| Tremor is clinically described as a rhythmical, involuntary oscillatory movement of a body part produced by reciprocally innervated antagonist muscles. The current clinical treatments include a collection of prescription drugs and, in especially debilitating or non-responsive cases, neurosurgery. The adverse side effects of both methods have inspired research into a less invasive alternative, the attenuation of tremor on the musculo-skeletal level. In the field of human-machine interaction, particularly that of wearable robotics, high strength-to-weight ratio actuators are required to maximize assistive and rehabilitative potential. Magnetorheological-based actuators can potentially achieve these high ratios and have the additional advantages of rapid response time, high fidelity control, and low power requirements. Previous applications of magnetorheological dampers (MRDs) have been chiefly limited to vehicle shock absorbers and seismic vibration attenuators. The topic at hand is the feasibility of developing and controlling MRDs that would be functionally and cosmetically adequate for actuation of an upper limb tremor suppression orthosis.;A prototype damper is presented for this purpose with experimental and FEA results to assess it's bandwidth and performance potential. An invertible lumped parameter model is developed for prediction and control of the damper's behavior in real-time. PID and sliding mode controllers are developed and compared for implementation of the damper, in light of its semi-active capabilities. Finally, both model and controller are implemented in a control structure with a joint simulator to evaluate potential utility in an orthotic platform for the suppression of tremorous motion. The results are compared with those of a tuned suppression approach, wherein the applied current is held constant to yield a comparable degree of suppression of the fundamental tremor frequency. The active control method is found to decrease the additional work load on the patient by an average of 13%, while reducing the average power requirement by nearly an order of magnitude. |
