Examples
of evolved center-crossing recurrent synaptic delay based NN controllers
The biped is controlled by a
recurrent synaptic delay based NN [2][6]. The bias of
each node is defined according to the center-crossing condition [1][3]. Thus, all the nodes will be near the maximum
sensitivity regions to induce activation changes.
The evolutionary robotics
methodology [4][5] was used to obtain the neural
controllers. A standard genetic algorithm was employed, using a mutation
operator and a rank-based method as selection operator. Each synaptic delay
based NN is codified by a vector that includes the connection weights, the
temporal delays and the biases of the output neurons.
Example
of locomotion behaviors on a flat surface and obtained by means of the GA,
showing the effect of selecting different intervals for the time constants of
the output nodes. In all the videos the original speed was divided by 4.
Example 1: Locomotion behavior using time constants in the
output nodes between 0.5 and 2.5, whereas the time delays of the NN connections
are in the range [0,25]:
Example 2: Locomotion
behavior using time constants in the output nodes between 2.5 and 5.0, whereas
the time delays of the NN connections are in the range [0,50]:
Example 3: Locomotion
behavior obtained with the robot on a slope. Time constants in the output nodes
are in the range [0.5,5], time delays of the NN
connections are in the range [0,50]:
[1] Beer, R. (1995), "On the Dynamics of Small
Continuous Time Recurrent Neural Networks", Adaptive Behaviour 3(4): 469-509.
[2] Duro, R.J. and
Santos, J. (1999), “Discrete time backpropagation for training synaptic delay
based artificial neural networks”, IEEE
Transactions on Neural Networks 10(4): 779-789.
[3] Mathayomchan, B., and Beer, R. (2002), "Center-Crossing Recurrent
Neural Networks for the Evolution of Rhythmic Behavior", Neural Computation 14: 2043-2051.
[4] Floreano , D. and Mattiussi, C.
(2008), Bio-Inspired Artificial
Intelligence, MIT Press.
[5] Nolfi, S. and Floreano, D.
(2000), Evolutionary Robotics, MIT
Press.
[6] Santos, J. and Duro, R.J.
(2001), “Influence of noise on discrete time backpropagation trained networks”,
NeuroComputing
41(1-4): 67-89.
More information in:
Santos, J. (2014), “Evolutionary
algorithms to automatically obtain central pattern generators for biped and
hexapod robotic structures”, Workshop on
Nature-Inspired Techniques for Robotics, Parallel Problem Solving form Nature -
PPSN 2014.
Santos, J. (2013), “Evolved
center-crossing recurrent synaptic delay based neural networks for biped locomotion
control”, Proceedings IEEE Congress on
Evolutionary Computation - IEEE-CEC 2013, 142-148.
Santos, J. and A. Campo, A. (2012), “Biped locomotion control with
evolved adaptive center-crossing continuous time recurrent neural networks”, Neurocomputing 86(1):86-96.