summary of lectures 1-3 sit 4011

Avionics Systems 4S(SIT4011)

A BIG WELCOME

23rd Sep 2013

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BEAUTIFUL GLASGOW

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1) Spaceflight dynamics, by Wiesel. 2nd edition available at SP Popular bookshop. 3rd

edition available on internet.

2) Avionics Navigation Systems, Kayton M., Fried, W. R., Wiley.

3) Introduction to Radar Systems – Third edition, Skolnik, M. I., McGraw-Hill International.

Recommended Texts3

Coverage

� To understand the science, purpose and principles of aerospace GNC, CNS/ATM and Radar information systems. To provide the broad range knowledge of technology required by the aerospace systems’ engineer. Course syllabus: The advanced signal processes and key equations. Review of Radar theory, radar signals and signal processing, Doppler radar, airborne radar systems. Pulse, compression and matched filters. Radar signal filtering, plot extraction and target modelling. Selected topics from: SSR, Mode-S. GNSS, ACAS/TCAS II and TCAS IV, GPWS, VOR, DME, ILS, MLS.

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Chapter 1

�What is Navigation?

1. The theory and practice of navigating, especially the charting of a course for a ship or aircraft.

2. Travel or traffic by vessels, especially commercial shipping.

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Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another. The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation All navigational techniques involve locating the navigator's position compared to known locations or patterns.

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Some basic definitions, notations, nomenclatures

7Why systems requires constant UPDATES to maintain accuracy. Updates obtained

Conventional ground-based radio navigations aids, or GNSS

Visual Omni

Range is and

instrument

that receives

high frequency

radio signals

from a

transmitting

station.

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Some definitions

1. Dynamics: It is the study of effect of force system acting on a particle or a rigid body which is in motion. Dynamics is the study of geometry of motion with or without reference to the cause of motion.

2. Particle - a single point, considerable mass but negligible dimension.

3. Rigid Body – no deformation under action of forces and with dimension.

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�Newton's Three Laws of Motion

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THE SOLAR SYSTEM

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Introduction

� A solar system consists of a star and objects that revolve around it.

� Our Solar System consists of the Sun and nine known planets and the moons that orbit those planets.

� The force of gravity keeps planets in orbit around the sun.

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The Nine Known Planets

The Inner Planets The Outer Planets

� Mercury

� Venus

� Earth

� Mars

� Jupiter

� Saturn

� Uranus

� Neptune

� Pluto

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The Orbital Speed of the Planets

� Mercury = 30 miles per second� Venus = 22 miles per second� Earth = 19 miles per second� Mars = 15 miles per second� Jupiter = 8 miles per second� Saturn = 6 miles per second� Uranus = 4.2 miles per second� Neptune = 3.3 miles per second� Pluto = 2.9 miles per second

Therefore, the further away from the Sun, the slower the orbital speed.

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12_001a

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12_001b

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12_001c

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12_001e

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12_FP002

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12_P002

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12_P013

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12_P053

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12_016a

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12_016b

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12_016c

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12_016g

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12_017a

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12_044a_EX026

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12_CR003

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12_CR009

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Exercise32

Avionics Systems 4S(SIT4011)

� Lecture 2: Forces and Acceleration

23rd Sep 2013

33

BEAUTIFUL GLASGOW

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Engineering Mechanics, Dynamics, SI UNIT, 13th

Edition, R.C.Hibbeler, Pearson

A Basic Understanding of the Inertial System is important before proceeding to Non-Inertial System.

Recommended Text

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13_003

You Try !!!

13_011

13_FP007

13_P053-054

13_P080-081

Avionics Systems 4S(SIT4011)

� Lecture 3: Pendulum and Accelerometer

23rd Sep 2013

44

BEAUTIFUL GLASGOW

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13_P083

� A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force combined with the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. A pendulum swings with a specific period which depends (mainly) on its length.

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

� The period of swing of a simple gravity pendulum depends on its length, the local strength of gravity, and to a small extent on the maximum angle that the pendulum swings away from vertical, θ0, called the amplitude.It is independent of the mass of the bob. If the amplitude is limited to small swings, the period Tof a simple pendulum, the time taken for a complete cycle, is:

where L is the length of the pendulum and g is the local acceleration of gravity.

You may like to refer to page 4 of “ SpaceFlight Dyanmics”

Fully Integrated Northrop Grumman AMMC

Courtesy Northrop Grumman

Northrop Grumman

Navigational Systems

� Radar

� Weather/terrain monitoring

� Air traffic tracking

� GPS

� Inertial reference systems

� i.e. Honeywell Primus Epic INAV and Northrop Grumman LTN-101E GNADIRU

Inertial measurements

� Accelerometers measure absolute acceleration

� Rate gyroscopes measure angular velocity

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

Applications:

- crash detector in airbag

• 50g with 100’s bandwidth.• reliability is of vital importance.

=> self-test mechanism is mandatory.

active suspensions

anti-lock braking systems

traction control systems

inertial navigation systems.

• integrate twice to obtain the position.

• resolution ~ mg to ensure the accuracy over a long period of time.

• thermal behavior is extremely important.

Introduction to Accelerometer

Accelerometers

� Devices that measure linear or translational acceleration along the sensitive axis

� Use the property of inertia to measure absoluteacceleration

� Mechanical or solid-state devices

� Mechanical device model also applicable to solid-state devices

Accelerometers

Accelerometers

Accelerometers

kspring,cdamper,

Accelerometer - Measurement Devices

� A basic transducer used in vibration measurement is the accelerometer.

� This device can be modeled using the base equations developed in the previous section

F∑ = - k(x-y) - c(�x-�y) = m��x

⇒ m��x = -c( �x − �y) - k(x − y)

( 2.86) and (2.61)

Here, y(t) is the measured

response of the structure

Figure 2.24

Base motion applied to measurement devices

Piezoelectric Accelerometer

Strain Gauge

Let z(t) = x(t ) − y(t) (2.87) :

⇒

m��z + c�z(t) + kz(t ) = mωb

2Y cosωbt (2.88)

⇒Z

Y=

r2

(1− r2)

2 + (2ζr)2

(2.90)

and

θ = tan−1 2ζr

1− r2

(2.91)

These equations should be familiar

from base motion.

Here they describe measurement!

Magnitude and sensitivity plots for accelerometers.

Fig 2.27

Fig 2.28

Magnitude plot showing

Regions of measurement

Effect of damping on

proportionality constant

In the accel region, output voltage is

nearly proportional to displacement

Accelerometers

� The accelerometer will measure the absoluteacceleration by means of a relative displacement

� Construct a free-body diagram of the case mass, apply Newton’s 2nd law

� Repeat for the proof mass

� Two governing equations in 2 unknowns solved simulataneously…

Accelerometers…UoG

� FBD, case mass

Accelerometers

� FBD, case mass

Accelerometers

� Governing equation, case mass

• Note that spring and damper forces are

proportional to relative position of proof and

case masses

• One equation, two unknowns

Accelerometers

� FBD, proof mass

Accelerometers

� FBD, proof mass

Accelerometers

� Governing equation, proof mass

• Now have two equations in two unknowns

• Hence

Accelerometers

� Or…

• Classical spring-mass-damper system

• Absolute acceleration measure by relative

position

Accelerometers

� then…

• If…

Accelerometers

• Steady-state solution is

• Sensitivity of the accelerometer is therefore a function of proof mass and spring stiffness

• Stiffness is usually chosen for a much faster response than data to be measured

• Damper is then selected to give optimum transient response

Accelerometers

• Errors include

– Scale factor

– Bias

– Time lag

Scale Factor

The ratio of the change in output (in volts or amperes) to a unit change of the input (in units of acceleration); thus given in mA/g or V/g.