Abstract. This paper is concerned with adaptation capabilities of evolved neural controllers. A method consisting of encoding a set of local adaptation rules that synapses obey while the robot freely moves in the environment 6] is compared to a standard xed-weight network. In the experiments presented here, the performance of the robot is measured in environments that are di erent in signi cant w ays from those used during evolution. The results show that evolutionary adaptive controllers can adapt to environmental changes that involve new sensory characteristics (including transfers from simulation to reality) and new spatial relationships.
Evolution and AdaptationEvolutionary algorithms are widely used in autonomous robotics in order to solve a large variety of tasks in several kind of environments. However, evolved controllers become well adapted to environmental conditions used during evolution, but often do not perform well when conditions are changed. Under these circumstances, it is necessary to carry on the evolutionary process, but this might t a k e long time.Combination of evolution and learning has been shown to be a viable solution to this problem by providing richer adaptive dynamics 1] than in the case where parameters are entirely genetically-determined. A review of the work combining evolution and learning for sensory-motor controllers can be found in 5, 9].Instead of simply combining o -the-shelf evolutionary and learning algorithms, in previous work we presented an approach capable of generating adaptive neural controllers by evolving a set of simple adaptation rules 6]. The method consists of encoding on the genotype a set of modi cation rules that perform Hebbian synaptic changes 2{4] through the whole individual's life. The results showed that evolution of adaptive individuals generated viable controllers in much less generations and that these individuals displayed more performant behaviors than genetically-determined individuals.In this paper, we describe two new sets of experiments conceived to measure the adaptation capabilities of this approach i n environments that are di erent from those used during evolution. The results are compared to standard evolution of synaptic weights and to evolution of noisy synaptic weights (control condition).