Development Of Automatic Verification Device For Refrigerators

With the continuous promotion of the Made in China 2025 plan,the refrigerator industry has put forward higher requirements for energy efficiency grade,air cooling technology,large volume,intelligent control and other aspects.Therefore,the refrigerator should be tested for its temperature control accuracy,thermal insulation efficiency,electromagnetic compatibility,etc.before leaving the factory to ensure the quality of the product.Based on the research task with practical engineering background,this thesis conducts in-depth research on refrigerator signal acquisition,analysis and field communication technology.Analyze the current refrigerator verification standards and requirements,determine the parameters and environment required for verification,discuss the research status and development trend of the refrigerator verification device,propose the research objectives and research contents of the refrigerator automatic verification device in this thesis,and provide the direction for the development of the refrigerator automatic verification device.This thesis analyzes the calculation methods of the voltage effective value,current effective value and active power of the discrete data,puts forward the calculation of the harmonic component in the electric energy signal based on the full-phase FFT bispectral correction algorithm,discusses the calculation of the thermal resistance and thermocouple graduation coefficient by the equal-precision least square method,and gives the calculation formula of the adjusted volume and efficiency index of the ice box calibration,which provides a theoretical basis for the application algorithm of the automatic refrigerator calibration device.Through the analysis of the overall scheme of the refrigerator automatic verification device,the design index of the power supply of the refrigerator automatic verification device is determined,and the single-end flyback switching power supply and EMI suppression protection circuit based on TOP224 are designed to improve the reliability and stability of the device operation;STM32F373 with multi-channel SDADC and DSP functions is used as the embedded microprocessor to improve the signal acquisition accuracy and data processing speed;The eight-channel thermocouple and high-precision instrument amplifier are used to design the temperature signal conditioning circuit,and the collected signal is selected by the multiplexer chip,in which the thermocouple uses the thermal resistance for cold junction compensation;The voltage and current signal conditioning circuit is designed by using transformer and zero-temperature drift operational amplifier;The multi-slave communication circuit based on RS-485 field bus is designed to improve the antiinterference of the device and reduce the wiring cost of the device.Analyze the data acquisition,data processing,and data communication process of the refrigerator automatic calibration device,determine the basic peripherals and usage algorithms of the embedded microprocessor used,and write corresponding programs;Based on the communication data and the required parameters for calibration,design the Labview upper computer interface to complete the management,recording,and display of calibration data.In this thesis,the proposed data processing algorithm is simulated and analyzed using MATLAB to verify the feasibility and accuracy of the data processing algorithm;Multisim is used to simulate the design circuit and compare it with the design theory to check the rationality and accuracy of the design;Build a test platform to test the function of the refrigerator automatic calibration device and the upper computer,and the error between the data processing results and the theoretical values meet the design requirements;The refrigerator automatic verification device has the advantages of controllable cost,simple operation and accurate results,and has a good application prospect.