pic: Hart District Robotics Swerve Drive Prototype

[AdamHeard]

I'm curious how the p60s will hold up cantilevered that like. We're overly cautious with them though.

The concept and gearing looks sound, can't really comment on the modules at all.

I think you could make the frame a lot easier for you by reducing the number of members by more than half. A lot of time goes into fabrication of such a frame, and also a lot of weight.

It looks like you could do just two main 3x1 rails (one per side), and lesser framing just connecting those. Would save a lot of time and weight. The frame for our Swerve drive is JUST a perimeter of 2x1x1/16".

What most people don't realize is the code is where you really make/break a crab drive. What have you guys accomplished there so far?

We used incremental encoders (s4's) for our steering, but have used MA3's in the past (as have a few other teams). I know other teams have used limitless potentiometers, and rotary hall effect sensors. Expect to pay $30 minimum for anything of quality.

[Aren Siekmeier]

Also, how are the p60s mounted? It looks like you need to take them apart and reassemble them around the box tube

[Clem1640]

We set up steering drive 1:1, so that steering drive angle provides an accurate proxy measurement for pivot driving angle.

We also used chains/sprockets and belts/pulleys to provide our gear reduction. Drawback is no gearshift (yet). On the positive side, we've got no formal gearbox.

1640 has been running pivot drive two years now. We are pretty satisfied with how it works for us.

The very devil is the control software. We spent a lot of quality time on developing this.

[AdamHeard]

Originally Posted by Clem1640

We set up steering drive 1:1, so that steering drive angle provides an accurate proxy measurement for pivot driving angle.

Gearing other than 1:1 doesn't have to sacrifice accuracy nor precision.

[Clem1640]

1:1 means that absolute angle measured on the steering drive corresponds to the absolute angle of the pivots. Other ratios require some sort of zeroing.

[AdamHeard]

Originally Posted by Clem1640

1:1 means that absolute angle measured on the steering drive corresponds to the absolute angle of the pivots. Other ratios require some sort of zeroing.

This is fact (but can be "fixed" pretty trivially). I just wanted to clarify to the uninformed reading that it's not an accuracy/precision issue, but a reference/zero issue.

[Clem1640]

Agreed.

[Garret]

I know someone asked for a picture of the module itself so I have attached one I took at today's meeting. Currently once we mount the encoders we should be running code. We plan on devoting the rest of our time to working on the code.

About running the steering at non 1:1 ratio, we did this because we could get AM parts that were cheap and were the right size for our shafts. I would run 1:1 but I am designing within my teams constraints.

I forgot to answer how we were going to measure wheel angle.
We plan on using an incremental encoder to determine our position relative to a zero position that would be set by a touch sensor or an optical sensor that would detect a reset/zero point defined by something along the lines of a reflector on the top of the module.

[Taylor]

reported