Data Acquisition And Control System Based On FPGA For Water Treatment Project

With the advances and development of modern industry, the automatic and intelligent control for sewage treatment system has become an inevitable trend. The conventional control system use PLC as control unit. However, the system performance is limited for further improvement because of the limited data processing capability of PLC. Although the data acquisition system based on embedded processor represented by ARM has a better performance, but the I/O resources are limited and the system is not conducive to upgrading due to its inflexibility. For now, small and medium water plants have the characteristics of low degree of automation and insufficient funds. They need new technology urgently to solve the problem of high cost and high maintenance spending for introducing foreign equipments. According to these needs and actual situation, a new sewage treatment data acquisition system based on NiosⅡis designed in this paper.After analysising research status at home and abroad of water treatment and data acquisition system, overall plan of data acquisition system based on FPGA is established. According to actual need of water treatment, digital input module, digital output module, analog input module and analog output module are designed, so the system has function of collecting and outputting both switching value and analog value. CAN bus is adopted to enhance reliability. FPGA of Altera Corporation is used as core control unit of system, and its type is EP2C70F896C6. Multi-task scheduling is realized by transplantingμC/OSⅡembedded real-Time operating system. Communication of system is realized by programming CAN driver. And Protocol convertion between CAN and RS232 is also designed, which makes it possible to output data through serial port. Moreover, a digital filtering algorithm is added in system to enhance the anti-jamming ability. At last, system testing is performed. Experimental results show that the system achieves the desired data acquisition and communication functionality. The maximum error of AD sampling is no more than 30mV. The average error of DA sampling is 12mV. The system can run up to 117MHz, and has good flexibility and cost-effective.