Korean Journal of Air-Conditioning and Refrigeration Engineering (설비공학논문집)

The Society of Air-Conditioning and Refrigerating Engineers of Korea (대한설비공학회)
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Optimization of a PI Controller Design for an Oil Cooler System with a Variable Rotating Speed Compressor

가변속 압축기를 갖는 오일쿨러의 최적 PI 제어기 설계

  • Kwon, Taeeun (Graduate School of Refrigeration and Air Conditioning Engineering, Pukyong National University(PKNU)) ;
  • Jeong, Taeyoung (Training Ship, Pukyong National University(PKNU)) ;
  • Jeong, Seokkwon (Department of Refrigeration and Air Conditioning Engineering, Pukyong National University(PKNU))
  • 권태은 (부경대학교 대학원 냉동공조공학과) ;
  • 정태영 (부경대학교 실습선) ;
  • 정석권 (부경대학교 냉동공조공학과)
  • Received : 2016.08.01
  • Accepted : 2016.10.20
  • Published : 2016.12.10
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Abstract

An optimized PI controller design method is presented to promote the control performance of an oil cooler system for high precision machine tools. First, a transfer function model of the oil cooler system with a variable rotating speed compressor was obtained by the perturbation method as the first order system with a negligible dead time. Then, the closed-loop control system was described as the second order system with a zero. Its dynamic behaviors are mostly governed by characteristic parameters, the damping ratio, and the natural frequency which is incorporated in PI gains. Next, an optimum integral of the time-weighted absolute error (ITAE) criterion was applied to the second order system. The characteristic parameters can be determined by the given design specifications, percent overshoots and settling times and comparisons with the ITAE criterion. Hence, the PI gains were plainly identified in a deterministic way. Finally, the PI gains were fine-tuned to obtain desirable dynamics in real systems, considering the zero effect and parameter variations. The validity of the proposed method was proven by computer simulations and real experiments for selected cases.

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References

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