Experimental Testing of Passive Linear TMD for Postural Tremor Attenuation

Research interest to provide a mechanical solution for involuntary tremors is increasing due to the severe side effects caused by the medications used to lessen its symptoms. This paper deals with the design of a cantilever-type tuned mass damper (TMD) used to prove the effectiveness of passive controllers in reducing the involuntary tremor's vibrational signals transmitted by the muscles to the hand segment. TMD is tested on an experimental arm, reflecting the flexion-extension motion of the wrist, excited by a mechanical shaker with the measured tremor signal of a patient with essential tremor. The designed TMD provides a new operational frequency for each position of the screw fixed to its beam. Modal damping ratios are also calculated using different methods for each position. The effectiveness of the TMD is quantified by measurements using a vibrometer and inertial measurement unit. Three TMDs, representing 15.7% total mass ratio, cause a reduction of 29% for the acceleration, 69% for the velocity, 79% for the displacement, 67% for the angular velocity, and 82% for the angular displacement signals. These encouraging results will allow the improvement of the design of the passive controller in the form of a wearable bracelet suitable for daily life.