peak to peak amplitude comparison

My system measures the speeds of two shafts with quarature encoders. As you can see from the below graph their speeds are fluctuating (I also upload the measurement data).

I need to compare the peak to peak amplitudes of these two shaft speeds in a Simulink model (in Real-time).

I tried to find max and the min values, so I used "Find Extrama" block but it gaves error as "o find a peak the input must have three or more samples per channel".

Same error is also seen when I used findpeaks command in Matlab Function block.

Thanks in advance for any help.

Answer 1

[Daniel M]

You can't find the peak of a single data point. It is telling you to provide more data points in order for the function to work. You can use the buffer block in simulink to build-up some data points. I suggest 1 period of the oscillation, so it can capture both the max and min of the signal. Note however, that this adds a latency to your real-time model (not that it isn't still real-time in terms of throughput). I'm not familiar enough with Simulink to provide another solution.

[gigi]

Thank you Daniel, buffer block worked fine as you suggested. Now I can get some results from the blocks :).

Anyway if you have any different idea regarding to how to calculate the amplitudes it will be very appreciated.

[Daniel M]

Happy to help, you can close this issue by accepting the answer.

[gigi]

as you know, my main aim is to calculate the amplitudes and whenever l succeed with this suggestion l will accept it for sure.

[Daniel M]

Also see this

https://www.mathworks.com/matlabcentral/answers/671-calculating-the-amplitude-of-a-sine-wave-in-simulink#answer_994