The first two milestones of my project were achieved. I've just built the base (cpu and camera) and adjusted the suspension of my rover to carry all the necessary payload.
For those unfamiliar with my project, the ALR2 (autonomous long range rover) is a rc based mobile robot that is intended to ride over rough terrain autonomously for 10 miles. (with the current configuration we are really shooting for 5 miles, but what the heck, if we get 5 miles, 10 miles is only a matter of energy).
And if you look closely, that red box is a set of drills :-)
In actuality, this picture was taken moments prior to its first (remote controlled) test drive. It carries a consumer digital camera just to take onboard footage so we can determine how easy or difficult will be to create the vision system once the final cameras are in place. Because the suspension was replaced by a more rigid one, if we didn't put some dummy weight on top of the rover, it would bounce too much. Therefore that huge CD-ROM and the drill box are there only to make some weight.
The instruments it will carry are the follow:
1 CMOS camera
1 CCD camera (pan and tilt)
2 GPS units (one at 4Hz and another one weak signal) Bumper switches
1 digital compass
2 sonars (pan and tilt)
3 gyroscopes (pitch-roll-yaw)
1 wheel encoder Assorted telemetry (batteries, temperature) rs485 bus mini-itx cpu with wi-fi (cardbus) and CF, OS will be installed in a 2GB CF
Sensors are listed in order of importance.
My next step will be to assembly the mini-itx cpu, install the OS and mount it into the rover with appropriate shock absortion and protection.
It is a regular RC car with two 14.4VDC motors, steering is ackerman style.
I started with gas, but it is not really practical for this application. RC gas based (or nitro-methane) are adjusted for racing performance, and being a 2 stroke engine, they require fine tuning of carburators, they don't idle very well by nature and they are poor performers in low revs. Besides that, it would be impossible to do demonstrations indoors because of the smoke.
What I'm really hoping for is that we get at least 5 miles of autonomous navigation on rough terrain, enough to prove our point and get the budget for a full size 4x4 vehicle to enter DARPA GC.
My opinion is that if you have tons of cash to invest on very sophisticated sensors, you won't sweat hard enough on efficient vision algorithms, and I think the answer is in vision and intelligence, not on ladars and sonars... want a proof?
If I mount one or two cameras on a hummer and let you teleoperate it through the internet, I bet you can make it go from point A to point B through rough (not extremely rough, mainly dirt roads) terrain. Consider that besides vision you also have GPS coordinates.
Most animals in nature don't have ladars or sonars (well, at least not the ones that have good vision)...
What is the farthest traveled distance in past DARPA competitions?
I don't see why someone doesn't get a truck with automatic trans. (sponsored by ford, GMC) put in in DRIVE, and throw a brick on the gas pedal. Would be a cool commercial.
In the real DARPA Grand Challenge, yes. You must complete the 176 miles (or something similar) in less than 10 hours. I don't think there's anything against solar panels, but I do know that you cannot stop to refuel. By refuel I understand as something we humans pre-position on the way of the rover so it can get from the environment.
I had thought about solar panels, but their limited amperage made me gave up the idea, but I've never thought about stopping for a moment until the batteries are full again... that's a good idea, thanks. Realistically, I don't have any expectations of completing 176 miles in less than 10 hours using an RC car, so stopping for a "recovering breath" may be a good option.
How long would it take to recharge my batteries, assuming I have a maximum of 12x12 inches area for the solar panel and 48 1.2V "sub-C" cells of
3700mAh each? (12 cells in series x 4 = 4 packs of 14.4V, total of 14.8A).
Forget this year, this project started after the deadline for this year's GC had already passed. Given that last year the longest run was of 9 (or 6, don't remember) miles out of 170 and something, I don't expect a winner this year, although looking at some of the top teams' web sites, they look very promissing.
Actually your suggested approach is not too bad. If I recall correctly, one of the teams that was having problems on the qualifying rounds disabled a series of sensors, keeping only vision, gps and a couple of basic others. They got better results with less sensors.
I've ordered one copy of Gordon's Constructing Robot Bases last week, but for some reason, amazon will only ship it on may 18th... this question may have already been answered in the book, but let me ask anyway.
The next step in my ALR2 project is to configure and assembly the cpu unit into the robot. It is a mini-itx VIA Eden mobo. What is your reccomendation for a protection case for this unit? Just remember that it must withstand the impact of an eventual crash and/or flip over.
I was thinking on building my one out of lexan, good choice?
I think lexan would be fine (unless there's a static issue). It's pretty easy to work with and strong, although I believe it does scratch easily
-- if you care. If you're using any PCI slots, make sure the inserted boards are well-braced -- these are not meant to take mechanical shock and vibration.
Are you using a hard drive? If so, I think this would cause me more concern than the motherbard as far as the ability to take shock goes. You might want to see if you can use CF or some other non-mechanical medium instead of an HD.
Not a bit. The good thing about lexan is that I can see what's inside, and if so, on my microcontroller side of the robot I can put some status leds inside the protection case and still be able to see from the outside, even with a few scratches.
Only regular DDR memory card, but it has those lateral locks that I believe are enough (?)
No HD's, the motherboard comes with a CF slot. I'll install everything on a
2GB CF card. I guess it will be more robust this way.
The pros and cons of different kinds of plastics *is* covered in the book, but here's sneak preview...
Lexan (polycarbonate) is a good choice. It has a high melting point and good impact resistance, but it something of a pain to work with. I'd avoid expanded PVC sheet for an outdoor robot, because it has a low melting point. Acrylic generates lots of static, and can shatter on impact.
If you have a good plastics outfit near you, ask them about some of their so-called engineering plastics. One of my favories is UHMW, a high density polyethylene. It's the stuff plastic cutting boards are made of. Surprising, it's not that hard to work with, at least to construct a box shell. I's suggerst construction using brackets and fasteners, and not cement.
I understood about the Darpa GC, but I was wondering if this test-case has to cover those five miles in a specific period of time. That would allow some recharging time, or a slower pace, and allowing the solar cells to contribute at least some of the current to the motors.
The test-case goal is to prove that we could navigate the 176 miles of the GC, therefore, I don't believe stopping to recharge would be a problem. If it proves to be feasible (half an hour instead of half a day), then implementing solar panels would be an additional attractive, not to say that it would be able (in theory) to navigate the 176 miles.
Since the test is mainly for the navigation prewess of your vehicle, would it be allowable to have it simply stop to allow you to replace the battery pack?
Frankly, if you can get this thing to go even a mile in rugged terrain, and end up a meter or two from where it's supposed to, you can hang the Darpa challenge. You'll have something quite marketable right there!
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