Improved Haptic Two-Port Networks Through Force Feedback and Admittance/Impedance Network Duality

This paper uses the two–port network with virtual coupling paradigm to analyze various haptic system architectures. Haptic Two–Port Network (H₂PN) numerical tuning algorithms and analysis techniques based on Llewelyn Stability Criterion are presented and lay the groundwork for testing haptic networks on HuRBiRT (Human Robotic Bilateral Research Tool), a large scale nonlinear hybrid active / passive haptic device. This paper presents the addition of local force feedback to the Impedance / Admittance (I/A) H₂PN to form the true dual of the Admittance / Impedance (A/I) H₂PN and explores alternative impedance and admittance virtual coupling forms. First, I/A and A/I H₂PN’s are numerically tuned using a linearized dynamic model of HuRBiRT and resulting admittance and impedance limits of the respective networks are compared to add insight on the duality of the two different implementations of haptic causality, with specific consideration given to the advantage of adding force feedback to the impedance network and selection of virtual coupling form. Second, I/A and A/I H₂PN’s are experimentally validated on HuRBiRT and resulting experimental networks are directly compared to those numerically formulated through use of HuRBiRT’s linearized dynamic models.