Design, fabrication and control of a novel linear magnetic actuator for a controllable squeeze film damper

, Design, Fabrication and Control of a Novel Linear Magnetic Actuator for a Controllable Squeeze Film Damper Truong Quoc Thanh... , Design, Fabrication and Control of a Novel Linear Ma

,

Design, Fabrication and Control of a Novel Linear Magnetic Actuator for a Controllable Squeeze Film

Damper

Truong Quoc Thanh

,

Design, Fabrication and Control of a Novel Linear Magnetic Actuator for a Controllable Squeeze Film

Damper

Truong Quoc Thanh

Linear Magnetic Actuator Applying to a

Controllable Squeeze Film Damper

Truong Quoc Thanh

A thesis submitted to the School of Mechanical and Automotive Engineering in fulfillment of the thesis requirements for the degree of Doctor of Philosophy in

the Graduate School, University of Ulsan

November 2008

Acknowledgments

First and foremost, I would like to express my deep gratitude to my supervisor,

Prof Dr Ahn Kyoung Kwan, for his introduction and advisement in the duration of

my studying at Ulsan University It would not be overstatement to say that without his

much guidance and support, this thesis could not have been completed

I am also honored to have Prof Yang, S.Y., Prof Lee, B.R., Prof Ha, C.G., and

Prof Park, J.H whose inspiration, support and perseverance made this dissertation

become possible in my committee I would like thank to them for kindly joining the

advisory board and providing many insightful suggestions and comments through my

research

My thanks also go to Brain Korea 21 (BK21) Project and the Korea Ministry of

Education-Human Resources Development for their financial support to promote our

research achievements I would like to thank Thinh, N.V., Hoang, N.M., Long N.P.,

Han, P.N and Trang, D.T.T for their encouragement and festivity which helped

enlighten my hard working days in Korea Especially, I need to express my gratitude

to V.D Nhat and N.V Giang for their unconditional helps

I would like to acknowledge all members of Fluid Power Control & Machine

Intelligence Lab, especially Anh, H.P., Yoon, Y.I., Truong, Q.D., Nam T.H and

Mechanical Workshop Staffs of University of Ulsan Their continuous support has

partly facilitated my work and kept me moving forward to my goal Thanks to all of

Furthermore, I would like to take this opportunity to express my sincere

appreciation to my wife and my daughter for their love and comfort through all my

endeavors Thanks also to my mothers, sisters and brother who always fulfill my life

with happiness and inspiration

Last but not least, my greatest thanks must be sent to my dead father, who gave

great sacrifices to me for my further education up to now

It is always impossible to specifically name everyone who has facilitated the

completion of this dissertation, and I also give my thanks to all of you!

University of Ulsan, Ulsan, Korea

November 28, 2008

Truong Quoc Thanh

Table of contents

Acknowledgments i

Table of contents iii

List of figures v

List of tables viii

Abstract ix

Nomenclatures xi

Chapter 1 Introduction 1

1.1 Motivation for this research 1

1.2 Literature and survey 3

1.2.1 An overview of Linear Magnetic Actuator 3

1.2.2 A Survey Squeeze Film Damper 9

1.3 Aim of this thesis 20

1.4 Layout of thesis 21

Chapter 2 Novel Linear Magnetic Actuator 23

2.1 Principal design of Novel LMA 23

2.2 Mechanical configuration of the LMA for the SFD 26

2.3 Improved formula of the electro-magnetic force 28

2.3.1 The general magnetic force 28

2.3.2 An improved electromagnetic force formula 31

2.4 Design of the electric circuit for controlling the LMA 32

2.4.1 Conspectus of the control method for the magnetic actuator 32

Chapter 3 Propositional and Design of Controllable Squeeze Film Damper 38

3.1 Parameter effect on the squeeze film damper 38

3.2 Mathematical model of Controllable Squeeze film damper 39

3.3 Mechanical design and assembly 48

Chapter 4 Experimental results of Novel Linear Magnetic Actuator 52

4.1 Characteristic of the electromagnetic force of the LMA 52

4.2 Position control of the LMA 62

4.2.1 Structure of a self-tuning fuzzy PID controller 63

4.2.2 Fuzzy-PID design 65

4.3 Experimental results 67

Chapter 5 Experiment of Squeeze Film Damper using LMA 71

5.1 Test-rig and primary parameters 71

5.2 Experimental results 74

5.2.1 Steady state responses 74

5.2.2 Circular Orbits 76

5.2.3 Application of fuzzy PID controller to the CSFD 79

Chapter 6 Conclusions and future works 84

6.1 Conclusions 84

6.2 Future works 86

References 87

Publications and Conference papers 95

International Journals 95

International Conference papers 96

Appendix : CAD’s drawing 98

List of figures

Figure 1-1 Configuration of the moving-coil actuator .3

Figure 1-2 Positioning magnetic head using on a disc memory system .3

Figure 1-3 Configuration of the moving-iron actuator 4

Figure 1-4 Configuration of moving-magnet actuator .6

Figure 1-5 The mechanical construction of EMV 6

Figure 1-6 The conformation of EMA 8

Figure 1-7 Tubular brushless permanent magnet linear motor 9

Figure 1-8 The ideal model of squeeze film damper 10

Figure 1-9 Different configurations of conventional fluid damper 12

Figure 1-10 Different configurations of ER damper 14

Figure 1-11 Different configurations of MR damper 18

Figure 2-1 Demonstrating the equivalence of a coil and a magnet 23

Figure 2-2 The assembly and principle of LMA 24

Figure 2-3 Model of the novel LMA 26

Figure 2-4 The electromagnetic coil (U-shape) 27

Figure 2-5 Illustration of the magnetic poles of U-shape 30

Figure 2-6 The diagram of the control circuit of magnetic actuators 33

Figure 2-7 The electrical circuit control using by IGPT 34

Figure 2-8 The real control electrical circuit use the IGPT 36

Figure 2-9 Schematic diagram of the LMA controller 36

Figure 3-1 Controllable squeeze-film damper model 39

Figure 3-2 Dimensionless pressure distribution versus clearance (at ε=0.5) 46

Figure 3-3 Dimensionless pressure distribution versus dimensionless quantity (at clearance cχ=0.15 mm) 46

Figure 3-4 Squeeze film damper dimensionless radial force versus clearance (cχ) 47

Figure 3-5 Squeeze film damper dimensionless tangential force versus clearance (cχ) 48

Figure 3-6 CSFD assembly sketch: (19.Damper housing; 20.Outer damper ring; 21.Inner damper ring) 49

Figure 3-7 Realized components of CSFD 50

Figure 4-1 Test-rig used to measure the magnetic force 52

Figure 4-2 Experimental magnetic force caused by permanent magnets without applied current 55

Figure 4-3 Experimental total magnetic force relative to applied current and position 55

Figure 4-4 Electromagnetic force corresponding to the applied current 56

Figure 4-5 Electromagnetic force cause the movement in right direction 58

Figure 4-6 The experimental coefficient ~ ( ) k I with the interpolative cubic curve 60

Figure 4-7 The magnetic force in 3-D plot 61

Figure 4-8 Structure of self-tuning PID controller 64

Figure 4-9 Structure of the fuzzy inference block 64

Figure 4-10 Fuzzy control rule of K’p and K’i 66

Figure 4-11 Experimental apparatus 68

Figure 4-12 System response with respect to sine reference input 68

Figure 4-13 Steady state error respect to sine reference input 69

Figure 4-14 The changes of Kp and Ki of self-tuning controller 70

Figure 5-1 The schematic experiment of the rotor system 71

Figure 5-2 The test-rig of the rotor system 73

Figure 5-3 Steady state response of rotor at position 74

Figure 5-4 Steady state response of rotor at position 2 75

Figure 5-5 Orbits versus the clearance of the SFD at 3200 rpm 77

Figure 5-6 Orbits versus the clearance of the SFD at 4000 rpm 78

Figure 5-7 RAM’s reference when the rotor run-up 79

Figure 5-8 Control the clearance of SFD (as the rotor speed reach 3450 rpm) 80

Figure 5-9 Controlling amplitude (X1,Y1) vs rotational speed 81

Figure 5-10 Controlling amplitude (X2,Y2) vs rotational speed 82

List of tables

Table 1-1 Comparison of fluid types applied on SFD 19

Table 3-1 The principal parameters of the LMA and the SFD 51

Table 3-2 Configuration data of a flexible rotor system 51

Table 4-1 Experimental value of Loadcell’s force 54

Table 4-2 Experimental value of Electro-magnetic force 57

Table 4-3 The coefficients of the model 60

Table 4-4 The coefficients of interpolated curves 60

Table 4-5 Rule table for Fuzzy control 66

Abstract

Design, Fabrication and Control of a Novel Linear Magnetic Actuator

Applying to a Controllable Squeeze Film Damper

Truong Quoc Thanh (Under the direction of Prof Dr Kyoung Kwan Ahn) Department of Mechanical and Automotive Engineering

University of Ulsan Ulsan, Korea

In this paper, a novel Linear Magnetic Actuator (LMA) and a Controllable

Squeeze film damper (CSFD) were proposed, designed, and fabricated The design of

the LMA was compatible with the proposed CSFD The experimental apparatus for

both positioning control of LMA and rotor-dynamics was developed and investigated

The general force’s formula was proposed by assuming that the dependence of

magnetic force between two charges is proportional to 1/r2 to determine the competence of the actuator’s force Our research develops a novel LMA to move the

ODR of the CSFD Experimental results illustrate the concept of the electromagnetic

effect as well as the interaction force between the electromagnet and permanent

magnet Subsequently, an advanced control algorithm is applied to exactly control the

position of LMA to prove its effectiveness and reliability in real applications

In addition, this literature approached the rotor-dynamic responses by

experiment It has been known, the problem of vibration in rotor dynamics is

Nevertheless, the damping of fluid film is effectively varied with the rotational speed

and the radial clearance of fluid film; that means the damping is low or high respected

to the clearance small or big High-speed rotor systems run-up or coast down

traversing critical speeds or working at unstable region, it will make excessive

vibrations of the rotor shaft The novel LMA was used to control the position of the

outer damper ring of the damper to vary the clearance/film thickness of the damper

leading to change the damping fluid forces The obtained experimental results with

variant clearance of the damper described the effectiveness for attenuating the rotor’s

vibration The damper had the best control effect to minimize the vibration within the

range of operating speed by on-off control method

Nomenclatures

c0 = original radial clearance at χ = 0, c0 = 0.05 mm

εχ = eccentricity ratio (at position χ of outer damper ring), e/cχ

Chapter 1 Introduction

1.1 Motivation for this research

Nowadays, industrial actuator brand was extremely and widely developed The

LMA is among of those Although, the LMA has just only been considered and

studied since the 1960s, but it proved the advantages, reliabilities and flexibilities in

the real applications Specifically, there are many researches and numerous papers

have been published on this subject in the recent years [1-27] Many innovated

constructions of the magnetic actuator were developed, investigated and applied A

LMA comprising a pair of stator windings arranged to carry currents providing

magnetic fields of opposed polarity The direction of magnetic flux is arranged as a

line substantially perpendicular to the directions of current flow in the windings With

a permanent magnet mounted on another actuator’s part and having opposite magnetic

poles with a predetermined spacing, the magnetic effect reacts between

electro-magnet and permanent electro-magnet leading to the motion of actuators Three basic

configurations of magnetic actuators are coil, iron and

moving-magnet which are used to classify the moving-magnetic actuators

In rotordynamic fields, the requirement of stability and improving working of

rotor systems is needed The most commonly recurring problems in rotor-dynamics

are how to reduce the excessive steady state synchronous vibration level and

requirement, i.e reducing imbalance mass, moving the operating speed out of critical

speed, and introducing external damping to limit peak amplitudes at traversed critical

speed The Squeeze Film Damper (SFD) was one of choices for high speed rotor

systems Many researchers [28-44] concentrated on the effect of mechanical factors

and damping coefficients of the conventional fluid damper for improving the working

stability of rotor-dynamics Such as seal location, feeding groove size and position,

fluid inertia effect, clearance of thin film, modifying damper configurations, and etc

The past studies in squeeze film damper had proved practical, effective and reliable

more than ball/journal bearing in high-speed rotor systems Beside, nowadays, based

on the invention of a Magneto Reheological (MR) fluid and Electro Rheolgical (ER)

fluid, which is called as a functional fluid, many researchers [45-62] was applied this

fluid into SFD The functional fluid has received increasing interest for use with

dampers and particularly with SFDs The ER and MR fluids react to electrical and

magnetic fields, respectively, undergoing reversible changes in their mechanical

characteristics, i.e viscosity, and stiffness

Nevertheless, contrary to expectations, since the ER and MR fluid have

generally consisted of micro-sized solid particles in suitable base oil, so it causes the

restrictions of rotor-machinery in real application

From above facts, this study was improved and investigated a novel LMA which

was appropriately applied to Controllable Squeeze Film Damper, which was used with

the conventional fluid The principle of the novel LMA was developed, the

mathematic model of magnetic force was proposed to investigate the electro-magnetic

force A CSFD was proposed, designed and fabricated Subsequently, the experiments

considering for both of the positioning control of novel LMA and the rotor-dynamics

behaviour of the rotor system

1.2 Literature and survey

1.2.1 An overview of Linear Magnetic Actuator

(a) Conventional moving actuator (b) Flux focusing actuator

Figure 1-1 Configuration of the moving-coil actuators

Figure 1-2 Positioning magnetic head using on a disc memory system

The moving-coil actuators (MCAs) are based on the Laplace (or Lorentz) force,

which is strictly proportional to the applied current A coil is placed into a magnetic

field perpendicular to the coil winding Applying a current into the coil produces a

magnetic force to coil winding along the third direction They have no blocking force

at rest Fig 1-1 shows schematically the configuration of the actuator To improve the

magnetic effect leading to an increase of electromagnetic force, thereby the permanent

magnets are arranged as shown in Fig 1-1(b)

Bleiman and co-workers [15] proposed a type of MCA, which is applied to the

magnetic head of memory disc system The mechanical model was depicted in Fig

1-2 This invention can improve the precisely located position, and more particularly

increase the motive force of the actuator Furthermore, the MCA was investigated by

Brende et al [16] This actuator is applied to rotating data recording device The

structure included a continuous, cylindrical permanent magnet with an annular

reluctance gap in outer core can provide symmetrical distribution of the permanent

magnetic flux

Figure 1-3 Configuration of the moving-iron actuator

The Moving Iron Actuators (MIAs) are more generally called electro-magnets

They use the magnetic attraction force that exists between two soft magnetic parts in

presence of a magnetic field This force is due to a minimization of the system

magnetic reluctance It is generally much higher than Laplace force used in MCAs In

principle, the magnetic force is intrinsically quadratic meaning that only attraction

forces can be produced To get it back, a return spring is added, leading to one fixed

position at rest The MIAs generally are a type of actuators which is not able to

perform control functions It is used in accelerating/breaking device, for fast

positioning, along the stroke and etc Fig 1-3 describes the configuration of the MIA

Bohm et al [20] combined this actuator for a micro-machined silicon valve; the

advantages of this device in operation are that the valve can be switched at only two

stages (closed /opened) under the supplied DC current Additionally, another type of

MIA, which is called novel IU-shaped electro-mechanical actuator as part of six

degree of freedom, was proposed and investigated by Lebedev and co-workers [21]

This actuator is a new alternative for implementing precision technology actuators It

comprises an I-shaped ferromagnetic mover and two U-shaped stator cores with

suspension and propulsion coils The stator cores are magnetically coupled by

permanent magnets In ref [22], the authors described a high-speed moving iron type

lift actuator; the construction of this actuator consists of two electro-magnetic coils

and an armature sprung by springs This design can improve the working speed

Beside, the robust controller was applied to control accurately position of this actuator

The Moving-Magnet Actuators (MMAs) are based on a permanent magnet

positions at rest Supplying one electromagnet to provide a magnetic field pulse

adding to the permanent magnet field and making the opposite with the second

electro-magnet allows the permanent magnet to move toward the first electromagnet,

and vice-versa

Figure 1-4 Configuration of moving-magnet actuator

Figure 1-5 The mechanical construction of EMV

The general configuration of MMA was depicted in Fig 1-4 This actuator was

demonstrated in [3, 17, 19, 20, 23 and 27], different types with modified configuration

were analyzed and compared the magnitude of the magnetic force, considering with

both theory and experiment One of the most effective applications with MMAs was

applied to the electro-mechanical vale (EMV) [17, 20, 26, and 27] An EMV system

consists of two opposing electro-magnets, an armature, two springs and an engine

valve Fig 1-5 shows the basically mechanical structure of EMV The armature moves

between two electro-magnets When neither magnet is energized, the armature is held

at the mid-point of two magnets by two springs located on either side of the armature

This system is used to control the motion of the engine valve The engine valve is then

in turn used to control the flow of air into and out of a combustion engine cylinder

Kawabe et al [22] developed and investigated a robust control method for controlling

the actuator; it is proved more accuracy position in controlling MMA

The principle of three ways to establish the construction of magnetic actuators

and some of their applications were described above Nowadays, the magnetic

actuator’s branch was extremely developed and applied in a wide range of the

industrial actuators, such as LMAs, tubular permanent-magnet generator/machines,

linear oscillo-actuators and generators have been increasingly researched and

developed [1-6, 14-27] Their use is in linear solenoid actuators, high-speed packing,

manufacturing sensors, machine tool sliding tables and pen recorders, microphones,

moving-coil meters, print-head actuators, disk-drive head actuators, actuators for

industrial robots, pneumatic pumps, car door locks and many others

Furthermore, some researches investigated the magnetic force caused by the

electrical magnetic effect versus permanent magnet with variables in space depicted in

[7] One study, [8], focused mainly on improving the performance of a permanent

magnet by using fixation and wave energy conversion in electrical fields through

direct drive In [9-12], the researchers investigated the interaction /repulsion force

between two permanent magnets, the apparatus was equipped in the laboratory for

examining the experimental formula of magnetic force

Figure 1-6 The conformation of EMA

Chen et al [13] proposed a prototype of a non-conventional electro-magnetic

actuator (EMA) Fig.1-6 depicts the perspective of EMA, comprising a motion pad

and two active coils The movement of the motion pad is due to the repelling force

between the coils and the magnet affixed to the pad The advantage is that it has large

moving-range, and can control accuracy position with the optical gap sensor feedback

signal

Another type of magnetic actuator, which is called tubular brushless permanent

magnet linear motor, was described in [1, 6, and 19] The design of this actuator bears

some similarities to a transverse flux motor Fig 1-7 demonstrates the structure of this

actuator Its advantage is with high thrust force capacity, low losses, and small

electrical time constant and rapid response

Figure 1-7 Tubular brushless permanent magnet linear motor

As above studies and applications of the magnetic actuators, they proved more

benefits and advantages in real applications Hence, that is a motivation leading to our

research for choosing LMA

1.2.2 A Survey Squeeze Film Damper

The rotor dynamics are required for stabilities The first problem may be

reduced the vibration of rotor response by improved balancing, or by modification

into the rotor-bearing systems to change the critical speeds of the system out of the

working region, or by changing external damping to limit peak amplitudes as the rotor

system traverses the critical speeds Subsynchronous rotor instabilities may be

avoided by eliminating the instability mechanism, by rising the natural frequency of

the rotor-bearing system as high as possible, or by introducing damping to raise the

onset speed of instability Squeeze film dampers (SFDs) are essential components of

vibration energy and isolation of structural components, as well as the capability to

improve the dynamic stability characteristics of inherently unstable rotor-bearing

systems

Figure 1-8 The ideal model of squeeze film damper

A Squeeze Film Damper (SFD) is a special type of bearing, comprising a

journal and a ball bearing The journal (called an inner damper ring) is mounted on the

outer race of a rolling element bearing with non-rotation, and the ODR (in some cases,

the ODR is the damper housing) is stationary The annular thin film, typically less

than 0.250 mm between the Inner Damper Ring (IDR) and the Outer Damper Ring

(ODR), is filled with lubricant In operation, as the IDR moves as a result of dynamic

forces acting on the system, the fluid is displaced to accommodate these motions As a

result, hydrodynamic squeeze film pressures create the fluid forces acting on the

journal to attenuate transmitted forces and reduce the rotor amplitude of motion The

amount of damping is considered based on the critical design If the damping is too

large, the damper acts as a rigid constraint to the rotor-bearing system with large

forces transmitted to the supporting structure On the contrary, if the damping is too

light, the damper is ineffectively and likely to permit large amplitude vibratory motion

with possible subsynchronous vibration

The idealized model of squeeze film damper is generally depicted schematically

in Fig.1-8 A journal is mounted on the external race of a rolling element bearing and

prevented from spinning with loose pins or a squirrel cage that provides a centering

elastic mechanism

As known, the dynamic behaviors of SFD is very sensitive to the mechanical

parameters, i.e feeding grove, seal, centering spring, rotor setup (unbalance mass,

operating condition) and construction of SFD In references [28-30], the authors had

depicted the effect of circumferential feeding groove and seal on the unbalance

response of a rigid rotor Both theoretical simulation and experiments performed the

feeding grove’s location and size, and also sealed SFD affected the dynamic responses

of a rotor in SFD In another reference [31], Chen was proved the effects of side

clearance by theoretic The study indicated that both of the damper stiffness and

damping characteristics were specifically affected on the rotors system Furthermore,

the dynamic characteristic theoretical analysis of floating ring SFD was introduced by

Rezvani and Hahn [32], the literature illustrated that the frequency response was

highly dependent on the stiffness and unbalance mass, somewhat dependent on the

mass

(a)

(b)

Figure 1-9 Different configurations of conventional fluid damper

a) Santiago’s damper ; b) Fleming’s damper; c) Shafei’s damper; d) Mu’s damper

In Fig 1-9, some constructions of SFDs with traditional fluid were depicted

Santiago and Andres [33, 34] proposed and tested an Integral Squeeze Film Dampers

(ISFDs) Fig 1-9(a) shows the configuration of ISFD The innovative design of the

SFD allows a substantial reduction in the axial dimensions with respect to the

conventional arrangements In fact, the retaining springs were machined integral with

the body of the damper The squeeze film region was represented by the gap between

the pads and the ring Experiments of test-rig rotor allowed identification of the

viscous damping coefficients due to the ISFDs that exhibited an approximate linear

increase with the amplitude of vibration

Fleming [35] implemented the dual clearance SFD for high load condition,

described couple film layers due to working condition of rotor With normal

conditions, only one clearance film is active, while with high unbalance conditions,

both films are active Fig 1-9 (b) illustrates SFD model proposed by the author

In addition, in Fig 1-9, a Hybrid Squeeze Film Damper (HSFD) was described

and proposed for using active vibration control of rotors The basic idea is to control

the flow in SFD through the movable seals, thus achieving the ability to change the

damper from short to long dampers and vice versa A variable geometry with active

control logic was implemented [36-38] The former configuration is more effective in

limiting the transmitted force to the support while the latter one, because of the high

damping capacity, allows a better reduction of the amplitude response of the rotor As

a consequence, the long damper configuration is recommended during run-up and

coast down On the contrary, the short damper configuration is beneficial at operating

speeds above resonance, where it is more effective than the long damper in reducing

the force at supports

In literature, Murthy [40] presented a conical hydrodynamic bearing considering

the influence of the working clearance and oil film stiffness of the bearing, and

analyzing the number of lobes in the form of scallops In addition, the numerical

results of the relations between amplitude of the shaft versus the rotational speed and

film clearance were described by Bonneau and Frene [41] As reported, theoretical

and experimental approaches of SFDs are to regulate the radial clearance Fig 1-9 (d)

shows an active SFD using a movable conical damper ring Mu et al [42] had just

only concentrated on the theoretical simulation for the conical damper, which can vary

the damping force depending on the variation of clearance It was possible to have the

optimum conditions for each regime of rotational speed The damper can be controlled

to minimize the vibration amplitude within the working speed by using on-off control

method

Beside the conventional fluid SFDs, other researchers concentrated in ER/MR

fluid applying on SFD in recent years The theoretical attention and experimental

approach of ER fluid are shown in the recent papers [46-54] The characteristics of the

ER fluid can be controlled by a pair of rings as electrodes Fig 1-10 describes the

different types of the ER dampers The ER damper model of Morishita, Gouzhi and

Lim were showed in Figs 1-9 (a), (b) and (c), respectively

Morishita’s model comprised two electrodes connecting the inner to the outer

rings of the damper Also one electrode was set up in the damper housing and the

other to the center spring retainer independently There are two ceramic insulators

placed between the electrode and housing, and also between the electrode and the

center spring retainer Several centering spring pins were necessary to be installed to

hold the IDR in the center

Ahn and co-workers [47-48] applied and proposed a prototype for new type of

CSFD using ER fluid Construction of the model has a little modified model

comparing to Morishita’s model Both of authors presented the stability of the rotor

system, and also evaluated the effective damper under controlling the applied voltage

on electrode by experiment Tichy [49] expressed the mathematic model of ER fluid

using Bingham fluid model to describe the yield shear stress and viscosity of ER fluid;

a simple rotordynamic system was applied to illustrating the optimization of

eccentricity and transmissibility by varying the applied voltages Vance [50-51]

focused on a disk type ER damper by regarding different systems for actively

controlled damping in aircraft engines The Vance’s damper configuration is nearly

similar to Lim’s model [53], but it consisted of six thin non-rotating disks moving

with outer race of a ball bearing and with five non-rotating disks attached to the

housing and sandwiches in between, whereas Lim’s model has only one non-rotating

disk Gouzhi et al [52] designed an ER damper with multi-layer This damper consists

of two opposite placed parts, a fixed one and a moving one, and each part with four

uniformly separated concentric cylindrical rings This model was showed in Fig 1-10

(b), the fixed part was fastened in the housing as a negative pole (-) of the electric

field, and the moving part was fastened to the outer ring of rolling bearing as a

positive pole (+) Beside, the modification and investigation of the configuration for

improving ER damper was mentioned Jung et al [54] studied the behaviour of ER

fluid by lubricant analysis of short SFD with assuming fluid as Bingham’s fluids The

expressions of research were proved that the ER fluid was very effective on the SFD

in rotor-dynamics for attenuating vibration

The MR fluid was applied to rotor machinery [55-63] Fig 1-11 depicted some

constructions of MR dampers Wang et al [55, 56] studied on theoretical analysis of

mechanical properties of the squeeze film and the unbalance response of an MR fluid

SFD-rigid rotor, showed the best control reducing effectively the vibration within the

operation speed A disk-type MR damper operating in shear mode and MR-SFD

operating in squeeze film mode for controlling the vibration of rotor system has been

developed by Zhu et al [57-59] Forte and colleague presented a numerical simulation

and an experiment of MR damper with the test-rig made of slender shaft supported by

two iolite bearings and unbalance disk [60] It was shown that the dynamic

characteristic of rotor systems supported on ER and MR fluid damper could

effectively control the vibration of rotor system in a wide range of rotational speeds

Amado and Navarro [61] used semi-active control for balancing compensation based

on sliding-mode control techniques The rotor test-rig systems were mounted one on

journal bearing, and another on controllable MR damper The study aims reducing the

amplitude of synchronous vibration when passing through the first critical speed A

novel MR damper was also investigated by Carmignani et al [62], this damper model

had a little modifications comparing with Forte’s model, which was described in Fig

1-11 (d) and Fig 1-11(c)

(a) (b)

Figure 1-11 Different configurations of MR damper

a) Wang’s damper; b) Wang’s damper; c) Forte’s damper; d) Carmignani’s damper

In addition, a semi-active SFD using MR fluid was studied by Kim and Lee [63] The authors proposed a new damper model, and then optimized the characteristic and evaluated the effect of MR fluid by using experiment analysis with different fluid tests However, contrary to expectations, since the ER and MR fluid have generally consisted of the micro-sized solid particles in a suitable base oil, so it causes the restrictions of the rotor-machinery in real application Based on the above descriptions, Table 1 summarizes the advantages and restrictions of various fluid types used in SFDs

Table 1-1 Comparison of fluid types applied on SFD

Functional Fluid Conventional

lubricant

Rheological fluid (MR)

Magneto-Electro-Rheological fluid (ER)

- Controllable &

parameters

rather good (floating spring, land film, film thickness /clearance, pressure oil, etc…)

good (damping and stiffness of fluid)

good (damping and stiffness of fluid)

- Fabrication/

components

simple

rather complex (extra components)

more complex (extra components)

- Real Application (in

rotordynamic)

good

no (up to now) possible application

no (up to now)

From overviews as mentioned previously, the effects of the SFD in

rotor-dynamics were studied and investigated Many configurations of SFDs were invented Type of fluid

Factors

by many researchers, the mathematical models were also developed for adaptation

with its aspects of the damper, i.e the conventional fluid, ER fluid, MR fluid, and the

mechanical modification of damper’s construction Hence, the attracted competences

of SFD were promoted in this study

1.3 Aim of this thesis

This study is to investigate a Linear Magnetic Actuator which applied

appropriately to the Controllable Squeeze Film Damper The novel configurations of

LMA and SFD were proposed, designed and fabricated All of the evaluated

experimental apparatus and the test-rig of rotor system were absolutely conducted in

laboratory Other aspects of this research can be described as below:

- The operating principle of the LMA was obtained form the physical essence

of the interaction phenomena between permanent magnet and electro-magnet In this

case, the repulsive and attractive forces between two polarities of magnets can be

controlled through the magnitude and direction of the applied DC current into the

coils

- The magnetic formula of novel LMA was investigated via experimental

measurements for the repulsive and attractive forces respected to the proposed LMA

- The position control of LMA was verified both of the PID and Fuzzy-PID

controller by proving the working ability of actuator The experimental results

revealed that the advanced control algorithm was exactly positioning control more

than another

- Mathematical model of the CSFD was investigated, and the effect of clearance

of damper on pressure distribution and fluid force was considered It revealed the

basis criterion for choosing the design parameters of the damper

- The obtained experimental results of rotor dynamic in steady state responses,

circular orbits, and on-off control showed that the proposed damper was effectively

and reliably in the real applications

1.4 Layout of thesis

This thesis unites a fairly diverse range of subjects separated into chapters and a

brief word as to their content may prove useful to the reader Where possible, separate

chapters have been used to introduce distinct areas of research, yet some interactions

and cross referencing are necessary

The survey of magnetic actuators and squeeze film dampers has been

highlighted in this Chapter The principle of operation and mathematic model of the

novel LMA was introduced in Chapter 2 In chapter 3, a Controllable Squeeze Film

Damper is compliantly designed with the proposed LMA depicted Both of

mechanical design and mathematical model of CSFD were investigated, which lead to

the applied ability in the rotor system Chapter 4 expresses the researched innovation,

which can improve the electro-magnetic from experiment The experimental results

had the valid form for developing the formula of electro-magnetic force Furthermore,

the advanced controller combined fuzzy and PID controller was applied to control the

position of the actuator The obtained results were proved the working ability of the

contents considered the steady state response and circular orbit of the rotor dynamic

behaviour So far, the on-off control was applied to the test-rig model via the

characteristic dynamic of the rotor test-rig The experimental results of rotor system

were revealed that the application of Controllable Squeeze Film damper using a novel

LMA would be used in the reality Chapter 6 gives conclusions and future work

Chapter 2 Novel Linear Magnetic Actuator

2.1 Principal design of Novel LMA

Electro-magnets behave in some ways like permanent-magnets A current

flowing in a wire will produce a magnetic field, and the shape of the wire windings

will determine the overall shape of the produced magnetic field A solenoid (or coil)

carrying a current will produce a magnetic field equivalent to that of a permanent bar

(or cylindrical) magnet Fig 2-1 depicts the principle of the equivalence between

electro-magnet and permanent magnet

Current carrying coil Permanent magnet Figure 2-1 Demonstrating the equivalence of a coil and a magnet

The strength of the magnetic field created by an electromagnet increases with

current An object in the vicinity of such a field will have a force inferred upon it,

which may be varied by altering the current The interaction force between the

permanent magnet and the coil can be adjusted by varying the current applied to coil

(a)

(b)

Figure 2-2 The assembly and principle of LMA

(a) Mechanical model of LMA; (b) Illustration of the magnetic poles of U-shape

It had been known that the magnetic actuators are classified based on the type of

mover, i.e moving-coil, moving-iron, and moving-magnet Many mechanical

structures and applications of magnetic actuators are presented in the Section 1.2.1 As

a consequence, actuators based on the magnetic effect have been developed and

effectively applied and they are still actively researched In this section, the proposed

LMA will be mentioned