Simulation framework for the verification of PLC programs in automobile industries

The objective of this study is to propose a framework of virtual plant models for the verification of PLC logic through modeling and simulation. The proposed virtual plant model consists of three types of object: the virtual device model (object model), the intermediary transfer model (functional model), and the PLC program & HMI (dynamic model). A virtual device model consists of a physical part, which is used to represent the properties of a real device and a logical part, which is used to manage the device's operation. For the fidelity of the virtual plant model, an intermediary transfer model controls the virtual device through a PLC program and sends information on the virtual device's state to the supervisory control model. Moreover, the PLC program and HMI are used for constructing communication environments similar to a real manufacturing line. For the implementation of the proposed virtual plant model, this study employs an I/O model based on the formalism of Automata and Discrete Event Systems Specifications (DEVS). As a result of the application to a car assembly line, 18 error codes are detected through the manual mode and have been revised. Finally, we can confirm there is no sequential error in the PLC program by checking the time chart. Moreover, the bottleneck and ramp-up/down times are reduced when a manufacturing system/line is built.