Integration of posture and rhythmic motion control using phase modulation based on leg loading/unloading

-- Towards a general controller of quadrupedal locomotion

Projects (detailed explanations at lower column)

• Integration of posture control and rhythmic motion control in low and medium speed dynamic walking using the phase modulation based on leg loading/unloading.

References

• Grillner, S. and Rossignol, M.: On the initiation of the swing phase locomotion in chronic spinal cats. Brain Res. vol.146, pp.269-277 1978.
• Duysens, J. and Pearson, K.G.: Inhibition of flexor burst generation by loading ankle extensor muscles in walking cats. Brain Res. vol.187, pp.321-32, 1980.
• Pearson, K.G.: Role of sensory feedback in the control of stance duration in walking cats. Brain Res. vol.57, no.1, pp.222-227, 2008.
• Ekeberg, O., Pearson, K.G.: Computer simulation of stepping in the hind legs of the cat: an examination of mechanisms regulating the stance-to-swing transition. Neurophysiol. vol.94, no.6, pp.4256-4268, 2005.

History and Abstract with movies and publications

• 2009-2010 (adaptive dynamic walking of Kotetsu)
  • In order to investigate the effectiveness of the proposed method and the validity of simulation results carried on in 2008, we made a new qadruped robot Kotetsu with three segments and four joints (hip roll, hip pitch, knee pitch and ankle pitch) in each leg.
  • In order to solve several problems in Kotetsu experiments against a lateral perturbation, we modified ACM used in simulations. That is, for adjustment of the forece threshold of fore legs, we added ACMinh and named ACM used in simulations as ACMexc. In addition, we changed ACM in simulations to increase the speed of swing motion of fore legs and named it as ACMw (w is \omega).
  • Especialy, stable dynamic walking against lateral perturbations was enabled without using touchdown angle control*1 based on rolling motion information.

  *1 Touchdown angle control (attacking angle control, stepping reflex) had been used in order to stabilize rolling motion and pitching motion of monopod robots (M.Raibert's monopods), biped robots (Biper-3&4, M.Raibert's bipeds and so on) and quadruped robots (Collie-2, Tekken, BigDog and so on).

  Results of experiments (ACMinh is employed in all experiments)

  • With a lateral perturbation at the stance phase onset of the left foreleg. (with ACMexc and ACMw) (WMV 4.3M, : explanation of the movie) (WMV 4M, : explanation of the movie)
  • With a lateral perturbation at the timing where only left foreleg was in the swing phase. (without ACMexc and ACMw) (WMV 3M, : explanation of the movie)
  • With a lateral perturbation at the stance phase onset of the left foreleg (without ACMexc and ACMw) (WMV 3M, : explanation of the movie)
  • Gait stability evaluation on flat floor (walk gait, cyclic period: 0.7s, walking speed: 0.18m/s, square root of Froude number: 0.12) (WMV 2.6M, QuickTIme 0.5M)

  Publications

  • C. Maufroy, H. Kimura and T. Nishikawa, Stable Dynamic Walking of a Quadruped Robot "Kotetsu" Using Phase Modulations Based on Leg Loading/Unloading against a Lateral Perturbation, Proc. of IEEE Robotics and Automation (ICRA2012), St. Paul, pp.1883-1888, 2012.5. (PDF) (PPT)
  • C. Maufroy and H. Kimura, Stable Dynamic Walking of a Quadruped Robot “Kotetsu” against Perturbations on Posture and Rhythmic Motion, Proc. of Int. Symp. on Adaptive Motion of Animals and Machines (AMAM2011), Awaji, (accepted), 2011.10. (Extended Abstract: PDF)
  • C. Maufroy, T. Nishikawa and H. Kimura, Stable dynamic walking of a quadruped robot "Kotetsu" using phase modulations based on leg loading/unloading, Proc. of IEEE Robotics and Automation (ICRA2010), Anchorage, pp.5225-5230, 2010.4. (PDF)

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• 2008 (adaptive dynamic walking in simulations)
  While integrating posture and rhythmic motion controls using phase modulations based on leg loading/unloading, we simulated adaptive 3D walking in low and medium speed under disturbances such as lateral perturbations and uneven terrain.
  The rhythmic motion of each leg in the sagittal plane is generated by a single leg controller (LC) which controls the swing-to-stance and stance-to-swing phase transitions using respectively leg loading and unloading. Since rolling motion induced by inverted pendulum motion during the two-legged stance phases results in the transfer of the load between the contralateral legs, leg loading/unloading involves posture information in the frontal plane. As a result of the phase modulations based on leg loading/unloading, rhythmic motion of each leg is achieved and leg coordination (resulting in a gait) emerges, even without explicit coordination amongst the leg controllers, allowing to realize dynamic walking in the low- to medium-speed range.
  We show that the proposed method has resistance ability against lateral perturbations to some extent, but that an additional ascending coordination mechanism (ACM) between ipsilateral legs is necessary to withstand perturbations decreasing the rolling motion amplitude.
  Consequently, we realized adaptive gaits using very weak coupling among LCs and no reflex.

  Results of simulations

  • 3D gait stability evaluation on uneven terrains (WMV 3M)
  • 3D gait stability evaluation with lateral perturbation at the beginning of the swing phase of the left hind leg (with ACM) (WMV 3M)
  • 3D gait stability evaluation with lateral perturbation at the beginning of the swing phase of the left hind leg (without ACM) (WMV 3M)
  • 3D gait stability evaluation with lateral perturbation at the beginning of the swing phase of the right fore leg (WMV 3M)
  • 3D gait generation with various walking speed (WMV 4M)
  • 3D gait generation with various walking cyclic periods (WMV 4M)

  Publications

  • C. Maufroy, H. Kimura and K. Takase, Integration of Posture and Rhythmic Motion Controls in Quadrupedal Dynamic Walking using Phase Modulations based on Leg Loading/Unloading,AUTONOMOUS ROBOTS, Vol.28, No.3, pp.331-3531, 2010.04. (PDF, Abstract on line)
  • C. Maufroy and H. Kimura, Stable Quadrupedal Dynamic Walking using Phase Modulations based on Leg Unloading, Proc. of Dynamic Walking 2009, Vancouver, (accepted), 2009.6 (Abstract)
  • C. Maufroy, H. Kimura and K. Takase, Stable Dynamic Walking of a Quadruped via Phase Modulations against Small Disturbances, Proc. of IEEE Robotics and Automation (ICRA2009), Kobe, pp.4201-4206, 2009.5. (PDF)

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• 2006-2007 (neuro-mechanical simulations)
  We carried out neuro-mechanics simulation of 2D hind legs stepping using a model of a cat. An independent LC (leg controller) consisted of three parts, those were, NPG (neural pattern generator), MOSS (motor output shaping stage) and PFCM (propulsive force control module). The swing to stance phase transition of a leg was determined by unloading of the leg. While using such phase transition, we successfully obtained alternative stepping of contralateral legs without the explicit coupling among LCs. This meant that we could generate stable 2D gaits using distributed and independent LCs.

  Results of simulations

  • 2D fore and hind legs stepping (WMV 3.5M)
  • 2D hind legs stepping while changing walking speed (WMV 19M)

  Publications

  • C. Maufroy, H. Kimura and K. Takase, Towards a general neural controller for 3D quadrupedal locomotion, Proc. of SICE Annual Conference (SICE2008), Tokyo, pp.2495-2500, 2008.08. (PDF)
  • C. Maufroy, H. Kimura and K. Takase, Towards a general neural controller for quadrupedal locomotion, NEURAL NETWORKS, Vol.21, No.4, pp.667-681, 2008.05. (PDF, Abstract on line)

Photo&Movie of "Patrush" & "Tekken"

Publications of quadruped studies