pic: Hart District Robotics Swerve Drive Prototype

[Isaac501]

Not a whole lot keeping those chains on the big drive sprockets, and the drive chain in the upper part of the picture looks pretty loose.

You may want to consider a tensioning system of some sort for it. Transferring any sort of power through that chain is going to make it fly off.

Other than that, looks really neat.

[Alan Anderson]

Originally Posted by Isaac501

Not a whole lot keeping those chains on the big drive sprockets, and the drive chain in the upper part of the picture looks pretty loose.

I don't know what you're looking at. I see 180+ degrees of chain wrap on the visible sprockets, and it looks like nearly that much on the obscured gearbox output sprockets.

You may want to consider a tensioning system of some sort for it.

Are we talking about the same picture? In the one I see, the long chain runs do have tensioning sprockets.

[Gdeaver]

I notice that it uses the banesbot transmissions for steering. They are not 1 to 1 on the chain drive. How are you measuring wheel angle?

[Garret]

We plan on measuring wheel angle with encoders or potentiometers mounted coaxially above the banebots gearbox output shaft. We don't have those encoder mounts on the robot in this picture.

[Alex.q]

Originally Posted by Garret

We plan on measuring wheel angle with encoders or potentiometers mounted coaxially above the banebots gearbox output shaft. We don't have those encoder mounts on the robot in this picture.

If you have a picture of the module itself, I would like to see it.

With respect to measuring wheel angle, I just want to warn you to make sure you buy a high quality sensor for this. My team learned this the hard way.

[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.