The “Feel” of Rotary Controls: Friction and Inertia1

The purpose of this study was to determine the influence of friction and inertia levels on the “feel” of rotary controls. Detection thresholds for changes in friction and inertia were determined and found to be about 10 to 20 per cent of the initial values. Preference ratings obtained for various combinations of friction and inertia increased as a function of inertia level and decreased as a function of friction level. Preferences for viscous friction were greater than for stick-slip friction. Psychophysical evaluations such as these are related to customer acceptance factors and provide a useful supplement to purely functional design criteria.