Hierarchical Interface-based Supervisory Control
Part II: Parallel Case
R.J. Leduc
M. Lawford
W.M. Wonham
Abstract
In this paper we present a hierarchical method that decomposes a
discrete-event system (DES) into a high level subsystem which
communicates with n >= 1 parallel low level subsystems through
separate interfaces, which restrict the interaction of the
subsystems. We first review the setting for the serial case
(n =1), and then generalize it for n >= 1. We define an interface and
a set of interface consistency properties that can be used to verify
if a DES is nonblocking and controllable. Each clause of the
definition can be verified using a single subsystem; thus the complete
system model never needs to be stored in memory, offering potentially
significant savings in computational resources. We provide algorithms
for verifying these new properties, and briefly discuss the
computational complexity of the method. Finally we present an
application to a large manufacturing example with an estimated
closed-loop state space size of 7 X 10^21.