1

Navigation sensors and systems

Glossary Classified navigation sensors Classical navigation sensors

accelerometers gyroscopes, rate gyros inertial measurement units

Inertial navigation systems (INS) global design gimbaled / strap down systems attitude measurement

Structure of INS errors Hybridization : the example of INS/GPS

survey of hybridization techniques review of common architectures

2

Foreword

Control Guidance Navigation Reference

Stabilisation Attitude control

Position and velocityrelative to a target

Position and velocityrelative to Earth

Position, velocity, attitude

Satellites

Launchers and balistic missiles

Civil air transportation

Military aircraft

Tactical missiles

Ground vehicles, radars, surveillance

Head Up Displays

Naval surface ships

Torpedoes

Submarines

Navigation systems are key elements of

guidance and control of autonomous or non-autonomou s vehicles.

3

Pourquoi ces fonctions et technologies ?

Localisation, références de vitesse et d’attitude sont critiquessur la plupart des plateformes, pour : les performances, le coût,

l’effort de développement et d’intégration

haute sensibilité de la fonction navigation dans les programmes d’armements

4

L’inertie et l’équilibre mondial bipolaire

Les pionniers (1958) : sous-marin américain type Nautilus

La riposte soviétique (1962) : sous-marin soviétique type K-3

5Aéronautique

Etendue des applications

1 mg

Gyrometers accuracy

AccelerometerAccuracy

150°/h 1°/h 0.1°/h 0.01°/h 0.001°/h

10 mg

100 µg

10 µg

Launchers

Military Aero

Military Land Navigation

30°/h

Civil Aero

Ammunitions

Short range& medium range

Gyro stabilization

Air Defense

AHRSMilitary Aerial

Transportation

Cruise Missiles

G-IRS

Stand-By&

Flight Controls

Rocket

Industry

0.05°/hSubmarines

Navigation

ICBM

HRG - RLG - FOG RLG - FOG HPMEMS

ME

MS

PO

L -

PC

L

Floated - DTG

Military Helos

GVP HP

6

Military applications : IRS/INS/G -IRS

Mirage’s INSMirage’s INS

Cruise missiles

THALES TOTEM 3000

SAGEM SIGMA95

THALES MAIA100

7

Other military applications : AHRS

Commercial brochure, downloaded from the internet, at www.kvh.com

Global Hawk RQ-4, Northtrop Grumann

Miniature AHRS on RQ-4 by Crossbow

8

Civil applications : IRS/INS/G -IRS

THALES’ ADIRU on AIRBUS

Quasar 3000, Ariane V’s INS

THALES’ stand-by instrument

9

Vocabulary

LocalizationProvide other functional equipments with position, speed, attitude, heading and rotation rate of a sol id reference element of the system.

GuidanceDefine a trajectory or piece of trajectory in the s tate space.

ControlDefine command values to apply in order to pilot th e vehicle along the guidance trajectory.

NavigationCombined loops of guidance, control and localizatio n.

10

Missile and Space applications

GuidanceDefine a trajectory for the center of gravity to fo llow.

ControlCorrect trajectory errors via attitude control.

NavigationSensors and systems providing the position of the c enter of gravity.

For any vehicle controlled with attitude only

11

Guidance, navigation and control : a global loop

Guidance

Predetermine portions of state space trajectories, such as position attitude

Control

Which control inputs to apply to the vehicle ?

What trajectory should I follow ?

Operate the vehicle some time

True vehicle’s dynamics

Localization

True vehicle’s trajectory

Estimate corrections

12

Chaines fonctionnelles(exemple SCORPION)

Observateur

Missile moyenne portée

Tireur

Frappe de la cible

Navigation missile

Désignation d’objectif

Localisation tireur

Alignement

13

Glossary

AttitudeAngular position of a solid with respect to an atti tude reference. Various kind of parameter sets : Eu ler angles, quaternions, direction cosine matrix.Often restrictly refers to roll and pitch angles (a s in AHRS below).

Attitude referenceNecessary to define an attitude. For instance : Loc al Geodetic Coordinate Frame (NED or NWU), Earth-Fixed Earth Centered Coordinate Frame, Copernic Ref erence Frame

Platform referenceReference to some force or some vector positioning in space (for instance : specific force or rotation al rate)

Navigation parameters at time tAny subset of the following : position, velocity, a ttitude, angular rateAnd never forget the accuracy !

14

Glossary

Reference frameCommunication tool between systems or humans, allow ing exchange of positioning data and objects/target designation.

The most common reference frame is a global coordin ate system (eg WGS84)

Ellipsoïd reference Semi-major axis a Semi-minor axis b Inverse flattening

WGS 84 6,378,137.0 m ≈ 6,356,752.314 245 m 298.257 223 563

15

Glossary

Navigation sensorAny device extracting a measurable signal from a ph ysical effect of motion. This signal is provided as an output of the device : voltage, current, frequen cy, bits…

Navigation equipmentAny equipment providing users or other systems with computed or estimated navigation parameters. Eg : rate gyro, two axis accelerometer, GALILEO rece iver, intelligent camera, …

Navigation systemAny system providing a full set of navigation param eters (and accuracy self-estime), based on embedded or auxiliary navigation equipments.

Attitude and heading reference system (AHRS)Any system providing attitude and heading parameter s (and accuracy estimation), based on embedded or auxiliary navigation equipments.

Inertial systemAny system whose function is based on inertial expe riments.

16

Navigation sensors

17

Orientation rate gyros

Orientation gyros stellar sensors intelligent cameras compasses, magnetometers

Specific force accelerometers

Speed Global Navigation Satellite Systems : GPS, Глонасс, Galileo Pitot tubes logs, Doppler logs optical flow sensors

Navigation sensors by categories

Position Global Navigation Satellite Systems : GPS, Глонасс, Galileo Intelligent cameras imagery Terrain correlation telemetry sensors : LADAR, LIDAR, …

HYDRA2 stellar sensor

THALES TOPSTAR 2020 GPS receiver

ATV’s videometer by EADS Sodern

THALES’ High precisionaccelerometer

GRH Cristal

SAGEM SIGMA95 InertialNavigation System

DAGR GPS Receiver by Rockwell Collins

(handheld)

Airspeed probe (THALES)

18

IEEE standard for strapdown INS architectureF

rom

CS

DL

-P-4

127

, PR

OP

OS

ED

IEE

E IN

ER

TIA

L S

YS

TE

MS

TE

RM

INO

LO

GY

ST

AN

DA

RD

AN

D O

TH

ER

INE

RT

IAL

SE

NS

OR

ST

AN

DA

RD

Sb

y R

. K. C

ure

y, M

. E

. Ash

, L

. O. T

hie

lman

, C. H

. B

arke

r , F

eb

ruar

y 2

00

4P

rese

nte

d a

t: IE

EE

Po

sitio

n L

oca

tion

Nav

igat

ion

Sym

po

sium

20

04

Mo

nte

rey,

CA

26

-29

Ap

ril 2

00

4

ISA : inertial sensor assemblyP/S : Power supplyIMU : inertial measurement unitINS : inertial navigation system

19

IEEE standard for gimbaled INS architectureF

rom

CS

DL

-P-4

127

, PR

OP

OS

ED

IEE

E IN

ER

TIA

L S

YS

TE

MS

TE

RM

INO

LO

GY

ST

AN

DA

RD

AN

D O

TH

ER

INE

RT

IAL

SE

NS

OR

ST

AN

DA

RD

Sb

y R

. K. C

ure

y, M

. E

. Ash

, L

. O. T

hie

lman

, C. H

. B

arke

r , F

eb

ruar

y 2

00

4P

rese

nte

d a

t: IE

EE

Po

sitio

n L

oca

tion

Nav

igat

ion

Sym

po

sium

20

04

Mo

nte

rey,

CA

26

-29

Ap

ril 2

00

4

ISA : inertial sensor assemblyP/S : Power supplyIMU : inertial measurement unitINS : inertial navigation system

ARO : (gimbal) angle readoutsTQR : (gimbal) torquers

20

Key elements of inertial systems

Supporting mechanics

Inertial sensorsGyroscopes and rate gyros

AccelerometersPerformance under

environment, reliability

Stiffness, EM shielding, precision,

optical alignment

SuspensionsShock damage avoidance

Vibration isolation

Control electronicsDedicated compensations

Mechanical housingStiffness, EM shielding, precision, optical alignment, thermal draining, handling

Navigation computerOptimized and modular algorithms,

safety design objectives

Input/Output boardVersatility, performance, safety design objectives

Power supplyStability, power consumption

21

Accelerometers

MICAL

Quartz VBA A90

Si MEMS A100

22

Pendulous Integrating Gyroscope Accelerometer (PIGA)

Accelerometers

1960 1970 1980 1990 2000 2010 2020

Si-MEMS

Vibrating Beam Accelerometer (VBA)

Mechanical Pendulous Rebalance Accelerometer

Pendulous accelerometer fluidic damping

23

Accels performance requirements vs applications

24

Accelerometers : international definition (IEEE Std5 28)

Accelerometer : An inertial sensor that measures linear or angular acceleration along

its input axis(es) . Except where specifically stated, the term accelerometer refers to linear accelerometer.

Note 1: An output signal is produced from the motion of a proof mass relative to the case, or from the force or torque required to restore the proof mass to a null position relative to the case.

Note 2: When transforming to an inertial frame for navigation computations, a linear accelerometer’s output must be compensated for the effects of centripetal and angular acceleration and gravity.

Accelero output S : analog or digital (volts, amperes, frequency or bits)

Acceleration to be measured on the input axis W : usually expressed in m/s²

γapparent acceleration

sensorS

outputinput axis

25

Accelerometers - Parts

Proof Mass

Packaging

Hinge

Pendulum axis

Input axisHinge axis

External acceleration

Input force

26

Aboard the vehicle, the pilot is subject to all the forces exerted by the seat.

These forces are such that the pilot remains fixed in the cockpit.

F = m ( γ − g)

What an accelerometer does measure

Thrust

= true vehicle’s acceleration m γγγγ

R2 = mγγγγThrust transmission

Reactive force to gravity mg

R1 = −−−− mg

Resulting force exerted by the seat to the pilot

mγ γ γ γ −−−− mg

27

1955 1975 1995

Pendulous Integrating Gyro Accelerometer (PIGA)

Fluidic dampingpendulous accelerometer

Accelerometer MEMS (Micro Electro

Mechanicals Systems)

Squeeze film dampingpendulous accelerometer

Vibrating Beam Accelerometer

Dimensions, number of parts and cost are decreasing

Trade-off between :accuracy, size and cost

1965 1985

Num

ber

of p

arts

1 _

10 _

100 _

Accelerometers

28

Accelerometers - Productions

Accelerometers are produced by companies in :

China Finland France Germany Israel India Italy Japan North Korea

"Equipment, Software and Technology Annex Handbook" (MTCR - May, 2005)

Norway Pakistan Russian Federation South Africa Sweden United Kingdom United States

29

Accelerometers - technologies

Proof mass : flexures - hinges - pivots Damping : fluidic - gas - mechanical Pickoff : electromagnetic, capacitive, optical, piezoresitive, strain

on a beam Forcer : electromagnetic, electrostatic,… Temperature measurement : internal or external Case : hermetic, thermal and mechanical insulator Servo loop : analogue or digital loop

30

Open loop pendulous accelerometer - 1 axis Motion detection : small angle α between acceleration and

pendulous axis Pendulum length L Hinge torsional stiffness Cc

Stiff hinge (suspension)

case

Detector

Proof mass M

M . L . Acceleration = Cc . αααα

Input axis

Pendulum axis

Hinge axis

Amesure

α

Accelerometers - Open loop

31

Closed loop : Pickoff detector measures the motion of the pendulum Force generator designed to oppose the inertia force Electronic servomechanism to keep the pickoff signal at 0

Electronic servomechanism

Amplifier

output(acceleration measurement)

forcer

pickoff detector

Pre-amplifier

Servo loop

Accelerometers - Closed loop

32

Force feedback accelerometer

Pendulous accelerometer (1970)

Electromagnetic forcer Fluidic damping inductive detection Needs thermal regulation

Electronics :

Servomechanism loop Analog to digital converter

33

Mechanical force feedback - force rebalanced - closed loop -servoed accelerometer with capacitive detection

Capacitive pick-off

Permanent magnets

- The motion of the proof mass induced by the applied acceleration is counteracted by a restoring force- The motion of the proof mass is detected by the pick-off system- The amount of force required to move the mass back to the null position is proportional to the applied acceleration

Pendulum

Feedbackelectronics

Electromagnetic restoring coil

Measure

Accelerometers - current technology

34

"Dry" close loop pendulous accelerometercapacitive pickoff - squeeze film damping

AccelerometersHinges

Flexures

Forcer coil

Capacitive electrode

Pendulum Proof mass

35

Vibrating beam accelerometer (VBA)

ONERA prototype

Finite element design

Quartz wafer

PrototypeTHALES’ A100

36

MEMS Accelerometers

5 mg class

Aéronautique

SCA30003-axis, 0,01 g class

CMA30003-axis, low power, 0,01 g class

37

Accelerometers

Other examples of products

38

Accelerometers - data

HONEYWELL (ex ALLIED SIGNAL)

Q-flex Familyhttp://www.inertialsensor.com/

Répétabilité sur un an Bias µg

S. Fact ppm

Range g

Space Navigation 40 80 60 Inertial Navigation 160 310 60

MWD (Measurement While Drilling-forage)

450 450 20

Lab. measurement 1 000 1 000 60 Industrial 1 200 1 200 30

High g navigation 1 500 1 500 90 Precise motion control 2500 2500 30

VBA 4 000 450 70

23 1

Repeatability over 1 year

39

Pendulous Accelerometers QA 2000

Accéléromètres pendulaireQ-Flex (Honeywell - previously AlliedSignal or Sundstrand)

40

Accelerometers

MODVIIA - A206C360"TRIAD ASSEMBLY"

3 acc. mounted perpendicular to each other

41

RAMENSKOYE

Repeatability Bias S. Fact Rangeover 1 year µg ppm g

A-15 300 200 10A-16 300 200 35A-17 (thermostated) 300 200 10

Accelerometers

42

• Usually protected from physical shock by small, high quality packages with thick, contour-fitted, foam lining

• Documentation on the accuracy of each individual accelerometer is usually contained in its package

• High quality electrical connections• Precision mounting surfaces for accurate alignment

Accelerometers

43

Rate gyros

Gyroscopes

44

Gyros : international definition (IEEE Std528)

Definition (IEEE Std528) ; Gyro : an inertial sensor that measures angular rotation about an (the) input axis (axes) .

Gyroscope : direction reference or angle measurementRate gyro : angular rate measurementGyro = gyroscope or rate gyro

sensorS

output

Ωrotation speed

Gyro output S : analog or digital (volts, amperes, frequency or bits)

Rotation to be measured on the input axis W : usually expressed in °/s or rad/s

45

Gyros : different technologies

Spinning wheelGyrosAngular

momentum, gyroscopic effect

Spinning wheelGyrosAngular

momentum, gyroscopic effect

Optical gyrosRing Laser Gyros (RLGs)Fiber Optic Gyros (FOGs)

(Sagnac Effect)

Optical gyrosRing Laser Gyros (RLGs)Fiber Optic Gyros (FOGs)

(Sagnac Effect)

Coriolis Vibratory Gyros(CVGs)

Coriolis Effect

Coriolis Vibratory Gyros(CVGs)

Coriolis Effect

Three physical principles

46

History

Single-axis floated gyroscopes

Two-axis Dynamically Tuned Gyros

Ring Laser Gyros

Fiber Optic Gyros

Coriolis Vibratory Gyros

1960 1970 1980 1990 2000 2010 2020

47

Gyro performance requirements vs applications

48

Gyroscopes, Rate gyros

Spinning wheels gyroscopes Angular momentum gyroscopic effect

= × Ω

49

Spinning wheel gyros : operating modes

Gyroscope :spin axis aligned in the desired direction,gimbals servoed to maintain the case in a fixed position relative

to the spin axis direction,gyro case is then the attitude reference,

Rate gyro :servo loop using the detector information to apply a torque to the

spinning wheel,voltage or current applied to the torquer is the angular rate

measurement,

Note : a gyroscope is more easily tested in the rate gyro mode

50

Spinning wheel gyros : typical form factors

Spinning wheel gyro :

51

Moteurd’entraînementlié au boîtier

Flexures isolate rotors from shaftFlexures isolate rotors from shaft

Dynamically tuned gyros (1960 …)

52

Dynamically tuned gyros : applications

A few DTGs…

S040

GYCAS

DTG 2000

GILDAS 3

G2000

GAM 5

• INS for aircraft

• IMU for missiles

• Satellite stabilization

• Radar or IR sensor stabilization for tactical missiles

53

Dynamically tuned gyros : example

Russian technology

54

Motor (small size, coil winding, efficiency)

Bearings (very small size, ball race material)

Greasing, lubrication (bearings) : fluidity over the temperature range, especially in non

temperature controlled systems

no migration

Machining : high precision tools,

many small pieces with stringent tolerances

Balancing (dynamic balancing, small masses, high speed)

Tuning (Dry Tuned Gyros : tuning frequency has to be measured and adjusted)

Clean rooms

Filling (dry air or low pressure or inert gas)

Gyros : critical points, spinning wheel

55

Optical gyros : RLGs, FOGs

Sagnac effect (needs relativistic theory) two laser beams or stationary laser waves interfere clockwise and

counterclockwise

the time difference between them is a function of t he rotation rate

Ω=∆ ..4

c

Sp

56

Optical gyros

Fiber optics gyros A coherent laser source is split into two

beams. The beams are guided through a fiber coil, clockwise and counterclockwise.

Signal detected : relative phase of the two beams, as they interfere.

Ω=∆ ..

...2

c

DL

λπϕ

57

Gyros : typical external shape

Fiber Optics Gyros

58

Gyros : critical points, FOGs

Critical components :Fiber (best performances with polarization maintaining fibers),IOC (Integrated Optic Chip : except for low performance open

loop design),Light source

Electronics (best performances with closed loop electronics)Optical connections (alignments, slant angle polish)Fiber coil winding

59

Optical gyros

RLGs

Ω=∆ ..

.4

λp

Sf

60

Samples of RLGs

61

Gyros : typical form factor

RLGs : usually not sold as a unique sensor, sold in IMUs and navigation systems

62

Gyros : critical points, RLGs

Clean rooms

Machining :Small diameter gain tubeOptimised aperture (size and position)

Mirrors :Highest quality dielectric mirrorsNeed of planar, curve and transmitting

mirrorsOptical contact

Cleaning after machining (before optical contact and gas filling)

Filling (He-Ne gain medium)

63

Gyro : CVG, principle of operation

Two cases :

Ω∧−=rrr

VmF 2

Free oscillation (Foucault pendulum : 1951)

Coriolis forces

64

CVGs Usually electronics

inside Analog output Many different

shapes

Systron Donner

Gyros : CVG, main parts

BAE Sumitomo

Delco

65

Gyros : critical points, CVGs

Machining (3D designs)

Performances (design)

Electronics

66

Micro-machined gyros : typical form factor

CVGs, MEMS :

67

Micro-machined gyros : MEMS technology

CRS04(BAE-Sumitomo)

CRS02(BAE-Sumitomo)

SiL(THALES)

CVG(Institut d’Electronique

Fondamentale)

ADXRS (Analog Devices)

68

MEMS gyros : applications

Crossbow AHRS, world first FAA certified MEMS inertial equipment

CRPA-MEMS IMUSegway system(BAE-Sumitomo MEMS sensors)

69

Performancesof accelerometers and gyros

70

Accelerometers : global error model

321

K

321

r

43421

r

321

r

r

NLnoise term shortntsmisalignme

factors, scalebias

++⋅+= aaaa fKb νε

Link to appendix : Sensor performance modeling

fr

aff εrrr

+=measured

zzyyxx efefeff ′+′+′= rrrr

meas, meas, meas,meas

xe 'r

ye 'r

ze 'r

xx eff ′⋅= rr

meas,

yy eff ′⋅= rr

meas,

zz eff ′⋅= rr

meas,

71

Gyros : global error models

RLGs

Spinning wheels

321

K

43421

rr

43421

r

321

r

r

NLdrift wheelspinningityorthogonal-non factors, scalebias

+×+⋅+= fBKb ibg /ωε

321

K

321

r

43421

r

321

r

r

NL

counting rays ceinterferen to due

noise whiteityorthogonal-non

factors, scalebias

++⋅+= νε ibg Kb /ω

Link to appendix : Sensor performance modeling

ωr

gεωω rrr

+=measured

zzyyxx eee ′′+′′+′′= rrrr ωωωωmeasured

72

Inertial Sensor Testing

73

Several phases :

Tests under gravity (+/- 1g) Scale Factor & Bias Temperature Electromagnetic

compatibility Magnetic induction Pressure (high, low)

Centrifuge tests

Vibrations & shocks

Accelerometers testing

74

Multiposition test(+g, -g, 0 g) ⇒⇒⇒⇒ scale factor - bias

Positioning accuracy :

precision round steel table Rotate and locked in a specific direction

repeatedly "Tumble testers" "Indexing heads" "Positioning tables" "Dividing heads"

Accelerometers testing

Temperature-controlledchamber

Seismic marble isolated from the building floor

for accurate measurements

75

Acceleration = R . ω² R : arm length ω² : angular rotation speed

Acceleration test : to confirm the ability of the sensor to withstand the acceleration forces expected during flight

Accelerometers testing

76

Vibrations electrodynamics vibrator - vertical and

horizontal Variable sinusoidal signal (bandwidth) Random vibration profile 20 Hz to 2 000 kHzShocks 900 g - 1/2 sinus - several msShaker 20 Hz to 50 kHz - 10 g for environmental

measurements

Vibration test :

to confirm the ability of the sensor to withstand the vibration forces expected during flight

Accelerometers testing

77

Gyroscopes & rate gyros : testing

78

Inertial Navigation Systems

Centrale SEXTANT SIRAL

Integrated INS/GPS miniature navigation system, ELEKTROPRIBOR, Russia

120 mm

Sigma 40DX

Sigma 95

MARINS

EPSILON 10

KN-4072A

LN120G LASEREF VI

QUASAR 3000

ADIRU