Mecanum Wheels is it good fin the Pits

[T3_1565]

Once kickoff is over, I will be posting up a new breed of omni drive systems (not mecanum though) which helps them with the pushing problem, if anyone is interested be sure to look out for it, I am putting the finishing touches on the design as we speak!

If you use mecanums on your robot, all you must is learn to drive with (not against) the force of other robots, this concept is applied in a lot of thing (martial arts mainly, as thats what I do for a living) and it will help you when driving.

Mecanum and omni are two very different drive styles than 4 wheel, 6 wheel etc.... So if you do make it, do your best not to drive like a 4 wheel or you will get shoved everywhere!

[Steve Kaneb]

Originally Posted by lineskier

For the past week or so I've been working on a design for a drive system implementing both mecanum and omni wheels

One of your ideas is to use only 2 motors to each side. I question the wisdom of this, as you're going to have to use much more real estate to get any kind of differential system in place. You might even reach the same amount of weight with a 2-motor system as a 4-motor system.
In 05, when we did mecanum, there was a small gear reduction to a chain reduction from the motor to the wheel, and it took up very little space. We were able to use field-oriented controls (with the old 150 degree/sec gyros and less powerful controller, so it should be pretty easy now) without pushing the weight limit.
Your design uses omnis to resolve the problem that mecanum wheels have with inclines, which is overstated. Last year, 3 or 4 teams with mecanum wheels were able to get up our ramps because they could drive straight. The problem mecanum robots have with inclines is if you try using the wheels as anything but straight on, you'll have control problems when the wheels lose contact with flat ground.
In 06, team 40 used 8" mecanum wheels and were able to get up that 30 degree incline. They just needed a running start, and the fact that they had their chassis high enough to take the crest.

[joeweber]

I would go with the one that will be rock solid so you will have fewer repairs and is easier to build ( cut down on assembly time) A drive motor for each corner is simple and safe. On our web site http://team1322.org/omni_drive.htm we have some instructions on how to build a simple mechanical joystick tie. The reason is as follows, in the coding for the robot drives there is a mix control for one joystick to tank drive. Use this to have the left joystick to control the left two motors. Copy and past it to use with the right joystick to control the right motors. With this mixing it allows you to go sideway when you move both joystick sideways, and allows you to go forward and back when both joysticks are move forward and back together. Now you can drive it like a two joystick tank control. The reason for the mechanical tie is to not allow the joysticks to move toward each other or apart. This is very easy to drive all directions with out allot of programming. We have tried all types of joystick configurations and this worked the best. I hope this was not confusing; I tried to make it a clear as I can with out pictures and diagrams.

[mwtidd]

Originally Posted by Borromakkot

In 06, team 40 used 8" mecanum wheels and were able to get up that 30 degree incline. They just needed a running start, and the fact that they had their chassis high enough to take the crest.

yesterday I stopped by your shop to take a look at the robot (im a junior @ wpi), pretty cool stuff. I was wondering if you are the one who is currently working on the code for that system(your coach mentioned someone was revamping it) because ive never used the gyros or encoders and i would like to get a feel for how to use them well

just a note on the omni wheels, the idea behind those were that the robot would not need a head start, it would be able to climb up the 30degree rather easily, i remember seeing robots just tossing themeslves up there, and its a pretty scary sight. especially for robots like ours, that are always at the max height
also the nice thing about the omni wheels is, if we have an issue with the mecanums, we can ditch them in mid competition and just switch to a tank drive
i also thought it may help with issues with pushing, i understand that the strength of the mecanums is getting away rather than fighting, but if you could get the best of both worlds it would be pretty nice

thanks again for the feedback