After some research, I determined that Swerve wheels are very expensive. I am on a rookie team, and was wondering if you could put a single swerve system in the middle with 4 omni wheels on the perimeter? I’d imagine that would be much cheaper than a full swerve drivetrain with fairly similar functionality.
No. You loose so much traction and the ability to rotate.
Weight on unpowered wheels is bad, with one swerve module in the middle almost all the weight is on omni wheels and acceleration will be poor and defenders can push you around easily.
Yup! This is a good example of a “degrees of freedom” problem.
A robot needs to be controlled through three degrees of freedom: fwd/rev, left/right, and rotation.
A swerve module has only two degrees of freedom: rotate the module, and turn the module.
No matter how you mount or control the single module, you won’t be able to control all three degrees of freedom of the robot. Two modules could get you there though.
Also notable is how 3 points define a plane. So the more wheels you add, the harder it is for them all to have traction. What I’m trying to say is that mounting the powering wheel on the inside may be hard because unless designed correctly, it may not have enough contact with the ground, potentially caused by metal flexing or just design error. And then on the other hand you could have a tippy center, which sounds really weird to drive but might work?
Technically you could assuming the omni wheels were also powered. The swerve module would give you directional control and the powered omnis would give differential turning like a traditional skid steer (and power in the fwd/bwd). Is it effective…probably not. The omnis would reduce the normal force acting on the swerve wheel so you’d have less available force for side to side movement.
2 is still cheaper than 4-6, so I’ll see if my team can look into that for next season. Thank you.
If you can’t afford the cost of 4 full modules swerve isn’t worth considering. In running 2 modules, you loose some traction due to weight being on powered wheels. Frame design also becomes extremely weird.
A well driven 6wd or kitbot can get close to the performance in swerve most years. This year is a bit of an outlier where swerve is more dominant, but I highly doubt the GDC will keep on making swerve friendly games for very long. But look at any other year and 6wd can and does compete on the same level as swerve bots.
Take a look at 525 in 2016. IIRC, tank in the front, party mode swerve in the back.
Not quite the same thing, but interesting all the same.
If you are interested in just playing with holonomic drive base a 3 wheeled kiwi is far and away the cheapest. You can do some interesting things with traction and kiwi as well .
I’ll certainly look into a holonomic drive train for maneuverability (maybe a good off-season project?). It would definitely be cheaper.
148’s blue banners from 2008 have a different opinion. Several other teams concur with theirs.
2-wheel swerve… questionable. Once you hit 3 wheels, you’re going to do much better. 4 is preferred. 6? Insane…
Ok yes three wheel can work if done correctly, however, its not something most teams will be able to pull off correctly. For most games, you are making serious tradeoffs to run 3-wheel swerve that isn’t usually worth it.
What about… 5???
Depends if any Winnivation alums are involved.
Also depends if it works.
If you want to fool around with an ill-advised, sub-optimal drivetrain that gives you a lot of functionality of swerve but certainly not all of it, might I suggest octocanum?
You can, for the price of four mecanum and four regular wheels, four gearboxes, a few pneumatics, and a little ingenuity, create an easy-to-build, easy-to-drive, easyish to program, omnidirectional-and-fast-when-you-need-it-but-really-pushy-with-high-torque-when-you-want-it drivetrain. It’s fun to build, fun to show off, and isn’t anywhere even close to as finicky or difficult to work with as swerve–you run mecanum geared fast to zip around the field with high maneuverability, and if you get into a pushing match (or don’t want to be pushed) you fire one solenoid to pop down your four traction wheels (which are also geared down to traction-limited pushing torque) and suddenly you’re a tank drive with amazing push and almost no ability to turn.
We ran it for several of our most successful years before swerve was really a thing. It’s significantly less elegant and less efficient than a swerve drive, but only requires four (geared down) motors and four pneumatics plumbed to the same solenoid in order to have fast omnidirectional driving and fantastic beast-mode pushing power.
[That said, I think if you want to do swerve but it’s too expensive, save the money for a year or three and do that instead. A well-executed swerve is definitely superior to a well-executed octocanum drive, though also much harder to execute well. Whatever you do, make sure you’ve nailed it in the off-season before you try it during build season.]
I feel like a lot of people sleep on the kit bot, if you are a rookie team I would highly suggest against creating and driving a swerve since it is the most complicated to create and understand (esp in terms of programming). A kitbot will serve you well and also provide a test bed for future events and years. The last thing you want is your drive to crap out mid match and stretching yourself to make a complex drive when you could invest that time into mechanisms would be to your teams detriment.
I think a cheaper option would be something called H-Drive. It has a lot of downsides, but I think this is what your’re thinking of.
Would it be legal to make a robot with one center wheel like the one-wheel skateboard? To steer, you’d put down “hands” to drag the floor differentially…? Then all your traction would be on that one wheel.
You could also steer by leaning if you had the right shape of tire and a weight transfer mechanism.
Of course I’ve seen “ball” robots like BB8, but hard to put bumpers on that
I don’t believe there is anything illegal about it, it would certainly prove to make packaging of your mechanisms more difficult much like an h-drive would
I would chose X drive over H drive. One less motor, a lot easier to program. The main issue with X drive is that you sacrifice speed because each wheel is at 45 degrees to the primary translation directions. but if you gear it for a higher speed, it will be plenty fast.
Plus X drive seems to do better with the normal un-evenness of typical playing field surfaces and would certainly be a better choice if there is any ramps or sizable bumps on the field. H drives always seem to require a bit of tuning to give the center wheel enough contact with the ground to maintain grip and even with tuning and a sprung suspension, it is easy for that center wheel to loose contact with the floor if there is any sort of terrain.
I implore you to think about what you will do if a module breaks in competition. If you can only afford 2 modules, and you use both on your robot - you have no spares. If swerve is an absolute “must have” for you - I would invest my energy into fundraising to buy “full sets” rather than designing a 2 wheel swerve drive.
But if you want some real advice -
Swerve gets you from point A to point B a little more efficiently - but what about when you get there? For younger, less experienced teams - you’ll get more “bang for your buck” focusing on game piece acquisition, manipulation, and delivery than on moving a little more efficiently. Swerve is a last 5% sort of improvement. Focus on the first 95%.