PI 제어기의 입력제한을 이용한 사출 성형기 온도제어

Temperature Control of Injection Molding Machine using PI Controller with Input Restriction

  • 발행 : 2007.03.01

초록

Injection molding is the most common method of shaping plastic resins for manufacturing a variety of parts. This injection molding is accomplished by injection molding machines (IMM) which consists of a hewer, a reciprocating screw, barrel assembly, and an injection nozzle. The plastic resin is fed to the machine through the hopper and it should be heated to the target melting temperature, which depends on material properties, as closely as possible with very small temperature overshoot in the barrel. Since the barrel, which has temperature dependent specific heat and thermal conductivity in the operating temperature range, is heated by the several electric heater bands, it is not an easy task to control the temperature of the barrel owing to the interference of neighboring heaters and its material properties. Though PID controller with auto-tuning capability is widely adopted in the nm, the auto-tuning process should be carried out whenever the operating temperature is changed significantly. Recently, though the predictive controller is developed and shows good performance, it has drawbacks: 1. Since the heat transfer modeling process is very complicated and should be carried out again when the barrel is changed, it is somewhat inappropriate in the field. 2. The controller performance is not validated in whole operating temperature range. In this paper, cascade type simple PI controller with input restriction is proposed to find the possibility of controlling the barrel temperature in the whole operating temperature range. It is shown by experiment that the proposed controller shows good performance. This result can be applied to design of PI controller with auto-tuning capability.

키워드

참고문헌

  1. 플라스틱 사이언스 정보 DB 서비스, http://www.plasticinfo.co.kr
  2. V. G. Gomes, W. I. Patterson, and M. R. Kamal, 'An injection molding study, Part II: Evaluation of alternate control strategies for melt temperature', Polymer Sci. Eng., vol. 26, no. 12, pp.854-866, 1986 https://doi.org/10.1002/pen.760261205
  3. R. Dubay, A. C. Bell, and Y. P. Gupta, 'Control of plastic melt temperature: a multiple input multiple output model predictive approach', Polymer Sci. Eng., vol. 37, no. 9, pp. 1550-1563, 1997 https://doi.org/10.1002/pen.11803
  4. C. Diduch, R. Dubay, and W. G. Li, 'Temperature control of injection molding. Part I: Modeling and identification', Polymer Sci. Eng., vol. 44, no. 12, pp. 2308-2317, 2004 https://doi.org/10.1002/pen.20258
  5. C. Diduch, R. Dubay, and W. G. Li, 'Temperature control of injection molding. Part II: Controller design, simulation, and implementation', Polymer Sci. Eng.,, vol. 44, no. 12, pp, 2318-2326, 2004 https://doi.org/10.1002/pen.20259
  6. A measurement of heat transfer in a reheating furnace and its computation method, a subcommittee on reheating furnace, The Iron and Steel Institute of Japan, 1971
  7. L. Ljung, System Identification - Theory For The User, 2nd ed., Prentice Hall, 1999
  8. G. F. Franklin, J. D. Powell, and M. Workman, Digital Control of Dynamic Systems, 3rd ed., Addison Wesley, 1998