Digital Control of Active Magnetic Bearings for Precise Eccentric Rotor Positioning

Active Magnetic Bearing ( AMB ) control has been a challenging task for the control engineers since its invention. Various types of control techniques - both analogue and digital - have been tried over the past years. In the application area of rotating machines, the whole concept of AMB control means stabilising the rotor of the machine in the exact centre of the radial AMEs and maintaining that position by counteracting the disturbances exerted on it under running condition. Noise reduction in electrical machines is becoming an increasingly important requirement for the design engineers and rotor eccentricities have been identified as the main source of noise generation. AMB with its relatively large air gap, allows the rotor to move away from the exact centre, provided the controller used is capable of maintaining an eccentric position under running condition. The ability of running the machine with known eccentricities makes the AMB a good actuator to study the noise characteristics of electrical machines. The ultimate objective of the project aims at investigating the magnetic noise from a standard induction machine. This calls for a flexible design of the control that enables the user to move the rotor to an arbitrary position in the air gap. This demand is achieved by using a digital controller based on a DSP.