To Strafe or not to Strafe

I’ve been reading up a lot about mecanum and omni-wheels here and other forums online. Most of what I’m seeing is “X wheels are great and easy” or “rule 1- never use X-wheels again”, both with sometimes one line for why.

Watching youtube videos of both, I’m seeing that they certainly get the job done, but requires a lot of skill from the driver.

I guess what I’m asking is if people could give a little more detail as to why or why not they are using mecanum or omni-wheels.

To help me search (and possible consolidate the list later with answers and credit) please list your response as:

Mech +
good reason

Mech -
bad reason

Omni +
Omin -
Mech/Omni +
Mech/Omni -

This is a link to a fantastic power point made by 1675 that answers the questions you are asking.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0CEQQFjAG&url=http%3A%2F%2Fwww.chiefdelphi.com%2Fmedia%2Fpapers%2Fdownload%2F2878&ei=X4muVPTbA4mjyQT09YLIDw&usg=AFQjCNEXVJgXzSxZrEKUG3-fitLaeCXIcw&bvm=bv.83134100,d.aWw

Keep in mind that a lot of CD posts warning against mecanum and omni are based on previous games, where the lower pushing power of these drives allows the to be susceptible to defense. However, this year, change has come, and omni and mecanum will probably be much more common.

Perfect

The best answer to the poll, would be to select ALL the answers.

They can all be valid answers, but it depends on how you implement it, if you have previous experience with it, and how much time you want to put into designing, programming, and practicing, with your drive system.

Would that time be better spent on a game piece manipulator? Maybe. That’s your decision. Just remember that for every hour you spend tweaking one subsystem, that’s an hour taken away from something else.

@Fields:
You have one of the best teams (in terms of Mecanum) right in your backyard - FRC 2052 Knightkrawler (Irondale). You may want to reach out the them and Ask what to expect.

FRC 4607 CIS will not attempt Mecanum this season - but from what we have seen from slide (omni’s in a H-config) we most likely will be working with that.

Why a need to strafe I feel if your team is comfortable and know that your crab, omni, mech wheel combo will work but the bump is so low there is no reason to dodge them you can get across the field much faster if you traverse the bumps well you really have nothing to out maneuver

If you chose to use the “H” or slide drive wont that middle wheel get high centered on the bump?

4269 plans to use a mecanum drive again this year. We developed a system that utilizes a gyroscope to track the robot’s orientation on the field. When the drivers push the joystick, the robot will move in that direction, regardless of it’s orientation.

If you do go mecanum, you need to start working on it now. I’m not a programmer, but the code is very complex. You also need to make sure that your chassis is designed to run mecanum (wheels must be in a perfect square, neutral camber, etc.). These were challenges last year.

Good luck!

We are sticking with what we already know we can do very well: a tank-drive system. We believe that a mecanum system is probably better for this year’s game, but having not done one for a long time, we would introduced a lot of unknkowns into our build season and potentially create a very real time crunch while trying to perfect our manipulators.

We can make up for many of the advantages of a mecanum drive through some create creative programming for a tanks system (we know we can do this) and by making sure that our tote-acquisition-manipulator has a way to make lateral positioning adjustments…

the programming libraries have built in functions for mechanum and because of this my teams programmers believe it will not be very hard.

It all depends on the complexity and necessary precision of the task you are attempting to program. :slight_smile:

We miscalculated on the amount of defense last year, and went mecanum. Our programmers got mecanum working from the libraries in about two weeks from a cold start. We’re going omni H-drive this year - we’re doing a “bottom stacker”, and feel that a bit of strafing is going to be essential to quickly and precisely line up on the totes. We decided to pass on mecanum this year because of the issues with a moving center of gravity.

When you experimented with H drive in the off-season, did you find that it was less affected by variations in center of gravity than mecanum is?

What kind of creative programming are you going to use? In my experience with tank drive I haven’t done anything more fancy than limiting the rate of acceleration, I’m curious as to what can be done.

To Strafe, w/ an Omni Crawler Drive though. This is the year to do it. The year without real defense and no bumpers required or necessary. If you use the triangular 1 it can tip over and still keep going…and going…

Hee, hee…Then there’s the Water Game! (Ok, that water is slightly frozen…But the 2016 Game could be held in outdoor colder locations and the field just a wee bit larger and colder is all). Posted to try and give the GDC ideas to give the fans what they have always prayed for…A Water Game! Using the 1929 Fordson Snow Machine concept of course. (There has to be a way we could tweak that so it wouldn’t turn the carpets into huge balls of yarn). Any ideas?

So what happens when the field melts in those warmer regions? Still a water game. (Only wetter and muddier).

“Guardrails can’t hold us!”…I know how I’m getting to the ski slopes from now on…Anyone still have a 1929 Ford around that’s still running or in decent shape? Lol. I’m going to make me 1 of those Fordson Snow Machines.

Why do you think that a square chassis is required to run mecanum?

Has anyone had any luck with having two traction wheels in the front and omni wheels in the back? This would allow you to pivot at the front rather than the center which makes getting totes easier

We did it in 2008 and it worked fine but you need to make sure that turning around the ends of your robot is what you really want.

I found the kitbot for that crane we have been looking for, and it Strafes nice at 2:14 of the video.:smiley: