Swerve Drive vs Mecanum Wheel drive?

[efoote868]

I've seen veteran teams (my old team, for instance) use swerve drive trains and sit an entire match out for something stupid related to swerve drive trains (such as the wheels not aligned properly at the start of the match).

If you want a holonomic drive, and you haven't been tuning a swerve drive train for the past 4 years, go with mecanum. A word of wisdom: before you pick a drive train, pick a strategy on how you want to play the game. Then, build that drive train as quickly as you can during the build season and let your drivers practice all the way until the end, build a second if you have to and practice before the competition.

Doesn't matter what you use if you can't drive it.

[Tyler2517]

As some one who has design, built, driven both of the two drives.

Swerve if done right is something that is amazing. It is something amazing to see it drive for the first time. Little lone ours is so much more reactive then the mecanum. I have by far learned the most when building out swerve then i have about anything else in robotics.Our swerve even though it is easily 50%-100% faster then last years mecanum drive can still plow it around all day long.

We had dome mecanum several times and after learning to drive on of those, our swerve is driven in exactly the same way so it was not that much getting use to.

I still do not know if i would chose to do swerve again. We spend 100s of hours just making the parts. That time could have been spend making a good manipulator. The swerve this year is our teams greatest strength and our greatest weakness.

Its all about risk V reward. Even though on the field a swerve should always trump a mecanum.

[NickTosta]

A quick note: you probably should have used the search function, it seems like this debate comes up every other week. At any rate...

Originally Posted by Botwoon

I've used neither, but I can draw on enough of my experience to tell you that Mek drivetrains don't hold a candle to swerve in terms of speed, traction, efficiency, agility, etc.

I have seen mecanum drives that, at the very least, don't get pushed around. They won't really push much, but they can certainly hold their ground. Mecanum can be about equal in terms of agility, although you're right in that you can always build a swerve drive that's faster and more efficient. I can't comment much on the traction.


That said, as I noted above, this debate happens all the time and it basically boils down to this:

Both mecanum and swerve:
-aren't worth the effort most of the time, especially since most teams can't even build a decent tank drive
-heavy!
-complicated
-difficult and time consuming to implement
-have numerous points of failure due to the extra complexity, although it can be true that their failures are less severe/impactful than a tank drive failing depending on the implementation

Mecanum:
-easier to program (pretty sure they have this in the library nowadays)
-easier to design (pretty standard)
-as noted above, generally inferior in every way to swerve, although I have seen some implementations that are just "sometimes inferior, sometimes on-par" as opposed to "always inferior"

Swerve:
-very difficult to program for full control if you're going with independent modules, although getting a basic crab drive up and running is simple
-harder to design, lots of different implementations and things to worry about
-Theoretically as fast and powerful as a tank drive but with far superior maneuverability


I've personally programmed and driven a swerve drive with four independent swerve modules, though I've only driven against mecanum robots.

[jamierose]

Originally Posted by Botwoon

Keep in mind how many teams have won championships on swerve drives; it's a small number.

To add to this statement, there has never been a robot on Einstein with Mecanum wheels. This isn't to say that it will never happen, but just that it has not happened yet.
As a note about Championship-winning teams with swerve drives, the most recent Championship winner with swerve drive was Team 16 in 2012.

[Answer42]

Swerve is a huge resource draw that takes years to develop. Even if it is really awesome to design and work with. Mecanum loses far too much power to make up for its benefits. You can always easily come back to the logic that swerves, 6wd, 8wd, butterfly, ect have made it to Einstien, but never a mecanum wheel. In my opinion 95% of teams are better off just buying or manufacturing a west coast drive and practicing the hell out of it. Just my two cents though.

[aryker]

Another thing to keep in mind is your strategy for playing each game. To give an example, our team excelled last year with a 6-wheel tank drive because our strategy was cycling, and our drivers got very good at this. Speed was much more important than maneuverability for us, so it wouldn't have made sense to spend more time on a more complicated drive train. This year though, the heavy defense makes strategy a little different. The argument could definitely be made for maneuverability over speed in this game. In any case, your game play strategy should always determine your robot's design, not the other way around.

[Bob Steele]

We have done both but we keep coming back to a basic strong shifting six wheel drive. It is really a resource allocation issue.

I will say that a performing swerve is a wonderful demo robot... It consistently amazes everyone in how it can do what it does.

If you embark on swerve I would encourage you to make it a summer / fall project with no expectations of using it for that year's game. Refine your idea and your programming... do prototyping.... work out your bugs and put it in your arsenal of mechanisms you have refined.

It does come down to resources though... if you have a machine shop you can rely on, your own or a sponsor's, good student designers and good mentor designers for them to work with and the financial resources to do the prototyping by all means go for it.

I liken a swerve drive to the Queen on the chessboard...
A good one is hard to beat... its two weaknesses are reliability because of the complexity and software AND the relative difficulty of making a shifting one.

It can be done but it is tough....

It could be a great achievement for your team though, and something for your students to come together with and be proud of ....

That, alone is a good reason to do anything....

The workhorse of premier drivetrains is the six wheel drop center shifting drive base.
I guess it would be the Rook of the chessboard...or the Bishop...
A well driven one can be devastating in offense and defense..... and they are relatively easy to maintain and keep in the game.

We did a mechanum drive once....... once.... (Does that make it the Knight of the chessboard?....lol not really ... if it could jump over other robots maybe...)

your mileage can certainly vary.....

Most of all find something your students can be inspired by participating in the design and fabrication....

[Christopher149]

Also on a risk-reward perspective, if mecanum stops working out, you can swap the wheels for traction and/or omnis with hopefully minimal problems. Swerve is generally "go big or go home", IMO.

[efoote868]

Originally Posted by jamierose

To add to this statement, there has never been a robot on Einstein with Mecanum wheels.

This statement has always irritated me. Mecanum drive trains were extremely rare before AndyMark manufactured them, while swerve drive trains were (relatively) much more popular. The first year I remember AM mecanum wheels was in 2007; before that it took teams significant resources to manufacture them. If I recall correctly, two teams had them in 2005, maybe a half dozen in 2006, maybe a few more in 2007.

2008 didn't lend itself to mecanum drive trains (successful robots were geared 18fps+ with 2 stage transmissions). 2009 mecanum wheels were illegal, 2010 a large segment of the teams automatically ruled them out ("can't traverse the bump!"), similarly with 2012 ("can't balance on the bridge!").

Even now they're still taboo due to all the misinformation floating around.


In my opinion, "never made it to Einstein" has no place in this discussion because it ignores the wheel's history, as well as game designs and strategies. Until there is a year in which a large segment (say 20% or more of teams) in the FRC population uses mecanum wheels, I'm going to give no credit to that statement. After all, 100% of the robots on Einstein in 2009 had hard plastic wheels for their drive train.

[RoboChair]

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.

[Caleb Sykes]

Originally Posted by RoboChair

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.

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.

[Keegbot]

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.

[MichaelBick]

Originally Posted by RoboChair

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.

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

[Chadfrom308]

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.

[MetalJacket]

Originally Posted by Chadfrom308

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.

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