Quote:
Originally Posted by 3175student17
My team has never used an omni drive train, but I do know a little bit about them. Please correct me, anyone, if I am incorrect in any of these statements, and I hope this can answer some questions.
Holonomic Drive: More prevalent in FTC, it uses 4 omni wheels with 2 sets of 2 perpendicular to one another. In theory, this drive should be able to drive in any direction, but my understanding of why this isn't used in FRC is because of a terrible lack of traction and difficult programming. |
You pretty much nailed them all. I just want to point out that "Holonomic drive" is sort of an incorrect name.
Holonomic just means that it is capable of moving in any direction, at any orientation. So there are many non-omni-wheel drivetrains that are holonomic (Swerve, octocanum, slide drive, nonadrive, and mechanum are all holonomic)
Though I do frequently see people use the term in the way you listed it. I've also heard it called "Kiwi drive", but some people only call it that when it's a three-wheel system (as opposed to four).
Back to the OP's original questions:
The system 624 is using in that video is known as Nonadrive, because it has nine wheels (Nona = prefix for nine). It switches back and forth between the five omniwheels and the four traction wheels.
148's 2010 robot also featured a Nonadrive (As far as I know they first invented it)
The advantage is that you can use the you can move omnidirectionally when in omni-mode, but, as you guessed, that leaves you open to being pushed around, because omniwheels offer very little traction. so when you get into a pushing match like that, you can switch over to the traction wheels for traction.
As 3175student17 mentioned, Nonadrive is not used very frequently because it has evolved into Octocanum (Four traction wheels, and four mechanum wheels).
Octocanum is used because it's simpler than Nonadrive; it requires one less set of wheels, and one less motor.
However the photo you posted, from the Vex forums, is a different kind of drvetrain, as 3175student17 also pointed out, that is usually called "Slide Drive". It gives you the same omnidirectional movement of Nonadrive, but you can't switch to traction mode if somebody is trying to push you. So yes, you will be very easy to "boss around" on the field.