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ATAV 602: Auto-flight Systems > Week 4: Servo Systems > Flashcards

Week 4: Servo Systems Flashcards

1
Q

In an aircraft with cable and pulley controls how is the autopilot servo connected to the control cables?

A

With a bridle cable

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2
Q

What basic requirement of a closed-loop system (not present in open loops) enables present load position to be sensed?

A

Feedback

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3
Q

An error signal is the difference between what two quantities fed to the CT (error detector)?

A

Input and feedback

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4
Q

The output of the summing point must contain information that controls what 2 factors of load movement in a position servo?

A

Amount and direction of rotation

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5
Q

In a typical velocity servo block diagram what device is placed in the feedback loop that is not present in the position servo?

A

Tachometer

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6
Q

What are the 2 common methods used in a feedback loop to anticipate control surface movement?

A

Back EMF feedback

Tach Gen feedback

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7
Q

In a servo system using BACK EMF feedback, the servo is driven with what type of signal?

A

Square wave with varying pulse widths

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8
Q

What type of servo is commonly used in Transport Category aircraft?

A

Hydraulic servos

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9
Q

Why are DEMODULATOR circuits used in some servo systems?

A

Convert AC error to DC error

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10
Q

What is the purpose of sensors and gyros?

A

Detect changes in aircraft attitude

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11
Q

What is a servo system?

A

Uses weak control signal to move a large load with great accuracy

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12
Q

Servo systems can be either:

A

electromechanical, electrohydraulic, hydraulic, pneumatic

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13
Q

Control systems are classified as?

A

Closed or open loop

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14
Q

Which control system is used most and why?

A

Closed loop because more accurate, quick, and has automatic feedback

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15
Q

Synchro devices compares what 2 signals?

A

Electrical applied to stator

Mechanical applied to rotor

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16
Q

What is the name given to the electrical output of a CT?

A

Error signal

17
Q

In a DC position servo system, the ______ and ______ of a DC error signal respectively are used to determine the amount and direction the load will be driven

A

amplitude and polarity

18
Q

The oscillation of the load around the desired position will result in what?

A

Hunting/overshooting

19
Q

In a velocity servo loop when it is in null position what is still present and what is happening?

A

Error signal still present and load is moving

20
Q

When would you use a velocity servo loop?

A

When load is required to be driven at constant/variable speed

21
Q

How is the speed governed in a velocity servo loop?

A

Level of error signal present

22
Q

What is time lag?

A

response between input and movement of load

23
Q

How do you decrease time lag?

A

Increase gain of servo amp

24
Q

What may introduce additional time lag?

A

Weight of the load

25
Q

How do we eliminate overshooting?

A

Damping

26
Q

How do we dampen things?

A

Introduce a voltage in opposition to signal voltage

Physical restraint on servo output

27
Q

What does friction clutch damping use and how does it work?

A

Flywheel, when it slips it disconnects

28
Q

This type of damping has 2 types and uses electro-magnetic force

A

Magnetic Clutch damping

29
Q

This type of damping “anticipates” the amount of overshoot and corrects the overshoot by introducing a voltage in the error detector that is proportional to the rate of change of the error signal.

A

Error Rate Damping

30
Q

In Error rate damping, when does max damping occur?

A

Max rate of change of error signal present

31
Q

The output voltage of the tachometer can be used to do what?

A

Anticipate sudden movement changes of the load

32
Q

What is the electromechanical device that can generate an error-voltage?

A

Tach Gen/ Rate Gen

33
Q

What is the purpose of MODULATORS?

A

Change DC error signals to AC error signals

ATAV 602: Auto-flight Systems (10 decks)

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