Abstract: In this paper, fault recovery for parallel interconnected
asynchronous sequential machines is studied. An adversarial input
can infiltrate into one of two submachines comprising parallel
composition of the considered asynchronous sequential machine,
causing an unauthorized state transition. The control objective is to
elucidate the condition for the existence of a corrective controller
that makes the closed-loop system immune against any occurrence
of adversarial inputs. In particular, an efficient existence condition
is presented that does not need the complete modeling of the
interconnected asynchronous sequential machine.
Abstract: Solvability of the model matching problem for
input/output switched asynchronous sequential machines is discussed
in this paper. The control objective is to determine the existence
condition and design algorithm for a corrective controller that can
match the stable-state behavior of the closed-loop system to that of
a reference model. Switching operations and correction procedures
are incorporated using output feedback so that the controlled
switched machine can show the desired input/output behavior. A
matrix expression is presented to address reachability of switched
asynchronous sequential machines with output equivalence with
respect to a model. The presented reachability condition for the
controller design is validated in a simple example.
Abstract: A strategy of fault diagnosis and tolerance for
asynchronous sequential machines is discussed in this paper. With
no synchronizing clock, it is difficult to diagnose an occurrence
of permanent or stuck-in faults in the operation of asynchronous
machines. In this paper, we present a fault detector comprised of
a timer and a set of static functions to determine the occurrence
of faults. In order to realize immediate fault tolerance, corrective
control theory is applied to designing a dynamic feedback controller.
Existence conditions for an appropriate controller and its construction
algorithm are presented in terms of reachability of the machine and
the feature of fault occurrences.