Design Of Self-diagnosis System For Electric Control Board Of Variable Frequency Air Conditioner

The electronic control board of variable frequency air conditioning is the core component in the electronic circuit of air conditioning.If the failure of the electronic control board of air conditioning can not be found in time,it will not only increase the follow-up maintenance costs and time,but also give users use and enterprise image caused a bad impact.Therefore,how to make effective fault diagnosis for the electric control panel is an urgent problem to be solved in the production of electric control panel for air conditioning.This thesis takes the electronic control board of variable frequency air conditioning as the research object,analyzes the working principle of its circuit,and summarizes the functional requirements and technical indexes of the electronic control board fault diagnosis system.Based on the analysis of the characteristics of the output signal of the electronic control board circuit,the overall design scheme of the system was proposed,and the hardware and software design of the fault diagnosis system of the electronic control board for variable frequency air conditioning was completed,as well as the research on the fault location algorithm.The specific work contents are as follows:STM32 is used for the hardware design of signal acquisition module,which mainly includes multi-channel analog signal acquisition,multi-channel pulse signal acquisition,analog excitation signal,RS-485 communication based on Modbus and other functional units.Hardware circuit design and software program design are carried out by module according to functional units.The Modbus communication protocol of RTU mode is adopted between the signal acquisition module and the upper computer.The custom data frame is designed to send and receive data.The address dial switch is used to select the address of the slave computer to realize the communication mode of master and multiple slaves.The host computer uses the Qt Creator as a platform to build a human-computer interaction interface.Users can configure user information and work order information through the human-machine interaction interface,use the SQLite database to save configuration data,and use multi-threaded programming ideas to send signal acquisition instructions to the signal acquisition module.And display fault diagnosis results on the host computer interface.In order to solve the problem of fault location in the electronic control board of variable frequency air conditioning,the fault location algorithm of the electronic control board of air conditioning is studied.Based on the analysis of frequency conversion air conditioning node transmission relationship between electric control board,on the basis of building air conditioning failure propagation digraph model of electric control board,and based on directed graph adjacency matrix model,using Warshall algorithm of matrix is obtained after the layered digraph model,according to the fault level and accessibility of node transmission constraints,locating fault source node.After the debugging and calibration of each module,the fault electronic control board is used to carry out the actual test to verify the effectiveness of the fault source node location algorithm.The test results show that the fault source nodes determined by the localization algorithm are consistent with the actual fault sources of the electronic control board,which indicates that the localization algorithm can effectively locate the fault source nodes.