Calculating Period for Signal's Waveform

Hell Experts,

I need sugestions on calculation of time period for different parameters of my motion sensor like ROLL, PItch, Heave etc. Currently I am using method of zero crossing for calculating the period of signals. Period is calculated using number of zero crossings. I am using timer and counters for that purpose, once the signal value cross zero and enters negative region counter increments again when it crosses zero crossing to go into positive region counter increments. But now I am looking at a case when my signal waveform never crosses zero value and remains in positive region always or negative region then in that case how can I calulate the period of my signals' waveform. Any ideas will be appreciated, if someone has implemented such scenario then please help me with this!

I have attached another function that is outputting the period of signal after each complete cycle.
Please suggest how can I do the above two scenarios when there is no zero crossings. Hope now you have a clearer picture of what I intend to achieve.

Please suggest asap!

Thanks in advance!

Welcome to the forum.

If you are satisfied with your zero-cross method you could try this:

Make a slow lowpass or a mean value of your input value.
When the input value crosses this mean value, do the counting.

Kalle

Can you estimate the velocity or rate of change in the Roll, Pitch and Heave? The 'zero crossing' occurs when the velocity is the highest. You could also use the time between the maximum and minimum reading. This isn't very accurate though. I have more sophisticated techniques but they would be tough to implement in a PLC.

An FFT will provide the frequency/period and magnitude but good luck with that on a PLC.

KalleOlsen said:

Welcome to the forum.

If you are satisfied with your zero-cross method you could try this:

Make a slow lowpass or a mean value of your input value.
When the input value crosses this mean value, do the counting.

Kalle

Click to expand...

Thanks a lot for your suggestion! can you elaborate how can I implement your suggestion in my code attached in my first post!

Peter Nachtwey said:

Can you estimate the velocity or rate of change in the Roll, Pitch and Heave? The 'zero crossing' occurs when the velocity is the highest. You could also use the time between the maximum and minimum reading. This isn't very accurate though. I have more sophisticated techniques but they would be tough to implement in a PLC.

An FFT will provide the frequency/period and magnitude but good luck with that on a PLC.

Click to expand...

Thanks Sir,

I thought of a logic to calculate the timer period without using the ero crossing or sign concept. Please look at the attached picture for understanding. However I need help in implementing that logic in the PLC Programming. I also want suggestions on how can I do comparison between current and previous values?


Thanks!

syedkhyzeraliabidi said:

Thanks Sir,

I thought of a logic to calculate the timer period without using the ero crossing or sign concept. Please look at the attached picture for understanding. However I need help in implementing that logic in the PLC Programming. I also want suggestions on how can I do comparison between current and previous values?


Thanks!

Click to expand...

The rate of change is very fast however its difficult give an exact estimate!