Mechanical feeding aids for patients with ataxia: design considerations

A mechanism has been designed which transforms steady, vertical hand motion into the scooping motion of a spoon. The mechanism incorporates vibration isolation through a spring-damper system to attenuate the transmission of low frequency (2-8 Hz) hand tremor to the spoon. A series arrangement of spring and damper has produced spoon amplitudes of between 5 and 12% of the hand amplitude at the lowest ataxic tremor frequencies. A prototype has been tested by four ataxic patients. The degree of vibration isolation and the ability to pick up food were adequate but the mechanism was felt to be unacceptable as a feeder for social reasons. Two other mechanisms have also been considered.