Abstract
In most of the industrial process plants, PI/PID controllers have been widely used because of its simple design, easy tuning, and operational advantages. However, the performance of these controllers degrades for the processes with long dead-time and variation in set-point. Up next, a PPI controller is designed based on the Smith predictor to handle dead-time processes by compensation technique, but it failed to achieve adequate performance in the presence of external noise, large disturbances, and higher-order systems. Furthermore, the model-based controllers structure is complex in nature and requires the exact model of the process with more tunable parameters. Therefore, in this research, a fractional-order predictive PI controller has been proposed for dead-time processes with added filtering abilities. The controller uses the dead-time compensation characteristics of the Smith predictor and the fractional-order controller’s robustness nature. For the high peak overshoot, external noise, and disturbance problems, a new set-point and noise filtering technique is proposed, and later it is compared with different conventional methods. In servo and regulatory operations, the proposed controller and filtering techniques produced optimal performance. Multiple real-time industrial process models are simulated with long dead-time to evaluate the proposed technique’s flexibility, set-point tracking, disturbance rejection, signal smoothing, and dead-time compensation capabilities.
Highlights
Simple control structure and easy tuning parameters made the PID controller trustworthy in process industries evien after the emergence of new process control strategies like model-based controllers, adaptive control, fault tolerance control, etc., [1]–[3]
Design of the proposed fractional-order predictive PI (FOPPI) controller using the conventional fractional-order PI controller and the smith predictor is elucidated in the first part
In the feedback loop a white noise signal of 0.01 magnitude shown in Fig. 3 is injected, for the filter evaluation, processes given in the Eqs. 14, 15, and 16 are used with the proposed FOPPI controller
Summary
Simple control structure and easy tuning parameters made the PID controller trustworthy in process industries evien after the emergence of new process control strategies like model-based controllers, adaptive control, fault tolerance control, etc., [1]–[3]. PI controller is largely adopted in the process and automation industry among all the PID variants [4], [5]. Conventional PI controllers are inadequate to be employed in a delayed environment, high-frequency noise, and other uncertainty systems [8]–[10]. In such environments, if the PI controllers are used, the system will lead to oscillatory and unstable response because of the limited gain constant [11], [12]. If the gain is large, the response becomes oscillatory with high peak overshoot and may lead to system instability. Several enhancements in conventional PI controller resulted in the development of different controllers like
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