Moving to a point between lights with autonomous

[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?

[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).

[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 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.

[kaszeta]

Originally Posted by Donut

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.

We're counting on filling in the gaps between the other teams going for the ones under the lights...

[ebowla]

Yea, Donut has a point. Our team started this year and I do most of the programming. I haven't been able to figure out a way to pin down the spot between lights due to the movement of the rack with a camera and encoders, but I can get a tube on any spot under lights, thats 12 spots we can get. So even if you can only get the ones under the lights, it doesn't mean that you're at that big of an disadvantage. (although if your team can get 3 keepers in a row horizontally you are in pretty good shape)

[CircularLogic]

Disclaimer: I do not have a robot, nor have I seen a robot the entire season (stupid graduating High School to go to college). However I have been thinking about this for quite some time.

Note: I fully thought it out around kick off. This is what I remember. Hopefully it can get you thinking in a good direction.


The first thing you need to have planned for in your autonomous is knowing your starting position, because that will make a difference later on.

When the autonomous period starts, have your camera track the closest light. Figuring out which light is the closest should be able to do be done relatively easily based off of the fact that you know all cameras are a constant distance apart. Then simply do an an angle check of the pan on the camera. If its too great, tell the camera to search the other way.

Now, once you have that target, you can make some reasonable estimates about the position of the off-light row. Using trig (specifically the law of cosines) you should be able to calculate the distance you need to adjust your robot in the X axis direction. That requires some ability to make reasonably accurate turns and movements (if you dont have some type of closed loop system, I would say go with the slowest viable speed to make those movements). Once you are aligned in the X direction, deploy your mechanism and drive forward the estimated distance that will get the ringer on the spider. I realize that you will be approaching the spider at an angle, but worst case scenario is about a 45 degree approach to it, which most arm designs should be able to handle.


Its not the best way. Its probably not fully thought out. It absolutely isnt tested. But the the thing it has going for it is that the math will work. There are a number of known things about the field when you first start the match, you have to use those to your advantage. It involved a lot of angle calculations. It involves creating lots of triangles to figure out distance accurately. When looking to make those triangles, remember a couple of things. Your robot will always be approximately the same distance away from the rack regardless of orientation but dependent on starting position.

The straight line distance is between spiders is a very useful thing for creating triangles.


Good luck.

[1768]

Our team can (probably) score between lights. I made a rom table of trig values and used that to approximate where each light is. Knowing two lights and their relative positions to each other, it can find the center of the rack and angle of rotation, and therefore where leg #3 is. Of course, this is still untested.

[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.