Thursday, March 08, 2007

[SW] MathCast-- Equation Editor

MathCast is an open and protable software (green software) for equation edition. It saves me from MathType, because I have no money to purchase MathType... Orz

Of course, you can not expect that MathCast can replace all the excellent capabilities of MathType. It is still good enough, however, for usual applications.

[SW] Maxima-- test of matrix manipulation

Wow, what a big matix...

This is my first idea when I saw the results from Maxima. I typed the matrix in textfile, then open it with Maxima. Here are some results.

You can get this result by typing

If we use invert command to inverse the previous matrix, then here is the inverted matrix

Column 1

Column 2

Column 3


I think maybe there are some tricks I have not known, or I have to do the manipulation with my hands and pencil. O__O

Saturday, March 03, 2007

[Heli] Inverted Flight Improvement

Yes, I did the really inverted flight with the T-rex 450SE!

Just in today's afternoon, I and Chih-sen went to the field for the flight. It is still quite challenging to me to inverted the T-rex. I can not pull the control stick precisely, so occasionally some kind of unexpected motion happens when the T-rex is pitched down to be inverted.

I did some ugly pitching-down manoeuvres, and it made me very tense. Suddenly, in one of the inverted flight, I can see the vehicle clearly. It became easier for me to control it, just like what I always do in the simulator!!

It is a encourage to me. Good job today!

[SW] Static local variables in Scilab

I rewrote my C code program into Scilab. When executation, however, I found there are some errors about variables undefined.

After some check, I figured out that might be the problem of "static local variables".

Here are 2 messages I found in Scilab newsgroup:
static local variables in Scilab

I don't want to use global variable declaration. It's not a good news for me that I can not declare static local variables in Scilab... :-(

Thursday, March 01, 2007

[SW] Maxima-- A Computer Algebra System


Several days ago, I was trying to derive an inverse of a 3 by 3 matrix with its mathematical symbols. It's really a tedious work. What might be worse is aftering the horrible manipulation, one can not to be sure if the result is correct!

Now, the Maxima looks like the savior. I think I would like to try it and then write down the test result.

[SW] Scilab

Scilab Homepage

I downloaded it several months ago, but haven't spend time to understand it yet.

These days I encountered some problem in my Kalman Filter C code. For 2 by 2 matrix, everything is fine. When I rewrote the program for 3 by 3 case, however, it went overflow with causes I cannot figure out... Orz

Therefore, I think it is necessary to write the code in something like Matlab. Open and free software occurred to me, and it is the downloaded Scilab.

Hope I can get familiar with it as soon as possible, or my research progress will be delayed more. :-p

Here is a homepage including informations and tutorial materials about Scilab:

Another basic tutorial: (added at 2009/05/22)
Master Scilab! by Finn Haugen

Monday, January 29, 2007

[Heli] Canopy Painting for T-rex 450SE

The original plastic white was a little boring, so I decided to add some colour on our lab's T-rex 450SE. It's the metal blue, and looks not bad. If I have more time, I think I will apply another colour, maybe the metal gray, on the bottom of this canopy.

Monday, January 15, 2007

[Heli] My 1st Inverted Flight

Date: 2007/01/11
Location: In fornt of the IAA building
Heli: T-rex 450SE

Here is the video taken by my friend with his new mobile phone:

After the 1st inverted flight, I was very excited and tense. During the 2nd trial, I pull down the collective pitch too slow and T-rex fell down... Orz

Although I crashed the helicopter, this is still a good beginning for me. I felt the true manuever with T-rex. I think I can do it better during the next flight! :-)

Wednesday, January 10, 2007

[Heli] T-rex 450SE is ready for 3D flying!

Our lab bought the T-rex 450XL last year and it has been hovered or flew in simple way by 4 members in our lab. Several weeks ago, I think it is time to upgrade our skill and of course as well as the helicopter. Based on the experience with the T-rex 450XL, the T-rex 450SE became the first (maybe the only one) choice. To purchase the T-rex 450SE, we can get information and help easily.

Because I had the assembage experience of the T-rex 450XL, I started to assemble the new coming T-rex 450SE by myself. However, I encountered some troubles in setting the servos up. The side plates are different from the T-rex 450XL. I didn't sure how to fix and trim the servos with thier arms. I had no idea about the position for the speed controller, the receiver, the battery, and so on.

Finally, I decided to ask someone who is expert in this. Siau-Chong is the one who can solve my problems. He assembled the rest parts and set everything ready.

I went to Beng-ka, a RC hobby shop, to take the T-rex 450SE back. Wow, it is really a good job! Everything was considered and settled. Even the heat-shrink tube was used to protect the cable line of servos. I never think about those details before!

Here are some pictures to show the work. For your reference if you also need some example to learn the arrangement of the 450 electrical helicopter.