Mecanum or Swerve?

[buildmaster5000]

During the offseason this year, my team has discussed developing swerve drive, but after seeing a number of teams use mecanum with great sucess, I am torn between the two. Mecanum seems simpler and lighter, while swerve seems to give better control and more pushing power/resistance to being pushed. What are the experiences of the rest of the FRC world?

[sidkulk]

I think the choice between mecanum and swerve lies in where your robot is best suited to play (offense/midfield/defense).

Offense: Swerve
From watching quite a few matches, swerve seems alot better suited to collect balls and maneuver them into the goal.

Midfielf: Swerve
When your playing the midfield balls constantly keep entering, so you need to be able to quickly "pick up" balls from your zone. And if your in the midfield, theres a higher chance of you needing to go over the bump. So if you use mecanum it seems you need to drive straight to go over on mecanum, but you can go also sideways with swerve over the bump

Defense: Mecanum
Mecanum seems better here because its alot easier to get from goal to goal and just block the goal from other robots scoring.

[davidthefat]

I say go for the 4 or 6 legged robot. First because with 6 legs, 3 legs are ALWAYS touching the ground (Of course unless its falling off a cliff) minimum of 3 legs needs to be on the ground to be stable. Yes I do mean LEGS... Its more adaptable then wheeled vehicles. I mean look at the Protoss Colossus

[thefro526]

In My personal opinion, Swerve > Mecanum > Holonomic, and this goes for just about any game.

If you've got the resources, both Manufacturing and Programming, go with a swerve. Swerve drives have the traction advantage over all of the other omni-drives out there. Swerve drives can be complicated to build and drive though, so be careful (Though, you could look into the team 221 swerve modules). Personally, if I ever built and omni-drive for any game I would build a swerve.

Mecanum Drives are probably the most accessible form of omni-drive out there. You can use the kit frame, AM Mecanums, and some off the shelf transmission and have a reliable Mecanum drive. Mecanums lack the traction of a swerve or traditional drive so watch out. Mecanums can climb decently though, so this is an advantage over a Holonomic.

Holonomic Drives are interesting. They're somewhere between a swerve and a mecanum in terms of build difficulty, due to the fact that the wheels must be mounted 90* from one another. (or 120*) They also can be a bit of a handful to drive, and they REALLY don't like un-level playing fields. Holonomic drives also don't push well.

[buildmaster5000]

Originally Posted by thefro526

If you've got the resources, both Manufacturing and Programming, go with a swerve. Swerve drives have the traction advantage over all of the other omni-drives out there. Swerve drives can be complicated to build and drive though, so be careful (Though, you could look into the team 221 swerve modules). Personally, if I ever built and omni-drive for any game I would build a swerve.

We had looked into the 221 modules, but had decided that with our small team (12 members) it would be better to have an operable robot with a 6wd than a swerve that did nothing. We also only have 1 programmer and build in a basement, so our manufacturing abilities are very limited.

Originally Posted by thefro526

Mecanum Drives are probably the most accessible form of omni-drive out there. You can use the kit frame, AM Mecanums, and some off the shelf transmission and have a reliable Mecanum drive. Mecanums lack the traction of a swerve or traditional drive so watch out. Mecanums can climb decently though, so this is an advantage over a Holonomic.

This was my primary reason for wanting to explore Mecanum...but it seems as though swerve offers better performance if it works right

[=Martin=Taylor=]

In my six years of competing in FIRST I don't remember a single mecanum robot ever dominating a competition.

The powerhouse teams have built swerves, tank-drives, and more unusual designs like 71's shuffler and the 148/217 nonadrives. But I can't remember any of the top teams EVER using mecanum.

I can only think of a few cases in which a mecanum robot even won a competition.

Why is this?

Is it simply two difficult to write controllable code?
Are they just too inefficient?
Not enough lateral traction?
Or has the mecanum drive simply never been perfected?

I've seen those mecanum forklifts, I know what the technology is capable of...

[ttldomination]

Mecanum and Holonomic involve great loses of power that drives like Swerve tend to provide for you. But swerve drives require weight and a certain skill level. A lot of teams this year saw that they had the need for the maneuverability, but not necessarily the experience/resources for a swerve, and mecanums offered an easy solution.

[thefro526]

Originally Posted by Chris is me

Mecanum drives are overrated, heavily.

Darn, I don't think I can give you anymore rep for a while.

Originally Posted by Nick Lawrence

Another drive system you could research is a kicker drive system, also known as a slide drive system. It's basically a 4WD setup with omni wheels, with a fifth powered omni wheel mounted in the center of the chassis, that allows the robot to strafe.

We've never built one for FRC, but many for VRC. I'd love to prototype one that would be FRC-ready though.

-Nick

This is basically what the 148/217 drive is based on. I'd love to play with one at the FRC scale aswell.

Originally Posted by davidthefat

But you can strife with regular omni.

While this is true, a "Slide Drive" has a few advantages over a regular omni drive. Theoretically, it's easier to drive, and because you aren't always relying on the omni wheels slipping it'll have more pushing power.

[joek]

but, most tank drives use only 2 drive motors, whereas omni and mechanum ALWAYS use 4, so there is pore power being delivered, despite the 30% decrease, we have mechanum, and were able to push around tank drives like it was notheing

[Andrew Schreiber]

Originally Posted by ajlapp

This is the reason we wanted to introduce commercial swerve components to the market. There is always lots of discussion amongst the community about how to keep FIRST competitive....

I disagree with making the game easier or artificially leveling the playing field through other means.

I'd much rather see a large portion of teams building high quality robots by using off-the-shelf items when necessary to bolster an area of their team where they may not have the expertise.

That said, swerve is tough to pull off even if you start with pre-made transmissions. Cyber Blue is hosting a swerve discussion this week in Atlanta about the months they spent leading up to competition developing the technology.

The hard part is not the hardware. The devil is in the software. I admit, after 7 years of FRC and countless off season projects I am still intimidated by the thought of having to code a functional swerve drive during the build season.

Originally Posted by joek

but, most tank drives use only 2 drive motors, whereas omni and mechanum ALWAYS use 4, so there is pore power being delivered, despite the 30% decrease, we have mechanum, and were able to push around tank drives like it was notheing

What Tank Drive bots are you looking at? Ive seen some using 6 drive motors and most using 4.

[kevin.li.rit]

Originally Posted by joek

but, most tank drives use only 2 drive motors, whereas omni and mechanum ALWAYS use 4, so there is pore power being delivered, despite the 30% decrease, we have mechanum, and were able to push around tank drives like it was notheing

While I haven't seen any first omni robots using less than 4 wheels. There are omni-wheeled robots with 3 wheels. In the past we've considered using a 3 wheel setup.

[joek]

Originally Posted by Coffeeism

While I haven't seen any first omni robots using less than 4 wheels. There are omni-wheeled robots with 3 wheels. In the past we've considered using a 3 wheel setup.

i was talking about true omni drive, the holonomic kind

[dtengineering]

Wow! Did you ever get a lot of responses, quickly, on this one thread. You'd think you had posted a game hint for next year, or something!

But you asked two questions... one was:

"What should we build?"

and the other was "What does your team prefer?"

Those are two entirely different questions.

Frankly, I really don't think that the "What does your team prefer?" question is relevant to the choice that you have to make. First of all, very, VERY few teams or people posting here will have built and worked with BOTH mecanum and swerve drive systems. Many people will have SEEN both systems in action... and a few will have built and worked with both... but very few will be able to give you a first hand opinion on what they prefer.

What you need to consider is WHY you want to build a robot in the off season. Do you want to build it to work on design and machining skills? Do you want to improve programming skills? Do you just want to get first hand experience with at least one form of omni-directional drive? Do you want to have a cool demo robot? All of the above?

We have built a mecanum... but not a swerve. It was pretty easy to build... but took a bit of work to program (at least if you want 4 wheel PID speed control on an IFI control system... the cRio should make it a bit easier.) Unless you choose to build your own wheels, or develop a fancy suspension system, a mecanum drive is a very simple build challenge... particularly if you use a direct drive from either a Banebots or AM gearbox.

Outside of the discussions surrounding FRC competition robots... which are really kind of irrelevant to an off-season build project, the #1 advantage of a mecanum drive is that 99% of the people on this planet have no idea what a mecanum wheel is... and aside from a brief shot of a forklift on the recent Star Trek movie... have never seen one, either. Think about that... these wheels fit in a STAR TREK movie! Honestly, there is not much that is cooler from a teacher's viewpoint than watching a grade 10 explain to a P.Eng how your wheels work.

If you're looking for a bigger machining challenge, however, a swerve has all sorts of intricate parts that need to fit together just so. Sure, you can buy some COTS parts now to make that easier... but you are still working on a more mechanically complex system.

That is the reason we have avoided swerve up until now... we just don't have the manufacturing resources (mostly human resources... we've got the machines...) to confidently put together a good working swerve during build season. It would certainly be less daunting a task if we had built one as an off-season project.

But your team needs to think about why you want to build this thing... what you want it to be able to do... how much you want it to cost (in terms of money AND time invested in it) and then go with the machine that will make your team a better team.

Who knows... we might be back on regolith next year... maybe we'll have to climb stairs, or maybe the field will be made of corrugated iron. Or maybe wheels will be outlawed entirely.

Focus on the team, not the machine, and you can't go wrong.

Jason

[joek]

Originally Posted by Andrew Schreiber

The hard part is not the hardware. The devil is in the software. I admit, after 7 years of FRC and countless off season projects I am still intimidated by the thought of having to code a functional swerve drive during the build season.



What Tank Drive bots are you looking at? Ive seen some using 6 drive motors and most using 4.

then they must be using Fisher Price motors to drive, because we're only allowed 5 cims

[sdcantrell56]

Originally Posted by joek

then they must be using Fisher Price motors to drive, because we're only allowed 5 cims

We're using 8wd tank drive with 6 motors this year (4cims and 2 FP's)


Any team only using 2 cims in the drive this year is seriously hurting themselves