Performance of Classical Controllers for an Electromagnetic Levitation System: A Comparative Study
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CASE STUDY
Performance of Classical Controllers for an Electromagnetic Levitation System: A Comparative Study S. Banerjee • R. Bhaduri
Received: 19 June 2012 / Accepted: 25 June 2012 / Published online: 22 August 2012 Ó The Institution of Engineers (India) 2012
Abstract The electromagnetic levitation system (EMLS) is inherently unstable and strongly non-linear in nature. A linearized model has been developed for the proposed levitated system and different classical controllers have been designed for providing overall closed loop stability as well as satisfactory performance for such an unstable system. The main aim of this part of work is to compare with the different designed controllers for the proposed designed EMLS at different operating points and to suggest a suitable classical controller that will provide fast response without any overshoot and steady-state error which is generally required for such type of critical systems. Experimental comparison of different simulated controllers with the existing prototype has been highlighted. Keywords Electromagnetic levitation system Lag–lead controller Switched mode dc–dc chopper PWM control Stability margin
Introduction The suspension of objects with no visible means of support is quite fascinating. Overcoming the effect of gravity has been a dream for generation of thinkers. Modern
S. Banerjee (&), Member Department of Electrical Engineering, National Institute of Technology, QTR No.-DS-8C, N.I.T. Campus, Durgapur 713219, WB, India e-mail: [email protected] R. Bhaduri, Member Department of Electrical and Electronics Engineering, NSHM Faculty of Engineering and Technology, Durgapur, West Bengal 713212, India
applications of levitation in equipments like magnetic bearings and magnetically levitated vehicles have given renewed impetus to research efforts in the direction of electromagnetic levitation [1–3]. Advances in control electronics and superconducting materials have also contributed to further research in the area of electromagnetic levitation. Magnetic levitation trains are becoming a popular transportation topic all round the globe. Currently maglev trains have been created in Germany and Japan for test runs only. Some other applications of electro-magnetic levitation, apart from the application in frictionless bearings and maglev vehicles, are in the fields of levitation of models in a wind tunnel, vibration isolation of sensitive machinery, levitation of molten metal in induction furnaces, levitation of metal slabs during manufacture etc. [4–6]. In any dc electromagnetic levitation system (EMLS) an attractive force is developed between the electromagnet and the ferromagnetic object. The force of attraction between two magnetized bodies is directly proportional to the square of the coil-current and inversely proportional to the square of the air-gap between the pole-face of magnet and the ferromagnetic object. Due to the negative slope of the inverse characteristics between force and air-gap, one pole of the transfer-function model of the levi
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