pic: Cyber Blue Swerve Chassis - Rear View

[Chris Fultz]

Originally Posted by Mike Soukup

add some mechanical stops to the system.

We talked about this last night and are trying to determine where is the best place for hard stops. We did not find a place yet, but your comment reinforces the desire to have something in place.

Originally Posted by Mike Soukup

Can you share with everyone how you plan on using the data from both pots? We've contemplated adding redundancy in the past, but have never come up with an easy way to distinguish a good vs a bad pot so we always stick with one.

I will talk to our programming leaders and get a response. I don't know if they plan on averaging the input data or using one as a primary and one as a backup or something else totally different.

[IndySam]

Love the work. Are you going to have a demo time?

My question about the two globes and the redundancy: If one globe dies will the other have enough power two turn the modules and overcome the drag from the other globe?

[Chris Fultz]

Originally Posted by IndySam

Love the work. Are you going to have a demo time?

My question about the two globes and the redundancy: If one globe dies will the other have enough power two turn the modules and overcome the drag from the other globe?

Don't know about a demo - maybe something at the IUPUI kick-off?

As long as globe1 doesn' fail and actually lock-up, then yes, one will overcome the other. Last night we put power to just one motor at a time and it (quickly) rotated the modules. We expect we will have to really limit the power to the globes to be able to control the rotation.

[waialua359]

Originally Posted by Collin Fultz

Raul -

Thanks for your thoughts. We are building this now so that we may learn from those with more experience than us without the stress of a build season. Any other questions or criticisms are welcome.

//Edit//

This photo may show the Globe mounting a little better.

Collin,
Same here for us. We started during the summer, our swerve project which is an off-shoot of what 1983 Skunkworks created.
Our thoughts were to go through the grind now rather than during build season, in case we use it or not. At least you got options come Kickoff.

With so many teams developing something last season, the last thing we wanted to do was be 2 years behind, in case it would be beneficial to have such a drive system for the 2010 game.

Nice work and thanks for the better photo.

[ajlapp]

These units make the steering job easier, Wild Swerve Steering Module. Though they don't support two sprockets.

We expect we will have to really limit the power to the globes to be able to control the rotation.

In my discussions with Raul he has mentioned that they commonly run a 2.5:1 reduction from the globe to the module.

The chassis looks great by the way. We've thoroughly enjoyed working with Cyber Blue. Their work on the assembly instructions for this unit is very impressive; as is their dedication to educating the FIRST community.

Thank you.

[Dillon Carey]

How is the chain tensioned?

[Aren_Hill]

threaded standoff setups with the chain masterlinked to them, only works for these cause the modules cant go round and round like coaxial can.

[Chris Fultz]

Yes. The tensioners are basicaly turnbuckles, with a drilled and flattened end on the screw threads to accept one side of a master link.

We made a dense foam mounting board with four wheel sized slots cut into it so that we could set the chassis onto it for alignment. After the wheels were aligned, we set the chain tension (the tops of the modules have some adjustment) and then used the tensioners on the other side of the sprockets.

[Matt Goelz]

Originally Posted by Brandon Holley

Looks extremely slick, kudos to 221 LLC and Cyber Blue. What kind of weight are you guys looking at for that setup right there?

Brando

I actually just weighed our robot with another member last week due to curiosity. It weighed near 80 pounds. But that also includes our electronics. However, I don't recall whether or not the battery was on or off the robot at that time. The 80/20 chassis we put together was 18 and each pod is presumably 8 or 10 pounds each. So what you are looking at in the picture is about 60, give or take a few. Of course you can always make it a lot lighter in a number of ways.

[reversed_rocker]

Looks great, we had pretty much the same design for our competition bot last year. what's your sensor and driver station setup?

[reversed_rocker]

are both your front wheels and back wheels steerable?

[EricH]

Originally Posted by reversed_rocker

are both your front wheels and back wheels steerable?

Yes. If you follow the chain runs, the sides (where the turning motors are) have a run to the far end and a run to the near end. Then there is a run across the near end for redundancy. All four modules rotate together.

[Collin Fultz]

Originally Posted by reversed_rocker

Looks great, we had pretty much the same design for our competition bot last year. what's your sensor and driver station setup?

Thank you.

Currently, the only sensors are the potentiometers on the rear wheels which monitor angular position of the pods relative to the frame.

These units from Team 221 LLC do come with an easy way to mount an encoder on each wheel, should you choose to do that.

We are using a PS2-style game pad to drive with one "joystick" controlling the angular position of the wheels (powered by the globe motors) and the other controlling the speed of the wheels (powered by the CIMs)

Overall the design has worked very well for us, and we're thankful that Anthony and Team 221 LLC decided to partner with us for this project.

[reversed_rocker]

when we built our crab drive, one problem we had was that the motor would over shoot the intended position, then try to swing back, and the process repeats.

we multiplied the difference between the wheels position and the intended position (the value read from the controller, translated to the same value range as the wheel position) by a constant less than 1 (ours ended up being around .57, but this is something you can define at the top of your code and mess around with) this way your wheels slow down as they approach the intended destination.

how did you solve the problem? maybe we could trade some code

[Collin Fultz]

Originally Posted by reversed_rocker

when we built our crab drive, one problem we had was that the motor would over shoot the intended position, then try to swing back, and the process repeats.

I am not a programmer, but I will tell you how I think we solved the problem. I believe we measure the delta between the angle we want and the current angle of the wheel. While that angle is >15 degrees, the wheel rotates at full speed. Between 15 and 5 degrees, the wheel rotates at a lesser speed. Between 5 and 0 degrees, it rotates slower, still.

We didn't seem to have any problem with overshoot. The wheels seemed to do a good job of "snapping" to a position and holding there.

All that said, I will check with the Controls team Monday and confirm this.