Rotor levitation by active magnetic bearing using digital state controller

Active magnetic bearings (AMB) find extended application in high-speed rotating electrical machines due to the contact-free operation, which reduces the overall machine wear. Previous research on the control system for the AMB dealt mostly with PID controller, with its advantage of simple design. Improvements using faster control access to the plant can be realized by state-space control. Additionally, the magnetic bearing as a MIMO (multiple-input multiple-output) system can be better described by the state-space equations. A digital state controller is applied to levitate a rotor of a 40-kW 40000-rpm PM synchronous machine. Simulation and measurement results are given for zero speed operation at an AMB test-rig.