Design and implementation of EtherCAT-based distributed cotton bale inspection and management system

Abstract: As a real-time industrial Ethernet technology, EtherCAT (Ethernet for control automation technology) has a flexible network topology, which also can be configured easily and transmitted with high speed. Distributed systems can realize the separation between the data acquisition of remote site and the control of local human-machine interface by using the modern network communication technology. It can interconnect the control center of test line and a number of auxiliary equipments via communication network to achieve the purpose of resource sharing and working together. It is also easy to realize decentralized centralized monitoring, control, fault diagnosis and distributed data management. In order to improve the efficiency, reliability and maintenance simplicity of the inspection process for cotton bales import and export, the distributed cotton bale inspection and management system based on EtherCAT was developed in this study, which realized a automatic process of the continuous works as weighing, sampling and marking in the cotton import, export and storage of national cotton. In the control scheme of single inspection line, the PLC + inverter + intelligent motor method is utilized to make system control logic simple and clear, which controls 11 inverters and 300 common IOs at the same time, and met the requirements of efficient sampling (the overall efficiency is 40 bales/min with the sampling rate of 10%). On the organization and management of off-site and multiple lines, we proposes a distributed communication scheme suitable for regulating and scheduling based on EtherCAT, which achieves transparent management and seamless connection with control layer, device layer and management layer. In the EtherCAT-based distributed applications, the control object includes the Ethernet devices of factory enterprises, factories, process, and field level. Specific devices contain the EtherCAT local rack, EtherCAT remote I/O sub-station, the EtherCAT distributed I/O device, ConneXium extended and managed switch, which can be pre-configured for using as a dual-loop switch. Hot standby configuration can be used with configuring the remote I/O, distributed I/O device or the third-party devices of distributed I/O devices. Through the daisy chain loop architecture of communication module, the entire system can achieve the performance of automatic network recovery and uncertainty remote I/O less than 50 ms. It has connected single control equipment to the whole EDCB-IMS (EtherCAT-based distributed cotton bale inspection and management system) for having the transparent access and control of businesses, factories, process and field equipments. The EDCB-IMS system has a design of the pipeline running mode, which makes the cotton mechanical devices automatically sample, analyze the sampling cotton bale, weigh and print barcode. According the operating frequency of each module, the system will arrange the work time of each step, such as separating the sampling bales with the other bales, analyzing the sample, passing through the RFID (radio frequency identification) system, weighing, and data management of sampling data. The experimental results show that it has greatly enhanced cotton bales inspecting efficiency from 5 bags/min to 40 bags/min. The data transmission speeds are 7.5Mbps (Modbus on EtherCAT) and 15 Mbps (CIP on EtherCAT) respectively and with low data loss. It provides a good real-time performance and is easy to do extensions, which can be a good reference for the automation research on application and technology of distributed quality-test system.