My lawn mower project

Molle

I need your help with my lawn mower project.

I want to built a lawn mower robot inspired of the robocut, using underground fence system.
The robot will work similar to the robocut, but I will experiment with different sensor functions.
The most important in my project is the safety, I will make experiment with Thermal Array Sensor and PIR and other sensors that can detect humans around the robot and make a full stop until no humans are around. I will also experiment with sensing where the grass is cut or not cut.
The lawn mower must work by the lowest power use as possible.

Before I start up the project I want to buy the right components from the begining, thats where I need your experience.

Can you recommend me some good products for the following:

Microprocessor
BS2? what version?· (I will connect up to 10 pcs sensors.)

Drive Motor
I need two drive motors, I imagine a motor speed controllable between 30 rpm and 60 rpm by use of 10 cm diameter wheels.
The motors should be able to carry a robot weight of max 15 kg.

Motor driver
Maybe the HB-25

Cutter motor
Any idear of what approx. speed this motor should run.
For the blade I will use the Zucchetti Ambrogio Replacement Cutting Blade
http://www.robotshop.ca/home/new-arrivals/zucchetti-ambrogio-replacement-blade.html

Hope you will share your experience to quick start my project and hope this can start a good discussion about lawn mower robots.

Thanks
Molle





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bennettdan

The Bs2 is a nice stamp and I believe it is what the prototype of the robocut uses.

Molle

only one reply for this interesting project?

I hoped that all you experienced people could help me to start this project by recommending me some products.

Anyway thanks for the one reply :-)

Thanks

Molle

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Ken Gracey

Hi Molle -

I use a RoboCut on my lawn, so I can help you with some answers. Robot lawnmowers are among the most entertaining and useful robots you could make. There's no shortage of programming opportunities. You could make it locate the charging station, run only at night, use GPS, etc etc. I'm personally more interested in over-the-snow robots, but if that wasn't a new interest I'd probably also be making a lawnmower.

I'd suggest you start with the BS2. Since the HB-25 is a "set it and forget it" H-bridge you should have plenty of bandwidth left over for your sensors. I think the HB-25 is the right choice for motor control, too. It'll handle larger motors than you'll use in your design (up to 25 A). If I made a RoboCut today I'd use the HB-25.

The cutters are simply Stanley break-away knife blades. They're bolted to a rotating disc and they cut really well. I think Hans Forsberg·chose them due to their light weight,·thin profile and razor-sharp cutting ability.

Hope this helps get you started.

Ken Gracey
Parallax, Inc.

bennettdan

Molle I have an older robotics book that has a buried wire senso project in it that might be up your alley, it uses a HI-FI stereo amplifier to give the buried wire the signal to be picked up but the sensor curcuit. I will draw it out on the computer and send it to you if you want it.

Lightfoot

What kind of grass are you cutting? I have grass that is "very full" in places. It also retains a lot of moisture. It requires my 5 hp gasoline engine to cut it. A robocut mower would overheat halfway down the first row. If your grass is heavy prepare to use a very powerful motor, gearing down will help too.

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Well well, I'm seeing things, three of them.

-Stanley Blystone

bennettdan

I figure with the Knife blades at a high rate of speed and is only cutting about 8" should cut pretty good. Kind of like a real sharp weedeater...

Lightfoot

My mower is a 20 inch cut. My neighbors cordless electric mower was ruined because he attempted to cut some extremely rich grass like mine. The motor overheated and fried. For best results I would use at least a 1.25hp motor and gear it as low as you can. For a blade maybe a mulcher at ACE hardware. If you want to get carried away you can double it up and create a lawn crew like mower (bobcat self propelled dual bladed thing).

A mower of my dreams uses a laser to cut the grass.

- A vaccum generates an upward suction that holds the long grass up for cutting (it also picks up the debris and deposits it in a grass catcher).

- A powerful laser beam (you may need multiple beams) exists at the bottom of the vaccum nozzle for cutting.

A gas mower pollutes and is expensive to maintain! With a laser you do not need to worry about blades wearing out, expensive parts, destruction of the environment , and the headaches of engine maintaince. A high power electric motor (more powerful then a leaf blower so it can suck up the largest of debries) will drive a wind tunnel fan for the vaccum. Fuel cell power will make a good future power source. Sealed lead acid (golf cart) batteries will power everything for the time being.

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Well well, I'm seeing things, three of them.

-Stanley Blystone

Molle

Thanks for the inputs until now :-)

I will use the BS2 and the HB-25 based on your reccomendations.


Thanks bennettdan·for your kind offer, I am very interested to see that and I am sure that it is of general interest here.
My first approch will be to experiment with the use of two metal detectors and a metal wire burried as the burried wire system, I want to keep it as simple as possible, and if it works it will be very easy to exclude areas like flowers, just put a wire below the ground ( no need to connect to anything)

As the platform for the robot I am thinking of using the below mower:
Electric Flexible Steerable Lawnmower 38 E easyMove
http://www.gardena.co.uk/catalog/prodid.cfm?art_nr=4038-20&bigimg=1

I will install drive 2 motors and completely modifi the cutter and cutter motor.

I am having trouples with choosing the motors:
How powerfull should the drive and cutter motors be? how many rpm should the cutter motor be?
Does anyone have some idears?

Yes in Denmark we have very fine grass so it is easy to cut.
I like the idear with the laser but when will that be possible and what are the dangers?

Molle
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Sawmiller

how about this motor ?
http://www.surpluscenter.com/item.asp?UID=2006070916584250&item=10-2313&catname=electric

Molle

looks good, I will look in to it, Thanks
Molle

crgwbr

I'm not recomending the laser cutter, but this companies 'Spyder' series would cut grass easily.

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NerdMaster
For
Life

bennettdan

Molle,
If I was going to build a electric lawn mower I would not convert that one because it will take alot of batteries to keep it going and you would have to convert it to a DC cutting motor and modifiy the steering. I would be just as eay to modify a used pushmower and make it skid steer with the two drive motors..

The metal detectors and quite pricy also the curcuit I have uses a coil of wire wrapped around a plastic thread bob. You can build it for just a few dollars. I draw it up for you tonight and send it to you.

bennettdan

Molle,

Here is the curcuit I found I alo attached the datasheet for the NE567. I have not built this curcuit so good luck.

http://www.x-robotics.com/downloads/pdfs/NE567_SE567_2.pdf

tkeenan

Somebody said...

Here is the curcuit I found I alo attached the datasheet for the NE567. I have not built this curcuit so good luck.

Is this a digital output?· Can be it connected to a stamp input?· This looks like a cool circuit.· What do you use as a signal in the wire?


This is very interesting!

Tim

bennettdan

Yes it is a digital output. Actually it needs a AC signal throught the wire you can build a curcuit or you can use a home stereo Amp and connect about 40 foot of wire one end of the wire on the positive and the other end on the negative then you can tune in a radio station then use the volume to change the signal strength on the wire...

For the L1 in the curcuit use a plastic bobbin then wrap 26 guauge unisulated magnetic wire about 250 turns.

Post Edited (bennettdan) : 7/12/2006 1:24:36 PM GMT

Billericay-Boy

Hi Molle, how have you faired with your mower.

I am doing the same thing and am looking at the burier wire fence issue as well on another sandbox discussion. I am trying to choose between a RF in the wire of just hall effect sensors. what was your final choice and is the mower working yet ?

bennettdan

Billericay-Boy,
I dont think you will have any luck with the hall effect sensors they usually have to be within an inch of the magnet it is sensing if not closer.

tkeenan

Sounds really great thanks very much



Tim

bennettdan said...
Yes it is a digital output. Actually it needs a AC signal throught the wire you can build a curcuit or you can use a home stereo Amp and connect about 40 foot of wire one end of the wire on the positive and the other end on the negative then you can tune in a radio station then use the volume to change the signal strength on the wire...

For the L1 in the curcuit use a plastic bobbin then wrap 26 guauge unisulated magnetic wire about 250 turns.

Molle

Thanks Bennettdan very much for the circuit, I will make it when I will have some time.
Do you recommend any freq for the freq generator that must be used to feed the wire?

Molle
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bennettdan

the frequency has to be one that the tone decoder chip can pick up read the datasheet for it and then tune the curcuit for one..

Post Edited (bennettdan) : 7/21/2006 6:13:41 PM GMT

AIman

· ent to the website of Northern Tool and pulled up a robotic lawn more. Thought you might want the link, the specs are pasted in below. It runs off a wire system like you are talking about wanting to use.

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

ryan1985

Interesting, I also is on a lawn mower project

DJSandberg

Hello,

About 20 years ago I built a chassis for a robotic mower.· I used two automotobile wiper motors geared down 4 to 1 with #25 chain to 8 inch wheels.· It moved at about 3 mph and used differential steering.

For the sensor, I used 12 IR emitter and detector pairs·that were mounted like tynes on a rake.···If a blade of grass broke the beam, the signal was sent to one of 12 ·555 timers that would extend the pulse.·· Don't laugh now, but Basic Stamps weren't around then.· The signals went to an EEPROM, and then to the motor controllers.· No MCU.

If it saw 000001111111 it would go·right until is saw 000111111111.

The idea was just like the way·a human mows grass.· You look for the part you've already cut and overlap the cut area by about 25%.· ·It worked surprisingly well in my small yard in Los·Angeles.· I had a sidewalk that went·around the circumference of·the yard, so I didn't have to cut the first swath manually.

My plan was to use 3 automobile cooling fan motors to actually·cut grass.·

I never finished it.· I had several hundred bucks into it and saw that it was going to take several hundred more.· One Saturday morning·(in Los Angeles)·when I was working on it, the gardeners showed up in their white van.· Six guys jumped out and started mowing, trimming, edging, blowing, pulling weeds and whatever else they did for forty bucks a month.· Yep, $40 a month.· I just couldn't justify the expense and the work.

Daryl

Dgswaner

There are no new Ideas I swear! I was going to use the same approach. I was sure that mounting the IR Sensors like that was my original idea but I thought of it about 10 years ago! darn. I was going to have my mower start in edge following mode and do all of the edges, then go the opposite direction. to find the edge of the center (outer edge of the center) and follow the edge inward until the distance traveling is < 3' then drive in a back and forth 5' square pattern covering the last little bit. cost is always a factor and kept me from building it 10 years ago. Now my lawn care is part of my HOA agreement so I don't feel it is a good place to dump a large sum of money when the lawn care is already being done! perhaps the next house!

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DGSwaner

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"When in doubt, use C4" - Jamie Hyneman, Myth Buster