WeHAPTIC-light: A cable slack-based compact hand force feedback system for virtual reality

Various force feedback devices for the hand have been developed for the virtual reality field, but many systems are heavy, and various functions have not been fully developed with respect to finger motion measurement and stiffness generation. We propose a light and wearable force feedback device that can measure finger motion without calibration and can implement different stiffnesses using a cable slack-based mechanism. The proposed system has a small weight of 298 g, using a 10 g motor. To measure finger motion without calibration, an equation for each finger joint angle is derived from the three-dimensional position and orientation information of the fingertip. To realize different stiffnesses, the proposed system connects a motor and a finger structure with a cable; zero impedance is realized by maintaining a slack. The adjustable cable slack mechanism ensures to restrict the finger motion when the fingertip touches the surface of a virtual object even in fast motion; different stiffnesses are realized by proportional control input to the motor according to the deformation of the virtual object. We manufactured a prototype for three fingers and experimentally verified the performance of the proposed system.