A system for evaluating the effect of keyboard design on force, posture, comfort, and productivity

Abstract

The purpose of this study was to develop a system to determine the effectiveness of an alternative keyboard design which aimed to reduce fingertip force and awkward wrist postures. A prototype alphanumeric keyboard, adjustable in four ways, was developed for this study. Four measurements were chosen to determine the effectiveness of each keyboard configuration: fingertip impact force; wrist position; productivity; and comfort and ease of use. Fingertip force was measured using instrumented keys that had strain gauges located between the key cap and the key switch. Wrist position was measured using electronic goniometers attached to the forearms and hands of the test subjects. A computer program was developed to measure productivity, and a questionnaire based on the Borg rating scale was developed to measure comfort and ease of use. The system was tested to ensure its accuracy. Linearity, repeatability, strike position sensitivity, and natural frequency of the instrumented keycap assembly were assessed. Output of the electric goniometers was compared with readings on a manual goniometer to ensure the former's accuracy over the range of wrist angles expected during keyboard operations. Results of the validation indicated that the system is capable of measuring fingertip force and wrist angle accurately and repeatably. The system described in this paper is the first one that measures fingertip force, wrist position, productivity, and comfort and ease of use simultaneously.