A Multimodal Haptic Rendering System Combining Force and Vibrotactile Feedback

We present a multimodal haptic rendering system that integrates normal force feedback via an airbag and vibration feedback through a piezoelectric vibrator, simulating the hardness and roughness of samples. For hardness rendering, the system utilizes local stiffness (LS) as a critical control parameter of the airbag to enhance user perception of sample hardness during compression. For roughness rendering, we introduce a texture mapping method that extracts roughness from texture images based on Tamura coarseness and maps it to the frequency of the piezoelectric vibrator’s drive voltage, enabling the perception of roughness during horizontal interactions with the sample. User studies are conducted to evaluate the system. Results indicate that the LS effectively mirrors the sample’s transient stiffness, significantly enhancing hardness perception. This multimodal approach demonstrably exceeds single-modal systems in replicating realistic sensory experiences. Moreover, our findings reveal that vibrational stimuli also influence the perception of hardness.