The Design Of Fuzzy Surveillance System For Dissolved Oxygen (DO) Of SBR Based On FPGA

With the development of related technologies in wastewater treatment, higher requirements of the automation level especially real-time were proposed in controlling some important parameters during the treatment process. In this paper, the fuzzy control theory was introduced according to the control requirements of the dissolved oxygen concentration in SBR (Sequencing Batch Reactor) sewage treatment process, then the design and implementation of fuzzy surveillance system for dissolved oxygen of SBR was discussed in the hardware description language VHDL, combing the FPG A and EDA technologies.Firstly, the requirements of dissolved oxygen concentration in the SBR wastewater treatment process ware analyzed, in base of which the dissolved oxygen surveillance system was established in combination with the fuzzy control theory. After that, characteristics of the A/D data acquisition section, the fuzzy controller section, the D/A convert section and the frequency aeration actuator section were analyzed in accordance with the basic structure of the system. Also selection of chips and devices used in each section were carried out to achieve the control function of the system.Secondly, the design and implementation of fuzzy controller for dissolved oxygen on FPGA, hard-core of the system, were analyzed emphatically. Then every section of the system was described and designed in VHDL language according to modular design flow. The main portions are as follows:the control of dissolved concentration acquisition was realized by the way of semi-integer frequency divider and finite state machine; with the fuzzy control list of dissolved oxygen calculated off-line by the fuzzy logic toolbox of MATLAB, combining with relevant macro function module on QuartusII, the fuzzy controller of dissolved oxygen was designed and realized with the method of look-up table; the control of D/A convert process for output of fuzzy controller was designed; furthermore, some auxiliary circuits such as display module and keyboard module were designed for the system.Finally, VHDL description of every function module in the system was simulated and verified on the development and design platform QuartusⅡ. The results showed that the data acquisition of dissolved oxygen, fuzzy processing and control output of the system could be realized by the corresponding VHDL description and design of each module, all of which could achieve regulation of the dissolved oxygen concentration parameter during the wastewater treatment process consequently.