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Weapons ON Target. Learning Objectives Know the definitions of the following terms: input, output, feedback, error, open loop, and closed loop Comprehend.

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Presentation on theme: "Weapons ON Target. Learning Objectives Know the definitions of the following terms: input, output, feedback, error, open loop, and closed loop Comprehend."— Presentation transcript:

1 Weapons ON Target

2 Learning Objectives Know the definitions of the following terms: input, output, feedback, error, open loop, and closed loop Comprehend the advantages of closed- loop control in a weapon system Comprehend the difference between the line-of-sight (LOS) and the tracking line Comprehend the operation of a simple automatic tracking system

3 Control System Terminology INPUT – stimulus applied from external source OUTPUT – response obtained from a system FEEDBACK – portion of output returned to modify input ERROR – difference between the input and output (more specifically the feedback)


5 History of Feedback Control Water clock of the Greeks Industrial Revolution –Pressure Regulators –Water Regulators –Temperature Regulators Fantail

6 Example Thermostat (temperature control) –Input – temperature it is initially set to –Output – heating or cooling (exhaust) –Feedback – ambient room temperature –Error – difference between ambient temp and input (temp it is set to)

7 Thermostat Temp Wanted Air Temp Heater Control Example of Feedback Control System

8 Types of Control Systems Open-Loop Simple system which performs function without concern for initial conditions or external inputs Must be closely monitored Closed-Loop (feedback) Uses the output of the process to modify the process to produce the desired result Continually adjusts the process

9 Advantages of Closed-Loop Feedback System øIncreased Accuracy –Ability to reproduce output with varied input øReduced Sensitivity to Disturbance –Self-correcting minimizes effects of system changes øSmoothing and Filtering –System induced noise and distortion are reduced øIncreased Bandwidth –Produces satisfactory response to increased range of input changes

10 Major Types of Feedback Used øPosition Feedback –Used when the output is a linear distance or angular measurement. øRate & Acceleration Feedback –Feeds back rate of motion or rate of change of motion (acceleration) –Motion smoothing –Uses a electrical/mechanical device called an accelerometer

11 Building a Gun Fire Control System Job Description: Train the gun turret to the proper firing position by moving a joy stick left or right depending on the direction needed. This must be performed as fast as possible. Safety Consideration : For your protection, you will be located inside a windowless protective enclosure inside the gun turret.

12 Time Old Position New Position Turret Position with Feedback

13 Dampening Old Position New Position

14 Questions?

15 Automatic Tracking Systems Feedback Control Part II

16 Learning Objectives Comprehend the concepts, advantages, and limitations of conical scan, conical scan on receive only (COSRO), and monopulse Comprehend stabilization as associated with tracking systems Know the difference between range tracking and angle tracking

17 Automatic Tracking Systems (Related to Feedback) 1.Target Tracking Parameters 2. Line-of-Sight(LOS) 3. Tracking Line

18 Target Tracking Parameters ·Azimuth ·Elevation ·Range ·Relative Target Velocity -Targets motion with respect to the platforms motion

19 Tracking Terms Tracking Element Line-of-Sight Tracking Line Error Tracking line = antenna boresight Tracking line lags line-of-sight

20 Angle-Tracking Servo Systems Five Basic Functions Sense position error magnitude and direction Provide position feedback Provide data smoothing / stabilization Provide velocity feedback Provide a power-driving device

21 Basic Principle: Target energy return is strongest on the axis of the beam, diminishes further from the axis. axis Methods of Tracking: * Sequential Lobing * Conical Scan * COSRO * Monopulse Position Error Magnitude & Direction

22 Azimuth lobing A B Returns

23 Uses of Angle-Tracking Servo Systems Monotrack fire control radars Homing missiles Acoustic homing torpedoes Aviation fire control tracking systems

24 Methods of tracking Conical scan Conical scan on receive only (COSRO) Monopulse

25 Conical Scan Time Pulse Return Amplitude

26 Conical Scan Time Pulse Return Amplitude Time Pulse Return Amplitude

27 Sequential Lobing L L L R R R Antenna looking left of target Antenna Pointing directly at target Antenna looking right of target Return Signals form Two Beams * Simplest Method * Multiple Beams * Compare Returns * Relatively Slow * Still used by some countries

28 Conical Scanning * Rotates a beam in a circle producing a cone of energy. *Rotate the feed horn in a small circle around the axis of the fixed parabolic antenna. Antenna Lobe Of Energy Pattern of scanning

29 Determining Tracking Error Using Conical Scan Locus of Beam Centers Beam Time Pulse Return Amplitude Equal Amplitude Sensor Return Signal Antenna Axis Target Position is in the Center of the Conical Scan (On Antenna Axis)

30 Determining Tracking Error Using Conical Scan Locus of Beam Centers Beam Time Pulse Return Amplitude Varying Amplitude Sensor Return Signal Antenna Axis Target Position Off the Center of the Antenna Axis

31 COSRO Conical Scan on Receive Only * Transmits pulses on antenna axis * Measures strength of return around axis of the antenna * Positions antenna based on return Antenna

32 Monopulse Developed to overcome tracking errors involved with conical scanning and sequential lobing Two or more beams transmitted simultaneously and amplitude comparison is made between returns One reflector but uses two or more feed horns Each simultaneous beam can be identified by tagging it with some type of information such as slight polarization Very complex and expensive!!!!

33 Monopulse = Summing of lobe energy

34 Monopulse Tracking AB Return Strength AB AB A – B Comparison

35 Providing a Stable Tracking System All tracking systems require some stabilization Three classes of tracking system stabilization Unstabilized - Not stabilized in any axis Partially Stabilized - Stabilized on one axis Fully Stabilized - Free of all rotational disturbances Gyroscopes provide the stable reference

36 Basic Gyroscopic Principles Gyro spins at a very high velocity –Spin axis remains aligned with terrestrial meridians Inertia –Rigidity - gyro will remain at a fixed orientation in space if no force is applied to it –A gimbaled gyro makes a good reference to cancel out platform role, pitch and yaw (ship or aircraft)

37 Basic Gyroscopic Principles Precession –A gyros spin axis has a tendency to turn at right angles to the direction of the force applied to it –Torque required to move the gyro is converted into a means of controlling system gain The gyro has three axes –spin axis –torque axis –precession axis

38 Gyroscopic Theory Accelerometers!!!

39 Now, put em together!!!! Range Tracking Angle Tracking One dead duck…………………..

40 Automatic Range Tracking Uses range gate method of determining range error. The range gate pulse is centered on the expected range. Actual Return Expected Return Centered on Predicted Range. Summation of actual pulse energy that falls within the boundaries of the expected pulse. (Second half energy amount is inverted so easier to compare). AB Range

41 Tracking Gates Return Strength GATE – small volume of space monitored on each scan

42 Questions?

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