4080 Teaser/Reveal

:wink: Got it!

This sounds interesting. Mecanums are almost twice the weight of Omnis, so I thought they should help lower CoG? What issue did you have with them?

Thanks, Paul

When we picked up 5 or more sacks in autonomous mode it would shift enough weight forward to make the rear wheels lose traction and the robot would twist sideways instead of continuing forward while picking up the rest of the sacks. Since we were just day’s from leaving for worlds we ditched the mecanums since we didn’t have the time to address the root cause of the malfunction. We might have been able to use some ballast to correct the problem, but it was Saturday afternoon when we were finishing our autonomous program and we had to leave Monday morning to get to Anaheim. The problem could have been corrected if we had found it sooner, but we were all toast by this point.

The solution to that would have been better autonomous programming. :stuck_out_tongue:
No matter what kind of wheel you’re using, if you don’t accelerate properly, you’re going to end up messing up in some way. Take a look at PID. Looks like you just needed some more D.

The only advantage we have found with mecanums over X-drive is the ease of build and the use of standard chassis shape. Other than that, we think that X-drive exceeds Mecanum in almost every way, including performance, ability to strafe as quickly as it goes forward/backward, and ease to perfect (mecanums are finicky with weight distribution and have a tendency to strafe in a rainbow-shaped pattern). X-drive also has an easier time with the bump, as mecanums cannot strafe over it, but X-drive can.

You should look into inflating those large balls some more.

Got the wiring done tonight and did a little driving practice. I guess we got the COG right, even with the lift at 42" we could not tip it even trying :slight_smile:

All that is needed now is a few sensors and we will be done with the exception of a little tweaking here and there. Below is a picture of the messy wiring the judges always complain about :wink:

http://sbdrobotics.com/wp-content/uploads/2013/06/wiring-e1371524329765.jpg

We have our intake (bucky storage) designed so any ball dropped on top of the robot goes into the intake. This way if we can score in one goal during autonomous we should be the closest to the other goal frequently. We can move quickly to the second goal and park, our alliance can just dump their bucky’s on top of our robot and we can then raise up 24" and score. This will help with the crowded shoving matches.

What’re you scoring in Autonomous with your current routine?

We have a total of 8 autonomous modes we are working on (2 for each starting position). Since most teams seem to be going for knocking the large balls off of the 12" bars we will be attempting to score 3 bucky’s in a 24" goal. We will then move towards the other goal if there is time. Since it appears at least early in the season that most robots will still be in the middle zone we will then move to block the other goal at the start of driver control. We will stay in front of the other goal until our alliance gets close enough to take our place and score, otherwise they can unload onto our robot and we can score. The second autonomous will knock the 2 large balls into the goal zone and then just get as close to one of the 24" goals as possible to score.

We are still about 3 weeks from having a full field so our autonomous strategy may change based on what we can actually do in 15 seconds.

Have you tried the chassis with a bump? It took some tweaking to get mine to drive over properly…

We will be setting the rubber mats and bump up tomorrow, we have the mat’s in storage and our wood floors are too slick to test with. It has no problems pushing a toolbox across our work table and we took the angle of the bump into account when we designed the drive. The wheels make contact with the bump before the base of the chassis touches it.

Is your chassis elevated enough to clear the bump once your front wheels have gone over it?

Yes, if you noticed in the pictures we have 2-1/2" clearance side to side. We have to cross the bump sideways, but with this being an X drive it moves sideways just well as it does forward or backwards.

Says you. We’re going to build a bunch of drives to play with. We’re pulling off 2:1 without a problem right now. Once I get my hands on the new sprocket kits we ordered, I’ll see how fast we can go.

Yes it goes over the bump with no problem. It was designed to go over sideways, but also goes over forward and backwards as long as we don’t go over it too slow.

http://sbdrobotics.com/wp-content/uploads/2013/06/bump1-e1371592997896.jpg

We did some prototyping of drive bases a few days ago. 1:3 for speed with the 2.75" wheels is fantastically fast. It isn’t too fast necessarily, because with our planned 8-motor drive and some extra weight we were able to push heavy objects for a long time without stalling. Not sure what it would look like with the 4" wheels yet though.

We also have our high hanging taken care of. We can hang high with a ball with our wheels at 24-1/2" above the floor. Our latching mechanism keeps the base up with the power off. We were able to latch the base without motors or pneumatics!

Here’s a teaser of our scissor lift.

http://sbdrobotics.com/wp-content/uploads/2013/06/photo-e1371676709294.jpg

Do you mind showing the locking mechanism? I totally understand if you don’t. Just wondering!