Abstract
Integrating systems are frequently encountered in the oil industry (oil–water–gas separators, distillation columns), power plants, paper-production plants, polymerisation processes, and in storage tanks. Due to the non-self-regulating character of the processes, any disturbance can cause a drift of the process output signal. Therefore, efficient closed-loop control of such processes is required. There are many PI and PID controller tuning methods for integrating processes. However, it is hard to find one requiring only a simple tuning procedure on the process, while the tuning method is based either on time-domain measurements or on a process transfer function of arbitrary order, which are the advantages of the magnitude optimum multiple integration (MOMI) tuning method. In this paper, we propose the extension of the MOMI tuning method to integrating processes. Besides the mentioned advantages, the extension provides efficient closed-loop control, while PI controller parameters calculation is still based on simple algebraic expressions, making it suitable for less-demanding hardware, like simpler programmable logic controllers (PLC). Additionally, the proposed method incorporates reference weighting factor b that allows users to emphasize either the disturbance-rejection or reference-following response. The proposed extension of the MOMI method (time-domain approach) was also tested on a charge-amplifier drift-compensation system, a laboratory hydraulic plant, on an industrial autoclave, and on a solid-oxide fuel-cell temperature control. All closed-loop responses were relatively stable and fast, all in accordance with the magnitude optimum criteria.
Highlights
The most used control algorithm in the industry is PID control
We propose the extension of the magnitude optimum multiple integration (MOMI) tuning method to integrating processes
Experiment results showed that the proposed MOMI method gave very good closed-loop responses for a broad range of process models when compared to some other methods
Summary
The most used control algorithm in the industry is PID control. It is widely used in various processes due to its tuning simplicity, good control performance, and robustness in a wide range of operating conditions. Most tunings methods for first-order integrating systems with time-delay can be applied in higher-order systems by approximating the process as an IFOTD model [30,32,33,34,35,39,40,43,44,45,47,48,50, 51]. Some of the tuning methods set the controller integrating gain to zero (Eriksson et al [38], Kuzishchin et al [46]) Those methods are not suitable for rejecting process input disturbances. Jeng [53] proposed a PI/PID controller method that was based on the direct synthesis approach and specification of the desired closed-loop transfer function for disturbances.
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