Study Of Distributed Intelligent System Based On Multi-Agent Architecture For Wastewater Treatment

Wastewater treatment process is a complicated industry process which is difficult to control,because it has the characters of multi-variables,non-linear,time-varying,randomicity and complexity. Therefore, it is difficult to implement steady running of the system and the effluent according with the standard by the traditional control theories and technologies. Currently, the application research of the artificial intelligence technique combined with other application fields in engineering systems has became the hotspot, and obtained greater achievement. However, it is still on the stage of groping research at home in the AI applications of wastewater treatment. The urgent problem are not only how to apply artificial intelligence technique realizing steady and dependable running of the process of wastewater treatment, also how to ensure the effluent according with the standard and energy-saving. This dissertation, analyzed the status quo of the AI application in wastewater treatment fields aboard and home, studied the multi-agent theory of distributed artificial intelligence, fuzzy set theory, expert system theory, and artificial neural network theory, put forwards a new idea of a distributed intelligent system of wastewater treatment based on multi-agent theory in order to realize the intelligent control of wastewater treatment process, on-line measure of the technologic parameters which is difficult to measure and real-time diagnosis of the exceptional phenomena, developed the prototype system based on the opening JADE developing platform according to the FIPA standard by Fuzzy JESS, Hibernate and Spring framework techniques etc, and offered feasible route for the application of the Multi-Agent theory.Main results of the research as following:①Through the analysis of agent, MAS theory and the characters of wastewater treatment process,brought forward the hierarchical structure and the system architecture of the intelligent distributed wastewater treatment system based on multi-agent theory, defined the inner logic frame and function of each agent of the system model. The research results indicate that the hierarchy of the agents of the intelligent system is clear, modularized, the agents is independent as well as contacted with each other organically, and the robustness and the expansibility of the system are excellent.②In order to actualize the multi-agent system, guarantee the opening trait of the system, interoperate among the agents each other, through the research on the FIPA standard, JADE Agent developing platform, Fuzzy JESS expert system developing tool and Hibernate, Spring Framework database technology, utilized the automations system platform of the wastewater treatment, the intelligent system has been implemented.③Through the analysis of the exceptional phenomena of the wastewater treatment for the activated sludge process, established the fault tree of the aeration tank and the fault tree of the secondary clarifier for the wastewater treatment system of the activated sludge process, adopted the forward inference mechanism, used Fuzzy JESS expert system developing tool, realized the agent of the fault diagnosis of the exceptional phenomena of the wastewater treatment for the activated sludge process. The agent of the fault diagnosis has the characteristics of knowledge base, inference machine, and the main program separated mutually, therefore, it is good to update knowledge fountain, and guarantee the trait of clarity, flexibility, migration of the system. Platform- independent and multithreading mechanism allows the Fuzzy JESS to execute concurrently applications.④Some key variants(such as SVI)can't be obtained directly by online measure or as the longer delay times of getting measure results, the control of the variants is difficult. After studying the principle of soft-measure techniques, gives a new model method of the parameters soft-measure of wastewater treatment based on artificial neural networks. To enhance the real-time and validity of the artificial neural network, using rough set theory to preprocess the model, after reducing the attributes and redundant data, set up the soft-measure model of the parameters difficultly to measure of wastewater treatment based on rough set theory and artificial neural network. Then using the real parameters from a wastewater treatment plant, made the simulation experiment. The result shows, as the model without preprocess by rough set, the error of the measure values is not only less, but the data dimensions, and the training time and the training steps of the artificial neural network are reduced. So, this is favorable to the practicability the soft-measure model.⑤In order to realize the process control of the wastewater treatment system, the intelligent system has set three executable agents include the agent of DO control, the agent of sludge circumfluence, and the agent of excess sludge discharge. DO control agent used Fuzzy control method which was fit to the characters of the big inertia, big lag and indetermination of DO control. The agent of sludge circumfluence measures real-timely the MLSS of the aeration tank,according to the difference between the value of MLSS by real-time measure and the given value, adopted PID arithmetic to control the running speed of the pump for the sludge circumfluence. By calculating the value of the daily excess sludge discharge, the agent of excess sludge discharge control makes use of the liquidometer to control running of the pump.⑥The interaction among the agents is an important character of MAS, so the conflict of agents is unavoidable. By the process of coordination and troubleshooting, agents fulfilled a problem solution. Through the analysis of the possible confliction and the distinguish methods among the agents in the wastewater treatment of activated sludge process, and according to the theory of conflict negotiation and task cooperation, brought forward the troubleshooting strategy for the intelligent system, and realized the troubleshooting agent.⑦The functions of the agent of data service are to provide uniform and flexible interfaces for other Agents to access real-time database. The reading and writing operation of the agents in the MAS to the real-time database are realized by using the correlative service provided by the agent of data service. The dissertation adopted Hibernate and Spring Framework database access technology, made the real-time database in the system is transparent for the agents, at the same time, the system is of outstanding migration, and long lifecycle.⑧Owing to MAS is a lax coupling system, which is composed of many agents, communication is the foundation of realizing interaction and social organization, so the communications among agents is one of the important problems of MAS research. Through the analysis of the agent communications pattern, adopted FIPA-ACL as the communication language in this intelligent system, also ascertained the mode, strategy, protocol, and content of the communication, implemented the communications among the agents of this intelligent system.The distributed intelligent system of wastewater treatment based on multi-agent theory could improve the decision-making level of the whole control system, thereby realizes intelligent running, control and monitor in the wastewater treatment process, enhances the water quality and implements energy saving. The software and hardware platform of Modern wastewater water control system, efficient java language environment, and JADE, FuzzyJESS, Hibernate, Spring Framework etc technology make the realization of the intelligent system is feasible.