A stiffness adjustment mechanism maximally utilizing elastic energy of a linear spring for a robot joint

This paper proposes a mechanism that adjusts mechanical stiffness around a robot joint and utilizes whole elastic energy of an elastic element. The proposed mechanism consists of a lead screw mechanism, a linear spring, and wires. The lead screw mechanism moves a nut of the lead screw mechanism to change a bending point of the wire, which connects the linear spring and the lead screw mechanism. Then, moment arm and ratio of joint rotation to extension of the spring are varied. As a result, joint stiffness is adjusted. Because this mechanism does not apply tension to the spring for the stiffness adjustment, whole elastic energy of the spring can be utilized for joint rotation. This utilization can minimize weight and size of the elastic element. Additional advantages of the proposed mechanism are mechanical simplicity, wide range of adjustable stiffness, and no energy consumption for keeping constant stiffness. We analyze characteristics of the proposed mechanism and compare with other mechanisms in detail. Device development and experimental results are provided for demonstrating the effectiveness of the proposed mechanism. Graphical Abstract

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

[2]  Sadao Kawamura,et al.  Generation of energy saving motion for biped walking robot through resonance-based control method , 2009, 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[3]  Nikolaos G. Tsagarakis,et al.  MACCEPA 2.0: Adjustable compliant actuator with stiffening characteristic for energy efficient hopping , 2009, 2009 IEEE International Conference on Robotics and Automation.

[4]  Masafumi Okada,et al.  Simultaneous optimization of robot trajectory and nonlinear springs to minimize actuator torque , 2012, 2012 IEEE International Conference on Robotics and Automation.

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

[6]  Russ Tedrake,et al.  Efficient Bipedal Robots Based on Passive-Dynamic Walkers , 2005, Science.

[7]  Jun Nakanishi,et al.  Stiffness and temporal optimization in periodic movements: An optimal control approach , 2011, 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[8]  Jae-Bok Song,et al.  Hybrid dual actuator unit: A design of a variable stiffness actuator based on an adjustable moment arm mechanism , 2010, 2010 IEEE International Conference on Robotics and Automation.

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

[10]  Sadao Kawamura,et al.  Motion Control With Stiffness Adaptation for Torque Minimization in Multijoint Robots , 2014, IEEE Transactions on Robotics.

[11]  Yoshihiko Nakamura,et al.  Design of programmable passive compliance shoulder mechanism , 2001, Proceedings 2001 ICRA. IEEE International Conference on Robotics and Automation (Cat. No.01CH37164).

[12]  G. Hirzinger,et al.  A new variable stiffness design: Matching requirements of the next robot generation , 2008, 2008 IEEE International Conference on Robotics and Automation.

[13]  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.

[14]  Koichi Koganezawa,et al.  Mechanical stiffness control for antagonistically driven joints , 2005, 2005 IEEE/RSJ International Conference on Intelligent Robots and Systems.

[15]  Takashi Emura,et al.  Energy-preserving control of a passive one-legged running robot , 2004, Adv. Robotics.

[16]  Matthew T. Mason,et al.  Compliance and Force Control for Computer Controlled Manipulators , 1981, IEEE Transactions on Systems, Man, and Cybernetics.

[17]  Shigeki Sugano,et al.  Design and development of a new robot joint using a mechanical impedance adjuster , 1995, Proceedings of 1995 IEEE International Conference on Robotics and Automation.

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

[19]  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.

[20]  Antonio Bicchi,et al.  Embodying Desired Behavior in Variable Stiffness Actuators , 2011 .

[21]  Stefano Stramigioli,et al.  Optimization of Mass and Stiffness Distribution for Efficient Bipedal Walking , 2005 .

[22]  Sadao Kawamura,et al.  A New Control Method Utilizing Stiffness Adjustment of Mechanical Elastic Elements for Serial Link Systems , 2007, Proceedings 2007 IEEE International Conference on Robotics and Automation.

[23]  Sadao Kawamura,et al.  A new mechanical structure for adjustable stiffness devices with lightweight and small size , 2010, 2010 IEEE/RSJ International Conference on Intelligent Robots and Systems.