Optimized Realization of Fault-Tolerant Heteropolar Magnetic Bearings

Abstract

Flux coupling in heteropolar magnetic bearings permits remaining active coils to assume actions of failed coils to produce force resultants identical to the un-failed actuator. This fault-tolerant control usually reduces load capacity because the redistribution of the magnetic flux which compensates for the failed coils leads to premature saturation in the stator or journal. A distribution matrix of voltages which consists of a redefined biasing voltage vector and two control voltage vectors can be optimized in a manner that reduces the peak flux density. An elegant optimization method using the Lagrange multiplier is presented in this paper. The linearized control forces can be realized up to certain combination of 5 poles failed for the 8 pole magnetic bearing. Position stiffness and voltage stiffness are calculated for the fault-tolerant magnetic bearings. Simulations show that fault-tolerant control of the multiple poles failed magnetic bearings with a horizontal flexible rotor can be achieved with reduced load capacity. [S0739-3717(00)01103-X]

An online fault-diagnosis of electromagnetic actuator based on variation characteristics of load current

“…Relying on the coupled magnetic circuit between the adjacent magnetic poles, the loss of magnetic flux caused by the failures of some actuators can be compensated by the fault-tolerant controller discussed in [37]. Based on this idea, the subsequent researches [38][39][40][41][42] were developed to reconfigure the support structure.…”

Fault tolerance of magnetic bearings with material path reluctances and fringing factors

“…The fault tolerant magnetic bearing system was demonstrated on a large flexible-rotor test rig [4]. Na and Palazzolo [5] developed an optimization method to realize fault-tolerant magnetic bearings; up to five poles failed out of an eight-pole heteropolar magnetic bearing.…”

A Generalized Unbiased Control Strategy for Radial Magnetic Bearings

“…The solution can proceed in a similar way to that described in [5] or [7]. The W matrix is split into two columns denoted w 1 and w 2 , and Equation (11) is re-arranged into six independent conditions:…”

“…Alternatively, [7] creates a quadratic cost that attempts to minimize the total flux in the bearing (although not necessarily minimizing flux density at the worst part of the bearing). This strategy will be adopted in the present work because it is easier to implement and provides reasonable solutions.…”