Has anyone made a swerve drive that's run on one motor?

[techhelpbb]

Originally Posted by Munchskull

I belive the late team 1717 did just that in 2009, or at least that is what the new cool made it sound like.

Per this post:
http://www.chiefdelphi.com/forums/sh...1&postcount=34

Confirmed here:
http://www.chiefdelphi.com/forums/sh...&postcount=102

2000 hours for 5 mentors and 5 students is basically 2 6 week build seasons if you work around the clock.

Still a highly impressive effort and result.

Here is the evolution of their swerve steering over several years:
http://www.chiefdelphi.com/forums/sh...3&postcount=61

Even if it is 2000 man hours which could be 200 hours each for 10 people - they built variations for years so by the time they built 4 wheel independent steer they already had design, build and drive experience.

[sanddrag]

Originally Posted by techhelpbb

Can anyone provide examples of teams that jumped into swerves cold in a 6 week build season and fully exploited it?

696 in 2015. I don't know what you mean by "fully exploited" but it was fully programmed and functional to do whatever you want. It stacked all three totes in autonomous a few times too. Did we drive it to its fullest capacity? Maybe not. But we didn't have a practice bot either. Details at http://2015blog.team696.org

[techhelpbb]

Originally Posted by sanddrag

696 in 2015. I don't know what you mean by "fully exploited" but it was fully programmed and functional to do whatever you want. It stacked all three totes in autonomous a few times too. Did we drive it to its fullest capacity? Maybe not. But we didn't have a practice bot either. Details at http://2015blog.team696.org

That is very impressive!
You've got a unique swerve design in 6 weeks.

Do you normally build practice robots?
Or put another way:
Did making the swerve drive contribute to the decision not to make a practice robot?

I ask because on Day 4 of the build log at the link it is suggested that the build schedule was to give enough time to practice before bag and tag.

In Leadership, an important schedule was made by Jack, the president, on the due dates of manufacturing. This is an important step in planning out the rest of the season as we hope to have a few days of drive practice before the robot has to get wrapped up and tied.

It looks like from the build log that the drive train was operational by mid-February?
That did not leave much time to practice.

[sanddrag]

Originally Posted by techhelpbb

Did making the swerve drive contribute to the decision not to make a practice robot?

In part, yes.

[techhelpbb]

Originally Posted by sanddrag

In part, yes.

Your team made a very impressive practice bot in 2014, I found pictures of it.

So if the swerve drive contributed to the decision not to build a practice robot that would mean there was less opportunity to practice and the build was finished pretty close to bag and tag.

I guess the question that would raise, is the same that you've previously hinted at, did the swerve drive deliver sufficient advantage to the human operators or might the time and resources have been better directed at more simplistic drive train that the drivers could have had more quickly and perhaps had a practice robot as well?

Regardless it is an impressive achievement.

When we tried the swerve we also did not build a practice robot. We bought the modules but we weren't able to get the drive train until the last 3 days. Plus we could not afford enough modules to make a practice robot.

The first time we really drove was on the field. I have always speculated that if we had gotten it all together a little sooner and if we had sorted out the programming challenges a bit sooner: that we might have been more successful.

Instead the drivers literally got the short end of the stick. A hard to control robot they had very little experience with and it was hard to make it go straight. Plus that was the year with the opening you could drive through in the field separator. Imagine threading a needle blind with something unpredictable.

[AlexanderTheOK]

Originally Posted by techhelpbb

Agreed it gives you more degrees of freedom of control. Thing is you have to be able to control it.

Controls for a unicorn swerve aren't too complex. If your worry is the programming you can try what we did here and make one out of vex components first. Heck, you could go even further and make it coaxial using these to get it closer to the real thing.

Originally Posted by techhelpbb

I've thought this over quite a bit. As the OP mentions the cost of 4 CIM motors/speed controls to drive steering indepently is pretty high. 8 CIMs risks a good hunk of battery power in addition to driving weight. One could counter that you only use the steering CIMs when you steer but is that not the goal? Assuming one tames the power required or uses a smaller motor with sufficient gearing to steer to overcome this....

No need for cims on the steering. We used 550s on 696 and other than getting hot, there weren't many issues.

Originally Posted by techhelpbb

Is this really a mere 6 week task to gain a degree of freedom that as others have pointed out risks reducing your ability to drive straight?

You actually get the ability to drive ultra-straight, as with four wheels on the ground, it takes more force for them to scrub.

Originally Posted by techhelpbb

Can anyone provide examples of teams that jumped into swerves cold in a 6 week build season and fully exploited it? I am honestly curious my experience is limited to the northeast US. I would be very curious if they bought the modules or borrowed their code to make it work in that timeframe. I can accept it is possible but would like to understand the details.

As sanddrag already mentioned, 696 went in very much cold. While doing it another year and iterating would yield a better design, I don't believe we left out any "features", that is to say, the driver had 3 axes of freedom, the option to drive field or robot centric orientation, and autonomously moving to field centric "coordinates" or "waypoints" (x,y,theta) on the field.

The modules and code were done entirely in house.
I have to say that one of the greatest boons to timely functionality was the construction and programming of the "miniature" swerve. It let us get the math out of the way early so we could focus on individual control of modules.

[techhelpbb]

Originally Posted by AlexanderTheOK

The modules and code were done entirely in house.
I have to say that one of the greatest boons to timely functionality was the construction and programming of the "miniature" swerve. It let us get the math out of the way early so we could focus on individual control of modules.

That was a very good idea: we didn't have any access to resources to work on the code except the robot itself when we tried it. In retrospect I wonder if those parts were available 6-8 years ago.