We are a new team and are excited about the build and comeratery that is present in this group.

We are looking at using a 4 wheel omni drive system on our robot. We are looking for help or a sample code that can be used to start us out on this large but interesting task.

Any help or information will be greatly appriciated.

Gwinter,

It is really important you understand the underlying math of an omniwheeled system. It's not terribly complex but it really makes things easier. I have a somewhat working omniwheeled robot that I am working on at the moment. It uses 3 wheels instead of the 4 you want.

This is the code I have:


For any given wheel, the speed it needs to turn at is :
Vw = Vb (cos Aw * cos At + sin Aw * sin At)

Vw = speed of the wheel
Vb = speed of the robot's body
Aw = the angle of the wheel on the body
At = the angle at which the body is travelling

So for a robot with 3 wheels (at 0, 120 and 240 degrees around the body), like my example, you get the following formulae:


Sometimes a term will disappear from the calculations because it's 0, sometimes it's simplified because it's 1. You need to figure out what angles your wheels are at and create the formulae for your Vw1, Vw2, Vw3 and Vw4.

I am not going to give you the answers, you have all the information here for a robot with 3 and a generic formula.

You need to figure out why I have the following code:


Good luck, if you have more questions, don't hesitate to ask, but don't ask me to write out the formulae for the 4 wheels, you should be able to do that yourself.

Regards,
Xander

I have figured out all the codes and the 4 wheel coding and alot of the formulas drop out with the use of the wheel angles. So it is simple. I am confused where the Vb and the Angle the body is traveling (At) comes from.

Are you using a gyro for input.

I have developed an array to draw the sine and cosine vales from vice using the nxt to calculate them each time. This should speed up the process.

I have also written a code for using joysticks to directly control the motors will this work in direct control modes.

gwinter

Vb is the velocity of the body. A four wheeled omniwheel robot is much more efficient when it comes to translating the motor's movement to that of the body. At is the angle at which the body is travelling. You should check out http://nxtasy.org/2006/12/27/omni-teaches-physics/ for more info on the physics of this. Also be sure to read up on this http://technicbricks.blogspot.com/2008/ ... ns_29.html


Nope, math is all I am using for now. I am planning to make it remote controllable (as well as autonomous) using the new HiTechnic IRReceiver sensor.

Regards,
Xander