A rotary magnetorheological fluid damper for pathological tremor suppression

This study explores the development of a new configuration of rotary magnetorheological fluid damper (MR damper) for pathological tremor suppression. In order to be attached to portable rehabilitation robot developed for practical application in robot assisted therapy, the proposed MR damper aims for design of compact size, light weight and enough output torque (about 4.5 Nm). An approach to form serpentine magnetic path by employing an offset electromagnetic coil and an asymmetric rotor is utilized to obtain a large radius and high area utilization rate of the magnetorheological fluid layer (thickness<1 mm) which is exposed to external magnetic field. Electromagnetic analytical methods and FEM numerical simulation are conducted for dimensioning and optimization. Design methods for compact size and light weight are proposed and could be viewed as an effective way to expand the application fields of MR damper. Finally, the output torque characteristic of the damper is evaluated and the tremor suppression experiment is conducted to verify the proposed design. The experiment results prove the effectiveness of MR damper in pathological tremor suppression. Compared with an existed MR damper (axial length 90 mm) for pathological tremor suppression, our 58 mm shorter prototype MR damper can generate 2 times more torque and weigh 40% lighter.