First step done!

"Andras Tantos"


I'm already using a via eden, and it really has a very low power consumption compared with a regular PC. My main problem is the energy to make the motors go on.

In this sense, I'm planning on installing some simple sensors on the shocks to measure activity. It should be possible to "learn" that some types of surface allow for greater speeds without much shock activity (and less vibration to the cameras)

I know that, and I hope to tackle those problems. If you keep the grand challenge in mind, the problem is not only traversing the desert, but be the first one to traverse. So speed is a very important component in the equation. Although I am aware that 50 mph on a hummer is very different from 20 mph on a RC car.

We won't be using stereo, which saves some computing time already. And as stated above, one of the main points of my research is to "find out" where it is possible to speed up. If the rover is on a flat surface, then it may afford to travel one or two meters "blindfolded"... Of course these are only theories in my mind... I may be completely wrong.

As stated above, we won't use stereo. One camera (slightly wide angle) will be fixed looking ahead. The other one will be on a pan-tilt base, together with a range finder (sonar). Think on how we drive. Before making a 90 degrees turn, we turn our head first, and then we turn the wheel. Kind of the same.

I think that will be the biggest challenge... with the increased center of gravity, the car flips very easily. I believe we will have to impose some limits on speed anyway, or else we would have to change the platform too much.

I know, and it will probably get many simplifications along the way. But in order to break through in anything, you have to dream high. You only have to be wise enough to realize when it is time to step back or be persistent when big challenges come in your way.
Cheers
Padu
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

be the

different from

if you keep the past results of the challenge in mind, you could take as long as you want to get to the finish. as long as you got there, you'd win. Everyone got stuck.
Rich
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hi!

My eden board died (on the selve!!) before I could measure its power consumption. OTOH for my purposes I'm afraid that board would have been too slow anyway.

That is actually a very good idea! I might steal it, if you don't have a patent on it :-)!!

That's true. My approach is however to tacke the 'getting there' part first and once I have a reliable solution for that, worry about speed.

Sorry, I don't know where I got that you're working on stereo vision.

Yip, that's an issue. And making a pan-tilt base to work reliably on a moving platform is hard. I don't really have a plan yet for that problem. On idea I've been toying with was to split the image into multiple segments and use mirrors to project multiple views into a single camera: front, left, right, rear. Not simple either and has its own drawnbacks but at least no moving parts.
Regards, Andras
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andras Tantos wrote:

only
is a

50 mph

first
One advantage of a smaller vehicle is you may be able to rig up some sort of re-inversion device to right an overturned vehicle. If you saw the pictures of the 1st Darpa challenge, you'll see big-red upended on the course with it lidar [??] dome crushed in. Prolly takes a crane to turn over a hummer :). =========

And as

out" where

it may

are
Whereas big-red had just about every sensor known to man on their hummer, the following guys indicated that their stereo vision system alone [back in 2004] was almost adequate to run the entire course ... note the last sentence below ...
http://www.digitalautodrive.com /
D.A.D. POSTMORTEM:
http://www.digitalautodrive.com/darpa_grand_challenge.htm
3/16/04 (Following Tuesday after the race): Here is a "final results and post mortem" update for Team DAD at the DARPA Grand Challenge.
What you probably know is that we finished third, making it 6.4 miles, behind the Red Team and Sci Autonics II teams made it just over 7 miles and 6.8 miles respectively. We were paused and then when we tried to restart we got hung up on a rock for 2 hours then were disabled. Here's some more info you might not have heard.
Dave and I redrove the route yesterday morning, largely in autonomous mode. We think we found the rock we hung up on. The GPS tracking looks like it led us right over it, and once they paused us the rock acted like a wheel chock. When we restarted the speed limit was only 5 MPH and we didn't have the smarts to accelerate until we moved. We only gave enough gas to go 5 MPH and that wasn't enough to get over the rock. Once we were disabled, the chase team just tapped the gas and we were over the rock no problem. D'oh!
However, we still wouldn't have gotten out of the hills. There were "switchbacks" and other turns in the road that we weren't programmed to handle - we needed more turning radius at slow speeds and better servoing at high speeds. Not a problem - just a software change - but we weren't ready for it.
All tolled, we were probably only 2 days of programming time away from completing the course.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"dan" wrote in message

My thesis advisor posted an additional challenge (as if making this thing to navigate by itself wasn't a big enough challenge) of making the car to "jump" some small obstacles. Although I'm not planning it for the first phase of the project, we put some thought about this requirement and we have considered the idea of a spring loaded mechanism to unflip the car when it is upside down... but I don't know how effective it would be. Maybe designing my own chassis that doesn't have an up side (any side is up side... symmetrical about the horizontal axis) would be a more robust solution.

<snipped>
These types of information are really usefull for us that are just starting. I'm lurking the DARPA GC newsgroup too, there are lots of good information coming directly from the teams that participated last year or that will participate this year...
Cheers
Padu
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

starting.
information
will
You might take a look at the websites of the teams that did the best in the Darpa challenge, and pay special attention to what they were using for sensors ... Axion, DigitalAutoDrive, Overbot, RedTeam, Sciautonics. Eg, as noted last time, DAD relied mainly on stereo vision, and got almost as far as big-red, who had about $3-4M worth of every sensor know to man, along with something like 5+ multi-Ghz cpus.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Andras Tantos"

(and
Go ahead :-) I't probably public domain already, as I've mentioned it in a public medium. I've been looking for a few linear potentiometers (the ones with retractable strings), but they are too precise and expensive (their specification is in the order of counts per micron). I thought about hacking old mouses and using their encoders... if you use that route, please share your design.

mph
first
I understand, I'm taking that approach too, but keeping the speed goal in mind while I'm designing it.

making
On
and
I won't deny that it is difficult. I first thought about that logitech orbit camera, which has a pan/tilt mechanism (and an excellent image by the way), but it is too fragile. Any bumps generated unecessary vibration in the mechanism. I'll have to design my own pan/tilt mechanism with more robustness and some shock isolation... so far only an idea, I will only know how practical it is when I get my hands dirty.
Cheers
Padu
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Padu wrote:

<snip> Don't you only want to monitor shock absorber activity rather than actual position at any moment in time? Also optical encoders attached to the shock absorbers on a vehicle will be subject to quite a lot of dust (could quickly be obscured)..
Why not attach a magnet to the moving part of the suspension and a hall effect sensor on the body close by? That way you would get an indication of suspension arm activity and speed albeit with no (accurate) position information.
JMTPW.
Jon.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"jon sutton"

That's exactly what I'm looking for. There are 3 factors that are very important here: 1) cost 2) size (I'll need to implement at least 4 of such sensors, the car has 8 shocks, but I think I can measure activity of 2 shocks in one wheel using only one sensor) 3) robustness
From your comments, I realize that an optical encoder may not comply with 3rd one. Can you give me more pointers about some hall effect sensors that would fit this applications?
Appreciated
Padu
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Padu wrote:

In the UK RS components stock a Honeywell device - SS495A (RS Part No. 216-6231 at 1.37 UK Pounds) I believe it is in an e-line package and available in a surface mount package. Operates from 5 to 10Volts and gives an analogue output from 0.2 to supply voltage dependant on magnetic flux strength (closeness of the magnet) They also have ruggedised industrial sensors that have a sealed body with a screw thread on the outside for mounting - these are a around 25 each and would probably be too large for your present vehicle, but might be suitable when you move up to a bigger platform.
http://content.honeywell.com/sensing/prodinfo/solidstate /
Has a lot of info on this type of sensor, as well as a list of worldwide suppliers.
Hope this helps, Jon.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

logitech orbit

way),
the
only know

As you probably know, some of the consumer-market hand-held video camcorders have self-stabilizing mechanisms, so you might investigate what they use. Besides mechanical devices, you can use deblurring software, autocorrelation rectification, etc. Eg, if you have a 1024x1024 camera, and limit the usable image size to 512x512, then you have enuf margin around the edges to compensate for a 256-pixel jitter/shift in any direction between frames. With a 1-Ghz cpu, you prolly have plenty of time to autocorrelate and re-justify the images. The commercial camcorders don't allow for this much jitter-margin, I think, but for your app, you might do it.
Also, JFTHOI, you might take a look at the techniques they use with the vibrating retina devices ...
http://www.klab.caltech.edu/~ania/research /
These are cool and actually modeled after jumping spiders, whose retinae are narrow vertical strips, which they scan back'n'forth horizontally to take 3-D measurements. If you think about it, by limiting sampling to only a 1-D strip and then processing this at successive time increments, the spider brain reduces the level of processing by about the square-root. N(t) instead of N*N(t). Even so, prolly pushing what a spider brain can handle :).
- dan michaels www.oricomtech.com ====================
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Can you describe parts? CD ROM drive? What are you using for video capture and processing?
Rich
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Can you describe parts? CD ROM drive? What are you using for video capture and processing?
Rich
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Padu" wrote in message

rover)
only
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?
Padu
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Padu wrote:

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.
Hope that helps -- m
--
(Replies: cleanse my address of the Mark of the Beast!)

Teleoperate a roving mobile robot from the web:
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"the Artist Formerly Known as Kap'n Salty"

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Padu wrote:

Highly doubtful, but add duct tape and I'm sure you're fine.
Tommy
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Padu wrote:

The pros and cons of different kinds of plastics *is* covered in the book, but here's sneak preview... <g>
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.
-- Gordon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Padu wrote:

unit
Do you have enuf battery power on the bot to operate this board for very long?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

unit
At least in theory, if I didn't screw up my calculations.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.