Manual Detection of Spatial and Temporal Torque Variation through a Rotary Switch

We report three experiments on manual detection of torque variations experienced through a rotary switch. The experiments were designed to investigate whether torque perception was determined by the spatial or by the temporal characteristics of the rotary switch. In Exp. I, manual detection thresholds of torque variation were measured with raised sinusoidal torque profiles that varied in spatial period from 2.8deg to 180deg per cycle. In Exp. II, the same was measured for torque profiles that varied in temporal frequency from 2 to 300 Hz. Exp. III was similar to Exp. 1 except that the participants were required to turn the rotary switch at two different speeds for each of seven spatially specified torque profiles (spatial period: 2.8deg to 90deg per cycle). A comparison of the thresholds obtained in Exp. III and those in Exps. I and II suggests that the detection of torque variations depends on the spatial, not temporal, specification of the torque profiles. Our results can potentially shed new light on the design and engineering specification of rotary switches.