Combination Process of a Pneumatic Artificial Muscle and a Fiber Optical Sensor System †

A McKibben artificial muscle is a typical soft actuator, and it features flexibility, lightweight, and low cost. It consists of a rubber tube and a sleeve which is woven with spiral fibers, and contracts axially by applying pneumatic pressure to the rubber tube. We have developed the combination structure of the McKibben artificial muscle and the optical fiber which works as a contractile displacement sensor. The optical fiber can be braided into the sleeve which is the necessary component of the artificial muscle, which means that the optical fiber works as not only the sensor element but also the actuator element. In the previous sensor system, the light-receiving part (photo IC diode) and the light-emitting part (LED) were located at the base and tip sides of the artificial muscle, respectively. This configuration has a limitation in applications and the possibility of electrical line troubles. In this report, the LED and the photo IC diode are arranged at the base end of the artificial muscle by improving the fabrication process. Through the process, the optical fiber from the base can be returned to the base again via the tip, and the LED and photo IC diode can be located at the base side of the artificial muscle. Experimentally, the relation between the sensor output and contractile displacement of the artificial muscle was confirmed.