Moving to a point between lights with autonomous

[minfranco]

I was just wondering if anyone has discovered a way to get the robot to a column between lights while in autonomous. A pointer in the right direction would be very helpful!

[half geek]

A very simple method would be to find two lights based on virtual windowing or otherwise, then drive to the center.
How to get there and position yourself accurately is a bigger problem.

[kaszeta]

Originally Posted by minfranco

I was just wondering if anyone has discovered a way to get the robot to a column between lights while in autonomous. A pointer in the right direction would be very helpful!

We have a good technique. It also doesn't use a camera.

[minfranco]

well how exactly would u do that without the light?

[lkdjm]

Is there anyone willing to point us in the right direction? We are already using the virtual window splitting, but the camera shakes violently between the 2 lights, and only inches up. It is not nearly fast enough. Has anyone been able to resolve this, or solve this conundrum in any other creative way? We would love to chat about this. ( dmazza90@gmail.com, infranco@gmail.com, gk2400 (aim) coolsn06 (aim)). You could post it on our forum too!! :: http://longwoodrobotics.org/ :: :-) Thanks a million in advance. We know we can always count on the Chief Delphi community.

[kaszeta]

Originally Posted by minfranco

well how exactly would u do that without the light?

There's a big giant eight-sided object in the middle of the field. You should be able to find that without a camera. The camera just gives you one way of doing it.

[Bomberofdoom]

Well, two things:
1) You need to get to the exact point in between the two lights. The rack is allways twisted in the begining of the game. The point between the two lights can always be in a diffrent direction. How are you going to get EXACTLY to that point without the camera?
2)From what I've heard, the rack itself is can be moved less than a meter from the cetner of the arena, where we all expect it to be. Now how you're gonna' find the point?

[minfranco]

Originally Posted by kaszeta

There's a big giant eight-sided object in the middle of the field. You should be able to find that without a camera. The camera just gives you one way of doing it.

I get that it is not difficult to drive up to the light, and I'm perfectly aware of the size of the object on the field. Maybe you read the post to fast we are looking to do this in autonomous so if you have a method post it.

[Donut]

There are numerous ways of detecting the rack without a camera, including:
Sonar
IR Distance Sensors
Intricate system of limit switches
Banner sensors
Photogates

The problem is are any of these as accurate as the camera? In most cases I'd say no, but depending on how you implement them, who knows...

[psquared89]

Wow, I hope I don't start off a discussion off-topic or offensive to anyone here, but I am truly disappointed in this thread. minifranco came to CD asking teams for a little help, a pointer in the right direction, and all he got were a series of cryptic, useless responses of teams guarding their hard-earned success instead of sharing them, even the tiniest part of them, with the community. I understand the competitive nature of the game, but why would you waste both his time and yours by rubbing in his face that you had succeeded where he had failed; I don't think he much cared that you did succeed, congratulations and all of that, he came here looking for help.

That brief rant non-withstanding, I am not our team programmer, but I do have some understanding. One method that, if not entirely accurate, should be somewhat successful:

Take advantage of what you know:

1.) Where YOU are, call this position the origin.
2.) Where each light is, relative to you. You know the structure these points are mounted to. As you travel towards them, keep calculating the relative growth/decay in the brightness of each light; yes, the camera is flipping back and forth, but in this case that's a good thing, updating your data for the two points roughly once/2sec. Using this growth/decay data and your relative position and orientation (all being relative from your starting position and orientation, the only thing you can really depend on (and that's depending on your drive team...)), you can extrapolate the position and orientation of the rack.

This does demand that you have some nice sensors on your robot; wheel encoders will well enough for position relative to your starting origin, or an accelerometer if you're feeling bold.

Hope I could help and sorry for the rant.

[kaszeta]

Originally Posted by Bomberofdoom

Well, two things:
1) You need to get to the exact point in between the two lights. The rack is allways twisted in the begining of the game. The point between the two lights can always be in a diffrent direction. How are you going to get EXACTLY to that point without the camera?

I repeat, there are plenty of things to cue off aside from the lights. Look at the drawings of the rack.

And who says you need to get to exactly one point? There are many ways of making a scoring mechanism, and most of them should have a reasonable tolerance for "hunting" to find the spider leg.

Never assume there is only one solution to a problem.

(I'd tell more, but I don't want to give up too much strategy).

[kaszeta]

Originally Posted by Donut

There are numerous ways of detecting the rack without a camera, including:
Sonar
IR Distance Sensors
Intricate system of limit switches
Banner sensors
Photogates

Exactly my point. Our team has evaluated these, and some of these are surprisingly workable, or at least have been on our test rack.

[kaszeta]

Originally Posted by psquared89

Wow, I hope I don't start off a discussion off-topic or offensive to anyone here, but I am truly disappointed in this thread. minifranco came to CD asking teams for a little help, a pointer in the right direction, and all he got were a series of cryptic, useless responses of teams guarding their hard-earned success instead of sharing them, even the tiniest part of them, with the community.

I'm not trying to be too cryptic, I'm trying to reinforce the idea that there are many approaches to autonomous mode, not just one technique (camera imagery). The original poster asks a real question (how to position the bot between the lights, when many (most?) camera installations won't be able to see one or both lights at this location). I'm trying to point out that if you get to this point, there may be simple solutions one can try aside from or in addition to camera strategies.

Too many discussions I've seen make the assumption that there is one way of doing this, which simply isn't true. The simply camera approach might be the best way. The double camera approach might turn out to be better. I'm reminded of both of the last two seasons, in which people proclaimed early on that cameras were absolutely necessary, and in both cases, many teams went on to do surprisingly well without (Team 95's robot last year, for example, ended up without a camera since we found it gave little benefit)

The only cryptic part comes from not needlessly exposing our team's specific strategy too early.

Hope I could help and sorry for the rant.

You have some valid points.

[Tom Line]

There are dozens of ways that would work, with varying degrees of success.

You could use blob size to determine your angle to the front of the light. (Yes, yes you can. We've done it.)
You could track multiple lights with a single camera simultaneously.
You can track multiple lights with a single camera by switch back and forth between them.
You could track one light while dead reckoning. With 2 positions and distance measures to the same light, along with the distance of traveling, and angle from the light you can triangulate with reasonably good accuracy.
You can drive the arc of a specific distance of the light until you lose the camera tracking. This is very repeatable (you move along at the same distance from the light until you pass the "event horizon" of the light).

Basically, to be able to score on any post in auton, you MUST have a way of determining your position relative to the racks.

To be able to score only on the spiders under the lights is significantly easier, and I suspect you'll see far more of this in the early competitions.

The neat part about this whole thing is that while I've given you a good number of ways to do what you want - I haven't told you how we're going to do it

[Donut]

Originally Posted by Tom Line

To be able to score only on the spiders under the lights is significantly easier, and I suspect you'll see far more of this in the early competitions.

Indeed it is, and I know our team is going that route. We looked at trying to score on in between legs early on, but decided it really wasn't worth it unless we had alot of extra time to work on that.

Have you gotten autonomous to work for a spider leg directly under a light yet (the full autonomous mode, not just tracking it)? If you haven't, I recommend you do that first and not worry about dual-light tracking.