Parametric study of an enhanced passive absorber used for tremor suppression

Abstract

Passive absorbers are designed to be attached to upper limb systems to reduce tremor of patients suffering from Parkinson's disease. Several works were done previously to show the effectiveness of the low cost passive controllers, which can reduce the undesired vibrations without power requirements. An improved type of such controllers is suggested in this paper. The mechanical absorber is a two-degree-of-freedom (DOF) system, which is formed by an elastic absorber connected in series to a viscous damper one, naming the system the Series Elastic Viscous Damper (SEVD). It was able to cause a high reduction in the amplitude of the tremor and operate over a wide frequency range. The lumped parameters of each absorber within the SEVD absorber are chosen to satisfy the tuning conditions. The device is tested numerically on the forearm of a biodynamic upper limb structure to check its capability in reducing the tremor at the limb's proximal joints. The limb was modeled as rigid segments with a three DOF flexion-extension angular motion in the horizontal plane. This study seeks to analyze the effect of the SEVD damping coefficient, total mass, and mass distribution on the reduction of the displacement amplitude at the joints, with stiffness chosen to satisfy the tuning condition for the undesired frequency of tremor. It was found that very low damping coefficients are not suitable to provide reduction at all joints simultaneously; high absorber's total mass can slightly increase the performance and equally, distributed dual masses can be a good selection.Pharmacotherapy or neurosurgeries through Deep Brain Stimulation are the clinical treatments against such involuntary tremor. The prolonged use of these treatments may cause its deterioration and could leave severe side effects on the patient. In addition, not all patients can respond to these medications. [1] As an alternative solution to medication, involuntary tremor can be treated using mechanical solutions. Such solutions can treat Parkinsonism mechanically and avoid the fatigue, sleep, nausea, poor vision, and muscle paralysis side effects of medications. [3] Passive absorbers can be used to reduce the undesired vibration of the structures without the need of power requirements. In order to increase the effectiveness of the traditional conventional absorbers, Snowdon [4] designed a three-element absorber which is formed by a series connection between the damper and spring connected together in parallel to another spring element. This device showed to be more effective than the conventional absorber. Lavan [5] presented a multi-objective optimized tuned vibration absorber (TVA). It was able to minimize the response of the system with a minimized absorber's mass and stroke. Different configurations were proposed in order to increase the effectiveness of the single-degree-of-freedom (SDOF) absorbers. Snowdon et al. [6] introduced the idea of the two-degree-of-freedom (DOF) conventional parallel absorber. Brennan [7] studied the effect of the multi degree-of-freedom (...

Design and efficiency evaluation of a new wearable device for multi-degree suppression of hand pathological tremor

“…However, the main differences between them consist of the springs’ values. The effect of the total mass, damping coefficient, and mass distribution play an essential role in the reduction of a biomechanical model of upper limb suppression (Gebai et al, 2018).…”