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Logo for the Journal of Rehab R&D
Vol. 35 No. 4, October 1998
Pages 373-387

A wearable tremor-suppression orthosis

Jack Kotovsky, MS and Michael J. Rosen, PhD

Department of Mechanical Engineering, University of California, Davis, Davis, CA 95616; Rehabilitation Engineering Service, National Rehabilitation Hospital, Washington, DC 20010-2949

Abstract--The Viscous Beam is a wearable tremor-suppression orthosis that applies viscous resistance to motion of the wrist in flexion and extension. The orthosis reduces tremor amplitude and is small enough to be worn under the sleeve of a shirt. Hand and forearm cuffs couple the damper to the user. The cuffs permit full thumb and finger motion, wrist flexion and extension, and forearm pronation and supination.
Damping is provided by a constrained-layer-damping (CLD) system, distinct in that it can damp large rotary deflections through a small bending radius. A bending-plate transmission linearly converts wrist extension/flexion to rectilinear translation within the damper. Bending deformation of two plates held a fixed distance apart within the transmission results in relative displacement along the lengths of the plates. A viscous fluid incorporated between the plates provides shear damping. Silicone fluids with viscosities as high as 10 million centistokes (cS) and shear layers as thin as 0.76 mm have been tested. With these parameter values, damping constants as high as 2.0×10-3 N-m/(°/s) have been measured. This testing was conducted with strain rates as high as 4,580°/s. The elastic stiffness of this beam was measured to be 4.1×10-2 N-m/°.

Key words: constrained layer damping, orthosis, rotary damper, tremor suppression/reduction/attenuation.

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