1) An autopilot controls the pitch and yaw motion of a missile to follow the main guidance loop. Pitch and yaw autopilots are called lateral autopilots. 2) Static margin refers to the distance between a missile's center of pressure and center of gravity. A positive static margin means the center of pressure is behind the center of gravity, making the missile statically stable. 3) There are two main control methods - Cartesian control uses two pairs of control surfaces and independent pitch and yaw control, while polar control uses roll to steer and only one pair of control surfaces. Polar control has advantages in weight and drag.

1. Missile control
CP -11

2. Autopilots
An autopilot is a closed loop system and it is a minor loop inside the main guidance loop; not all
missile systems require an autopilot. The autopilots are designed to control the motion in the
pitch and yaw planes, in which they are called lateral autopilots,( mainly due to symmetry of the
missile Pitch and Yaw auto pilots are known as Lateral autopilots) or they control the motion
about the fore and aft axis in which case they are called roll autopilots.

5. Static Margin
The degree of pitch stability can be quantitatively expressed by an index called static margin,
which is the distance of the center of pressure (c.p.) to the center of gravity (c.g.). The c.p. is
the point through which the combined aerodynamic forces caused by body, wings, and
control surfaces are acting.
If c.p. is behind the c.g. (i.e., the static margin is positive), the missile is said to be statically
stable. I

6. Cartesian Control
In a Cartesian system, the guidance angular
error detector produces two signals, a left-right
signal and an up-down signal, which are
transmitted to the missile. The method is also
called skid-to-turn (STT) method.
Here there are two pairs of control surfaces.
Hence there will be two lift forces acting in
perpendicular directions simultaneously and
independently say Fx and Fy.
The resultant of Fx and Fy, say F, will help
missile to
move towards target.
Polar Control
The same information could be expressed in polar
coordinates i.e., R and Ჶ.
The method is called polar control or twist and steer method or
bank-to-turn (BTT) method.
the missile will roll by and angle
and so lift changes from say from L to L0.

7. Advantages of Polar Control over Cartesian control
(a) Weight is less due to elimination of one pair of control
surfaces.
(b) Drag also is less due to only one pair of control
surfaces.
(c) Due to the above reasons, payload can be increased.
Controlled maneuvers are not precise since roll, yaw and pitch
are simultaneously
coupled or roll, pitch and yaw are cross-coupled. Due to this,
the system becomes
a multivariable system with three inputs and three outputs.
Hence calculation of
output is not very accurate and the maneuver will not be
precise.
It is found that the polar control is a slow process since the full
maneuver cannot take place until the full bank angle is
achieved.
majority of missiles use Cartesian control method.

8. Advantages of Cartesian control
(a) Pitch and yaw channels can be considered as independent two-dimensional problem
with roll being zero unless purposefully introduced. Hence system is more accurate.
(b) Thus Cartesian method is a quicker method of moving laterally in any one direc-
tion. Also analysis of the performance of Cartesian system is simpler.
(c) Polar control cannot be used where roll stabilization is required (in case of homers
where high roll rate may disturb the homing head).
(d) With a Cartesian control system, the pitch control system is made identical to the
yaw control system. Hence we need to discuss one channel only and with missiles,
lateral movement usually means up-down or left-right.

9. Tail Control
control provides excellent manoeuvrability at high angles of attack, to
intercept a highly manoeuvrable aircraft. These missiles have non-movable
wings to provide additional lift and improve range. Tail control provides lot of
convenience in placing the propellant, warhead and guidance system in the
missile.
In subsonic missiles, the controls are used as “flaps"
immediately behind the wings.
In supersonic missiles, the tail control surfaces are placed
as far as possible at the rear, to exert maximum moment on
the missile.

10. Canard Controlled
They are commonly used in short- range air-to-air missiles
The primary advantage of canard control is better
manoeuvrability at low angles of attack
However to retain the stability in the canard configuration, the
missiles have large fixed tails kept at the rear, as far as possible.
Hence canard controlled missiles do not have conventional
wings..
Canard controlled missiles have difficulties in performing roll
control

11. Wing Controlled
The primary advantage of wing control is that the deflections of the wings produce a
very fast response with little motion of the body. This feature results in small seeker
tracking error and allows the missile to remain locked on to the target even during large
manoeuvres.
The major
disadvantage is that the wings must usually be quite large in order to generate both
suffcient lift and control effectiveness, which makes the missiles rather large overall.
Wing control also generates strong vortices that may
adversely interact with the tails causing the missile to roll, known as induced roll. If the
induced roll is strong enough, a separate control system is required to compensate it.

14. Primary Control Surfaces
Ailerons, rudders, elevators, canards,
and their various combinations are considered primary controls.. As these control surfaces
are deflected, they present a surface to the existing airflow at an angle that will cause a force
to exist. T
1. Ailerons. A conventional aileron is attached to the outer trailing edge of the wings to control the
missile row motion in a manner that when one aileron is lowered, the opposite one is raised. 2.
Elevators. Elevators are attached to the pitch stabilizer on the tail to control pitch motion. They are
raised and lowered together.
2. Rudders. A rudder is attached to the rear part of the vertical stabilizer and is used to maintain
directional (yaw) control.
Canards. A canard is basically a forward wing located ahead of the center of gravity of the missile for
the purposes of stabilization and pitch control.

15. Thrust Vector control

20. PID control T VC

21. Missile as a lumped system with mass m and moment
of inertia about the y-axis as Iyy .
V^.α is much smaller than V α^.
change in flight path occurs when L -W > 0 and the
corresponding flight trajectory would be curved.
For a constant flight path angle (

22. Drag Model
Pitching Moment