상태공간 모델을 이용한 공작기계용 압축기 가변속형 냉각기의 최적 제어

Abstract

In this paper the control method of compressor variable speed(CVS) is deal as the main study. The CVS system is possible to satisfied demand of high speed, high precision and high efficiency. Input variables of this system are compressor speed and opening angle of EEV, and the output variables are outlet temperature and superheat. Therefore, this system is multi-input multi-output(MIMO) system. Generally, the PID control method or fuzzy method are used to control the CVS system. The PID control method is widely used to control cooler system. However, the CVS system is considered as single-input single-output(SISO) system. The fuzzy control methods have merits in easy to control and easy to apply based on expert experiences. However, it was hard to get precise control performance and the control performance was depended on expert ability. In addition, the energy consumption. is not considered by both methods above. Therefore, the optimum control method is proposed to control the CVS system in this paper. This optimum control method is based on state space model, so the model can deal with MIMO system. In addition, this method can achieve optimum control by using evaluation function that variables are control error and input energy. To implement the proposed system, state space model of the CVS system is designed firstly. Then the state space model expanded to servo system for dealing with model uncertainty. Finally, the optimum gain was decided by using evaluation function. Furthermore the proposed control method is checked by experiments of starting characteristic, changing control late, and changing heat load.