Samstag, 23. Oktober 2010

Sending Data over the Network --> First Success

So I figured out that Processing has a network library. Its a step in the right direction. Raises the question weather this can be used for sending data via the Internet. Probably not. Actually, yes it can :-) But hey. One step at a time

Enjoy the clip:

Some Pictures of new Prototype in Action

Connecting Thermoplast to Sensors

(I will comment on these later. Right now I just want to upload these so I can fool around with some new stuff.)

Turbocast: Low Temperature Thermoplast (Streifeneder)

A couple of days later I received a parcel from Streifeneder with some of the 'Turbocast' which they produce.

Turbocast was much more difficult to mold. It stuck glued to my tools. It glued to the hair on my hand, which was sort of painful ... (I ended up shaving my hand before continuing experimenting with Turbocast). Somehow this material just felt more stubborn than Apolit.

However, eventually I got used to the material and was able to get some decent results out of it. More on that topic soon.

Apolit: Low Temperature Thermoplast (Minke Props)

A couple of days ago a received a sample of Apolit, a low temperature Thermoplast by Minke Props.

First off, I have to say that I love this stuff. Where it not rather expensive, I would buy a ton of it...

It was quite easy to mold, I did not burn myself, nor did it pull out any hair after having hardened on my hand. If you need material for instant prototyping this is very interesting stuff.

Take a look at how my first encounter with Thermoplast went.

If you toss it into boiling water it turns soft and transparent in under a minute. I assume you could also bake it in the oven, though it would definitely need a much higher temperature. I was a bit worried that this material might melt if left in a car or something. However I think that would require very, very high temperatures (not saying these are impossible) as air is not all that good in transporting heat. I think its really the fact that water 'transports heat' so well which makes this work so effortlessly.

If you don't like the way its molded, just throw it back into the water. It will go back to its original (flat) shape and become moldable again.

Cutting it is no big deal, however if you use thicker material that could be a pain. I figured this out later, but obviously if you cut it while its still soft. A knife or scissors would go through it like butter.
I also tried sanding it, which did not work very will. Sanding it feels like rubbing an eraser on paper. Carving it with a sharp knife works better. Sawing it should work fine.

I added some self adhesive Velcro. This works sort of fine, but if you want something really permanent, you may want to additionally secure it with screws or something. 

By the way. I hope to soon receive a ton of sensors by images. This 'wristband' will then be used for mounting the stretch sensors for measuring arm rotation. More on that in a later post thought.

Freitag, 15. Oktober 2010

Getting better aquainted with the Stretch Sensors

As mentioned in a previous post, I now have a stretch sensor by Images in my possession. Though I was first a bit skeptical I am beginning to see more and more ways of using this. I sort of had a hunch that the relationship between stretch and resistance might not be linear (yeah admitted, nothing strange in that, I would be more surprised *where* there a linear relationship.)

I am a visual person and I need to see things to understand them, so I made these graphs:

Stretched to 125 % of original length.

Stretched to 150 %

Stretched to 175 %

Stretched to 112.5 %, 125 %, 137.5 %, 150 %, 162,5 %, and 175%

Stretched with incrementions of 6.25 %

Due to the fact that I am lazy the graphs might be a bit confusing to read. The x-axis represents time and the white vertical lines represent seconds (I just double checked my math and the white lines are more like half seconds - maybe I will redo these if I get around to it. However you still get the generally picture). The y-axis measure the change in resistance. The light gray area is the resistance of the sensor. I did not add units, as the interesting part is the relative change and that is all I measured. 
The fact that the signal is non-linear can, with some tinkering, be used as a bonus. The resolution in the first couple percent of stretch is quite high - so if I where to use two stretch sensors simultaneously but in opposite phase (if one is loose, the other one is stretched) I should be able to maximize the resolution available :-)

Feedback Circuit - Signal Flow

Had a productive meeting with the other PEERS / Research Based Learning people. I finally feel like I have an overview of all the different areas I have to tackle for this. I like making graphs to sort my ideas: This roughly represents the feedback loop which I hope to create.

Mittwoch, 13. Oktober 2010

Putting the Pieces together

Well… of course I did not sit down to do my readings for UCM as I had planned. Instead I made another video demonstrating how flex and stretch sensors can be combined. Together with the potentiometers I basically have all the sensors I need now. I hope I will be receiving Thermoplast some time this week to build a stable frame for all this tech which is, as of now, sort of floating around..

Ok. Here goes the video:

Images Stretch & Flex sensor

(scroll down a bit to go directly to the videos.)

As I said, I received two sensors by images the other day. A flex sensors and a stretch sensor (find documentation here and here. Unlike a potentiometer these do not come with a voltage divider to simply measure the resistance, so I had to go about constructing my own. Basically what I did was put a resister between ground and the sensor and attached a third cable to the sensor right before where I attached the resister. (The same way as you would do it for a photo-resistor or any other resistive sensor i guess...)

Here are some pictures of the first readings I took with the flex sensor:


and bent:

I then went about to see if I could actually use them as I hoped. (The flex sensor for measuring the hands clasp and the stretch sensor for measuring wrist rotation)

Here's an image of my flex-sensor-glove setup:

And here are videos of both flex and stretch sensors in action:

I am a bit worried that the signal from the stretch sensor might be too weak, but I believe I can improve this when I actually go about constructing the whole thing (I might not be using the optimal resistor in the voltage divider and have to experiment with location of the sensor etc.)

The flex sensor/glove combo works so well that I've had everyone who comes close to my room wear it and try it out for themselves :-D

Freitag, 8. Oktober 2010

As they dont give me my own NAO...

Well, I built myself an arm-robot. This is basically just a post to show you some pictures. Once this is posted I'll start experimenting with flex and stretch sensors (just got them in the mail, yesterday :-D...) So there will be a more substantial update soon.

off topic --> Skiing & The Acceleration of Time

Another thing I was looking into was sports. I just have this vague memory of seeing some Austrian guy winning the slalom world championship in the 50's even though he had to track back for a second as he almost missed a gate.

As we all know, that does not really happen anymore today. (Missing gates: yes. Missing gates, backtracking and winning: nope.)

So I got myself the finishing times of the best 6 skiers in all World Championship and Olympic slalom events. Then I plotted some graphs. I found the results quite fascinating. I will show all graphs first with regular scales and then with logarithmic scales.

  • Graph one shows the difference in time between first and second
  • Graph two shows the difference in time between the first and the average of the first 6 (I included the first in this average, which is a bit silly, I just realized, but oh well...)
  • Graph three shows the difference between the first and the sixth person to cross the finish

Whats really interesting here, IMHO is that these graphs don't look like some random development, governed by society and technological development. These graphs look more like something following a natural law.

I find the level of correlation quite spooky, to be honest. Take a look at these logarithmic charts...

The numbers in the graph is difference in time, measured in seconds.

Anyway. I would love to hear what other people have to say to the things I'm posting. I know people are reading this, and there is a comment function. Feel free to use it :-)

off topic --> Translating & The Acceleration of Time

I held a presentation on time the other day. And while doing my research I sort of got sidetracked and found some interesting things.

As I am a science fiction fan, and randomly collect books, I somehow ended up owning this book three times. Once the English original, then a translation published in the 50’s and a newer translation published in the 70’s. As this is pulp literature, my theory is that the translators are less motivated to preserve original wordings then when, say, translating Virginia Woolf. So I figured that comparing the two German versions of the book might give some interesting information on how language had developed in those 20 years.

Take a look yourself, here is the first paragraph in all three versions.

Farmer in the Sky by Robert Heinlein - 1950

Our troop had been up in the High Sierras that day and we were late getting back. We had taken off from the camp field on time but Traffic Control swung us 'way east to avoid some weather. I didn't like it; Dad usually won't eat if I'm not home.

50 Words, 196 Characters - 1950


Pioniere im Weltraum (Gebrüder Weiß, 1951)

An jenem Tage war unser Trupp hoch oben in den Sierras gewesen, und wir kehrten mit Verspätung zurück. Wir waren pünktlich vom Lagerfulgplatz gestertet, erhielten aber vom Flugüberwachungsdienst die Weisung, nach Osten auszuweichen, weil wir sonst in schlechtes Wetter geraten würden. Das paßte mir gar nicht; Dad ißt nämlich nicht, wenn ich nicht da bin.

55 Words, 301 Characters – 1951


Farmer im All (Heyne, 1970)

Unsere Truppe war an dem Tag oben in der Sierra gewesen, und wir kamen spät zurück. Wir waren rechtzeitig vom Feldlager aufgebrochen, aber die Leute von der Verkehrskontrolle drängten uns wegen irgendeines Unwetters nach Osten ab. Das paßte mir nicht. Paps ißt meistens nicht, wenn ich fort bin.

48 Words, 248 Characters


Aside from the obvious difference in the length of these fragments, there is also a huge stylistic difference. Personally, I find that the second, newer version does the original more justice – so maybe it has nothing to do with language development after all, and we are just looking at a better translation. An interesting point is that while the Heyne book uses an Anglicism in its title, it refrains from using the Anglicism “dad”. I wish they would have refrained from using the word farmer as well…

Samstag, 2. Oktober 2010

University is catching up on me - any help?

I was hoping to get the communication with the Nao (or at least with choregraphe) up and running by Monday...

Well, looks like I have a ton of other things to do for university and that's not gonna happen :-(

I have not come that far yet. This is the way I understand it: Choregraphe is just a programme for stringing together individual movements. These movements are programmed in python.
So what I need to do is figure out how to read serial import with python. 

Only problem. Today is the first time I even opened a python manual. However, it seems simple enough and writing interpreted code is sort of fun. (Its like you have a super smart text editor, which talks back to you while you write...  I like it :-)..

So this is how far I got, up until now.

Physical set up:

A potentiometer attached to my Arduino on analogue pin 4.

Arduino Code:

Python Code:
(using pySerial:

What needs to happen now?

a) (easy) The '1023\r\n' needs to be translated into an integer (I guess there are some string operators, which can allow me to do it. need to look that up again.)

b) (no idea how to do that as of yet.) Within choregraphe I need to write some code which will enable me to use the integer to define the angle of the servo in the elbow of the NAO.


Who can help me?

As I said, I need to focus on other university things, and if anyone could give me some suggestions on how to go about this, it would be very much appreciated.