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System modeling and robust control of an AMB spindle: part I modeling and validation for robust control

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Abstract

This paper discusses details of modeling and robust control of an AMB (active magnetic bearing) spindle, and part I presents a modeling and validation process of the AMB spindle. There are many components in AMB spindle : electromagnetic actuator, sensor, rotor, power amplifier and digital controller. If each component is carefully modeled and evaluated, the components have tight structured uncertainty bounds and achievable performance of the system increases. However, since some unknown dynamics may exist and the augmented plant could show some discrepancy with the real plant, the validation of the augmented plant is needed through measuring overall frequency responses of the actual plant. In addition, it is necessary to combine several components and identify them with a reduced order model. First, all components of the AMB spindle are carefully modeled and identified based on experimental data, which also render valuable information in quantifying structured uncertainties. Since sensors, power amplifiers and discretization dynamics can be considered as time delay components, such dynamics are combined and identified with a reduced order. Then, frequency responses of the open-loop plant are measured through closed-loop experiments to validate the augmented plant. The whole modeling process gives an accurate nominal model of a low order for the robust control design.

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Abbreviations

A :

Area

B :

Bandwidth of detector

C :

Capacitance for current impulse

C f :

Feedback capacitor of detector

C x :

Unknown capacitance

C nu×1 :

nu×1 dimension complex vector

f :

Frequency

G :

Transfer function of the plant

go :

Nominal air gap of electromagnetic actuator

i :

Current

io :

Bias current of electromagnetic actuator

N c :

Number of coil turns

R c :

Coil resistance

R f :

Resistor for current measurement

R fet :

Turn on resistance of FET

T :

Sampling time

U :

Frequency response matrix of controller output

V c :

Charge voltage of capacitance detecting circuit

V o :

Output voltage of capacitance detecting circuit

V s :

DC link voltage for FET

Y :

Frequency response matrix of controller input

Δ:

Computation time

μ o :

Permeability

ω :

Frequency

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Authors and Affiliations

  1. Department of Mechanical & Aerospace Engineering, University of Virginia, 122 Engineer’s way, 22904-4746, Charlottesville, Virginia, USA

    Hyeong-Joon Ahn

  2. School of Mechanical & Aerospace Engineering, Seoul National University, 151-745, Korea

    Dong-Chul Han

Authors
  1. Hyeong-Joon Ahn
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  2. Dong-Chul Han
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Correspondence to Dong-Chul Han.

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Ahn, HJ., Han, DC. System modeling and robust control of an AMB spindle: part I modeling and validation for robust control. KSME International Journal 17, 1844–1854 (2003). https://doi.org/10.1007/BF02982423

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  • DOI: https://doi.org/10.1007/BF02982423

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