Abdul Aziz Ishak, Dept. of Industrial Chemistry, Institut Teknologi MARA, MALAYSIA
Tel: 6-03-556-4881 / Fax: 6-03-559-7681 / E-mail: pidtuning@altavista.net / Webpage: https://members.tripod.com/aabi

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OPTIMUM PID CALCULATION FOR NON-SELF REGULATING (NSR) PROCESS
based on Zieglar-Nichols formulation

1. The Fundamental

2. Example using data captured using a paperless recorder

1. Td = 2.6 s
2. Process rate = (80% - 60%)/(32.4 s - 12.8 s) = 1.0204 % / s
3. Step input = MV2 - MV1 = 64.9% - 40.5% = 24.4%
4. RR = process rate / step input = 1.0204 / 24.4 = 0.04182 / s
5. Mode = PI : P = 111.1 x 0.04182 x 2.6 = 12.1% , I = 3.33 x 2.6 = 9 s

3. Example using data captured using a chart recorder

1. Td = 3.6 s
2. Process rate = (68% - 52%) / 21.6 s = 0.7407 % / s
3. Step input = MV2 - MV1 = 44.3% - 25.9% = 18.4%
4. RR = process rate / step input = 0.7407 / 18.4 = 0.04026 / s
5. Mode = PI : P = 111.1 x 0.04026 x 3.6 = 16.1% , I = 3.33 x 3.6 = 12 s

TEST YOUR SELF: Can you calculate the optimum PI for this process

19 July 1999

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