An Integrated Self-Sensing Approach for Active Magnetic Bearings

Ranft, E.O.; Schoor, George van; Rand, C.P. du

doi:10.23919/saiee.2011.8531907

Cited by 3 publications

(3 citation statements)

References 8 publications

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“…The flow diagram of the TSM implemented in simulation is shown in Figure 6 . Details regarding the individual TSM modules are presented in [ 16 , 17 ].…”

Section: Reference Modelsmentioning

confidence: 99%

A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach

Niemann

Schoor

Rand

2013

Sensors

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Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance thereof. This paper presents the direct current measurement (DCM) approach for self-sensing AMBs, denoting the direct measurement of the current ripple component. In AMB systems, switching power amplifiers (PAs) modulate the rotor position information onto the current waveform. Demodulation self-sensing techniques then use bandpass and lowpass filters to estimate the rotor position from the voltage and current signals. However, the additional phase-shift introduced by these filters results in lower stability margins. The DCM approach utilizes a novel PA switching method that directly measures the current ripple to obtain duty-cycle invariant position estimates. Demodulation filters are largely excluded to minimize additional phase-shift in the position estimates. Basic functionality and performance of the proposed self-sensing approach are demonstrated via a transient simulation model as well as a high current (10 A) experimental system. A digital implementation of amplitude modulation self-sensing serves as a comparative estimator.

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“…The flow diagram of the TSM implemented in simulation is shown in Figure 6 . Details regarding the individual TSM modules are presented in [ 16 , 17 ].…”

Section: Reference Modelsmentioning

confidence: 99%

A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach

Niemann

Schoor

Rand

2013

Sensors

View full text Add to dashboard Cite

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“…Two currently prominent approaches to determining the rotor position are self-sensing and dedicated non-contact sensors. In self sensing, the rotor position is approximated using the change in actuator inductance, caused by rotor movement [1,2]. Dedicated position sensor technologies used in AMBs, include; optical, inductive, eddy current, Hall-effect and capacitive types [3].…”

Section: Introductionmentioning

confidence: 99%

“…As explained above, the target should be electrically conductive for an eddy current sensing principle to be used. The penetration depth (δ) of the magnetic fields can be calculated using (1) where f is the frequency of the excitation current, µ is the permeability and σ is the conductivity of the target. Aluminium is commonly used as target for eddy current sensors and has a calculated penetration depth of 58.5 µm if a 2 MHz signal is used.…”

Section: Introductionmentioning

confidence: 99%

Design and Optimisation of a PCB Eddy Current Displacement Sensor

2017

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Position sensing is one of the crucial parts of many systems, specifically in an active magnetic bearing. The position is used to control the magnetic forces within an active magnetic bearing to keep a rotor levitated. Sensors used in these systems must be very sensitive and are usually very expensive. In this paper a low cost printed circuit board position sensor is analysed. The sensor uses an excitation coil to establish a magnetic field. Four sensing coils are then used to measure the influence a conducting target has on the magnetic field to enable position sensing. The sensor's magnetic operation is analysed using finite element methods and very good correlation is found with measured results. The effects of the target material and the number of PCB layers are analysed. It is shown that a two layer sensor can produce acceptable sensitivity and linearity.

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