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I'm wanting to build an autonomous lawn mower

So I live rural and have a large square paddock as lawn. I also hate mowing the lawns, and would much rather be in my shed tinkering etc.

I have a spare Walker ride on mower that I can use for this project, and I had a bit of engineering and computer knowledge (I own an IT company with ten staff), so I figured this shouldn’t be beyond me hopefully!.

I also love to research the hell out of stuff before jumping into it, and would rather spend the money for good stuff. Below is a random collection of my thoughts on it all.

So with that aside, here’s my plan, I’m after everyones input on this as I’m a total newbie.

My mower is a Walker very similar to this - http://www.prinsgroentechniek.nl/home/479-walker-mdd-diesel-frontmaaier.html

The back tray can be removed and replaced with a flat board, so mounting things isn’t an issue.

I’d be using Mission Planner as that is probably the most well sorted.

I’d like to use the new PixHawk 2.1 with HERE+ http://www.proficnc.com/system-kits/121-gps-module.html

I haven’t decided on servos or controller boards yet, but open to suggestions.

Controls

The Walker has a single lever for drive speed on the right hand side. This works by being pushed forward. If it’s right back the mower won’t move, if it’s right forward then the mower will go full speed, and obviously anywhere inbetween.

To turn the Walker has two levers in the middle, as the speed lever above is pushed forward so are these. To turn you pull back on the applicable lever, or to temporarily slow the mower down / reverse you just pull both the levers backwards.

Am I better off to have one actuator controlling the forward and backward speed and another two actuators controlling the steering? or would I be better off to reengineer the Walker to have one actuator on each speed lever that’ll also push forward or back, meaning then if the actuator is at -50% it’s full speed backwards, 0% is stationary, 100% is full speed forwards? I’m guessing that might be the easier option for APMRover to control?

Throttle control is a lever on the left hand side. It’s a diesel engine and you pretty much run the thing at full throttle the whole time. This gives the best cut and speed is varied by the speed lever anyway. I need some way to activate the throttle, however I’m guessing an actuator that could just be switched to full would be easiest.

To activate the blade is a lever to the right as well, this requires a bit of force and throw to activate but I’m sure there’s a actuator out there that’ll do it.

Other inputs

I’d also like it to monitor the water temperature and oil light, I can’t quite tell if the PixHawk 2.1 has inputs that could support this, or whether I’d need to make up some adaptor. I would probably fit new sensors to the mower rather than relying on the factory ones. And obviously if the mower got to hot or oil light came on then it would shut down and alarm me.

Positioning

As above I’d go with the Here+ kit, as I believe this will give me the most accuracy and compatibility. It’s a big open field so no trees or anything to block the signal.

Safety

I’m thinking whilst it’s autonomous I wouldn’t let it run without me watching it (happy to watch, just hate sitting on it). I’d have a kill button, and maybe make some bumpers for the front (one each side) that if nudged far enough trigger a switch or something to immediately kill the mower. However, open to suggestions on this.

Any other thoughts anyone has would be much appreciated? I’m interested what actuators people use, and most wont need to be that strong, but I don’t want anything delicate that’ll break easy. The one to actuate the blade starting though will need to be reasonably powerful.

Many thanks.

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