Abstract—Today, the care and welfare pneumatic equipment to support a nursing care and a self-reliance of the elderly and the disabled are actively researched and developed by many researchers. These wearable devices require many servo valves for multi degrees of freedom and precise control performance of the wearable actuator. The total weight of the wearable devices increases according to the degree of freedom. In the previous study, a small-sized and light-weight pressure control type quasi-servo valve and rubber artificial muscle using built-in displacement sensor were developed. The quasi-servo valve consists of two on/off control valves and an embedded controller. In this study, an ultrasonic sensor is installed in the rubber artificial muscle as a displacement sensor. Then, the position control of the artificial muscle using the built-in displacement sensor is proposed and tested. As a result, it is confirmed that the position control of the muscle can be realized using the tested sensor.