The Hardest Drive System To Program:

[mobilegamer999]

swerve drive == crab drive

and yes, putting all that stuff in (in summary) sounds simple, but seems complicated in comparison to say tank drive which is read left joystick set left wheels, read right joystick set right wheels

[davidthefat]

Originally Posted by mobilegamer999

swerve drive == crab drive

and yes, putting all that stuff in (in summary) sounds simple, but seems complicated in comparison to say tank drive which is read left joystick set left wheels, read right joystick set right wheels

So you are saying that the "hardest" drive system is not even that hard. (I am more than capable of programming that) Now I guess I will look into to legged locomotion instead of wheels...

Actually, I think a 2 wheel system would be fairly hard.

[rahilm]

Originally Posted by mobilegamer999

swerve drive == crab drive

and yes, putting all that stuff in (in summary) sounds simple, but seems complicated in comparison to say tank drive which is read left joystick set left wheels, read right joystick set right wheels

Crab is simply a TYPE of swerve drive, but they are not the same. Swerve is just the ability to have sets of wheels that can rotate. Crab drive is a type of swerve drive where all the wheels are linked (mechanically usually), so they are always at the same angle. There are other types of swerves, including ones where each wheel is rotated independently (allows greater maneuverability and less skidding and much more complicated programming), and Winnovation's 6-wheel swerve.

[David Doerr]

Ackermann steering was the hardest steering I've programmed, but also the most fun. If you're not familiar with it check it here: http://en.wikipedia.org/wiki/Ackermann_steering

The wheel steering angles aren't equal when turning because the wheel axles both have to point at the turning center point. With a hardware linkage, you're limited as to where your turning center can be located, but with a software "linkage" you can place the turning center wherever you like.

The HOT team used this in 2008 when I was a member of that team - a fitting drive and steering system for that year's theme. A separate control loop was used for each steerable wheel.

[Siri]

I'd say Unicorn drive is up there. There's so many modes available: tank (uncommon if snake works), full crab (all wheels pointed same direction), snake (front & back point opposite directions), center spin, arbitrary center spin, each potentially with x and y-orientation. The real trick is switching "modes" on the fly. Some have 2 speeds, either mechanical or software-based (less optimal but alright for some games/strategies).

We've been iterating 4-wheel swerve for 2 years (without tank mode). Heck of a ride. Go programmers!

The other possibility that comes to mind is Nonadrive. It's incredible, but I have no idea how complicated the programming is. (148, are you here?) Of course, there's always auto-balancing trackballs. Or triple-jointed six legged bots.

[davidthefat]

Originally Posted by Siri

there's always auto-balancing trackballs. Or triple-jointed six legged bots.

How legal would those be?


edit: I don't think the unicorn drive is hard per se, but it would be a pain to make it user friendly

[mobilegamer999]

I have helped many teams with base drive code and have encountered quite a few different drive types. The swerve drive that I worked with was 4 swerves, each with independent control, and I would say it was one of the more difficult ones to get working, fully functions, and non-wire-twisting.

Now, the code i have doesnt use PID loops, but rather 'manual' monitoring and speed adjustment of swerve modules based on current and target angles. That being said, had it not been in the heat of competition with the limited time for programming and annoyance of "its just code, whats so hard about it" (as im sure all programmers are used to), I would have taken the time to properly implement PID loops, correct stops, and more features. But what made it difficult and would make it similarly difficult in any build season is the tendency to get 'base functionality' working then add 'slightly more' over and over so you can get more testing done and get it more and more functional but have ugly and hard to manage code, instead of taking the time to properly write it with closed control loops after base functionality was working. The biggest issue was the time limitation we had on programming and had we had more time, maybe it might have been easier to work with.

[Ether]

Originally Posted by Siri

I'd say Unicorn drive is up there. There's so many modes available: tank (uncommon if snake works), full crab (all wheels pointed same direction), snake (front & back point opposite directions), center spin, arbitrary center spin, each potentially with x and y-orientation.

You left out the most interesting one: full 3-degree-of-freedom control, like a mecanum or omni.

Originally Posted by rahilm

There are other types of swerves, including ones where each wheel is rotated independently (allows greater maneuverability and less skidding and much more complicated programming)

A swerve with four-wheel independent steering and wheel speed control allows the vehicle to be programmed to behave much like a mecanum, but without the traction limitations.

The procedure for calculating the wheel speed and steering angle for each of the 4 wheels is presented here.

For those who like to have a deeper understanding, the derivation of those equations is given here.

[davidthefat]

I just realized why more teams don't do swerve: it is hard to do the actually mechanical fabrication than it is to code it. I am not sure if my team is capable of producing such a drive system. Most of the mechanical guys are seniors and are graduating. My mentor will not let me learn any mechanical skills because he deems me as a too valuable of a programmer to be welding and stuff.

The most "advanced" drive we can fabricate will probably be a mecanum drive, possibly an omni drive.

But, if there are any teams that are willing to invite me to help program something more advanced, I will be glad to do it. I really have our doubts for next year. Chances are, we will go with our 6 wheel again (which I loath)

[bladetech932]

Dont worry david i'm in the same boat as you. Our team doesn't have the manufacturing capabilities to do a swerve drive even though i could easily program it and make it easy to use. and I HATE THE 4-6 WHEEL TANK DRIVE

[NickE]

Originally Posted by davidthefat

What is the hardest drive system to program?

http://www.youtube.com/watch?v=vwFrCpYavt4

[Robby Unruh]

To me, drive programming isn't hard, it's just really time consuming. Having to write all those limits to make sure you don't go over 1.0 or under -1.0, yelling at your electrical team to hurry up and give you the jaguar channels because you forgot to write them down (I never did ), then having to write all the functions like goLeft, goRight, goForward, etc. All just a total brainhurt, and at the end of the day you probably will have carpal tunnel. Man, those were the days.

[WarpSpeed10]

I think this drive base would be the hardest to program. Just watch it as they kick it. It's beautiful. :')

http://www.youtube.com/watch?v=W1czBcnX1Ww

[davidthefat]

Originally Posted by NickE

http://www.youtube.com/watch?v=vwFrCpYavt4

I would totally be down to do that. *cough*JPL, accept my internship request*cough*

[Chris is me]

Programming a drive so that you CAN control all of its functions is easy.

Programming a swerve drive so that it's intuitive and easy to control those functions is not.