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.
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