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Longitudinal Autopilots
12/11/2015
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Introduction
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Autopilot uses:
For safety reasons
Lowers pilot workload (especially for long flights)
Types
Control or Hold certain flight parameter(s)
Perform navigational tasks
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Introduction
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Introduction
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Longitudinal Autopilots Pitch Hold Altitude Hold Airspeed Hold Mach Hold Climb/Descend rate Hold
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Pitch Attitude Hold Autopilot
9/10/2012
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Pitch Hold Prevents pilot having to constantly control pitch attitude in
turbulent air (e.g. TURB switch in 747-400)
Autopilot mode analysis/design, 2 important questions: Which type of control device do we use?
Elevator
What type of feedback loop structure (sensor)? Vertical gyro
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Pitch Hold Block Diagram
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Pitch Hold Block Diagram
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π»π»ππππππππ β 1
π»π»π π π π πππ π ππ β1
πππ π π π πππ π πππ π + 1
πΎπΎ(π π )πΎπΎππ +πΎπΎπΌπΌπ π
+ πΎπΎπ·π·π π πΎπΎπ·π·π π 2 + πΎπΎπππ π + πΎπΎπΌπΌπ π
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Pitch Hold Block Diagram
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Pitch Hold Example: Cessna 620
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Pitch Hold Example: Cessna 620
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Pitch Hold Example: Cessna 620 Simulink & sisotool Gain
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Pitch Hold Example: Cessna 620 πΎπΎ = 0.5 Short period damping goes from ΞΆ = 0.716 to ΞΆ = 0.464 But it still satisfies the requirements, so no inner loop
(SAS loop) is required.
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Pitch Hold Example: Cessna 620
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Pitch Hold Example: Cessna 620
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Pitch Hold Example: Boeing 747-200
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Pitch Hold Example: Boeing 747-200
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Pitch Hold Example: Boeing 747-200
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Pitch Hold Example: Boeing 747-200 Simulink & sisotool Gain
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Pitch Hold Example: Boeing 747-200
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Pitch Hold Example: Boeing 747-200
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Pitch Hold Example: Boeing 747-200
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Pitch Hold Example: Boeing 747-200
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Pitch Hold Example: Boeing 747-200
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Pitch Hold
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Pitch Hold
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Pitch Hold
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Pitch Hold
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Flight Conditions
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Pitch Hold
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Flight Conditions
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Pitch Hold
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Pitch Hold
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Pitch Hold
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Pitch Hold
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Altitude Hold Autopilot
9/10/2012
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Altitude Hold Prevents pilot having to constantly control altitude during
the flight
Autopilot mode analysis/design, 2 important questions: Which type of control device do we use?
Elevator
What type of feedback loop structure (sensor)? Altimeter
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Altitude Hold
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Airspeed Hold Autopilot
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Airspeed Hold Prevents pilot having to constantly control airspeed
during the flight
Autopilot mode analysis/design, 2 important questions: Which type of control device do we use?
Throttle
What type of feedback loop structure (sensor)? Airspeed Sensor
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Airspeed Hold
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Airspeed Hold
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Airspeed Hold
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Airspeed Hold
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Airspeed Hold
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Flight Path Angle Hold Or Climb/Descent Rate Hold Autopilot
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Flight Path Angle Hold Prevents pilot having to constantly control airspeed
during the flight
Autopilot mode analysis/design, 2 important questions: Which type of control device do we use?
Elevator
What type of feedback loop structure (sensor)? Flight Path Angle??
It is not directly measureable so vertical gyro and angle of attack sensor are used.
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Flight Path Angle Hold
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Flight Path Angle Hold
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Flight Path Angle Hold
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Flight Path Angle Hold
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Summary For each Hold autopilot there are two important
questions: Which type of control device? Which type of feedback? loop structure? sensors?
Keep controller as simple as possible Proportional only (if acceptable) PD, PI, Lead/Lag, etcβ¦
The closed loop system must comply with the airworthiness requirements
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Summary Take into account the inner loop, when constructing the
outer loop. Keep in mind the possible effects on the closed loop
system of: Servo break frequency Flight condition (airspeed, altitude) etc...
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