In this research, we developed a position control system for a hybrid actuator using position, velocity and pressure feedback loops as well as a force-blending algorithm. The actuator uses combination of a spherical MR-brake and three air muscles to create motion in two degrees-of-freedom (DOF). The spherical MR-brake is capable of rotating along three axes and restricts all motion when engaged. The control system helps prevent overshoot and instability in the air muscles by engaging the MR-brake when necessary. It also provides significant improvement in response time by making high-gain PID control of air muscles possible. Such an actuation scheme can be used in a wide-variety of advanced robotics applications such as walking robots, bio-robotics and exoskeletons, where high power, multi-DOF actuation is required in a compact volume.

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