Active Magnetic Bearings for High Speed Spindle Design With Nonlinear Time-Frequency Control

2015 ◽  
Author(s):  
Mengke Liu ◽  
C. Steve Suh
Keyword(s):  
High Speed ◽  
Frequency Control ◽  
Air Gap ◽  
Magnetic Bearings ◽  
Lms Algorithm ◽  
Significant Implication ◽  
Active Magnetic Bearings ◽  
Gyroscopic Effect ◽  
Electromagnetic Actuators ◽  
Time Frequency

A novel concept applicable to the control of spindles at high speed is developed by using active magnetic bearings (AMBs) that are non-contact and of low vibration. Though former studies are abundant and demonstrating promising potentials, however, two major issues hamper the broader application of AMBs. The first is the disregard for the gyroscopic effect and geometry coupling that influence the magnitude as well as distribution of the electromagnetic force in AMBs. Not considering the two has a significant implication for the proper control of AMBs. This paper considers the gyroscopic effect and explores the geometry coupling of the electromagnetic actuators to the formulation of a comprehensive nonlinear AMB-rotor model. The model provides the basis for the creation of a novel time-frequency control algorithm whose derivation requires no linearization or mathematical simplification of any kind, thus allowing the model system to retain its true fundamental characteristics. Unlike proportional-integral-derivative (PID) controllers that are dominant in most if not all AMB configurations, the controller developed for the research is inspired by the wavelet-based nonlinear time-frequency control methodology that incorporates the basic notions of online system identification and adaptive control. Due to the fact that dynamic instability is characterized by time-varying frequency and non-stationary spectrum, the control of AMBs needs be executed in the time and frequency-domain concurrently to ensure stability and performance at high speed. Wavelet filter banks and filtered-x least-mean-square (LMS) algorithm are two of the major salient physical features of the controller design, with the former providing concurrent temporal and spectral resolutions needed for identifying the nonlinear state of motion and the latter ensuring the dynamic stability of the AMB-rotor system at extremely high speed. It is shown that the vibration of the rotor is unconditionally controlled by maintaining a mandatory 0.55 mm air gap at 187,500 rpm subject to a tight spatial constraint (tolerance) of the order of 0.1375mm, which is the 25% of the air gap.

Simultaneous Time-Frequency Control of Multi-Dimensional Micro-Milling Instability

2012 ◽  
Author(s):  
Meng-Kun Liu ◽  
Eric B. Halfmann ◽  
C. Steve Suh
Keyword(s):  
Frequency Response ◽  
High Speed ◽  
Frequency Control ◽  
External Perturbation ◽  
Micro Milling ◽  
Time Frequency ◽  
System A ◽  
Control Concept ◽  
The Time Domain ◽  
Tool Damage

A novel control concept is presented for the online control of a high-speed micro-milling model system in the time and frequency domains concurrently. Micro-milling response at high-speed is highly sensitive to machining condition and external perturbation, easily deteriorating from bifurcation to chaos. When losing stability, milling time response is no longer periodic and the frequency response becomes broadband, rendering aberrational tool chatter and probable tool damage. The controller effectively mitigates the nonlinear vibration of the tool in the time domain and at the same time confines the frequency response from expanding and becoming chaotically broadband. The simultaneous time-frequency control is achieved through manipulating wavelet coefficients, thus not limited by the increasing bandwidth of the chaotic system — a fundamental restraint that deprives contemporary controller designs of validity and effectiveness. The feedforward feature of the control concept prevents errors from re-entering the control loop and inadvertently perturbing the sensitive micro-milling system. Because neither closed-form nor linearization is required, the innate, genuine features of the micro-milling response are faithfully retained.

Vibrations monitoring of high speed spindle with active magnetic bearings in presence of defects

2015 ◽  
Vol 49 (2) ◽  
pp. 207-221 ◽  
Author(s):  
Amel Bouaziz ◽  
Slim Bouaziz ◽  
Taissir Hentati ◽  
Jean Yves Cholley ◽  
Mohamed Haddar
Keyword(s):  
High Speed ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings

Nonlinear Calculation of Active Magnetic Bearings Dynamic Magnetic Field by Finite Element Method

2013 ◽  
Vol 392 ◽  
pp. 285-289
Author(s):  
Guo Ping Ding ◽  
Bin Gao
Keyword(s):  
Magnetic Field ◽  
Flux Density ◽  
Eddy Current ◽  
Open Loop ◽  
Air Gap ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Flux Lines ◽  
Source Current ◽  
Dynamic Magnetic Field

Active magnetic bearings open-loop instability makes the features of dynamic magnetic field crucial to the control performance. We presented a nonlinear calculation of AMBs dynamic magnetic field by FEM. Firstly, we constructed a AMBs dynamic field FEM model considering the magnets nonlinear permeability; Secondly, we applied a harmonic current to the coils through 160 load steps and a zero magnetic potential boundary condition; Finally the field was solved and magnetic flux lines, air gap flux density and eddy current density were retrieved and analyzed. Because of the nonlinearity of eddy current, air gap flux density is not standard harmonic and lags behind the source current,and as magnetizing energy equalizes eddy current losses, air gap flux density approaches harmonic.

scholarly journals Control Performance, Stability Conditions, and Bifurcation Analysis of the Twelve-Pole Active Magnetic Bearings System

2021 ◽  
Vol 11 (22) ◽  
pp. 10839
Author(s):  
Sabry M. El-Shourbagy ◽  
Nasser A. Saeed ◽  
Magdi Kamel ◽  
Kamal R. Raslan ◽  
Mohamed K. Aboudaif ◽  
...  
Keyword(s):  
High Speed ◽  
Coupling Effect ◽  
Dimensional Space ◽  
Dominant Role ◽  
Dynamic Stiffness ◽  
Equations Of Motion ◽  
Magnetic Bearings ◽  
Control Parameters ◽  
Active Magnetic Bearings ◽  
Pole System

The active magnetic bearings system plays a vital role in high-speed rotors technology, where many research articles have discussed the nonlinear dynamics of different categories of this system such as the four-pole, six-pole, eight-pole, and sixteen-pole systems. Although the twelve-pole system has many advantages over the eight-pole one (such as a negligible cross-coupling effect, low power consumption, better suspension behaviors, and high dynamic stiffness), the twelve-pole system oscillatory behaviors have not been studied before. Therefore, this article is assigned to explore the effect of the magneto-electro-mechanical nonlinearities on the oscillatory motion of the twelve-pole system controlled via a proportional derivative controller for the first time. The normalized equations of motion that govern the system vibrations are established by means of classical mechanics. Then, the averaging equations are extracted utilizing the asymptotic analysis. The influence of all system parameters on the steady-state oscillation amplitudes is explored. Stability charts in a two-dimensional space are constructed. The stable margin of both the system and control parameters is determined. The obtained investigations reveal that proportional gain plays a dominant role in reshaping the dynamics and motion bifurcation of the twelve-pole systems. In addition, it is found that stability charts of the system can be controlled by simply utilizing both the proportional and derivative gains. Moreover, the numerical simulations showed that the twelve-poles system can exhibit both quasiperiodic and chaotic oscillations besides the periodic motion depending on the control parameters’ magnitude.

scholarly journals Theoretical and Experimental Analysis on the Influence of Rotor Non-Mechanical Errors of the Inductive Transducer in Active Magnetic Bearings

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4376
Author(s):  
Jinpeng Yu ◽  
Yan Zhou ◽  
Ni Mo ◽  
Zhe Sun ◽  
Lei Zhao
Keyword(s):  
Measurement Error ◽  
High Speed ◽  
Eddy Currents ◽  
Excitation Frequency ◽  
Surface Conductivity ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Anisotropic Surface ◽  
Measuring Accuracy ◽  
Measuring Signal

Inductive transducers are widely applied to active magnetic bearings (AMBs). However, when the rotor rotates at a high speed, the rotor defects will affect the measuring signal (the magnetic field generated by transducer coils) and then reduce the transducer measuring accuracy. The rotor in AMBs is assembled with laminations, which will result in rotor non-mechanical errors. In this paper, rotor non-mechanical errors, including the anisotropic internal permeability and anisotropic surface conductivity, and their influence on double-pole variable-gap inductive transducers are explored in depth. The anisotropic internal permeability will affect the transducer measuring accuracy and bring about 1.3 ± 0.1 % measurement error. The anisotropic surface conductivity leads to different eddy currents around the rotor, influences the equivalent reluctance of the magnetic circuit, and then affectsthe transducer measuring accuracy. The experiments prove that rotor non-mechanical errors have a significant influence on transducer measurement accuracy, and the reduction of the transducer excitation frequency can reduce the measurement error and improve the AMB control performance.

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