Browsing by Author "Pekař, Libor"

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Access status: Open Access ,
Enhancing a hierarchical evolutionary strategy using the Nearest-Better Clustering
(2024) Guzowski, Hubert; Smołka, Maciej; Pekař, Libor
Wydział Informatyki
A straightforward way of solving global optimization problems is to find all local optima of the objective function. Therefore, the ability of detecting multiple local optima is a key feature of a practically usable global optimization method. One of such methods is a multi-population evolutionary strategy called the Hierarchic Memetic Strategy (HMS). Although HMS has already proven its global optimization capabilities there is an area for improvement. In this paper we show such an enhancement resulting from the application of the Nearest-Better Clustering. Results of experiments consisting both of curated benchmarks and a real-world inverse problem show that on average the performance is indeed improved compared to the baseline HMS and remains on par with state-of-the-art evolutionary global optimization methods.
Access status: Open Access ,
Operating point shift induced by relay asymmetry: an iterative solution proposal
(2023) Pekař, Libor; Matušů, Radek; Guzowski, Hubert; Gazdoš, František
Wydział Informatyki
This contribution focuses on a problem that appears when using a relay with non-symmetric output in the closed loop. Such a scheme is usually used for process model parameters identification, possibly followed by automatic controller tuning. Whenever static or dynamic properties of the process reveal asymmetry when the sign of the input changes, the setpoint (reference) becomes different from the operating point value of the process output. As a class of relay-based identification methods utilize calculations in the frequency domain that are based on integral computation around the operating point, the discrepancy between the setpoint and the operating point can lead to incorrect results. The aim of the paper is mainly to provide the reader with problem formulation and step-by-step proposition of how it can be solved. Concise numerical examples are also given. The concluding remarks suggest possible further ways of research.