Passive impedance control of a multi-DOF VSA-CubeBot manipulator

This work presents an example of the application of passive impedance control of a variable stiffness manipulator, which shows the actual benefits of variable stiffness in rejecting disturbances without resorting to the closure of a high level feedback loop. In the experiment a 4-DOF manipulator arm, built with the VSA-CubeBot platform, is controlled to hold a pen and draw a circle on an uneven surface. The control is designed calculating joint and stiffness trajectories with a Cartesian approach to the problem, thus designing the optimal workspace stiffness at first. Then, the joint stiffness yielding the closest workspace stiffness is searched for. Experimental results are reported, which agree with the theoretical outcomes, showing that the sub-optimal joints stiffness settings allow the arm to follow the circular trajectory on the uneven surface at best.

[1]  R. Ham,et al.  Compliant actuator designs , 2009, IEEE Robotics & Automation Magazine.

[2]  Kazuhito Yokoi,et al.  A Method Of Compliance Control For A Redundant Manipulator , 1992, Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems.

[3]  Kevin Barraclough,et al.  I and i , 2001, BMJ : British Medical Journal.

[4]  Yanmei Li,et al.  A new theory in stiffness control for dextrous manipulation , 2001, Proceedings 2001 ICRA. IEEE International Conference on Robotics and Automation (Cat. No.01CH37164).

[5]  Imin Kao,et al.  Simulation of conservative congruence transformation. Conservative properties in the joint and Cartesian spaces , 2000, Proceedings 2000 ICRA. Millennium Conference. IEEE International Conference on Robotics and Automation. Symposia Proceedings (Cat. No.00CH37065).

[6]  Alin Albu-Schäffer,et al.  The DLR hand arm system , 2011, 2011 IEEE International Conference on Robotics and Automation.

[7]  Mark W. Spong,et al.  On the force control problem for flexible joint manipulators , 1989 .

[8]  Antonio Bicchi,et al.  Fast and "soft-arm" tactics [robot arm design] , 2004, IEEE Robotics & Automation Magazine.

[9]  Matthew M. Williamson,et al.  Series elastic actuators , 1995, Proceedings 1995 IEEE/RSJ International Conference on Intelligent Robots and Systems. Human Robot Interaction and Cooperative Robots.

[10]  W. Brockett,et al.  Minimum attention control , 1997, Proceedings of the 36th IEEE Conference on Decision and Control.

[11]  Keng Peng Tee,et al.  Concurrent adaptation of force and impedance in the redundant muscle system , 2010, Biological Cybernetics.

[12]  Gianluca Palli,et al.  Interaction Force Control of Robots with Variable Stiffness Actuation , 2011 .

[13]  J. Salisbury,et al.  Active stiffness control of a manipulator in cartesian coordinates , 1980, 1980 19th IEEE Conference on Decision and Control including the Symposium on Adaptive Processes.

[14]  Alin Albu-Schäffer,et al.  Safety Evaluation of Physical Human-Robot Interaction via Crash-Testing , 2007, Robotics: Science and Systems.

[15]  Neville Hogan,et al.  Impedance Control: An Approach to Manipulation , 1984, 1984 American Control Conference.

[16]  Alin Albu-Schäffer,et al.  A Unified Passivity-based Control Framework for Position, Torque and Impedance Control of Flexible Joint Robots , 2007, Int. J. Robotics Res..