I have a rotating shaft where I need to move from the time domain to the angular domain to look for vibration faults. I have the data from a tachometer.
From another post I found these steps:
The steps involved for time domain --> Angle domain are:
- Use the tachometer signal to obtain a speed signal. This is the inverse of the difference in time for each trigger point.
- Depending upon the variability of the tachometer signal least squares cubic spline fitting is often used. Matlab spline library will work as will matlab central libraries. I use the fastBspline library.
- Integrate the speed signal to obtain shaft angle position.
- Determine the equal angle increments that you want to use. Keep the Nyquist theorum in mind, in other words there should be roughly the same number of points in the angle domain as in the time domain.
- Switch the (time, angle) data to (angle, time). Resample the (angle, time) data to obtain uniform angle increments. Once this is done, do all the same processing you would have done, but now you are in the angle order domain.
In regards to step 2: What is returned if I integrate the speed signal (which is an array)? Surely that would not be a function or an array?
In regards to step 5: Why is it necessary to change from (time, angle) to (angle,time)? How is this plot related to the original vibration signal (time, acceleration)?