On the stiffness design of intrinsic compliant manipulators

The incorporation of intrinsic compliance in robotic actuation systems has attracted the attention during recent years due to the considerable benefits which is not possible to achieve with conventional “stiff” actuation systems. However, despite the numerous compliant robots developed, a systematic method for tuning the passive elasticity of the individual joints is still missing. This tuning is typically performed using experimental trial and error processes and very little information on the criteria and methodologies used is available. This work studies the effects of passive compliance on the key parameters of the robotic systems including natural frequency, damping ratio, Cartesian stiffness and energy storage capacity. Criteria are then defined based on the desired performance of the system; and a method for the selection of the passive stiffness of compliant actuated arms is introduced. The proposed method is evaluated on a four degrees of freedom (DOF) compliant arm and the compliance of its joints is tuned. The sensitiveness of the main dynamic and static parameters of the robot with respect to the stiffness of joints is illustrated to show the effect of the compliance of each individual joint.

[1]  Nikolaos G. Tsagarakis,et al.  A compact compliant actuator (CompAct™) with variable physical damping , 2011, 2011 IEEE International Conference on Robotics and Automation.

[2]  Stephen P. DeWeerth,et al.  Biologically Inspired Joint Stiffness Control , 2005, Proceedings of the 2005 IEEE International Conference on Robotics and Automation.

[3]  D. Chablat,et al.  Stiffness Matrix of Manipulators With Passive Joints: Computational Aspects , 2012, IEEE Transactions on Robotics.

[4]  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.

[5]  S. E. Semercigil,et al.  Joint Stiffness Control of a Two-Link Flexible Arm , 2000 .

[6]  Sadao Kawamura,et al.  Resonance-based motion control method for multi-joint robot through combining stiffness adaptation and iterative learning control , 2009, 2009 IEEE International Conference on Robotics and Automation.

[7]  Nicholas Roy,et al.  Exploiting Passive Dynamics with Variable Stiffness Actuation in Robot Brachiation , 2013 .

[8]  Delbert Tesar,et al.  Optimal actuator stiffness distribution for robotic manipulators based on local dynamic criteria , 1985, Proceedings. 1985 IEEE International Conference on Robotics and Automation.

[9]  Jian S. Dai,et al.  Stiffness Design for a Spatial Three Degrees of Freedom Serial Compliant Manipulator Based on Impact Configuration Decomposition , 2013 .

[10]  N. G. Tsagarakis,et al.  Dynamic modeling and adaptable control of the CompAct™ arm , 2013, 2013 IEEE International Conference on Mechatronics (ICM).

[11]  Jonathan W. Hurst,et al.  Optimal passive dynamics for torque/force control , 2010, 2010 IEEE International Conference on Robotics and Automation.

[12]  Nikolaos G. Tsagarakis,et al.  CompAct Arm™: a Compliant Manipulator with Intrinsic Variable Physical Damping , 2012, Robotics: Science and Systems.

[13]  Antonio Bicchi,et al.  Optimality principles in variable stiffness control: The VSA hammer , 2011, 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[14]  Nikolaos G. Tsagarakis,et al.  Safe human robot interaction via energy regulation control , 2009, 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[15]  Nikolaos G. Tsagarakis,et al.  Optimal control for maximizing velocity of the CompAct™ compliant actuator , 2013, 2013 IEEE International Conference on Robotics and Automation.

[16]  Nikolaos G. Tsagarakis,et al.  A new variable stiffness actuator (CompAct-VSA): Design and modelling , 2011, 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[17]  Taro Nakamura,et al.  Derivation of nonlinear dynamic model of novel pneumatic artificial muscle manipulator with a magnetorheological brake , 2012, 2012 12th IEEE International Workshop on Advanced Motion Control (AMC).

[18]  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.

[19]  Zexiang Li,et al.  Natural frequency based optimal design of a two-link flexible manipulator , 2009, 2009 IEEE International Conference on Robotics and Automation.

[20]  Nikolaos G. Tsagarakis,et al.  The design of the lower body of the compliant humanoid robot “cCub” , 2011, 2011 IEEE International Conference on Robotics and Automation.

[21]  Alin Albu-Schäffer,et al.  State feedback damping control for a multi DOF variable stiffness robot arm , 2011, 2011 IEEE International Conference on Robotics and Automation.

[22]  Nikolaos G. Tsagarakis,et al.  Antagonistic and series elastic actuators: a comparative analysis on the energy consumption , 2009, 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[23]  S. Vijayakumar,et al.  Exploiting variable physical damping in rapid movement tasks , 2012, 2012 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM).

[24]  Nikolaos G. Tsagarakis,et al.  AwAS-II: A new Actuator with Adjustable Stiffness based on the novel principle of adaptable pivot point and variable lever ratio , 2011, 2011 IEEE International Conference on Robotics and Automation.

[25]  John Kenneth Salisbury,et al.  A New Actuation Approach for Human Friendly Robot Design , 2004, Int. J. Robotics Res..

[26]  T. Caughey,et al.  Classical Normal Modes in Damped Linear Dynamic Systems , 1960 .

[27]  Nikolaos G. Tsagarakis,et al.  A variable physical damping actuator (VPDA) for compliant robotic joints , 2010, 2010 IEEE International Conference on Robotics and Automation.

[28]  H. Harry Asada,et al.  Optimal compliance design for grinding robot tool holders , 1985, Proceedings. 1985 IEEE International Conference on Robotics and Automation.