Our team is planning on having a holonomic drivetrain this year in sky rise… but there are soo many different ways to do. This thread is for brainstorming about all the different types of omni-directional drivetrains and which ones are the best.
Do a search for Cody’s thread on Holonomic Drives. That thread has more about the drive system than you will ever want to know. Plus it has the best C code evolution. So you can start out with the “anyone can understand how this works” to the highly optimized version (almost fits in a single Tweet)
As far as all of the types there is only one, four omni-wheels mounted 90 degrees around the base. Equidistant wheels work best.
I did build and program a Tri-Holo ™, but it underperformed as a drive and was pretty tippy. (Think Reliant Robin from England).
There are some teams that have done Mechanum in the four corners and then Omni’s on the side, YMWV.
My team is planning either an x drive with the little omni wheels, or a mecanum setup. We’ve never done an x drive, but know that it’s just as good if not better than mecanum. We’ve had really good experiences with mecanum, but they take up a lot of room.
Any tips or good examples on setting up an x drive would be awesome.
Thank You.
I thought our team would just build an x-drive, but after I looked at all the different ways to do so I was like 0.o! Plus our team isn’t shure if we will do a scissor lift or an elevator.:eek: #soomanychoices
You had posted a poll with these terms
*X-drive *- aka an Holonomic drive (so lets use the right term)
Plus-drive - no idea what this is.
*Mecanums *- aka a mecanum drive.
Three wheeled triangle (I don’t know what to call it) - its a Tri-omni
*Four omni-wheeled tank drive chassis with one or two sideways omni wheels (I don’t know what to call that one either) *- So there are a ton of these variations, the four corner wheels do not need to be omni, and the 5th or 6th wheels can be at the edges or the center of the robot. https://vexforum.com/gallery/showimage.php?i=4176 is one example.
Sorry I thought I have seen X-drives where there was a wheel on each side and not on each corner. I must be wrong ;_;
Ummm, so if you turn the robot 45 degrees do they look the same? If so then it’s just the perception of where “front” is.
Yeah. Sorry about that. Excuuse mI dumbnnuss! LOL!
The problem with a lot of these designs is that they are too intrusive to the intake area of the robot. The cubes are 8" all around, which makes it really hard to allocate enough space for them when on either side there are wide mecanum wheels or omnis facing inwards. From a purely getting-everything-to-fit-together-nicely standpoint, H-drive would be the best option
I have thought about that also. With an x-dive it is hard to find enough space to mount a lot of different lifts.
I’ll bite, what is an H-drive? I know what an H-chassis is. H-Bridge is how the motors are driven. My Google skills failed me, can you help me out?
http://www.team323z.com/uploads/1/0/0/6/10062475/2341353_orig.png
I love H-Drives. We might use one this year, but we will see.
I’m not sure but I think 323z may be building a H drive since their last one was really good. Also does anyone have a cad of a double reverse four bar or a video?
Examples for Foster…
X-Drive - 81 Gambit or KTOR in Roundup, or an early version of 81M in Toss Up (no sure you saw that one). Look at the Wingus & Dingus robot from NZ in Toss Up too. It’s the 45 degree offset in the corners like you thought. 44 had a variation one year with wheels that maneuvered and locked themselves into place too which is an engineering marvel.
Plus drive - 81M Mystique in Sack Attack. Not much place for a lift or grabber when you’re done. The 45 degrees in the corners cut down on the center opening space which is its trade off.
Any of these holonomics need to be balanced weight wise to keep all four wheels on the floor. Otherwise you get some wheel spin and undesired results.
These are referred to as Kiwi drives. Not likely to be a good choice on an 18" wide platform when the robot will be as tall as 60" while scoring. If you use this design you might consider naming your robot Timber… They are also a bit trickier than X drives to program due to the mixing of channels involved.
Good!.. so I’m not crazy thanks. After hearing people give their opinion about it I think our team is leaning toward a h-drive more than anything…but I don’t know there are a lot of pros and cons to consider.
I plan using mechanems because I think the only time I will be strafing will be when I am aligning with the posts so strafing just has to be a capability.
since there seems to be a good amount of interest about reverse bars, I think I might post a reveal about my exploits in that area in the next few weeks if I can find the pictures/videos. (it was way back in gateway)
But here is 5327Bs reverse four bar robot:
https://www.youtube.com/watch?v=Y9OP9O4CClY
My favorite is projext drive
followed by the shifting X drive, or morpheus drive, as I’ve heard on rare occasions. It’s a drive which can shift from holonomic and tank as desired.
https://www.youtube.com/watch?v=KtsbIVxHNb8
https://www.youtube.com/watch?v=VpcXp7TV_FA
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@rougherbot here is a thread with a picture of a double reverse 4-bar