Compensation of nonlinearities in active magnetic bearings with variable force bias for zero- and reduced-bias operation

̧bski, Rafał Piotr Jastrze; Pollanen, R.

doi:10.1016/j.mechatronics.2009.01.013

Cited by 23 publications

(19 citation statements)

References 9 publications

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“…However, the high bias results in increased losses, a high bearing stiffness, and increased noise in position measurements, because of the high stiffness and current signal levels. To compensate for the influence of the rotor position and the bearing current on the inner-loop controllers and to keep their dynamics more linear, a variable feedback gain, K c (x, i), could be considered [8]. The static force field nonlinearity as a function of currents and position can also be compensated for, for example, by using an inverse nonlinearity method [8], a nonlinear force model in the observer [10], or an extended Kalman filter (EKF) [18].…”

Section: Outer Position Control For Current-controlled Ambmentioning

confidence: 99%

“…To compensate for the influence of the rotor position and the bearing current on the inner-loop controllers and to keep their dynamics more linear, a variable feedback gain, K c (x, i), could be considered [8]. The static force field nonlinearity as a function of currents and position can also be compensated for, for example, by using an inverse nonlinearity method [8], a nonlinear force model in the observer [10], or an extended Kalman filter (EKF) [18]. However, the compensated control systems, as in [8,10], are sensitive to modeling errors, and they are difficult to implement without an accurate identification of the nonlinear plant models.…”

Section: Outer Position Control For Current-controlled Ambmentioning

confidence: 99%

“…The static force field nonlinearity as a function of currents and position can also be compensated for, for example, by using an inverse nonlinearity method [8], a nonlinear force model in the observer [10], or an extended Kalman filter (EKF) [18]. However, the compensated control systems, as in [8,10], are sensitive to modeling errors, and they are difficult to implement without an accurate identification of the nonlinear plant models. The inverse nonlinearity compensation assumes that there are no actuator dynamics between the compensated control and the actual control signal and no limitation on how fast the control signal can be produced.…”

Section: Outer Position Control For Current-controlled Ambmentioning

confidence: 99%

“…For testing the flux-based zero-bias control, a Linear-quadratic-Gaussian (LQG) outer position controller is synthesized [8,17]. The weighting matrices for both centralized LQG (flux and current) controllers have been optimized to achieve maximum bandwidth and minimum sensitivity peaks.…”

Section: Comparison Of Current-and Flux-controlled Amb Systemsmentioning

confidence: 99%

“…To compensate for the resulting force nonlinearities, such methods, as, for example, inverse-nonlinearity-based compensation [8] and observer-based force linearization, have been proposed [9,10]. In [9], a 1 DOF axial control has been presented with a model-based flux observer for the compensation of eddy currents and other magnetic force nonlinearities.…”

Section: Introductionmentioning

confidence: 99%

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Cascaded Position-Flux Controller for an AMB System Operating at Zero Bias

et al. 2014

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The paper reports on the implementation and the design of a controller for a fuel cell blower (FCB) with active magnetic bearings (AMBs). The cascaded position-fluxcentralized controller is comprised of a centralized position control loop and an inner flux control loop. The last one is based on state estimation without explicit flux measurements. As the position control is not dependent on the magnetic field nonlinearities, such a control structure enables operation under a zero bias. The practical working implementation of a flux control for the industrial levitated rotor is shown for the first time. The flux control gives better results than current control for both normal and zero bias operation. The system is analyzed fully, combining rotor dynamics and power amplifier analyses simultaneously. The importance of using the coil voltage in addition to current and practical treatment of the flux control is revealed. The centralized position-flux controller is compared with a state-of-the-art cascaded position-current control, which has inner current control loops. The proposed control solution with a zero bias can achieve a dynamic performance comparable that of a controller with the classical bias current.

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Section: Outer Position Control For Current-controlled Ambmentioning

confidence: 99%

Section: Outer Position Control For Current-controlled Ambmentioning

confidence: 99%

Section: Outer Position Control For Current-controlled Ambmentioning

confidence: 99%

Section: Comparison Of Current-and Flux-controlled Amb Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cascaded Position-Flux Controller for an AMB System Operating at Zero Bias

et al. 2014

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Controller parameterization and bias current reduction of active magnetic bearings for a flexible and gyroscopic spindle

2022

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A magnetically levitated spindle was designed for fatigue testing of cylinders made of fiber reinforced plastic. In these fatigue tests, the speed of the cylinders is varied cyclically between 15,000 and 30,000 rpm until their mechanical failure occurs. Several eigenfrequencies have to be passed to reach the operational speed range. During long-term operation, the rotor of the spindle is prone to overheating due to various losses. One way of reducing the rotor temperature is to decrease the bias current of the radial active magnetic bearings. Since the bias current influences the dynamic behavior of the system, the control of the bearings has to be adapted as well. This article describes a controller design for the system with different bias currents to determine the smallest usable bias current. A detailed model of the plant is developed, which is then used to optimize the parameters of the utilized controller with a predefined structure using the weighted  ∞ norm as the objective function. Since the rotor is highly gyroscopic, its eigenfrequencies change with the rotational speed. To ensure that the system meets certain robustness criteria at all rotational speeds, the parameters of the controller are simultaneously optimized for the plant model at different speeds. This approach leads to a controller which can be used in the entire speed range without the need for gain scheduling. The functionality of the controller and the influence of the bias current on the rotor temperature are investigated through measurements.

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