Department of Applied Mechanics, Adaptive Systems
research group
Evolution of
central pattern generators
Krister Wolff, Jimmy Pettersson,
Almir Heralic, Mattias Wahde.
Project carried out: Aug. 2005 to Jan. 2006.
Introduction
and aim Many biological organisms
are equipped with central pattern generators (CPGs), i.e. neural circuits
capable of producing oscillatory output given tonic input. CPGs have been
studied in animals such as cats, and there are also observations that support
the notion of CPGs in humans. The development of
artificial counterparts to biological CPGs, with the aim of generating robust
gaits for bipedal robots, is addressed in this research project. The approach
has been investigated through full rigid-body dynamics simulations in 3D of a
bipedal robot with 14 DOF. Rendered image of the
bipedal robot. (Scroll down to see movies
of the robot walking.) Method The half-center CPG model
was adopted as an oscillator unit, with interconnection paths between oscillators
undergoing structural modifications using a genetic algorithm (GA). In
addition, the connection weights in a feedback network of predifined
structure were evolved. Furthermore, a (massless) supporting structure was
added to the robot, in order to guide evolution towards natural, humanlike
gaits. Subsequently, this structure was removed, and the ability of the best
evolved controller to generate a bipedal gait without the help without the
help of the supporting structure has been verified. Picture of the structure
of the CPG network used in the simulations. Note that an arrow indicates the possibility
of full connection (left). The robot depicted with a single hip joint CPG
with feedback paths, and a possible choice of connection types (right). Simulations The simulations were
carried out using the EvoDyn simulation library, developed at Chalmers
University of Technology. The successful approach involved two phases: First
generating a stable gait in 2D with help of the supporting structure. Then,
the 2D gait was generalized to 3D, without the supporting structure. Movies of the robot
walking in 3D: Publications
related to this project Wolff, K., Pettersson, J.,
Heralic, A., and Wahde, M. Structural evolution of
central pattern generators for bipedal walking in 3D simulation. In Proceedings of the 2006 IEEE International Conference on Systems,
Man, and Cybernetics (SMC), pp. 227–234, Heralic, A., Wolff, K.,
and Wahde, M. Contact
information: Department of Applied
Mechanics 412 96 Göteborg, Sweden Tel: +46 31 772 3625 Fax: +46 31 772 3690 e-mail:
krister.wolff@chalmers.se |