| 摘要 |
PURPOSE:To accurately determine PID (Proportion Integral Derivate) constant by shortening a time period of a time proportional output circuit at the generation of a limit cycle. CONSTITUTION:When a feedback control system is turned on, the 1st and 2nd switching parts 9A, 9B of a limit cycle starting means are synchronously switched by an AtSP value setter 8, a limit cycle is generated and a time proportional output period switching signal adjusted so as to be shorted to be used for the limit cycle by an adjusting duty ratio converting means 12 is sent to a time proportional output circuit 10. Consequently, a time proportional output period 20 at the time of the limit cycle becomes a period 21 shorter than that of PID control (i.e. normal control other than auto-tuning) when the AtSP value coincides with a PV value, so that delay is also reduced to a small value which may be ignored in accordance with the shortened period. Thus, the amplitude and period of the limit cycle are stabilized, an ON/OFF command is prevented from being delayed and the reproducibility of determination of the PID constant is secured and stabilized.
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