Intelligent predetermined control method for sinusoidal temperature testing on a cylindrical environmental chamber

摘要

The Intelligent Predetermined Control Method (IPCM) aims to predetermine the requirements of programmed changes in the test chamber, which differentiates from the gain-scheduling PID (GS-PID) control method in accordance with dry and wet bulb temperature errors. The IPCM consists of a scheduling of optimal control path, a determination of the heat and water vapor mass flow rates along the path, an estimation of heat loss from walls of chamber, and a compensation for unexpectedness with a fixed-gain PID controller. In order to verify the feasibility of the sinusoidal temperature test by using the IPCM, a cylindrical test chamber with independent flow loops was designed, and it equips a precise heating system and a variable refrigerant flow (VRF) cooling system with a variable-frequency drive (VFD) compressor. This paper uses process models with nonlinear gain to identify the models of the heating and cooling systems individually. An experiment was performed by using a 5-45 °C sine wave excitation. The results show that the temperature in the chamber closely tracks along the programmed sine wave excitation with less than ±0.25°C of errors in almost entire cycles, which indicates that the IPCM is able to advance the chamber testing into the acceleration test beyond the ordinary step and ramp excitation.