Re: which holonomic drivetrain do YOU think is the best any why???
 

point taken. the question and poll was meant to see what people thought the best drive train was in GENERAL. in other words, what drivetrain is the most adaptable to any situation? no system is going to be perfect and most teams will definatly realize the need to change strategies year after year. i also didn't want to limit this discussion in any way. i left it up to responders to give a situation and then give an opinion. FIRST is so dynamic that giving one specific situation is just as bad as giving none, no?

Re: which holonomic drivetrain do YOU think is the best any why???
 

please explain. i dont know what octocanum is. also tell us why u think it is the best

Re: which holonomic drivetrain do YOU think is the best any why???
 

Octo--8.
Canum--(me)canum.

8-wheeled mecanum drive (which is actually being done this year).

The other drive referenced: Nonadrive.
Nona--9. (For one of the teams using it, Neuna is an acceptable variation.)
Drive--self-explanatory.

Omni-drive setup with 4 wheels pointing in the same direction and a drop-down center one at 90* to the rest of them. The 4 are on pods such that traction wheels can drop down for extra power in a pushing war. Used by 148 and 217 this year.

Re: which holonomic drivetrain do YOU think is the best any why???
 

It's my play name for a drive very similar to the "nonadrive" deployed by 148 this year, but with only 8 wheels and 4 of them being mecanum instead of omni. See pg.4.

My post was more joking than anything, though. You should evaluate each drive within your strategy for each particular game. Each style of drive, wheel type, and variation will give you different advantages and disadvantages, and you need to see which of them are going to work best in your particular strategy.

Re: which holonomic drivetrain do YOU think is the best any why???
 

If you can pull off a field-centric, independent swerve drive, it's an amazing experience. It has a slight lag over mecanum wheels (the pods need a small amount of time to spin into position), but it's extremely agile, maneuverable, and depending on your choice of wheels and gearing, can out-push nearly anything.

But to do this, you'll need strong mechanical design, CNC manufacturing and software development resources, as well as a lot more time to develop and debug when compared to simple skid-steer 6WD. It will also take a big bite into your budget - both weight-wise and financial. And with the added quantity of components in the system comes the added chance that something will break.

Re: which holonomic drivetrain do YOU think is the best any why???
 

I love a well put together Mecanum system, but the fact of the matter is that nothing on this list can touch a simple, elegant 6WD (8WD this year) with a drop center. Just ask 1114, I haven't seen them deviate from this strategy for a great many years.

A crab can match it if done properly, but I bet a poorly rookie team could build a solid 6WD much more easily (in fact I know they can, just look at 2056's rookie robot http://www.chiefdelphi.com/media/photos/28599).

But if it is purely omnidirectional motion you are looking for, Mechanum is pure holonomic, and easy to build/maintain.

Re: which holonomic drivetrain do YOU think is the best any why???
 

Did you happen to see this picture posted during build season?

http://www.chiefdelphi.com/forums/sh...highlight=1708

Re: which holonomic drivetrain do YOU think is the best any why???
 

wow thats nice :O... do you have any follow up pics? or maybe some pics of the setup working during practice/testing?

Re: which holonomic drivetrain do YOU think is the best any why???
 

Not only did I see it, I was working in the pit right next to theirs during the DC regional. Unfortunately, 1708 had major issues all weekend, and never got to really show what their design could do at full potential. :(

Re: which holonomic drivetrain do YOU think is the best any why???
 

http://www.youtube.com/watch?v=cHJJQ0zNNOM


This

Re: which holonomic drivetrain do YOU think is the best any why???
 

Nonadrive, obviously. If you don't count that, I'm going to say 6wheelswervedrive takes the cake.

Re: which holonomic drivetrain do YOU think is the best any why???
 

Mecanum is pretty simple to build and program yet still produces good results. This made it the drive train of choice for many teams this year, including 1138.

However resources and difficulty aside, swerve definitely wins in speed and mobility as proven by 1717's amazing robot. :D

Re: which holonomic drivetrain do YOU think is the best any why???
 

I was more amazed by their hanging mechanism... Kinda looked like a machine gun sticking out of the robot

Re: which holonomic drivetrain do YOU think is the best any why???
 

After getting a tour through 217's practice bot tonight I am incredibly impressed by the Nonadrive.

Re: which holonomic drivetrain do YOU think is the best any why???
 

Given my druthers with all other constraints aside I'd go for 4-wheel, fully independent, continuous-turn swerve almost every time. a well-executed swerve beats most other pretty readily as far as widest applicability and best performance across the board. That said, there are other constraints, though they affect different teams and games in different ways.

Cost: A well-done pivot drive is almost always more expensive than mecanum or omni. In fact, if anyone's succeeded with a cheaper version, I'd love to talk. Pivot usually (though not always) requires milling, and of course more motors. After pivot, mecanum is usually more expensive than omnis, just by virtue of the wheels themselves.

Building/Wiring Difficulty: Everything's as difficult as you make it. That said, it's a lot "easier" to make a pivot drive complicated than an omni drive. That's not to say many teams don't make creative and effective omni, mecanum and other holonomic drives as well. However, from fabrication to wiring to programming, pivot drive is a tall order. I've never heard of a team with a successful pivot that didn't start examining the possibility in pre-season (then again, this is helpful for almost any type of success).

Programming: A pivot drive is certainly more complicated than a just simple tank, but how far you go with it is really up to you. We currently have crab, spin, x- and y-biased snake, x- and y-biased auto, and x- and y-biased tank (all with arbitrary fronts) at various levels of development. Depending on the game, a decent crab and/or snake can be more than enough to facilitate successful driving.

Traction: A good pivot works wonders here. Mecanum lacks in the area, as do omnis wherever they're used. (If you use omni front wheels and traction backs, you're pretty easy to push up front.) Perpendicular/angled wheels suffer here too, as you're effectively sliding the wheels' projection not along your movement vector.

Another novel idea: Last year, my team went with a 6wd wide configuration with a 7th deployable wheel in the back lowed to lift up the back 4 wheels. On the regolith, this allowed us to break more easily (transverse coefficient was greater than inline), spin quickly, and if we were lucky, move sideways. Of course, this all depends on the friction coefficients and their ratios, but suffice to say there are other options--notwithstanding nthdrive.

But if we're talking truly versatile, I've got one word: walking! ;)