Control Design for a Hand Tremor Suppression Pen

Active feedback control is utilized in this study in order to regulate pen-tip deviations in a novel pen design with the aim to minimize the effects of hand tremors on handwriting. The pen comprises a pendulum-like pen-rod that swings inside a tubular shaped pen casing, and between the pen and the casing, certain compliance and active actuation is considered. Since by the nature of the system dynamics, arbitrary pole placement is not possible in the design of the controller, a nonlinear optimization scheme is constructed to design the controller gains. With these gains, pen-tip deviations are minimized (≈ −47 dB) when the pen casing is subjected tremor-induced cyclic disturbances, and pen-tip response against impulsive perturbations is satisfactorily improved (settling time ≈ 1 sec) while keeping the controller effort around 2 N. Simulation studies are presented comparing the efficacy of the proposed controller with respect to a passively controlled pen, along with trade-offs within the design parameter space.