Tuesday, July 20, 2010

DASH Robotic Insect

Just watch the video, there is so much amazing innovation in this robot. One after another...

Air Cannons

I've wanted to make one of these for a long time, but you'll always have to spend some money and a trip to Home Depot. Here are some great resources anyway. I really like the simplicity and easy instructions that the Make projects have, plus the Crazy Builders' project has interesting mathematics and physics explanations. Besides what I've said, there's not much more to say if you watch the videos.

Maker Workshop Burrito Blaster

Crazy Builders Air Cannons --- be sure to go to the site and check out the tabs at the top

Make Weekend Project-Compressed Air Rocket

Robot Survival Game and hit sensors

Found on BotJunkie: http://www.botjunkie.com/2010/07/20/inaugural-robot-survival-game-takes-place-in-japan/

I don't care a ton for the robot wars genre, but I had to post about it this time. What got me was the interesting hit sensors in this competition. These tinfoil boxes cover up a light sensor. When the robots' airsoft guns make holes in the tinfoil, the light sensor registers more light. After a limit of holes/light/sensor reading, the robot is declared defeated.

Otherwise related: Mech Warefare competition.

Robot Survival game video:

Extruded origami text

Found on Make: Online: http://blog.makezine.com/archive/2010/06/extruded_origami_text_pattern_gener.html

Make: has these Math Monday posts, which often talk about origami. This one talked about the work that some college students did on folding letters with paper. The letters are raised up like 3D walls. They wrote a short paper on it and made a web application for generating paper with the fold lines for whatever message you want.

If you think it's cool, it is. But be forewarned, to fold one of these things is not an easy task. Look at the paper you've got to fold for the above "Hello World" message. The red lines are "mountain folds" and the blue lines are "valley folds." Have fun.

As ambitious as this was, I decided I'd try to tackle it somehow. Starting with single letters is best because it gets you familiar with this type of folding and the different types of corners. I started with the capital L because it has only 2 types of corners: a right angle corner and two starting corners. In retrospect, starting with the letter i would have been better since there is only one kind of corner. I ended up cutting the paper apart into the different corners so that I could work on them separately. It was difficult to fold them when they are all on the same paper, much less learn how while I'm at it. Later I paper clipped it together and it turned out ok. I paper clipped it in case I wanted to take it apart for reference.

I found that the instructions for folding were incorrect. First of all, they described the lines as being "dark" and "light." Kind of annoying that they don't call them blue and red, but I guess they mean if you print it out black and white, the blue turns out darker. But after finishing my first L, it was extruded downwards instead of upwards. Unless you wanted upside down and mirrored text, the instructions were wrong. I folded the letter i twice to check this; once with the folding instructions reversed. Now I fold the letters like they should be: red is mountain folds, blue is valley folds.

Next I folded an L that wasn't cut up, then did it again to make it more accurate and look nicer. It turned out pretty well. Here's a picture of my current foldings progressively from left to right. The top left one is a single starting corner that I cut out for my first L.

Next I plan to do the capital letter T because it has the "T"-type corner in the top-middle. There is no such thing as a 4-way type corner, so that's all you need.

If you want to try doing this, I suggest doing what I did: start with simple single letters, and cut out individual corners to work out first. Other than that, just work with the paper and be patient as you try to make it work. It eventually comes to you. The first L took me about 2 hours, the last L took me about half an hour.

RoMeLa's Charli-L's legs

My previous post talked a little bit about RoMeLa's Charli-L, a robotic humanoid from Virginia Tech. Look him up for more information. His main purpose is to compete in the Robocup competitions, but he's also just a robotics development project for the college.

Charli-L has a big photo of himself on the front cover of Popular Science's August 2010 magazine. When I was looking at it I became interested in his legs for a couple of reasons.

  1. The main shin and thigh components are 4-bar linkages. This seems to be a nice, stable, and simple way to move the legs. I noticed that the bars are at different heights in relation to their pairs, i.e. on the shins, the back bars are higher than the front bars and vice versa for the thighs. I assume that this is so that you can get more rotation out of the linkage because the bars will "run into each other" later than if they were equal.
  2. There are large springs on the shins and thighs. These obviously help the motors work the legs by taking some of the effort. But on further inspection, based on what vertecies of the linkages they are connected to, the springs seem to be pulling the legs into an extended, straight position. This might be to help the robot stand better and to help the motors keep the legs from collapsing under the robot like jelly. It might also be because it is easier to control the legs when they are working against a force to bend a leg. Instead of holding the leg precisely, you only need to worry about moving in one direction, even if it's at various speeds or strengths. You don't have to worry about "pushing" the leg in the other direction to make it extend; the spring does that for you. You just have to limit or counteract the spring's force. It's sort of hard to describe and I can't think of a really good example...maybe a pulley with a weight instead of without?...I might think of something later.
  3. There are these strange objects whose purpose isn't clear to me. They are inside the thighs and look like heavy-duty actuators. They have gold ends, black tapered middles, and ribbed bottoms. Either they're for structure support or they are actuators. But the structure of the legs don't support these theories. If they're for support, why don't the shins have them. If they are actuators, there is nothing they can move; that thigh part is solid.
So just some interesting things to think about.

American mindset of purposeful advancement

Popular Science had an article in their recent August 2010 magazine about humanoid robots. It was specifically about RoMeLa's (Virginia Tech) Charlie-L and how it's basically the first and only humanoid robot in America, where as Asian countries have loads of them (think ASIMO, etc).

Here was one quote that I found intriguing and that slightly sums up why America doesn't have more humanoids:
(Daniel Lee, co-runs RoMeLa):
"If you write a proposal here for a robot that plays music, you'll have a very hard time finding funding. What's the practical purpose?...Yet if a robot improvised a jazz performance, it might teach you all sorts of things about artificial intelligence and even human intelligence. There's more openness to that kind of investigation in Asia and Europe. Here the focus is on a well-defined problem."
I have seen this in American thinking and it frustrates me. There are some college students who made an interesting breakthrough in technology, interfacing, or control. They describe it all nicely and you get to the end and they give their cobbled-up answers to what this could be useful for. You can easily tell they are thought up to work with their professor's assignment or to make sense to a sponsor. Then they continue to explain half of their other work, which is how to eventually integrate this technology into our lifestyle. What's wrong with exploring technology for the purpose of exploring it? Sure, the process and information can be formatted so that someone later can use it for something helpful and the work shouldn't be "pointless." But sometimes the purpose should just be to learn more about ourselves, our world, and what we can do with it; that kind of knowledge is beneficial and exciting enough. There doesn't always need to be an initial problem.

Monday, July 12, 2010

Military missile vs. missile protection systems

Found on RobotJunkie: http://www.botjunkie.com/2009/12/02/active-protection-systems-think-fast-to-intercept-rpgs/

Two active protection systems that show the rate at which computers can think and act. The first is called Quick Kill and uses radar to detect incoming missiles, then sends a self-orienting missile to detonate in its path. The second is called the Iron Curtain and uses radar and optical sensors to sense RPGs fired at military vehicles. Then missiles mounted on the edges of the vehicle fire downwards at the RPG when it comes close.

Quick Kill:

Iron Curtain:

Robot collision safety with knives and saws

Found on RobotJunkie: http://www.botjunkie.com/2010/05/07/robots-with-knives-robots-with-knives/

This is an amazing post on RobotJunkie about robot safety work that the Institute of Robotics and Mechatronics in Germany has done. They did research to find out exactly what happens when robots dangerously collides with humans (besides, you know, death). This was to help make a collision avoidance system, which works great when they integrated it with their robot arm. They reduce the cuts down to 1-3 mm lengths, which is much better than getting stabbed all the way through. Check out this video, especially all the way to the end when a real human gets tested!

This second video is about work with basic collisions, no knives. This deals with large robots that someone would be dealing with in, say, an assembly line.

On RobotJunkie they made the very good point that this is why we don't have to always be afraid of robots. They are certainly powerful and can do damage, but when you are careful and develop a sense of safety around these special mechanisms, you can use them to your great advantage without hesitance. On that note, RobotJunkie included this video about the SawStop, which I'll also include here. The SawStop is a table saw that drops the blade below the table surface if it senses a finger touching it. Watch the video to see more about how it works.

Saturday, July 10, 2010

Engineering reliance and independance quote

Here's a very intriguing quote by oakshaman in a review on Amazon about a mechanisms book I plan to buy:

"The many crisp line drawings are presented with a minimum of explanation and no dimensioning. You see, it was assumed back in those days that a person with natural mechanical aptitude could look at a diagram, or a machine, and figure it out. Not only that, but it was assumed that once you had the idea, then you could work out all the details for yourself without having to be told everything down to the last screw size. While there is a descriptive paragraph indexed to every drawing, most of the time you don't really need it.

This book comes from an age when engineers and designers had to have the talent and the knowledge to use the mechanical principles of levers, linkages, cams, gears, etc. to produce a given motion- and to link together many such elegant little mechanisms to get a bigger job done- reliably. This isn't done much anymore. Now most machines are huge, cobbled-up, Rube Goldberg devices of pneumatic or hydraulic cylinders, screw actuators, or servo motors- all interconnected by electronic controllers. The whole thing is controlled by software of even more dubious reliability.

Up to the "digital revolution", this book shows how it was always done- it's how I learned it. Of course, once upon a time, a mechanical designer actually had to understand machinery, and the basic principles of physics, and not just how to write code...."
It just about puts a whole new perspective on how you look at things like this. Well said!!

Heron's Fountain

Found on Makezine.com
Antique Heron's Fountain on Makezine.com
Wikipedia-Heron's Fountain

Heron's Fountain is a water fountain that squirts water upwards because of the falling of other water. The concept uses hydraulics and pneumatics. It can seem paradoxical and like a perpetual-motion machine, especially since the water shoots up higher than its "original source."

Here's how it works. The water in the basin falls to the bottom beaker. The water coming in pushes the air out of the beaker. This is the important mechanism. The vise versa happens in the top beaker. The air coming in from the bottom beaker pushes the water out of the top beaker. This water gets squirted out into the original basin.

This is not a perpetual motion machine because water will eventually run out or fill up somewhere. The typical justification is that the basin will never run out of water because it is continually being refilled. But consider:

  1. the basin is being refilled by the top beaker, but the system will stop if that beaker runs out of water to squirt.
  2. the bottom beaker could completely fill with water and there would be no air to push out.
  3. I don't know if this would actually work, but there might end up to be too little water in the basin to provide enough pressure to push the air and water out of the beakers. The reason that the water gets squirted out is that there is more water in the basin that provides more weight and pressure than the amount of water being squirted out. But if an equilibrium occurred because the basin water runs down, the system would stop. Maybe the refilling of the basin is just enough to keep it going until something else stops the system.
Something interesting is that the top beaker doesn't need to be above the bottom beaker. It could be positioned anywhere and squirting water anywhere. It is not affected by gravity as the falling basin water is. It would be different if we were squirting with a tube coming directly from the basin: as soon as you point or position it too high, the water would stop squirting.

It is popular to position these fountains in a straight line (to be more mysterious) and make them artistic, like this one. If you want to experiment, there are multiple instructions online that show you how to make one from pop bottles and straws.

Friday, July 2, 2010

Mindstorms NXT screen fix

For a while my screen on my Mindstorms NXT had been broken. When I would turn it on and press buttons, it would make correct sounds, but the screen would be blank or sometimes show flashes of lines across the screen. Putting new batteries in and updating the firmware did nothing. I did a search online and this matched the symptoms of other people. They had found a solution:
re-solder 3 capacitors inside the NXT.

Thankfully this procedure only required "tapping" the contact points, which means to re-melt the existing solder so that the connection is better.

Feel free to use this post to learn what to do in this situation. I've tried to include enough information for that to be possible. I get a lot of views of this post every month; there are a lot of people with is problem.
If you've never soldered before, I suggest you watch a couple of videos showing how. Maybe practice soldering two wires together first. But don't be daunted, with some practice and common sense it's really not that hard and pretty fun.
Here are two places that I used as a resource:
http://forums.nxtasy.org/index.php?showtopic=2713 - 5/3/12 sorry, this link appears to be dead now. Nxtasy has ended and now they have a small site with some forums.

Opening was simple, just remove batteries and unscrew the 4 screws underneath.
Here's what the inside looks like after the cover is removed:

I needed to get at the underside of the daughterboard, the secondary circuit board connected to the screen. The screen is screwed in by the white plastic it is attached to. The daughterboard is attached to the motherboard by pins (two rows of metal leads, left and center in the picture above) and needed to be gently pulled off. The speaker, which is attached to the screen, is attached to the motherboard by wires and can't be taken off completely.

Here's a close up of the insides.

I put the screen back in place without screwing it in and attaching the daughterboard pins. Then I flipped over and taped down the daughterboard. Here's its underside.

Here are the capacitors that are causing the trouble. They are surface mount capacitors, so they are small, compact, and don't have wire leads. Examples of "normal" capacitors can be seen above as large, black cylinders on the motherboard above (look at the "insides" picture).

Tips for tapping/re-soldering the capacitors:
-Be patient and wait for the iron to warm up, it won't really work with a cold iron. Test it by touching it to solder from a reel; it should smoke/burn/sizzle right away and not cool off on the iron.
-You may need to apply some pressure to the solder points to melt the existing solder.
-Don't hold the iron on the circuit board too long! It may not seem like it, but electrical components can get damaged from the heat. That can certainly happen to these small capacitors. Work quickly.
-If you need to apply new solder, go ahead, that might work better.
-Clean up the connection by dragging a clean soldering iron across/by the connection. The iron and the contact points will wick away extra solder to themselves, and you will clear away any bridging mess in the middle. This is especially helpful for the area between the C1 and C3 capacitors.

I had learned my lesson from before to be patient with the soldering iron and wait for it to really heat up. But this time I learned that I needed to apply much more pressure to the contact points to make the solder melt. After that was done, I did a quick test without closing it all back up. It showed more stuff on the screen, but it still was sketchy. I flipped over the daughterboard and tapped the C3 capacitor again, which I didn't think I did a good job on. That did the trick.

Here is the fixed screen. I just laid the rubber buttons on the button contacts so I could operate the NXT.

Hope that helps!

Arduino Digital Display: Count up and Serial Control

My Arduino is currently hooked up to a digital display. This is an electrical component that has LEDs arranged so that you can display a number. To display something, you turn on each LED individually in whatever configuration you like. Right now I have the Arduino hooked up to the digital display with a solderless breadboard. One output pin is connected to each LED of the display. Here is a sketch (Arduino program) to display numbers counting up from 0 to 9 (this repeats, as all Arduino sketches do).

Digital Display: Counting Up

This is a sketch that displays numbers that are sent to it from the computer. This is done through USB, but the Arduino and the computer pretend it's an old school serial hookup. You control what's sent through the serial monitor that comes with the Arduino software.

Digital Display: Computer control

I experimented with making my own functions in C with these projects. Instead of manually turning on and off the specific LEDs needed, I made a function that takes in an input number and manipulates the correct LEDs to display that number.

In the future I plan to make a library of the functions I use for the digital display. This allows one to easily include functions into a program without having to manually define them in a big long mess in the beginning.