Discrete Foot Shape Changes Improve Dynamics of a Hopping Robot

Legged locomotion is characterised by a repetitive appearance of impulsive ground collisions which are strongly influencing the locomotion behaviour. The collisions depend on the shape of the contacting foot, but little is known on how the foot needs to be shaped to assist stable and fast locomotion. This paper investigates discrepancies in locomotion dynamics caused by a discrete foot shape change. A curved foot, open-loop controlled hopping robot which can be switched between two foot shape states was built and tested for the experimental investigations. The results indicate that the right timing of foot shape change can induce a variety of locomotion gaits and increase maximal speed by up to 40%, without the shape change doing any positive work on the robot. Three distinct take off cases were identified which depend on the robot’s state and foot shape. The switching between the cases in consecutive hops can explain the observed behaviour qualitatively as presented in this paper.

[1]  A. Ruina,et al.  A collisional model of the energetic cost of support work qualitatively explains leg sequencing in walking and galloping, pseudo-elastic leg behavior in running and the walk-to-run transition. , 2005, Journal of theoretical biology.

[2]  J. Grizzle,et al.  Feedback control of an underactuated planar bipedal robot with impulsive foot action , 2005, Robotica.

[3]  M A Lafortune,et al.  Influences of inversion/eversion of the foot upon impact loading during locomotion. , 1995, Clinical biomechanics.

[4]  Vijay Kumar,et al.  Control of locomotion with shape-changing wheels , 2009, 2009 IEEE International Conference on Robotics and Automation.

[5]  M. Coleman,et al.  The simplest walking model: stability, complexity, and scaling. , 1998, Journal of biomechanical engineering.

[6]  X. Mu,et al.  On Impact Dynamics and Contact Events for Biped Robots via Impact Effects , 2006, IEEE Transactions on Systems, Man, and Cybernetics, Part B (Cybernetics).

[7]  Mont Hubbard,et al.  Optimal foot shape for a passive dynamic biped. , 2007, Journal of theoretical biology.

[8]  Yildirim Hurmuzlu,et al.  The role of impact in the stability of bipedal locomotion , 1986 .

[9]  Tad McGeer,et al.  Passive Dynamic Walking , 1990, Int. J. Robotics Res..

[10]  T. Pavlidis.  Stability of systems described by differential equations containing impulses , 1967 .

[11]  A. Kuo,et al.  Mechanical and energetic consequences of rolling foot shape in human walking , 2013, Journal of Experimental Biology.

[12]  Andy Ruina,et al.  Energetic Consequences of Walking Like an Inverted Pendulum: Step-to-Step Transitions , 2005, Exercise and sport sciences reviews.

[13]  Fumiya Iida,et al.  Improving Efficiency for an Open-Loop-Controlled Locomotion With a Pulsed Actuation , 2016, IEEE/ASME Transactions on Mechatronics.

[14]  Arthur D Kuo,et al.  Energetics of actively powered locomotion using the simplest walking model. , 2002, Journal of biomechanical engineering.

[15]  Fumiya Iida,et al.  Simulation of forward hopping dynamics in robots and animals using a template with a circular foot and impulsive actuation , 2016, 2016 6th IEEE International Conference on Biomedical Robotics and Biomechatronics (BioRob).

[16]  Fumiya Iida,et al.  Self-stable one-legged hopping using a curved foot , 2014, 2014 IEEE International Conference on Robotics and Automation (ICRA).

[17]  Mario W. Gomes,et al.  Walking model with no energy cost. , 2011, Physical review. E, Statistical, nonlinear, and soft matter physics.

[18]  Y. Hurmuzlu,et al.  Bipedal locomotion stabilized by impact and switching: I. Two-and three-dimensional, three-element models , 1987 .