Abstract— A high-power flexible actuator with a built-in displacement sensor that can support bathing is attractive as a wearable actuator. In the previous study, a rubber artificial muscle with the inner diameter sensor was proposed and tested. The sensor could measure the axial length of the rubber artificial muscle based on the geometric model of the muscle, indirectly. The position control of the muscle using the tested sensor based on the model and the identified parameter was successfully carried out. However, a measuring error caused by a setting error of the sensor was also observed. In this paper, to decrease the measuring error based on the sensor’s setting position error in the muscle, an improved inner diameter sensor with radially arranged three photo reflectors was proposed and tested. To get larger generated force, the muscle with larger diameter compared with the previous one was also used. In addition, to realize the wearable actuator that can be easily operated, an intelligent rubber article muscle with an integrated pneumatic driving system and the built-in inner diameter sensor was proposed and tested. The position control of the tested muscle was also carried out. As a result, it could be confirmed that the tested muscle controlled by giving reference electric signal was be realized.