Quote:
Originally Posted by efoote868
To me, the beauty of AM's mecanum wheel is that it makes easy holonomic drivetrains available to low resource teams.
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I'm going to disagree with this notion because, as it's written, it's missing a key point.
(Keep reading after it, I do clarify it significantly.)
Quote:
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It makes BAD holonomic drivetrains available to low resource teams.
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You know, I can go out and buy a swerve module too? I'd make the exact same statement about a drive with them. Why? Because the hard part about holonomic/omni directional drive systems is they are hard to control. The mechanical aspects of things are hard (yes, even mecanum wheels) but building a reliable, tuned, and intuitive method of controlling them is HARD.
So, let's take team number 4xxx. They are your average semi experienced team. Some resources but not enough to build a second bot. Enough resources to build a solid manipulator and put it on a KOP drive train. Maybe even get a couple hours of driver practice.
Now imagine they put mecanum wheels on that KoP drive (because it's not hard. Costs about as much as adding shifters which is another system this logic CAN apply to). So, I've added some extra work beyond implementing simple skid steer drive. I guess I can use the WPILib's Mecanum implementation. But my robot turns as it strafes because my CG isn't perfect, what do I do? It's either something the driver has to get used to or it's something I have to invest more of my most limited resource (manpower) into fixing. So, now my manipulator has lost an iteration or small tweaks? For what gain?
Most teams don't think of problems this way. But they should.
Mecanum wheels are a solution to a problem. But they aren't as simple as slapping them on and using the WPILib Mecanum Drive class. That's a great way to build a crappy omni directional drivetrain. If you want it to be world class you need to develop and test a reliable and intuitive user interface. And you need to understand how it changes how you can interact with game objects and the field. It needs to be built into your greater strategy. And your driver needs to understand the limitations and benefits of your drive system.
Omni Directional drivetrains ARE inherently difficult. Nothing is ever going to make them easy to do. COTS parts simplify the mechanical issues with them. But the hard part is always going to be the UX.