2775J 24 Pt. Programming

24 Pt. Skills Autonomous

Feel free to ask any questions about our vision sensor!



Great route. What exactly are you using the vision sensor for?


From what I can tell, realigning after turns to get the cube/tower.

At least that’s what it looked like to me


@Doctortictac is correct. The sensor aligns with orange cubes to more accurately turn to a position.

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What will you do if the fields are not set up with the correct color cube in every position? Many skills fields I have seen put them in the right position but don’t care about colors.

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The skills fields are supposed to be set up with the colors in the right places, so if they came to a field that was set up wrong, they could probably just point it out and change it.


For sure.

In fact, the official Q&A says the cubes should be in the correct places so they should be able to get it fixed easily.


How exactly did you get the vision sensor to align so perfectly with the orange cube. Does it ever mess up with different lighting?


Our lead progammer used a simple p-loop for the drive’s velocity to center the robot accurately on the orange cube. This actually boosted to program’s consistency by quite a bit!

As for the different lighting, yes:

At Kalahari Classic, we had issues where we calibrated the sensor off-field. The referees eventually allowed us to calibrate on the skills field, which allowed us to complete the run successfully.


Question: are the mechanum wheels the reason for the “wobbly” turns or is that the vision sensor?

The “wobbly” turns are partially a result of mecanum wheels, but are also a result of a drift correct loop which ensures both sides of the drive go at the same speed. You see something similar around 0:07.


I figured that much. have you tried lowering the drift correct value? I use this same thing when driving straight and fine tuning the correction loop allowed me to increase over all velocity because I did not have to worry about the velocity difference anymore.

I believe our value is pretty close to optimal, but we can certainly look into tuning it. Thanks!

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What is a drift correct loop? And did the vision sensor help you out a lot?? Like is it worth it.

A drift correction loop or straight-line correction loop basically adjusts how much power is sent to the different sides of your drive to compensate for any variations in the right and left side. Basically, if the right side is falling behind the left side or a set target velocity, it will boost right side power and or lower left side power. If you use the integrated encoders and vex’s integrated PID controller then this isn’t really necessary.
Edit: Forgot to mention why @2775Josh and I use them. If you write your own p controller then you will want to use voltage to control your motors which does not use the integrated velocity PID. So we have to manually compensate for variation.