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position control

Discussion in 'Electronic Design' started by [email protected], Aug 31, 2006.

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  1. Guest

    hi
    i am searching about the factors that affect the accuracy of position
    control of ac and dc motors , also the difference between them in
    position contro ( ac & dc )
     
  2. default

    default Guest

    Google for servo motors or shaft encoders - servo motors may have
    position feedback and or speed feedback. Shaft encoded motors -
    sounds like what you want . . . have absolute position feedback/

    Absolute position means just that - some digitally encoded signal
    tells you the position of the motor shaft at any angle within some
    specified resolution.

    Stepper motors usually require a "home" position to initialize them on
    power up - go to a position, close a switch (interrupt a beam of light
    etc), then it knows where it starts from and can count to a position
    (easily the most common type of position encoding used today) If
    something physically interferes with their position they merrily go on
    not knowing where they are.

    And - do you really want to know the position of the motor or what the
    motor is driving? Do you need uninterrupted 360 rotation of the
    driven device?

    AC servos are practically extinct unless you are talking very large
    industrial motors with feedback on the driven mechanism (or consider a
    stepper motor an AC motor) Back in WWII they used them Look up
    synchros, selsyns, and servos.
     
  3. Hewants us to answer his homework for him.

    Good Luck!
    Rich
     
  4. Guest

    I have been graduated from faculty of engineering
    i want to know difference between position control of ac $ dc motors to
    decide which is better.
    my motor is suppoosed to be used in a machine for examining diffrent
    luminares by measuring luminous intensity
    if you can help plz help
    thank you
     
  5. What sort of power / torque / speed? Sounds more like a stepper motor
    function.
     
  6. Jim Thompson

    Jim Thompson Guest

    "I have been graduated from faculty of engineering"

    Scary ;-)

    ...Jim Thompson
     
  7. so who will design the new stuff?


    martin
     
  8. Jim Thompson

    Jim Thompson Guest

    I don't know. I'm considering retiring to a life of debauchery ;-)

    ...Jim Thompson
     
  9. You'd prefer he write in his native language (Arabic, I'd guess)?

    Try googling on "AC servomotor" and "DC servomotor".


    Best regards,
    Spehro Pefhany
     
  10. default

    default Guest

    It would help if you expressed your application a little better

    ". . .examining different luminares" (light source or
    reflector/diffuser, or combination etc.?) By measuring luminous
    intensity. Where does a motor come in to this? Mechanically chop the
    light source(s), direct the light from two sources into a photometer?
    Physically move the sources or detector?

    The application will tell more about what to use than really general
    questions about servos. There's different conditions to consider - do
    you care about speed? How many different positions? How fast and how
    many degrees of accuracy do you need? Good chance the mechanical
    design will also come into this.

    If you've been "graduated from faculty of engineering," was that
    electrical engineering? In what country? They don't cover this?
     
  11. Don Foreman

    Don Foreman Guest

    Highly recommended!
     
  12. Since so many US employees have been replaced by shaved monkeys (customer
    support, retail sales) why not continue the trend?
     
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