With the new motor rules, we no longer have as strict a motor limit as before. Now that we can get up to 16 motors, using 6-8 small motors to build a swerve drive might be feasible. Any thoughts on this?
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So here is the challenge: A standard drive is 66W with various amounts of PTO, from occasionally 44W to up to 88W.
The simplest Swerve with 11W drive pods outputs 44W of drive and 22W of steering leaves 22W for mechanisms, but still has only 44W of drive, without linked all-wheel drive (which makes it harder to win pushing matches).
A more advanced swerve could run 4x (11+5.5) in each pod, for the equivalent of 66W of drive. Then you could have 2 5.5W motors run differential linkage systems for turning the pods and that’s 77W for the drive, leaving 1M for other mechanisms. 66W of a highly agile driving power, but mechanically complex, no linked AWD, and no simple PTO from your main drive system.
So while you could build it, we can look to VEXU for what is possible without the motor limit. Without custom engineering, it is going to be very hard to run any form of swerve that is viable.
However for us to really know its viability, we would need to see a well iterated and implemented example. If you want to build it, go for it. However the complexity is prohibitive without purchasing a well engineered and iterated upon swerve POD, which is how most of FRC achieves swerve.
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Adding on, the alternative to swerve in VRC is usually the x-drive. It can also move in all directions, and it would certainly out-perform a VRC swerve. This is why many VexU teams elect to use X-drives where more driving flexibility is required.
FRC uses swerve because of the almost limitless customization, along with the powerful BLDC motors, this is also why FRC teams do not use an X-drive, as swerve is the better, option in their circumstance.
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Thank you for the information. I am relatively new to robotics and I am trying to gain the knowledge to help with coaching. I knew that swerve required a minimum of 6-8 motors, but the power was an interesting point.
No problem! Remember the swerve (built most simply) would have 4 motors of driving power anyways, probably less than most of your opponents that would use a 6-motor, geared-together drivetrain.
Additionally, the greatest challenge with building swerve is just the parts you have available. If you take a look at FRC swerve designs (the SDS swerve modules being the most popular), you will see that it would be quite difficult to replicate that module robustly using Vex V5 building rules. If you tried building a VRC competition swerve, it is likely that the most unreliable, weakest, and frustrating part of the robot would be your drivebase - the most important part of your robot.
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For the most part, my goal is to give my students ideas and options that they can work through in designing their own robots. We do not as of yet have an FRC team (though that may or may not change). However, I did volunteer for them and learned quite a bit about the mechanics of robots.
So there are a LOT of great drivetrains that you can find digging around on youtube and the forums. Peak design in VRC tends to be an ultralight drivetrain with PTO or a shifting transmission. This game might not need ultra low range pushing, but it will need to power a climbing mechanism, and not at the same time as a strong drive, or your other mechanisms, so learning how to build pneumatically shifted mechanisms unlocks a lot of design potential.
That being said, just having a robust drivetrain that can drive over the middle while still being light enough to climb is a good start.
What do we think about a two-wheeled crab drive? 2 motors per wheel, 1 for rotation of both wheels, omnis to support everything. You get holonomic drive with full 4-motor pushing power and traction wheels. Rotation works fine with traction wheels because only 2 traction wheels. Difficult to build and program? Absolutely. Impractical? Probably. But maybe not so bad…
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