PassiveWalkerExperiment

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• Body Evolution and Morphological Computing

Body Evolution and Morphological Computing

The term “Morphological Computing” refers to the fact that the computations/elaborations that allow a situated robot to display a certain desired behaviour should not be performed necessarily by the robot’s control system only, but can be performed also by the robot’s body. One paradigmatic demonstration of this is constituted by passive walking machines, i.e. robots that can display a bipedal walking behaviour on an inclined plane without any actuator and any control system. Whether these machines manage to display an appropriate walking behaviour or not depends on the physical characteristics of their body (e.g. the length and the mass of each body segment).

The term “Body Evolution” or “Body/Brain Evolution” refers instead to evolutionary robotics experiments in which not only the characteristics of the robots’ controllers but also the characteristics of the robots’ body are evolved.

The PassiveWalkerExperiment plugin provides a way to study the power of morphological computation through an evolutionary approach that is used to discover the characteristics of the robots’ body that, in interaction with the environment, enable the robot to display the desired walking behaviour.

In this experiment a biped robot constituted of only passive elements (rigid body segments, joints and springs) can evolve an ability to walk on an inclined plane. For simplicity, the plugin implements a simplified biped with a body that does not extend over the lateral axis (the two legs are allowed to physically compenetrate) and consequently does not need to balance over that axis. The physical characteristics of the robot body are encoded in the robots’ genotype and evolved. Evolving individuals are evaluated on the basis of the distance walked during a fixed amount of time. The implementation of the body structure is included in the plugin code and constitutes a useful exemplification of how robots made of articulated body parts can be implemented in FARSA.