Multi-PLC Control System Based on Wireless Bridge/Base Stations for Work-in-Process Movements in Corrugated Box Manufacturer

This paper presents a practical technique to design and implement a cooperative control of two groups with three conveyors and two rail guided vehicles (RGVs) by using two master and two slave programmable logic controllers (PLCs), respectively. The controlled conveyors and RGVs are utilized for work-in-process (WIP) movements between a corrugator and six printing machines in a manufacturer of corrugated paper boxes. The proposed technique is based on the use of wireless bridge/base stations modeled Ubiquiti Rocket M5 and Loco M5 for interconnections of two master PLCs modeled Omron CJ2M-CPU31, two slave PLCs modeled Omron CP1L-M40DT-D and connected with Omron CP1W-EIP61 module, and a host application over a control network to communicate with each other through EtherNet/IP technology. Input and output devices of each controlled subsystem are hardwired to each PLC. The transmission and reception schemes to enable real-time input/output data exchanges between the PLCs are specified with tag names for cyclic communications on data links. The proposed multi-PLC control system for WIP movements can operate in accordance with the manufacturer's requirements.