Design and Control of a Parallel Robot for Ankle Rehabiltation

The use of robots in rehabilitation, particularly for physical therapy has the potential to bring about various benefits including reduction of physical workload of physiotherapists and improved repeatability. A three degree of freedom parallel robot is proposed in this paper to accommodate range of motion and muscle strengthening exercises for ankle rehabilitation. Singularity analysis of the design revealed that a redundantly actuated robot is required to avoid singularity in the workspace. Kinematic parameters of the robot were selected so that the available workspace could closely match the available ankle range of motion. An impedance control scheme has been utilized to allow control of both force and motion to ensure safety of the patient. The redundant actuation degree of freedom is exploited to regulate the vertical reaction force at the ankle.