2.007: A Carnival Journey
And here’s my completed 2.007 Robot minutes before I sent it off to impound.
But how did it came to be!? I’ll try my best to recount the events of designing and what went through my head…
The 2.007 game this year is carnival themed.
Here is MIT’s article this year http://web.mit.edu/newsoffice/2012/2007-robotics-competition-0511.html
I’ve always done robotics competition with a group or at least with another person. This is the first time I’ll be designing, manufacturing and assembling the entire robot.
Tasks include: pressing a button to grab a ticket, blowing up a balloon, hitting the high striker and spinning the ferris wheel.
Here’s the point distribution:
Pressing+Grabbing ticket: 1pt for every ticket
Blowing up a balloon: 2pts/Liter
HighStriker - Max of 25pts for ringing the bell. Otherwise it is 10pts, 5ts, 3pts or 1 pt depending on where the slug ends.
Ferris Wheel- Score multiplier. (Max of x3 to current score. Depending on net angular displacement)
Finally, there’s a 30 second autonomous period where any points you earn in this period is bonus excluding the multiplier.
As a veteran in robotics competitions, I immediately knew that I will be aiming for the most yield in points as well as do the multiplier. Naturally, I selected the High Striker and the Ferris Wheel tasks.
To approach the high striker problem, I wanted to keep it as simple as possible. I thought doing a vertical hammer for the challenge was probably the simplest way to do the task.
I didn’t know how my robot would look like, and I wanted to keep the option of doing other tasks a possibility. So I wanted to save space as much as possible. A vertical hammer conserves space in the x-y plane in exchange for occupying the z-plane primarily.
It seems I’ve been out of touch with CAD during the beginning of the semester because I could not create anything substantially interesting, creative, or something that looks like it can do the task.
This was version 1 of the Pile Driver:
I thought that I didn’t really have to use strings, so maybe I can just use a 4-bar linkage instead?
I tried making this in lab with just calipers and a drill press. I didn’t get to take a picture of it because I was trying to get back into manufacturing mode. It’s been almost a year since I last used a drill press. >.<
To say the least, version 1.0 was a complete failure. The vertical displacement of the arm doesn’t even go that high! Plus, if I were to make the arm longer, I will be occupying more space than needed. If I did try to go for this design, I will be occupying space in all 3 directions. My complete reason for doing a vertical hammer will be trashed.
I felt very rusty. So I tried to attempt the problem again.
This was version 2.0
I still felt rusty with my CAD, and I couldn’t understand why I couldn’t design anything properly. I wasn’t happy with version 2.0 either. The structure is blocky with weak structural supports. It’s like all my engineering experiences have suddenly disappeared in the first few weeks of the class. wtf right?
It’s better, but it could be so much more… I just didn’t know what I was lacking. Anyway, it’s about 5 weeks into the class already and my progress has been extremely slow. I needed to have something built by the next lab section. Being sick, loaded with other classes, and “losing” my CAD ability left no time for me to change this design for the class’s milestone. So I just had to build it for the next meeting, get a grade and just scrap it when I have time.
There. I built it half-willingly. The structural supports aren’t even there. There were so many problems with this build that I wanted to scrap it as soon as it came to be. Don’t get me wrong, the sliders worked fine… but I approached the problem incorrectly.
Instead of building the structures before the sliders, I built the sliders and tried to constraint the structure. BAD MOVE. There was no way to salvage this build. Since I’m scrapping it anyway, I might as well just trash the design.
So… on to version 3.0.
What now? I had 2 tries so far and they’ve failed miserably to my own expectations. It was difficult to desire high precision holes and work with band saws and drill presses. Robotics needs precision and unless I only use the lathes, mills, the waterjet or a 3D printer, I’ll have a hard time gaining the precision that I want.
I thought to myself that maybe I should just stick to designing everything in CAD. And for that matter, maybe I should just stick to a standerdized way of building things…
What better reason is there to abuse the water jet machine?
So Version 3.0 had that in mind…. But again, my CADding ability is still not with me.
Here’s what version 3.0 looked like:
Where is my CAD MOJO!?? As I made version 3.0, I realized I was using almost all of my aluminum sheets. This is not desirable if I want to create the rest of my robot with the abrasive water jet.
Again, I did not like my 3rd design iteration. But I wasn’t going to give up. I was increasingly getting frustrated because it’s already spring break, and I don’t have anything useful….
And then i tried to do it for the 4th time:
I thought I hit the jackpot. The design resonated with me, and I felt very confident about it. I got my CAD Mojo back.
The design combined both abrasive water jetting and square stock machining. The water jet pieces were primarily there to accurately space critical dimensions.
The first half of spring break was making this 4th design iteration. Now that spring break is half done, I needed to start manufacturing.
It was a lot easier to manufacture things when you know exactly what you need to build:
Instead of waiting for 2.007’s system for waterjetting, I decided to just make it my own and used MIT’s hobby shop water jet machine.
I then plotted the holes on the square stocks very carefully and assembled the main pile driver structure.
Assembly was a huge pain… But in almost no time, i managed to finish the primary structure of the pile driver.
I had a lot of problems with tolerances, as I seem to always miss a few thousandths with the water jet… Particularly this unique triangular bracket:
This holds the pile driver tower up and I had a lot of issues when I forced myself to make the slots fit in and work. Vincent Kee told me that it doesn’t seem as strong as a regular L-bracket… Vincent was right and I would soon be proven wrong (much later into the semester).
For now, I went ahead and finished other stuff:
This was the hammer with a rubber end. The carrier is an aluminum square stock. Again, I waterjet an aluminum piece to connect them together. It was completely unnecessary to use the waterjet like that I know, but you know what? I might as well since I’m on the machine anyway.
Now that my hammer was up, I also needed to make the gearbox that will physically pull up the hammer:
It’s a 9:1 gear reduction. (bBig Gears are 36 tooth and small gears are 12 tooth).
The white cylinder at the left end is a pulley. The idea is that the hammer is reloadable. BUT HOW? There’s a gapped tooth on the 36tooth gear connected to the 12 tooth output. When the output spins to a gapped tooth, the final output shaft free spins as the hammers tries to pull it down.
As for the shafts, they are a combination of hex axles with .25in diameter ends
Anyway… After much turning with the lathe, here’s version 1.0 of the gearbox:
I think I did not account for the material properly because I had to use washers on top of the stand offs that I turned down… but there’s no point in changing this now since time was winding down.
Ok…. so I have part of the pile driver built, part of the gearbox built, now I need to start designing the drive base…
I’m very behind in the class… but I’m betting/hopping that my ridiculous amount of time spent on CADding will be paid off.
Here’s version 1.0 of the drive system:
It was a rough sketch with no screws, but I didn’t like how I had to create more gearboxes to make the drive system work… So I needed to revamp it.
Here’s version 2.0 of the drive:
I removed the gearbox and made it a 1:1 gear ratio. It has a very low drive base so that I can maximize my 12”vertical limitation.
A closer look at the 1:1 direct drive module:
A hex axle connects with the wheel. The wheel connects to the servo arm. The hex axle has a 0.25in shaft diameter to support the wheel on both sides.
I really dislike working in a machine shop without have any idea what to do. But now that my robot is slowly coming together in the CAD, I knew exactly what tools to use to make the drive system relatively quickly.
Back to waterjetting:
And here are the awesome waterjet pieces:
The ABS plastic makes a great stand off. I was getting really tired of making my own stand offs with an aluminum axle, so this was a nice change.
Assembly for the drive modules didn’t take long either:
Alright. Now that I have my modules together, I can finally assemble them all into a robot:
First…. I cannot tell you how painful it was to assemble the robot. There were way too many sharp edges that I should have fillet or filed. I should have really thought about designing for assembly. I think you just get into CADding so much that you forget that your fingers have to go in there somewhere to put the parts physically together.
Now that my 2.007 project is actualky starting to look like a robot… I couldn’t wait to try the hammer!
I really should have done testing much much earlier than doing it now… And only now do I realize how naive of me to not even do any testing..
So what happened? Remember that my output gear was a 12tooth? After 2 tries with the hammer, the piece was destroyed because it didn’t have any structural strength.
Also… I realize that I didn’t really support my input gear… After a days worth of machining I have a new gearbox:
Now that looks much much better…
I tested it once, and it worked… Although I don’t know if it can achieve the maximum 25 points that I’m aiming for. I figured that because my design is tunable, in that you can change the number of springs and the ending position of the hammer, I should be able to find the right configuration that will hit the high striker.
But I needed to start designing my ferris wheel mechanism. I really need to make sure that I get it right the first time so again I’m relying on Solidworks to do my “theoretical testing”
Here’s my ferris wheel arm attempting to spin the ferris wheel.
I was satisfied with how it was working on CAD.
Since I was really getting back into CADDing very quickly with satisfactory results, I did this tower in one try:
It’s a mechanism attached to a ratcheted four bar linkage. The spinning mechanism also had its own ratchet.
Here’s a close lookup of the ratchet deisgn:
CAD works. <3.
Finally… I have a 100% complete CAD of the robot:
All that is left is to finish manufacturing everything…
I went back to water jetting, and because I had a lot to do, I completely forgot to take pictures… sorry. But… I do have this:
I spent so much time on the water jet that my accumulated minutes was ~112 minutes. Woah. That’s around $224.00 or $336 if the department funds it… Thankfully they said they will fund it. PHEW.
Alright… Then I had to make a bunch more stand offs for the ferris wheel mechanism
It really did take a long time to finish. And this is not even all of it. I also had to turn down the spacers and remake them because of measurement errors
I now have reached the point where I am completely done machining the robot.
I did the finishing touches on the drive base by connecting the timing belt threads:
The Ferris wheel tower goes up:
Assembled the ferris wheel spinner:
I wasn’t done just yet… I still needed to make the VS-11 Servos continuous so I quickly took them apart and removed the mechanical tab which prevented it from spinning 360degrees.
And you just take this gear and remove the mechanical tab:
NOW…. all the hardware is done. There’s 2 days left before impound and I was thinking I could pull it off.
Assembly again was a real pain… but after much work it’s finally together completely:
Ahh yes… Finally… I quickly wired everything, and programmed it. I have much experience with servos and motor drivers that it wasn’t really a challenge to put them together.
Also, we were using a PS2x controller so programming was really easy for me since I did that for my UROP last summer when we worked with making the omnidrive robot.
For final touches, I labeled the robot ”Orthanc and Barad-dur” in spirit of FIRST robotics and labeling your robot as well as in spirit of Lord of the rings and the two towers. =D
The MIT Copy Tech is a great place to get laminated labels. :]
By impound time, my robot was drivable and could do the tasks that I wanted… However, it wasn’t do them so well. I only scored 1 pt during seeding cause I thought the hammer wasn’t working.
So how was the competition? It definitely gave me the robotics competition feeling to say the least.
Just like FIRST, there’s a place where the robot resides:
The competition floor is captivating and beautiful:
And finally, the people in it make it super fun and amazing!
(The guy on the far left wearing an orange shirt is professor sungbae kim. He’s one of the leading roboticist in the world. The cheetah robot and stickybot for example).
During the competition I was eliminated on the first round after I scored 5 pts. I wasn’t paying attention to the competition so I misfired my hammer twice. By my 3rd try, there was no time left to do the multiplier. Oh well…
I took the class with an arrogant attitude and that definitely back fired. I couldn’t even CAD for the first 2/3’s of the semester for some reason… Was I too sick? Or maybe I was really burned out from IAP for working 18 hours a day? I wasn’t sure… But 2.007 definitely was a big learning experience surprisingly.
Also, I’m glad I got beaten out completely. If MIT’s 2.007’s best student is me, then the world is in trouble because I have much to learn.
You can watch the full competition here:
I am just glad that my robot turned out exactly as how I wanted, it could be better, but it is what I designed: