21-06-2014, 02:46 PM
ADAPTIVE MISSILE GUIDANCE USING GPS
[attachment=65161]
ABSTRACT
In the modern day theatre of combat, the need to be able to strike at targets that
are on the opposite side of the globe has strongly presented itself. This had led to the
development of various types of guided missiles. These guided missiles are self -guiding weapons
intended to maximize damage to the target while minimizing collateral damage. The buzzword in
modern day combat is fire and forget. GPS guided missiles, using the exceptional navigational
and surveying abilities of GPS, after being launched, could deliver a warhead to any part of the
globe via the interface pof the onboard computer in the missile with the GPS satellite system.
Under this principle many modern day laser weapons were designed. Laser
guided missiles use a laser of a certain frequency bandwidth to acquire their target. GPS/inertial
weapons are oblivious to the effects of weather, allowing a target to be engaged at the time of the
attacker's choosing. GPS allows accurate targeting of various military weapons including
ICBMs, cruise missiles and precision-guided munitions. Artillery projectiles with embedded
GPS receivers able to withstand accelerations of 12,000 G have been developed for use in 155
mm. GPS signals can also be affected by multipath issues, where the radio signals reflect off
surrounding terrain; buildings, canyon walls, hard ground , etc. These delayed signals can cause
inaccuracy. A variety of techniques, most notably narrow correlator spacing, have been
developed to mitigate multipath errors. Multipath effects are much less severe in moving
vehicles. When the GPS antenna is moving, the false solutions using reflected signals quickly
fail to converge and only the direct signals result in stable solutions. The multiple independently
targeted re-entry vehicles (MIRVs) – ICBMs with many sub-missiles – were developed in the
late 1960s. The cruise missile has wings like an airplane, making it ca pable of flying at low
altitudes. In summary, GPS-INS guided weapons are not affected by harsh weather conditions or
restricted by a wire, nor do they leave the gunner vulnerable for attack. GPS guided weapons,
with their technological advances over previous, are the superior weapon of choice in modern
day
INTRODUCTION
Introduction to missile guidance
Guided missile systems have evolved at a tremendous rate over the past four decades, and recent
breakthroughs in technology ensure that smart warheads will have an increasing role in
maintaining our military superiority. On ethical grounds, one prays that each warhead deployed
during a sortie will strike only its intended target, and that innocent civilians will not be harmed
by a
misfire. From a tactical standpoint, our military desires weaponry that is reliable and effective,
inflicting maximal damage on valid military targets and ensuring our capacity for light ingfast
strikes with pinpoint accuracy. Guided missile systems help fulfill all of these demands
Concept of missile guidance
The missile sensor or seeker, on the other hand, is a component within a missile that generates
data fed into the missile computer. This data is processed by the computer and used to generate
guidance commands. Sensor types commonly used today include infrared, radar, and the global
positioning system. Based on the relative position between the missile and the target at any given
point in flight, the computer autopilot sends commands to the control surfaces to adjust the
missile's course
INTRODUCTION TO GPS
What is meant by GPS
GPS, which stands for Global Positioning System, is the only system today able to show us our
exact position on the Earth anytime, in any weather, anywhere. GPS satellites, 24 in all, orbit at
11,000 nautical miles above the Earth. Ground stations located worldwide continuously monitor
them. The satellites transmit signals that can be detected by anyone with a GPS receiver. Using
the receiver, you can determine your location with great precision
Elements of GPS
GPS has three parts: the space segment, the user segment, and the control segment. The space
segment consists of a constellation of 24 satellites plus some spares, each in its own orbit 11,000
nautical miles above Earth. The user segment consists of receivers, which we can hold in our
hand or mount in a vehicle. The control segment consist, of ground stations that make sure the
satellites are working properly.
2 Mechanical, fiber optic, and ring laser gyroscopes
The purpose of a gyroscope i s to measure angular rotation, and a number of different
Methods to do so have been devised. A classic mechanical gyroscope senses the stability of a
mass rotating on gimbals. More recent ring laser gyros and fiber optic gyros are based on the
interference between laser beams. Current advances in Micro-Electro-Mechanical Systems
(MEMS) offer the potential to develop gyroscopes that are very small and inexpensive While
gyroscopes measure angular motion, accelerometers measure linear motion. The accelerations
from these devices are translated into electrical signals for processing by the missile computer
autopilot. When a gyroscope and an accelerometer are combined into a single device along with
a control mechanism, it is called an inertial measurement unit (IMU) or inertial navigation
Fig.1.3 Inertial navigation concept
The INS uses these two devices to sense motion relative to a point of origin Inertial navigation
works by telling the missile where it is at the time of launch and how it should move in terms of
both distance and rotation over the course of its flight. The missile computer uses signals from
the INS to measure these motions and insure that the missile travels along its proper -
programmed path. Inertial navigation systems are widel y used on all kinds of aerospace vehicles,
including weapons, military aircraft, commercial airliners, and spacecraft. Many missiles use
MISSILE GUIDANCE USING GPS
The central idea behind the design of DGPS/GPS/inertial guided weapons is that of using a 3-
axis gyro/accelerometer package as an inertial reference for the weapon's autopilot, and
correcting the accumulated drift error in the inertial package by using GPS PPS/P-code. Such
weapons are designated as "accurate" munitions as they will offer CEPs (Circular Error
Probable) of the order of the accuracy of GPS P -code signals, typically about
. Global Positioning System used in ranging navigation guidance .
The next incremental step is then to update the weapon before launch with a DGPS derived
position estimate, which will allow it to correct its GPS error as it flies to the target, such
weapons are designated "precise" and will offer accuracies greater than laser or TV guided
weapons, potentially CEPs of several feet. For an aircraft to support such munitions, it will
require a DGPS receiver, a GPS receiver and interfaces on its multiple ejector racks or pylons to
download target and launch point coordinates to the weapons. The development of purely
GPS/inertial guided munitions will produce substantial changes in how air warfare is conducted.
Unlike a laser-guided weapon, a GPS/inertial weapon does not require t hat the launch aircraft
remain in the vicinity of the target to illuminate it for guidance - GPS/inertial weapons are true
fire-and-forget weapons, which once released, are wholly autonomous, and all weather capable
with no degradation in accuracy. Existin g precision weapons require an unobscured line of sight
between the weapon and the target for the optical guidance to work.
CONCLUSIONS
The proliferation of GPS and INS guidance is a double-edged sword. On the one hand, this
technology promise a revolution in air warfare not seen since the laser guided bomb, with single
bombers being capable of doing the task of multiple aircraft packages. In summary, GPS-INS
guided weapons are not affected by harsh weather conditions or restricted by a wire, nor do they
leave the gunner vulnerable for attack. GPS guided weapons, with their technological advances
over previous, are the superior weapon of choice in modern day warfare
[attachment=65161]
ABSTRACT
In the modern day theatre of combat, the need to be able to strike at targets that
are on the opposite side of the globe has strongly presented itself. This had led to the
development of various types of guided missiles. These guided missiles are self -guiding weapons
intended to maximize damage to the target while minimizing collateral damage. The buzzword in
modern day combat is fire and forget. GPS guided missiles, using the exceptional navigational
and surveying abilities of GPS, after being launched, could deliver a warhead to any part of the
globe via the interface pof the onboard computer in the missile with the GPS satellite system.
Under this principle many modern day laser weapons were designed. Laser
guided missiles use a laser of a certain frequency bandwidth to acquire their target. GPS/inertial
weapons are oblivious to the effects of weather, allowing a target to be engaged at the time of the
attacker's choosing. GPS allows accurate targeting of various military weapons including
ICBMs, cruise missiles and precision-guided munitions. Artillery projectiles with embedded
GPS receivers able to withstand accelerations of 12,000 G have been developed for use in 155
mm. GPS signals can also be affected by multipath issues, where the radio signals reflect off
surrounding terrain; buildings, canyon walls, hard ground , etc. These delayed signals can cause
inaccuracy. A variety of techniques, most notably narrow correlator spacing, have been
developed to mitigate multipath errors. Multipath effects are much less severe in moving
vehicles. When the GPS antenna is moving, the false solutions using reflected signals quickly
fail to converge and only the direct signals result in stable solutions. The multiple independently
targeted re-entry vehicles (MIRVs) – ICBMs with many sub-missiles – were developed in the
late 1960s. The cruise missile has wings like an airplane, making it ca pable of flying at low
altitudes. In summary, GPS-INS guided weapons are not affected by harsh weather conditions or
restricted by a wire, nor do they leave the gunner vulnerable for attack. GPS guided weapons,
with their technological advances over previous, are the superior weapon of choice in modern
day
INTRODUCTION
Introduction to missile guidance
Guided missile systems have evolved at a tremendous rate over the past four decades, and recent
breakthroughs in technology ensure that smart warheads will have an increasing role in
maintaining our military superiority. On ethical grounds, one prays that each warhead deployed
during a sortie will strike only its intended target, and that innocent civilians will not be harmed
by a
misfire. From a tactical standpoint, our military desires weaponry that is reliable and effective,
inflicting maximal damage on valid military targets and ensuring our capacity for light ingfast
strikes with pinpoint accuracy. Guided missile systems help fulfill all of these demands
Concept of missile guidance
The missile sensor or seeker, on the other hand, is a component within a missile that generates
data fed into the missile computer. This data is processed by the computer and used to generate
guidance commands. Sensor types commonly used today include infrared, radar, and the global
positioning system. Based on the relative position between the missile and the target at any given
point in flight, the computer autopilot sends commands to the control surfaces to adjust the
missile's course
INTRODUCTION TO GPS
What is meant by GPS
GPS, which stands for Global Positioning System, is the only system today able to show us our
exact position on the Earth anytime, in any weather, anywhere. GPS satellites, 24 in all, orbit at
11,000 nautical miles above the Earth. Ground stations located worldwide continuously monitor
them. The satellites transmit signals that can be detected by anyone with a GPS receiver. Using
the receiver, you can determine your location with great precision
Elements of GPS
GPS has three parts: the space segment, the user segment, and the control segment. The space
segment consists of a constellation of 24 satellites plus some spares, each in its own orbit 11,000
nautical miles above Earth. The user segment consists of receivers, which we can hold in our
hand or mount in a vehicle. The control segment consist, of ground stations that make sure the
satellites are working properly.
2 Mechanical, fiber optic, and ring laser gyroscopes
The purpose of a gyroscope i s to measure angular rotation, and a number of different
Methods to do so have been devised. A classic mechanical gyroscope senses the stability of a
mass rotating on gimbals. More recent ring laser gyros and fiber optic gyros are based on the
interference between laser beams. Current advances in Micro-Electro-Mechanical Systems
(MEMS) offer the potential to develop gyroscopes that are very small and inexpensive While
gyroscopes measure angular motion, accelerometers measure linear motion. The accelerations
from these devices are translated into electrical signals for processing by the missile computer
autopilot. When a gyroscope and an accelerometer are combined into a single device along with
a control mechanism, it is called an inertial measurement unit (IMU) or inertial navigation
Fig.1.3 Inertial navigation concept
The INS uses these two devices to sense motion relative to a point of origin Inertial navigation
works by telling the missile where it is at the time of launch and how it should move in terms of
both distance and rotation over the course of its flight. The missile computer uses signals from
the INS to measure these motions and insure that the missile travels along its proper -
programmed path. Inertial navigation systems are widel y used on all kinds of aerospace vehicles,
including weapons, military aircraft, commercial airliners, and spacecraft. Many missiles use
MISSILE GUIDANCE USING GPS
The central idea behind the design of DGPS/GPS/inertial guided weapons is that of using a 3-
axis gyro/accelerometer package as an inertial reference for the weapon's autopilot, and
correcting the accumulated drift error in the inertial package by using GPS PPS/P-code. Such
weapons are designated as "accurate" munitions as they will offer CEPs (Circular Error
Probable) of the order of the accuracy of GPS P -code signals, typically about
. Global Positioning System used in ranging navigation guidance .
The next incremental step is then to update the weapon before launch with a DGPS derived
position estimate, which will allow it to correct its GPS error as it flies to the target, such
weapons are designated "precise" and will offer accuracies greater than laser or TV guided
weapons, potentially CEPs of several feet. For an aircraft to support such munitions, it will
require a DGPS receiver, a GPS receiver and interfaces on its multiple ejector racks or pylons to
download target and launch point coordinates to the weapons. The development of purely
GPS/inertial guided munitions will produce substantial changes in how air warfare is conducted.
Unlike a laser-guided weapon, a GPS/inertial weapon does not require t hat the launch aircraft
remain in the vicinity of the target to illuminate it for guidance - GPS/inertial weapons are true
fire-and-forget weapons, which once released, are wholly autonomous, and all weather capable
with no degradation in accuracy. Existin g precision weapons require an unobscured line of sight
between the weapon and the target for the optical guidance to work.
CONCLUSIONS
The proliferation of GPS and INS guidance is a double-edged sword. On the one hand, this
technology promise a revolution in air warfare not seen since the laser guided bomb, with single
bombers being capable of doing the task of multiple aircraft packages. In summary, GPS-INS
guided weapons are not affected by harsh weather conditions or restricted by a wire, nor do they
leave the gunner vulnerable for attack. GPS guided weapons, with their technological advances
over previous, are the superior weapon of choice in modern day warfare