Title :
Controllability improvement of zero-power magnetically levitated system by dither
Author :
Tomono, Hirotaka ; Kiwaki, Hisakatsu
Author_Institution :
Dept. of Electr. Eng., Kyushu Sangyo Univ., Fukuoka, Japan
Abstract :
A zero-power magnetically levitated (MAGLEV) system using a permanent-electro hybrid magnet has a defect of current fluctuation due to nonlinearity of the intermittent domain of a PWM-controlled current controller which may cause unfavorable vibration to the levitated object. To improve controllability, application of dither to the current controller is studied. Transfer characteristics of the current controller applied by dither have a tendency to show better linearity but lower gain. Measured and analysis results by the describing function method agree very well. A current controller with 11 kHz PWM carrier and 500 Hz dither frequency shows very little current fluctuation without current feedback. As a result, a MAGLEV model using the current controller realizes very quiet levitation without vibration
Keywords :
PWM power convertors; bridge circuits; controllability; describing functions; electric current control; electromagnets; magnetic levitation; transportation; 11 kHz; 500 Hz; MAGLEV model; PWM-controlled current controller; controllability improvement; current fluctuation defect; describing function method; dither; permanent-electro hybrid magnet; transfer characteristics; zero-power magnetically levitated system; Control systems; Controllability; Fluctuations; Frequency; Linearity; Magnetic domains; Magnetic levitation; Nonlinear control systems; Pulse width modulation; Vibration control;
Conference_Titel :
Power Electronics Specialists Conference, 1998. PESC 98 Record. 29th Annual IEEE
Conference_Location :
Fukuoka
Print_ISBN :
0-7803-4489-8
DOI :
10.1109/PESC.1998.701958
