Optical shaft encoder on mecanum drive

do i need four Optical shaft encoders on our robot that uses mecanum drive or will only one or two do?

em, i used two when i was doing simple autonomous (not strafing) …

One is all you need. Technically, four would be more accurate. But you should be perfectly fine with one. We did that least year (admittedly with IMEs), and it worked well. That’s the plan this year, too.

Our team also used only one. It never posed any large problems. I am not the programmer but I remember having void functions helped a lot .

One assumes that wheel is the one always touchign the floor. With the bump that may not be the case this year.

My high school team uses 1 encoder at a time and resets it to zero after every move. They avoid slippage by always using the wheel that is pushing and not pulling.

Couldn’t you go by the encoder that’s traveled the shortest distance?

I am sure it is design dependent, but we noticed a slight bit of slippage (maybe 1/4 revolution) from the wheel that hits the bump first. I believe it can be done with just 1 encoder on most bot’s, but would take a little trial and error to see which wheel works best on a specific robot. A lot of this will depend on the center of gravity. With RobotC or Convex the live debugging should make this a snap.

Yeah I really can’t wait to start taking advantage of ConVEX’s more advanced debugging setup :). I wanna write a custom debug window for doing work with it. We’ll see if that ends up happening.

Also, what I meant was if you could have an encoder on both front and back and for each section of the code just default to the one which has traveled the shortest distance. This should always be the wheel with the least slippage. This has worked fine for me in that past.

I did not take that into consideration, thanks for bringing that up.

However, if all the wheels are chained together ( If possible) the wheels should all spin at the same speed, then it should not affect the rotation speeds/ number of rotations . If you can not chain your wheels together, then this will not help.

Not sure if you’re aware or not, but mecanum drives use these wheels. Each wheel has to have its own power source, and be able to move independent of the others. In other words, he absolutely cannot chain them together.

I know that mechanums use those wheels :D. I mentioned that if this was possible if you could chain them together. I should have reworderd that sorry ( no more posts from me when im tired :o) If a tank type drive is used then it is possible, however this is a mechanum disscusion, So no it would not be possible your right :D. sorry about that.

Our team used mechanum for sack attack, But this year the bump would mess up the rotations so i would agree with drdanielfc that this is the best option