Mems Based Digital Gyroscope

Design Phase Project Report

MEMS BASED DIGITAL GYROSCOPE

Submitted in partial fulfillment for the award of the Degree of Bachelor of Technology in Electronics and Communication Engineering

Submitted by

ASHIK A S (Roll No.10415013) ALFIYA KAMAL (Roll No.10415063) ARCHA M S (Roll No.10415067) MUBEENA M (Roll No.10415081)

Under the guidance of

Mrs. SABEENA S

Department of Electronics and Communication Engineering MUSLIM ASSOCIATION COLLEGE OF ENGINEERING

VENJARAMOODU,TRIVANDRUM ,KERALA

OCTOBER-NOVEMBER 2013

CERTIFICATE

This is to certify that the thesis entitled “MEMS BASED DIGITAL

GYROSCOPE” is a bonafide record of design phase project work done by ASHIK A S

(Roll No.10415013) under our supervision and guidance, in partial fulfillment for the

award of Degree of Bachelor of Technology in Electronics and Communication

Engineering from the University of Kerala for the year 2013.

Mrs. SAJITHA P Mrs. SABEENA S (Coordinator) (Guide) Asst. Professor Asst. Professor Dept. of ECE Dept. of ECE

Dr. IBRAHIM SADHAR Head

Dept. of ECE

Place: Date:

ACKNOWLEDGEMENT

First and foremost, I wish to place on record my ardent and earnest gratitude to

my project guide Mrs. SABEENA, Assistant Professor, Department of Electronics and

communication Engineering. Her tutelage and guidance was the leading factor in

translating my efforts to fruition. Her prudent and perspective vision has shown light on

my trail to triumph.

I am extremely happy to mention a great word of gratitude to Dr. IBRAHIM

SADHAR, Head of the Department of Electronics and communication Engineering for

providing me with all facilities for the completion of this work.

Finally yet importantly, I would like to express my gratitude to my project

coordinator Mrs. SAJITHA P, for her valuable assistance provided during the course of

this work.

I would also extend my gratefulness to all the staff members in the Department. I

also thank all my friends and well-wishers who greatly helped me in my endeavour.

ASHIK A S

ABSTRACT

A gyroscope is a device for measuring or maintaining orientation, based

on the principles of angular momentum. A vibrating structure gyroscope or "Coriolis

Vibratory Gyroscope (CVG)" is a wide group of gyroscope using solid-state resonators of

different shapes that functions much like the halters of an insect. The underlying physical

principle is that a vibrating object tends to continue vibrating in the same plane as its

support rotates.

MEMS based ADXRS450 is an angular rate sensor (gyroscope) intended

for industrial, medical, instrumentation, stabilization, and other high performance

applications. An advanced, differential, quad sensor design rejects the influence of linear

acceleration, enabling the ADXRS450 to operate in exceedingly harsh environments

where shock and vibration are present. The ADXRS450 is capable of sensing angular rate

of up to ±300°/sec. Angular rate data is presented as a 16-bit word, as part of a 32-bit SPI

message.

In this project ADXRS450 MEMS gyroscope is used to measure the

angular spinning rate of a spinning sounding rocket. This helps in understanding the

stability of the sounding rocket. The circuit uses a PIC microcontroller to control and

guide the operations of the ADXRS450 sensor. MAX232 and RS232 interfaces are used

for communication with Labview software for graphical evaluation.

http://en.wikipedia.org/wiki/Orientation_(rigid_body)

http://en.wikipedia.org/wiki/Angular_momentum

http://en.wikipedia.org/wiki/Gyroscope

http://en.wikipedia.org/wiki/Halteres

http://en.wikipedia.org/wiki/Vibration

i

CONTENTS

Chapter no: TITLE Page no:

List of abbreviations iii

List of figures iv

List of tables vi

1 INTRODUCTION 1

2 HISTORY OF GYROSCOPES 3

3 TYPES OF GYROSCOPES 8

3.1 Mechanical Gyroscope 8

3.2 Piezoelectric Gyroscope 9

3.3 Optical Gyroscope 9

3.4 Active Ring Laser Gyroscope 10

3.5 Passive Ring Resonator Gyroscope 10

3.6 Closed-Loop Interferometric Fiber Optic Gyroscope 11

3.7 Dynamically Tuned Gyroscope 11

3.8 London Movement Gyroscope 11

3.9 MEMS Gyroscope 12

4 MECHANICAL GYROSCOPE 13

4.1 Space Stable Gyroscope 14

4.2 Gyrocompasses 15

5 THE CORIOLIS FORCE 16

6 MEMS GYROSCOPE 18

ii

6.1 Challenges in Fabrication 23

6.2 Challenges in Packaging 24

7 SOUNDING ROCKET 25

8 PROPOSED APPROACH 29

8.1 Block Diagram of Project 32

9 HARDWARE DESCRIPTION 34

9.1 Sensor ADXRS450 34

9.1.1 SOIC-V Package details 35

9.1.2 Pin Description 36

9.1.3 LCC-V Package details 37

9.1.4 Pin Description 38

9.1.5 Evaluation Board for ADXRS450 40

9.2 PIC 18F6520 41

9.2.1 Features of PIC 18F6520 41

9.2.2 Pin Out 44 9.3 MAX 232 45

9.4 RS 232 47

9.4.1 DB-9 USB Modules 49

10 SOFTWARE IMPLEMENTATION 50 11 FUTURE WORK 53 12 REFERENCE 54

iii

List of Abbreviations

MEMS - Micro Electro Mechanical Systems

TEDCO - Technology Development Corporation

ICBM - Intel Chip Based MacIntosh

RPM - Revolutions per Minute

QFN - Quad Flat no Lead

NASA - National Aeronautics and Space Administration

ADXRS - Angular Dynamic Rate Sensor

PIC - Programmable Interrupt Controller

RS - Recommended Standard

SPI - Serial Peripheral Interface

MAX - Maxim Company Name

USART - Universal Synchronous and Asynchronous

Receiver and Transmitter

PWM - Pulse Width Modulator

EIA - Electronic Industries Association

DTE - Data Terminal Equipment

DCE - Data Communication Equipment

POS - Point Of Scale

USB - Universal Serial Bus

iv

List of Figures

Figure no: TITLE Page no:

2.1 An earlier Gyroscope 4

2.2 Gyroscope housing of Gravity Probe B 6

3.1 Mechanical Gyroscope 8

3.2 Piezoelectric Gyroscope 9

3.3 Optical Gyroscopes 10

4.1 Two axis mechanical gyroscopes 14

6.1 X-axis gyroscope driven mode 20

6.2 X axis Gyroscope 21

6.3 Z Gyroscope 22

6.4 Vibration Gyroscope 22

6.5 Various design options 23

6.6 MEMS Gyroscope Products 24

7.1 Sounding rockets 26

8.1 Pitch Roll and Yaw Axes 31

8.2 Project Block Diagram 32

9.1 SOIC-V 2 & LCC-V Package 35

9.2 Pin out and Application Diagram 35

9.3 Incorrectly Mounted Gyroscope 37

9.4 Pin out And Application Diagram 37

9.5 Gyroscope structure 39

9.6 ADXRS450 chip structure 39

v

9.7 Evaluation board 40

9.8 Pin Out of 64 Pin PIC18F6520 44

9.9 MAX232 Chip 45

9.10 TTL converter 46

9.11 MAX232 Die 46

9.12 A DB-25 Connector 48

9.13 DB-9 USB Family 49

10.1 Front Panel of LabVIEW 51

10.2 Block Diagram and Corresponding Front Panel 52

vi

List of Tables

Table no: TITLE Page no:

9.1 Pin description of SOIC-V package 36

9.2 Pin description of LCC-V package 38

Design Phase Report 2013 MEMS based Digital Gyroscope

Dept. of ECE 1 MACE, Venjaramoodu

CHAPTER 1

INTRODUCTION

The properties of gyroscopes can be found in heavenly bodies in motion, artillery

projectiles in motion, turbine rotors, different mobile installations on ships, aircraft

propeller rotating, etc. The modern technique of gyroscopes is an essential element of

powerful gyroscopic devices and accessories used for the automatic control of the

movement of aircraft, missiles, ships, torpedoes, etc. They are used in navigation to

stabilize the movement of ships in a seaway, to change their direction or the direction of

angular and translatory velocity projectiles, and for many other special purposes. There

are many devices applied in the military, and their design is based on the principles of

gyroscopes. Technical applications of gyros today are so manifold and diverse that there

is a need to get out of the general theory of gyroscopes and to allocate a separate

discipline called "applied theory of gyroscopes." A gyroscope is a part of many scientific

and transportation-related instruments including compasses, mechanisms that steer

torpedoes toward their targets, equipment that keeps large ships such as aircraft carriers

from rolling on the waves, automatic pilots on airplanes and ships as well as systems that

guide missiles and spacecraft, relative to the Earth (i.e., inertial guidance systems).

The characteristic of the gyroscope to keep the direction was used in many fields

of mechanical engineering, mining, aviation, navigation, military industry and celestial

mechanics. Gyroscopes are very important parts of instruments for aircraft, rockets,

missiles, transport vehicles and many weapons. This gives them a significant role and

needs to be under the strict control of the design and inner functioning because in case of

damage it could lead to catastrophic consequences. A gyroscope (gyro, top) is a

homogeneous, axis-symmetric rotating body that rotates at high angular velocity about its

axis of symmetry. Today, it is one of the most important inertial sensors measuring

angular velocities and small angular disturbances or angular displacement around the

reference axis. Gyroscopes for measuring angular velocity are called rate gyroscopes, and



when they measure small angular disturbances they are called rate integrating

gyroscopes.

This design phase project report deals with the origin and history of gyroscopes. It

then goes on to various types of gyroscopes presently used. One of the primarily and

widely used gyroscopes are mechanical gyroscopes. This report then discuss upon the

MEMS gyroscope which is finding applications in many sophisticated fields. The

fabrication and packaging challenges of MEMS gyroscopes are also discussed.

This project use MEMS gyroscope in a spinning sounding rocket to measure its

spin rate. The report then explains about sounding rockets and why spinning is essential

for a rocket. It then explains the typical block diagrammatic representation of the

intended project. Finally the description of various components used in the project is

briefly explained.



CHAPTER 2

HISTORY OF GYROSCOPES

In early times, people discovered the spinning top, a toy with a unique ability to

balance upright while rotating rapidly. Ancient Greek, Chinese and Roman societies built

tops for games and entertainment. The Maori in New Zealand have used humming tops,

with specially-crafted holes, in mourning ceremonies. In 14th century England, some

villages had a large top constructed for a warming-up exercise in cold weather. Tops

were even used in place of dice, like the die in the contemporary fantasy game Dungeons

& Dragons. It was not until the late 18th and early 19th centuries that scientists and

sailors began attempting to use spinning tops as a scientific tool. At that time, sailors

relied on sextants for navigation, measuring the angle between specific stars and the

horizon. This method was limited, however, if choppy seas or fog obscured the true

horizon, or clouds obscured the stars.

Serson, an English scientist, noted in the 1740's that the spinning top had a

tendency to remain level, even when the surface on which it rested was tilting. He

suggested that sailors could use it as an artificial horizon on ships. Unfortunately, when

Serson went to sea to test this idea the ship sank and everyone was lost. A French

scientist in the 19th Century, Fleuriais, created a top that was continuously powered by

air jets blowing into mini-buckets on the rim of the wheel - a process that has been used

for thousands of gyros since.

The first modern gyroscope was designed in 1810 by G.C. Bohnenberger. It was

made with a heavy ball instead of a wheel, but since it had no scientific application, it

faded into history. In the mid-19th century, the spinning top acquired the name,

"gyroscope," though not through its use as a navigation tool. French scientist Leon

Foucault had experimented with a long, heavy pendulum in an attempt to observe the

rotation of the Earth. The pendulum was set swinging back and forth along the north-

south plane, while the Earth turned beneath it.



Foucault corroborated the observation by using a spinning top in a similar

manner. He placed a wheel, rotating at high-speed, in a supporting ring in such a way that

the axis of the spinning wheel could move independently of the ring. In fact, the

supporting ring moved over the course of a day, as it was connected to the surface of the

rotating Earth. The axis of the wheel remained pointed in its original direction,

confirming that the Earth was rotating in a twenty-four hour period. Foucault named his

spinning wheel a "gyroscope", from the Greek words "gyros" (revolution) and "skopein"

(to see); he had seen the revolution of the Earth with his gyroscope. Fifty years later

(1898) Austrian Ludwig Obry patented a torpedo steering mechanism based on

gyroscopic inertia. It consisted of a little bronze wheel weighing less than 1.5 pounds that

was spun by an air jet.

Fig 2.1 An earlier Gyroscope

In the 1860s, the advent of electric motors made it possible for a gyroscope to

spin indefinitely; this led to the first prototype heading indicators and, quite more

complicated devices, first gyrocompasses. The first functional gyrocompass was patented

in 1904 by German inventor Hermann Anschütz-Kaempfe. The American Elmer Sperry

followed with his own design later that year, and other nations soon realized the military

http://en.wikipedia.org/wiki/Heading_indicator

http://en.wikipedia.org/wiki/Gyrocompass

http://en.wikipedia.org/wiki/Hermann_Anschütz-Kaempfe

http://en.wikipedia.org/wiki/Elmer_Sperry



importance of the invention—in an age in which naval prowess was the most significant

measure of military power—and created their own gyroscope industries. The Sperry

Gyroscope Company quickly expanded to provide aircraft and naval stabilizers as well,

and other gyroscope developers followed suit.

In 1917, the Chandler Company of Indianapolis, created the "Chandler

gyroscope", a toy gyroscope with a pull string and pedestal. Chandler continued to

produce the toy until the company was purchased by TEDCO inc. in 1982. The chandler

toy is still produced by TEDCO today.

In the first several decades of the 20th century, other inventors attempted

(unsuccessfully) to use gyroscopes as the basis for early black box navigational systems

by creating a stable platform from which accurate acceleration measurements could be

performed (in order to bypass the need for star sightings to calculate position). Similar

principles were later employed in the development of inertial guidance systems for

ballistic missiles.

During World War II, the gyroscope became the prime component for aircraft and

anti-aircraft gun sights. After the war, the race to miniaturize gyroscopes for guided

missiles and weapons navigation systems resulted in the development and manufacturing

of so-called midget gyroscopes that weighed less than 85g and had a diameter of

approximately 2.5 cm. Some of these miniaturize gyroscopes could reach a speed of

24,000 revolutions per minute in less than 10 seconds.

In the early 20th Century, Elmer A. Sperry developed the first automatic pilot for

airplanes using a gyroscope, and installed the first gyrostabilizer to reduce roll on ships.

While gyroscopes were not initially very successful at navigating ocean travel, navigation

is their predominant use today. They can be found in ships, missiles, airplanes, the Space

Shuttle, and satellites.

3-axis MEMS-based gyroscopes are also being used in portable electronic devices

such as Apple's current generation of iPad, iPhone and iPod touch. This adds to the 3-

axis acceleration sensing ability available on previous generations of devices. Together

these sensors provide 6 component motion sensing; acceleration for X, Y, and Z

http://en.wikipedia.org/wiki/Sperry_Gyroscope_Company

http://en.wikipedia.org/wiki/Sperry_Gyroscope_Company

http://en.wikipedia.org/wiki/Indianapolis

http://en.wikipedia.org/wiki/Black_box_(systems)

http://en.wikipedia.org/wiki/Inertial_guidance_system

http://en.wikipedia.org/wiki/Ballistic_missile

http://en.wikipedia.org/wiki/IPod_touch



movement, and gyroscopes for measuring the extent and rate of rotation in space (roll,

pitch and yaw).

A gyroscope exhibits a number of behaviors including precession and nutation.

Gyroscopes can be used to construct gyrocompasses, which complement or replace

magnetic compasses (in ships, aircraft and spacecraft, vehicles in general), to assist in

stability (Hubble Space Telescope, bicycles, motorcycles, and ships) or be used as part of

an inertial guidance system. Gyroscopic effects are used in tops, boomerangs, yo-yos, and

Powerballs. Many other rotating devices, such as flywheels, behave in the manner of a

gyroscope, although the gyroscopic effect is not being used.

Gravity Probe B has made one of the most sophisticated and accurate gyroscopes

in the world to measure the shape and motion of local space time. Yet, their gyroscopes

have much in common with the simplest toy tops that children have played with for

centuries. The spinning top retains its balance through a physical phenomenon called

"precession". Without this phenomenon, there would be no toy tops or Gravity Probe B.

Fig 2.2 Gyroscope housing of Gravity Probe B

http://en.wikipedia.org/wiki/Precession

http://en.wikipedia.org/wiki/Nutation

http://en.wikipedia.org/wiki/Gyrocompass

http://en.wikipedia.org/wiki/Hubble_Space_Telescope

http://en.wikipedia.org/wiki/Powerball_(toy)

http://en.wikipedia.org/wiki/Flywheel

http://solarsystem.nasa.gov/scitech/images/inset-20050314-327-5-large.jpg



A gyroscope is a device for measuring or maintaining orientation, based on the

principles of angular momentum. Mechanically, a gyroscope is a spinning wheel or disc

in which the axle is free to assume any orientation. Although this orientation does not

remain fixed, it changes in response to an external torque much less and in a different

direction than it would without the large angular momentum associated with the disc's

high rate of spin and moment of inertia. The device's orientation remains nearly fixed,

regardless of the mounting platform's motion, because mounting the device in a gimbal

minimizes external torque.

Gyroscopes based on other operating principles also exist, such as the electronic,

microchip-packaged MEMS gyroscope devices found in consumer electronic devices,

solid-state ring lasers, fiber optic gyroscopes, and the extremely sensitive quantum

gyroscope.

Applications of gyroscopes include inertial navigation systems where magnetic

compasses would not work (as in the Hubble telescope) or would not be precise enough

(as in ICBMs), or for the stabilization of flying vehicles like radio-controlled helicopters

or unmanned aerial vehicles. Due to their precision, gyroscopes are also used in gyro

theodolites to maintain direction in tunnel mining.



http://en.wikipedia.org/wiki/Torque

http://en.wikipedia.org/wiki/Rotation

http://en.wikipedia.org/wiki/Moment_of_inertia

http://en.wikipedia.org/wiki/Gimbal

http://en.wikipedia.org/wiki/MEMS_gyroscope

http://en.wikipedia.org/wiki/Ring_laser_gyroscope

http://en.wikipedia.org/wiki/Fibre_optic_gyroscope

http://en.wikipedia.org/wiki/Quantum_gyroscope

http://en.wikipedia.org/wiki/Quantum_gyroscope

http://en.wikipedia.org/wiki/Inertial_navigation_system

http://en.wikipedia.org/wiki/Hubble_telescope

http://en.wikipedia.org/wiki/ICBM

http://en.wikipedia.org/wiki/Unmanned_aerial_vehicle

http://en.wikipedia.org/wiki/Gyrotheodolite

http://en.wikipedia.org/wiki/Gyrotheodolite



CHAPTER 3

TYPES OF GYROSCOPES

3.1 Mechanical Gyroscope

The mechanical gyroscope, a well-known and reliable rotation sensor based on

the inertial properties of a rapidly spinning rotor, has been around since the early 1800s.

The first known gyroscope was built in 1810 by G.C Bohnenberger of Germany. In 1852,

the French physicist Leon Foucault showed that a gyroscope could detect the rotation of

the earth. Within mechanical systems or devices, a conventional gyroscope is a

mechanism comprising a rotor journal led to spin about one axis, the journals of the rotor

being mounted in an inner gimbal or ring; the inner gimbal is journal led for oscillation in

an outer gimbal for a total of two gimbals. The outer gimbal or ring, which is the

gyroscope frame, is mounted so as to pivot about an axis in its own plane determined by

the support. This outer gimbal possesses one degree of rotational freedom and its axis

possesses none. The next inner gimbal is mounted in the gyroscope frame (outer gimbal)

so as to pivot about an axis in its own plane that is always perpendicular to the pivotal

axis of the gyroscope frame (outer gimbal). This inner gimbal has two degrees of

rotational freedom.

Fig 3.1: Mechanical Gyroscope

http://en.wiktionary.org/wiki/rotor

http://en.wikipedia.org/wiki/Coordinate_axis

http://en.wikipedia.org/wiki/Journal_(mechanics)




3.2 Piezoelectric Gyroscope Piezoelectric vibrating gyroscopes use Coriolis forces to measure rate of rotation.

In one typical design three piezoelectric transducers are mounted on the three sides of a

triangular prism. If one of the transducers is excited at the transducer's resonance

frequency (in the Gyrostat it is 8 kHz), the vibrations are picked up by the two other

transducers at equal intensity. When the prism is rotated around its longitudinal axis, the

resulting Coriolis force will cause a slight difference in the intensity of vibration of the

two measuring transducers. The resulting analog voltage difference is an output that

varies linearly with the measured rate of rotation.

Fig 3.2: Piezoelectric Gyroscope

3.3 Optical Gyroscope Optical rotation sensors have now been under development as replacements for

mechanical gyros for over three decades. With little or no moving parts, such devices are

virtually maintenance free and display no gravitational sensitivities, eliminating the need

for gimbals. Fueled by a large market in the automotive industry, highly linear fiber-optic

versions are now evolving that have wide dynamic range and very low projected costs.

The basic device consists of two laser beams traveling in opposite directions (counter

propagating) around a closed-loop path. The constructive and destructive interference

patterns formed by splitting off and mixing parts of the two beams can be used to

determine the rate and direction of rotation of the device itself.



Fig 3.3: Optical Gyroscopes

3.4 Active Ring Laser Gyroscope The active optical resonator configuration, more commonly known as the ring

laser gyro, solves the problem of introducing light into the doughnut by filling the cavity

itself with an active lazing medium, typically helium-neon. There are actually two beams

generated by the laser, which travel around the ring in opposite directions. If the gyro

cavity is caused to physically rotate in the counterclockwise direction, the

counterclockwise propagating beam will be forced to traverse a slightly longer path than

under stationary conditions. Similarly, the clockwise propagating beam will see its

closed-loop path shortened by an identical amount. This phenomenon, known as the

Sagnac effect, in essence changes the length of the resonant cavity.

3.5 Passive Ring Resonator Gyroscope

The passive ring resonator gyro makes use of a laser source external to the ring

cavity, and thus avoids the frequency lock-in problem which arises when the gain

medium is internal to the cavity itself. The passive configuration also eliminates

problems arising from changes in the optical path length within the interferometer due to

variations in the index of refraction of the gain medium. The theoretical quantum noise

limit is determined by photon shot noise and is slightly higher (worse) than the theoretical

limit seen for the active ring-laser gyroscope. The fact that these devices use mirrored



resonators patterned after their active ring predecessors means that their packaging is

inherently bulky. However, fiber-optic technology now offers a low volume alternative.

The fiber-optic derivatives also allow longer length multi-turn resonators, for increased

sensitivity in smaller, rugged, and less expensive packages.

3.6 Closed-Loop Interferometric Fiber Optic Gyroscope

This new implementation of a fiber-optic gyro provides feedback to a frequency

or phase shifting element. The use of feedback results in the cancellation of the

rotationally induced Sagnac phase shift. However, closed-loop digital signal processing is

considerably more complex than the analog signal processing employed on open-loop

IFOG configurations. It now seems that the additional complexity is justified by the

improved stability of the gyroscope closed-loop IFOGs are now under development with

drifts in the 0.001 to 0.01°/ hour range, and scale-factor stabilities greater than 100 ppm

(parts per million).

3.7 Dynamically Tuned Gyroscope

A dynamically tuned gyroscope (DTG) is a rotor suspended by a universal joint

with flexure pivots. The flexure spring stiffness is independent of spin rate. However, the

dynamic inertia (from the gyroscopic reaction effect) from the gimbal provides negative

spring stiffness proportional to the square of the spin speed. Therefore, at a particular

speed, called the tuning speed, the two moments cancel each other, freeing the rotor from

torque, a necessary condition for an ideal gyroscope.

3.8 London Movement Gyroscope

A London moment gyroscope relies on the quantum-mechanical phenomenon,

whereby a spinning superconductor generates a magnetic field whose axis lines up

exactly with the spin axis of the gyroscopic rotor. A magnetometer determines the

orientation of the generated field, which is interpolated to determine the axis of rotation.

Gyroscopes of this type can be extremely accurate and stable. For example, those used in

the Gravity Probe B experiment measured changes in gyroscope spin axis orientation to

http://en.wikipedia.org/wiki/London_moment

http://en.wikipedia.org/wiki/Quantum-mechanical

http://en.wikipedia.org/wiki/Phenomenon


http://en.wikipedia.org/wiki/Superconductor

http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Axis_of_symmetry

http://en.wikipedia.org/wiki/Magnetometer

http://en.wikipedia.org/wiki/Interpolation

http://en.wikipedia.org/wiki/Gravity_Probe_B



better than 0.5milli arc seconds (1.4×10−7 degrees) over a one-year period. This is

equivalent to an angular separation the width of a human hair viewed from 32 kilometers

away.

The GP-B gyroscope consists of a nearly-perfect spherical rotating mass made of

fused quartz, which provides a dielectric support for a thin layer of niobium

superconducting material. To eliminate friction found in conventional bearings, the rotor

assembly is centered by the electric field from six electrodes. After the initial spin-up by

a jet of helium which brings the rotor to 4,000 RPM, the polished gyroscope housing is

evacuated to an ultra-high vacuum to further reduce drag on the rotor. Provided the

suspension electronics remain powered, the extreme rotational symmetry, lack of friction,

and low drag will allow the angular momentum of the rotor to keep it spinning for about

15,000 years.

3.9 MEMS Gyroscope

A MEMS gyroscope takes the idea of the Foucault pendulum and uses a vibrating

element, known as MEMS (Micro Electro-Mechanical System). The MEMS-based gyro

was initially made practical and producible by Systron Donner Inertial (SDI). Today, SDI

is a large manufacturer of MEMS gyroscopes. Inexpensive vibrating structure gyroscopes

manufactured with MEMS technology have become widely available. These are

packaged similarly to other integrated circuits and may provide either analog or digital

outputs. In many cases, a single part includes gyroscopic sensors for multiple axes. Some

parts incorporate multiple gyroscopes and accelerometers or multiple axis gyroscopes and

accelerometers, to achieve output that has six full degrees of freedom. These units are

called inertial measurement units, or IMUs.

http://en.wikipedia.org/wiki/Minute_of_arc

http://en.wikipedia.org/wiki/Angular_separation

http://en.wikipedia.org/wiki/Gravity_Probe_B

http://en.wikipedia.org/wiki/Moment_of_inertia#Rotational_symmetry

http://en.wikipedia.org/wiki/Fused_quartz

http://en.wikipedia.org/wiki/Dielectric

http://en.wikipedia.org/wiki/Niobium

http://en.wikipedia.org/wiki/Superconductor

http://en.wikipedia.org/wiki/Angular_acceleration

http://en.wikipedia.org/wiki/Revolutions_per_minute

http://en.wikipedia.org/wiki/Rotational_symmetry

http://en.wikipedia.org/wiki/MEMS_gyroscope

http://en.wikipedia.org/wiki/Foucault_pendulum

http://en.wikipedia.org/wiki/Microelectromechanical_systems

http://en.wikipedia.org/w/index.php?title=Systron_Donner_Inertial&action=edit&redlink=1

http://en.wikipedia.org/wiki/Microelectromechanical_systems

http://en.wikipedia.org/wiki/Integrated_circuit

http://en.wikipedia.org/wiki/Accelerometers

http://en.wikipedia.org/wiki/Accelerometers

http://en.wikipedia.org/wiki/Inertial_measurement_unit



CHAPTER 4

MECHANICAL GYROSCOPE

A gyroscope is defined as a rigid rotating object, symmetric about one axis.

Generations of children, back at least to Greek antiquity, have found fascination in the

behavior of tops, to give the gyroscope its common name. A number of eminent

physicists have also found the complex behavior of spinning objects a matter of interest

and a fit subject for detailed analysis. More recently, very carefully engineered

gyroscopes were used for navigation because the axis of spin points in a nearly fixed

direction when external torques is small. This makes the gyroscope a good replacement

for a magnetic compass, particularly in regions where magnetic compasses are unreliable.

To start the gyroscope, let us hold the axis fixed and set the rate of spin to the

desired value. The axis then moved at the precession speed and released, the motion will

be a smooth precession. If, instead, the axis is released from rest the tip will trace out

small 'scallop' or looping motions, superimposed on the overall precession. This is called

nutation, and arises from conservation of mechanical energy. The precessional motion

represents additional kinetic energy, relative to the state with the axis fixed. Since ω is

constant (frictionless bearing), the additional kinetic energy must come from a loss of

gravitational potential. In other words, the center of mass must fall a little bit, tipping the

axis of rotation, in order for the top to precess. If the spin is rapid, the drop is small, and

the precession is affected only slightly. Overall, the tip of the axis bounces up and down a

little, and the precessional speed varies a little. If the spin is not fast enough then the

character of the motion changes drastically, but that is a complicated story.

4.1 Space Stable Gyroscopes

The earth’s rotational velocity at any given point on the globe can be broken into

two components: one that acts around an imaginary vertical axis normal to the surface,

and another that acts around an imaginary horizontal axis tangent to the surface. These

two components are known as the vertical earth rate and the horizontal earth rate,



respectively. At the North Pole, for example, the component acting around the local

vertical axis (vertical earth rate) would be precisely equal to the rotation rate of the earth,

or 15°/hr. The horizontal earth rate at the pole would be zero. As the point of interest

moves down a meridian toward the equator, the vertical earth rate at that particular

location decreases proportionally to a value of zero at the equator. Meanwhile, the

horizontal earth rate, (i.e., that component acting around a horizontal axis tangent to the

earth’s surface) increases from zero at the pole to a maximum value of 15°/hour at the

equator. There are two basic classes of rotational sensing gyros:

1) Rate gyros, which provide a voltage or frequency output signal

proportional to the turning rate, and

2) Rate integrating gyros, which indicate the actual turn angle.

A typical gyroscope configuration is shown below. The electrically driven rotor is

suspended in a pair of precision low-friction bearings at either end of the rotor axle. The

rotor bearings are in turn supported by a circular ring, known as the inner gimbal ring;

this inner gimbal ring pivots on a second set of bearings that attach it to the outer gimbal

ring. This pivoting action of the inner gimbal defines the horizontal axis of the gyro,

which is perpendicular to the spin axis of the rotor as shown. The outer gimbal ring is

attached to the instrument frame by a third set of bearings that define the vertical axis of

the gyro.

Fig 4.1 Two axis mechanical gyroscopes



The vertical axis is perpendicular to both the horizontal axis and the spin axis.

Notice that if this configuration is oriented such that the spin axis points east-west, the

horizontal axis is aligned with the north-south meridian. Since the gyro is space-stable

(i.e., fixed in the inertial reference frame), the horizontal axis thus reads the horizontal

earth rate component of the planet’s rotation, while the vertical axis reads the vertical

earth rate component. If the spin axis is rotated 90 degrees to a north-south alignment, the

earth’s rotation does not affect the gyro’s horizontal axis, since that axis is now

orthogonal to the horizontal earth rate component.

4.2 Gyrocompasses

The gyrocompass is a special configuration of the rate integrating gyroscope,

employing a gravity reference to implement a north-seeking function that can be used as

a true-north navigation reference. This phenomenon, first demonstrated in the early 1800s

by Leon Foucault, was patented in Germany by Herman Anschutz-Kaempfe in 1903 and

in the U.S. by Elmer Sperry in 1908. The U.S. and German navies had both introduced

gyrocompasses into their fleets by 1911. The north-seeking capability of the gyrocompass

is directly tied to the horizontal earth rate component measured by the horizontal axis. As

mentioned earlier, when the gyro spin axis is oriented in a north-south direction, it is

insensitive to the earth's rotation, and no tilting occurs. From this it follows that if tilting

is observed, the spin axis is no longer aligned with the meridian. The direction and

magnitude of the measured tilt are directly related to the direction and magnitude of the

misalignment between the spin axis and true north.

Numerous mechanical gyroscopes are available on the market. Typically, these

precision machined gyros can cost between $10,000 and $100,000. Lower cost

mechanical gyros are usually of lesser quality in terms of drift rate and accuracy.

Mechanical gyroscopes are rapidly being replaced by modern high-precision — and

recently — low-cost fiber-optic gyroscopes. MEMS based gyroscopes are also being

widely used due to their small size at the tradeoff in precision.



CHAPTER 5

THE CORIOLIS FORCE

It is observed that the sun moves across our sky, having risen in the east, bound to

set in the west. As a consequence, the amount of solar radiation received at the surface

varies during the calendar day, reaching a peak around local noon, being entirely absent

at night. The diurnal variation of heating drives local circulations, such as the sea- and

land-breeze. Striking optical phenomena like red suns and green flashes occur when the

sun is low in our sky. These phenomena are very real.

However, if interpreting the sun’s motion as being due to its rotation about the

Earth, our underlying explanation for these real effects is flat-out wrong. Of course, we

appreciate that we are moving and not the sun. However, rapid as it is we cannot sense

the Earth’s rotation, and so it’s just easier to pretend the sun is doing the moving. That is

strictly an apparent, though very convincing motion. Importantly, our misinterpretation

has no bearing on the phenomena described above. They are still real, even if our

explanation for them is merely convenient and self-serving. The same holds true for the

phenomena for which we credit (or blame) the Coriolis force.

These include the facts that the large-scale wind does not blow directly from high

to low pressure; that principal northern hemisphere (NH) surface ocean currents are

clockwise (CW); that winds tend to blow from the west in mid-latitudes, as well as from

the east and the northeast in the polar and tropical latitudes, respectively; and that mid-

latitude and tropical cyclones (hurricanes) can and do form, but with the latter never

appearing directly on the equator. These are real and very important effects, which we

usually explain through the agency of the Coriolis force. At worst, that’s just lazy

thinking, nothing more, similar to our other convenient fiction regarding air temperature

and water vapor holding capacity. At best, it helps us explain what we ourselves observe,

and in the simplest possible terms. The Coriolis force helps us make sense of what we

sense.



Newton’s first law of motion presents a simple yet very powerful constraint on

motions. It states that an object, once put into motion, continues moving in a straight line

and at constant speed unless other forces are acting. By that same token, if we see

something curve, then it follows there must be a force impelling this deviation from

straight-line motion. Note this well: if we see something curve, we have to explain the

curvature. We have to identify a force. Consider a rocket put into motion on the rotating

Earth. We are observers located on that spinning sphere. Once launched, we see the

rocket start curving, and we give the force causing that curvature a name: the Coriolis

force. That Coriolis force is acting to the object’s right, following its motion. Thus, if we

launch the rocket northward, it cannot continue traveling due north. Instead, we see it

start curving eastward, the direction to the object’s right. The deflection does not stop

there. Once eastbound, the Coriolis force works to bend the object to the south. Once

southbound, Coriolis encourages a westward deflection. Finally, the westbound rocket

starts curving towards the north, the direction we wanted it to travel in the first place. The

object is has begun describing circles, called Coriolis or inertial circles.

However, the rocket didn’t actually curve at all. The rocket was launched and

allowed the go on its merry way. No other forces have actually intervened. Thus, the

rocket went straight, as Newton’s first law insisted it must. Yet, it is seen to curve. There

is only one solution to this: if the rocket didn’t turn, we did.

Although the meteorological science enjoys a relative wealth of colorful figures

and events, from past and present, the educators rarely make use of this historical

dimension, as was recently pointed out in this journal by Knox and Croft (1997). A case

where a historical approach proves to be illuminating is in the teaching of the Coriolis

force, named after French mathematician Gaspard Gustave Coriolis (1792 – 1843). On a

rotating earth the Coriolis force acts to change the direction of a moving body to the right

in the Northern Hemisphere and to the left in the Southern Hemisphere.



CHAPTER 6

MEMS GYROSCOPE

Gyroscopes have played an important role in aviation, space exploration and

military applications. Until recently, high cost and large size made their use in

automobiles and other consumer products prohibitive. With the advent of Micro- Electro-

Mechanical Systems (MEMS), gyroscopes and other inertial measurement devices can

now be produced cheaply and in very small packages in the micro domain. An example

of this are the MEMS accelerometers now used in some automobiles to detect collisions

for air bag deployment. In order to estimate the absolute angle θ, with a traditional

MEMS rate-gyroscope, one would have to integrate the angular rate signal Ω with respect

to time. The problem with this method is that bias errors in the angular rate signal from

the gyroscope will inevitably cause the integrated angle value to drift over time, since all

gyroscopes have at least a small amount of bias error in their angular rate signal. This

paper develops a sensor design to directly measure absolute angle. The design can also be

combined with traditional angular rate measurement to provide a sensor in an integrated

package that measures both angle and angular rate.

There are a large number of applications where a gyroscope that can measure

angle would be useful. A common application is measurement of the heading or

orientation of a highway vehicle. The measurement of orientation is useful in computer-

controlled steering of the vehicle as well as in differential braking systems being

developed by automotive manufacturers for vehicle skid control. An important additional

benefit of the proposed design is that it would also contribute towards improving the

accuracy of the regular rate gyroscopes. The proposed design is novel in that it breaks

new ground by introducing sophisticated control systems into the MEMS domain. It is

the use of advanced control techniques that leads to a new sensor making the

measurement of a new variable possible.



Gyroscopes are physical sensors that detect and measure the angular motion of an

object relative to an inertial frame of reference. The term "Gyroscope" is attributed to the

mid-19th century French physicist Leon Foucault who named his experimental apparatus

for Earth's rotation observation by joining two Greek roots: gyros - rotation and skopeein-

to see. Unlike rotary encoders or other sensors of relative angular motion, the unique

feature of gyroscopes is the ability to measure the absolute motion of an object without

any external infrastructure or reference signals. Gyroscopes allow untethered tracking of

an object's angular motion and orientation and enable standalone Heading Reference

Systems (AHRS).

MEMS vibratory gyroscopes measure rotation rate by vibrating a proof-mass and

sensing the Coriolis force caused by angular velocity. Beyond the goal of making a

vibrating structure that gives rise to a Coriolis force, the true goals of the gyro transducer

are to minimize the error sources that corrupt the Coriolis signal and to simplify the IC

architecture. The former is achieved by a design that minimizes Brownian noise, rejects

external vibrations, survives shock, rejects package stresses, and minimizes cross-axis

sensitivity. The latter is achieved by a design that has high transducer sensitivity, minimal

quadrature, carefully designed resonant modes, and minimal parasitic capacitance.

All InvenSense X- and Y-axis gyroscopes are based on coupled dual-mass (tuning

fork) proof-masses that are driven out-of-plane and generate Coriolis forces in-plane, as

shown in Figure 6.1. The vibration mode consists of a five-mass system. The two proof-

masses translate out-of-plane coupled together through lever arms connected to three

separate torsion plates. The torsion plates are mounted on springs that act as pivot points,

which is the key to achieve vertical motion using thick silicon. Aluminum electrodes on

the IC are located under the torsion plates forming parallel-plate electrodes that can exert

torque on the torsion plates for actuation and detect the torsion plate angle for feedback to

resonate and provide amplitude control.



Figure 6.1: X-axis gyroscope driven mode

The coupled mass system is essential for rejecting external vibrations because the

design is fully balanced and therefore does not move in response to linear acceleration.

However, the first generation gyroscopes, which operated in the 12 kHz to 15 kHz range,

were found to respond to acoustic interference. Later generation gyros were designed to

operate in the 25 kHz to 30 kHz range to avoid interference from sound and other

ambient sources of noise found in consumer applications.

The key to reducing size has been to improve the Coriolis sensing system. In the

first generation sensors, the three torsion plates were connected to a sensing frame. The

sensing frame was suspended such that it could only rotate. The Coriolis forces from the

proof-masses created a torque that rotated the ring in plane. Motion of the ring was

detected by capacitive combs. The full scale angular rate in image stabilization generated

merely ~1Å of mechanical deflection of the sensing frame. Sensing the deflection

required lots of capacitive combs and low-noise electronics.

In the next generation gyroscope in-which the two outer torsion plates are

anchored to the substrate, and the center torsion plate is flexibly connected to the sense



frame. By flexibly connecting the drive system and sense system, two resonant modes are

created, and the drive resonant frequency is in the middle. This introduced several

benefits including lower sensitivity variation as well as 2x higher mechanical sensitivity.

The design improvement resulted in smaller MEMS that met the same performance with

higher resonant frequency to avoid the audio range. In the third and current generation,

the sense frame was further optimized into a four-bar linkage. The Coriolis torque moves

the four-bar linkage which is sensed in-plane using capacitive electrodes, as shown in

Figure 6.2. The four-bar linkage has lower inertia than the corresponding rigid frame

structure of the past. This generation also anchors the structure at two points which

minimizes sensitivity to any stress associated with conventional QFN plastic packages.

Fig 6.2 X axis Gyroscope

Z-axis gyroscope consists of two proof-masses that are resonated in-plane as

shown in Figure 6.3. The proof-masses are flexibly coupled and resonate in a differential

mode. The proof-masses can move in two directions but the actuation structures are

constrained to move only in the drive direction. The Z-axis gyroscope also uses dual-

mode sensing. The proof-masses are flexibly coupled to the sense frame and the resulting

Coriolis torque moves the sense frame similar to the X and Y gyroscopes. In this manner,

the Z-axis gyroscope is able to leverage the entire sense-system mechanics and



electronics developed for the X-and-Y sensor. In fact, the first generation Z-gyro simply

replaced the Y-gyro drive masses with proof-masses that are driven in-plane, enabling

rapid development.

Fig 6.3: Z Gyroscope

Vibrating-Wheel Gyroscopes have a wheel that is driven to vibrate about its axis

of symmetry, and rotation about either in-plane axis results in the wheel’s tilting, a

change that can be detected with capacitive electrodes under the wheel, Figure 3. It is

possible to sense two axes of rotation with a single vibrating wheel. A surface micro

machined polysilicon vibrating wheel gyro, Figure 6.4, has been designed at the U.C.

Berkeley Sensors and Actuators Center that demonstrated this capability.

Fig 6.4 Vibration Gyroscope



6.1 Challenges in Fabrication

Fig 6.5 various design options

Gyroscopes are much more challenging sensor products than acceleration

or pressure sensors. Gyroscopes are basically two high performing MEMS devices

integrated into one single device that have to work together to produce results. They are a

self-tuned resonator in the drive axis and a micro-g sensor in the sensing axis. The

absolute magnitude of the Coriolis force sensed is orders of magnitude lower than any

high volume production MEMS accelerometer. Capacitive sensors are generally used for

measuring these small changes of capacitance. Gyroscope performance is very sensitive

to all potential manufacturing variations, packaging, linear acceleration, temperature, etc.

To achieve high performance and low cost, lots of care must be taken during the initial



design. Gyroscope designers must achieve a solution that can be insensitive to most of

these potential variations. Figure 6.5 shows the various possible combinations of

fabricating MEMS gyroscopes.

6.2 Challenges in Packaging One of the most difficult decisions that can have the biggest effect on the

cost is the choice for the final package. Generally, packaging is one of the highest

components of the final cost for most types of MEMS sensors. In majority of cases,

sensor designers and MEMS experts are not packaging experts. MEMS designers are

primarily focused on the design and development of the sensor element, with the

objective of demonstrating performance on the bench. The task of taking the MEMS

sensor element and package it is the packaging engineer’s problem. In order to have the

lowest cost MEMS product packaging issues must be addressed up front in the initial

phase of design cycle.

Fig 6.6 MEMS Gyroscope Products



CHAPTER 7

SOUNDING ROCKETS

A sounding rocket, sometimes called a research rocket, is an instrument-carrying

rocket designed to take measurements and perform scientific experiments during its sub-

orbital flight. The rockets are used to carry instruments from 50 to 1,500 kilometers

above the surface of the Earth, the altitude generally between weather balloons and

satellites (the maximum altitude for balloons is about 40 kilometers and the minimum for

satellites is approximately 120 kilometers). Certain sounding rockets, such as the Black

Brant X and XII, have an apogee between 1,000 and 1,500 kilometers. Sounding rockets

often use military surplus rocket motors. NASA routinely flies the Terrier Mk 70 boosted

Improved Orion lifting 270–450 kilograms payloads into the exo-atmospheric region

between 100 and 200 kilometers.

The origin of the term comes from nautical vocabulary to sound, which is to

throw a weighted line from a ship into the water to measure the water's depth. The term

itself has its etymological roots in the Spanish and French word for probe, which is

"sonda" or "sonde", respectively. Sounding in the rocket context is equivalent to taking a

measurement.

A common sounding rocket consists of a solid-fuel rocket motor and a science

payload. The free fall part of the flight is an elliptic trajectory with vertical major axis

allowing the payload to appear to hover near its apogee. The average flight time is less

than 30 minutes, usually between five and 20 minutes. The rocket consumes its fuel on

the first stage of the rising part of the flight, then separates and falls away, leaving the

payload to complete the arc and return to the ground under a parachute.

Sounding rockets are advantageous for some research due to their low cost, short

lead time (sometimes less than six months) and their ability to conduct research in areas

inaccessible to either balloons or satellites. They are also used as test beds for equipment

that will be used in more expensive and risky orbital spaceflight missions. The smaller

http://en.wikipedia.org/wiki/Rocket

http://en.wikipedia.org/wiki/Sub-orbital_spaceflight

http://en.wikipedia.org/wiki/Sub-orbital_spaceflight

http://en.wikipedia.org/wiki/Earth

http://en.wikipedia.org/wiki/Weather_balloon

http://en.wikipedia.org/wiki/Satellite

http://en.wikipedia.org/wiki/Balloon

http://en.wikipedia.org/wiki/Satellite

http://en.wikipedia.org/wiki/Black_Brant_rocket

http://en.wikipedia.org/wiki/Black_Brant_rocket

http://en.wikipedia.org/wiki/Apogee

http://en.wikipedia.org/wiki/NASA

http://en.wikipedia.org/wiki/RIM-2_Terrier

http://en.wikipedia.org/wiki/Improved_Orion

http://en.wiktionary.org/wiki/exoatmospheric

http://en.wikipedia.org/wiki/Solid-fuel_rocket

http://en.wikipedia.org/wiki/Payload_(air_and_space_craft)

http://en.wikipedia.org/wiki/Freefall

http://en.wikipedia.org/wiki/Elliptic_orbit

http://en.wikipedia.org/wiki/Semi-major_axis

http://en.wikipedia.org/wiki/Apogee

http://en.wikipedia.org/wiki/Parachute

http://en.wikipedia.org/wiki/Orbital_spaceflight



size of a sounding rocket also makes launching from temporary sites possible allowing

for field studies at remote locations, even in the middle of the ocean, if fired from a ship.

During flight, all launch vehicles are imparted with a spinning motion to reduce

potential dispersion of the flight trajectory due to vehicle misalignments. The longitudinal

and lateral loads imparted due to rocket motor thrust, aerodynamics, winds, spin rates and

abrupt changes in spin rate due to de-spin devices are major design considerations.

Unguided sounding rocket launch vehicles fly with a spinning motion to reduce the flight

trajectory dispersion due to misalignments. The effects of spin-induced loads should be

considered when components are mounted off of the spin-axis. Load factors exceeding 30

g's can be experienced by components mounted near the payload external skin for large

diameter designs. Most electronic devices utilize relatively small, lightweight circuit

boards and components. When soldering is properly performed, and a conformal coating

applied, problems caused by mechanical loads are very infrequent.

Fig 7.1: Sounding rockets



The best way to induce spin is to pre-spin the rocket prior to launch. A spinning

launch platform (some kind of turn table) would be ideal. The second best alternative

would be a helical launch tower. This kind of tower does exist, and is still used by NASA

for launches of the Super Loki Dart rocket. As the rocket rises up through the tower, the

guides induce a spin into the rocket. The faster the rocket leaves the tower, the higher the

rotation rate.

According to Newton’s first law of motion, a body in motion will remain in

motion unless acted on by some outside force. This law is also known as the law of

inertia. This case deals with the spinning motion. Once the rocket leaves the helical

tower, the spinning will continue unless some outside force acts on it. But, even a

spinning top will wind down and fall over after some time. So there must be some force

acting on it that causes it to slow down. That force is mainly friction on the point where it

touches a table. In the case of a spinning rocket, the force is aerodynamic drag.

The positive effects of spinning the rocket will probably be sufficient to keep it

going straight during that time period when the rocket is most susceptible to disturbances.

That period is when the rocket’s speed is the slowest, which is right when it leaves the

launcher. After it has built up enough speed, the fins will do a pretty good job keeping it

going relatively straight even if it does slow down or stop its spinning. For most model

rockets, we’d like the rocket to start out spinning as it leaves the launch pad, so that it has

the greatest effect at preventing weather cocking. Weather cocking usually begins when

the rocket is traveling at a slow speed. Once we the rocket gets past that critical point in

the flight, then ideally it would be desirable to de-spin it so as to lower the drag. In

rockets launched off a spin table or out of a helical tower, this will happen by itself. But

for rockets that are being designed for super high altitude flights it may be desirable that

they spin for a good portion of the flight to reduce the chances of weather cocking. In that

case, canted fins or spin tabs would have to be used.

Rotation is also used to point a nozzle of the primary propulsion system into its

intended direction just prior to its start. It can also provide for achieving flight stability,

or for correcting angular oscillations, that would otherwise increase drag or cause



tumbling of the vehicle. Spinning or rolling a vehicle will improve flight stability, but

will also average out the misalignment in a thrust vector. If the rotation needs to be

performed quickly, then a chemical multi-thruster reaction control system is used. If the

rotational changes can be done over a long period of time, then an electrical propulsion

system with multiple thrusters is often preferred.

Thus spinning is essential for a rocket to maintain its stability. It is also essential

to monitor the spinning of a spinning rocket on flight. With this we can get an idea of the

spin rate of rocket and take necessary steps to maintain the required spin rate. For

monitoring the spin rate, we have to incorporate a gyroscope into the rocket. A gyroscope

is a device for measuring or maintaining orientation, based on the principles of angular

momentum. Mechanically, a gyroscope is a spinning wheel or disc in which the axle is

free to assume any orientation. Although this orientation does not remain fixed, it

changes in response to an external torque much less and in a different direction than it

would without the large angular momentum associated with the disc's high rate of spin

and moment of inertia. The device's orientation remains nearly fixed, regardless of the

mounting platform's motion, because mounting the device in a gimbal minimizes external

torque. Mechanical gyroscopes are highly accurate but their size and weight limits their

application in rockets where size is a major concern. So we go for MEMS gyroscopes

which are very light, less costly and easy to assemble even though it is not highly

accurate.




http://en.wikipedia.org/wiki/Torque


http://en.wikipedia.org/wiki/Moment_of_inertia




CHAPTER 8

PROPOSED APPROACH

This project aims at building a MEMS based gyroscope that could be used in

spinning rockets to monitor the spinning of the rocket in its flight. It is important to

measure the spinning of the rockets as stability of the rocket in flight mainly depends on

spinning. Gyroscopes mainly measure the angular rate of spinning.

This gyroscope can also be used to measure the pitch, roll and yaw of an aircraft

or rocket or satellite in flight. For this let us know about these three parameters in detail.

Flight dynamics is the science of air vehicle orientation and control in three

dimensions. The three critical flight dynamics parameters are the angles of rotation in

three dimensions about the vehicle's center of mass, known as roll, pitch and yaw.

Aircraft engineers develop control systems for a vehicle's orientation (attitude) about its

center of mass. The control systems include actuators, which exert forces in various

directions, and generate rotational forces or moments about the center of gravity of the

aircraft, and thus rotate the aircraft in pitch, roll, or yaw. For example, a pitching moment

is a vertical force applied at a distance forward or aft from the center of gravity of the

aircraft, causing the aircraft to pitch up or down. Roll, pitch and yaw refer, in this

context, to rotations about the respective axes starting from a defined equilibrium state.

The equilibrium roll angle is known as wings level or zero bank angle, equivalent to a

level heeling angle on a ship. Yaw is known as "heading".

A fixed-wing aircraft increases or decreases the lift generated by the wings when

it pitches nose up or down by increasing or decreasing the angle of attack (AOA). The

roll angle is also known as bank angle on a fixed-wing aircraft, which usually "banks" to

change the horizontal direction of flight. An aircraft is usually streamlined from nose to

tail to reduce drag making it typically advantageous to keep the sideslip angle near zero,



though there are instances when an aircraft may be deliberately "side slipped" for

example a slip in a fixed-wing aircraft.

An aircraft in flight is free to rotate in three dimensions: pitch, nose up or down

about an axis running from wing to wing, yaw, nose left or right about an axis running up

and down; and roll, rotation about an axis running from nose to tail. The axes are

alternatively designated as lateral, vertical, and longitudinal. These axes move with the

vehicle, and rotate relative to the Earth along with the craft. These definitions were

analogously applied to spacecraft when the first manned spacecraft were designed in the

late 1950s. These rotations are produced by torques (or moments) about the principal

axes. On an aircraft, these are produced by means of moving control surfaces, which vary

the distribution of the net aerodynamic force about the vehicle's center of gravity.

Elevators (moving flaps on the horizontal tail) produce pitch, a rudder on the vertical tail

produces yaw, and ailerons (moving flaps on the wings) produce roll. On a spacecraft, the

moments are usually produced by a reaction control system consisting of small rocket

thrusters used to apply asymmetrical thrust on the vehicle.

Yaw axis is a vertical axis through an aircraft, rocket, or similar body, about

which the body yaws; it may be a body, wind, or stability axis also known as yawing

axis. The yaw axis is defined to be perpendicular to the body of the wings with its origin

at the center of gravity and directed towards the bottom of the aircraft. A yaw motion is a

movement of the nose of the aircraft from side to side. The pitch axis is perpendicular to

the yaw axis and is parallel to the body of the wings with its origin at the center of gravity

and directed towards the right wing tip. A pitch motion is an up or down movement of the

nose of the aircraft. The roll axis is perpendicular to the other two axes with its origin at

the center of gravity, and is directed towards the nose of the aircraft. A rolling motion is

an up and down movement of the wing tips of the aircraft. The rudder is the primary

control of yaw.



The lateral axis (also called transverse axis) passes through the plane from

wingtip to wingtips. Rotation about this axis is called pitch. Pitch changes the vertical

direction the aircraft's nose is pointing. The elevators are the primary control of pitch.

The longitudinal axis passes through the plane from nose to tail. Rotation about

this axis is called bank or roll. Bank changes the orientation of the aircraft's wings with

respect to the downward force of gravity. The pilot changes bank angle by increasing the

lift on one wing and decreasing it on the other. This differential lift causes bank rotation

around the longitudinal axis. The ailerons are the primary control of bank. The rudder

also has a secondary effect on bank.

Fig 8.1 Pitch Roll and Yaw Axes



8.1 Block Diagram of Project

Fig 8.2 Project Block Diagram

MEMS based gyroscopic sensor ADXRS450 is used here for measuring

the angular spinning rate of a rocket. The ADXRS450 is an angular rate sensor

(gyroscope) intended for industrial, medical, instrumentation, stabilization, and other

high performance applications. An advanced, differential, quad sensor design rejects the

influence of linear acceleration, enabling the ADXRS450 to operate in exceedingly harsh

environments where shock and vibration are present. The ADXRS450 uses an internal,

continuous self-test architecture. The integrity of the electromechanical system is

checked by applying a high frequency electrostatic force to the sense structure to generate



a rate signal that can be differentiated from the baseband rate data and internally

analyzed. The ADXRS450 is capable of sensing angular rate of up to ±300°/sec.

This family offers the same advantages of all PIC18 microcontrollers –

namely, high computational performance at an economical price – with the addition of

high endurance Enhanced Flash program memory. The PIC18FXX20 family also

provides an enhanced range of program memory options and versatile analog features

that make it ideal for complex, high-performance applications. The PIC18FXX20 family

introduces the widest range of on-chip, Enhanced Flash program memory available on

PIC micro microcontrollers – up to 128 Kbyte (or 65,536 words), the largest ever offered

by Microchip. For users with more modest code requirements, the family also includes

members with 32 Kbyte or 64 Kbyte.

PIC 18F6520 is used as master here for controlling the operations of the

gyroscope sensor ADXRS450 and to give instructions on what to do. PIC is programmed

for the required operation using C programming language and is burnt into chip after

converting it to PIC assembly language. ADXRS450 sensor act as slave here and acts

upon as instructed by the PIC microcontroller. It is a digital output gyroscope and the

corresponding digital output regarding the spinning rate is stored inside registers

available within the chip. RS232 and MAX232 are used for communicating or

transferring the values from the sensor to outside world. In this project we use Labview

software for graphical evaluation.



CHAPTER 9

HARDWARE DESCRIPTION

9.1 Sensor ADXRS450

New applications for MEMS (micro electro mechanical systems) motion sensors

are evolving in the industrial automation, medical, and instrumentation markets where

much higher performance is required than is typically found in motion sensors designed

for consumer applications. To address this growing demand for more accuracy, stability,

and high vibration and shock resistance, Analog Devices, Inc. has developed the high

performance, low power ADXRS450 iMEMS gyroscope with digital output specifically

for angular rate (rotational) sensing in harsh environments. Leveraging ADI’s previous

three generations of industry leading MEMS gyroscopes, this fourth generation device

features an advanced, differential quad sensor design that enables it to operate accurately

under intense shock and vibration conditions.

The ADXRS450 is an angular rate sensor (gyroscope) intended for industrial,

medical, instrumentation, stabilization, and other high performance applications. An

advanced, differential, quad sensor design rejects the influence of linear acceleration,

enabling the ADXRS450 to operate in exceedingly harsh environments where shock and

vibration are present. The ADXRS450 uses an internal, continuous self-test architecture.

The integrity of the electromechanical system is checked by applying a high frequency

electrostatic force to the sense structure to generate a rate signal that can be differentiated

from the baseband rate data and internally analyzed. The ADXRS450 is capable of

sensing angular rate of up to ±300°/sec. Angular rate data is presented as a 16-bit word,

as part of a 32-bit SPI message. The ADXRS450 is available in a cavity plastic 16-lead

SOIC (SOIC_CAV) and an SMT-compatible vertical mount package (LCC_V), and is

capable of operating across both a wide voltage range (3.3 V to 5 V) and temperature

range (−40°C to +105°C).



The ADXRS450 is available in two package options. The SOIC_CAV package

configuration is for applications that require a z-axis (yaw) rate sensing device. The

vertical mount package (LCC_V) option is for applications that require rate sensing in the

axes parallel to the plane of the PCB (pitch and roll).

The LCC_V package has terminals on two faces; however, the terminals on the

back side are for internal evaluation only and should not be used in the end application.

The terminals on the bottom of the package incorporate metallization bumps that ensure a

minimum solder thickness for improved solder joint reliability. These bumps are not

present on the back side terminals and, therefore, poor solder joint reliability can be

encountered if used in the end application.

Fig 9.1 SOIC-V 2 & LCC-V Package

9.1.1 SOIC-V Package details

Fig 9.2 Pin out and Application Diagram



9.1.2 Pin Description

Pin No. Mnemonic Description

1 DVDD Digital Regulated Voltage.

2 RSVD Reserved. This pin must be connected to

DVSS.

3 RSVD Reserved. This pin must be connected to DVSS.

4 CS Chip Select.

5 MISO Master In/Slave Out.

6 PDD Supply Voltage.

7 PSS Switching Regulator Ground.

8 VX High Voltage Switching Node.

9 CP5 High Voltage Supply.


11 AVSS Analog Ground.


13 DVSS Digital Signal Ground.

14 AVDD Analog Regulated Voltage.

15 MOSI Master Out/Slave In.

16 SCLK SPI Clock.

Table 9.1 Pin description of SOIC-V package



Mount the ADXRS450 in a location close to a hard mounting point of the PCB to

the case. Mounting the ADXRS450 at an unsupported PCB location (that is, at the end of

a lever, or in the middle of a trampoline) can result in apparent measurement errors

because the gyroscope is subject to the resonant vibration of the PCB. Locating the

gyroscope near a hard mounting point helps to ensure that any PCB resonances at the

gyroscope are above the frequency at which harmful aliasing with the internal electronics

can occur. To ensure that aliased signals do not couple into the baseband measurement

range, design the module wherein the first system level resonance occurs at a frequency

higher than 800 Hz.

Fig 9.3 Incorrectly Mounted Gyroscope

9.1.3 LCC-V Package details

Fig 9.4 Pin out And Application Diagram



These application circuits provide a connection reference for the available

package types. Note that DVDD, AVDD, and PDD are individually connected to ground

through 1 μF capacitors; do not connect these supplies together. Additionally, an external

diode and inductor must be connected for proper operation of the internal shunt regulator.

These components allow for the internal resonator drive voltage to reach its required

level.

9.1.4 Pin Description

Pin No. Mnemonic Description

1 AVSS Analog Ground.

2 AVDD Analog Regulated Voltage.

3 MISO Master In/Slave Out.

4 DVDD Digital Regulated Voltage.

5 SCLK SPI Clock. 6 CP5 High Voltage Supply.



9 VX High Voltage Switching Node.

10 CS Chip Select.

11 DVSS Digital Signal Ground.

12 MOSI Master Out/Slave In.

13 PSS Switching Regulator Ground.

14 PDD Supply Voltage.

Table 9.2 Pin description of LCC-V package

The ADXRS450 operates on the principle of a resonator gyro-scope. Each sensing

structure contains a dither frame that is electrostatically driven to resonance. This

produces the necessary velocity element to produce a Coriolis force when experiencing

angular rate. In the SOIC_CAV package, the ADXRS450 is designed to sense a z-axis



(yaw) angular rate; whereas the vertical mount package (LCC_V) orients the device such

that it can sense pitch or roll angular rate on the same PCB.

When the sensing structure is exposed to angular rate, the resulting Coriolis force

couples into an outer sense frame, which contains movable fingers that are placed

between fixed pickoff fingers. This forms a capacitive pickoff structure that senses

Coriolis motion. The resulting signal is fed to a series of gain and demodulation stages

that produce the electrical rate signal output. The quad sensor design rejects linear and

angular acceleration, including external g-forces and vibration

Fig 9.5 Gyroscope structure

Fig 9.6 ADXRS450 chip structure Structure



9.1.5 Evaluation Board for ADXRS450

The ADXRS450/ADXRS453 inertial sensor evaluation system is an easy-to-use

evaluation tool targeting bench or desktop characterization of Analog Devices, Inc.,

inertial sensor products. The system consists of the inertial sensor evaluation board

(ISEB), or main board and satellite boards for several Analog Devices inertial sensor

products. The ISEB connects directly to a PC via a USB cable, with the USB connection

providing both power and communications to the board. The ISEB is connected to the

satellite board through a ribbon cable. This cable allows the satellite to be easily

manipulated for testing or separately placed into an environmental chamber for

temperature or humidity testing. Separating the boards mitigates corruption of data due to

the temperature and humidity effects of other components. The different products are

evaluated by means of separate GUIs that are customized for performance and

characterization measurements relevant to the inertial sensor being evaluated.

Fig 9.7 Evaluation board



9.2 PIC 18F6520 The PIC18FXX20 family offers the same advantages of all PIC18

microcontrollers – namely, high computational performance at an economical price –

with the addition of high endurance Enhanced Flash program memory. The PIC18FXX20

family also provides an enhanced range of program memory options and versatile analog

features that make it ideal for complex, high-performance applications.

9.2.1 Features of PIC 18F6520 a) Expanded Memory

The PIC18FXX20 family introduces the widest range of on-chip, Enhanced Flash

program memory available on PIC micro microcontrollers – up to 128 Kbyte (or 65,536

words), the largest ever offered by Microchip. For users with more modest code

requirements, the family also includes members with 32 Kbyte or 64 Kbyte.

Other memory features are:

• Data RAM and Data EEPROM: The PIC18FXX20 family also provides plenty of room

for application data. Depending on the device, either 2048 or 3840 bytes of data RAM are

available. All devices have 1024 bytes of data EEPROM for long-term retention of

nonvolatile data.

• Memory Endurance: The Enhanced Flash cells for both program memory and data

EEPROM are rated to last for many thousands of erase/write cycles – up to 100,000 for

program memory and 1,000,000 for EEPROM. Data retention without refresh is

conservatively estimated to be greater than 40 years.

b) External Memory Interface

In the event that 128 Kbytes of program memory is inadequate for an application,

the PIC18F8X20 members of the family also implement an External Memory Interface.

This allows the controller’s internal program counter to address a memory space of up to

2 Mbytes, permitting a level of data access that few 8-bit devices can claim.



With the addition of new operating modes, the External Memory Interface offers

many new options, including:

• Operating the microcontroller entirely from external memory.

• Using combinations of on-chip and external memory, up to the 2-Mbyte limit.

• Using external Flash memory for reprogrammable application code, or large data tables.

• Using external RAM devices for storing large amounts of variable data.

c) Easy Migration

Regardless of the memory size, all devices share the same rich set of peripherals,

allowing for a smooth migration path as applications grow and evolve. The consistent pin

out scheme used throughout the entire family also aids in migrating to the next larger

device. This is true when moving between the 64-pin members, between the 80-pin

members, or even jumping from 64-pin to 80-pin devices.

d) Special Features

• Communications: The PIC18FXX20 family incorporates a range of serial

communications peripherals, including 2 independent USARTs and a Master SSP

module, capable of both SPI and I2C (Master and Slave) modes of operation. For

PIC18F8X20 devices, one of the general purpose I/O ports can be reconfigured as an 8-

bit Parallel Slave Port for direct processor-to-processor communications.

• CCP Modules: All devices in the family incorporate five Capture/Compare/PWM

modules to maximize flexibility in control applications. Up to four different time bases

may be used to perform several different operations at once.

• Analog Features: All devices in the family feature 10-bit A/D converters, with up to 16

input channels, as well as the ability to perform conversions during Sleep mode. Also

included are dual analog comparators with programmable input and output configuration,



a programmable Low-Voltage Detect module and a programmable Brown-out Reset

module.

• Self-programmability: These devices can write to their own program memory spaces

under internal software control. By using a boot loader routine located in the protected

Boot Block at the top of program memory, it becomes possible to create an application

that can update itself in the field.

There are 5 PICS in this family. They are differentiated by

• Flash program memory (32 Kbytes for PIC18FX520 devices, 64 Kbytes for

PIC18FX620 devices and 128 Kbytes for PIC18FX720 devices).

• Data RAM (2048 bytes for PIC18FX520 devices, 3840 bytes for PIC18FX620 and PIC18FX720 devices).

• A/D channels (12 for PIC18F6X20 devices, 16 for PIC18F8X20).

• I/O pins (52 on PIC18F6X20 devices, 68 on PIC18F8X20).

• External program memory interface (present only on PIC18F8X20 devices).

Analog Features of PIC are:

• Up to 16-ch 10-bit Analog-to-Digital Converter (A/D)

• Conversion available during SLEEP

• Programmable 16-level Low Voltage Detection (LVD) module

• Supports interrupt-on-Low Voltage Detection

• Programmable Brown-out Reset (BOR)

• Dual analog comparators

• Programmable input/output configuration



9.2.2 Pin Out

Fig 9.8 Pin Out of 64 Pin PIC18F6520



9.3 MAX232 The MAX232 is an IC, first created in 1987 by Maxim Integrated Products, that

converts signals from an RS-232 serial port to signals suitable for use in TTL compatible

digital logic circuits. The MAX232 is a dual driver/receiver and typically converts the

RX, TX, CTS and RTS signals.

The drivers provide RS-232 voltage level outputs (approx. ± 7.5 V) from a single +

5 V supply via on-chip charge pumps and external capacitors. This makes it useful for

implementing RS-232 in devices that otherwise do not need any voltages outside the 0 V

to + 5 V range, as power supply design does not need to be made more complicated just

for driving the RS-232 in this case.

The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to standard

5 VTTL levels. These receivers have a typical threshold of 1.3 V, and a typical hysteresis

of 0.5 V. The later MAX232A is backwards compatible with the original MAX232 but

may operate at higher baud rates and can use smaller external capacitors — 0.1 μF in

place of the 1.0 μF capacitors used with the original device. The newer MAX3232 is also

backwards compatible, but operates at a broader voltage range, from 3 to 5.5 V.

Fig 9.9: MAX232 Chip

http://en.wikipedia.org/wiki/Maxim_Integrated_Products

http://en.wikipedia.org/wiki/RS-232

http://en.wikipedia.org/wiki/Transistor-transistor_logic

http://en.wikipedia.org/wiki/Volt

http://en.wikipedia.org/wiki/Charge_pump

http://en.wikipedia.org/wiki/Power_supply

http://en.wikipedia.org/wiki/Transistor-transistor_logic

http://en.wikipedia.org/wiki/Hysteresis

http://en.wikipedia.org/wiki/Baud

http://en.wikipedia.org/wiki/Farad



It is helpful to understand what occurs to the voltage levels. When a MAX232 IC

receives a TTL level to convert, it changes TTL logic 0 to between +3 and +15 V, and

changes TTL logic 1 to between -3 to -15 V, and vice versa for converting from RS232 to

TTL. This can be confusing when you realize that the RS232 data transmission voltages

at a certain logic state are opposite from the RS232 control line voltages at the same logic

state.

Fig 9.10: TTL converter Fig 9.11: MAX232 Die

The MAX232 (A) has two receivers (converts from RS-232 to TTL voltage

levels), and two drivers (converts from TTL logic to RS-232 voltage levels). This means

only two of the RS-232 signals can be converted in each direction. Typically, a pair of a

driver/receiver of the MAX232 is used for TX and RX signals, and the second one for

CTS and RTS signals.

There are not enough drivers/receivers in the MAX232 to also connect the DTR,

DSR, and DCD signals. Usually these signals can be omitted when communicating with a

PC's serial interface. If the DTE really requires these signals, either a second MAX232 is

needed, or some other IC from the MAX232 family can be used. Also, it is possible to

directly wire DTR (DB9 pin #4) to DSR (DB9 pin #6) without going through any

circuitry. This gives automatic (brain dead) DSR acknowledgment of an incoming DTR

signal.



9.4 RS 232

RS-232 was first introduced in 1962 by the Radio Sector of the EIA. The original

DTEs were electromechanical teletypewriters, and the original DCEs were (usually)

modems. When electronic terminals (smart and dumb) began to be used, they were often

designed to be interchangeable with teletypewriters, and so supported RS-232. The C

revision of the standard was issued in 1969 in part to accommodate the electrical

characteristics of these devices.

Since the requirements of devices such as computers, printers, test instruments,

POS terminals and so on were not considered by the standard; designers implementing an

RS-232 compatible interface on their equipment often interpreted the requirements

idiosyncratically. Common problems were non-standard pin assignment of circuits on

connectors, and incorrect or missing control signals. The lack of adherence to the

standards produced a thriving industry of breakout boxes, patch boxes, test equipment,

books, and other aids for the connection of disparate equipment. A common deviation

from the standard was to drive the signals at a reduced voltage. Some manufacturers

therefore built transmitters that supplied +5 V and -5 V and labeled them as "RS-232

compatible".

Later personal computers (and other devices) started to make use of the standard

so that they could connect to existing equipment. For many years, an RS-232-compatible

port was a standard feature for serial communications, such as modem connections, on

many computers. It remained in widespread use into the late 1990s. In personal computer

peripherals, it has largely been supplanted by other interface standards, such as USB. RS-

232 is still used to connect older designs of peripherals, industrial equipment (such as

PLCs),console ports and special purpose equipment.

The standard has been renamed several times during its history as the sponsoring

organization changed its name, and has been variously known as EIA RS-232, EIA 232,

and most recently as TIA 232. The standard continued to be revised and updated by the

Electronic Industries Alliance and since 1988 by the Telecommunications Industry

Association (TIA). Revision C was issued in a document dated August 1969. Revision D

http://en.wikipedia.org/wiki/Electronic_Industries_Alliance

http://en.wikipedia.org/wiki/Teleprinter

http://en.wikipedia.org/wiki/Computer_terminal

http://en.wikipedia.org/wiki/POS_terminal

http://en.wikipedia.org/wiki/Serial_communication

http://en.wikipedia.org/wiki/Programmable_logic_controller

http://en.wikipedia.org/wiki/System_console

http://en.wikipedia.org/wiki/Electronic_Industries_Alliance

http://en.wikipedia.org/wiki/Telecommunications_Industry_Association

http://en.wikipedia.org/wiki/Telecommunications_Industry_Association



was issued in 1986. The current revision is TIA-232-F Interface between Data Terminal

Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data

Interchange, issued in 1997. Changes since Revision C have been in timing and details

intended to improve harmonization with the CCITT standard V.24, but equipment built to

the current standard will interoperate with older versions.

In telecommunications, RS-232 is the traditional name for a series of standards

for serial binary single-ended data and control signals connecting between DTE (data

terminal equipment) and DCE (data circuit-terminating equipment, originally defined as

data communication equipment. It is commonly used in computer serial ports. The

standard defines the electrical characteristics and timing of signals, the meaning of

signals, and the physical size and pin out of connectors. The current version of the

standard is TIA-232-F Interface between Data Terminal Equipment and Data Circuit-

Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997.

An RS-232 serial port was once a standard feature of a personal computer, used

for connections to modems, printers, mice, data storage, uninterruptible power supplies,

and other peripheral devices. However, the low transmission speed, large voltage swing,

and large standard connectors motivated development of the Universal Serial Bus, which

has displaced RS-232 from most of its peripheral interface roles. Many modern personal

computers have no RS-232 ports and must use either an external USB-to-RS-232

converter or an internal expansion card with one or more serial ports to connect to RS-

232 peripherals. RS-232 devices are still found, especially in industrial machines,

networking equipment, and scientific instruments.

Fig 9.12 A DB-25 Connector

http://en.wikipedia.org/wiki/ITU-T

http://en.wikipedia.org/wiki/Telecommunications

http://en.wikipedia.org/wiki/Serial_communication

http://en.wikipedia.org/wiki/Single-ended_signaling

http://en.wikipedia.org/wiki/Data_transmission

http://en.wikipedia.org/wiki/Signaling_(telecommunications)

http://en.wikipedia.org/wiki/Data_terminal_equipment

http://en.wikipedia.org/wiki/Data_terminal_equipment

http://en.wikipedia.org/wiki/Data_circuit-terminating_equipment

http://en.wikipedia.org/wiki/Computer

http://en.wikipedia.org/wiki/Serial_port

http://en.wikipedia.org/wiki/Pinout

http://en.wikipedia.org/wiki/Serial_port

http://en.wikipedia.org/wiki/Personal_computer

http://en.wikipedia.org/wiki/Modem

http://en.wikipedia.org/wiki/Printer_(computing)

http://en.wikipedia.org/wiki/Mouse_(computing)

http://en.wikipedia.org/wiki/Uninterruptible_power_supplies

http://en.wikipedia.org/wiki/Universal_Serial_Bus

http://en.wikipedia.org/wiki/File:DB25_Diagram.svg



9.4.1 DB-9 USB Modules

The DB9-USB connector modules can be used to upgrade an RS232 port to an

active USB port without the need to redesign the PCB. The DB9-USB family consists of

6 modules. Two of these operate at RS232 voltage levels, while four of them operate at

digital voltage levels (a choice of 5V or 3.3V). Each is available to replace either a male

or a female DB9.

The FTDI DB9-USB-RS232 modules are available in two types DB9-USB-

RS232-M and DB9-USB-RS232-F.

• A DB9-USB-RS232-M can be used to replace a male DB9 connector that is wired

in a PC compatible RS232 manner. This module operates at RS232 signal levels.

• A DB9-USB-RS232-F can be used to replace a female DB9 connector that is

wired in a PC compatible RS232 manner. This module operates at RS232 signal

levels.

The purposes of these modules is to provide a simple method of adapting legacy

serial devices with UART interfaces to modern USB ports by replacing the DB9

connector with this miniaturized module which closely resembles a DB9 connector. This

is accomplished by incorporating the industry standard FTDI FT232R USB-Serial Bridge

IC. The RS232 level DB9-USB modules include an RS232 level transceiver.

Fig 9.13 DB-9 USB Family



CHAPTER 10

SOFTWARE DESCRIPTION

LabVIEW is a graphical programming language that uses icons instead of lines of

text to create applications. In contrast to text-based programming languages, where

instructions determine program execution, LabVIEW uses dataflow programming, where

the flow of data determines execution. In LabVIEW, user interface is built with a set of

tools and objects. The user interface is known as the front panel. Then add code using

graphical representations of functions to control the front panel objects. The block

diagram contains this code. In some ways, the block diagram resembles a flowchart.

LabVIEW programs are called virtual instruments, or VIs, because their

appearance and operation imitate physical instruments, such as oscilloscopes and

multimeters. Every VI uses functions that manipulate input from the user interface or

other sources and display that information or move it to other files or other computers.

A VI contains the following three components:

•Front panel— Serves as the user interface.

•Block diagram— contains the graphical source code that defines the functionality of

the VI.

•Icon and connector pane— identifies the VI so that you can use the VI in another VI.

A VI within another VI is called a sub VI. A sub VI corresponds to a subroutine in text-

based programming languages.

Then build the front panel with controls and indicators, which are the interactive

input and output terminals of the VI, respectively. Controls are knobs, push buttons, dials,

and other input devices. Indicators are graphs, LEDs, and other displays. Controls

simulate instrument input devices and supply data to the block diagram of the VI.



Indicators simulate instrument output devices and display data the block diagram

acquires or generates.

Fig 10.1 Front Panel of LabVIEW

After building the front panel, add code using graphical representations of

functions to control the front panel objects. The block diagram contains this graphical

source code. Front panel objects appear as terminals on the block diagram.

The terminals represent the data type of the control or indicator. It can configure

front panel controls or indicators to appear as icon or data type terminals on the block

diagram. By default, front panel objects appear as icon terminals.



Nodes are objects on the block diagram that have inputs and/or outputs and

perform operations when a VI runs. They are analogous to statements, operators,

functions, and subroutines in text-based programming languages.

It can transfer data among block diagram objects through wires. Wires connect

the control and indicator terminals to the Add and Subtract functions. Each wire has a

single data source, but you can wire it to many VIs and functions that read the data.

Wires are different colors, styles, and thicknesses, depending on their data types. A

broken wire appears as a dashed black line with a red X in the middle.

Structures are graphical representations of the loops and case statements of text-

based programming languages. Use structures on the block diagram to repeat blocks of

code and to execute code conditionally or in a specific order.

Fig 10.2 Block Diagram and Corresponding Front Panel



FUTURE WORK

This design phase report deals with the initial study on application of a

MEMS based gyroscope ADXRS450 to measure the spin rate of a spinning rocket. In this

phase we have studied about the history of gyroscopes and its different variants. It is also

studied on how the spinning of a sounding rocket helps in attaining stability during its

flight. Afterwards, we have discussed on how to implement this project for measuring the

spin rate.

In the next phase we are going to design the circuit and analyze it. After

this we will be implementing this project at VSSC, Thumba. We will be doing the

necessary software implementation and code burning for microcontroller along with the

hardware implementation. After successful implementation of the circuit we will examine

it to get an idea of its performance and to ensure its accuracy. We will be utilizing the

help of Labview software for graphically evaluating the result.



REFERENCES

1. SPRY, S.C., GIRARD, A.R.:” Gyroscopic Stabilization of Unstable Vehicles:

configurations, dynamics and control, in Vehicle System Dynamics”, 2008,

Vol.46, pp.247-260.

2. JOE SEEGER, MARTIN LIM, and STEVE NASIRI: “Development of High

Performance High-Volume Consumer MEMS Gyroscopes”.

3. DAMRONGRIT PIYABONGKARN & RAJESH RAJAMANI:”The

Development of a MEMS Gyroscope for Absolute Angle Measurement”.

4. N. YAZDI, F. AYAZI, AND K. NAJAFI. Aug. 1998. “Micromachined Inertial

Sensors,” Proc IEEE, Vol. 86, No. 8.

5. JONATHAN BERNSTEIN, CORNING-INTELLISENSE CORP ,” MEMS

inertial sensing technology”.

Mems Based Digital Gyroscope

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