Re: Autonomous Perception
 

Its carpet, so IDK if the optical one will work, but the ball definitely will, another way is using the encoders on 2 non motorized wheels facing east and south...

Re: Autonomous Perception
 

Probably would want to make a larger-scale version. That ball is tiny compared to the field it's on.

The ball could also solve the crossing the bump problem. If we set 4 encoders on the ball at 90 degree angles from eachother, then if 2 opposite eachother go the same direction for a period of time (hence the larger scale version to expand the window of time), then the bot would know it's not on the ground anymore. Even if it happens when not crossing the bump, we know that something has just caused the robot to leave the ground and tracking would need to reset anyways.

Should it also have a horizontal roller to detect changes in angle? With all of this combined we can get most of our position detection done with just one sensor (plus a gyro or compass for sanity checks?)

Re: Autonomous Perception
 

Only 2 encoders are needed

Re: Autonomous Perception
 

A ball mouse doesn't get good "traction" on the carpet. It skips. Perhaps a largish rubber ball could be used as an intermediary between the floor and the mouse, to keep things moving well.

A typical optical mouse can't keep up with the speed of the robot. A couple of us tried doing a "telephoto mouse" system a number of years ago, but it turns out that any variation in height above the surface changes the scale of the image enough to mess with the sensed travel distance.

Re: Autonomous Perception
 

We've been there:

http://www.chiefdelphi.com/media/photos/30154
http://www.chiefdelphi.com/media/photos/30740

It's a billiard ball, about 55 mm in diameter if I remember correctly. It took us a while to get it to work reliably, and even then required some petting (cleaning carpet lint after every match, watching the disks, etc.). It was a very good experience for the team, but I think two omni-wheels perpendicular to each other would work better.

Re: Autonomous Perception
 

Is the middle wheel required? but I also think the wheels are the best choice

Re: Autonomous Perception
 

You mean the spring loaded arm that contacts the northern hemisphere of the ball? If so, yes, it kept the ball from popping out of the socket.

Re: Autonomous Perception
 

Why? The rise-fall detection would never work with only 2 unless other sensors are added, and even then you can't detect rotation.

Re: Autonomous Perception
 

The rotation can be checked with the gyro and then only 2 encoders are needed

Re: Autonomous Perception
 

Great article on 3d sensing http://www.cs.stanford.edu/people/an...nipulation.pdf

Re: Autonomous Perception
 

I think I just found the solution for telling where you are when you go over the bump:
Robots usually only slip on the way *up* the bump. On the way down, their back end may get some air, but all the wheels are still moving at the same rate.
A robot can use the Z accelerometer to tell when it's at the top of the bump, and use IR (because it has a very narrow beam) to tell where you are horizontally. (It's assumed you know *which* bump you're on, but if you like, you could use a colored phototransistor to tell the color of the bump.)
Alternately, SONAR could be used once the robot has gotten down off the bump.

Re: Autonomous Perception
 

I don't really trust using encoders until you can zero into a known position after crossing a bump. Even if the wheels are coming down with the robot, it looks like most robots do slip a fair amount from momentum. If you can get a VERY accurate sonar that would be okay for re-detection after clearing the bump, but I think the risk of another robot interfering is a bit too high with that.

Also, what would happen if you were to land on another robot after crossing the bump. It's certainly possible with the tunnel bots that are about the same height as the bumps. Is there any way of detecting and preventing this?

Re: Autonomous Perception
 

I know the Maxbotix SONAR is accurate to an inch, and it would take +-9mV of jitter to throw it off (if you round the value after you receive it).
This sounds like something that would be easy to test with current robot configurations. I'll make a list of things I need to test.

Perhaps the surest option is to re-square yourself on the bump after you go over.

Re: Autonomous Perception
 

Late-night thought:
The XL-MaxSonar give you the "real-time envelope" in analog, so you can do your own processing. If you had one with a very narrow beam, you could record the acoustic signature (amplitude over time) of the gamepiece, and use that to determine if you're pointed at a gamepiece.
The problem with this is, if the gamepiece is a sphere, this may make the robot think that every sphere is a gamepiece.

Re: Autonomous Perception
 

http://www.societyofrobots.com/robottheory.shtml
Very Very good articles to read about