Vibrotactile actuators are used in many different haptic devices, e.g. game controllers and smartphones. These vibrotactile actuators are typically made of rigid materials. In this work, we use soft pneumatic actuators known as Pneumatic Unit Cell (PUC) to characterize the perceived intensity of vibrotactile stimuli when presented at the tip of the index finger. This study investigates how three parameters—stimulus pressure (4 to 30 kPa), inflation-deflation frequency (20 to 100 Hz), and actuator stiffness (determined by top layer thicknesses of 0.9 mm and 1.2 mm)—influence the perceptual intensity of the stimuli. Psychophysical experiments involving 16 participants were conducted using the AEPsych toolbox.
Statistical analysis was conducted to assess the influence of the three parameters on perceived vibrotactile intensity. A 3×3 repeated-measures ANOVA was performed at nine representative pressure-frequency combinations to evaluate the main effects of pressure and frequency for each actuator design. To examine interaction effects, two separate one-way repeated-measures ANOVA tests were conducted for each actuator design to compare the Just Noticeable Differences (JNDs) across three pressure slices (33 Hz, 63 Hz, and 93 Hz) and three frequency slices (10 kPa, 18 kPa, and 26 kPa). The mean of JNDs (mean of pressure slices JNDs and mean of frequency slices JNDs) were then used to compare the relative influence of pressure and frequency, using a paired t-test for the 0.9 mm PUC actuator and a Wilcoxon signed-rank test for the 1.2 mm PUC actuator. To analyze the effect of actuator stiffness, we evaluated the frequency adjustment required at 17 kPa and the pressure adjustment required at 60 Hz in the 1.2 mm PUC actuator to match the perceived intensity of a reference stimulus from the 0.9 mm PUC actuator. A paired t-test was performed in both cases to determine the influence of actuator stiffness.
These reveal that all the three parameters - pressure, frequency, and actuator stiffness significantly affect perceptual intensity. The findings indicate that both pressure and frequency exhibit a positive main effect and a positive interaction effect on perceived vibrotactile intensity. Additionally, the results show that, for a given frequency, pressure variations produce more perceptually distinct stimuli than frequency variations for a given pressure. Finally, presenting vibrotactile stimuli on a less stiff PUC actuator was perceived as being less intense than when the same stimulus was presented on a stiffer PUC actuator. Overall, this study provides key insights into the combined influence of pressure, frequency and actuator stiffness on the perceived vibrotactile intensity.
" authors: - family-names: Kommuri given-names: Krishna Dheeraj orcid: "https://orcid.org/0009-0005-9934-1781" - family-names: van Beek given-names: Femke orcid: "https://orcid.org/0000-0003-4741-6196" - family-names: Kuling given-names: Irene orcid: "https://orcid.org/0000-0003-3556-0393" title: "Data underlying the publication: Perceived Intensity of Pneumatic Vibrotactile Stimuli: Effects of Pressure, Frequency, and Stiffness" keywords: version: 1 identifiers: - type: doi value: 10.4121/1c783e5a-b8dd-48a0-8d02-67554c7ea2b0.v1 license: CC BY 4.0 date-released: 2025-04-02