Research On The Key Technologies Of Remote Monitoring For PLC

With the rapid development of economic, the scale of industrial production becomes larger and larger. The environment of industrial zone is poor. PLC is used in industrial zone as the core of industrial production. Realizing the remote monitoring of PLC is very important for health protection. In this thesis, a PLC remote monitoring system is designed, whose core are microcontroller and GPRS module. A communication structure is designed, which makes every expansion module do not interfere each other. This design makes the communication between PLC and expansion module operates smoothly. Based on that, the system's key technologies are researched in this thesis.In this thesis, a control strategy is designed for the stability of communication between monitoring centre and the GPRS module. This paper designed control strategy for SMS control. Using these control strategies, the system can filter the spam messages. The ability of resisting the impact of a large number of messages is enhanced. If the signal is poor, TCP connection is prone to disruption. This paper designs the corresponding control strategy, too. This paper also considered the cases of the combination of the two kinds of communication. The experimental results illustrated that each control strategy is suitable for the corresponding situation.The structure of KMP algorithm is improved based on the analysis of its characteristics. The improved algorithm is applied in the serial communication between microcontroller and GPRS module. In this method, the similarity between pattern and corresponding substrings is estimated and determine whether to response the command according the similarity. The experimental results illustrated that the proposed method could largely enhance the anti-jamming ability of the serial communication between microcontroller and GPRS module.New methods for the key expansion algorithm of AES encryption algorithm are proposed according to the one-way property based on the analysis of the shortcomings of the original key expansion method, which improved the original method in two aspects- encryption strength and running speed. Analysis and experimental data illustrated that the proposed methods not only guaranteed the security of the original algorithm but also improved its efficiency.At last, after the summary of achievements, the problems which have not been resolved are pointed out, making a prospect for this system.