Generalized Fuzzy Inference Method And Its Application To Aerobic Treatment Of Papermaking Wastewater

With the rapid development of China’s paper industry,the problem of papermaking wastewater pollution is becoming increasingly prominent.The latest discharge standard of water pollutants for pulp and paper industry(GB3544-2008)issued by the Ministry of Environmental Protection of the People’s Republic of China puts forward more stringent requirements for the discharge indicators of papermaking wastewater.Based on the traditional anaerobic and aerobic secondary biochemical treatment process,it is difficult to meet the above requirements using traditional PID control methods.The aerobic treatment process of papermaking wastewater is quite complex.It features non-linear,time-varying,time-delay,and modeling difficulties.The existing intelligent control methods still have some problems including low control accuracy and high energy consumption during system operation.Therefore,a hot research topic in the current aerobic treatment process control of papermaking wastewater is to embed advanced intelligent control methods and technologies into aerobic treatment process control system.It will improve its control accuracy and effluent quality,lower energy consumption,and reduce wastewater discharge in order to ensure the safety and efficiency of the wastewater treatment process.Based on the biochemical treatment process of papermaking wastewater from the Paper Mill in Xianyang City,Shaanxi Province,this thesis focuses on the control of dissolved oxygen concentration in the aeration process of the activated sludge system.With the real-time data of aerobic treatment process,new generalized fuzzy control systems are proposed based on fuzzy control system and generalized fuzzy set theory by combining theoretical research and experiment.It is of great importance to improve the stability,accuracy,rapidity and robustness of the control system for aerobic treatment process of papermaking wastewater.Besides,it also lays a solid theoretical foundation for the development of new control strategies.Major work and contributions of this thesis can be summarized in the following three aspects:Ⅰ.The establishment and simulation of neutrosophic inference system.Based on the first type inclusion relation of the single-valued neutrosophic set,the related lattice structure of single-valued neutrosophic sets is studied,and it is proved that single-valued neutrosophic sets constitute De Morgan algebras with respect to its basic operations.On this basis,the relevant definitions and basic properties of the neutrosophic norm,the neutrosophic conorm,the neutrosophic negation,the neutrosophic implication operator and the neutrosophic residual implication are given,and the structure and properties of De Morgan neutrosophic triples are deeply analyzed.The residual lattice based on the neutrosophic norm and its residual implication is systematically studied from the perspective of algebraic operations,which provides new research ideas and methods for dealing with the structure of the neutrosophic logic operator.Then,on the basis of neutrosophic relation and neutrosophic implication operators,the NCRI method and the triple I algorithm of neutrosophic inference are proposed.By combining the MATLAB code of the membership function and basic operation of single-valued neutrosophic set,a study on the MATLAB program for neutrosophic inference system and neutrosophic controller are studied and developed,which offers a new theoretical basis and implementation strategy for further building neutrosophic control system.Ⅱ.The proposition of the basic theory of three-way fuzzy sets and the establishment and simulation of three-way fuzzy inference system.In view of the limitations of the existing generalized fuzzy sets in solving uncertainty problems,this thesis proposes the concept of three-way fuzzy sets based on the basic ideas of three-way decision,rough sets and various generalized fuzzy sets(including lattice valued fuzzy sets,intuitionistic fuzzy sets,partial fuzzy sets,and neutrosophic sets,etc.),and discusses the relationships between several special three-way fuzzy sets(including ordinary three-way fuzzy set,dependent three-way fuzzy set,three-way set,etc.)and various generalized fuzzy sets,three partition.The basic operations of three-way fuzzy sets are systematically studied,and their properties and related lattice structures are analyzed.Then,the concept of three-way fuzzy relation is introduced,the relation between it and the concept of joint coefficient in set pair analysis is discussed,and the composition operation of three-way fuzzy relation is given.The definitions and properties of three-way fuzzy implication operators and three-way residual implications generated from three-way t-norms are studied.On this basis,the TCRI method and the triple algorithm of three-way fuzzy inference are proposed.Combined with specific examples,the specific steps of these two inference methods and their MATLAB implementation program are provided.Finally,aiming at the control of the liquid medicine preparation water level in aerobic treatment process of papermaking wastewater,three-way fuzzy inference methods based on different three-way fuzzy implication operators are applied to construct three-way fuzzy controllers.By comparing and analyzing the graphical features of the three-dimensional surface graph,the inference effects of different three-way fuzzy inference methods are demonstrated.Then,the three-way fuzzy inference method with best effect is to be applied in the control system of the liquid medicine preparation water level.Through simulation experiments,the tracking ability and anti-interference capability of the step response curve are analyzed,which proves the feasibility and effectiveness of the three-way fuzzy inference method.Ⅲ.Generalized fuzzy control of dissolved oxygen concentration in aerobic treatment system of papermaking wastewater.Aiming at the problem of the uncertainty in aerobic treatment process of papermaking wastewater,the characteristics of dissolved oxygen concentration control(non-linear,time-varying,time-delay,and modeling difficulties),as well as the limitations of process control technology itself,resulting in low accuracy of dissolved oxygen concentration control,based on the research of activated sludge system model,the internal relationship between dissolved oxygen concentration and gas supply volume is deeply analyzed and the dynamic equation of dissolved oxygen concentration is established.By using Euler discrete method,the time domain model of control system is obtained.Furthermore,fuzzy control,neutrosophic control and three-way fuzzy control for dissolved oxygen concentration are proposed based on the Mamdani type fuzzy implication operators,neutrosophic implication operators and three-way fuzzy implication operators,respectively.With the help of MATLAB,simulation programs for the generalized fuzzy control system are proposed,achieving intelligent control of complex closed-loop control systems.Through simulation experiments,it is proved that these two generalized fuzzy control systems have good dynamic performance and anti-interference ability,thus proving the effectiveness and feasibility of the generalized fuzzy inference method for dissolved oxygen concentration control in aerobic treatment system of papermaking wastewater.Successfully solved the problems of low accuracy and poor control effect in dissolved oxygen concentration control,thereby realizing the application value of the generalized fuzzy control theory.In summary,based on the research of fuzzy control theory and its application to the field of industrial process control,this thesis proposes neutrosophic inference methods and three-way fuzzy inference methods.On this basis,generalized fuzzy control systems for dissolved oxygen concentration in aerobic treatment system of papermaking wastewater are constructed,which not only improves the control accuracy and aerobic efficiency,but also has great significance in energy conservation and emission reduction.Its application to control system of aerobic treatment process of papermaking wastewater is of great reference value for the in-depth research and application of intelligent control technology in the field of industrial wastewater treatment process.