Autonomous Electric Lawn Mower

[hayden55]

Hi guys,

We are running into issues trying to source an appropriate motor for our cutting blade for our lawn mower. I was wondering if you guys had any options to suggest. System voltage is 24V. We are looking for a motor that satisfies the following requirements:

Voltage
DC: Any
AC: ~120V to ~240V (60Hz)
Wattage: ~1500W+
RPM: ~2600RPM+
Torque: Variable
Power requirement Equation:
P (Watts) = (Torque(N*m)*RPM)/9.548

We would prefer DC motors that meet the requirement but could work with the AC motor options.

Seems like our current options have been mostly 360V and 400V in very odd frequencies which require vfd's. Makes the whole setup way to complicate and expensive for a lawn mower.

[Daox]

I would look at motenergy motors. I use one of theirs for my battery riding mower. It's a permanent magnet dc brushed motor and works awesome. The permanent magnet motor self regulates it's speed based off the voltage so you really don't need to get fancy with controls. Mine just uses a forklift contactor. Their ME0909 is nice and small and would easily do the job of spinning a blade.

[hayden55]

Originally Posted by Daox

I would look at motenergy motors. I use one of theirs for my battery riding mower. It's a permanent magnet dc brushed motor and works awesome. The permanent magnet motor self regulates it's speed based off the voltage so you really don't need to get fancy with controls. Mine just uses a forklift contactor. Their ME0909 is nice and small and would easily do the job of spinning a blade.

I like it. What voltage are you using on yours? What blade width? How many kW (or amps whatever works for ya)?

Currently we have a crazy expensive setup with a 205vac 1.35kW (4.15n*m 3450 rpm) motor, an allen bradley vfd, and a big inverter on our grocery list. All together I assume our current robot cost will be around $4500 with all the gps, sensors, 5 electric motors, etc...
Puts into perspective if I ever make another one for private use I will for sure just use a gasoline cutting motor. Much cheaper.

[Daox]

My mower runs on 48V. It takes very little power to push it around, probably 10-20 amps max. Engage the blades and you're sucking an additional 80. Start cutting and that jumps up to about 130 in thick grass. It has a 3 blade 36" deck.

Tim Fulton's Simplicity Broadmoor 728

[redpoint5]

My interest is in the autonomous strategy. Picking a motor to spin a blade should be cake compared to operating in a complex environment.

[freebeard]

First word in the title, then it goes into the weeds.

Start with a drone mower?
https://www.youtube.com/results?sear...trol+mower+diy

[vskid3]

Why not start with a commercially available electric push mower? Many of the battery ones (at least the newer ones) spin the blade slowly to save power until a load is sensed. Then you can focus on the autonomous parts like redpoint said.

[hayden55]

I guess to add back to this post we ended up finding a solution pretty easily. We will end up using a single phase input to three phase output VFD for our 1.5kW Ac motor.

Why not use an existing unit? Donations for the most part. All of our parts have been without cost so far. And actually some of the reverse engineering was a little more complicated than just making your own simplified system. Seems like some of the oem options were made purposely more complex for people to work on for what i assume to be intellectual property protection.

We have a fantastic strategy so far. Can't share too many specifics but we will have multiple GPS inputs, collision avoidance sensors, and collision detection, and probably bumpers. lol

Full tilt we are looking at 2000W/h for the entire robot.

[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.

Sounds like a fun project. It's something I've thought about back before they made consumer products. My current musing is how to make an asphalt shingle laying robot. I'd have the material on a spool though instead of "squares".

Will this robot mow a pattern, or random?

[freebeard]

Can't share too many specifics but we will have.... lol

This sounds much more interesting than the original post. I'm glad I'm subscribed.