What type of drive train is the most maneuverable?

[efoote868]

Originally Posted by Veselin Kolev

...And they're arguably more complicated to program, needs sensors, etc....

Our programmers this year actually got the code down to 4 lines... and it was just converting joy numbers to good PWM values.... super efficient.

Most programmers that I've met actually say they're easier to program than a 4-wheel / 6 wheel tank drive, or at least the ones that have used them.
Only a very weird configuration would make it harder... like only using 3 wheels

As for making it go relative to the driver, thats where it becomes tricky (all that great vector math). Thats where we used the gyro, and thats how our robot messed up (preseason, the lead programmer then decided that it wasn't worth our time).

We also found out that a gyro is affected by temperature, pressure, etc. greatly; and that it gave out different readings at different times of the day oh well

[Lil' Lavery]

Originally Posted by efoote868

As for making it go relative to the driver, thats where it becomes tricky (all that great vector math).

How would vectors not apply for robot-centric control as well?

[Aaron D.]

I'm simple. I am a fan of the 4w tank drive, for several years we always went with a width ways orientation so we had a zero degress turning radius. but this last year we had a 4 wheel 2 spd tank that was long ways so to solve the manuverablility problem we implemented a pop-castor design that used a piston to push up the fron and turn on 2 castors and the rear wheels. It looks pretty sweet too!!!

[efoote868]

the vector math is easier, and actually is just converting joy input to PWM values (4 lines of code)...

In a stroke of brilliance one of our programmers got rid of all the vectors... and explained "To go left, turn these wheels forward, those ones backward. To go right, turn these wheels backward, those ones forward. To go forward, all wheels go forward, backwards the same. To spin, turn these 2 forward, these 2 backward, and vice-versa" (as he pointed to our diagram).

now (like all other drives) the driver is thinking in terms of the robot, so they're the ones "doing the math".
The robot isn't remembering where it is, so theres fewer vectors involved.

If the robot did remember where it was, the coding would become absolutely atrocious.

[KenWittlief]

Originally Posted by efoote868

...We also found out that a gyro is affected by temperature, pressure, etc. greatly; and that it gave out different readings at different times of the day ...

if that was true then your gyro was defective or there was a bug in your code reading the gryo value. Solid state gyros are highly reliable, the same AD chips used on the robots are used in cars for things like airbags and stability control (steering).

One thing about the gyros, they must be solidly mounted to the chassis of the robot. If the gyro can wiggle and vibrate (if you hold it down with tie wraps, or foam tape) you will get all sorts junk on the output signal.

To be useful the gyro chip must move exactly the same as the robot chassis moves.

[Jay TenBrink]

Our 2006 Martian robots were initially designed and built with the same knobby pneumatic skid steer drive train layout we had in 2003,4, and 5. This proved to be too unstable during turning because of the robots’ higher center of gravity. The diagonally placed omni wheels were installed very late in the build. Omni wheels are fine for maneuverability, but not good for resisting a lateral push.

If we had it to do over again, we would have had a drive train very similar to what 469 did this year (and what we did in 2001 on our first Martian robot). Las Gorillas had a skid steer with a set of deployable ball casters on the front right and left to lift the front of the robot off of the ground for maneuverability. When the casters were retracted, all four knobby pneumatic tires were on the ground for impressive pushing power and sideways stability against an aggressor.