aem 4321 / ee4231 automatic control systemsseilercontrol/courses/aem4321/section1_intro.pdfa...
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![Page 1: AEM 4321 / EE4231 Automatic Control SystemsSeilerControl/Courses/AEM4321/Section1_Intro.pdfA EROSPACE E NGINEERING AND M ECHANICS 1/31 AEM 4321 / EE4231 Automatic Control Systems Course](https://reader036.vdocuments.us/reader036/viewer/2022071211/60231e429e14ce444978522a/html5/thumbnails/1.jpg)
AEROSPACE ENGINEERING AND MECHANICS
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AEM 4321 / EE4231
Automatic Control Systems
Course Overview
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Outline
• Course Objectives
• Applications of Control
• Examples: Cruise Control and Aircraft Autopilots
– Terminology
– Block Diagrams
• Summary
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AEROSPACE ENGINEERING AND MECHANICS
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Course Objectives
• Develop an understanding of classical control
techniques and the basic properties of feedback.
• Feedback
– Use a sensor to measure the system behavior
– Compare measured behavior with desired behavior
– Take actions based on this comparison
• Feedback enables many advanced technologies.
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AEROSPACE ENGINEERING AND MECHANICS
4/31
Reusable Rockets: Blue Origin and SpaceX
First Landing by Blue
Origin on 11/23/2015
Linkshttp://arstechnica.com/science/2015/11/blue-origin-sticks-rocket-landing-a-major-step-toward-reusable-spaceflight/
https://www.youtube.com/watch?v=9pillaOxGCo
https://www.youtube.com/watch?v=igEWYbnoHc4
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AEROSPACE ENGINEERING AND MECHANICS
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Self-Driving Cars (Google, Uber, and Many Others)
Linkshttp://www.bloomberg.com/news/features/2016-08-18/uber-s-first-self-driving-fleet-arrives-in-pittsburgh-this-month-is06r7on
https://www.google.com/selfdrivingcar/
https://www.youtube.com/watch?v=bDOnn0-4Nq8
Uber’s Volvo XC90
(coming to Pittsburgh, PA)
Google’s Car in
Mountain View, CA
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Uninhabited Aerial Systems (UAVs) / Drones
Linkshttps://www.youtube.com/watch?v=tJB9g_ne23U
https://sentera.com/phoenix-2/
https://www.dji.com/product/phantom-4
https://www.youtube.com/watch?v=JJPSSqMQajA
Sentera Phoenix 2
(Precision Agriculture,
Road/Pipeline Surveillance, etc)
DJI Phantom 4
(Cinematic Photos, Building
Surveillance, etc)
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AEROSPACE ENGINEERING AND MECHANICS
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Athletic Robotics
Linkshttps://www.youtube.com/watch?v=mT3vfSQePcs
https://www.ted.com/talks/raffaello_d_andrea_the_astounding_athletic_power_of_quadcopters?language=en
Bike Riding Robot Raffaello D’Andrea’s Ted Talk
These two examples are for “fun” but similar techniques have many “real”
applications (e.g. Kiva Systems robots for automated warehouses).
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AEROSPACE ENGINEERING AND MECHANICS
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Example: Automotive Cruise Control
Objective: Use the engine throttle to track a desired
speed specified by the driver
User interface Vehicle
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AEROSPACE ENGINEERING AND MECHANICS
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Block Diagrams
Plant
VelocityThrottle
Command
The plant (car) is the system
being controlled.
Systems represented by
blocks with inputs/outputs
– “Hide” the dynamics
– Interconnect blocks for
more complex systems
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AEROSPACE ENGINEERING AND MECHANICS
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Open Loop
• Open Loop: Compute an engine throttle angle
based on the desired velocity.
• Issue: Incomplete knowledge of the car dynamics
– Uncertain mass, e.g. different #’s of passengers
– Varying environment conditions, e.g. hills and wind
– Imprecise models for complex effects, e.g. engine
dynamics and tire forces.
CarController
Slope of Road /
Uncertain Mass
VelocityThrottle
Command
Desired
Velocity
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AEROSPACE ENGINEERING AND MECHANICS
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Closed Loop / Feedback
• Closed Loop: Update the throttle command based
on a measurement of the current vehicle speed.
• Feedback is the basic principle used to control the
system despite our incomplete knowledge.
• The use of feedback involves tradeoffs
– Stability, speed of response, sensor noise rejection
CarControllerVelocity
Throttle
Command
Desired
Velocity Error
Feedback Path
Slope of Road /
Uncertain Mass
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AEROSPACE ENGINEERING AND MECHANICS
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Cruise Control Block Diagram
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
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Reference Command
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
The reference (desired velocity) is the
desired condition for the system.
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Sensor
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
The sensor (wheel speed sensor) is
a device used to measure the
behavior of the plant.
The sensor (wheel speed sensor) is
a device used to measure the
behavior of the plant.
The sensor (wheel speed sensor) is
a device used to measure the
behavior of the plant.
The sensor (wheel speed sensor) is
a device used to measure the
behavior of the plant.
The sensor (wheel speed sensor) is
a device used to measure the
behavior of the plant.
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Embedded Processor
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
The algorithm computations are
are done on an embedded processor.
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Actuator
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
The actuator (throttle motor) is a
device used to control the plant.
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AEROSPACE ENGINEERING AND MECHANICS
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Plant
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
The plant (car) is the system
being controlled.
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AEROSPACE ENGINEERING AND MECHANICS
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Uncertainties / Disturbances
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
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AEROSPACE ENGINEERING AND MECHANICS
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Control Design
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
• Objective: Maintain the desired velocity
• Considerations:
– Transient response (rise time, overshoot)
– Changes in desired velocity
– Driver comfort (control effort)
– Disturbances, model uncertainty, sensor noise
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AEROSPACE ENGINEERING AND MECHANICS
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Control Design
CarController
Measured
Velocity
Throttle
Cmd.
Desired
Velocity Error
Slope of Road /
Uncertain Mass
Actuator Sensor
• Design Process
1. Model the system: Differential equations
2. Design the control algorithm
3. Analyze and simulate: Theory + MATLAB
4. Implement the controller and experiment
5. Iterate
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AEROSPACE ENGINEERING AND MECHANICS
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Proportional-Integral-Derivative (PID) Control
FuturePast
Presenttime (sec)
vd(t)
55
velocity (mph)
65e(t)
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AEROSPACE ENGINEERING AND MECHANICS
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Example: Commercial Fly-by-Wire
Boeing 787-8 Dreamliner
• 210-250 seats
• Length=56.7m, Wingspan=60.0m
• Range < 15200km, Speed< M0.89
• First Composite Airliner
• Honeywell Flight Control Electronics
Boeing 777-200
• 301-440 seats
• Length=63.7m, Wingspan=60.9m
• Range < 9700km, Speed< M0.89
• Boeing’s 1st Fly-by-Wire Aircraft
• Ref: Y.C. Yeh, “Triple-triple
redundant 777 primary flight
computer,” 1996.
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AEROSPACE ENGINEERING AND MECHANICS
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Basic Aircraft Control
Aircraft
(787)
Pitch RateElevator
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AEROSPACE ENGINEERING AND MECHANICS
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Block Diagram: Pitch Rate Control
787Controller
Measured
Pitch Rate
Elevator
Cmd.
Desired
Pitch
Rate Error
Wind Gusts/
Uncertain Aerodynamics
Actuator Sensor
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Reference Command
787Controller
Measured
Pitch Rate
Elevator
Cmd.
Desired
Pitch
Rate Error
Wind Gusts/
Uncertain Aerodynamics
Actuator Sensor
The pilot pulls on the column
to specify a desired pitch rate.
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Sensor
787Controller
Measured
Pitch Rate
Elevator
Cmd.
Desired
Pitch
Rate Error
Wind Gusts/
Uncertain Aerodynamics
Actuator Sensor
A gyroscope is used to measure the
aircraft pitch rate
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AEROSPACE ENGINEERING AND MECHANICS
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Redundant Computers
787Controller
Measured
Pitch Rate
Elevator
Cmd.
Desired
Pitch
Rate Error
Wind Gusts/
Uncertain Aerodynamics
Actuator Sensor
The algorithm computations are
done on multiple redundant
computers for reliability.
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Actuator
787Controller
Measured
Pitch Rate
Elevator
Cmd.
Desired
Pitch
Rate Error
Wind Gusts/
Uncertain Aerodynamics
Actuator Sensor
A hydraulic actuator is used to
move the elevator surface
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AEROSPACE ENGINEERING AND MECHANICS
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Distribution of 777 Primary Actuators [Yeh, 96]
“Real” systems can
have many actuators,
sensors, and computers
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Many Other Applications of Control Systems….
Disk Drives Spacecraft
Power Grid
Biomedical Devices
Wind Turbines
(Power Electronics)
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Summary
• Feedback: Compare measurement with a desired value and use the difference to determine control action
• Why Feedback?– Feedback is not needed if the plant model is exact
– Reasons our knowledge is not exact:
• unknown external disturbances
• inaccuracies in our model of the plant behavior
• Issues:– Performance trade-offs
– Need to consider measurement errors (noise, bias, etc)
– Poorly designed controllers may cause instability