Development Of High-precision Temperature And Humidity Test Box Control System

With China’s industrial upgrading and intelligent manufacturing capacity improvement,the demand for high-end calibration and measurement equipment is increasing,high-precision temperature and humidity experimental box as a kind of experimental equipment to produce constant temperature and humidity environment,widely used in medicine,measurement,electrical and other fields.The traditional temperature and humidity test chamber has low measurement accuracy and control accuracy,which cannot meet the high-precision requirements of temperature and humidity of contemporary calibration experiments,and it is difficult to ensure the accuracy of measurement value transmission.Therefore,the development of a high-precision temperature and humidity control system is of great practical significance to improve the domestic calibration level and accelerate the upgrading of the intelligent manufacturing industry.The main research content and work of this thesis are as follows:(1)Through the analysis of the structure and internal electrical principle of the temperature and humidity test box,the humidity generator and cold and heat source of dry and wet shunt method are proposed to cooperate with temperature control,and the temperature and humidity control performance indicators are determined according to the key technologies and corresponding calibration specifications of the system.(2)The generalized transfer function model of temperature and humidity of the temperature and humidity experimental chamber is calculated by the law of conservation of energy and the law of conservation of mass,the temperature and humidity transfer function is identified by step response method,the fuzzy PID control strategy of the temperature and humidity experimental chamber is proposed,the Z-N method is proposed to tune the initial parameters,the input and output quantization factors are determined and the fuzzy rule table is established,and the control effect is tested and analyzed by Simulink.It is proved that the control method has better dynamic performance and steady-state performance than fuzzy control and traditional PID control.(3)Developed the hardware circuit and software program of the temperature and humidity test box control system,and completed the temperature and humidity detection board and control board hardware circuit,mainly including: high-precision temperature,humidity acquisition circuit,constant current source drive circuit,dynamic commutation circuit,control output circuit,etc.;In order to achieve the requirements of high-precision temperature measurement,the segmented least squares fitting algorithm and the Kalman filtering algorithm are proposed,and the touchscreen human-computer interaction interface is drawn through the Mcgs Pro software,including the temperature and humidity data operation curve interface,parameter setting interface,alarm interface,etc.Complete schematic drawing and original machine experimental setup.(4)The application verification and control performance analysis of the proposed control strategy in the temperature and humidity test chamber show that the temperature control accuracy reaches ±0.05 °C,the resolution reaches 0.01 °C,the humidity control accuracy reaches ±0.1%RH,and the resolution reaches 0.1%RH,which can ensure the stability of temperature and humidity in long-term operation and meet the requirements of system performance indicators.