Robotic Lawnmower

Rackle

I've wanted to build a remoted control lawn mower for a while, and I typically have trouble starting projects due to a lack of money and knowledge. I'm sure I could increase my experience/knowledge by working on smaller projects and kits, but unless I'm really interested in what I'm doing I won't get very far with it. With that I ask for advice on motor purchasing...

I saw these two motors featured in Nuts&Volts by http://www.resunltd4u.com/. They both have gearboxes built in and run on low DC voltages. To me, seems like a good motor to build onto the side of a mower, or any other slow robotic body.

Can anyone share their thoughts on why these would be good or bad purchases for such an application?

MASSIVE GEAR REDUCTION for BIG TORQUE.
New, right angle drive system intended for use in a childs motorized vehicle. A powerful 12VDC motor drives the attached gearbox to provide final drive through a 1.75" diam. splined drive shaft. The 2.7" diam.male mating hub, included. (black piece in photo). This terminates in a 3.9" diam. flange eith notches for bolts. There is also a 0.43"Diam through hole in the center of the hub. Nice for a large platform. See CARDRIVE FP-2 for quantity price.

http://www.resunltd4u.com/productimages/FP_RA3tr.jpg

BOSCH, REVERSIBLE, with 2.4"LONG STEEL SHAFT.
These are brand new, very rugged, right angle drive, gear motors originally intended for an automotive application. They are very substantial, weighing over 2 pounds each! They offer a 0.44" diam. x 2.4"L steel drive shaft located centered between three 0.45" diameter cast aluminum "spider" threaded mounting points. Each offset 120o and on a diameter of 2.75". Overall size: 5"H x 7.5"L x 2.7"W Motor will operates with wrist twisting torque. As little as 3VDC lights it up, nominal is 12VDC. Draws about 4.5 A under load. All metal construction.

http://www.resunltd4u.com/productimages/RA_DRIVEBLKtr.jpg

Thank you.

jdolecki

My well kept secret i will now share with the world. When ever i need a small dc motor with high torque i would go to my local tool repair store and check out their trask or you could even go in and ask.but they always have some cordless drills and what not's they are throwing away. I have the luxury of being able to machine my·own housings but you can make something workwith the stock ones.

All you have to do is ask the worst that could happen is they say no.·

Beau Schwabe

I never thought of asking for "throw-aways". I always wait until the $10 clearence sale and grab a couple that way.
At least I am certain that the motors work if I buy them.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

---

Beau Schwabe - Mask Designer III

National Semiconductor Corporation
Latest Company News
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071

---

bobledoux

I've been working on a robot lawnmower navigation system for over a year. I've discovered that building from scratch involves reinventing the wheel.

If remote control is your goal, why not modify an existing mower system? Id start with one of the mowers with the large driven rear wheels and swivel front wheels. Convert the front wheels to Ackerman steering, controlled by a large servo. This might not give you reverse direction capability, but everything else would be there.

Differential steering may not be an optimal choice when your machine has to go from point "A" to point "B" in a straight path.

Paul Baker

Most mower's engage bar require a significant amount of force to activate, this could be a problem, using a solenoid with enough force would require a very large load to be placed on the batteries reducing how long you could operate the mower for.

Harry Stoner

I've just read in the last week of robotic lawn mowers for sale to the public. They are expensive and apparantly cut the grass rather inefficiently (go in triangle patterns and take 3 times as long as they should). I'm sure you can find links on the web.

Some day I could see myself owning one of these, but I would want to modify it to cut efficiently.

Harry

m_fabio2

I played around with one mower before college, before I understood RF.

I used a older John Deere full size rider mower, the one with the engine in the back, and just a steering column in the front. The good thing was the tractor had a electronic clutch for the mower.

If your going to make a mower remote controlled, at least make a big one. It takes the same amount of effort in terms of steering and s/s (Start/Stop).

I would worry about making a completely roboitc mower, just from the aspect of failure. We've all seen the matrix.

bishop

wow..it had never really occurred to me to use a riding mower. thats weird. it would be a perfect platform.
hmmmm....

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
**************

daniel woolston
Teksystems Inc.
www.danwoolston.com
**************

Rackle

Would an electric drill motor provide enough force to propell a 20/30 pound lawn mower around? 14.4v, 18v, 24v? what would be needed?

Ryan Clarke

Just a side note: did anyone notice that the WAM book uses a robotic lawnmower as an example (page 4)-

[noparse]:)[/noparse]

Ryan

Todd U

This is a subject of great interest to me that I’ve been working on for over a year.
I used the toy car gear boxes in my completed model along with front casters in a
Differential config. The problem here is mechanical differences in these low grade
Units cause unequal rpm regardless of equal PWM signals. Proportional control
Will solve but further complicates. The dual motor differential system with proportional
Control seems to be an approach used by many, novice and professional.
However, unless you are a code wiz and are using expensive gear motors your
mower will never fly straight.

Back to the drawing board. In brief, I am using two gearbox and axle assemblies· (http://www.surpluscenter.com/item.asp?UID=2005051513452716&item=28-1049&catname=powerTrans) one motor (
http://store.partsforscooters.com/motor-e100.html) and two scooter wheel assemblies (http://store.partsforscooters.com/whasr-e200.html) in my new design.

The idea is to use a one input and two-output gearbox and one motor config. With free wheel and brake control Similar to many commercial lawn mowers. Front casters =
http://www.surpluscenter.com/item.asp?UID=2005051513452716&item=1-2430&catname=trailer

Tom Walker

Another way to overcome limitations of differential steering assemblies is to change it to a "car-type" steering assembly with one motor dedicted to drive and the other dedicated to steering. Be advised that this can complicate navigation, however.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Truly Understand the Fundamentals and the Path will be so much easier...

LoopyByteloose

If you could bury a wire in the perimeter of your lawn [noparse][[/noparse]lets say it is AC at 60hz] and have the lawn mower sense the induction, it would greatly simplify setting up a perimeter. Assuming your a good programer -- from there, the lawn motor could just wind its way in a spiral to the center.

Having been a gardner,
if you set up a lawn without tight corners and a bit of careful thought, it is much easier to run the machine in a fixed pattern. Also, all the sprinkler heads have to be low and god forbid that the dog leaves a bone in the yard or a kid drops a baseball [noparse][[/noparse]they seem to love flying through windows or hitting the neighbors- along with sprinkler heads].

Also, there are very good reasons that most lawn mowers are gasoline driven as grass really can vary greatly in texture and difficulty to cut. Much depends on how wet it is and how tall it is. I doubt if anyone has invented a 'cordless' electric lawn mower. If you do want to go electric, just use a Toro lawn mower body and convert it to an AC electric mower [noparse][[/noparse]but then you have the cord to contend with].

If you have a robot, it is also likely that you will not want to bag the clippings as that requires emptying the bag. If you have to empty the bag several times, then you have to stand by while the mover does the work. You may have to stand-by anyway to start, stop, and refuel the gasoline mower.

I guess what I am saying is this isn't the same as a Roomba. Mowing is dangerous and bulky work. It really helps to have an operator present to watch what is going on.

If you want true freedom from mowing, get some sheep. Of course they do leave little slimy patches of 'doo doo'. But, that is just one small trade off. Besides, you can make sweaters and eat the critter whenever it seems too much. I just love lamb chops!

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
G. Herzog in Taiwan

Harry Stoner

The idea about burying a wire is similar to one I had. I envision cones or pylons to define a rectangle, that are placed by the operator. The mower would be able to determine the boundaries by some kind of sensor or communication with the pylons. This would allow the mower to be used anywhere without prior set up.

Black and Decker has made cordless electric lawn mowers for years.

Sheep would work well and are pleasant to look at. They fertilize while they "mow".<g>

Also thought of tethering the mower to a central post and just running it in a spiral fashion.

Harry

Todd U

In my opinion, one should perfect a radio controlled·mower that operates flawlessly
before attempting an autonomous mode.··

LoopyByteloose

Definitely, not all robots are the same.

Having thought about my above posting for a few weeks, I was really surprised by what people imagine simple robotics can safely do. Being a cutting task is quite dangerous for any machine. Being in an outdoor environment is quite dynamic.

Unlike an indoor environ and a simple task, lawn mowing in quite complex. After a heavy rain, the texture of the grass can change quite a bit and become sticky, the waste has to be regularly managed, and there are a lot of real dangers of an un-attended machine. Unexpected obstacles need to be identified and resolved.

All these factors create additional layers of systems to consider and develop if you want an autonomous robot to complete the task. And, safety is paramount.

This is not an outdoor Roomba.

In sum, robots that do cutting and robots that work in the outdoors require good safety features and should know when to shut down and ask for help. Otherwise, you might come home to a disaster and angry people.

I cut lawns for six years and have been amazed at the spontanous destruction one Toro mower in the hands of the unknowing can cause. It can be as dangerous as a chain saw.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
G. Herzog in Taiwan

bobledoux

Navigation is a critical element of mowing. Most robotic mowers employ a random course with limits defined by a buried perimeter wire. This might be improved upon buy burying a wire that represents the course over the lawn. This is the line-following robot method. The mower would then center itself over the wire as it moves. The disadvantage is that the entire path must be laid out and a wire placed under each segment of the course.

A good navigation technique would be very beneficial in another critical task: finding buried land mines. Having read some to the proposed techniques for robotic land locating I am flabergasted. College researchers propose random search patterns to locate mines in a given area. How would you like to be the mine recovery technican when told "We are 99% percent certain, given plus or minus 5%, that we have identified all the mines within the area we have bounded?"

LoopyByteloose

I think the critical element is not navigation, but SAFE CUTTING.

Please consider using a 'weed wacker' like nylon cord to do the cutting. With a steel rotary blade, rocks fly 50 feet and your pet cat may loose a tail! The more traditional 'reel' lawn mover jams up on rocks or deep lawn. Unattended, you just destroy its blades.

Secondly critical is waste management. The cuttings either fill a bag [noparse][[/noparse]which must be emptied somewhere] or the cuttings just lie about, interfer with cutting, and kill the lawn. You might have one machine cut and later another maching 'rake' the lawn.

Also, it would be ideal to have the waste management unit pick up leaves and debris PRIOR to cutting. That might be done a day or two ahead and allow the lawn to stand straight up. There is a lot of seasonal variation in how you cut.

Also, it is best to cut a lawn from several directions. Always cutting in the same pattern will create 'thatch'. This is similar to a 'thatch roof'. The lawn begins to lie on its side and water just runs off it. You get dead patches.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
G. Herzog in Taiwan