Accuracy of Omni drive?

[Daniel_LaFleur]

Originally Posted by teslalab2

Hi all! I'm building a robot with my money to finalize my arduino-wifi control system. Before I spend my own money on a lemon I want to know what drive system I want going to go with. I was wondering if any one had experience with 4 wheel X shaped omni drive. like this http://i.ytimg.com/vi/Z0lUTMBbu9A/maxresdefault.jpg

I don't want to spend money on encoders. I programmed encoders on my teams bot this year for mecanum, I just don't want that headache for this

So basically, can I even drive in straight line with this, or is it just as bad as encoder-less mecanum?!

Thanks

The picture you show is a diamond shaped Omni drive, and it drives very well.

It has the same motion profile as a mechanum drive (direction of forces and slippage) and the same drawbacks (low resistance to being pushed, less thrust in direction of travel).

PID is not needed for this drivetrain but it can help if the motors (or frictional drag) are not closely matched. A gyro will allow you to do some field-centric control (however it also introduces gyro drift), otherwise the control will be robot-centric which gives some drivers issues.