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Thread: The task (lawn mower topic)

  1. #21

    Re: The task (lawn mower topic)

    Having the LED be the "brightest thing" seems hard. Can you recognize some blinking pattern instead?
    jwatte, not a bad idea, few years ago I'v played with image filters that only showed difference between two images, blinking pattern
    would work in that setup.

    Sweet idea!

    Tommy

  2. #22

    Re: The task (lawn mower topic)

    With this platform I tested a new GPS and Magnetic senor from Yocto
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    While I was able to get good GPS data, the Magnetic sensor didn't
    give good tilt compensated compass data.

    So I replaced with a Phidget 3/3/3, and now seem to be getting repeatable
    compass values.
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    Tommy
    Last edited by Tommy_T; 08-14-2018 at 11:45 AM.

  3. #23

    Re: The task (lawn mower topic)

    With the compass integrated to the software I'm ready for next try.

    X=distance traveled
    C=compass bearing
    Q=platform Yaw sensor
    Overshoot Value=Increases with speed, using servo motors keeps the value very consistent

    (A) position platform at start location (facing Target)
    (B) Press "S" on keyboard, (X axis is set to Zero)

    Step 1: platform Zero Radius turns(+) while X<3.1ft
    Step 2: C=80deg, Speed(mowing speed) while X<103.1ft - Overshoot Value
    Step 3: Q=-45deg, Speed(turning speed) while X<121.3ft - Overshoot Value
    Step 4: C=280deg, Speed(mowing speed) while X<221.3ft - Overshoot Value
    Step 5: Q=+45deg, Speed(turning speed) while X<227.5ft - Overshoot Value
    Step 6: Localization(webcam, or wireless trip wire device, or beacon)

    repeat steps 154 times.

    Looks like I need to put a little more effort on the mower's discharge shut.
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    It's loading up, leaving lines of clippings on the field.
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    Tommy
    Last edited by Tommy_T; 08-15-2018 at 07:48 AM.

  4. #24

    Re: The task (lawn mower topic)

    Good news on the clippings :-)

    My experience is that compasses are super inaccurate, and only useful as a 1% corrector in a Kalman filter.
    You really want to use a gyroscope IMU for near-term delta angles, and heading derived from GPS path traveled as another corrector input.

  5. #25

    Re: The task (lawn mower topic)

    My experience is that compasses are super inaccurate
    jwatte, I also have not found a reliable way of using these type compasses yet.
    I'm looking at the gyro next.

    The one sensor that seems to give me repeatable results is the X/Q sensors.
    had some fun in the field turning circles, repeated very nice.

    for fun I may try cutting all 2 acres in circles.
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    Tommy
    Last edited by Tommy_T; 08-16-2018 at 11:40 AM.

  6. #26

    Re: The task (lawn mower topic)

    for fun I may try cutting all 2 acres in circles.
    Someone else's field.
    In the middle of the night.
    Leaving no trace.

    "Alien robots did it!"

  7. #27

    Re: The task (lawn mower topic)

    I'v noticed that the webcam I'm using takes a lot of PC
    resources. So I ordered a set of Photoelectric Security Alarm Infrared Detector Sensor

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    should be a fun test.

    Tommy


  8. #28

    Re: The task (lawn mower topic)

    You really want to use a gyroscope IMU for near-term delta angles
    My current gyro is 8yrs old, they have a new technology(MEM) in today's gyro,
    so I have new one coming.

    they say no drift, my current gyro has 7deg per minutes.
    time between localisations is about 1 minutes.
    I seen some stats that list drift of MEM sensors at 10deg per hour, that would work out
    to .1deg in the time between localization .

    Click image for larger version. 

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    Tommy

  9. #29

    Re: The task (lawn mower topic)

    heading derived from GPS path traveled as another corrector input.
    A good test to check the repeatably of the derived GPS Heading, would be to use the Q to turn
    large dia. circle then stop when a preset heading is reached. should stop the same place
    if it repeats.

    Tommy

  10. #30

    Re: The task (lawn mower topic)

    After setting up a test for the new gyro( easy test, just set a zero and wait )
    I was able to test the repeatably of the GPS heading value.

    the red flag is where the platform started each circle.
    the orange cones are the stopping locations of each circle.(I didn't localize the starting direction for each circle)
    where the platform is sitting is it's last circle(ran out of cones).

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    I spent about an hour changing software and turning circles, when
    I got back to the new gyro it was still under 1deg. (sweet,so far)

    Tommy

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