Feeling a rigid virtual world through an impulsive haptic display

Abstract

In this paper the first haptic display capable of applying a true impulse to the operator is presented. The applied impulse results in an immediate change of the user's momentum. Such a change is considered to be invaluable in making interactions with rigid virtual objects feel realistic. Conventional methods can only approximate impulses by outputting a constant force over a certain number of sample periods. The quality of these impulses is therefore limited by the maximum torque of the motor. At high interaction velocities these methods lose realism. The usage of large motors not only brings along safety issues, it also compromises the feeling of free motion. The new haptic display can generate an arbitrarily large impulse by continuously adapting the amount of momentum of a momentum wheel. At the predicted instant of contact with the virtual object, an electromagnetic tooth-clutch is engaged. The momentum wheel is mechanically connected to the handle of the haptic display and a real, but controlled, collision between the operator and momentum wheel is realized. The impulse generation part of the device is in fact the first 'generalized encountered haptic display'. Like typical encountered haptic displays its influence is not felt in free motion, but in contrast to them it is not limited to only static encounters, but effectively applicable to make encounters over a full velocity spectrum.