Research Of Service-oriented Open Interconnection Technology For OPC UA Based Wireless Field Devices

Driven by advanced information and communication technologies, manufacturing is on the fourth industrial revolution(Industrie 4.0), which requires more extensive information sharing in the factory. As a data exchange specification for industrial communication, OPC Unified Architecture(OPC UA) solves the access uniformity problem and standardization problem of data communication between the factory floor and enterprise level, and meets the need of enterprise information in a high degree of connectivity. This thesis attends to extend the OPC UA protocol to the low layer of the industrial wireless system, and achieves the seamless integration between the low-level Internet of Things(IOT) and the Internet, as well as the filed devices and the background management system. However, due to the relative limitation of equipment resources and communication resources in the underlying IOT, an original OPC UA protocol cannot be applied to the underlying IOT directly. Therefore, this thesis investigates the applicatio n of OPC UA in wireless filed devices and the implementation of service-oriented open interconnection of wireless filed devices. The main work includes:1. Study the key technologies of service-oriented open interconnection for wireless field devices, including the OPC UA protocol and the 6LoWPAN technology, which can support the service orientation and open interconnection of wireless field devices, respectively.2. For the resource-constrained characteristic of wireless field devices, as well as the low power dissipation characteristic of IEEE 802.15.4, the OPC UA server is cut out and corresponding datagrams are optimized. Consequently, without changing the core function of OPC UA, a Nano OPC UA server suitable for wireless field devices and a compression mechanism supporting the compression and decompression of OPC UA network transmission load are designed and realized.3. Considering the sensitivity of the wireless field devices for power consumption, and the OPC UA protocol can not support the sleep proxy function of devices, a sleep proxy mechanism is designed. The designed sleep proxy mechanism can meet the sleep needs of wireless filed devices, thus prolonging the network lifetime and solving the problem of data obtainment for the sleeping devices.4. Take the Contiki IOT operation system platform and the IOT devices developed in laboratory for special examples, the designed mechanisms including Nano OPC UA server, compression mechanism and sleep proxy mechanism are implemented. Meanwhile, a test system is also established.Test results show that the Nano OPC UA server designed in this thesis realizes the core function of OPC UA and meets the needs of practical applications. The designed compression layer can effectively compress and extract the OPC UA network transmission payload, which improves the efficiency of network transmission. In addition, the designed sleep proxy mechanism can meet the needs of devices for sleeping. Hence, the study of this work has a certain reference value for the extension of the UA OPC protocol to the low layer of IOT and the implementation of the service-oriented open interconnection of filed devices.