Neets Module 15 Assignment 2

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CVN68
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165466
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Neets Module 15 Assignment 2
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2012-08-09 16:35:43
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Neets
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  1. What is a servo?
    A system in which the precise movement of a large load is controlled by a relatively weak control signal.
  2. In an open-loop control system, what action reduces the input to zero so the load is stopped at the desired position?
    Usually the operator senses the desired load movement and reduces the input to stop the motor.
  3. What basic requirement of a closed-loop system (not present in open-loops) enables present load position to be sensed?
    Feedback.
  4. An error signal is the difference between what two quantities fed to the CT (error detector)?
    Input signal and feedback.
  5. What are the three relatively common classifications of servo systems by function?
    Classifications in accordance with position, velocity, and acceleration functions.
  6. The output of the sum point must contain information that controls what two factors of load movement in a position servo?
    Amount and direction of rotation.
  7. What term is used for a series of overshoots in a servo system?
    Hunting.
  8. What are two major differences between velocity servos and position servos?
    Velocity loop senses velocity rather than position. When velocity loop is nulled, an error signal is still present and the load continues to move.
  9. In a typical velocity servo block diagram what device is placed in the feedback loop that is not present in the position servo?
    Tachometer.
  10. What is the advantage of using a closed-servo loop to control load velocity?
    The closed-servo loop can regulate load speed under changing conditions.
  11. If a position servo system tends to oscillate whenever a new position is selected, is the system overdamped or underdamped?
    Underdamped.
  12. If a position servo system does not respond to small changes of the input, is the system overdamped or underdamped?
    Overdamped.
  13. Why is damping needed in a practical servo system?
    To minimize overshoot and/or oscillations.
  14. Error-rate damping is effective because the circuitry has the capability of ______________the amount of overshoot before it happens.
    Anticipating.
  15. In a properly designed servo system that has an oscillating input (order), what should be the response of the load?
    It should oscillate.
  16. What is the advantage of designing a limited bandwidth into a servo amplifier?
    Unwanted noise-generated frequencies are rejected.
  17. When the input and output wipers of a balanced potentiometer are in the same angular position, what is the value of the error voltage?
    Zero.
  18. In the output of an ac error detector, what indicates the (a) direction and (b) amount of control necessary for correspondence?
    • (a) Phase
    • (b) Amplitude.
  19. What two basic types of magnetic devices are used as error detectors?
    E-transformer and control transformers.
  20. What is the basic difference between the primaries of ac and dc rate generators?
    The method of primary excitation (ac and permanent magnet).
  21. What is the purpose of a modulator in a servo system?
    To convert a dc error signal into an ac error signal.
  22. What is the purpose of a demodulator in a servo system?
    To convert an ac error signal into a dc error signal.
  23. What is the purpose of a synchronizing network in a servo system?
    To switch control of the amplifier between either the coarse signal and the fine error signal.
  24. What the three basic components make up the typical magnetic amplifier?
    Two saturable reactors and a transformer.

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