potential future white paper: swerve drive implementation

[PAR_WIG1350]

Originally Posted by virtuald

Swerve Drive is really easy to implement if you ignore the actual control of the motors and just look at it abstractly (ie.. point motor to angle and run it at some speed). Of course, there are some optimizations you can do to ensure smoother operation past just the pure mathematical analysis.

I created a spreadsheet to simulate a swerve drive and its calculations (by using a graph to model the direction/speed of the wheels): http://www.virtualroadside.com/blog/...l-spreadsheet/

We also released the source code for our robot that year (which includes its swerve drive code), which can also be found elsewhere on my website.

Yes, but not really, for people who breeze through vector calculus like it was nothing, swerve drive is nothing (and this is swerve drive, not crab which is really easy to program), but some teams don't have any team members with higher level math skills. The idea of this paper is to provide an out of the box formula for any swerve drive base regardless of size, shape, or number of wheels. Also, it doesn't involve any calculus at all. in addition, mechanical and electrical implementation of swerve will also be discussed. Currently the paper is not very much more than a plan, but the idea of using tables and arrays for swerve drive is one of the planned topics of discussion, although how to do it is not.

[Nadav Zingerman]

Originally Posted by PAR_WIG1350

Yes, but not really, for people who breeze through vector calculus like it was nothing, swerve drive is nothing (and this is swerve drive, not crab which is really easy to program), but some teams don't have any team members with higher level math skills. The idea of this paper is to provide an out of the box formula for any swerve drive base regardless of size, shape, or number of wheels. Also, it doesn't involve any calculus at all. in addition, mechanical and electrical implementation of swerve will also be discussed. Currently the paper is not very much more than a plan, but the idea of using tables and arrays for swerve drive is one of the planned topics of discussion, although how to do it is not.

There is no calculus involved in that spreadsheet. If anyone really want to use an "out of the box" formula without really understanding it, all they have to do is translate the Excel formulas into code.

[brianc217]

My team tried to do a crab drive system this year but we found that the chassis would not maintain its orientation as we had assumed.
Does anyone know why this might have happened?

I tried implementing some correction code that would look at the gyro and compensate by speeding up one side or slowing down the other with some success but it wasn't perfect.

I also tried making sure all the wheels were going the same speed using rotation sensors and PID but could never get it to work. There was too much lag. Has anyone got this to work with this or a different method?

Thanks. I would appreciate any feedback. It would let me sleep easier at night!

[PAR_WIG1350]

wheel slippage, gyro drift, collisions and wheels that aren't centered in the modules can all contribute to changes orientation.

for more information, I would suggest starting a new thread for this specific topic

[apalrd]

You could let it happen, and provide a way to manually correct for it. Many things can cause you to turn, but if you can fix that, you will be good (plus, it might be handy to be able to line up by turning a little bit)

[PAR_WIG1350]

Just an update, I haven't forgotten about this, but since the inverse AND forward kinematics of swerve drive have already been posted in these papers in great detail, I plan on changing the topic of the paper to autonomous path planning with interdependently steered and driven wheels. I hope to get this up before kickoff by working on it in my free time, but lately I haven't had much.

Feedback or suggestions would be appreciated.