Design And Research Of The Constant Temperature Control System On Air Source Water Heater

Since the advent of the air source water heater, with its characteristics of energy-saving,efficient and safe，The air source water heater quickly occupied the water heater market, andwould be bound to the future development direction of the water heater. Its stable and reliableoperation can not be separated from the control and regulation of the constant temperaturecontrol system. The constant temperature control system is the brain and central nervoussystem of the air source water heater. Its response speed, accuracy and intelligence is thecurrent focus of the study of the constant temperature control system on air source waterheater.This paper describes working principle of the air source water heater, and used it tointroduce to the method for the constant temperature control system of the air source waterheater. Through has been analyzed the advantages and disadvantages of using PLC and MCUto made the constant temperature control system in the past time, we found that they were thelow degree of system integration and anti-interference ability. Therefore the constanttemperature control system of air source water heater is designed by FPGA.In this paper, the topic is discussed in detail from the hardware, the constant temperaturecontrol system control algorithm and software design. There are two main parts of thehardware design：the circuit design of signal acquisition and processing unit, the circuit designof display and setting unit, two unit communicate with each other by using RS485communication mode. Next is the control algorithm and software design. Based on theanalysis of the characteristics of control system, a suitable control characteristics of thecontrol algorithm—optimization PID control algorithm is designed. Optimization PIDalgorithm is based on digital PID algorithm, Joined the feedforward control, the change rateof the temperature control, track control valve. Next, the optimal PID control algorithm isanalyzed, in the QuartusII software by using Verilog language and FPGA IP nucleus, it isimplemented. In the part of software design, based on the analysis of the software functiondemand on the constant temperature control system of air source water heater, the wholesoftware control flow of the constant temperature control and the procedures of optimizationalgorithm of PID control are designed. And it is achieved by FPGA. In Modelsim, thefunction of each module is simulated, and the program is proved to be correct.Finally, in test field, combined with air source water heater, an overall functional testingand validation on the temperature control system is taken and test results are analyzed.According to the analysis of the test results, the system has the control effect of fast responsespeed, high stability, high precision of temperature and can according to the environment temperature intelligent energy-saving features, the temperature control system has been putinto use. At the end of this article, the further work on the constant temperature control systemof air source water heater is summarized and prospects.