Swerve Drive

[Tristan Lall]

Originally Posted by Aren_Hill

I've used bevel gears 3 times in competition and have never had a problem with them, in the above pictured setup we only had issues with the utterly ridiculous chain runs.

Looks like you took extreme care to make sure they stayed aligned—the keyed profile on the quarter-inch plates is a fantastic way of implementing that. I often worry about the torsional rigidity in the modules we occasionally see posted here.

[Andrew Schreiber]

Originally Posted by JDNovak

As for crab vs swerve. The code to steer from straight through an arc to rotating around the center of the frame has taken years to perfect. Actually, we had the trig working on the Basic Stamp in 1999 but changed to look up tables through the PIC years. We finally got a better version of real time trig working last year. Crab, on the other hand, takes about 10 minutes to point all the wheels in the same direction and turn all the wheels the same speed.

This is interesting, I was under the impression that the STAMP did not have math libraries included whereas the PIC did. I know the programmer on 27 was very happy to have the math libraries on the PIC. Of course, not only is this a long time ago but it was also when I was much younger and wasn't really paying too close attention to him so I could be very much mistaken.

It does show how far the controllers in FRC have come though.

[JamesCH95]

Aren - how much did that swerve drive base weigh? I'm just curious.

[Joe Johnson]

Originally Posted by Andrew Schreiber

This is interesting, I was under the impression that the STAMP did not have math libraries included whereas the PIC did. I know the programmer on 27 was very happy to have the math libraries on the PIC. Of course, not only is this a long time ago but it was also when I was much younger and wasn't really paying too close attention to him so I could be very much mistaken.

It does show how far the controllers in FRC have come though.

To use the STAMP2 you had to get into the PBASIC Zen Mode. It was all unsigned 16 bit math and it tooks some discipline to keep from hosing yourself. I can recall pulling my hair out trying to count/balance/place the nested parens (which I eventually gave up on -- I memorized the evaluation order of operators and basically kept parens down to the absolute minimum - took some doing but it was a time and bug saver in the end)

As to being glad to see the STAMP2 in the rear view mirror? You bet. It was some much easier to do things like scale a joystick using signed math. Oh and the PIC chip was many many times faster, more memory for variables, more code space (remember program slots? Ugh! that was painful).

Joe J.

[Andrew Schreiber]

Originally Posted by Joe Johnson

To use the STAMP2 you had to get into the PBASIC Zen Mode. It was all unsigned 16 bit math and it tooks some discipline to keep from hosing yourself. I can recall pulling my hair out trying to count/balance/place the nested parens (which I eventually gave up on -- I memorized the evaluation order of operators and basically kept parens down to the absolute minimum - took some doing but it was a time and bug saver in the end)

As to being glad to see the STAMP2 in the rear view mirror? You bet. It was some much easier to do things like scale a joystick using signed math. Oh and the PIC chip was many many times faster, more memory for variables, more code space (remember program slots? Ugh! that was painful).

Joe J.

This makes me glad I only ever used the PIC based stuff.

[JamesCH95]

Originally Posted by Joe Johnson

To use the STAMP2 you had to get into the PBASIC Zen Mode. It was all unsigned 16 bit math and it tooks some discipline to keep from hosing yourself. I can recall pulling my hair out trying to count/balance/place the nested parens (which I eventually gave up on -- I memorized the evaluation order of operators and basically kept parens down to the absolute minimum - took some doing but it was a time and bug saver in the end)

As to being glad to see the STAMP2 in the rear view mirror? You bet. It was some much easier to do things like scale a joystick using signed math. Oh and the PIC chip was many many times faster, more memory for variables, more code space (remember program slots? Ugh! that was painful).

Joe J.

I recall when 95 did a swerve drive using the basic stamp in 2003. I soldered up a board to use a second stamp in parallel with the RC in order to speed up our processing time. It was a nightmare from what I recall.

[Aren_Hill]

Originally Posted by JamesCH95

Aren - how much did that swerve drive base weigh? I'm just curious.

Never got a weight on just the chassis, but my estimates put it around 45lbs.
Currently rebuilding the practice chassis into a 4wd completely independent swerve for controls development, so I can probably get a weight on that later this week.

I've got a few new concepts in mind that would bring an 8 motor swerve down to 30-35lbs

[Chris Fultz]

http://www.chiefdelphi.com/media/papers/2378

http://www.chiefdelphi.com/media/papers/2381

Here is a paper and presentation from a few years ago that you can review.