Voluntary Driven, Velocity Controlled Tremor Suppression

The standard course of treatment for pathological tremor mainly involvespharmacotherapy. However, treatment can be challenging as individual responses totherapy vary widely. Individuals with a disabling or medication refractory tremor, mayhave the option for one of several surgical procedures. Essential Tremor (ET) andParkinson’s Disease (PD) are considered to be among the most pervasive of tremorrelated disorders. Overall pathological tremor prevalence statistics range from 2% to wellover 10% in the elderly. Up to 60% of those affected by tremor experience disability intheir Activities of Daily Living (ADL) and more than a quarter struggle to find reliefthrough conventional treatments. There is, therefore, a persuasive case for alternativetherapies for individuals with pathological tremor. This thesis proposes a tremorsuppression approach to track the intentional motion. Typically tremor suppressionmethods estimate the tremor component and produce a counteracting signal. Thesuggested approach instead predicts the voluntary motion component via forceinformation, while the tremor signal is regarded as a motion disturbance andconsequently rejected. The approach is demonstrated in a modular form for flexibility inimplementation. The suppression approach, involving an admittance and speedcontrolled feedbacks, was evaluated experimentally with a benchtop tremor simulationsystem. Parametric stability and controller tuning were demonstrated, and response timeperformance specifications were achieved. Spectral analysis results show a 99.8%tremor power reduction; the power reduction related to the voluntary movement wasinstead negligible (0.18%). A robotic orthosis was subsequently developed to validatethe approach for the suppression of pathologic elbow tremor. Two types of roboticallysimulated human inputs were evaluated in addition to employing orthosis gravitycompensation. Finally, nine participants with either ET or PD were recruited andperformed computerized pursuit tracking tasks with the orthosis. The mean tremor powerreduction was 94.4%; significantly higher than typically achieved with pharmacotherapy.Importantly, the effect to the voluntary motion was limited to only 6.6%. Whenmechanically suppressing tremor, there is a risk of preventing the individual with tremorfrom performing volitional movements. An important contribution of this work involves theexplicit treatment of the impact to the volitional motion.