Line Tracking in Toss Up

I’m one of the lead programmers for my team, 2581P/2581B. Line tracking is one of the most accurate ways to navigate during the autonomous part of the competition. The issue I’m have this year is how to keep the line followers 1/8" from the ground with that 2" bump. Any suggestions?

Use an accelerometer to watch for a change in height. If one occurs, cancel the line follower code temporarily and when you’re back on the ground re-engage it.

Would that work?

I problem is not following the lines while I go over the bump, the followers will pick up the line again on the other side. The problem is how to cross the bump without bashing the followers on the bump.

Put them in the middle of the robot, the accelerometer in the front. As the robot drives forward and the front raises, have code built in to automatically raise the line followers. Use Linear Slides, Pneumatics, anything. When the front comes back down, wait .5 seconds and then lower them again.

Would that work?

The most ideal to place line followers is in the center just in front of or behind of the center of rotation. With standard 4-wheel driven drives, this can be somewhat of a problem because the center of rotation is where there aren’t wheels to guard the line followers. The best thing to do (in my opinion) is to put the line followers pretty much in line (front to back) with a set of wheels and in the center (left to right).

If you have a 6wd, you should be able to place the sensors under the center wheel … Unless you plan to straddle the bump at some point, they should be protected

Has anyone built a working 6-wheel drive that crosses the bump? The one we tried (admittedly not with a 4" wheel) got stuck. We get across fine with Mecanums and 4-wheel Omnis, though.

Thanks guys. This will hopefully help. I’ll take the suggestions to my team and we will see what we can do. And yes, there are youtube videos of 6-wheel robots, using 4" wheels.

Wow, don’t know how I missed that. Here’s a video for anyone interested. I would recommend the 6-wheel drive approach, then.

Yep, my team is currently using a 6wd with the 4" omni wheels and it has no problem going over the bump. You just have to make sure that there isn’t enough space for the bump to fit between the wheels and contact only the metal of the frame (no wheels touching the bump is no good) and you can go over with no problem.

If you do the 6-wheel drive correctly, you don’t even need to do any extra drop for the wheels like there is on the 4 wheel drive robot in that video

Apply the sensors next to wheels so the bump hits the wheels rather than sensor itself. Since our drivetrain was a C, we plan on placing another on our drivetrain booster or attach a weak/bad rollguard so that way when the rollguard/booster hits the bump, it just folds up

I’ve also debated whether we should try placing sensors on both sides of the line so we don’t need the extension. Never used line followers before, so i dont know how useful that’ll be

I you place three line followers in line with the y-axis of your robot, then three in line with the x-axis of your robot, you wont have to turn to change direction. This would only be useful if you can drive sideways. Any more line followers than this would be useless and just take up sensor ports on your brain.

I don’t completely understand what you’re trying to say… I believe you’re saying place line sensors in an “+” or “|–” pattern. But the main part I don’t understand why you don’t need to turn to change direction.

You can strafe. If you have the plus pattern, you can maneuver nearly the entire field without turning to follow the lines.

If you need to turn, you still have to turn.

You could also have the sensors mounted so the force the sensors hitting the bump pushes the sensors out of the way, but a rubber band would bring them back into position after the bump

That sounds much more difficult to build and maintain.

It does, but I will try it to see if it works this week

The simplest approach is to have the sensors in line with your wheels, that’s what we’re doing on our robot.

Also, welcome to the forum, 2581B/P! I remember you guys from the MSU scrimmage, and I’m looking forward to what you guys have in store for Toss Up!

Is there a specific distance from the ground that the line sensor has to be mounted? Our line sensor is not working. It does not detect the line and continues going forward instead of taking a turn