Autonomous part

[Reda]

hi, my team and I want to know how other teams are doing to do the autonomus part without any sensors, because we have a lot of issues in the same code

[9MotorGang]

There are already lots of threads about this already. A simple search of vex autonomous help would reveal lots. What specifically are you unsure of?

[Reda]

the problem is that we are using vex code blocks , when we put the robot at the same place , sometimes it doesn’t do what it should do , and also we were interested to know if we are doing well

[74656A]

If you have an issue with your code, then post your code. I have a feeling that you are using time.

[Reda]

We are not using time , intead we are using turns in our code

[74656A]

Can you post your code?

[9MotorGang]

@Reda

when we put the robot at the same place , sometimes it doesn’t do what it should do

This is a problems that every team faces. You might find this helpful.

Autonomous works then doesn't...help

Team mom here trying to help our middle school kids solve our current frustration. Our autonomous programs works sometimes and doesn’t other times even if we don’t change ANYTHING! Same code, same setup, same field…it’s maddening. Happens to us nearly every competition and even sometimes during practice. First run in the morning - all is well. Second run (no changes) - complete fail. Robot goes way off course as if it’s using some other code that they didn’t program. Then we descend into the pit…

[Reda]

[invalidflaw]

So first, I really think you should consider moving to V5 text in the future. Your code is becoming fairly advanced for blocks(thats a good thing), and text code is better understood and easier to debug by the community.

With that little aside out of the way. What is the robot not doing the same. Is the robot moving different distances every time? If that is the case it could be your wheels are slipping on starts and stops. You could reduce this by slowly accelerating the motors at starts and stops.

[Reda]

first of all, thank you for your motivating remark and I wanted to say that the angles are different each time by a few degrees which becomes annoying because it
misses a lot of balls

[invalidflaw]

My strong suspicion is that either your wheels are slipping or your turn center is changing. If your wheels jump or spin out at the beginning or end of turns, it is expected that your turn will be a little off. You could verify this by slowing down the entire autonomous.

Turn the speed of the auton down to say 15-20%. Don’t worry about how long it takes. Is the the run consistent for 3-5 runs? If the answer is yes, then you need to change how your function accelerates/decelerates in turns.

Secondly, what type of drivetrain are you using?

[Reda]

we are using a drivetrain with two omni wheels and two regual wheels(like the crunch bot’s but slightly different) we have also a problem with measuring distances. It’s never accurate and we always have to test it over and over again to get the right one. The way we do it is measuring the distances manually in cm and dividing them by 4 pi to get how many turns our motor should make to reach our target position. Do you know any more accurate way to do it?

[kay]

To increase accuracy without using sensors or advanced techniques (like PID), your best bet is to slow down the movement a lot. At a minimum, slow down when the robot starts and stops a movement.

[Reda]

ok , and how can we do to measure distances ?

[kay]

For starter, encoder is easy to use. For turns, IMU is a good choice (beware of strafing issue).