Re: Swerve Drive vs Mecanum Wheel drive?
 

Mecanum if done well, geared for agility, and absolutely programmed FIELD CENTRIC and then practice the hell out of it can be a very competitive drive train. Anyone that does not put in the effort to code and set up a mecanum drive for field centric is wasting their time. I have seen many teams drive mecanum like a tank drive with only the occasional strafe/rotation and this is a waste of time. You can dance across the field dodging defense all day if you can just move the stick and your robot moves that way on the field no matter where it is pointed. But if defense catches up to you that's it, you must be faster! Mecanum shouldn't really even have a tank style drive mode.

Re: Swerve Drive vs Mecanum Wheel drive?
 

Though this is the practice ramp (only pic I have on me) we could quite easily

Also 2012 bump? no problem

I loved our mecanum robots, they worked really well.

They work an unbelievably better when controlled by encoders and PID as well, the only reason we stopped using them is because we hate getting ruled off scouting lists for no reason but them, even though in 2011/2012 we pushed so many robots you would not even imagine.

And mecanum is really light. in 2012 and 2011 we used ToughBox nanos with the output direct driving the AM 6" wheel. Any 4 CIM chain tank drive is going to weigh just as much. Also they take up almost no space (note our 4 sided intake!)

Re: Swerve Drive vs Mecanum Wheel drive?
 

This is another reason mecanum can suck, because of the number of teams that don't utilize the full benefits of the drive most competitive teams will cross you right off of pick lists. You have to SHOW that you can rock it well with some epic driving to avoid that fate(this is one of the things 1678 looks for when scouting).

Re: Swerve Drive vs Mecanum Wheel drive?
 

I think that you are focusing on the wrong issue here. The issue with most team's mecanum drives is not whether or not it is field-centric, but whether or not teams have practiced driving it like a mecanum drive.

I agree that field-centric drive is awesome (and fun to code:)), and I might even agree that it is easier for a new driver to learn. However, if, on the last day of build season, I can give the programmers the robot to make field-centric code, or I can give the drivers the robot to practice, I will choose the later without hesitation.

For 95% of teams, the limiting factor for their drive system is the driver, not the motors/wheels/gearboxes/code. I would argue that a well driven standard mecanum drive could easily hold its own against a well driven field-centric drive.

Re: Swerve Drive vs Mecanum Wheel drive?
 

I don't think mecanum drive needs to be field centric. We don't and we are still a very competitive team. If you can build it and drive it well, mecanum can be effective.
On the other hand, this year's Hawaii Regional was the first time I'd seen a swerve drive (or one that works well) and I was thoroughly impressed. 368's drive was able to maneuver super good. Our team will hopefully do an off-season project with swerve. If we get it right we may try it next year.

Re: Swerve Drive vs Mecanum Wheel drive?
 

Popular belief was wrong, and there weren't many teams to challenge assumptions.

Even the belief that swerve drive done correctly is always better than mecanum drive done correctly is misguided. The teams that use swerve drive year in and year out effectively tend to have great organizations along with better than average resources. I'm not convinced these team's competitiveness entirely derives from their drive train. Likely they'd be just as successful with a 4/6/8 wheel tank drive, a mecanum drive train, or some other drive train.

Re: Swerve Drive vs Mecanum Wheel drive?
 

Personally, I like both Mecanum and Swerve. However, my team decided that we weren't really looking to make a swerve drive due to the resource and experience concerns. Instead, we went with a modified octanum drive. With butterfly modules comprised of mecanum and colson, we feel as if we have achieved a similar performance to Swerve, but without several of the sacrifices.

When considering drive trains, you must consider everything. Do not make a hasty decision whilst either scouting or building. I suggest looking up 1114's drive train documentation. Implementing a system that allows for decisions based off of quantitative data enables a team to make intelligent choices.

Re: Swerve Drive vs Mecanum Wheel drive?
 

Team 174 Arctic Warriors do belt driven swerve drives every year. It's honestly ridiculous if you get a chance to see it but it works well and it's really cool.

Re: Swerve Drive vs Mecanum Wheel drive?
 

I have never personally seen a swerve drive in person, but only in videos. This is the first year that my team has used mecanems. We decided that we also wanted to develop a new drivetrain to go with it. It is sort of an octanum drive base. We used 4 4" mecanem wheels and 2 six inch traction wheels. We have gone through 2 district events and gotten second in one. The first event we got pushed around a decent amount, but in the second, we got pushed around less as we got better driving. The traction wheels also allow us to play some pretty good defense too. The choice that teams make between tank, mechanems, and swerve should be based on their desired strategy that year. I have found mechanems to be the greatest wheels i have seen when lining up for the one point goal. Since they can "drift" it makes it easy to drive up quickly, and then move side to side to put the ball in quickly. I have seen numerous teams have to line up multiple times when they try to get the ball in.

Re: Swerve Drive vs Mecanum Wheel drive?
 

To be fair, one of the finalists on curie in 2008, 2171, was running mecanums. And IIRC they were actually using them as well (to weave through traffic).

Re: Swerve Drive vs Mecanum Wheel drive?
 

I disagree. The most competitive mecanum robot I believe I have seen is 2052, who had a tank mode. the tank mode helps because it keeps your smallest side going through defensive holes:

https://www.youtube.com/watch?v=Ogy65hEPIXk

Re: Swerve Drive vs Mecanum Wheel drive?
 

Team 308 chose mecanums over swerve this year because it was easy to install, probably lighter, and less points of failure.

We chose mecanums because we wanted to avoid defense. And, at least I think so, we have done this correctly. It takes 2 and sometimes 3 robots to keep us from moving. We have incredible power on our drive train and incredible programming though.

On each wheel, we have a toughbiox mini with 1 big CIM and 1 min CIM. (Yes technically we have an 8 CIM drive)

This allows us to accelerate crazy fast, which helps with all the defense,

Programming wise, we have 5 PID loops on our drivetrain. I'm not a programmer, but how I think we set up the PIDs is the based on rpm from each wheel, us telling the PID how fast it should be going. We have 1 PID on each wheel, and one for rotation. It's cool because you can push our robot and it will push back with independent power on each wheel. And speaking of pushing, that's how we play defense (sometimes). We sit in front of a robot and step away from the controls and it does the work (mostly) by itself.

We spin around each robot when trying to be defended, and when defending, we push corners and even head on. We can normally stop robots from moving at that point.

We don't get pushed around easy, although it may look like it. We have adapted to rolling with defense and spinning off whenever we have the chance.

We have shut down power house teams from scoring with mecanums.

Re: Swerve Drive vs Mecanum Wheel drive?
 

Do you have any video of the automated push-back? It sounds epic.

Re: Swerve Drive vs Mecanum Wheel drive?
 

As a mecanum lover, it really annoys me when people automatically rule out mecanums when the really don't know what they are capable of. Our robots in 2010 (http://youtu.be/rdAKiuimaY4?t=58s) and 2012 (http://youtu.be/tdAncHeHOEQ?t=1m36s) had mecanums and they could traverse the bump and balance on the bridge.

I especially agree with this. In past years we have driven our mecanums mostly as arcade drive and with crabbing at the press of a button. You can see the ineffectiveness of this in our video from 2012. This year though, I implemented a really cool (in my and the judges' opinions [we won the Innovation in Control Award for it at two districts]) field oriented drive mode that we use exclusively. I read about the idea on CD and decided to implement it early in the build season, so we had a lot of time to practice with it. Even though we aren't extremely powerful, we are agile.

That sounds really cool. I was thinking of using PID loops and encoders this year but I decided it was just easier to use a gyro to maintain our orientation if we were pushed and to correct for traction or weight imbalance problems, mostly because we have had bad experiences with encoders failing in the past. I might try that along with extra miniCIMs in the offseason.

Re: Swerve Drive vs Mecanum Wheel drive?
 

Is there something unique about the way you did it?

Field oriented control has been around for a number of years. It's built-in to LabVIEW and WPILib for Java and C.