Shape and friction recognition of 3D virtual objects by using 2-DOF indirect haptic interface

In this study, a haptic rendering method named indirect haptic feedback is proposed. In traditional haptic interfaces for the index finger, the contact point of the finger and the point of application of force are the same when touching a virtual object. As a result, in the augmented reality environment, a user is unable to touch a real object with his/her bare hand through traditional haptic interfaces. In this study, separate contact and reaction force points are selected for haptic rendering. To realize this, a prototype system, which consists of a motion tracker, a 2-DOF haptic interface that is equipped with a force sensor, and a visual display, is developed. The system measures the position of the fingertip of a user and produces an appropriate horizontal force on the thenar eminence (the group of muscles on the palm of the human hand at the base of the thumb) of the user. Through the visio-haptic interface, a user can perceive the surfaces of 3D virtual objects. In addition, the user can perceive the frictional force on the surface of the objects. Through two evaluation tests, it was verified that the subjects could effectively perceive the 3D virtual objects using this system.