Magnetic levitation systems are able to provide frictionless, reliable, fast and economical operations in wide-range applications. The effectiveness and applicability of these systems require precise feedback control designs because the magnetic levitation is an unstable process and have highly nonlinear dynamics. In this article, a robust sliding mode–based cascade control approach is proposed for effectively tracking the reference position of a magnetic levitation system. The magnetic levitation plant is described with electrical and mechanical models, and the control problems of these parts are treated with cascade controllers. An integral sliding mode and an output feedback sliding mode controllers are designed for use in the cascade loops. The performance of the sliding mode controllers is compared with a proportional–integral–velocity plus proportional–integral control structure. It is shown that the proposed control structure is able to provide a highly satisfactory tracking performance and can eliminate the effects of the inductance-related uncertainties and operating point originated disturbances. The experimental results are provided to validate the efficacy and feasibility of the approach.

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Abstract. The effectiveness and applicability of magnetic levitation systems need precise feedback control designs. A cascade control approach consisting of sliding mode control plus sliding mode control (SMC plus SMC) is designed to solve position control problem and to provide a high control performance and robustness to the magnetic levitation plant. It is shown that the SMC plus SMC cascade controller is able to eliminate the effects of the inductance related uncertainties of the electromagnetic coil of the plant and achieve a robust and precise position control. Experimental and numerical results are provided to validate the effectiveness and feasibility of the method.

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In Arabic grammar there are a group of words that differ in terms of their properties and shapes It is very important to understand the meaning of the words that are included in the curriculum of the Quran and are named as garib because their meaning is not known by everyone. In general, the Quran, which was downloaded as Arabic in the Quraysh dialect, contained words belonging to different dialects, and the presence of some words that were muarreb in Arabic from some other languages were seen as garib by people who were not familiar with these words. In addition, many new words that the Arabs never used before or used in different meanings became religious terms and concepts in time, and in Arabic mutter (two or more words having the same meaning), azdad (one word having two opposite meanings), common (one word meaning two or more) etc. The diversity of wording in many ways caused such words to be perceived as strange. Again, as a result of the Islamic conquests, the fact that the Arabs gradually moved away from corruption made it difficult to understand the Quran compared to the first period, and this was one of the most important reasons for more words to be regarded as garib. At the same time, the most common features of the verbal adjectives in Arabic language were investigated in the article.