A COMPARISON OF 2 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 curso r and the corresponding angle of head estension/flexion or rotation. T he alternative measure, defined as displacement/angle (D/A) gain, is t he ratio between the linear displacement of the cursor on the screen a nd the corresponding angle of head extension/flexion or rotation. A di screte target acquisition task using circular targets was used to comp are control-display gain measures, Operator performance was evaluated for three viewing distances and three gain settings of each measure. A verage 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 ob served for any of the D/A gain settings indicated that it might be mor e suitable to fix D/A gain rather than A/A gain for head-controlled co mputer input devices. Minimum movement time occurred for D/A gain sett ings of 0.5 cm/degrees and 0.67 cm/degrees. One explanation for the ob served insensitivity of performance to changes in viewing distance wit h a fixed D/A gain may be that both angular head movement and the acco mpanying kinesthetic feedback do not change for a specified cursor dis placement as viewing distance is changed.