Brais Gonzalez Sousa’s research while affiliated with TU Dresden and other places

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Publications (2)


Fig. 1. Actuation time course of the SMA arm-sleeve, plaster arrangement and experimental setup. The actuation time course (left) shows onsets of plaster actuations (coloured rectangles) for different overlap durations. Note that if a row was actuated, all plasters in that row were actuated simultaneously with the same stimulation pattern and duration (1000ms). The analysis time window for facial EMG activities was 0 to 6000 ms. The plaster matrix (middle) depicts the layout of the SMA-wired arm-sleeve with five rows (R) of plasters (P). Note that the tiny gaps between the plasters shown here are only for illustration; the actual arm-sleeve had no such gaps. Experimental setup (right) shows an example participant wearing facial EMG recording electrodes and the arm-sleeve on his left forearm.
Fig. 3. Behavioral ratings for different parameter combinations of the SMA arm-sleeve. Results for linear mixed models are plotted with points and bars showing estimated marginal means (EMMs) for (a) continuity ratings and (b,c) intensity ratings, respectively. Standard errors are plotted as error bars. ns: not significant, p > .05, **p < .01, ***p < .001
Evaluating Affective Touch Generated via a Shape-Memory-Alloy Arm-Sleeve by Subjective Report and Facial Muscle Activity
  • Article
  • Full-text available

January 2024

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12 Reads

IEEE Transactions on Haptics

Brais Gonzalez Sousa

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Robert Rosenkranz

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Realistic actuation of social touch remains a pressing challenge. This study evaluated a shape-memory alloy (SMA) based arm-sleeve, which actuated touch patterns in the range of C-tactile optimal velocity (3 to 4.5 cm/s) that is known to evoke pleasant affect. We manipulated the intensity (238, 289 & 340 mA) and overlap (0, 187 & 375 ms) of the actuation. Twenty-one participants rated the perceived continuity and intensity of the resulting stroking and tapping patterns. Their psychophysiological reactions of pleasantness derived from activities of the zygomaticus major muscle were also measured by facial electromyography (EMG). At the highest actuation intensity (340 mA), greater differences in perceived continuity between conditions of actuation overlaps were observed (p < .001), with the highest continuity rating for an overlap of 375 ms. Relative to other conditions, this parameter combination elicited higher facial muscle activities of positive affect (p < .001). Crucially, individual differences in perceived continuity and psychophysiological reactions of positive affect correlated positively. These findings (i) extend evidence of pleasant responses elicited by human touch and touch by haptic actuators and (ii) establish a psychophysiologically based perceptual benchmark for designing haptic devices to render affective touch.

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Fig. 2. Schematic drawing of the armband array. Numbered circles mark the positions of the actuators. Grey lines show the subdivision of the area in triangles for the algorithm.
Fig. 3. Illustration of the algorithm output for a uniformly moving vibration (from actuator 1 to actuator 4). The upper plots show the generated signal for the vibration without (left) and with (right) amplitude modulation. The lower plot shows this signal as calculated by the algorithm for every actuator (as indicated by color below) with quadratic interpolation. The signals are displayed in time domain.
Fig. 4. Armband with actuator housing, wiring and predominant direction of vibration (arrows) of the actuator array in (a). Backside of the housing with silicone knob (10 mm diameter, 4 mm height) that provides skin contact in (b).
Fig. 5. Ratings of stimuli, averaged over combinations of amplitude modulation. Means of plausibility, continuity and pleasantness ratings are plotted for all combinations of intensity, signal shape (S for sinusoidal and C for combined, i.e. sinusoidal+noise signals), frequency and velocity. The two columns show high (left) and low (right) intensity, respectively. Points give means with ± standard error as error bars.
Fig. 8. Photograph of the experimental setup for multimodal context scenes, with participant.
Phantom Illusion Based Vibrotactile Rendering of Affective Touch Patterns

September 2023

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149 Reads

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2 Citations

IEEE Transactions on Haptics

Physically accurate (authentic) reproduction of affective touch patterns on the forearm is limited by actuator technology. However, in most VR applications a direct comparison with actual touch is not possible. Here, the plausibility is only compared to the user's expectation. Focusing on the approach of plausible instead of authentic touch reproduction enables new rendering techniques, like the utilization of the phantom illusion to create the sensation of moving vibrations. Following this idea, a haptic armband array (4x2 vibrational actuators) was built to investigate the possibilities of recreating plausible affective touch patterns with vibration. The novel aspect of this work is the approach of touch reproduction with a parameterized rendering strategy, enabling the integration in VR. A first user study evaluates suitable parameter ranges for vibrational touch rendering. Duration of vibration and signal shape influence plausibility the most. A second user study found high plausibility ratings in a multimodal scenario and confirmed the expressiveness of the system. Rendering device and strategy are suitable for a various stroking patterns and applicable for emerging research on social affective touch reproduction.

Citations (1)


... The sense of touch operates with a more precise temporal resolution than vision and hearing 17 ; therefore, including tactile information into digitalized environments could further enhance virtual experiences. Possibilities to integrate touch into digital and communication technologies are presently being intensively researched and evaluated 16,18,19 . When these technologies are matured, they could provide new multisensory experiences for humans to perceive in virtual (or remote) environments through digitalized tactile and kinematic information 10,20 , besides visual and auditory signals. ...

Reference:

Cortical processes of multisensory plausibility modulation of vibrotactile perception in virtual environments in middled-aged and older adults
Phantom Illusion Based Vibrotactile Rendering of Affective Touch Patterns

IEEE Transactions on Haptics