Abstract: The control system of magnetic bearing has a complex structure. Even the damage of a single control channel will lead to the failure of the whole magnetic bearing system. The reliability requirements limit magnetic bearings from being used in critical applications. To improve the reliability, a fault-tolerant current distribution scheme is presented for a magnetic bearing biased by permanent magnet. In this scheme, the one-dimensional magnetic circuit is used to analyze the force nearby the equilibrium point, and the current distribution matrices are obtained through analyzing the relationship between the normal control-current and the fault control-current. The scheme is effective and easy to implement in engineering. The experimental results indicate that the fault-tolerant scheme can realize static suspension and speed-raising of magnetically suspended flywheel on condition that the coil (power amplifier) is damaged, thus improving the reliability of the magnetic bearing system.

Key words: Fault-tolerant control, Homopolar, Magnetic bearing, Reliability