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Ramp Speed — Parallax Forums

Ramp Speed

Bob FrumpetBob Frumpet Posts: 5
edited 2005-06-13 03:17 in Robotics
I have yet to figure out what ramp speed is exactly...

I would be greatly appreciative if somebody could help me out with this...


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Comments

  • KenMKenM Posts: 657
    edited 2005-06-12 22:22
    My undefinedunderstanding is that ramp speed is a term related to part of·a waveform.

    Sometimes there is a need to gradually or slowly turn on a motor.

    It describes the slope of a controlling voltage waveform. See attached pic.

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    Ramp Speed.jpg
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  • Bob FrumpetBob Frumpet Posts: 5
    edited 2005-06-12 22:35
    Thanks, I dont think I had the best question though

    I was wondering how it effects the servo chip, and more specifically the serout command...

    Thanks again
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-06-12 22:44
    Hello,

    ·· Ramping doesn't affect the SEROUT command at all.· SEROUT is simply used to communicate the desired values to the PSC.· A better way to word the Ramping effect would be, instead of going from a complete stop position to full speed, which would cause a sudden jerk, the Ramping value allows the PSC to gradually increase the value from stop to full speed over time.· This time is related to the ramping value.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Bob FrumpetBob Frumpet Posts: 5
    edited 2005-06-12 23:01
    Thank you...

    Another question is, how does the ramp speed effect the waveform of the chip...

    Thanks
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-06-12 23:19
    Bob,

    ·· Technically the Ramp does not affect the waveform (other than pulse width) of the chip.· What it does it changes the pulse width of the signal being sent to the servo in increments over time.· But it is a square wave, and that aspect is not being altered.


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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Bob FrumpetBob Frumpet Posts: 5
    edited 2005-06-13 00:08
    Thanks,

    I know this is probably getting annoying, but what is the speed of the servo...
  • dandreaedandreae Posts: 1,375
    edited 2005-06-13 00:12
    It depends on the type of servo (high speed, high torque, or standard)·that you are using.· The servos that Parallax sells averages around 4 to 5mph.

    Dave



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    Dave Andreae

    Tech Support
    dandreae@parallax.com
    [noparse][[/noparse]url]Http://www.parallax.com[noparse][[/noparse]/url]

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  • Bob FrumpetBob Frumpet Posts: 5
    edited 2005-06-13 00:47
    But the speed of the servo is controlable, right...

    In other words, it has a range of 4-5mph...

    Thanks
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-06-13 01:05
    Bob,

    ·· The pulsewidth that you send the servo on a continuous rotation servo determines the speed it spins up to maximum that it can turn.· This is not an exact science, since servos were not meant to turn continuously.· They have been modified.· That said, yes, you can vary the speed from stopped, to max, and in between.· But the range isn't considered· linear.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Ken GraceyKen Gracey Posts: 7,395
    edited 2005-06-13 03:17
    Bob,

    See page 115-117 of the following document:

    Robotics with the Boe-Bot

    There's a discussion on servo RPM vs. pulse width that will answer all of your questions very clearly.

    Sincerely,

    Ken Gracey
    Parallax, Inc.
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