In environments where knobs are frequently damaged by mechanical wear or seepage of liquids, the use of sealed substitutes without moving parts has been tested. In this case, users slide their fingers around a still cylinder rather than rotating a knob. A comparative experiment is reported in this paper, in which participants were asked to perform rotation gestures by specific angles on either a rotary or motionless knob, both hidden to sight. Concerning rotation performance, no significant differences were measured in terms of mean accuracy and precision; however, sliding caused larger deviations in the final position of the fingers. In parallel, a questionnaire unveiled issues of affordability of the motionless knob. Our experiment is preliminary to the realization and validation of a haptic rotation sensing technology applicable to graspable motionless cylinders.
