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G. Leng, MDTS, NUS MDTS 5705 : Control Lecture 1 : Missile control configurations

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Page 1: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

MDTS 5705 : ControlLecture 1 : Missile control configurations

Page 2: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

References

• G. M.. Siouris, “Missile Guidance and Control Systems”,

Springer-Verlag, 2004

• B. Stevens. "Aircraft Control & Simulation", J. Wiley,

1992.

• D. McRuer, I. Askenas & D. Graham, "Aircraft Dynamics

and Automatic Control“, Princeton University Press, 1973

Page 3: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Training Programme

1 : Missile control configurations

or making sense of the aerodynamics for flight control

2 : Missile dynamics and control models

or when to simplify, when to stop and how to simulate

3: Designing the flight control system

or defining the control limits of the missile

Page 4: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.1.1 : A first step is to define a convenient axis system or

reference frame fixed to the missile.

Question : Why fixed to the missile ?

1.1 : Axes System

Page 5: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

x

z

1.1.2 : Body axes

yy

The convention for flight dynamics is :

I) The positive x axis points towards the nose

II) The positive y axis points to the right

III) The positive z axis points downwards.

Note that this is a right handed

coordinate system.

Question : Where should the

origin be placed ?

Page 6: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.1.3. The set of axes as defined in 1.1.2 is called the body axes. It is fixed to the missile and translates and rotates with it.

Question : Implications for equations of motion ?

Page 7: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.1.4 : Aerodynamics axes

Question : Why do the axes point

this way ?

x

z

y

y

Typically, aerodynamicists and structural engineers use different

conventions for their axis systems creating unnecessary

confusion

Page 8: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.1.5. Using the body axes, the missile's velocity V is written

as V = {u, v, w} where

u, v, w

are the velocity components in the X,Y,and Z axes direction.

Page 9: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

x

z

Figure 1.1.1 : Velocity components

y

v

w

u

V

Page 10: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.1.6. Similarly we denote the missile's rotation with an

angular velocity vector = {p, q, r } where p, q, r, are the

roll (wings up/down)

pitch (nose up/down)

yaw (nose right/left)

rotational rates.

Page 11: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

x

z

Figure 1.1.2 : Angular velocity components

yp roll rate

r yaw rate

q pitch rate

Page 12: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.2 : Aerodynamic Forces and Moments

1.2.1. Aerodynamic forces and moments on the missile depend

on the orientation of the missile with respect to the flight

trajectory

1.2.2. This orientation is specified by the two important angles

: angle of attack

: sideslip angle

Page 13: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

v

u

w

Figure 1.2.1 : AOA & sideslip angle definition 1

V

Page 14: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

v

u

w

Figure 1.2.1 : AOA & sideslip angle – definition 2

V

s

Question : Can you spot the difference ?

Page 15: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Example : Aerodynamic database

How does the aerodynamics vary for a real missile ?

Page 16: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Example – CZ variation

Page 17: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Example - Cm variation

Question : Why must Cm vary this way with AOA ?

AOA

Cm

e

trim pt

Page 18: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

How does one “control” a missile ?

Maverick

Sidewinder

Control

surfaces

Control

surfaces

Page 19: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Missile aerodynamic control surfaces

servo motor

control

surface

hinge

line

Page 20: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

• Deflection of control surfaces changes aerodynamic forces acting on the surface

• Changes in forces generate moments about the cg which roll, pitch and yaw the missile

• How well does this work ?

• Can you estimate the aerodynamic control forces on a missile ?

Basic aerodynamic control technique

Page 21: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Ex : Control force estimation

• AIM 9 @ Mach 2.5

• Triangular fin

• Area = ½ x 0.3 x 0.3

= 0.045 m2

Force =

=

=

Page 22: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Examples of missile control surfaces

• Foldable fins

• Tube launched weapons

Page 23: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Examples of missile control surfaces

• Lattice control surface

• AA-12 Adder

Page 24: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Performance implications 1

Tail control missile

Lw

W Lt

So what’s the problem ?

Page 25: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Non–minimum phase response

time

commanded

latax

actual latax

Initial response heads off in the wrong direction

Page 26: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Performance implications 2

Canard control missile

Lw

W

Lc

Comments ?

Page 27: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Ex : Comment on the control configuration of this missile

Page 28: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Multi-control surfaces - Rafael Python 4

Page 29: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Page 30: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.3 Missile control methods - examples

ailerons

rudder

elevator

Where are the control surfaces ?

Page 31: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.3.1 Cartesian control for homing

• Separate sets of control surfaces

for pitch (up/down) and yaw

(left/right)

• Guidance generates required

latax for pitch and yaw planes

• Pitch and yaw controls can act

simultaneouslytarget

Page 32: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

Missile control methods - example

Moving wings serve as both

ailerons and elevators

Fixed tail surfaces

Question : What can of control

method was employed ?

Page 33: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.3.2 Polar control for homing

• Guidance generates

roll command and

required pitch latax

(twist & steer)

• Needs roll angle

reference

• How fast is the

missile response ?

target

target

Page 34: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.3.3 Skid to turn for mid-course

• Turn executed by

“skidding” the missile

• Hence missile is not

aligned with velocity

vector during turn

• Typically used for fast

turn response

• May lead to large AOA &

sideslip – problems ?

Page 35: MDTS 5705 : Controldynlab.mpe.nus.edu.sg/mpelsb/mdts/Control 1n v2.pdf · MDTS 5705 : Control Lecture 1 : Missile control ... Siouris, “Missile Guidance and Control Systems”,

G. Leng, MDTS, NUS

1.3.4 Bank to turn for mid course

• Missile rolls to vector lift

• Missile is aligned with velocity vector during turn

• Small AOA & sideslip

• Why bank to turn ?