconductor manufacturing, the MIF (Multifunction Integrated Film) has been developed for integration of electrical elements for the manipulator. The MIF has several functions; strain sensor, temperature sensor, heater, and wires to interconnect links. In this manipulator, the MIF with 7 itm in thickness is attached to each SMA plate. As a flip-flop circuit chip is mounted on each MIF in a state of bare chip, many heaters and sensors are controlled serially by shift-resisters. Therefore, this manipulator is controlled by eleven common wires even if the number of links increases. The heater is constructed with Ti film. The sensors are constructed with Ti film and Pt film. As these two materials have different gage factors and temperature coefficients, the value of temperature and strain can be calculated from the change of the resistivity. By PID feedback control with strain and temperature, the positioning error at the end of the link is less than 0.2 mm.