Reliable goal-directed reactive control of autonomous mobile robots

Abstract

This dissertation demonstrates that effective control of autonomous mobile robots in real-world environments can be achieved by combining reactive and deliberative components into an integrated architecture. The reactive component allows the robot to respond to contingencies in real time. Deliberation allows the robot to make effective predictions about the world. By using different computational mechanisms for the reactive and deliberative components, much existing deliberative technology can be effectively incorporated into a mobile robot control system. The dissertation describes the design and implementation of a reactive control system for an autonomous mobile robot which is explicitly designed to interface to a deliberative component A programming language called ALF A is developed to program this system. The design of a control architecture which incorporates this reactive system is also described. The architecture is heterogeneous and asynchronous, that is, it consists of components which are structured differently from one another, and which operate in parallel. This prevents slow deliberative computations from adversely affecting the response time of the overall system. The architecture produces behavior which is reliable and goal-directed, yet reactive to contingencies, in the face of noise, limited computational resources, and an unpredictable environment. The system described in this dissertation has been used to control three real robots and a simulated robot performing a variety of tasks in real-world and simulated real-world environments. A general design methodology based upon bottom-up hierarchical decomposition is demonstrated. The methodology is based on the principle of cognizant failure, that is, that low-level activities should be designed in a way as to detect failures and state transitions at high levels of abstraction. Furthermore, the results of deliberative computations should be used to guide the robot's actions, but not to control those actions directly.