2022 年 88 巻 911 号 p. 22-00040
In recent years, many types of inchworm mechanisms have been developed as miniature linear actuators for high-resolution positioning. The mechanism can usually move over a long distance regardless of the positioning actuator stroke because it moves like an inchworm by sequentially driving two clamping elements and one positioning actuator. However, most mechanisms equipped with a multi-layered piezoelectric actuator for positioning have difficulty to improve their feed rate because of a small stroke of the actuator, despite their excellent positioning resolution. An inchworm mechanism in this study employs one electromagnet for longitudinally driving a moving bar and two electromagnets for clamping the bar. Use of the electromagnet with a larger stroke enables a high-speed feed rate and allows for the use of inexpensive low-voltage amplifiers. Furthermore, a displacement reducer based on the toggle linkage reduces the actuator displacement and enlarges the thrust force. Since the output displacement of the reducer exponentially increases with an increase in the input displacement, this mechanism achieves not only high-speed positioning but also high-resolution positioning as necessary. This paper describes the principle of proposed mechanism and the design of the electromagnet actuator and clamps. Experiments of a prototype mechanism showed that low reduction ratio of the reducer achieved maximum feed rate of 25 mm/s at a driving frequency of 110 Hz. In addition, high reduction ratio kept the positioning resolution less than 50 nm.
