An architecture for autonomy

An autonomous robot offers a challenging and ideal field for the study of intelligent architectures. Autonomy within a rational behavior could be evaluated by the robot's effectiveness and robustness in carrying out tasks in different and ill-known environments. It raises major requirements on the control architecture. Furthermore, a robot as a programmable machine brings up other architectural needs, such as the ease and quality of its specification and programming. This article describes an integrated architecture that allows a mobile robot to plan its tasks-taking into account temporal and domain constraints, to perform corresponding actions and to control their execution in real-time-while being reactive to possible events. The general architecture is composed of three levels: a decision level, an execution level, and a functional level. The latter is composed of modules that embed the functions achieving sensor-data processing and effector control. The decision level is goal and event driven, and it may have several layers, according to the application; their basic structure is a planner/supervisor pair that enables the architecture to integrate deliberation and reaction. The proposed architecture relies naturally on several representations, programming paradigms, and processing approaches, which meet the precise requirements that are specified for each level. The authors have developed proper tools To meet these specifications and implement each level of the architecture: a temporal planner IxTeT; a procedural system for task refinement and supervision, PRS; Kheops for the reactive control of the functional level, and G(en)oM for the specification and integration of modules at that level. Validation of the temporal and logical properties of the reactive parts of the system, through these tools, are presented. Instances of the proposed architecture have been integrated into several indoor and outdoor robots. Examples from real-world experimentations are provided and analyzed.