Title: A fuzzy logic modified Smith predictor for IPDT process control

Authors: Hao Chen; Zoubir Zouaoui; Zheng Chen

Addresses: Institute for Arts, Science and Technology, Glyndwr University, Mold Road, Wrexham, Wales, LL11 2AW, UK. ' Institute for Arts, Science and Technology, Glyndwr University, Mold Road, Wrexham, Wales, LL11 2AW, UK. ' Institute for Arts, Science and Technology, Glyndwr University, Mold Road, Wrexham, Wales, LL11 2AW, UK

Abstract: This paper presents a development of a modified Smith predictor for integrator-plus-dead-time (IPDT) process control. An IPDT process plant is intentionally modelled by a first-order-plus-dead-time (FOPDT) model within the predictor in order to nullify the effect of disturbances. Results show that the IPDT - FOPDT Smith predictor can successfully suppress disturbance loading. Stability analyses have carried out with the Lyapunov criterion for generic cases. Bode plot analysis shows a good stability for an IPDT process control case study. To reduce the overshoot of a process response during the transient response for a set-point tracking, a fuzzy-logic-based method for set-point weight tuning of a PID controller was applied. Simulation results demonstrate that this new modified Smith predictor has superior robustness to process dead time modelling error and good performance for set-point tracking and disturbance rejection.

Keywords: integral process; dead time; Smith predictor; fuzzy logic; process control; modelling; disturbance loading; set-point weight tuning; PID controller.

DOI: 10.1504/IJESMS.2012.048665

International Journal of Engineering Systems Modelling and Simulation, 2012 Vol.4 No.3, pp.155 - 161

Received: 08 Jul 2011
Accepted: 17 May 2012
Published online: 30 Aug 2014 *

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