An enhanced force bounding approach for stable haptic interaction by including friction

Abstract

There is an inherent trade-off between stability and transparency in haptic interaction systems when interacting with virtual environments. Therefore, no perfect transparency can be displayed with absolute stability. For meaningful interactions, anyhow, some level of transparency is necessary for providing realistic feelings. On the other hand, robust stability must absolutely be guaranteed against any virtual environments because unstable behaviors disrupt contact realism completely and/or may also injure human operators. In order to increase magnitude transparency of the haptic interaction system, this paper proposes a way of systematic inclusion of Coulomb friction component in the previous force bounding approach. In the inclusion, two type of force bounding approach are derived. The less conservative condition can generate significantly higher magnitude transparency in terms of the initial contact crispness as well as the steady-state contact force for very stiff virtual objects. However, there occur some contact oscillations to diminish contact realism due to the energy accumulation during free motion. In order to avoid contact oscillations, a more conservative condition is proposed for systematically removing the past accumulated energy. The proposed algorithm is also compared with the other similar algorithm. Comprehensive experimental results are presented to show the effectiveness of the proposed approaches.