Perceptual evaluation of the passive/active torque and stiffness asymmetry of a hybrid haptic device

Abstract : Hybrid haptic interfaces combining brakes and motors can present dissimilar torque and stiffness capabilities when dissipating or restoring energy. This paper aims at identifying the asymmetry thresholds that lead to an alteration in the perception of elasticity simulated by such devices. 17 subjects took part in an experiment consisting in interacting with virtual springs with either controllable stiffness or torque asymmetry levels, and identifying if the springs were symmetric or not. Experimental results indicate that when the decompression stiffness or torque were less than 80% and 60% of the compression stiffness or torque respectively, users did not perceive the asymmetry in 80% of trials. This suggests that hybrid devices can present dissimilar active/passive torque or stiffness capabilities without affecting the perception of elasticity.