Model-Based Switching-Crack Identification in a Jeffcott Rotor With an Offset Disk Integrated With an Active Magnetic Bearing

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Sandeep Singh ◽  
Rajiv Tiwari
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Vibration Signal ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Crack Identification ◽  
Identification Algorithm ◽  
Full Spectrum ◽  
Jeffcott Rotor ◽  
Domain Transformation

Vibration characteristics of a cracked Jeffcott rotor with an offset disk under the action of an active magnetic bearing (AMB), implemented to improve the radial positioning of the rotor, has been studied. Presence of the AMB suppresses the vibration induced due to the crack and unbalance; identification of the crack could be made by utilizing the vibration signal in conjunction with the controller current of the AMB. A four degrees-of-freedom (DOF) cracked rotor is modeled considering the gyroscopic effect due to the offset disk and a switching crack excitation function (SCEF) to introduce the breathing of crack. The dynamic condensation is applied to eliminate rotational displacements, which would pose practical difficulty in accurate measurement, from the system equations of motion (EOM) to develop an identification algorithm. Frequency domain transformation of the EOM is made with the help of the full spectrum analysis. An algorithm developed with the purpose of crack identification in the form of additive crack stiffness estimates the viscous damping, disk unbalance, and AMB constants as well. The algorithm has been tested for the measurement noise (in the displacement and the current) and bias errors in system parameters, and found to be robust.

Model-Based Crack Identification Using Full-Spectrum

2013 ◽  
Author(s):  
Shravankumar Chandrasekaran ◽  
Rajiv Tiwari
Keyword(s):  
Equations Of Motion ◽  
Crack Identification ◽  
Force Model ◽  
Identification Algorithm ◽  
Full Spectrum ◽  
Rotor Systems ◽  
Model Based ◽  
Fault Parameters ◽  
Harmonic Components ◽  
Rotor Model

This paper illustrates the application of full-spectrum technique for model-based identification of the crack and unbalance multi-fault parameters in cracked rotor systems. The rotor model chosen is a Laval rotor with disc unbalance and transverse surface crack. The crack force model is a switching crack, which has harmonic components exciting the rotor both in the same and reverse directions of the rotor spin. Development of identification algorithm uses linearized equations of motion in frequency domain. Full-spectrum obtains the complex Fourier coefficients of the force as well as the response. Further usage of these coefficients in the identification algorithm estimates the viscous damping, disc eccentricity, and additive crack stiffness as fault parameters. The accuracy of estimates increases on considering measurements at multiple spin speeds. The algorithm tests reasonably robust for various levels of measurement noise and bias errors in system parameters.

Some Nonlinear Effects of Magnetic Bearings

1999 ◽  
Author(s):  
Norbert Steinschaden ◽  
Helmut Springer
Keyword(s):  
Equations Of Motion ◽  
Period Doubling ◽  
Path Following ◽  
Nonlinear Effects ◽  
Magnetic Bearing ◽  
Operating Conditions ◽  
Active Magnetic Bearing ◽  
Nonlinear Phenomena ◽  
Amb System ◽  
Large Rotor

Abstract In order to get a better understanding of the dynamics of active magnetic bearing (AMB) systems under extreme operating conditions a simple, nonlinear model for a radial AMB system is investigated. Instead of the common way of linearizing the magnetic forces at the center position of the rotor with respect to rotor displacement and coil current, the fully nonlinear force to displacement and the force to current characteristics are used. The AMB system is excited by unbalance forces of the rotor. Especially for the case of large rotor eccentricities, causing large rotor displacements, the behaviour of the system is discussed. A path-following analysis of the equations of motion shows that for some combinations of parameters well-known nonlinear phenomena may occur, as, for example, symmetry breaking, period doubling and even regions of global instability can be observed.

Modelling, Analysis and Identification of the Parallel and Angular Misalignments in a Coupled Rotor-Bearing-AMB System

2020 ◽  
Author(s):  
Siva Srinivas R ◽  
Rajiv Tiwari ◽  
Ch. Kanna Babu
Keyword(s):  
Mathematical Model ◽  
Vibration Suppression ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Identification Algorithm ◽  
Rotor Systems ◽  
Force Moment ◽  
Coupling Force ◽  
Auxiliary Bearing ◽  
Amb System

Abstract The standard techniques used to detect the misalignment in rotor systems are loopy orbits, multiple harmonics with predominant 2X component, and high axial vibration. This paper develops a new approach for the identification of misalignment in coupled rotor systems modelled using 2-node Timoshenko beam finite elements. The coupling connecting the turbine and generator rotor systems is modelled by a stiffness matrix, which has both static and additive components. While the magnitude of static stiffness component is fixed during operation, the time varying additive stiffness component displays a multi-harmonic behaviour and exists only in the presence of misalignment. To numerically simulate the multi-harmonic nature coupling force/moment as observed in experiments, a pulse wave is used as the steering function in the mathematical model of the additive coupling stiffness (ACS). The representative TG system has two-rotor systems, each having two discs and supported on two flexible bearings - connected by coupling. An active magnetic bearing (AMB) is used as an auxiliary bearing on each rotor for the purposes of vibration suppression and fault identification. The formulation of mathematical model is followed by the development of an identification algorithm based on the model developed, which is an inverse problem. Least-squares linear regression technique is used to identify the unbalances, bearing dynamic parameters, AMB constants and importantly the coupling static and additive stiffness coefficients. The sensitivity of the identification algorithm to signal noise and bias errors in modelling parameters have been tested. The novelty of paper is the representation and identification of misalignment using the ACS matrix coefficients, which are direct indicators of both type and severity of the misalignment.

Design of a Highly Integrated Active Magnetic Bearing With Six Coupled Actuators for High Precision Rotation Applications

1999 ◽  
Author(s):  
M. Kümmerle ◽  
B. Aeschlimann ◽  
J. Zoethout ◽  
T. Belfroid ◽  
R. Vuillemin ◽  
...  
Keyword(s):  
High Precision ◽  
Pid Controller ◽  
Degrees Of Freedom ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
The Other ◽  
Axial Forces ◽  
Functional Prototype ◽  
The One ◽  
Contact Free

Abstract This paper presents the design and the implementation of a contact free Active Magnetic Bearing (AMB) for high precision rotation applications. For controlling five Degrees of Freedom (DOF) of the rotor six coupled reluctance force actuators (creating radial and axial forces at the same time) are used. A method for designing the actuators in order to meet the specifications is described. Two different controller schemes using different sensor configurations have been implemented on a functional prototype: On the one hand a conventional decentralized PID controller, on the other hand a more centralized structure.

scholarly journals Bearingless PM-synchronous machine with axial active magnetic bearing fed by zero-sequence current

2021 ◽  
Author(s):  
Daniel Dietz ◽  
Andreas Binder
Keyword(s):  
Degrees Of Freedom ◽  
Pulse Width Modulation ◽  
Position Control ◽  
Magnetic Bearing ◽  
Magnetic Suspension ◽  
Active Magnetic Bearing ◽  
Axial Position ◽  
Synchronous Motors ◽  
Bearingless Motor ◽  
Zero Sequence

AbstractA novel inverter supply for bearingless PM-synchronous motors with magnetic suspension allows the reduction of the number of power electronic switches. Hence, all six motional degrees of freedom of bearingless AC machines may be controlled via 3-phase inverter topologies. In this paper, instead of a bearingless motor consisting of two half motors, one bearingless motor with an additional radial active magnetic bearing is treated. Bearingless machines with cylindrical rotors in contrast to double cone rotors generate – apart from the electromagnetic torque – only radial magnetic forces. Hence, an axial magnetic bearing is used.For this bearing, there is no need for a feeding converter bridge as the bearing coil is fed by the zero-sequence current of the feeding 3-phase inverters. The bearing coil is placed between the two star points of the motor winding. The zero-sequence current amplitude is adjusted by the 3-phase inverters via pulse width modulation. The feasibility of this kind of axial position control is proven by simulation as well as with an experiment with a 1 kW prototype motor up to 60000 min−1.

On the Robust Stability of Segmented Driveshafts with Active Magnetic Bearing Control

2005 ◽  
Vol 11 (3) ◽  
pp. 317-329 ◽  
Author(s):  
Hans A. Desmidt ◽  
K. W. Wang ◽  
Edward C. Smith ◽  
Andrew J. Provenza
Keyword(s):  
Robust Stability ◽  
Closed Loop ◽  
Equations Of Motion ◽  
Stability Index ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Internal Damping ◽  
Shaft Speed ◽  
Load Torque ◽  
Loop Stability

Many researchers and engineers have employed active control techniques, such as active magnetic bearings (AMBs), to suppress imbalance vibration in various subcritical and supercritical speed rotors dynamic applications. One issue that has not yet been addressed in previous AMB driveline control studies is the effect of non-constant velocity (NCV) flexible couplings, such as U-joint or disk-type couplings, present in many segmented drivelines. The NCV effects introduce periodic parametric and forcing terms into the equations of motion that are functions of shaft speed, driveline misalignment, and load-torque, resulting in a linear periodically time-varying system. Previous research has found that both internal damping and NCV terms greatly impact stability; thus, they must be accounted for in the control law design in order to ensure closed-loop stability of any AMB-NCV-driveline system. In this paper, numerical Floquet theory is used to explore the closed-loop stability of a flexible segmented NCV-driveline supported by AMBs with a proportional-derivative (PD) type controller. To ensure robust stability with respect to internal damping and NCV effects, the robust P and D gains and AMB locations are selected based on maximizing a stability index over a range of shaft speeds, driveline misalignments, and load-torques. It is found that maximum robustness occurs within a finite range of P and D gains for several different AMB locations. Finally, the range of robustly stabilizing P gains versus the shaft speed is examined for several misalignment and load-torque bounds.

Circularity Error Analysis of Axial Displacement Sensor Detecting Surface for Active Magnetic Bearings of 10MW High Temperature Gas-Cooled Reactor (HTR-10GT)

2013 ◽  
Author(s):  
Jingjing Zhao ◽  
Yan Zhou ◽  
Zhe Sun ◽  
Suyuan Yu
Keyword(s):  
High Temperature ◽  
Degrees Of Freedom ◽  
Magnetic Bearing ◽  
Axial Displacement ◽  
Working Environment ◽  
Active Magnetic Bearing ◽  
Displacement Sensor ◽  
Displacement Sensors ◽  
Circularity Error ◽  
High Temperature Gas

The 10MW high temperature gas-cooled test module reactor (HTR-10GT) with the core made of spherical fuel elements was designed and constructed by the Institute of Nuclear and New Energy Technology of Tsinghua University in China. In the HTR-10GT, turbo-compressor and generator rotors are connected by a flexible coupling and a decelerator. The rotors, restricted by actual instruments and working environment, must be supported without any contact and lubrication. Active magnetic bearing (AMB), is the best way to suspend and stabilize the position of rotors of HTR-10GT. In AMB system, the displacement sensors are designed for converting measured physical value into proportional electric signals and transferring it into the control and monitoring system. The characteristics and influence of circularity error of the axial displacement sensor detecting surface is analyzed according to AMB with five degrees of freedom. In order to reduce the circularity error of the magnetic bearing system, the sensor detecting surface requires high-precision machining.

scholarly journals Optimal control for hybrid magnetically suspended flywheel rotor based on state feedback exact linearization model

2020 ◽  
Vol 103 (3) ◽  
pp. 003685042095138
Author(s):  
Tong Wen ◽  
Biao Xiang ◽  
Shilei Zhang
Keyword(s):  
Optimal Control ◽  
Nonlinear Dynamic ◽  
Degrees Of Freedom ◽  
State Feedback ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Exact Linearization ◽  
Dynamic Function ◽  
The Stability ◽  
Flywheel Rotor

For a hybrid magnetically suspended flywheel (MSFW) rotor suspended by permanent magnet biased active magnetic bearing (AMB) and passive magnetic bearing (PMB), the dynamic functions are nonlinear and coupling among different degrees of freedom (DOFs). In this article, the nonlinear dynamic functions in two controllable DOFs of the hybrid MSFW rotor are developed based on the equivalent magnetic circuit, and then the nonlinear dynamic function is linearized by using the state feedback exact linearization (SFEL) in order to minimize the coupling in two controllable DOFs. Furthermore, an optimal control based on the SFEL model is designed to reduce displacement runout and coupling among two controllable DOFs of the hybrid MSFW rotor at the rated speed. Finally, the simulation and experimental results validate the effectiveness of the optimal control based on SFEL model, and the stability of the hybrid MSFW rotor with an impulse-type disturbance is improved.

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