Research On Rotor Position Self-sensing And Power Amplifiers Of Active Magnetic Bearings

Active magnetic bearing (AMB) is one kind of high performance bearing which levitates a rotor in the space by magnetic forces without machinery contact between the rotor and the stator. It is the most representative machinery integration product which relates to many science fields such as mechanics, rotor dynamics, control engineering, electromagnetics, computer science and so on. Compared with the traditional ball bearing, sliding bearing and oil bearing, the magnetic bearing has a series of merits, such as no machinery friction, low energy consumption, small noise, long life, needless to lubricate, no pollution and so on. It has broad application prospect in many high tech domains such as the energy and transportation, the mechanical industry, the avigation and spaceflight, the robot and so on.In order to realize rotor position control in the magnetic bearing system, a closed loop position feedback control system is needed to be established. At present domestic mostly uses the position sensor, but the existence of the position sensor causes the magnetic bearing's axial size increases, the system controller's design complex, the dynamic performance reduces, moreover the system's high cost and low reliability, these have greatly limited the application of magnetic bearing in industry. In order to overcome the series of shortcomings which the sensor brings, oninternational appeared a new research direction------self-sensing magnetic bearing. Inthe self-sensing magnetic bearing system, the rotor displacement is obtained from the current or voltage signal on electromagnetic winding. The self-sensing magnetic bearing has a series of merits because of position sensorless.This article introduced self-sensing methods and self-sensing principles, and has given particular analysis and mathematics reasoning on small signal self-sensing method and differential transformer self-sensing method. Based on the theoretical analysis, designed and simulated the differential transformer self-sensing system which can output high power. The simulation result indicated that using differential transformer test method can accurately gain the rotor displacement information, and realized the rotor's stable aerosol.The power amplifier is an important part of magnetic bearing system, it acts according to the controller's output to produce proportion current signal in magnetic bearing stator coil, so as to produce the needed electromagnetic force. The power amplifier is executor of the controller's control command, its performance has important influence on the overall system. In order to enhance the performance of self-sensing magnetic bearing system, this article adopt phase-shift method to design tristate control power amplifier and tristate bias power amplifier which apply to differential transformer self-sensing method based on tristate power amplifier theory, the simulation and the experimental study indicated that the designed power amplifier has finer performances than the ordinary double-state power amplifier.