Y. Takeda, TAKE R&D, Fujieda-shi, Japan; T. Yamamoto, Y. Kudo, Oita University, Oita-shi, Japan; T. Sakuma, Oita University, Oita, Japan
The actuators using shape memory alloy (SMA) can work as an actuator to control or retain positioning without using sensor device, because SMA is such a superior element that the element itself has a sensing function in it. This type of sensor-less system brings about many merits like simplification of the system and easy and simple operability. SMA has a characteristic that electric resistance varies due to the phase transformation in the process of heating and cooling. The actuators, applying this characteristic to position control of SMA with resistance feedback, have been reported. Authors have proposed the new resistance feedback control system by using the method of setting OFF time and Blanking time and have showed that positioning can be set and retained at an arbitrary position. In this work, a position control system with three kinds of biasing mechanism, which is a constant mass, a bias spring and antagonistic wire, is produced and evaluated. The produced position control system is controlled by a resistance feedback method. The SMA element used for the actuator is Ti-Ni-Cu alloy, which has a relatively small transformation temperature hysteresis. The alloy wire, which is memory processed in a linear shape, has a length of 400mm and a diameter of 0.156mm. A constant mass is 40-130 gr. Investigation is made on such positioning characteristics as settling velocity at heating/cooling and position accuracy in relation to the applied load. Furthermore, the effect of biasing mechanism on positioning characteristics is discussed.
Summary: A position control system with three kinds of biasing mechanism, which is a constant mass, a bias spring and antagonistic wire, is produced and evaluated. The produced position control system is controlled by a resistance feedback method. The SMA element used for the actuator is Ti-Ni-Cu alloy, which has a relatively small transformation temperature hysteresis. Investigation is made on such positioning characteristics as settling velocity at heating/cooling and position accuracy in relation to the applied load. Furthermore, the effect of biasing mechanism on positioning characteristics is discussed.
