generating synchro/resolver signals using NI 9269

[Tirmizi]

Hi,

i am working on developing a synchro simulator using NI 9269 in LV 2012. According to theory synchro is a three wire signal S1 S2 S3 with reference voltage R1 R2. at first i am using 26 V 400 Hz reference voltage. the equations I am implementing are as follows;

S1= - sqrt (2) * (11.8)* sin (theta + 60) * sin(wt)  eq (1)   w= ref signal frequency    11.8 = rms value for output , theta= the angle

S2= - sqrt (2) * (11.8) * sin (theta) * sin (wt)       eq(2)

S3= - sqrt (2) * (11.8)* sin (theta + 120) * sin(wt)     eq (3)

 I am generating the signals as single ended output , using three outputs A0 ,A1 a,nd A2 of NI 9269.

as per the theory I got from public domain literature it is stated that theta is the angle we want to sent over the signals S1 S2 S3. the signals are some 120 part or phase shift from each other. the synchro LINE - LINE voltage then should be

Voltage (S3 -S1) = (constant value) * sin(wt) * sin (theta)

Voltage (S3 -S2) = (constant value) * sin(wt) * sin (theta+120)

Voltage (S2 -S1) = (constant value) * sin(wt) * sin (theta+240)

 I implemented eq (1) (2) and (3) in FPGA and generate the signals from NI 9269. I use a reference signal 26 V , 400 Hz from synchro reference signal generator.

BUT when I connect all above to an angle position indicator (API) , It shows me erroneous result .

I fixed  the synchro angle theta value equal to 15 degree and API should display 15 Degree but it is not happening and it is showing fluctuating results like 100 degree  115 , 89, 67 etc.

how I achieve the correct angle position on API and what changes should I made in my equations etc to achieve it.

Regards

[RyanPoPo]

Hey Tirmizi,

Can you include your FPGA code? We won't be able to see what you may have done incorrectly without being able to see your current implementation.

Regards,

Ryan

[Tirmizi]

sorry for late reply as i was busy in another project.

i am attaching the images of my fpga code as well as parameter setting of sinewave generator block. i am also attaching the vi.

please follow the equations i have written before in my msg to have a clear picture of the attached images. waiting for your reply

[srm@viewpointusa.com]

There were several problems with your code.

the maxium of your sine generator was set to 16.  the output is integer.

change to max range.

you converted to fxp from integer

you need to use integer to fixed point cast

I added a step to provide amplitude adjustment

you had three generators when one is sufficient.  if you are tracking an excitation signal, replace the generator with that input.

i fixed up the multiply number types.

I changed the output to a test case graph so you can test this under windows and observe the correct data before compiling for FPGA

[Tirmizi]

thanks for the attachement but i am unable to open this in my LV. can you save in some prev  version like LV 11.

[Tirmizi]

sorry for the mistake for writing LV 11 , kindly read it as LV 7 or LV 8

[Tirmizi]

if you cannot send me the vi in prev version then please attach the snapshots of the vi so that i understand the problem in my vi.

[srm@viewpointusa.com]

here is a version for LV2011.  that is the best i can do.

[Tirmizi]

but what i do with the factor present in each synchro equation i am talking about the highlighted terms

S1= - sqrt (2) * (11.8)* sin (theta + 60) * sin(wt)

S2= - sqrt (2) * (11.8) * sin (theta) * sin (wt)       eq(2)

S3= - sqrt (2) * (11.8)* sin (theta + 120) * sin(wt)     eq (3)

i have seen these terms in a US PATENT document and i follow it to generate my synchro signals. can you help me in this metter. the 11.8 Is termed as rms output voltage and sqrt(2) factor is seems to convert this rms into peak to peak

[srm@viewpointusa.com]

you might have two questions here.

the code that i posted does exactly what your equations describe except the hardware will not produce the amplitude of your signal.  The software has an amplitude factor that can be used with external voltage amplifier to acheive the required physical voltage levels.