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Thread: The task (lawn mower topic)

  1. #11

    Re: The task (lawn mower topic)

    seems like a motor brush problem(spring broken).
    That's unfortunate!
    I am more and more becoming a fan of brushless motors ....
    They're as robust as steppers, but faster and higher power!

  2. Re: The task (lawn mower topic)

    While waiting on parts to repair my motor, got to thinking about plan B.

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    some of these type devices have a 500m range.
    found one on ebay with 250m outdoors range for $60.00
    almost seems like it should be a plan A, but because of costs, it's
    still a plan B.


    Tommy

  3. Re: The task (lawn mower topic)

    got the brushes, but wrong size.
    because the springs failed on the brushes from the motor
    I has able to remove springs from new brushes and put
    them on my old brushes, and get the motor to run.

    I was able to test the record/playback software. while it did
    function as planed, it could not repeat angles to required tolerance.

    the platform has about 6deg of lost motion in the drive train(gears,sprockets,chains)
    so some type of angle feedback is needed.

    Tommy

  4. #14

    Re: The task (lawn mower topic)

    6 degrees is a fair amount! I imagine you already tightened up everything you can?
    If you wiggle it, can you see what the limiting factor is?

  5. Re: The task (lawn mower topic)

    can you see what the limiting factor is?
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    the motor gearbox has 2deg of lost motion in them.
    a few years ago I opened one of these type gearboxes
    and pinned it's internal gears to their shafts and was
    able to reduce it to .5degs, but because chains stritch
    and motor brackets can move with heavy loads I gave
    up on that approach.

    that's when I came up with the below idea.

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    This device gives me .008deg resolution of the angle
    the device is moving(Q axis). it also lets the platform
    make sweet crop circles.

    this device has limitations. (losing contact with the ground, and the math is convoluted)


    Tommy
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    Last edited by Tommy_T; 2 Days Ago at 06:53 AM.

  6. Re: The task (lawn mower topic)

    While waiting on cash flow(payday), I had a very strong LED light sitting around
    so I tested using it as a target, see if my cheap webcam could pick it up from
    1000ft.

    My cellphone camera could pick it up.
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    But, not my webcam.

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    Tommy

  7. #17

    Re: The task (lawn mower topic)

    Oh, that's nice!

    If losing contact is a problem, I bet a Raspberry Pi + camera pointed down can, in a pinch, be turned into a picture-based visual odometer. I've wanted to try that, but never gotten around to it. (I believe that downwards-facing cameras for slow speeds can be more accurate than the general-purpose cars-on-streets visual odometers that have significant drift.)

  8. Re: The task (lawn mower topic)

    I bet a Raspberry Pi + camera pointed down can, in a pinch, be turned into a picture-based visual odometer.
    Jwatte, monocular visual odometry off loaded on a Pi seems like a fun test, but I'm still looking at mechanical methods
    of getting reliable odometry information.

    I'm currently testing a 6" #40 chain sprocket.

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    I get .015" resolution with current setup.

    Tommy

  9. Re: The task (lawn mower topic)

    The next test is finding the maximum distance my webcam can
    reliable pick up an LED TARGET. The corps(corn this year) make
    a sweet target, but they are not always there.



    Tommy

  10. #20

    Re: The task (lawn mower topic)

    Having the LED be the "brightest thing" seems hard. Can you recognize some blinking pattern instead? Of course there will be latency for that, but that might not be so bad.

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