A fault diagnosis system-PLC design for system reliability improvement

摘要

In this paper, a fault diagnosis system-programmable logic controller (FDS-PLC) is developed and discussed, regarding the improvement of reliability of PLC systems. Traditional approaches to improve reliability of the fault diagnose functions of PLC are not conscious of the fact: system developers and programmers are not able to identify every fault that may occur during the system's lifetime. In order to conquer this problem, a FDS-PLC design that establishes and perfects a specification model of the PLC system is introduced. Firstly, FDS-PLC collects and transmits diagnosis data in surplus kernel time of the embedded processor; therefore, it does not decrease the responding speed of the system. Secondly, a finite state machine (FSM) built on PC is applied to construct the specification model and report faulty states to the system operator. Finally, the system is endowed with learning ability by perfecting the specification model. The application of FDS-PLC is further illustrated by an example on an elevator control system experimental platform.