A unique systematic design methodology is developed
for achieving efficiency in solving some useful control problems
of real-time discrete-event systems. To achieve this,
an extended modelling formalism,
which allows the incorporation of data variables, is proposed
for describing real-time
discrete-event systems. Based on this formalism,
a new state-feedback control framework which can
exercise two types of control mechanisms: enabling/disabling and
forcing is established.
Two important control problems are handled in this thesis.
The first problem involves finding solutions which ensure that
predicate-based constraints are satisfied invariantly
in a closed-loop real-time discrete-event system.
To tackle this problem leads to the development of a
self-contained theory based on an innovative analysis of
event trajectories of a system and
a strategy for manipulating control mechanisms.
A novel decision algorithm,
employing a hybrid dynamic programming/constrained-search method,
offers a baseline for handling forcing and thereby plays a key role in
the derivation of sufficient conditions which
guarantee this control problem is solvable.
Furthermore, a procedure for controller synthesis
is obtained based on a crucial connection
between solvability conditions of
this problem in this theory and an adapted notion of control-invariance
in Ramadge-Wonham theory.
The second control problem is how to find solutions which ensure that
the first control problem is solvable and deadlock-freedom
is achievable. Sufficient conditions are presented for
the existence of solutions to this problem.
For both control problems, synthesis procedures in pseudocode are
provided.
As application examples, some control problems are examined:
a traffic-light in a subway system,
a transfer line in a manufacturing system, and two rods
in a nuclear power plant.
The feasibility of this systematic design approach is effectively
demonstrated by these examples
in terms of computational effort and explicit representations of
control policies.
As a whole, this thesis combines mathematical theory and quasi real-world
applications.