Model-free and time-constant prediction for closed-loop systems with time delay. (December 2018)

• Record Type: Journal Article
• Authors: Saków, Mateusz; Marchelek, Krzysztof
• Is Part Of: Control engineering practice. Volume 81(2018)
• Page Start: 1
• Page End: 8
• Publication Date: 2018-12
• Subjects: Closed-loop control -- Model-free prediction -- Smith predictor -- Transport delay; Automatic control -- Periodicals; 629.89
• DOI: 10.1016/j.conengprac.2018.08.021
• Languages: English
• ISSNs: 0967-0661

Abstract

Abstract: This study presents a model-free method of signal prediction dedicated to closed-loop systems affected by time delay. The proposed prediction method leads to better prediction results than the Smith Predictor for relatively small delays. Moreover, the solution is dedicated to complex systems, which are susceptible to differences between the system and its model. The theoretical analysis, experiments, and comparisons performed in this study confirmed these features. This paper presents simplifications that were conducted to obtain the Prediction Block directly from the Smith Predictor control scheme. The Prediction Block, under specific conditions, allows for signal prediction with a constant time value. The Prediction Block was compared with an ideal anticipatory object. Furthermore, the Smith Predictor control scheme was compared with the proposed method. In this case, the transport-delay value in the closed-loop system is the only information required for proper prediction. An adapted Nyquist criterion that can prove the asymptotic stability of the control scheme was proposed. The theoretical part of the paper was supported by experiments performed on an experimental test stand with a hydraulic manipulator. In the experiments, the Prediction Block improved the position tracking of the system. The prediction control scheme has already demonstrated widespread potential for applications in multiple control approaches and experiments. The solution is dedicated to complex systems that are susceptible to differences between the system and its model. Graphical abstract: Highlights: A simple and model-free signal prediction dedicated to closed-loop systems. Prediction time depends only on one value of the transport delay. An adopted Nyquist stability criterion dedicated to the control scheme was proposed. The prediction based control scheme reduced the position overshoot by 20% during experiments.