weapons on target. learning objectives know the definitions of the following terms: input, output,...
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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 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
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)
Feedback Control System
CONTROLLER
FEEDBACK ELEMENT
INPUTOUTPUT
History of Feedback Control
• Water clock of the Greeks
• Industrial Revolution– Pressure Regulators– Water Regulators– Temperature Regulators
• Fantail
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)
Thermostat
Temp Wanted
Air Temp
Heater Control
Example of Feedback Control SystemExample of Feedback Control System
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
Advantages of Closed-Loop Feedback System
Increased Accuracy– Ability to reproduce output with varied input
Reduced Sensitivity to Disturbance– Self-correcting minimizes effects of system
changesSmoothing and Filtering
– System induced noise and distortion are reducedIncreased Bandwidth
– Produces satisfactory response to increased range of input changes
Major Types of Feedback Used
Position Feedback– Used when the output is a linear distance or
angular measurement.Rate & Acceleration Feedback
– Feeds back rate of motion or rate of change of motion (acceleration)
– Motion smoothing– Uses a electrical/mechanical device called an
accelerometer
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 insidea windowless protectiveenclosure inside the gunturret.
Time
Old Position
NewPosition
Turret Position with Feedback
Dampening
Old Position
New Position
Questions?
Automatic Tracking Systems
Feedback Control
Part II
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
Automatic Tracking Systems (Related to Feedback)
1. Target Tracking Parameters
2. Line-of-Sight(LOS)
3. Tracking Line
Target Tracking Parameters
· Azimuth
· Elevation
· Range
· Relative Target Velocity- Target’s motion with respect to the platform’s
motion
Tracking Terms
TrackingElement
Line-of-Sight
Tracking Line
Error
•Tracking line = antenna boresight
•Tracking line lags line-of-sight
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
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
Azimuth lobing
A B A B A B
Returns
Uses of Angle-Tracking Servo Systems
Monotrack fire control radars Homing missiles Acoustic homing torpedoes Aviation fire control tracking systems
Methods of tracking
Conical scan Conical scan on receive only (COSRO) Monopulse
Conical Scan
Time
Pulse Return Amplitude
Conical Scan
Time
Pulse Return Amplitude
Time
Pulse Return Amplitude
COSROConical Scan on Receive Only
* Transmits pulses on antenna axis * Measures strength of return around axis of the antenna* Positions antenna based on return
Antenna
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!!!!
Monopulse
=
Summing of lobe energy
Monopulse Tracking
A B
Return Strength
A B
Return Strength
A B
Return Strength
A – B Comparison
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
Now, put ‘em together!!!!
• Range Tracking
• Angle Tracking
One dead duck…………………..One dead duck…………………..
Tracking Gates
Return Strength
GATE – small volume of space monitored on each scan
Questions?