핫가스 바이패스 및 압축기의 회전수 제어에 의한 공작기계용 냉각기의 초정밀 온도제어

Abstract

Recently, technical trend in machine tools is focused on enhancing of speed and accuracy. The high speed usually causes thermal displacement and structural deformation on objects of the machine tool. To minimize thermal effect, machine tools are adopting oil cooler with precise temperature control function. This paper presents precise temperature control of oil outlet in an oil cooler with hot-gas bypass and compressor's speed control as an industrial refrigerator. The control system was designed for obtaining steady state error within ±0.2℃ even though abrupt disturbances are added in the system. This final paper deals with design method of PI and predictive controller for obtaining precise temperature and energy saving. The controllers of compressor's speed and superheat are designed to maintain constant temperature of oil outlet and superheat. In addition, the predictive controller was designed to control the temperature of oil outlet precisely under abrupt disturbances. This paper showed that the PI gain could be easily determined by using a lot of simulations. The temperature of oil inlet was measured for predictive controller and it was reflected to the output of compressor's speed controller feedforwardly. Through some experiments, the system can control the target temperature within error of 0.2℃ under abrupt disturbances.