Instantaneous stiffness effects on impact forces in human-friendly robots

Joint stiffness plays an important role in both safety and control performance, particularly in human-friendly robots using artificial pneumatic muscles. Due to the limited control bandwidth of pneumatic muscles, stiffness characteristics and their effects on safety in the frequency domain should be taken into account. This paper introduces the concept of instantaneous stiffness and validates its model with the Stanford Safety Robot (S2ρ. The potential effects of instantaneous stiffness on safety is explored through experimental comparison of peak impact accelerations under various impact conditions. Instantaneous stiffness demonstrates different effects on the impact acceleration depending on impact velocity and controller gain. Finally, the paper discusses the stiffness characteristics as a guideline for design and control to improve the robot safety while maintaining the control performance.

[1]  Oussama Khatib,et al.  Analysis of torque capacities in hybrid actuation for human-friendly robot design , 2010, 2010 IEEE International Conference on Robotics and Automation.

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

[3]  Alin Albu-Schäffer,et al.  Safe Physical Human-Robot Interaction: Measurements, Analysis and New Insights , 2007, ISRR.

[4]  Michael R. Zinn,et al.  A New Actuation Approach for Human Friendly Robot Design , 2004, Int. J. Robotics Res..

[5]  Oussama Khatib,et al.  Design and development of high-performance torque-controlled joints , 1995, IEEE Trans. Robotics Autom..

[6]  Blake Hannaford,et al.  Measurement and modeling of McKibben pneumatic artificial muscles , 1996, IEEE Trans. Robotics Autom..

[7]  John Duncan,et al.  A Lumbar Spine Modification to the Hybrid III ATD For Aircraft Seat Tests , 1999 .

[8]  Stefano Stramigioli,et al.  Towards a novel safety norm for domestic robotics , 2007, 2007 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[9]  Sungchul Kang,et al.  Design of a robot joint with variable stiffness , 2008, 2008 IEEE International Conference on Robotics and Automation.

[10]  John Kenneth Salisbury,et al.  Preliminary design of a whole-arm manipulation system (WAMS) , 1988, Proceedings. 1988 IEEE International Conference on Robotics and Automation.

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

[12]  Alin Albu-Schäffer,et al.  DLR's torque-controlled light weight robot III-are we reaching the technological limits now? , 2002, Proceedings 2002 IEEE International Conference on Robotics and Automation (Cat. No.02CH37292).

[13]  P. Beyl,et al.  The Role of Compliance in Robot Safety , 2010 .

[14]  Michael R. Zinn,et al.  A new actuation approach for human-friendly robotic manipulation , 2005 .

[15]  Oussama Khatib,et al.  Design and Control of a Bio-inspired Human-friendly Robot , 2010, ISER.

[16]  Takeo Kanade,et al.  Design of Direct-Drive Mechanical Arms' , 1983 .

[17]  Oussama Khatib,et al.  A hybrid actuation approach for human-friendly robot design , 2008, 2008 IEEE International Conference on Robotics and Automation.