Minibot deployment

[kstl99]

I see many threads about minibots but not about deploying them. Who has the best deployment system? The fastest? Most reliable? How do they do it?

Yes, I am trying to get ideas before our next regional but I think many teams could use help with this. We are considering an arm that swings out, a scissor mechanism or a slide along with other ideas. What has been most successful?

[NOV8R]

KISS is alive and well for minibot deployment. Here's a video of our (3729) drawer slide deployment tray doing it's thing. As you can see the minibot is held on the tray with vertical 5/16 inch pins that engage 3/8 inch tubes on the minibot. As you can see the complete deployment and climb take about 2 secs.


http://www.facebook.com/video/video.php?v=1840638666659

[LLogan]

We're using 80/20 on linear bearings pulled back with surgical tubing. It's released by a servo.

Consider using some sort of self-centering "V" or a deployment that deploys rails prior to actually releasing the minibot (check 148 and 1676.)

[billbo911]

We, too, are using a drawer slide type deployment system. Ours is actually comprised of a set used for a server piggy-backed to a set of Igus rails.
It is driven by a single .75in dia. 10in stroke piston. We use a set of pulleys to get the full 27.5 inches of travel. It is extremely reliable.

The minibot sits on a cleat and has a bolt that drops into a slot in the back plate. The minibot climb rate is around 4.5 seconds, not smokin' fast, but it gets the job done. More speed will come with the version 2 robot we are taking to Nationals.

http://www.youtube.com/watch?v=AVx7oFAyfjg

[kstl99]

Thanks for the replys. Looks like we will be going with a scissor mechanism, partly due to space constraints. It will be relatively simple, light and strong. We will have a V to help alignment. It will be interesting to see how it works.

[Grim Tuesday]

If your interested, the trick with drawer slide types is to, instead of using one long cylinder, use two a fire them simultaneously.

[cgmv123]

MRI slides, surgical tubing, self-correcting Lazy Susan table and plate. Deployment time: .5 seconds. See here:http://www.flickr.com/photos/johnvra...7625630416689/

[philso]

My boys (an award winning FLL team) were asked to build a MiniBot for one of the FRC teams in Houston. We tried several different configurations before coming up with a MiniBot that reliably does the climb in 2.5 seconds. It took a lot of work to install the deployment system on the Hostbot since we could not get any drawings for the it ahead of time. Unfortunately, our Minibot was never deployed successfully in competition.

We found that you need to look at deployment holistically. The Hostbot must be able to get the MiniBot to the pole accurately and reliably. The wobbling of the arm holding the MiniBot while the Hostbot is moving forward makes this more difficult. We also observed instances where the Hostbot drove forward too hard and bounced back, pulling the MiniBot off the pole. The pressure of being in a competitive match may have made a difference in how smooth the robot was driven. A system that does not require the Hostbot to move probably would have worked better.

http://www.youtube.com/watch?v=ibi8ZqC_LXI


A sight (pink pool noodle) was added to the Hostbot to allow the driver to better line up with the pole. This sight only works with the Hostbot in a line between the driver and the pole. Many of the attempts to deploy in competition were unsuccessful since the MiniBot was mis-aligned. One time, it was mis-aligned enough that it was damaged when the Hostbot drove forward and smashed it into the pole.

http://www.youtube.com/watch?v=10MxQCTuAQ0


Also, one has to consider other factors such as shown below. A bit of extra code probably would have prevented this mishap. My boys broke down and cried when they saw this happen, for the second time...

http://www.youtube.com/watch?v=Piq4VSKoy54


We hope others will be able to get some benefit from our experiences.

Phil

[Dad1279]

IMHO the key is in the alignment, and being ready to deploy ahead of time. We used a piece of 8020 with a slide, and a lexan 'V' at the end, so we could align with the pole prior to the 10 second endgame, and be ready to deploy.

Other successful methods included arms that swung out to hit the pole, so they were self aligning.

[notmattlythgoe]

We used a pneumatic scissor system on our robot this year for deployment. This past weekend at Pamletto we successfully deployed 16 of 16 minibots.

[jvriezen]

I may be biased based on what we did, but from what I've seen, for speed and reliability, the best approaches include one or more of the following:

1) Some type of alignment that uses the tower base as a reference (e.g. a fold down plate with a tower base radius matching cutout) This is not essential however, if item (3) is done well. (This is the only item in this list we did not do, but still had pretty good deployment success.)

2) A center mounted slide mechanism, pre-loaded with surgical tubing, and released with pneumatics or servo. We used two drawer slides and one igus slide, with two stages of tubing. Be sure to keep safety in mind -- we put a safety strap (removed just after placing the bot on the field) and also had a red danger flag that we put on the robot when transporting it to help keep people from walking too close behind. For the longer drawer slides, we looped the tubing back and forth to have a greater overall length. In other words, it works better if the tubing goes from 30" to 10" in deployment rather than from 12" to 2".

3) A pivoting V/funnel plate that will help with finer alignment. Ours was integrated with the surgical tubing slider mechanism so that the same laterally mounted surg tubes kept the V centered (until the pole persuaded it otherwise) and also provided slider thrust when released. The plate cutout had a shallow V, but at the vertex of the V, we cut back a rectangular slot, a bit wider than the pole, so that the last bit of travel was straight in line with MB, avoiding an angled approach of the minibot. That's the 'funnel' part of the plate.

4) Minibot mounted with tube/pin interface (at least 2). Probably doesn't matter which bot (HB or MB) has tube and which has pins.

5) Locking pin to prevent MB movement prior to deploy. We used a horizontal pin that went thru a hole in the mounting tube and vertical pin which held MB in place. It had some friction fit, so that it wouldn't jostle loose. The horizontal pin was attached by a string so that the pin would be pulled out just prior to MB reaching the pole. Just gather up the slack in the string with a loosely fastened zip tie so that the string doesn't get caught in something during the match.

5) Turn on power to MB before it reaches pole -- we used a simple string with a loop on the end to pull a standard wall switch on the MB.

6) Software control that releases the MB only when two things are true: a) Driver is pressing deploy button b) Match clock reads <= 10 seconds. Some have told us (b) was risky, as the internal cRio match clock might not be synced exactly with field clock, but we were never called for early deploy.
You mileage may vary. This way we lined up, held the deploy button and as soon as clock hit 10, it goes.


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Other good ideas involve a two step deployment, where alignment and contact with the pole happens prior to 10sec, and then the MB rides a rail out the pole at 10sec mark. But this seems more complex and takes more time if you are late to the tower due to being defended.


John Vriezen
Team 2530 "Inconceivable"
Mentor, Drive Coach, Inspector