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Old 05-05-2022, 07:08 PM
unfinished unfinished is offline
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Default Small RC and Autonomous Mower

Just throwing some random notes and documenting a build for a small autonomous mower (~24" cut). Intended for a 1 acre mow-able area, cutting continuously and recharging as needed.

Will have 4 channel radio control for manual control.
Will have Computer control using RTK GPS for autonomous control.

Way this RTK (Real Time Kinematic) positioning works is:
The Rover's (mower) GPS receives corrections from a Base Station GPS mounted on my roof, and runs software to compute RTK Fixed solutions. The Base Station is another ZED-F9P attached to a computer, which also receives corrections from DOT-run GPS network. The DOT GPS network is freely provided in my state, you just have to request an account to receive NTRIP data over the internet. A lot of this stuff is technical and I can't explain it either.

Mower platform is just a pair of wheelchair motors and pair of deep cycle batteries in series.

Theres a several autonomous rover or mowing projects on the web. I'm going with ardupilot running on a Beaglebone Blue SBC.
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Old 05-05-2022, 07:11 PM
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Block diagram of components. I don't show any proper fusing yet. And the relays for the mower motors may need a logic board to drive the relays, and not directly from the SBC.
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Old 05-06-2022, 11:15 AM
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GWIZ GWIZ is offline
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In the case of a run away you may want to add perimeter bump switches and an emergency stop switch

Quite a few times I had my GPS go crazy or intentionally off location making me U turn back and forth.
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Old 05-06-2022, 07:51 PM
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Yes, I will definitely have an emergency stop button right from beginning. I will have sensors at some point before it runs unattended, but I'm not sure exactly what I'll be using, some combination of bump sensors, ultrasonic sensors, or perhaps some machine vision. I'm thinking about running the sensors on a different SBC and using that to override the inputs to the primary SBC. Ie. stop the machine if it detects something in the way.

Trying to do this in stages. Like the following:
1) Get platform mobile with RC input
2) Base station and Rover GPS configuration and tuning
3) Get platform mobile using GPS input and path planning software
4) Sensor integration
5) Build the mower deck, testing power demands and consumption
6) A way to dock and charge

I did come across a video where it used odometry (the encoder feedback) to continue motion where it lost the GPS signal. Such as under tree cover. That is a concern I have, and will need to test the reliability of GPS. It all hinges on how well the GPS works.
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Old 05-06-2022, 09:11 PM
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Quote:
Originally Posted by GWIZ View Post
In the case of a run away you may want to add perimeter bump switches and an emergency stop switch

Quite a few times I had my GPS go crazy or intentionally off location making me U turn back and forth.
My cell phone GPS does that all the time (WAZE and Google maps). You're driving down the freeway and it will tell you to make a left turn, NOW! Or you can be driving in the mountains and it will tell you to drive off a cliff. I always thought my ex wife had hacked my phone

In the movie Red October, they spoke about the "crazy Ivan" where the sub suddenly turns left or right to see if anybody is following them. I call that the same thing when the GPS starts wacking out as a crazy Ivan maneuver.
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