The perception of torque pulses

Directional torque perception with brief, asymmetric net rotation of a flywheel

This paper proposes a directional torque feedback technique for mobile devices that creates brief unbalanced torque by suddenly starting to rotate a stationary flywheel and then stopping it soon after. The experimental results show that a twisting sensation was induced effectively with angular velocity profiles that include sudden starts.

Reproducibility of controlled force exertion measurements computed by a quasi-random target-pursuit system

The reproducibility of measurements and measurement error of controlled force exertion was examined based on target-pursuit of quasi-random waveforms. 30 college students were required to match their grip strength to a changing demand value appearing on the display of a personal computer using visual images in the form of four different quasi-random waveforms. The variable was the sum of the differences over time between the demand value and produced grip strength. Intraclass correlation coefficients (ICCs) for measurements one day apart were low or moderate for quasi-random waveform displays, with mean frequencies of 0.01, 0.05, 0.07, and 0.09 Hz (ICCs= .37, .73, .57, and .57, respectively). Measurements at a 1-wk. interval showed statistically significant improvements in performance at all quasi-random waveform frequencies. The total error between test and retest, and the systematic error between tests, remained relatively small as mean frequency increased. Tests that use the quasi-random waveform displays of 0.05 Hz and over can be useful in documenting controlled force exertion.

Reliability of a computerized target-pursuit system for measuring coordinated exertion of force

The purpose was to examine trial-to-trial and day-to-day reliability and sensitivity for measurements of the ability to coordinate exertion of force based on target-pursuit. 30 college students were required to match their grip strength to a changing demand value appearing on the display of a personal computer, using two visual images in the form of a bar chart and waveform. The variable was the sum of the differences between demanded and produced grip strength over time. Analysis indicated high intraclass correlation coefficients (ICC) for bar chart and waveform displays (ICC = .87, ICC = .95, respectively). The limits of agreement, designating the interval comprising 95% of the differences between three measurements in a stable individual, were -14.8 to 99.3% for the bar chart and -3.5 to 113.6% for the waveform displays. One-tailed, paired t tests of the day-to-day measurements showed significant (p < .05) improvement in both the bar chart and waveform displays. ICCs for day-to-day measurements were low-to-moderate for bar chart and waveform displays (ICC = .33 to .71, ICC = .48 to .76, respectively). The limits of agreement between measurements of two trials for day-to-day measurements were -112.2 to 218.6% for the bar chart and -139.2 to 352.8% for the waveform displays. The repeatability coefficients of trial-to-trial and day-to-day measurements for bar chart and waveform displays were 141 and 173%, and 152 and 176%, respectively. The limits of agreement between each test were relatively wide. We believe that these tests, on which the force response is visually guided, can be useful in objectively documenting the ability to coordinate exertion of force.

Role of duration and interval in perception of force pulses

Three experiments investigated the perceptual threshold for a pulsed force stimulation of the middle phalanx of the forefinger. The first experiment (N = 5) manipulated duration of the pulse, and the second (N = 6) manipulated the interval between pulses. Both experiments held magnitude constant. The results confirmed high reliability and indicated that perceptual threshold decreased as both Duration and Interval increased. Although subjects responded consistently, they described the sensation as "muscular" and "diffuse." Exp. 3 (N = 12) covaried Duration and Interval and found effects similar to those of the first two studies. Also, Duration and Interval were independent. Additional research is needed to clarify the relations of duration, interval, and magnitude in contributing to conscious perception of the presence of applied force. Treating pulse magnitude as a dynamic variable by varying its rate of change within a train of force pulses could further our understanding of how perception of force changes depend upon rate.