Controlled-STM: A Two-stage Model to Predict User’s Perceived Intensity for Multi-point Spatiotemporal Modulation in Ultrasonic Mid-air Haptics

Multi-point STM offers a great range of parameters (i.e., drawing frequency, number of points) to produce different tactile sensations. However, existing studies offer limited insight on the effects of these parameters, and ignore their effect on the physical stimuli delivered, limiting effective haptic design. We propose a two-stage model to predict response to multi-point STM. The first stage predicts physical stimulus properties with 7.8% error, while the second stage predicts mean and spread of perceived intensity with 8.0 % and 8.8% error. We report 3 studies conducted to derive this model: one to characterize physical stimuli, another one measuring user perceptual thresholds, and a third one measuring user's perceptual response to multi-point STM. Besides, we characterize 4 effects that influence device performance, confirm if previous effects reported are due to physical or perceptual effects (or both) and derive recommendations for manufacturers, haptic designers and HCI researchers.