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an incoherent world 003

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Well.
I blame the end of term and 2.009 peer reviews, which I’d just read when I wrote this script. I wish I had a stronger ego, so instead of moping I could be like “Hah! I shall go forth and work on this problem.”

No worries! The next few strips will (a) actually contain technical content and (b) be more lighthearted. Hopefully. 😀

Additionally, I was looking for comics by makers, and found it difficult to find any @__@. There was this: http://citizenengineer.com/ce01.html by one of my heroes, ladyada, and Phillip Torrone. But it is more photorealistic than comic-y, though it adheres to the comic format.

This article was also interesting:
http://blog.makezine.com/2011/04/07/which-comic-book-character-is-the-greatest-maker-of-all-time/

This page took a third as long as the other pages, since I really only had to draw two simple panels u.u

==
Anyway, long rambly personal blog things follow:
http://www.quora.com/MIT-Massachusetts-Institute-of-Technology/What-are-the-downsides-of-attending-MIT-as-an-undergrad
That about sums about MIT for me. Especially,

Plenty of people at MIT do perfectly normal, youthful diversions from the beaten path – like taking time off, build disco dance floors instead of studying, intentionally take 7 or 9 classes at once “to learn as much as I can”, and the like. However, the people who can do this and are visibly *confident* of it are in a clear minority. The others – I’d venture to guess a majority of campus – often wind up with serious identity crises in an undergraduate culture that rewards maintaining the same level of “excellence” at MIT as it took to get in – getting As and being in six clubs on two hours of sleep a night, and then graduating into Google, Wall Street or Ph.D programs at “name” schools (depending on your circle).

Ouch. ;__; Oh right, last last term and taking 8 or 9 classes. That ended poorly (with two incompletes and a my first D…), but I still maintain I have no regrets. I definitely fall into the “insecure about not getting As” group though. But what worries me is that, right now, I have almost no desire to take more than 2 or 3 classes.

Oh and as my friend Cathy Wu says on that same question,

I fear that many students enter MIT with the potential and aspirations to substantially improve the world (help solve world problems, innovation, etc.), but spend their four years working themselves to death such that they burn out by the end, and they end up not achieving their full potential. I only have anecdotal evidence of this.

-__-;
I remember coming to MIT in part thanks to the existence of D-Lab and Amy Smith and the work on international development. This sense that there is something really f***d about the world, that if only I were more [technically] competent I could help address, has been a driving force over the years. But lately I’ve been very internally focused and wondering if I’m not a startup-founder, self-motivated type after all. : / I’ve taken a long, long, break this winter break, I’m not even really doing anything over IAP, I really enjoy being on hall, yet I still feel distressed all the time. Talk about a waste of stress! Hah. I think mostly it is uncertainty about grad school / the future, and constantly stressing about what I should be doing with 2.007x. @__@ Uweh, I need to set some deadlines and make up my mind already.

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an incoherent world 002, gimp + bamboo cth460

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I suppose I ought to make note of the silliness in these pages. 
SLAM = simultaneous location and mapping. at the end of 2.737 mechatronics we each talked a bit about projects we’d worked on, and my classmate will vega-brown is in the robust robotics group @ CSAIL and is working with quadrotors. I think the video he showed is is still hidden (awaiting publication or something).
panel 3: they really do make tiny functional robots! 
I watched this video when the prof from the UC berkeley biomimetic millisystems lab came and gave a talk. I guess if I had planned life out more thoroughly or if I was more ambitious, I might have applied there for grad school. The more options the better, and right now I only applied to one place x.x oh well. WHATEVER. life will fall out as it will. also inspired by the bugs in 9 and this creepy and kind of depressing comic I read while bored.
oftentimes, though, with these tiny robots they don’t process their data onboard and send it via radio to a computer that gives them an estimate of where they are and where to go next.

panel 4:
555 footrest (turned nightstand in this instance?)
jordan dropped her quadrotor and one end was bent at approximately the angle of the quadcopter in the mobile, but something about trimming the propellers and her quadrotor still flew perfectly fine.

oh and that thing to the very right is a ballcopter (well, the kit ones upstairs of MITERS are white plastic so they must come from somewhere else), popular thanks to this video.
===
hrm and pg 1:

pg 1
cruft = discarded junk. crufting = the art of hunting for such junk to reuse in projects.
and… idk what that is. tesla coils on hexapods. hexlas. because why not?
===
Oh yes, about GIMP and bamboo CTH-460 on windows 7: works fine.
Initially it didn’t work : / even after installing the bamboo drivers and restarting, this is what I would get:
I ended up uninstalling the drivers via the control panel and reinstalling, and this time when I started GIMP the tablet I borrowed works fine.

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punt punt punt

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punt punt punt
…
a few days ago on the facelolz i said that

It’s now conclusive that I do not ask enough questions when I get stuck on things, and that this is unacceptable as it will impact my work performance. (I theorize that this ask-questions problem is why I am so mediocre at school).
Therefore, my goal for the next two weeks is to ask at least five dumb but coherent questions a day, and as proof of that I will write the answers up on my blog.
(I am still thinking a bit as to whether this casual-question-asking will actually translate to me asking more questions when I feel like people expect me to know more than I actually do).

So! then i asked questions. turns out most of the questions were so silly they don’t even merit writing down and/or I’ve completely forgotten them. But here today I’m writing down some notes on controls courtesy of Shane with mock-quadcopter demos by Charles (not duplicated here).

some of those questions were silly questions like how do i do controls in real life, as opposed to in labview on a $10,000 national instruments card.
then my brain went “speaking of things i want[ed] to do consistently to improve on skills…”

src files. wacome graphire4 4×6, inkscape, gimp. crashlanding, caeldera, digitalstrip2 fonts from blambot. ~4.

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the theory behind both is the same, ignore current incompetence (flaunt it? sorry, internet, for adding to the general scuz of atrocious material) and focus on learning learning learning to get to where i want to go…
(credit to MITERS folks for creative inspiration, including conversations with Dane about post-apocalypticc robot boxcar somethings.).

hmm. Right. controls.
Say I have a quadrotor. How would I go around implementing controls for it?
e.g. in 2.737 mechatronics class, we use a digital signal analyzer to characterize the plant. But no one tries to do that to their quadrotor. One possible way: mount quadrotor on stick, rotate it along one axis at a time. But, in real life:
Generally PD controllers.
If you didn’t know that, you could model it as a mass and damper (really simple model). Small number for damping (only comes from moving through air, minimal), e.g. damping coefficient of 0.1. Don’t know distribution of mass along quadrotor axis, so just model as evenly distributed — really does not matter since will end up tuning gains empirically anyway.
Proportional controller is like a torsional spring. Bigger error, bigger control effort.
Derivative controller is like additional damping. Otherwise, with proportional controller will correct for error but then due to lack of damping will oscillate.
Start out with too little gain, because then it will fly but drift off to the side. With too much gain, it will oscillate and flip over. Then slowly increase P gain.
Converging on the gains — a common method is Zieger-nichols. General idea is to up the P gain until it just begins to oscillate. Now up the damping (D gain) until compensate for oscillation, use some magical constants, … that sort of thing.
PD fine for flying indoors. But outdoors, wind will cause constant offset. Need I[ntegral] term. Also helpful if one motor is weaker than others, other sources of constant error.
Bandwidth and sampling frequency.
Limitation: how fast can control code loop run on microcontroller (mcu). Mcu has system clock (16Mhz for atmega’s). Rule of thumb, +-* each operation 1 clock cycle. Dividing integers four clock cycles. Floating point, tens of cycles. More margin because processor will need to respond to interrupts. This is upper bound on sampling frequency.
Lower bound, well, only need to respond to user input, and human reaction time perhaps 0.5 secs, 20 Hz. But also want to reject higher frequency noise e.g. from wind.
If calculate these and not overlap, need more efficient code or more powerful processor.
Tuning gains — actually pilot dependent. Some people like higher gain despite closer to instability because will respond quicker to sudden turns. While people shooting video will want higher damping so that footage is smooth, okay to more slowly respond to errors in position. 
Segging things are like quadrotors but with one axis instead of two.

projects blog (nouyang)