Soft robotics: what Cartesian stiffness can obtain with passively compliant, uncoupled joints?

In the field of service robotics, whole arm contact with an unstructured environment or human beings becomes a major issue. Therefore soft robots, which mean robots with passively (or mechanically) compliant joints, become more and more important. In this work we analyze what Cartesian stiffness at the tool center point one can achieve with a passively compliant, redundant robot with variable joint stiffness. We restrict this work to the special case of uncoupled joint stiffness only, as coupling of joint stiffness seems to be mechanically difficult to realize. Finally we discuss a Cartesian controller, which incorporates the compliance of the joints and ensures the correct stiffness behavior also for high displacements from the desired position.

[1]  Ernest D. Fasse On the Spatial Compliance of Robotic Manipulators , 1997 .

[2]  Vijay Kumar,et al.  Affine connections for the Cartesian stiffness matrix , 1997, Proceedings of International Conference on Robotics and Automation.

[3]  Antonio Bicchi,et al.  Variable Stiffness Actuators for Fast and Safe Motion Control , 2003, ISRR.

[4]  Shuguang Huang,et al.  The eigenscrew decomposition of spatial stiffness matrices , 2000, IEEE Trans. Robotics Autom..

[5]  Alin Albu-Schäffer,et al.  On a new generation of torque controlled light-weight robots , 2001, Proceedings 2001 ICRA. IEEE International Conference on Robotics and Automation (Cat. No.01CH37164).

[6]  Hiroaki Kobayashi,et al.  On Tendon-Driven Robotic Mechanisms with Redundant Tendons , 1998, Int. J. Robotics Res..

[7]  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.

[8]  Koichi Koganezawa,et al.  Stiffness control of antagonistically driven redundant D.O.F. manipulator , 2002, IEEE/RSJ International Conference on Intelligent Robots and Systems.

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

[10]  N. Hogan Mechanical Impedance of Single- and Multi-Articular Systems , 1990 .

[11]  Stefano Stramigioli,et al.  Modeling and IPC Control of Interactive Mechanical Systems - A Coordinate-Free Approach , 2001 .

[12]  Alin Albu-Schäffer,et al.  Cartesian impedance control techniques for torque controlled light-weight robots , 2002, Proceedings 2002 IEEE International Conference on Robotics and Automation (Cat. No.02CH37292).

[13]  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).

[14]  Joseph Duffy,et al.  Hybrid Twist and Wrench Control for a Robotic Manipulator , 1988 .

[15]  Antonio Bicchi,et al.  Adaptive simultaneous position and stiffness control for a soft robot arm , 2002, IEEE/RSJ International Conference on Intelligent Robots and Systems.