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#1 Help Me ! » Finding COS value from SIN » 2020-06-09 08:46:57

kappa_am
Replies: 1

Hi All,
I need to get COS value from SIN. what I have is COS value and I can determine which region the signal is in. I know that it is simply sqrt(1-sin^2). Since I am working on microcontroller, I need computationally efficient method. It means no SQRT. However, my DSP core has power, divide, ... simple operation like these. I would be grateful if you give me a hint.

Thank you.

#2 Re: Help Me ! » Rotation in 60°-coordination » 2019-04-15 10:16:03

Thank you Bob. smile Do you have any proof or find it by considering vectors movements?

#3 Help Me ! » Rotation in 60°-coordination » 2019-04-13 08:17:21

kappa_am
Replies: 3

Hi all,
I have been dealing with a problem, but I did not get any solution so far. I am looking for a rotation operator in 60°-coordination. A plane of a 60°-coordination is shown below.

ss.jpg

I am familiar with rotation in 90° coordination. it is (cos(θ)+jsin(θ)). I tried to modify this formula to use in 60°-coordination, but no success so far.

some examples: 60° rotation of (1,0), (-1,2), (1,-2) in 60°-coordination should yields (0,1), (-2,1), (2,-1), respectively.

I would be grateful if you share your ideas with me.

Thank you in advance.

#4 Re: Help Me ! » 60-coordination » 2018-08-26 13:25:40

Hi,
Could you please tell me what is operant 60° counterclockwise rotation in this coordination? for example, J is operant of 90° rotation in 90° frame which is exp(jπ/2). I convert 60° rotation in 90° frame to this frame by using the equation we talked about. but I did not get correct answers.

I would be very thankful if you give me hint on this subject.

#5 Re: Help Me ! » 60-coordination » 2018-06-27 05:10:29

Completely understood.

Thank you smile

#6 Re: Help Me ! » 60-coordination » 2018-06-24 17:35:45

Dear Grantingriver,
Actually, I have Ph. D in electrical engineer, and like to use this theory in the switching of a converter. I think plain and spherical trigonometry can help me, because in future I may extend this work to 3D switching. I know basics of trigonometry like solving trigonometry equations, some formulas of equivalence, etc all the subject we studied about trigonometry in university. However, generalized trigonometry was totally new to me.  From physical facts, I extracted following equations after posting this thread.
D=√3*v*sin(θ)
H=√3*v*cos(θ+30)
There may be a 3/2 or 2/3 coefficient difference between these and your formulation but it is ok. It depends on voltage vector definition. I really astonished how math matches physical phenomena. thank you again for making me familiar with this subject.
Could you please send me the derivation of these formulas, I also will read the book you refer me to.


thank you again for taking your invaluable time and helping me.

#7 Re: Help Me ! » 60-coordination » 2018-06-24 12:28:52

It helps a lot. Thank you very much. could you please introduce me a reference about this subject. I'd like to go deep into that.

#8 Help Me ! » 60-coordination » 2018-06-23 06:15:24

kappa_am
Replies: 8

Hi All,
I have a question about decomposing a vector on a 60°-coordination.  In 90°-cordination, it is easy and we are familiar with that. In X-axis direction is |V| cosθ and in Y-axis direction is |V|sinθ. What about 60°-coordination? is there any equation by which we find compositions of a vector in 60°-coordination? For more information, I have shown a 60°-coordination below.

Thank you


ss.jpg

#9 Re: Help Me ! » S-shaped function » 2016-04-28 11:06:19

Hi Bobbym,
Something like this picture.
http://i60.tinypic.com/2ykbz2v.png
I'd like to have a numerical formula by which I can define a desirable S_shaped curve (desired minimum, maximum, slope).

Thank you

#10 Help Me ! » S-shaped function » 2016-04-28 09:26:07

kappa_am
Replies: 3

Hi fellas,
I need an S-shaped function whose starting point (t), steepness, starting value(y1), and end value (y2) can be adjustable.
I would be grateful if you provide me with a numerical solution or a formula.

Thanks

#12 Re: Help Me ! » Discrete mathematics » 2016-01-10 19:30:40

for example suppose my set is 1 1 2 2. if second switch fails the set turn to 1 3 2. there is 1 switch less than or equal to 2^0, two switch LE 2^1 and 3 switches LE 2^2. so first condition is satisfied. Second condition is also satisfied. So, it works.
Now, suppose third switch fails; the set will be 1 1 4. there is 1 switch LE 2^0, two switch LE 2^1 and 3 switches LE 2^2. so first condition is satisfied. But since 4>6/2. this series cannot provide all levels ( numbers between 1 to 6).

Since I have develop this method by thinking and try&error, I am not sure about it. Please inform me if this method has any defect. Thank you

#13 Re: Help Me ! » Discrete mathematics » 2016-01-10 17:16:01

I kid of thinking of a solution. Lets suppose my system has M modules. each with voltage Vm. I think the system can maintain its functionality if the following conditions are true. I am not sure, please confirm.

1- for every K ( K is a number from 1 to M), there are K number of switch with weight less than 2^K
2-weight of the next switch to the failed switch, after adding weight of failed switch weight to it remain less than half of the summation of all members.

Does it work?
I am afraid, but I do not know what SE stand for.

#14 Re: Help Me ! » Discrete mathematics » 2016-01-10 16:47:02

yes. means the system has up to 25 sub-modules.

#15 Re: Help Me ! » Discrete mathematics » 2016-01-10 13:49:45

up to 20-25. However, a general formula is more desired.

#16 Re: Help Me ! » Discrete mathematics » 2016-01-10 11:55:23

actually this is a fault tolerant inverter, in which if a sub-module failed. the other modules try to maintain the performance using appropriate control. This is first step to examine that the remained operating circuit can compensate loss of that sub-module or not. Therefore, yes, simple as much as possible.

#17 Re: Help Me ! » Discrete mathematics » 2016-01-10 11:24:31

it is MOSFET, controlled by micro controller.

#18 Re: Help Me ! » Discrete mathematics » 2016-01-10 09:38:46

No, they can be any  positive integer number. But the failed switch is discriminated (provided by fault diagnosis system).

Enjoy your meal

#19 Re: Help Me ! » Discrete mathematics » 2016-01-10 09:05:58

We have a series in which each number is per-unit voltage of a inverter. We have several inverters connected series to each other generating output voltage ( it look like a staircase waveform). for example 1, 1, 2, 2 means I have 4 inverter 2 with voltage 1V (per-unit) and 2 with 2V. by this inverters I can produce voltage levels from 1 up to 6. suddenly one of the inverters fails. the connection is in such a way that weight of the failed switch transfers to upper switch. suppose the third switch fails the series turns to 1, 1, 4. first I have to examine that am I able to generate all levels or not. then proceed to appropriate program. in this case I can not generate all levels. Because there is no way to generate 3.

Thanks for all your helps

#20 Re: Help Me ! » Discrete mathematics » 2016-01-10 08:47:54

dsPIC30F4011. What I need is that I have to ensure that by existing number, all numbers up to summation of all members can be construct. no need to find specific number. There has to be a simple rule.
like the next number in the series be less than summation of the previous numbers. I thought a lot, but every way has a defect!!

P.S I need the answer (yes or no) in less than 10us.

#21 Re: Help Me ! » Discrete mathematics » 2016-01-10 08:31:17

I got it. Thank you. math is always fascinating.
I need to implement this method to control a procedure (physical). It seems this requires heavy computation. Do you have any recommendation in programming this algorithm? our micro has limited computation power and I need to have efficient algorithm.

#22 Re: Help Me ! » Discrete mathematics » 2016-01-10 06:30:31

could you explain more or introduce me a reference.
your help is appreciated.

#23 Help Me ! » Discrete mathematics » 2016-01-09 20:50:41

kappa_am
Replies: 29

Hi,
I have a question about series (some members are repeated). I have a series, How can I find out if this series make all numbers up to summation of all members. Is there any formula?

for example {1, 1, 2, 4}; the subsets of this set can construct all numbers from 1 to 8.
{0, 1, 3, 4} cannot make all numbers ( 2 and 6 cannot be constructed).

question is how determine that if a set is capable to construct all numbers up to all members summation or not. a general formula would be appreciated.

Thank you.

#24 Re: Help Me ! » Curve fitting » 2015-05-21 19:53:30

it steady on 1 after 165, I have examined over 10 points.

#25 Re: Help Me ! » Curve fitting » 2015-05-20 20:34:54

yes it comes from an experiment. least squares is ok.

thank you

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