@conference {DLFSB-IROS09,
	title = {Nonlinear Decoupled Motion-Stiffness Control and Collision Detection/Reaction for the VSA-II Variable Stiffness Device},
	booktitle = {Proc. IEEE/RSJ International Conference on Intelligent RObots and Systems},
	year = {2009},
	month = {October, 11 - 15},
	pages = {5487-5494},
	address = {St. Louis MO USA},
	abstract = {<p>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.</p>
},
	keywords = {Embedded Control, Physical Human-Robot Interaction (pHRI), Robotics},
	author = {A. De Luca and F. Flacco and R. Schiavi and A. Bicchi}
}
