Project Nibbles A Scratch built robotic lawn mower

While I've been waiting for parts to arrive for my Robonova I decided to start building a robomower. I'm quite inexperienced with programming of robots but building machines is something I have been doing forever. Ive been looking around and the Arduino platform seems to be the way to go to keep the budget down and also popular enough to find plenty of on-line support when i need it. Im happy to trade beer with any man that helps solve the issues im sure to come across. :o

So as inexperienced as i am i have put together a bit of a plan for the mower and ordered most of the gear to get it going, providing i can teach myself how to program it that is.

After doing a bit of research on whats currently available and what will suit my yard i have decided to make quite a simple robot for a start and then develop as i get a bit more skilled with the programming. 4X4 platform constructed from 10mm PVC sheeting 5inch wheels from RC car basic bump avoidance using 4 corner bump sensors (my yard has walls all the way round) 12v gel cell geared cutter motor with plastic cutting disc Stanley knife blades for blades. eventually a solar pannel to charge it for a few days Some way of using either a voltage sensor or a timer to tell it when its charged up and ready to start mowing again and low voltage cut out.

here is what i got so far. Another two weeks till i get home from work so all on hold at the moment.

Looks interesting; I like the spikes! How do you plan on keeping dirt/dust/etc from getting to the motors/gears/electronics? I’ll probably follow your progress; I recently picked up a Friendly Robotics RL500 for $50.00 off of a guy on Craigslist, with the intent of (someday, maybe before summer if I get really lucky) changing out the controller for an Arduino-based one…

Can’t wait to see how yours progresses!

:slight_smile:

Well That was a bargain. That would save me some trouble.

The whole thing actually needs to be water proof as it is intended to permanently live in the back yard. There will of course be a lid of some sort with the solar panel mounted on top. As for the cutter motor O-ring seals around the output shaft and similar for the drive motors. The way i have mounted them there is only a 6mm shaft sticking out. All the seams of the chassis (box) are sealed with silicone. As for the bump sensors they are hidden behind the hinged bumpers. there just waterproof buttons about 15mm diameter.

Still a long way to go yet all the parts should be there when i get home from work.

I had planned to control the motors with a pololu motor controller but i dont think it actually necessary as the drive motors run at about the right speed directly of the battery. So i think the simpler and cheaper way to go is get a bunch of relays and run them straight off the arduino board. Open to suggestions

Well That was a bargain. That would save me some trouble.

To a certain extent - I likely need to buy a new battery set, which isn't going to be cheap (the old ones - which are SLA - haven't been charged in over 6 months, which means they are likely toast).

The whole thing actually needs to be water proof as it is intended to permanently live in the back yard. There will of course be a lid of some sort with the solar panel mounted on top. As for the cutter motor O-ring seals around the output shaft and similar for the drive motors. The way i have mounted them there is only a 6mm shaft sticking out. All the seams of the chassis (box) are sealed with silicone.

Sounds like a good deal; if my backyard wasn't completely covered by a huge mesquite tree, I would look into a solar charging system for my lawnbot as well. Likely it will have to be plugged in after use...

I had planned to control the motors with a pololu motor controller but i dont think it actually necessary as the drive motors run at about the right speed directly of the battery. So i think the simpler and cheaper way to go is get a bunch of relays and run them straight off the arduino board.

If it works for you, its likely to be the cheapest option - also easy to fix if something happens (use Bosch style automotive relays, and its a simple trip to Autozone/Checker).

Have any ideas on how you plan to check for cut vs. non-cut grass? What about route planning/control? Will it be a "random-walk" style control system, or mapped? These are all questions I need to consider when I get around to mine (mainly on the control-end of things, as the RL500 was a "random walk" mower with a perimeter wire).

BTW - something to keep in mind (although you already have the bump sensors) - monitor current level draw of the motors driving everything; that way if there were an obstruction (even to the blades), you could reverse the motor to "clear" the obstruction (the newer 500+ series Roomba has something like this to keep it from tangling on cords - the original Roomba would just tangle and beep).

:)

While I've been waiting for parts to arrive for my Robonova I decided to start building a robomower.

I've seen a number of robomower projects posted on the net. Bottom line, if you expect it to actually cut grass, start out with a real lawnmower and work from there. If you don't hack the mower too much, then after the project reaches EOL, you still have a lawnmower to use/sell. You could get an electric push mower to use in your project. Remove the wheels, the push handle, and mount the mower in the center of your bot frame. I have some simple wifi wireless bot control ideas in the below link that require a minimum of equipment hacking. I bit the bullitt last night and picked up a kid's riding toy at walmart last night for $50 to experiment with as a wifi bot (my niece has four little kids that will probably get it in the end). Too many toys!

http://www.lynxmotion.net/viewtopic.php?f=20&t=6343

I bit the bullitt last night and picked up a kid's riding toy at walmart last night for $50 to experiment with as a wifi bot (my niece has four little kids that will probably get it in the end). Too many toys!

What did you end up getting? I'm using a PowerWheels Hummer H2 (it was originally bought on Craigslist):

I haven't done much work on it since I've been "fighting" the last of a cold I had a couple of weeks ago; hopefully this weekend I can work on getting the steering working again (thorn in my side)...

BTW - thanks for the link over on the Lynxmotion forum to the network video server. I currently have a Logitech Orbit AF that I was going to use for machine vision and ranging experiment work with the system, but that video server looks very tempting (and I just got paid!)...

;)

Have any ideas on how you plan to check for cut vs. non-cut grass? What about route planning/control? Will it be a "random-walk" style control system, or mapped? These are all questions I need to consider when I get around to mine (mainly on the control-end of things, as the RL500 was a "random walk" mower with a perimeter wire).

Well initially with my skill set, random bump is all ive got planned. I have been thinking about using some sort of compass sensor to make the bot drive back and forth in the same direction with a bit of a random turn at each end. but to be honest that is way over my head right now.

BTW - something to keep in mind (although you already have the bump sensors) - monitor current level draw of the motors driving everything; that way if there were an obstruction (even to the blades), you could reverse the motor to "clear" the obstruction (the newer 500+ series Roomba has something like this to keep it from tangling on cords - the original Roomba would just tangle and beep).

Actually yes this is one of the more important things i have been thinking of doing. Ive decided for a start i would just use a couple of slow blow fuses, but later i would like to upgrade to a amp sensor.

Also i would like to put in a safety circuit with an accelerometer so if the robot is tipped over or something the motors will shut down and then sound a siren from a old car alarm i have lying around.

I've seen a number of robomower projects posted on the net. Bottom line, if you expect it to actually cut grass, start out with a real lawnmower and work from there.

I hear ya, but just wait and see. I've done a little research and a few test with various devices in the back yard, i wouldn't say im 100% confident with the design but i think it'll be sweet. My programming is the bit that sucks right now.

What did you end up getting? I'm using a PowerWheels Hummer H2 (it was originally bought on Craigslist)

Below is the 6v riding toy I got at walmart (big enough to hang some stuff on). Bottom is the router I use in my routerbot project. Simple steering control is the next challange. The only objective is to see how simply and cheaply one can make a remotely controlled bot.

http://www.walmart.com/ip/Disney-Handy-Manny-Mini-Quad-6-Volt-Battery-Powered-Ride-on/14956303 http://www.geeks.com/details.asp?invtid=WGR614NAR

Im doing a similar project using an existing Flymo Lite with a welded frame(so the mower is removable) powered by a wheelchair motor. It will be controlled via RC with a Cam mounter on a pan tilt for those cold days :) Im just working on a method of keeping the power cord up and out of the way of the mower.

cordless mowers

http://www.google.com/search?q=electric%20lawn%20mower%20cordless&hl=en&num=100&lr=&ft=i&cr=&safe=images&um=1&ie=UTF-8&tbo=u&tbs=shop:1&source=og&sa=N&tab=wf