This paper proposes two position control methods for a double air chambers pneumatic artificial muscle (W-PAM) developed to improve the hysteresis characteristics of the rubber-less artificial muscle and confirms their characteristics and usefulness. The proposed control methods are the external pressure-regulated position feedback control and the internal pressure-regulated position feedback control. Of the two air chambers in the W-PAM, the air chamber regulated by the feedback control is different. The steady-state characteristic and frequency characteristics of these controls were compared, and it was experimentally confirmed that the adjusted position feedback control is superior in terms of position control performance. On the other hand, we confirmed that external pressure-regulated position feedback control can express passive stiffness, which is an important characteristic of pneumatic artificial muscles. These results indicate that the W-PAM is a useful actuator for human coexistence systems, because it can express both positional control performance and softness by using different control methods depending on the application.

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