Modulating Effort Sensations in Virtual Reality: A Parameter-Based Haptic Feedback Approach.

Virtual reality is becoming increasingly popular, and modern haptic equipment, such as vibrotactile suits, haptic gloves, and force-feedback controllers, offers new means of interaction within virtual environments, significantly enhancing user experience. When interacting with virtual objects, combined visual and haptic feedback simulates the physical sensations of grasping, lifting, or moving real objects. This sensorimotor feedback is essential for inducing a sense of presence and agency, yet it remains challenging to reproduce in the absence of reliable haptic cues. In this study, we design and evaluate several haptic metaphors using combinations of vibrotactile design parameters to simulate the lifting effort associated with light to heavy objects. These parameters include primitive signals, intensity, spatial density, propagation, and temporal density. Our contribution is threefold. First, we propose a method for modulating perceived physical effort by extending signal intensity with spatial and temporal density, which together reflect the effort required to lift an object. Second, we present a user study in which participants compared haptic effects and ranked them according to perceived lifting effort, comfort, and confidence, allowing us to assess the influence of each parameter. Third, we report the results of a second study in which participants evaluated vibrotactile effects when lifting different virtual objects. The findings confirm the importance of intensity and spatial density, as well as the influence of graphical representation on perceived effort. This research provides practical insights for designing haptic-enabled virtual reality systems and offers guidance for developers seeking to create more expressive and believable vibrotactile interactions.