Komputerowy symulator obiektu przeznaczony do testowania oprogramowania sterowników PLC

W artykule przedstawiono koncepcję programowego symulatora obiektu sterowania przeznaczonego do uruchamiania i testowania oprogramowania dla sterowników PLC. Symulator emuluje zachowanie fizycznego obiektu przemysłowego i komunikuje się ze sterownikiem za pośrednictwem karty wejścia-wyjścia podłączanej do komputera. Pozwala on na przetestowanie tworzonej aplikacji bez udziału fizycznego obiektu, dzięki czemu znacząco przyspiesza proces tworzenia, uruchamiania oraz testowania oprogramowania.

The paper discusses hardware and software tools used to support program testing and verification of Programmable Logic Controllers (PLC). Three main ideas of tools supporting PLC application development are presented: software PLC simulators (Fig. 1), software PLC simulators with software object simulators (Fig. 2), and software object simulators with a hardware PLC (Fig. 4). The last idea is discussed wider in the paper. The authors propose a new concept of the tool for supporting PLC program testing - an object simulator which is a separate device. The simulator consists of a PC equipped with an appropriate I/O card, and an object simulator program running on the PC. The object simulator program is responsible for emulating behavior of an industrial object, and providing appropriate visualization of its operation, enabling also the PLC programmer to simulate object faults. The PC does not communicate with the PLC using a network interface, but through physical I/Os of the PLC. The simulator is thus capable of testing the most of functionality built in PLC I/O modules, and time-critical functions, e. g. interrupts. The proposed concept of an object simulator can provide a reliable substitute for a physical object, and thus a significant part of software tests can be performed with use of the simulator. This can significantly facilitate and accelerate development of the application.