Ideas for mobile platform

It's Friday, nobody is really working right? So let's warm up this ng a bit.
I just got the news that my budget for a new mobile platform was approved
(yeeeey), so I need to start worrying about chosing one very soon. The project is to create agile rovers that can accomplish fully autonomous missions on a 20 miles range at speeds up to 20mph. It should be smaller than an ATV but bigger (and more rugged) than an R/C car. It must idle well (in case of gas engine). It must have built in reversal and automatic transmission (in case there is more than one speed forward). Low cost (less than $3000). Finally, it must be able to overcome rough terrain (dirt roads, small rocks, grass, grades, whatever it is possible to do with an ATV).
I already have a few ideas in my mind, please critique mine or suggest novel:
- Custom build gas platform: using a small 4-stroke engine (1 to 9HP). Pros: we can build exactly what we need. Cons: takes too long to build, may have lots of flaws as I'm no mechanical engineer - Small ATV. Pros: it's ready. Cons: Too big and cumbersome to carry around, barely fits the budget of $3000 - This little babe: http://www.theultimategolfcart.com /. Pros: perfect size, looks nice (humnn, shouldn't be a reason for robotics right ;-) ), electric allows us to demonstrate indoors. Cons: too heavy (220 pounds!), I'm not sure a 1000W motor is strong enough for this app.
I'm leaning towards the last one, but any suggestion is welcome.
Cheers
Padu
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The golf cart runs off SLA batteries, that is prolly a good bit of mass there. It is 3 wheeled, and therefore less stable. It is not intended for slopes beyond 20 degrees, on grass.
Building a platform capable of 20 mph is going to cost a lot more than 3K.
How about a youth ATV? like a Raptor 50 from Yamaha? Dimensions L x W x H 60.5" x 32.5" x 36" Seat Height 24.3" Wheelbase 40.6" Ground Clearance 3.0" Fuel Capacity 1.8 Gallons Dry Weight 237 Lbs.
Put an electric motor on there with a clutch for reverse.

bit.
well
(less
roads,
Pros:
around,
size,
electric
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"blueeyedpop" wrote in message

I've been thinking about that golf cart and day by day it seems a weaker option... if they only had a reseller here in San Diego that I could see and test it before I buy...
On the kid's ATV side, I had put some thoughts too. The 50 or 80cc seem perfect, but they don't have reverse, I'm not sure what you mean by putting an electric motor for reverse. The Grizzly 125 is the only I could find with built in reverse. I haven't looked at other offstream brands, so my answer may be there...
Cheers
Padu
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I think I was on Crack perhaps, assuming there would be a chain that you could tsndem a motor to.
Mike

for
3K.
and
putting
with
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wrote:

I think I've mentioned this before in another post, but the rear engined snapper lawn mowers might be a good platform to try. If your project is a "not for profit" venture, you might be able to get a local lawn mower dealer to sponser an old used one for free (maybe for a little "NASCAR" type of advertising for the dealer on it). Otherwise a used one in decent shape might be had in the $500 range in the want ads. I've got one I've had for ~15 years and it is *rugged* and dead simple in operation. It hauls me (210 lbs) in and out of the ditch next to the main road without problems. The belt system that drives the blade would be very simple to use to drive an alternator and/or hydraulic pump to support onboard actuators. Foward-neutral-reverse and go-clutch in-stop is all simple push/pull actuation. Snappers are popular in the south, but not sure about the rest of the country. If you have a dealer near you, go buy and take a test ride around the shop to see how they work.
http://www.snapper.com/rear_engine_riders.html
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Si Ballenger wrote:

[snip]
They are rugged, mostly because they are dead simple. Do they really have automatic transmissions? The ones I've seen have a sliding speed/"gear" control with notches, but they really don't have gears in the motion drive train, they are more continuously variable using a friction disk. I would bet that you could remove the teeth on the notches and use a servo to switch from low to hi ratio. Or just pick a ratio and bolt it down.
--
Pat



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On Sat, 22 Oct 2005 12:55:02 -0400, Pat Farrell

Heavy duty gearhead motors modified to be servos like in the below link from another thread could operate the go-neutral-stop pedel, foward-neutral-reverse lever, and turn the short throw stearing wheel. The MSRP for a new bottom of the line Snapper is ~$1,250 ($1,700 for electric start capability), well with in the $3,000 budget. If care were taken with the modifications, the moble platform could be returned to a lawnmower when the project is completed. Anything much lighter might do cartwheels when it hit a big rock or bump in the road at the higher speeds.
http://www.cpg1.freeserve.co.uk/servos/servos.htm
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Having just finished with a DARPA Grand Challenge entry, I think you're underestimating the size of the job.
See
    http://www.ghostriderrobot.com /
the self-balancing autonomous off-road motorcycle that ran in the DARPA Grand Challenge. That meets all your stated requirements. You just have to be really good at controls.
                John Nagle                 Team Overbot
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John Nagle wrote:

I agree with you, John, but the Grand Challenge was a race, 20 MPH would not cut it, and 20 miles is a lot shorter than 200 km.

I just love this silly motorcycle. It is totally impractical, but as a proof of engineering skill, it is so much more impressive than making a Hummer go down a dirt road.

Doesn't this contradict the autonomous criteria?
--
Pat



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"John Nagle"

No, I'm not underestimating... it's been almost one year I'm working on a small scale (R/C car scale) autonomous thing and it's already hard enough. I went to Primm to watch the GC, and that made me gain an special appreciation for this type of effort. I saw ghost rider in person (it's much smaller than I thought it was) and being a motorcyclist myself, I admire that they could get that thing moving by itself... What I think I could have been misunderstood is that for someone that is mechanically talented, building something like an offroad go-kart with off the shelf components may not be as difficult at first glance. In my case I would take ages to do it, as my handyman skills don't go past weekend around the house projects...
Cheers
Padu
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John Nagle wrote:

I don't know how far that thing got this year, but last year as I recall it went about 10' and fell over. Clearly top-heavy. OTOH, an off-road motorcycle makes a nice light-weight and cheap platform that can go 50 MPH, and get 40 MPG.
Suggestion - add some "training wheels", or an outrigger, etc. Or better yet, turn it into a tricycle, like you see a lot of Harleys made into.
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dan michaels wrote:

It went a lot farther. Cheap didn't seem to be much of a criteria in this event.
For years, the Baja 1000 was won overall by motorcycles. They are nimble, fast, accelerate quickly and

Harley trikes are so the bike doesn't fall over when the rider is too drunk to remember to put out their feet. :-)
Single track vehicles can avoid a lot of obsticals that two or three track vehicles hit and have to absorb.
I assume that the ghostrider folks did it for the challenge. There are lots of challenges in a robotic bike.
--
Pat



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On Mon, Oct 24, 2005 at 06:59:48PM -0400, Pat Farrell wrote:

Actually, it didn't complete in the GCE.

I think they had this on this year's version - retractable "landing gear" that would fold up when the vehicle started into motion and then fold back down when stopped.
-Brian
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Brian Dean wrote:

The problem, of course, is that the gyro effect of the wheels is only effective when the wheels are spinning at a high rate. If you need to slow down for an obstacle, etc, then the top-heavy 2-wheeler falls over. That's why human beings have a leg on each side - to put down to hold the bike from falling over!
I started reading the book Fab by Neil Gershenfeld last nite, and lo and behold found a picture of a guy in India who sells $400 conversion units for motorcycles that converts the rear-end into 2-wheels, like a trike. These use it as a cheap tractor. You can quickly remove the wheels and convert it back into a regular 2-wheeler. I'm surprised the Berkeley guys didn't attempt something like this.
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"dan michaels"

Then they wouldn't be doing anything different than the others...
Padu
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dan michaels wrote:

Ever watch a trials rider? if not go rent On Any Sunday. They can stop, back up and then go foreward again without doing a "touch". A touch is touching the ground with any part of your body.
Humans may have an advantage of balance, but the idea of a robot doing trials speed work on a motorcycle is so cool.
Adding an pair of emergency legs so you could do a dab might be a way to do best of both worlds. Walking robots aren't easy and not clear that they are even desired in general. A motorcycles is going to be fine at speed. Don't know if the added weight and complexity makes sense.
--
Pat



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Pat Farrell wrote:

Check out this video if you are interested in slow speed balance. www.ghostriderrobot.com/videos/superslow.wmv
Pretty impressive to me
--
Pat



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Pat Farrell wrote:

They're active balancing, using subtle body movements, not using the wheel gyro effect.

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Pat Farrell wrote:

There was a movie out recently about the Baja 1000. What hoot. The guys on the bikes were complete maniacs. 100-120 MPH on dirt roads.

The Berkeley team probably should have rounded up a harley driver for a consultant.

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dan michaels wrote:

http://us.imdb.com/title/tt0386423 /
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