M.  Mancini, Grioli, G., Catalano, M. G., Garabini, M., Bonomo, F., and Bicchi, A., ?Passive impedance control of a Qboid multi-DOF VSA-CubeBot manipulator?, in International Conference of Robotics and Automation - ICRA 2012, Saint Paul, MN, USA, 2012, pp. 3335 - 3340 .