[robotics-worldwide] Post-Doc announcement

Benoit Girard benoit.girard at college-de-france.fr
Thu Nov 20 06:33:52 PST 2008

Dear colleague,
I would like to transmit to following post-doc position announcement to 
the robotics worldwide mailing list :

*Head stabilization and top-down control of humanoid robots*

Keywords : Humanoid robotics, neuroscience, movement control, stabilized 
vision, vestibulo-ocular reflex, locomotion.

A post-doc position is available on bio-inspired walking control of 
humanoid robots. The position will be hosted at the Laboratory of 
Physiology of Perception and Action (LPPA, College de France, Paris) and 
will be conducted in close collaboration with the Laboratory for 
Analysis and Architecture of Systems (LAAS, Toulouse France) and the 
Aldebaran Robotics company (Paris). The position could begin in January 
2009. The 1 year contract could be renewed twice for a total of three 
years. It is part of the humanoid robot ROMEO project, gathering several 
French robotics laboratories and companies.

Humanoid robots are complex mechanical systems that include several 
kinematic chains in tree structure and contain a high number of degrees 
of freedom. To localize and control such systems, it is necessary to 
measure the angular value of each joint and determine the position and 
orientation of at least one reference frame, attached to the robot, with 
respect to the environment. To this end, roboticists usually consider a 
reference frame located in the chest, as it constitutes the central node 
of simple independent kinematic chains (i.e. the members and the head) 
and is close to the center of gravity of the robot. Considering this 
spatial reference, control strategies based on generalized inverse 
pendulum models have been proposed to control the center of gravity 
within an horizontal plane in order to make the Zero Moment Point (ZMP) 
follow a prescribed trajectory defined by successive planned steps.

As efficient as it could be, this control strategy turns out to be in 
contradiction with available knowledge about human locomotion. Indeed, 
during walking, the center of gravity strongly oscillates while the head 
appears to be stabilized. Experimental studies tend to show that this 
stabilization concerns the head orientation with respect to the gravity 
(Pozzo et al, 1990) as well as the gaze stabilization using the 
vestibulo-ocular reflex. It appears then that the central nervous system 
rather plans a stable head trajectory, while the rest of the body 
implements this plan according to the local constraints (Hicheur et al., 
2005, 2007). Furthermore, because of the conjunction of visual, auditory 
and vestibular sensory systems, the head constitutes an excellent 
multi-sensory spatial reference and, as a consequence, an ideal base for 
controlling the whole body motion. In addition, contrary to a reference 
located in the chest, which would require coordinates transformation, 
the spatial information is directly delivered at the head level by the 
sensors, providing better precision and control robustness.

Following this reasoning, the objective of this post-doctoral work is to 
develop an innovative bio-inspired “top-down” control architecture that 
guarantees the stabilization of the head and uses this reference for 
controlling the locomotion of the whole body. A NAO humanoid robot 
developed by Aldebaran robotics, with a modified head including an 
actuated visual system and inertial sensors, will be available from the 
beginning of the project.

The candidate must have a strong background in robotics and a real 
interest for investigating bio-inspired approaches.

* Pozzo, T., Berthoz, A. and Lefort, L. (1990). Head stabilization during various locomotor tasks in humans. Experimental Brain Research 82(1):97-106.

* Hicheur, H., Pham, Q.-C., Arechavaleta, G., Laumond, J.-L. And 
Berthoz, A. (2007). The formation of trajectories during goal-oriented 
locomotion in humans. I. A stereotyped behaviour. European Journal of 
Neuroscience 26(8):2376-2390.

* Hicheur, H., Vieilledent, S. and Berthoz, A. (2005). Head motion in 
humans alternating between straight and curved walking path: Combination 
of stabilizing and anticipatory orienting mechanisms. Neuroscience 
Letters 383:87–92.

Contacts :


      B. Girard _benoit.girard at college-de-france.fr
      <mailto:benoit.girard at college-de-france.fr>_


      A. Berthoz _alain.berthoz at college-de-france.fr
      <mailto:alain.berthoz at college-de-france.fr>_


      Ph. Souères _soueres at laas.fr <mailto:soueres at laas.fr>_

Benoît Girard, LPPA - CNRS / Collège de France
11 place Marcelin Berthelot
75231 Paris Cedex 05

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