Haptic Rendering

The user has to be given a realistic sensation that he or she is actually touching and manipulating physical objects. Motions made by a user modify the models specifying the virtual world appropriately. We employ Orin's nonlinear viscoelastic surface model and Ellis' force impulse method to ensure energy conservation during surface interactions [JMH97]. Stick-slip friction is simulated according to a modification of Karnopp's method. It was recently shown that this stick-slip model approximately models the human fingerpad [NH98], thus leading to a realistic feel. Virtual two-fingered grasping has also been implemented [MH98].

As the user sets virtual objects in an assembly into motion, appropriate inertial and contact forces have to be generated and the positional evolution predicted. Coordinate systems have to be established to allow flexible redefinition of assemblies and chains. We employ a stiffness model of haptic interaction: the user generates displacements, and the simulation returns forces and torques. Consequently, an inverse dynamics solution is required [NN98].

Efforts have also been expended on the master for gravity compensation [DM96] and on new approaches towards kinematic calibration [MI97].

JMH97	Hollerbach, J.M., Cohen, E., Thompson, W.B., Freier, R., Johnson, D.E., Nahvi, A., Nelson, D.D., Thompson II, T.V., and Jacobsen, S.C., "Haptic interfacing for virtual prototyping of mechanical CAD designs," ASME Design for Manufacturing Symposium, (Sacramento, CA), Sept. 14-17, 1997.
HT99	Hollerbach, J.M., Thompson, W.B., and Shirley, P., ``The convergence of robotics, vision, and computer graphics for user information,'' Intl. J. Robotics Research, 18, 1999, pp. 1088-1100.
JMH00	Hollerbach, J.M., `` Some current issues in haptics research,'' Proc. IEEE Intl. Conf. Robotics and Automation, San Francisco, April 24-28, 2000, pp. 757-762.
MH98	Maekawa, H., and Hollerbach, J.M., ``Haptic display for object grasping and manipulating in virtual environment,'' Proc. IEEE Intl. Conf. Robotics & Automation, Leuven, Belgium, May 16-21, 1998, pp. 2566-2573.
NH98	Nahvi, A., and Hollerbach, J.M., " Display of friction in virtual environments based on human finger pad characteristics," Symp. Haptic Interfaces, Proc. ASME Dynamic Systems and Control Division, DSC-Vol. 64, Anaheim, CA, Nov. 15-20, 1998, pp. 179-184.
NN98	Nahvi, A., Nelson, D.D., Hollerbach, J.M., and Johnson, D.E., `` Haptic manipulation of virtual mechanisms from mechanical CAD designs,'' Proc. IEEE Intl. Conf. Robotics & Automation, Leuven, Belgium, May 16-21, 1998, pp. 375-380.