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

Abstract

Accurate and fast fault-diagnosis is the foundation of fault-tolerance. To develop the faulttolerance of magnetic-levitated bearing system, this paper presents an online fault-diagnosis approach of electromagnetic actuator based on variation characteristics of sampled load current in the modulation to identify the time constant of the electromagnetic coil, and then to diagnose the broken circuit or partial short-circuit faults. After analysing the variation characteristics of the load current theoretically, the simulation is constructed to verify the effectiveness of the proposed approach. Considering the real-time requirement of fault-diagnosis, we develop a fast sampling and calculating method for the equivalent slope of the load current in the modulation, which represents the variation characteristics of the load current. The experimental results demonstrate that the proposed approach is effective for diagnosing broken circuit and partial short-circuit faults, and the execution time for the fault-diagnosis is about 2 ms, proving its excellent real-time performance.

Design and Implementation of a Fault-Tolerant Magnetic Bearing Control System Combined With a Novel Fault-Diagnosis of Actuators

“…Furthermore, the singularities that belong to the sampling points and are likely to be an error factor in the calculation of inc k must be taken into consideration. An effective identification strategy to cancel these singularities has been presented in [31]. 7.…”

“…A real-time, threshold-based fault detection algorithm without a valid threshold was put forward in [10], but the diagnostic results were less accurate when the control currents of the actuator changed suddenly. Given that the ripple characteristics of the actuator current are directly correlated with the time constant of electromagnetic coils [29], theoretical analysis and simulation validation of the inherent ripple characteristics have been conducted in [30], [31].…”

A Parametric Solution to the Generalized Bias Linearization Problem

“…This subsequent work has explored various aspects of fault tolerance through generalized bias linearization. Examples include Reference [8], which explored many aspects of potential failures in magnetic bearing systems, including the use of generalized bias linearization provide tolerance of coil or amplifier failures, Reference [9], which examined a range of implementation aspects of this approach, Reference [10], which specifically examined the problem of robust fault detection prior to action, [6] which included finite magnetic permeability and the effect of leakage into the generalized bias linearization formulation, Reference [11], which introduced the math to enable use of reduced controller outputs in generalized bias linearization, and Reference [12], which examined how controller parameters might need to be modified with faults under generalized bias linearization. Experimental results are provided in Reference [13], which documents an early application of generalized fault tolerance to a rotor test rig, in Reference [14], which applied the approach to the design of magnetic bearings for turbo-molecular results, and in Reference [15], which compared theoretical results to physical experiments.…”

Optimization of bias current coefficient in the fault-tolerance of active magnetic bearings based on the redundant structure parameters

“…Because of the requirement of high efficiency in magnetic bearings, it is practically impossible to design some hot standby actuators prepared to replace the failed ones only. Moreover, there is a symmetry constraint on the stator structure [8], the short circuit, break or partial insulation damages in the electromagnetic coils will cause the unexpected EMF, which is defined as the actuator fault [5] and will destroy the original symmetry of the bearing structure, leading to the failure of bearing system and serious impacts [9].…”