Please consider this paper for presentation as a poster.

Abstract:

Powered wheelchairs are widely used by people with various disabilities to provide independence in indoor and outdoor settings. The control of these devices usually relies on a proportional joystick operated by either hand. It has been identified that there are a large number of potential powered wheelchair users who are unable to effectively operate the joystick due to hand tremor. Tremor forms part of the symptoms of many conditions and may be defined as a regular, roughly sinusoidal oscillatory movement of the affected limb. There is significant variation in both the frequency and amplitude of tremor, depending on the aetiology.

Viscous damping of the affected limb has been shown to reduce oscillations and increase the ability of the user to make fine motor movements. This principle may be applied to the wheelchair controlling joystick with the intention of improving driving accuracy, reducing fatigue and extending joystick life.

This project investigates the damping of tremor using a mathematical modelling approach. The standard joystick is measured in detail, and a model constructed using Mathworks Simmechanics software. A sinusoidal tremor is applied in order to obtain a set of baseline data. The model is then modified to include an element of viscous damping. Various tests are carried out using a range of damping coefficients and tremor input characteristics. Two damping configurations are investigated. The first has simple linear damping, the second uses a damper designed to give a reduced damping coefficient when the joystick is moving toward the neutral position.

The testing identifies that the joystick has a highly non-linear stiffness, giving strong self centring. This has a significant impact on the damping effect. The second configuration is found to provide improved movement reduction, with an acceptable increase in force requirement. A prototype damping unit is described and manufactured.