Articles written in Sadhana

    • Design, analysis, fabrication, control and comparative study of two different-shaped plate levitation prototypes


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      This paper presents a comparative study on the design, modelling, electromagnetic analysis based on finite-element software, fabrication and experiment on rectangular flat (148 g) and C-shaped (148 g) levitationprototypes based on steel plates. No mechanical restrainer has been used in the transverse direction for the levitation. This aspect of the work is an improvement over existing work reported in the published literature. The entire set-up has been designed, fabricated, analytically investigated and experimentally evaluated and verified. The finite-element model (FEM) has been derived using standard commercial package(s). The analytical model has been obtained using specific permeance concepts following Robert Pohl’s method. Excellent correlationbetween the predicted and experimental results is a highlight of the work. The stability against transverse mechanical perturbation has also been investigated. Control system design and implementation is successfully done.

    • Detailed comparative investigations on levitation prototypes of a ball and a rectangular plate of same mass using a novel analytical model and experiments


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      This paper presents a comparative study between lab-developed attraction-type levitation prototypes of two different objects with different geometries but, importantly, the same mass. Effects of continuous geometry without sharp corners in spherical ball vis-a-vis that of the plate having sharp corners introducesignificant changes in the analysis, operation and set-up development arising out of this subtle but characteristic geometric difference, which lead to change in configuration of field lines. This broadly reflects on the design, finite-element analysis, modelling, stability analysis, fabrication and controller design. The challenges and stepwise procedures in design and fabrication for this change from a spherical shape to cuboid shape for the same mass of levitated object have been highlighted in this work. Inductance, force and current vs. air-gapcharacteristics, etc. have been determined first using the proposed novel and simplified analytical formulation and then using finite-element (FE)-analysis-based software packages. Particularly, specific permeance-based approach originally proposed by Robert Pohl for inductor alternators having double saliency is extended here successfully for analytical formulation that has not been adopted by other researchers. The proposed analytical model can be used to obtain a sufficiently accurate design, starting from nominal ratings, and hence for building the model geometry for the FEM analysis. The FEM analysis cannot be conducted unless one has the model geometric dimensions. The results thus obtained have been verified by actual experiments too. Thereafter, the mathematical models for control of the systems have been derived analytically. There exists a good agreement between predicted and measured results. This implies that the system modelling is precise, which leads to accurate design and implementation of controllers. Analog controllers have been designed, analysed, implemented and practically experimented upon with steady levitated position for both the systems.

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