Differential Swerve Test (1/27/23)

[@mro9629]

Fire 🔥🔥🔥🔥🔥

[@glowytheglowbug]

interesting build

[@illumi1749]

i have no clue what that thing is suppost to be yet it s so cool

[@cojames1514]

Swerve-drive is an omnidirectional drive-train in which all wheels are independently steered and driven. This allows the robot to go in every direction without looking at the direction

[@pepperypeppers2755]

That only answers half the question. Normally a swerve drive uses 1 motor to steer and 1 motor to drive per wheel. A differential swerve uses both motors to drive, and fancy gearing to turn when those motors drive at different speeds. More complex, but twice as powerful! Notably these will not be legal in the 2024 season due to the 4 drive motor limit. They may not ever be legal again.

[@dhruvbose8294]

It sounds like it wants to be put out of its misery jeez

[@Maxb0tbeep]

woah 3 wheels. thats interesting. does first allow this?

[@muffinmeister4528]

This is not allowed in FRC as teams are allowed a maximum of 4 motors propelling the robot and differential swerve, even with three wheels would have 6 motors. As far as I know, this is legal in FTC but it may be difficult to implement. I'm sure that there was a significant development effort that went into this drivetrain.

[@kirtrex]

14343 escape velocity is currently running 2 wheel diffy, and 14779 spontaneous construction ran 4 wheel last year. It's difficult to implement, and in FTC, differential swerve is way worse than coaxial swerve because module rotation can be driven by a servo. The traction issues and torque issues of a diffy swerve really aren't worth it imo. I would not recommend any swerve to any team lmao.

[@Maxx400x]

This robot is for the VEXU college level competition. The three-wheel design is actually totally unrelated to the fact that its a differential swerve (the triangle shape was important for some of our strategy considerations for the 2022-2023 VEXU game). We spent a ton of effort developing differential swerve because VEX/VEXU have much more restrictive actuator limits than FRC (i.e. putting motors on steering is super unrealistic). We typically max out our motor/sensor limit every year, so adding three or four motors for steering is a no-go. This video is from last season's robot, and these modules had a lot of efficiency issues from friction. Our new modules are much more effective, but that does put total development time at around 18 months (including breaks, and totally different design attempts). A big motivation for using differential swerve was to implement fancy motion planning / trajectory generation algorithms (i.e. Model Predictive Control) as a research project. For a purely competition focused team, the amount of effort to get differential swerve competitively viable is not a good use of time lol.

[@itsvoid2917]

Can i get some more information on the electronics? This seems very interesting, I never thought v5 motors could be used outside the brain? What is this bot for?

[@space8028]

that seems like black board is naked brain actually

[@itsvoid2917]

@@space8028 yeah I observed that

[@itsvoid2917]

He also has a 3000mah cortex battery

[@Maxx400x]

Hi, sorry for the delay. This is a VEXU robot from GHOST at UT Austin from the 2022-2023 competition season and an R&D robot for developing motion planning algorithms for Differential Swerve drives. There is a V5 Brain on this robot that interfaces the way you would expect. The black board is an Nvidia Jetson Nano (sort of like a raspberry pi). We do all our high-level programming on the Nano and send motor commands and receive encoder data through a microUSB cable connected to the VEX Brain. This makes it easier to interface with non-VEX Sensors, record data, simulate and test code, etc.

[@idk-ot5nb]

Knew VEXU had less strict rules, never knew you could genuinely use what is essentially a rasberry pi as part of your electronicsc​@Maxx400x

[@barknvar3902]

Is the cad file public?

[@Maxx400x]

We will release CAD for the new version sometime in the late spring. I'm happy to chat anything about swerve and show pictures of CAD publicly, but the current swerve CAD is coupled with the rest of our robot CAD for this season so I haven't had time to make a public release. Curious people can reach out to me on Discord at maxx3164 (preferable), or at [e-mail] and I'll pretty much tell/show whatever you like :).

[@rameensarwar3500]

8 motor drive?????

[@glowytheglowbug]

3*

[@Maxx400x]

It is 8 motor drive despite the three wheels. You have to have come multiple of two per module for a differential swerve to work. We double up the back wheel with four motors because we wanted a triangle chassis for specific strategy reasons and 8m drive is the norm for the VEXU competition. We run four-wheel swerve for the new season.