Thing's I'd like to see...
Now that the NXT is shipping to some of you, I'm hoping to start receiving pictures, videos, programs, and commentary on your designs. I almost wish I had another NXT kit, because most of my work with the NXT right now is for the bots that will be included in my book. This leaves me very little time for un-official bot business :)
That said, here are some of the NXT bots that I'd like to either work on or see someone else take a try at...
1. Mars Rover type bot - something that has a video camera, a claw, a soil sampler, etc... go crazy.
2. As mentioned in earlier post, alternative forms of biped (the AlphaRex is soooo January 2005)
3. NXT version of The Scribbler
Jim
That said, here are some of the NXT bots that I'd like to either work on or see someone else take a try at...
1. Mars Rover type bot - something that has a video camera, a claw, a soil sampler, etc... go crazy.
2. As mentioned in earlier post, alternative forms of biped (the AlphaRex is soooo January 2005)
3. NXT version of The Scribbler
Jim
Comments
Some of ideas I'd like to see further developed are up on a web page I posted at
http://home.earthlink.net/~xaos69/
cosine_approximation.html
--
Brian Davis
The page on triangulation is at
http://home.earthlink.net/~xaos69/triangulation.html
I got really interested in your cosine function and started to think about how improve the precision near 90 degrees and I think I came up with something:
What if we use a bezier curve formula to calculate it?
I found a very nice article about it at http://www.cubic.org/docs/bezier.htm
What do you think?
(please forgive me if I said something stupid - I'm only a curious brasilian graphic designer that is dying to grab my own NXT kit)
Yes I think it would be a good idea to search for better approximation formulas. Especially it would be good to search for formulas that are easy to implement in the limited numerical environment of 16 bit signed integers.
You can get the Excel spreadsheet I used at
http://home.earthlink.net/~xaos69/
files/Trig_Approximation.xls
The spreadsheet may help you get a head start on how to adapt a Bezier curve formula to the computational environment of signed integer arithmetic.
100,000 * cos() =
100,000 - 13 x^2 + x^4 / 12379
I updated my Excel spreadsheet to include the analysis of this formula. At first sight it appears that the two formulas are about equivalent, with Brian's providing better results for angles close to 90 degrees. The spreadsheet is available at
http://home.earthlink.net/~xaos69/
files/Trig_Approximation.xls
An interesting challange would be to mount a US sensor on motor and pan it back and forth like a radar antenna. The program should create a radar like display on the NXT LCD display. Since NXT-G has display draw blocks, this seems like a possibility - providing the blocks have inputs for variables.
How fast is the US sensor?
--
Brian Davis
y = 1 - ((x + 0.35) * x * 0.33)
It works fine between 0 and PI/2, but you must flip it every 90º in order to work until 360º as follows:
x1 = x
x2 = 3.14/2 - (x - (3.14/2))
x3 = x - 3.14
x4 = 3 * 3.14/2 - (x - (3.14/2))
y1 = 1 - ((x1 + 0.35) * x1 * 0.33)
y2 = ((x2 + 0.35) * x2 * 0.33) - 1
y3 = ((x3 + 0.35) * x3 * 0.33) - 1
y4 = 1 - ((x4 + 0.35) * x4 * 0.33)
If I'm not mistaken, the error ranges from 0 to 2%.
What do you think?