TitleNonlinear Decoupled Motion-Stiffness Control and Collision Detection/Reaction for the VSA-II Variable Stiffness Device
Publication TypeConference Paper
Year of Publication2009
Conference NameProc. IEEE/RSJ International Conference on Intelligent RObots and Systems
Date PublishedOctober, 11 - 15
Publication Languageeng
AuthorsDe Luca, A, Flacco, F, Schiavi, R, Bicchi, A
Conference LocationSt. Louis MO USA
KeywordsEmbedded Control, Physical Human-Robot Interaction (pHRI), Robotics

Variable Stiffness Actuation (VSA) devices are being used to jointly address the issues of safety and performance in physical human-robot interaction. With reference to the VSA-II prototype, we present a feedback linearization approach that allows the simultaneous decoupling and accurate tracking of motion and stiffness reference profiles. The operative condition that avoids control singularities is characterized. Moreover, a momentum-based collision detection scheme is introduced, which does not require joint torque sensing nor information on the time-varying stiffness of the device. Based on the residual signal, a collision reaction strategy is proposed that takes advantage of the proposed nonlinear control to rapidly let the arm bounce away after detecting the impact, while limiting contact forces through a sudden reduction of the stiffness. Simulations results are presented to illustrate the performance of the overall approach. Extensions to the multi-dof case of robot manipulators equipped with VSA-II devices are also considered.

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