lecture 1 : guidance system requirements
TRANSCRIPT
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Gerard Leng, MDTS, NUS
MDTS 5705 : GuidanceLecture 1 : Guidance System Requirements
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Gerard Leng, MDTS, NUS
Course Admin
Instructor : Gerard Leng
Office : E2 -02 - 37
Contact : phone 6 874 6548
fax 6 779 1459
e-mail [email protected]
Consultation : Mon-Fri 12-2pm (happy hour)
Course Website : dynlab.mpe.nus.edu.sg/mpelsb
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Gerard Leng, MDTS, NUS
Course Outline
Topics
1 : Guidance System Requirements
2 : Line-of-sight Guidance
3 : Homing Guidance
4 : INS/GPS Guidance
Course Organisation
4 lectures/tutorial
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Gerard Leng, MDTS, NUS
Course Objectives & Requirements
1. Understand theoretical guidance concepts
2. Relate these concepts to practical weapon systems
Required Background
Basic engineering or science degree
( calculus, differential equations, particle dynamics )
Some programming experience ( eg : Matlab )
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Gerard Leng, MDTS, NUS
Text
P. Garnell & D.J. East, Guided Weapon Control Systems, Pergamon
Press, 1977
A.S. Locke, Guidance, Principles of Guided Missile Design, van
Nostrand, 1955
E. Fleeman, Tactical Missile Design, AIAA, 2006
P. Zarchan, Tactical and Strategic Missile Guidance , AIAA Progress in
Astronautics & Aeronautics, v239, (6th edition), 2012
Recommended references
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Gerard Leng, MDTS, NUS
Grading Policy
“Proposed” grading - Plan A
Project 40%
Final Exam 60%
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Gerard Leng, MDTS, NUS
1.0 What is a guided weapon ?
Guided Weapon = Sensors (Eyes & Ears)
+ Guidance Logic (Brain)
+ Control & Propulsion (Muscles)
+ Warhead
In other words ….
A guided weapon is a weapon system that can
correct its course to hit a target
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Gerard Leng, MDTS, NUS
Example : The earliest guided bomb
WWII German Fritz X
Specifications
• Weight 1300 kg, 270 kg AP warhead
• Wing span 1.6 m
• Guidance joy stick, radio link
• Range 5.6 km
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Gerard Leng, MDTS, NUS
Example : The earliest guided missile
WWII German HS 293
Specifications
Launch weight 1045kg, 295 kg HE warhead
Wing span 3.10m
Guidance joy stick, radio/wire link
Propulsion rocket
Range 18 km
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Gerard Leng, MDTS, NUS
Question : What can we observe & conclude from
these early guided weapons ?
A guided weapon doesn’t have to be really “high-tech” or even
autonomous
So can we build one with commercial-off-the-shelf (COTS)
components ?
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Gerard Leng, MDTS, NUS
1. 1 Mission profile of guided weapons
1.1.0 Guided weapons with different missions
• Anti Tank Guided Missile ATGM
• Air to Ground Missile AGM
• Anti-Ship Missile ASM
• Surface to Air Missile SAM
• Air Interdiction, Air-to-Air Missile AIM, AAM
• Anti-Missile Missile AMM
• Unmanned Combat Air Vehicles UCAV
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Gerard Leng, MDTS, NUS
1.1.1 Anti-Tank Missile Mission Profile
Question :Is a direct head on impact the most effective way for an ATGM
to destroy a tank ?
1. missile aligned with tank 2. head -on impact on the front hull
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Gerard Leng, MDTS, NUS
What is the best way to destroy a tank ?
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Gerard Leng, MDTS, NUS
Russian MBT T-72
Basic protection : 520mm - 590mm turret armour against HEAT
Main armament : 125-mm gun with range of 2000 m
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Gerard Leng, MDTS, NUS
Question : Where should the ATGM hit ?
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Gerard Leng, MDTS, NUS
ATGM flight trajectories
2. Elevated - Hellfire
1. Direct - Milan
3. Arched - Javelin
What’s this ?
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1.1.2 Anti-tank missile guidance requirements
2. Attack armoured targets at the weakest point (top armour)
1. Additional protection eg : ERA (explosive reactive armour)
3. Guidance design implications :
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Gerard Leng, MDTS, NUS
1.2 What is the best way to destroy a ship ?
1.2.0 Warships can detect and defend against in-coming missiles
A : detection & launch
B : align with intercept plane
C : intercept course
D : target neutralised
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1.2.1 Anti Ship Missile Mission Profile
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1.2.2 Anti-ship missile guidance requirements
More complicated guidance design for different phases of mission
launch : dive/climb
mid-course : altitude hold
tactical maneuvers
terminal : pop-up
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Gerard Leng, MDTS, NUS
1.3 How to destroy an in-coming missile ?
1.3.0 Problems
Target can be as fast as your missile
Target may approach from any direction
Target can perform evasive maneuvers
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Gerard Leng, MDTS, NUS
1.3.1 Anti-Missile Missile Mission Profile
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Gerard Leng, MDTS, NUS
1.3.2 AMM guidance requirements
Vertical launch to “optimal” altitude
Tip-over to correct plane for interception
Mid course guidance to close with target.
Terminal guidance to counter evasive maneuvers
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Gerard Leng, MDTS, NUS
1.4 What are the guidance requirements for a UCAV
or a cruise missile ?
X45 X47
Hint : What kind of targets are suitable for UCAV or cruise missiles ?
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Gerard Leng, MDTS, NUS
1.4.1 UCAV/Cruise Missile Mission Profile
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Gerard Leng, MDTS, NUS
1.4.2 Cruise missile, UCAV guidance requirements
1. Long range, low-level terrain hugging flight
2. Best used against large stationary targets
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Gerard Leng, MDTS, NUS
1.5 The First Lesson of Guidance System Design
The design of the guidance system must suit the
mission profile and must function within the
limits of available sensors and controls
To paraphrase Sun Tze’s Art of War
Know your guided weapon, know your target.
In a 100 firings, you get a 100 hits (or close)
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1.6 Basic Trajectory Analysis
q
g
R
V
a
OI
J
P
(1) Position of P
X = R cosq
Y = R sinq
1.6.0 Kinematics
(2) Velocity of P
X’ = V cosg
Y’ = V sing
X
Y
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Gerard Leng, MDTS, NUS
1.6.1 Turn rate and latax
1. Differentiate eqns (1)
X’ = cosq -sinq R’
Y’ sinq cosq Rq’
2. Substitute eqns (2)
Vcosg = cosq -sinq R’
Vsing sinq cosq Rq’
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Gerard Leng, MDTS, NUS
Inverting
R’ = V cos(g - q )
R q’ = V sin(g - q )
3. Conclusions :
a) The velocity component parallel to OP affects the rate of change of
OP
b) The velocity component perpendicular to OP affects the rotation rate
of OP
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Gerard Leng, MDTS, NUS
4. From the diagram, the lateral acceleration a = a { -sin g, cos g }
Differentiate eqns (2),
X’’ = cosg -sing V’
Y’’ sing cosg V g ’
5. Noting that the LHS is the lateral acceleration a …
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Gerard Leng, MDTS, NUS
We obtain
V’ = 0
V g ’ = a
6. Conclusion
The (applied) lateral acceleration (latax) changes the turn rate but not
the speed
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Gerard Leng, MDTS, NUS
Exercise : Getting a physical feel for the math
A fighter aircraft flying at 180 m/s (Mach 0.6) executes a 9g turn.
What is the turn rate ?
Noting that V g ’ = a
m V g ’ = ma = 9 mg
Hence g ’ =
=
=
=
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Gerard Leng, MDTS, NUS
Exercise : Estimating performance Aster 30 AMM
Reported : Dec 1997 test firing of the Aster 30 AMM
Intercepted target from above at Mach 2.68
miss distance < 4 m
max load = 60 g’s
What’s the turn rate ?
max turn rate =
=