Wow, haven’t posted here in a while! A lot has changed in the last almost-2-years since I’ve updated this blog.
Now, I update my personal website more frequently. Please check it out at:
Wow, haven’t posted here in a while! A lot has changed in the last almost-2-years since I’ve updated this blog.
Now, I update my personal website more frequently. Please check it out at:
Summer 2010 was fantastic! It went by so fast, and I had a great time. Here are a few highlights:
Despite having lived in Massachusetts my entire life, I had never been in Boston for its famous July 4th weekend. Don’t get me wrong — I’ve always really wanted to go, it’s just that the traffic into and out of Boston is infamous (around 800,000 people flock there), so I’ve always ended up just watching everything on TV. However, living on campus for the summer right along the Charles and just a short walk away from the Esplanade changes everything!
Boston is famous for two things on July 4th weekend – the Pop’s Concert and the fireworks. It’s sort of ironic though that most tourists who visit Boston to take part in the festivities don’t actually get to see both — if you have good seats at the concert, you can’t see the fireworks, and vice versa. That can put a damper on things, but luckily there is an optimal solution! The Pop’s have a rehearsal concert the night before on July 3rd that’s open to the public. It’s nearly the same as the main concert on the 4th, with the exception that there aren’t any fireworks at the rehearsal. My friends and I decided to go see the rehearsal concert on the 3rd, and then to see the fireworks on the 4th so that we’d get the best of both worlds – being able to see BOTH the concert and the fireworks!
July 3rd started out as a pretty relaxing day. After going to a leisurely BBQ at Next, I walked down to Baker to meet some friends who were going to the concert. I ended up meeting some more friends while we were en route to the Esplanade, so we all went together. The rehearsal concert was scheduled to start at 8:30 PM, but we decided to get there pretty early (around 6:15) – and it’s a good thing we did! We bearly got seats, even at that time. Most of the oval outside the Hatch Shell where the concert was packed – except for a small area in the back where my friends and were lucky enough to claim and set up camp. Even though we were pretty far away from the Hatch Shell, we still had a great view:
With an abundance of liberty hats, American flags, people, and over-priced food stands, it was a recipe for good times. We waited it out until the concert started by chatting, playing cards, and taking pictures. Finally after a lot of waiting around, the concert started. The Pop’s really did sound great, and the Hatch shell looked fantastic:
The guest artist this year was Toby Keith, who is famous for his country music. Probably my famous song of the night was the 1812 Overture, which sounded great. There were even cannons near the end:
Another great part was the patriotic sing along. Seriously, I’m not a very good singer, but I had a lot of fun anyways (which probably means the people in my immediate vicinity didn’t!). Overall it was a great concert, and afterwards we returned back to our dorms. I went to sleep very tired, after a long day of relaxing and doing absolutely nothing.
July 4th was a giant Boston picnic! Seriously, people were just lounging around in the closed-off streets, having a great time all day waiting for the Fireworks. I was with some friends along Memorial Dr., and we had a spectacular view.
And then it got darker.
…so we started playing with lights and cameras:
And then the fireworks came! They were excellent. We were so close we could *feel* the gush of air a few seconds after some of them exploded. It was great. Here are some of the finer pics:
Yes, I’m writing another post about bicycles. Sorry if you’re one of the people who has to listen to me talk about them all day, and then read my blog posts about them at night.
I’ve asked myself why exactly I enjoy bicycles so much, and it’s surprisingly hard for me to answer. I like the efficiency and speed in a road bike. I like its thoughtful design, with every minute detail well considered. For some inexplicable, perhaps instinctual reason, I also really like spinny things… I’m not sure. But I do like them. Bicycles appeal to the mechanical engineer inside me, and so maintaining the machine can be just as much fun as riding it. As such, I decided to purchase a few bike tools and have a hand at working on my bike last weekend.
The first things that needed repair were my tires, which were in pretty bad shape. They were very likely original, and had the tan-walls common to many vintage road bikes. However, the tan rubber was peeling and cracking in a bunch of spots, and a friend at MITERS (the MIT Electronic Research Society, a pretty cool hackerspace around at MIT that has any bike tool you would ever need) informed me that they were just about to blow out. So, I went down to the local bike store and bought some tools, a pair of puncture resistant tires, and new inner tubes (the part that actually gets inflated – the tire is just a rubber covering for the tube).
Armed with these and an arsenal of YouTube videos, my days as a bicycle mechanic were about to begin. I went down to MITERS to change my tires, which went fairly smoothly. I’m glad that, after taking off both wheels, I was actually able to put them back on again. Here are a few pictures of the sleek new tires:
I also ended up adjusting the brakes (single pivot caliper), because the pads were rubbing on the back wheel at times. That wasn’t too bad. While the wheels were off, I also tried doing some (very minor) truing adjustments, to the point where I barely changed the wheel at all. But maybe it helped a bit, haha.
The bike rides great now! I don’t even have to worry about tire blow-out any more. The one thing that still needs to be fixed is the slightly warped chainring, which makes a funny clicking noise when I pedal in certain positions in a certain gear. I’ll save that story for next weekend.
Wow… I’m going to be a senior… Just one year left?!?! This year flew by so fast… especially last semester. I truly can’t believe how fast college is flying by. But on the other hand, looking back I feel that I’ve changed a lot since my freshman year.
As I’ve done every year, here are some highlights of junior year that come to mind:
I suppose that this past semester, most of my class-related blog posts were dominated by 2.007. It’s only fair to talk about my other classes! This post is dedicated to 6.141, other known as Robotics: Science and Systems (RSS). It’s a great class. Unlike 2.007 which is nearly completely focused on the mechanical design of a robot, I’d say that about 20% of RSS is focused on mechanical design. The rest teaches students about control, locomotion, sensory perception, computer vision, mapping, and navigation – all done autonomously. Whereas in 2.007 we controlled our robots manually, in RSS are robots run autonomously without human intervention! RSS is taught by the EECS department, and 2.007 by the MechE department (which explains these differences).
Also unlike 2.007, RSS is a team-based class. We keep the entire team throughout the term, and work on a series of labs that lead up to the Grand Challenge – constructing a robot to complete a specified task. In RSS, the task is to locate and pick up brightly-colored blocks, and build a structure out of them – all autonomously. It’s quite the challenge!
I was lucky enough to be on an all-star team with some pretty cool people. We decided to take the hard road, and planned to build a very ambitious robot in nearly every respect. We scrapped nearly all of the mechanical parts given to us and completely redesigned the robot, opted to use a deliberative rather than reactive architecture (which is much harder to get working, but great for its educational value). We even rewrote the low-level controller powering the wheels.
We knew at the beginning that this would be a challenging project, and that we were perhaps biting off more than we could chew for a one-month project (especially given that we all had other final projects (like 2.007 for me!)). We decided to go for it anyway, and it was a great learning experience. Although our robot didn’t do everything we wanted to in the end, and we had very little time for testing, we certainly learned a lot through our extensive use of all-nighters at the end of term. I also made some pretty cool friends, and had a blast.
Here’s a picture of our partially-functional robot, using computer vision to pick up a red block. Not that the arm has independent control in the X, Y, and Z directions (like a CNC milling machine). Here’s the video:
Here’s a group picture of our team, with our robot:
Again, RSS was a fantastic class! I’m so glad I took it. Taking two robotics lab classes in the same semester did prove to be quite challenging, but definitely worth it. Right now, the robot is chilling in my room. My teammates and I are planning to work on it some more over the summer, to finish up the parts we didn’t have time to complete and get it working for fun.
Bikes, bikes, bikes, bikes, bikes. As some of you may already be painfully aware, I talk about bikes a lot. That’s because biking is a new hobby of mine, And I freely admit that I’m perhaps a tad obsessed
It all started about a year ago, when I bought my first full-sized hybrid bike (previously to that, I had an old 24″ bike from middle school at home that I hardly used). The bike I got was great – it was an inexpensive mountain-like hybrid that got me around campus, and I also went on periodic joy rides around Boston when the weather was nice. Here’s my old blog post from when I got it.
But then, sometime around the middle of second semester, a good friend of mine let me try out his road bike. And things just went spinning out of control from there (!). Road bikes are *very* different from mountain bikes. The handling is much “narrower”, the wheels are much skinnier and inflated to a higher tire pressure (thereby reducing rolling resistance), and the geometry is markedely different. Road bikes usually have drop handle bars that can allow the rider to sit in a more aerodynamic posture, which is also better suited to the legs for pedaling. This all adds up to a faster, more efficient riding experience (though some comfort and ability to ride off road is sacrificed).
I admit that, when I first tried my friend’s road bike, I didn’t like it that much. I wasn’t used to the narrow handling and the short handlebars — it kind of felt like I was learning how to ride a bike again (complete with almost falling off several times)! Once you get used to it though, it really does seem like the natural way to ride. And the speed and efficiency difference is phenomenal. The road bike spoiled me.
Around the end of the semester (after finals, thankfully), I started my lengthy bicycle search. I’m the type of person that has to do lots of research to make a very informed decision, so I started reading lots of biking websites (www.sheldonbrown.com is a great resource, by the way). At first I was going to buy a lightweight single-speed bike with skinny tires (the KHS Urban Soul, ~$400) that another friend had and loved. But then I started looking around, and got dizzy with so many options. Here are all of the bike options I was considering, in chronological order:
As you can see, I was all over the place with what I wanted! For a while there I wanted a new multi-speed road bike. However, unlike mountain bikes, entry level road bikes are pretty expensive. Whereas it’s possible to get a cheap mountain bike for ~$125 in many stores with many models to choose from, entry level road bikes start at around $650. Big difference! It’s easy to find a road bike in the thousands, and if you have a large enough pocketbook, it wouldn’t be hard to spend around $10,000 on a pro racing bike.
That’s one of the reasons why I started looking into vintage road bikes; they cost a fraction of the price. Older bikes are very popular around campus as well. Their styling is distinctive and elegantly simple. Unlike modern road bikes which are nearly always aluminum or carbonfiber for lightness, older road bikes generally have steel frames (which are heavier, but provide a smoother ride). There are still a plethora of road bikes from the ’70′s and ’80′s around the city. I figure, if they’ve lasted that long, then they must be made pretty well and probably continue to last!
The problem is, you can’t buy new old bikes anywhere. You have to get them used, off of a website like craigslist. This made me a bit nervous, since you never know for sure who you’re dealing with and the quality of what you’re actually getting. Nonetheless, I started searching around craigslist for a few weeks. After a few failed attempts, I came across an ad for a light-blue road bike, supposedly in good condition. I took the bull by the horns (or the bike by the handlebars, I should say…), met the seller, and purchased the bike. Hooray, my first road bike! It was in overall very good condition, especially cosmetically. Here’s a picture I took in my excited euphoria that night after purchasing it:
It’s a Sterling Sporten, which was a subbrand of Univega bicycles. The bike was in pretty good mechanical condition as well, although there were a few minor issues. The tires were old (probably original) and were cracking and just about to blow out, so a tire (and perhaps tube) change was needed. Also, part of the crank shaft was slightly warped, but I think that can be fixed pretty easily just by pending it into place. The brakes and shifters worked great (although the friction shifters took some getting used to).
Overall, it’s a fantastic bike and I’m so glad I purchased it. I’ll keep you updated with my biking adventures!
Alright, it’s finally time for me to talk about the 2.007 finals! Luckily, my machine was fortunate enough to get a good seeding score, meaning that my placement in the preliminary rounds would be good. The prelims were held the day before the finals. Everything was held in the Johnson ice rink, since there’s so much room. On both days of the competition, Johnson was packed with a loud, cheering audience. Excitement, suspense, heartbreak, and hard-won victories – robotics competitions are the MIT equivalent to football games at other schools!
Here’s a recap of the prelims, which were the rounds leading up to the finals. Some of my friends showed up to watch, which was great! The 2.007 staff recorded short videos of people’s robots, and here’s a picture of my video being played on the projector screen:
Finally, the field was set. It’s nearly time to do battle:
I was a bit nervous at this point, since there was so much adrenaline and excitement pumping through my veins. I knew the competition was all in good spirit though, so I just had fun. Here’s my robot, starting to drive:
Here’s my robot, starting to extend (it started with a codice in it’s claw):
Here it is, continuing to extend – and right about to score!
My little bot scored 4 points that round, which I’m very proud of. I wasn’t able to go get the second codice, because I ran out of time and got stuck a little bit while driving. 4 points turned out to be enough to advance, meaning that I would be in the finals the next night!
The next day, it was time for the finals! I was already very proud of my robot at this point, so I didn’t feel too much pressure that night. My first match was against a pretty neat robot that also used a scissor mechanism, although it was connected in a very different orientation.
When the match began, my robot was functioning pretty well – it backed up, and then started raising its scissor mechanism. However, my robot suddenly dropped the codice it was holding! My theory is that my basic stamp browned out due to the very high current requirements of the DC motor powering the lead screw (it was nearly stalling at it’s most difficult position), causing the PWM signal to the gripper to temporarily drop out. Hence, my gripper arm opened, dropping the codice. Unfortunately I didn’t have enough time to recover from this, and I ended up scoring 0 points during the round. It’s okay though – mistakes always happen, and I still had a blast in the finals. One can always learn from failures – if I had to do it again, I likely would have spring-loaded my gripper shut, so that in the event that a power fluctuation did occur, the gripper would still have held on to the codice. Oh well, maybe next time
Well, this is probably my last post for 2.007. I have to say, 2.007 was one of the coolest and most rewarding classes I’ve ever taken. Before 2.007 and 2.670 during IAP, I had virtually no machining experience and I’d never build anything out of metal, ABS, and other similar materials. By the time the class was over, I was much more knowledgeable, had some practical MechE “street credit”, build an awesome robot, and made a bunch of friends on the way. If you’re thinking about taking 2.007 or even majoring/minoring in Mechanical Engineering, I’d highly encourage you to do so. 2.007 is the kind of class that reminds you why you wanted to go to MIT – to learn, and to engineer awesome stuff
In my last 2.007 post, I was making a lot of head way on robot… but I still had an immense of work to do! In this post, I’ll describe how I finished the robot.
Last time, my robot didn’t have locomotion built yet. Oh, to think how far my little bot has come… It’s all done now, complete with locomotion, a working counterweight, a working gripper, electronics, and the lead-screw powered scissor mechanism!
My locomotion mechanism is fairly simple. I have two continuous-rotation servos powering opposite sides of the bot, effectively giving it tank-style control. The two powered wheels are located towards the front of the robot, which is generally heavier and will therefore provide more traction. There are two castor wheels on the back counterweight (which works!) for balance so the robot won’t tip over. My counterweight is powered by a quarter-scale servo, hacked to be continuous. This servo drives a rack-and-pinion that pushes the counterweight out. The counterweight itself is a large chunk of heavy steel. Here are some pics of the locomotion and counterweight:
I also started integrating some electronics! We’re using the Basic Stamp, a cute little micro controller. Although I originally planned on doing some fun autonomous control with sensors, I ended up running out of time in the mechanical construction phase and didn’t have time. I am however using the microcontroller to mix input signals and give me a more intuitive control from the radio interface.
Here’s a picture of the microcontroller, all wired up (you can also see the lead screw motor controller board in the background):
After a long semester of hard work, my robot is finally D O N E!! Here are a few pictures of it:
Also, here are some tour videos of it:
I’m very proud of this little guy Next time I’ll talk about the final competition!
Hey all, it strikes me that I haven’t blogged in a very long time… nearly months! A lot has changed since then! So, it’s time for an epic blogging session in which I try to crank out as many entries as possibles. Some things that I’ll be talking about: