One point relay identification experiment based on constant-phase filter
Using standard relay identification methods, one obtains a critical frequency response point with the phase shift 180 degrees. Such phase is not optimal for consequential PI(D) controller design especially when there is no additional knowledge about the process. This paper presents a new low-order filter providing arbitrary constant phase at about three decades. Such filter embedded into relay tuner shortens the experiment significantly and helps to identify the sample with arbitrary phase shift. The authors believe that presented approach may lead to improvement of existing relay autotuners.
Using standard relay identification methods, one obtains a critical frequency response point with the phase shift 180 degrees. Such phase is not optimal for consequential PI(D) controller design especially when there is no additional knowledge about the process (e.g. static gain). Currently, an adaptive filter is used to get a frequency response sample with different phase shift. Adaptive filter parameters are tuned during the identification experiment. Unfortunately, the adaptation makes the experiment more time consuming. This paper presents a new low-order filter providing arbitrary constant phase at about three decades. Such filter embedded into relay tuner shortens the experiment significantly. Further, the paper discusses several implementation aspect. The authors believe that presented approach may lead to improvement of existing relay autotuners.
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