IMECE2007-42131 DISTURBANCE OBSERVER BASED CLOSED LOOP FORCE CONTROL FOR HAPTIC FEEDBACK

Most commonly used impedance-type haptic interfaces em-ploy open-loop force control under the assumption of pseudo-static interactions. Advanced force control in such interfaces can increase simulation fidelity through improvement of the trans-parency of the device, and can further improve robustness. How-ever, closed loop force-feedback is limited both due to the band-width limitations of force sensing and the associated cost of force sensors required for its implementation. In this paper, we pro-pose the use of a nonlinear disturbance observer for estimation of contact forces during haptic interactions. This approach cir-cumvents the traditional drawbacks of force sensing while ex-hibiting the advantages of closed-loop force control in haptic de-vices. The feedback of contact force information further enables implementation of advanced robot force control techniques such as robust hybrid impedance and admittance control. Simulation and experimental results, utilizing a PHANToM Premium 1.0A haptic interface, are presented to demonstrate the efficacy of the proposed approach