Robotic Mower

studysession

With the power of our wonderful search tool - I have seen some people talk about robotic lawn mowers.... Has anyone actually done this? I am really interested if you have. I want to make one....

I want to control the blad with an electric motor though. I know that will use up batteries quick, but that is what I want to do..... Use tank treads and a motor on each side for driving. Can do something like the Z-Axis on my mill for rasing and lowering the chassis for cutting height.

If anyone has made one, I would like to hear about it.

Thanks

Franklin

First off, start simple. Is there a big need to dynamically adjust cut height? Why not set it to two or three inches and cut the whole lawn? Plan on running it with a 12v car or deep cycle rv battery, you will need the power.

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- Stephen

Mike Green

If you can find one, I would suggest you start with an existing battery powered mower. The shape of the blade chamber is somewhat important for performance, particularly for mulching or for throwing the clippings into an attached bag. It might be easier to add motors for moving and adjusting the mowing mechanism than starting from scratch. These also have/had suitable batteries for a useful amount of mowing and a high efficiency motor for the blade.

studysession

As for a need to adjust cut height. It is not a must, but would think be neat to do.

As for the electric mowers - we used them when I lived in the UK. Not seen them much here in the US though. Figure once I understand the motor controllers for DC motors and then try stepper motors. Then get an idea of torque required and power.
Then take it from there. I have a CNC mill and a lathe that is not CNC. Once I get the transformer to power them. A lot of what I need for mounting brachets and adaptors I can make. Within the next month or so, I should have my transformers. (Need more funds for purchase).

AIman

If you go to Northern Tool's website there is a robotic lawn mower for sale. Also the Twin Cities Robot Club (TCRG I think) has a guy who is building a robotic lawn mower.

There was a previous post about a robotic lawn mower where I posted data on the mower for sale from Northern Tool.

AIman

Here is the post I just referenced.·

http://www.northerntool.com/webapp/wcs/stores/servlet/CatDsp?No=42&storeId=6970&N=143

Automatically cuts lawn with push of a button

Also has manual mode

Cutting system features 3 battery-powered 150 Watt electric motors with 3 blades

Delivers a 21in. cutting width

Equivalent to a 5.5 HP gas mower

5800 RPM blade speed (twice the speed of a gas mower)

6 mowing height adjustments at front, 2 adjustments at rear

Cuts lawn in criss-cross pattern to eliminate lawn stripes

Triple chamber mulching system eliminates bagging of clippings

Safe, quiet and environmentally friendly

Uses perimeter wire system to define mowing area (requires simple one-time setup)

Sensitive bumpers redirect mower away from trees, rocks and any obstacles

Lift Sensor stops blades immediately when mower is lifted

Child Guard prevents children from operating mower

Perimiter switch prevents operation of mower if switch is off

3 hours average work time

Suitable for lawns up to 10,800 sq. ft.

Cuts approx. 5400 sq. ft. per charge

Plug into included charger after mowing

Knobby wheels work on high grass, slopes and bumps

LCD display panel and audio user interface with intuitive and easy to use menus

Includes 24V battery pack

Approx. 20 hours charging time

Durable polyethylene shell

Mower is 35in.L x 26in.W x 12 1/2in.H

Model RL-850

2-year limited warranty

Billericay-Boy

Hi - the quest for a robot lawn mower continues - see my previous postings.

I am also building one as are seval other members. I think that you have to look at the project in 3 stages, being :-

1) Moving platform - chassis, wheels, motors, bumpers etc
··· This will need to be able to potter around and bump and navigate round contacted obsticles.

2) Safety & Containment
··· This is the difficult part. You need to design and build safety devices to stop the blades in the event the bot is picked up or turned over (mercury switch on main power), stop theft (when power turned on - keypad to enter code), how do you keep the mower on the lawn ? (buried wire fence - using either hall effect or RF down a burried wire) - this is diffucult bit.

3) Fit cutting motor & blades. mount motor vertically in round compression collar which will allow you to alter the height.

I am at stage 2 at the moment, even though i have ideas on 3. i have a bot that will bounce round a room ot lawn with obsticles but it falls of the edge of the lawn. i have looked at the Lego line follower and various buried wire fences, the idea being the bot measures the amplitude of the RF as it nears the wire then as it passes it starts reducing, so it reverses. this seeme to be the sticking point for most lawn mowers and myself and Molle are working on the problem. So if you or anyone can help with the Buried wire Fence problem it would be great.
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studysession

Thanks for the replies -
In theory I figured out how I will do most of this. Now have to do it.

I want to use treads like a tank. Anyone with siggestions on what to use as the treads and wheels to drive them? Trying to keep it as cheap as possible. Thanks

bennettdan

Look at this websight..
www.rctankcombat.com/articles/track-systems/

studysession

Thanks -
That link has some great info. I am going to try the bike chain idea. Going to hardware store to get some supplies. Now need to figure out how I will hook my motors up to it to drive it once this part is finished.

Been doing a lot of searches on google and came up with a lot of ideas. To start I could leave the blade being gas powered then convert it to electric later. Not sure what I will do right off on that part. Thanks again.

Billericay-Boy

The sound of a gas powered blade fills me with dread.

If the system fails the blades must stop. All systems must contribute to the continued rotation of the blade so that if any one fails the blade does as well. the other danger is that using a gas powered cutting system meeens that the blades will be very chunky and therefore the rotational energy that they store will mean that they could continue to rotate after power is cut.

Sorry to sound like a kill joy but i do believe that the first systems should be safety orientated. if it cant be done safely then dont do it.

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studysession

My plan is everything will be electric. I prefer electric for everything. Even my nitro powered RC's have all been converted to brushless electric.

AIman

Personally I would look for an old electric scooter or electric wheelchair or even a small golf cart. Those would be reliable and useable motors for cutting grass. As for height of cut, I would suggest just going along with what has been on gas mowers for years. For staying in the yard I would suggest what a guy at the robot club is doing - use a gps and enter points about every two feet or so as you go around the yard exterior and then write code so it doesn't cross it.

I would also suggest that you consider a simple solid state switch instead of anything liquid. Liquid can get bounced pretty good and in the even something gets turned on its side or rolls... Or just buy a dual axis accelorameter

studysession

AIman - I follow most of what you said -
But what is a solid state vice a liquid state switch?

Thanks -

Billericay-Boy

This site has some interesting tracks to make your own cat.trak. http://www.britishrobotics.com/pictures/BRCandice/BR510415Desc.htm



Let us know what you go with.

Franklin

Take a look here for US (Canada) supplier.
www.solarbotics.com
Look under gears and tracks on the right side.

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- Stephen

Quik_Draw

Why not use an RC servo to actuate a device much like on the·self propelled mowers, in the event of a failure (I no NOTHING about RC...would a loss of power to the servo return it to its null position?). ·That way, the failure would force a shut down of the GAS engine just like the push mower applications have now, where they shut down if you remove your hand, allowing the safety bar to release.

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Quik_Draw

I work in the lawn & garden industry...On riding mowers, there is a safety switch built into the seat that won't allow the unit to run if the seat is not occupied. It is really nothing more than a bare metal contact plate that must be CLOSED to complete the safety circuit. You could put a high output on an actuator like that which, in the event of a loss of power to the electronics, would go low, tripping the safety switch to shut down the GAS engine driven portion of the build...

Just trying to "Think out of the box" and offer some input...Hope it's constructive for you...

Quik

allanlane5

"Liquid Switch" aka "Mercury Switch" referenced above. AKA 'tilt switch'.