Autonomous Electric Lawn Mower

[hayden55]

Originally Posted by redpoint5

The existing robots all use blades that are relatively safe if they hit a person or animal. Maybe it would cause a laceration, but not bad. I've seen videos of the robots going over plastic toys, and they leave the toys intact.
Will this robot mow a pattern, or random?

So the mowing a random pattern concept has been driven into the ground. The plans are even already available on maker space for one of those three-wheeled electric fence bouncing robots already.
We are going to be mowing a pattern. Accuracy of the sensors is up to 10 mm. But we will see. Setup and implementation heavily effected the accuracy from 10mm up to 1 meter accuracy.
Also, my goal is to be able to mow any pattern we input, not just the users personal yard (which I think is lame on top of the random pattern and very limited mowing/cut).
Lastly, I'm sure our robot will be as dangerous as a standard gas mower. Except when a gas mower hits a big branch and stalls, ours gets more torque strength as the mower approaches zero rpm! So keep the small chillens away. :P
Nah I'm sure we can monitor input amperage vs rpm and see what we are mowing and if it is outside of acceptable range we can stop the blade. (think smart power tools)
For the most part we are only going to the final concept stage of development and will not be selling this so we don't have to worry about sue happy snowflakes! (see: tesla door handles)

I will for sure be building me one for personal use afterward though as I will finally be an engineer. Also, it will probably be converted to gasoline and possibly even add an alternator. A pure gasoline input automower would be heavenly and cheaper. *woot cash money* *woot no more poverty*

[freebeard]

For the most part we are only going to the final concept stage of development and will not be selling this so we don't have to worry about sue happy snowflakes!

If it's still in the conceptual stage, could you swap out the [rotary?] blades for reels? They are much friendlier to the grass, shearing instead of battering. Less moisture loss.

[redpoint5]

I'd prefer a dangerous mower. They aren't meant to be safe, and if they are safe, they aren't so effective. The videos of consumer robots shows them mowing an already mowed lawn, which isn't impressive. I want to see it take a couple inches off and hack down weeds. I'd still put a big red EMO button on it though.

[litesong]

Originally Posted by hayden55

...System voltage is 24V.

Might some of the bicycle motors work with 24V? Bicycle motors are sometimes, 36V & 48V, but could be some are 24V?

[hayden55]

Originally Posted by litesong

Might some of the bicycle motors work with 24V? Bicycle motors are sometimes, 36V & 48V, but could be some are 24V?

I started to go that way at first, but I noticed the continuous heat capacity on them was only like 200W-250W (btu/hr). Ended up being too small. The bigger versions were closer. But these guys came through faster than that whole idea.

Blade: Standard 20" lawnmower blade from wal-mart. I think those razer blade wheels and all that nonsense are so cringe.

[litesong]

Originally Posted by hayden55

I started to go that way at first, but I noticed the continuous heat capacity on them was only like 200W-250W (btu/hr).

Yes, most of the bicycle motors are too small. Cities try to limit bicycle motor sizes to avoid HP wars & bicycles moving at 30-50+MPH. I had a Crystallite(?) 48Volt, 2000Watt motor on a big-tired used Schwinn that powered up, even steep hills.... except for one. The Crystallite came in three torque & speed levels. An old style, I think it could have been more efficient. But it would have powered through most grass easily.
There are other (more efficient?) electric bicycles with strong motors. Got to be a 24Volt bicycle motor, you can use.

[hayden55]

Alright final-ish lawn mower specs:

Synopsis of the report: The design consists of an autonomous lawnmower with a 1500W three-phase ac cutting motor (20" blade), a single VFD controller, 4500w inverter, four-wheel-drive system with (4) 100W DC drive motors (7 height adjustable... not easily adjustable yet... ), a modular 3d designed chassis, and a 24V battery solution. For the sensor array, the robot deploys multiple Ultrasonic sensors for obstacle detection and avoidance, a multi-axis accelerometer/magnetometer for directional control (0.1-degree accuracy) and event detection (object strikes, anti-rollover), and a weather sensor for inclement weather detection. The robot also houses an internal GPS unit with a connection to the on-premises GPS base station for correction data to achieve the 10 mm placement accuracy since the closest public GPS station is out of range at 75 miles away. Finally, for the code, the if-then statement lines will control safety, object interaction, traction control, and GPS/Compass data-logging and comparison for route-following.

With that said, that's the plan. We had to resubmit our sensor order so I hope it gets approved again. Also, design contingent on how ambitious I still feel after next semester between the race-car and every other project going on personal and academic.

I think retail for the parts is about $5000 dollars so far. No labor cost included. GPS/magnetometer components around $800.

Now I'm looking into getting into testing and adding the project-specific sensor output values to my previous navigation code from the maze solving robot I worked on this semester. That consisted of around seven pages of code for the obstacle combinations, x tracking, y tracking, pointing direction tracking, three sensor inputs, and left and right motor forward and reverse. :O

[hayden55]

Hopefully, there is a picture attached to this.

Lastly, to add. The next big problem to face will be a lightweight adequate and affordable battery solution. We have to pay out of pocket for it and this thing needs to be similar in weight to an existing push mower! (75 pounds?)

[Daox]

I would highly recommend looking here for lithium battery solutions:

Battery Hookup

You'll likely have to make your own ~24V pack out of the cells, but the prices are great.

[Should be biking]

I know I’m digging up a pretty old thread. But very curious about this. For 10 years I thought about a robo-mower every weekend when I was mowing the lawn. How did this turn out??