Simultaneous Force and Stiffness Control of a Pneumatic Actuator

This paper proposes a new approach to the design of a robot actuator with physically variable stiffness. The proposed approach leverages the dynamic characteristics inherent in a pneumatic actuator, which behaves in essence as a series elastic actuator. By replacing the four-way servovalve used to control a typical pneumatic actuator with a pair of three-way valves, the stiffness of the series elastic component can be modulated independently of the actuator output force. Based on this notion, the authors propose a control approach for the simultaneous control of actuator output force and stiffness. Since the achievable output force and stiffness are coupled and configuration-dependent, the authors also present a control law that provides either maximum or minimum actuator output stiffness for a given displacement and desired force output. The general control and maximum/minimum stiffness approaches are experimentally demonstrated and shown to provide high fidelity control of force and stiffness, and additionally shown to provide a factor of 6 dynamic range in stiffness.

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

[2]  Weiping Li,et al.  Applied Nonlinear Control , 1991 .

[3]  Donald Russell,et al.  Implementation of variable joint stiffness through antagonistic actuation using rolamite springs , 1999 .

[4]  Marc H. Raibert,et al.  Legged Robots That Balance , 1986, IEEE Expert.

[5]  N. Heglund,et al.  Energetics and mechanics of terrestrial locomotion. , 1982, Annual review of physiology.

[6]  R. McN. Alexander,et al.  Three Uses for Springs in Legged Locomotion , 1990, 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]  Antonio Bicchi,et al.  Design and Control of a Variable Stiffness Actuator for Safe and Fast Physical Human/Robot Interaction , 2005, Proceedings of the 2005 IEEE International Conference on Robotics and Automation.

[9]  E. Bizzi,et al.  Neural, mechanical, and geometric factors subserving arm posture in humans , 1985, The Journal of neuroscience : the official journal of the Society for Neuroscience.

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

[11]  Antonio Bicchi,et al.  Compliant design for intrinsic safety: general issues and preliminary design , 2001, Proceedings 2001 IEEE/RSJ International Conference on Intelligent Robots and Systems. Expanding the Societal Role of Robotics in the the Next Millennium (Cat. No.01CH37180).

[12]  Koichi Koganezawa,et al.  Mechanical stiffness control of tendon-driven joints , 1999, Proceedings 1999 IEEE/RSJ International Conference on Intelligent Robots and Systems. Human and Environment Friendly Robots with High Intelligence and Emotional Quotients (Cat. No.99CH36289).

[13]  G. Cavagna,et al.  Mechanical work in terrestrial locomotion: two basic mechanisms for minimizing energy expenditure. , 1977, The American journal of physiology.

[14]  J. Edward Colgate,et al.  Design of components for programmable passive impedance , 1991, Proceedings. 1991 IEEE International Conference on Robotics and Automation.

[15]  Donald Russell,et al.  Mechanics and stiffness limitations of a variable stiffness actuator for use in prosthetic limbs , 1999 .

[16]  Neville Hogan,et al.  The mechanics of multi-joint posture and movement control , 1985, Biological Cybernetics.

[17]  Neville Hogan,et al.  Impedance Control: An Approach to Manipulation: Part I—Theory , 1985 .

[18]  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.

[19]  N. Hogan.  Adaptive control of mechanical impedance by coactivation of antagonist muscles , 1984 .

[20]  Joel E. Chestnutt,et al.  An actuator with physically variable stiffness for highly dynamic legged locomotion , 2004, IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004.