# Modeling and Formulation of a Novel Microoptoelectromechanical Gyroscope

Authors: Bohua Sun; Bo Zhang; Mohamed Toriq Khan
Journal: Journal of Nanomaterials
 (2008)

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## Abstract

This paper proposed a novel design of microgyroscope based on MEMS structures and optic interferometric microdisplacement measurement technique. The gyroscope consists of microvibrator and interferometric readout. Using Coriolis force, the vibrator transfers the system rotation into a forced vibration; the induced vibration can be sensed by the interferometric microdisplacement measurement system. The optic measurement system has two mirrors which will reflect two rays into a detector. The comprehensive studies on the formulation and analysis of the proposed gyroscope have been undertaken; two key sensor equations have been derived in the first time in the world: (1) relation between rotation and phase shift of lightΔφ=(4πl0/λ)+(8π/λ)(xmaxQy/ωy)Ω(t)sin(ωdt), (2) relation between rotation and interferometric intensity of light I(t)≈(8π/λ)(xmaxQy/ωy)Ω(t)sin(ωdt)sin(4πl0/λ). The comparison of the proposed gyroscope and well-know Sagnac formulation has been investigated; it shown that the proposed model is much better than Sagnac ones. The new model has finally get rid of needing very long fiber in the case of Sagnac gyroscope. The innovative model gives a new hope to fabricate high accurate and cheaper gyroscope. To date, the proposed gyroscope is the most accurate gyroscope.


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## Body

## 1. Introduction

Gyroscopes are
the inertial measurement devices, which are used to detect angular rotation
rate of the objects. which are widely used for guidance, navigation, airplanes, spacecrafts, missiles, automobiles, and even consumer electronics to maintain
orientation, measure the angular motion of essential objects for the control
and stabilization of its attitude.The gyroscope
development is going through the processes from the macrosize to the microsize. Traditional gyroscopes with spinning
wheels employed in the present aerospace and military industries are bulky,
which need lubricant and wear out, as stability control system, navigation
system, and so forth. Ring laser gyroscopes (RLGs) and fiber optical gyroscopes
(FOGs) are high precision. But they are expensive and heavy. The micro applications require the
host structures to be
transformed from the huge spin wheel mass to the tiny light vibration mass or
optical interferometer measurement
system fabricated by microelectromechanical system (MEMS) technology like MEMS vibratory gyroscopes and fiber
optical gyroscopes [1].In terms of small size critical, MEMS vibratory gyroscopes
are the perfect substitution, especially for microsatellites, microunmanned vehicles,
digital cameras, and notebook, PDA, due to their small size. MEMS gyroscopes
are also suitable for longtime employ because of low power consumption, and the
bulk fabrication processes can produce batch applications. Since the light
weight and low power consumption, some small instruments like digital cameras
can wear several MEMS gyroscopes and accelerometers for positioning or
monitoring its activities either in vehicle or out of vehicle during travel
[2]. In fact, some types of sell MEMS gyroscopes have started for dynamic
control of automobiles a few years ago. Silicon basement sensing system is
providing MEMS gyroscopes by Analog Devices.Silicon-based MEMS gyroscopes processes may be categorized
into bulk micromachining and surface micromachining. A large mass is desired
for a gyroscope because thermomechanical noise is inversely proportional to
mass weight. Generally, MEMS gyroscopes and bulk micromachined gyroscopes have
large mass and relatively large readout capacitance or piezoresistive readout. Therefore,
most bulk bonding to a separate electronic readout chips (two chips). Two chips
gyroscopes are expensive and have a relatively large package size that
restricts their applications in consumer electronics regardless of price. In
contrast, surface micromachining gyroscopes have small mass and relatively
small readout capacitance. The sensors and readout electronics are usually
integrated on a single chip to reduce parasitic capacitance and size.MEMS gyroscopes system can only sense in one axis, but angular rate is requiring
a vector, measuring all three-axis rotations. Assembling three gyroscopes
together is needed, which will increase the package size, and the complexity of
packaging cost. The capacitance readout electronic circuits have the essential
shortcoming at the sensitivity, responding time, bandwidth, and so forth.
Therefore, the current MEMS gyroscopes only occupy the low and middle
sensitivity scales markets.On the other hand, many intrinsic optical theories are used
in the new field for pressure, temperature, acceleration, skin friction
sensors, and so forth, and the performances of optical sensors and measurements
scale are better than mechanical sensors or others at sensitivity, volumes,
cost, stability, and so forth. Optical type gyroscopes have advantages at the
sensitivity, performance, responding time, lifetime, and bandwidth. They occupy
the high sensitivity and performance markets. Ring laser gyroscopes, fiber
optical gyroscopes, and other optical gyroscopes are too large and heavy for
many applications due to the Sagnac effect principle, which is the basic theory
for all kinds of optical gyroscopes. The large size comes from the long
distance light path to create the enough interference and the lack of MEMS
fabrication technology for the micro-optical devices.However, the MEMS inertial sensors have the following
advantages compared with the conventional inertial instruments [3].(1) Smaller Volume and Lighter Weight
The advanced semiconductor manufacturing
processes make the volume smaller and the weight of the microinertial
mechanical sensors lighter.(2) Mass Production and Lower Production Cost
Thousands of microinertial devices in
a 3 inch or 4 inch silicon chip could be yielded with the mature technique and
batch production, which will improve the rate of finished products and reducing
the cost. The cost of microinertial devices, then, will depend on the
packaging, testing, and accessory circuits. It is undoubted that the cost would
drop greatly when the true integration of electromechanical is accomplished.(3) Antiharsh Environments and Wider Applications
With the small testing proof mass, a
micromechanical accelerometer is adapted to measure the high acceleration. The
measurement range could be extended widely by the micromechanical gyroscopes
without rotating parts.(4) Lower Consumption, Higher Sensitivity and Efficiency
When performing
the same task, the consumption of micromechanical devices is only one tenth of
the traditional ones or even less, while the operation speed could be improved
ten times. Certain reasons, for example, the no delay performance of integrated
micromechanical devices results in their wide use in high-speed application.(5) Multifunction and Intelligence
Most micromechanical devices integrated the
transducer, actuator, and electronic circuits. It is easier to realize the
multifunction and intelligence of micromechanical devices after using the
intelligent materials and structures.The novel combination of the microvibratory gyroscope and
optical interferometer readout system is proposed in this paper. The merged
system has the small size and high performance and is suitable for MEMS
fabrication technology. In this paper, the system design, mathematical model,
and performance analysis are presented.


## 2. Micromechanical Design of The Moems Gyroscope

Based on the comprehensive review of the optical gyroscopes
and MEMS silicon-based gyroscopes, we propose  a hybrid model  which combine MEMS silicon-based oscillation gyroscopes and micro-optical
interferometer readout system. It will take both advantages of MEMS vibratory
gyros and optical sensing technique.  It
is believed that the proposed gyroscope can be massively fabricated with high
performance at low cost.The operation of thez-axis vibratory rate gyroscope is best
illustrated by the spring-mass system shown in Figure 1. As in all vibratory
rate gyroscopes, Coriolis acceleration is generated by an oscillating proof
mass in a rotating reference frame. The proof mass is oscillated along the
x-axis (the driven mode), the reference frame rotates around the z-axis,  and the Coriolis acceleration is detected as deflections
along the y-axis (the sense mode) [4].Figure 1
Model of coriolis force.The microelectromechanical sense element of the surface
micromachinedz-axis vibratory rate gyro is also shown in Figure 2. The
structure comprises three major elements: the suspension system, the comb drive
used to sustain oscillation, and the
proof mass forced by the Coriolis force in y-axis.Figure 2
Solid model of MEMS vibratory structure.Coriolis acceleration is(1)a→c=2⋅v→×Ω→ which shows that orthogonal lateral-axis vibration and acceleration
sensing are required to detect the z-axis rotation. The mathematics principle
model is shown in Figure 1.One vibration
mode corresponds to the vibration of mass in thex-direction with a vibration
frequency of ωx. The other vibration corresponds to the vibration of mass in the
y-direction with a vibration frequency of ωy [5, 6].For operation, the mass is driven into vibration in thex-direction with
a driving frequency ωd.Given driven signal,(2)x=Adsinωdt. Then, if the
system rotates around the z-axis with a
constant angular rate of Ω, the Coriolis force appears in the y-axis and impelling the
mass vibrating in y-axis: (3)x˙=Adωdcosωdt,Fc=2mx˙Ω. Differential equation
for the mass movement in the y-direction is given by (4)my¨+cyy˙+kyy=2mAdωdΩsin(ωdt+π2). The steady-state
solution is given by (5)y=Aysin(ωdt+π2−φ)=Aycos(ωdt−φ). There, amplitude
at y-direction is (6)Ay=2AdωdΩωy2(1−ωd2/ωy2)2+4ζy2(ωd2/ωy2). Phase is (7)φ=tan−12ζyωdωyωy2−ωd2,ζy=cy2mωy, where Qy is the quality factor at the sensing mode given by (8)Qy=12ζy. Let ωd=ωy,
the mass amplitude becomes at resonance (9)Ay=2AdΩQyωy=2AdQyωyΩ. Equation (9) shows that the measurement of
rotation Ω can be achieved by sensing the amplitude of vibration in y-direction,
the problem of measurement of rotation becomes a problem of sensing a
displacement. It is the foundation of vibratory gyroscope principle.The system response froced Coriolis
acceleration alongy-axis is given by (9).The vibration alongy-axis is: (10)yΩ=2AdQyωysin(ωdt+π2−φ). The results of the relative between the angular rate and
Coriolis acceleration are clear, which shows the y-axis amplitude proportion
with the z-axis angular rate, and the x-axis driver oscillation redound to
amplifier the amplitude of the y-axis [7]. In the microsize, the nature
frequency of oscillation beams and proof mass is very high, and the weight is
very light. It is of the advantage driving the mass at the x-axis under low power consumption,
and achieves the high sensitivity.Now, the angular rate measurements convert to measure they-axis amplitude, shown in Figure 3. This changing gives the measurement idea,
which is microdisplacement measurement. There are many methods to measure
microdisplacements like bridge resistance, bridge capacitance,
piezoelectricity, optical modulation methods, and so forth. Currently, the optical
interferometer is the most precise method, which is the method proposed in this
paper.Figure 3
Oscillating coriolis displacements creating by variable rotation velocity.


## 3. Micro-Optical Interferometric Design of The Moems Gyroscope

From (9), we know that
the problem of measurement of rotation becomes a problem of sensing a displacement.
There are several ways to sense the displacement, but up to now the optic
sensing is the most accurate one.The optical
interferometric readout system has the high sensitivity, high precision, high
integration, low cost characteristics. Interference, which is a complex wave
phenomenon, is one of the useful readout, which can be happened and observed in
frequency wave areas, like the mechanical wave, sound wave, light wave,
electric wave, and so forth [8]. In the optical technology, the interference
will be happened under those situations, no matter the sensor is a Michelson, a
Mach-Zehnder, a Sagnac, or a Fabry-Perot interferometer, (1) frequency of two
beams must be same; (2) the vibration of two beams must be same direction; (3)
phase shift of two beams must be holed constant.The intensity of general interferometer output is  composition of two light beamsI1 and I2: (11)I=I1+I2+2I1I2cosφ12. Here, φ12 is the
phase shift different
of two beams at interaction
point: (12)φ12=φ1−φ2−2πΔLλ. Here φ1 and φ2 are initialization phase of two beams. ΔL is the path-length different of two beams.The periodic intensity patterns are shown in Figure4.Interferometer output intensity and patterns.The phenomenon of the
interference of light underlies many high-precision measuring systems and displacement
sensors. The use of optical fibers allows making such devices extremely compact
and economic. In fiber optic interferometer, the interference occurs at the partially reflecting
end face surface of the fiber and an external mirror. The size of the sensitive
element based on this principle can be as small as diameter of the fiber, and
the sensitivity can achieve subangstrom level. Additionally, such sensor is not
sensitive to electromagnetic interference and can be used in hostile
environment.Consider the principle of operation of
the fiber optic interferometer, the system view shown in Figure5, and the
magnifying sensor head configurations
shown in Figure 6.Figure 5
Diagram of micro fiber optical interferometer.Figure 6
Magnify fiber optic interferometer head.The radiation of the laser diode 1 is coupled into fiber 2
and propagates through coupler 3 to fiber 4. Then, one part of radiation is
reflected from the end face of fiber 4, and other part of radiation is flashed
into the air, reflected from the mirror 5 and returned back into fiber 4. The
optical beam reflected from the end face of fiber 4 interferes with the beam
reflected from the mirror. As a result, the intensity of the optical radiation
at photodetector 5 is periodically changed depending on the distancex0 between the fibers and mirrors as follows. The
path-length difference is ΔL=2x0.The out intensity is(13)I=I1+I2+2I1I2cos(4πλx0+φ0). Here, φ0 is initialization phase shift. λ is the wavelength of the light source used; phase shift is Δφ=(2π/λ)ΔL=(4π/λ)x0;I1 and I2 are intensities of these two reflected rays.In fiber optic interferometer,I1=I0R1 is the intensity of the light reflected from
the end face surface of the fiber, and I2=(1−R1)2R2I0 is the intensity of the light reflected from
an external mirror and returned back into the fiber, where I0 is the intensity of the laser diode radiation
coupled into the fiber, R1 is the reflectivity of the end face of the
fiber, and R2 is the reflectivity of an external mirror. Figure 7 shows the simulation
result of the relationship between sensor output I0/I and gap distance x0.
This gap distance x0 is the position to setup the movement
reflected surface, which is also the definition of the interferometer cavity
length [9, 10]: (14)I=I0[R1+(1−R1)2R2+2(1−R1)R1R2cos(4πλx0+φ0)], in which I1=I0R1 and I2=(1−R1)2R2I0 are constant, by applying demodulation technique, the above equation (14) can be
simplified as (15)I≈cos(4πλx0+φ0). For simplification and cavity design purpose, let x0=kλ/2,
and φ0=0,
then we have (16)Δφ=4πλx0=2kπ,k=0,±1,±2,…,Imax=(IoR1+(1−R1)2R2Io)2. Let x0=(λ/4)(2k+1),(17)Δφ=4πλx0=(2k+1)π,k=0,±1,±2,…,Imin=(IoR1−(1−R1)2R2Io)2. From the above intensity distributing analysis, as
every time the cavity length x0 is changing λ/4,
the intensity would be varied from maxima to minima.Figure 7
Simulation result of the relationship between sensor outputI0/I and gap distance x.So the movement distance can be calculated by(18)ΔS=λ4N. Here, ΔS is the distance moving from initialization position x0. N is the times of the intensity changing.Letφ0′=(4π/λ)x0 be presenting cavity x0 equivalent initialization phase shift. The
initialization phase φ0′ is located at the middle of Imax and Imin,
because here is maxima linear slope, shown in Figure 8. For microdisplacement,
the accurate output result can be achieved in this linear region. The
initialization position for movement reflected surface is (19)x0=kλ8,Ix0=Imax−Imin2. Now, we will consider the interferometric signal appearing as
a result of the reflection of the light from the vibrating surface (resonator).
When the resonator oscillates, the phase difference of interfering rays is
varied as follows. The principle diagram shown in Figure 9 is describing the
affection oscillation input to output intensity of the microfiber optical
interferometer. The distance measurement performance of the micro-optical fiber
interferometer is proved under 5 nm [11, 12].Figure 8
Initialization position of the vibratory reflected surface and linear region.Figure 9
Effecting oscillation input to output intensity.Figure 10
Output intensity atΩ=0.Figure 11
Output intensity atΩ≠0rad/s.According to the Coriolis acceleration theory, they-axis
vibration created by z-axis ration rate is (20)y=Aysin(ωdt+π2−φ)=Aycos(ωdt−φ). Path-length difference is (21)ΔL=2[x0+Aycos(ωdt−φ)],Δφ=4πλ[x0+Aycos(ωdt−φ)]. This Aycos(ωdt−φ) vibration signal  gives rise to the
following modulation of the light intensity: (22)I(t)≅cos{4πλ[x0+Aycos(ωdt−φ)]}≅cos[4πλAycos(ωdt−φ)+4πλx0]. Expanding I(t) in a Fourier series, and Bessel function cos(xsiny)=J0(x)+2∑n=1∞J2n(x)cos2ny,
the alternating
components of the light modulation is: (23)I(t)≅J1(φω)sin(ωt−η)sinφ0′−J2(φω)cos(ωt−η)cosφ0′+⋯, where Ji(φω) is the Bessel functions, φω=(4π/λ)Ay.
When φω≪1, then Ji(φω) equals approximately φω/2 and, therefore, an alternating component of
intensity I(t) will be proportional to displacement of the
resonator from the equilibrium: I(t)~sin(ωt): (24)I(t)≅12φωsin(ωt−η)sinφ0′≅2πλAysinφ0′cos(ωdt−φ). Let ωd=ωy,
the amplitude becomes (25)Ay=2AdΩQyωy=2AdQyωyΩ,(26)I(t)≅4πAdQyλωyΩsinφ0′sin(ωdt+π2−φ),(27)Ω≅I(t)λωy4πAdQysinφ0′sin(ωdt+(π/2)−φ). Let α=λωy/4πAdQysinφ0′,(28)Ω≅αI(t)cos(ωdt−φ)=αI(t)cos−1(ωdt−φ). The linear displacement linked between the y-axis vibration
in MEMS structure and the optical readout system is the key factor for the
microopticelectromechanical gyroscope; the system model is  in Figure 12. The vibration
parameter is the requirement measurement, which is creating the intensity
changing as well.Figure 12
Model of micro vibratory optical readout gyroscope system.The relative parameters of the angular motion can be
calculated by integrating (27). This results in the equation below indicate
angular displacement, θ, which is useful for navigation
systems directly.The angular movement is the integral of angular rate:(29)Δθ=∫Ω(t)dt=α∫t1t2I(t)cos(ωd−φ)dt=[α1ωdln|tan(ωdt2+π4)|+C]∫t1t2I(t)dt. From (29), the operator of navigation would indicate the
angular movement variation value Δθ=θt2−θt1;
feedback signal would emendate the application during the steering.Therefore for any intensity readout, the angular movement
value can be calculated asΔθ due to the reference frame, by means of a simple digital signal processor
circuit attached to the optical readout of the MOEMS device.If (27) is differentiated, the rotation acceleration is
obtained, shown in (30)θ¨=dΩdt=αI˙(t)+I(t)ωdtan(ωdt−φ)cos(ωdt−φ). This is another useful output signal to control the system’s
stability. From (30), the signal is fast attenuation signal as the expectation.
The application is illustrated in Figure 13.Figure 13
Angular acceleration attenuation diagram.


## 4. Moems Gyroscope Comparison with Optical Gyroscope Based on Sagnac Effect

The Sagnac effect is the
relative phase shift between two beams of light that have traveled an identical
path in opposite direction in a rotating frame. The explanation of the Sagnac
effect is simple for the inertial frame of reference. The motions of the
mirrors, during the light transit time between mirrors, cause the clockwise and
counterclockwise waves to be reflected at different points of space, which
leads to an optical path difference. Modern fiber-optic gyroscopes (Sagnac
interferometers) used for navigation are based on this effect. They allow
highly accurate measurements of rotation rates down to about0.1° per hour. The schematic setup of a Sagnac interferometer is shown in
Figure 14. Light is decomposed into two beams by a 50:50 beam splitter, with
one traveling clockwise (CW) and the other counterclockwise (CCW) around a
polarization-maintaining single-mode glass-fiber loop. The two beams interfere
after passage through the loop, and the interference signal is measured with a
photodiode. If only reciprocal effects are involved in the experiment, then the
two beams interfere constructively (relative phase shift Δϕ=0). If Δϕ≠0,
then nonreciprocal effects occur, one of them is the Sagnac effect that results
from rotation of the fiber loop during the measurement.Figure 14
Schematic setup of a Sagnac interferometer.The Sagnac effect is a
relativistic effect but can be understood with a simple picture (see Figure15). Let us assume that a fiber coil (N windings with radius R)
is rotated clockwise with an angular velocity, and that light is injected into the loop at
time t=0. At tt≈2πRN/c,
the CW and CCW beams meet again at the starting point. However, due to the
rotation of the loop, they have traveled in different path lengths. Figure 15 on the right
indicates what happen if the loop itself is rotating during this procedure.
Supposing that radius of fiber round is R,
and light emitting and detector sensors are laid in ‘`A" point. The
system is rotating with Ω in the clockwise direction
relatively inertia space. When clockwise direction light (CW) and the
counter-clockwise direction light (CCW) are emitted in opposite direction
around, the photo sensor also rotates from “A" to “A." So the
two light paths have
different length. The clockwise direction light pursues “A" after back,
which crosses the distance more than 2πR. While the counterclockwise
direction light goes face to “A," which crosses the distance less than 2πR. The difference between the travel times causes the difference light
distance [13].The Sagnac effect principle diagram.
(a)(b)Assume light transmitting
in vacuum, which velocity isc=3×108. The paths of clockwise and
counterclockwise light are LCW,LCCW; spending time is tCW,tCCW, individually.LetC=Ccw=Cccw,(31)Lcw=2πR+RΩtcw=Ccwtcw,Lccw=2πR−RΩtccw=Cccwtccw. From (1), Δt is (32)Δt=tcw−tccw=2πR2πΩ−(Ccw−Cccw)Ccw⋅Cccw=2πR2πRΩC2=4AΩC2, where A is area of
ring fiber round.Accounting, it is only approximate and simple evolvement
above result in (32). The strict evolvement should be applied in broad theory
of relativity. The speed
of light transmitted in fiber optical depends on  refractive index of
medium.So, clockwise and counterclockwise light is(33)Ccw=c/n+RΩ1+((c/n)⋅RΩ)/c2=c/n+RΩ1+RΩ/cn,Cccw=c/n−RΩ1−((c/n)⋅RΩ)/c2=c/n−RΩ1−RΩ/cn, where n is refractive index of medium. From (33), we have (34)Δt=tcw−tccw=2πR2πΩ−(Ccw−Cccw)Ccw⋅Cccw≈2πR2RΩ−2RΩ(1−(1/n2))c2/n2=2πR2πRΩC2=4AΩC2. Equation (32) is same as (34) in the vacuum. Corresponding phase
difference is (35)Δϕ=2πΔtcλ=8πAΩλc. The difference in path length can be expressed as (36)ΔL=2RΩt=4πR2NcΩ, and the corresponding phase difference between the two beams
is (37)Δϕ=8π2R2NλcΩ,ΔϕSagnac=8πAcλΩ,A=πR2. It is
interesting to note that although the above calculation is over-simplified
(e.g., the speed of light in vacuum was assumed instead of that in the glass
fiber), it yields the correct result. Exact relativistic calculations show that
the phase shift is indeed independent of the material of the wave guide and the
above equations apply.Since
the Sagnac effect was discovered, this theory is applied to manufacture the
whole optical gyroscope such as laser gyroscope, ring gyroscope, fiber optical
gyroscope, and so forth. The fiber optical gyroscope systems are hasty
developed due to many advantages like no movement parts inside, high precision
output, long consumption, and so forth.The
Sagnac effect method is based on two light beams path-length different created
by rotation speed. The long distance light path is required because of the
highlight speed. So the disadvantages of Sagnac effect gyroscope system are
large in size and weight, complex fabrication processes due to long fiber
optical or optical integrated chip.As mentioned above, in MOEMS gyroscope the light phase shift
created by rotation velocity is described(38)ΔϕMOEMS_Gyro=4πλl0+4πλ2xmaxQyωyΩsin(ωdt). Because (4π/λ)l0 is constant number, which is defined by initialization interferometer
cavity length, (39)ΔϕMOEMS_Gyro−4πλl0=8πλxmaxQyωyΩsin(ωdt). Assume, at the same input
rotation velocity for each gyroscope system, that two-phase shift ratios are (40)ΔϕMOEMS_Gyro−(4π/λ)l0ΔϕSagnac=8πλxmaxQyωyΩsin(ωdt)/8πAcλΩ,|ΔϕMOEMS_Gyro|=|(xmaxQyωycA)ΔϕSagnac|+4πλl0. Here (xmaxQy/ωy)(c/A)≥1,
which means the sensitivity of MOEMS gyroscope system, is higher than optical
gyroscope using Sagnac effect method. So the MOEMS gyroscope design is
satisfied to civilization and military user.


## 5. Conclusion

In this paper, the combination of the micro-optical
interferometer readout system and MEMS vibratory gyroscope is proposed. This
novel micro-optical gyroscope has possessed microsize, light weight, and high
performance features due to MEMS fabrication technology and the precision feature
of the optical interferometer principle. According to comparison with Sagnac
effect, the sensitivity and measurement range of this MOEMS gyroscope system
are at the same level as the FOG system. The real-time testing results for the
MOEMS gyroscope must wait for the first prototype coming out. The full
performance comparisons between the MOEMS and FOG system will be investigated.The novel optical MEMS gyroscope system is the perfect MOEMS
application to combine the optical and MEMS technology. On the size aspect, the
MEMS vibratory structure has been proved and fabricated to convert the rotation
speed to the vibration movement due to Coriolis force theory. On the
performance aspect, the microfiber optical interferometer has solved the
precision distance readout comparing with the electrical readout. The novel
optical MEMS gyroscope can be used from the rate grade to the inertial grade for the pose
stability control in the missile, satellite, motion detector in the
entertainment system like PC game, camera, or hard drive protector.The operation principles of the MOEMS gyro system have been
clearly discussed and created; the mathematics model successfully includes the
theory and equations. The MEMS fabrication processes and package for both the
microvibration part and the micro-optical readout system will be discussed in
the other paper. The first prototype has been sent to MEMS foundry after the
software simulating.



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*Source: 429168-2008-12-04.xml*