AN IMPROVED RELAY AUTO TUNING OF PID CONTROLLERS FOR CRITICALLY DAMPED SOPTD SYSTEMS
2012; Taylor & Francis; Volume: 199; Issue: 11 Linguagem: Inglês
10.1080/00986445.2012.668863
ISSN1563-5201
Autores Tópico(s)Radio Frequency Integrated Circuit Design
ResumoAbstract Using a single-symmetric relay feedback test, a method is proposed to identify all three parameters of a stable second-order plus time delay (SOPTD) model with equal time constants [kp exp(-Ds)/(τs + 1)2]. The conventional analysis of the relay auto-tune method gives 27% error in the calculation of ku, for a large D/τ. In the present work, a method is proposed to improve the accuracy in the ku calculation by incorporating higher order harmonics. Three simulation examples are given for SOPTD and higher order time delay transfer function models. The estimated model parameters of the SOPTD model are compared with those of the Li et al. (1991 Li , W. , Eskinat , E. , and Luyben , W. L. ( 1991 ). An improved auto tune identification method , Ind. Eng. Chem. Res. , 30 , 1530 – 1541 .[Crossref], [Web of Science ®] , [Google Scholar]) method and those of the Thyagarajan and Yu (2003 Thyagarajan , T. , and Yu , C. C. ( 2003 ). Improved auto tuning using the shape factor from relay feedback , Ind. Eng. Chem. Res. , 42 , 4425 – 4440 .[Crossref], [Web of Science ®] , [Google Scholar]) method. The open-loop performance of the identified model is compared with that of the actual system. The proposed method gives performance close to that of the actual system. Simulation results are also given for a nonlinear bioreactor system. The closed-loop performance of the model identified by the proposed method is close to that of the actual system. Keywords: Auto tuningCritically damped systemIdentificationSoptd modelSymmetric relayTransfer function
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