98451138 Missile Guidance

7/28/2019 98451138 Missile Guidance

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By:

Gaurav Kumar Verma


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Missile

Missile may be anythrown or launchedobject, it colloquiallyalmost always refers

to a self-propelled guidedweapon system.


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Targeting and/or guidance

Flight system

Engine

Warhead


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Surface-to-Surface/Air-to-Surface

1. Ballistic2.Cruise

3. Anti-ship

4. Anti-tank

Surface-to-air

1.Anti-aircraft2. Anti Ballistic


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Missile guidance refers to a variety ofmethods of guiding a missile or a guidedbomb to its intended target. The missile's

target accuracy is a critical factor for itseffectiveness. Guidance systems improvemissile accuracy


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A servomechanism, or servo, is an automaticdevice that uses error-sensing negativefeedback to correct the performance of a

mechanism.The term correctly applies only tosystems where the feedback or error-correctionsignals help control mechanical position, speedor other parameters.


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An autopilot is a mechanical, electrical, orhydraulic system used to guide a vehiclewithout assistance from a human being.

the autopilot refers to the missile airframedynamics and associated stabilityaugmentation system, which is designed sothat the missile lateral acceleration follows the

autopilot acceleration commands as closely aspossible


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1 Roll PositionAutopilot

2 Pitch autopilot

3 Yaw Autopilot


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The basic function of the roll autopilot is to roll-rate stabilize the missile, that is, to providemissile stabilization of roll attitude about the

longitudinal axis. This is accomplished bysensing roll rate, and using the signal to deflectthe fins (or wings) by an amount sufficient tocounteract roll disturbances.


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Airframe misalignments.

Asymmetrical loading of the lifting andcontrol surfaces at supersonic speeds.

Atmospheric disturbances, if the missileis made to fly close to the sea or ground.


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Basically, the pitch/yaw autopilots (also knownas lateral autopilots) each consist of a majoraccelerometer feedback loop that provides the

desired conversion of commanded accelerationto missile acceleration, and a minorratefeedback loop that provides the necessarydamping of missile pitch or yaw rates.


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Maintenance of near-constant steady stateaerodynamic gain.

Increase frequency.

Increase damping. Reduce cross-coupling between pitch and yaw

motion

Assistance in gathering.


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Thus we find that when the unmodelled dynamics of theservo and gyro are neglected, roll autopilot system is shownto be stable. However when the servo dynamics areincluded the system becomes unstable. Thus the role of thecontrol engineer is to design the system such as to make it

robustly stable. The system can be made stable by includinga phase lag network. However the phase margin that can beattained is very marginal and the bandwidth and gainmargin reduces. Control engineers design the phase marginto be at least 50 degrees and a bandwidth of around 150rad/s to overcome any possible unforeseen disturbance in

flight. Thus by including a phase lead network also, thephase margin of 46 degrees is attained which is consideredadequate. Also bandwidth is 147 rad/s at gain margin of 11dB, which is also adequate. In a similar manner, a lateralautopilot also can be designed to be robustly stable.

98451138 Missile Guidance

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