Vibrotactile Force Perception – Absolute and Differential Thresholds and External Influences

Abstract

Three experiments were carried out to determine absolute and differential thresholds for vibrotactile forces and external influences in the frequency range of 5 to 1,000 Hz at the tip of the index finger. Differential thresholds were obtained for reference stimuli of 0.5, 0.25 N, and near the individual threshold. Frequency, temperature, age, fingertip size, and contact force were investigated as parameters in a full-factorial design. Experiments were conducted with at least 27 subjects and a 1up-2down staircase procedure with 3IFC paradigm. We find absolute thresholds ranging from 1.7 to 19 mN with the lowest threshold at 320 Hz. Weber fractions from 18 to 41 dB are found near the absolute threshold. For larger references, they range from 4.9 to 23 dB. ANOVA finds frequency as significant medium effect for both absolute and differential thresholds. Results imply impact of age on the absolute threshold, but no effect of motor skill, temperature, fingertip size, and contact force. Differential thresholds are affected by frequency only, which is attributed to saturation effects of the Pacinian channel. Fingertip size and motor skill are not able to explain effects on thresholds and the interpersonal variance. Results of this work are intended as requirement source for the design of task-specific haptic interfaces.

Effect of Waveform on Tactile Perception by Electrovibration Displayed on Touch Screens

“…8). We used the human sensitivity functions reported in [42], [43] for the force, acceleration and displacement data, respectively. Moreover, we calculated the corresponding electrostatic forces generated by the same waveforms and amplitudes via Matlab simulations.…”

“…We collected force and acceleration data from fingertips of the subjects while they explored a touch screen displaying electrovibration stimuli at threshold voltages. We analyzed the collected data in frequency domain by taking the human tactile sensitivity curves given in [42], [43] into account. The results suggested that Pacinian was the primary psychophysical channel in the detection of the square wave input signals tested in this study.…”

Influence of surgical gloves on haptic perception thresholds

“…This was either because of limited relevance in the design of task‐specific haptic interfaces (sex, fingertip size, manual dexterity), to lower the number of factor level combinations (temperature was set to 23°C in the room where experiments took place), or in favor of a worst‐case‐approximation (only young subjects were included in the study who exhibit lower thresholds compared with older people). The contact force between finger and contactor, that exhibits strong influences on the mechanical impedance, was not considered, since previous studies by the authors did not find significant effects on perception parameters . The effect of the contact area size is thoroughly described in the existing literature, the combination with wearing a glove does not give grounds to expect any additional effects on the perception thresholds.…”

“…The contact force between finger and contactor, that exhibits strong influences on the mechanical impedance, was not considered, since previous studies by the authors did not find significant effects on perception parameters. 18 The effect of the contact area size is thoroughly described in the existing literature, 19 the combination with wearing a glove does not give grounds to expect any additional effects on the perception thresholds. Therefore, it is not considered in this study.…”

Selective listening attention enhancement, using a simultaneous visual and haptic stimuli

“…Therefore, to compensate for the limitation of the haptic sense to perceive frequency variations, we did not rely on the haptic frequency shift alone to represent the notes of the highlighted instrument. We took advantage of the noticeable capabilities of the somatosensory sense to distinguish small amplitude variations (1.7~19 mN for frequencies at 320Hz) (Hatzfeld, Cao, Kupnik, & Werthschtzky, 2016), so the waveform characteristics of the highlighted instrument were also included in the haptic signal envelope.…”