A comparison of two control-display gain measures for head-controlled computer input devices.
We compared two gain measures: One, defined as angle/angle (A/A) gain, is the ratio between the angle subtended by displacement of the cursor and the corresponding angle of head extension/flexion or rotation. The alternative measure, defined as displacement/angle (D/A) gain, is the ratio between the linear displacement of the cursor on the screen and the corresponding angle of head extension/ flexion or rotation. A discrete target acquisition task using circular targets was used to compare control-display gain measures. Operator performance was evaluated for three viewing distances and three gain settings of each measure. Average movement time and root mean squared (RMS) cursor deviation from a straight line path increased as viewing distance increased for A/A gain settings 0.75 and 1.0. That no significant distance effect was observed for any of the D/A gain settings indicated that it might be more suitable to fix D/A gain rather than A/A gain for head-controlled computer input devices. Minimum movement time occurred for D/A gain settings of 0.5 cm/degree and 0.67 cm/degree. One explanation for the observed insensitivity of performance to changes in viewing distance with a fixed D/A gain may be that both angular head movement and the accompanying kinesthetic feedback do not change for a specified cursor displacement as viewing distance is changed.
Schaab
J A
JA
University of Wisconsin, Madison 53706, USA.
Radwin
R G
RG
Vanderheiden
G C
GC
Hansen
P K
PK
D000328:Adult; D006804:Ergonomics / Q000295:instrumentation*; D005260:Female; D019416:Head Movements / Q000502:physiology; D006801:Humans; D016018:Least-Squares Analysis; D016014:Linear Models; D008297:Male; D012656:Self-Help Devices; D014584:User-Computer Interface