How to obtain Transfer Function from Scope Data?

I have a scope data of gyro output for a range of frequency (0.5Hz-20Hz) obtained using system identification toolbox. I want to obtain a transfer function for the gyro output. Should I generate a bode plot for the data to obtain the transfer function? Am i supposed to use the idfrd function to obtain bode plot?

Answer 1

[Sebastian Castro]

The idfrd function is a start, as that will package up your collected data into an "experiment" of frequency vs. complex response data.

The next step would be to estimate the transfer function using that data, with functions like tfest.

Here is the general documentation page for all things transfer function in System ID Toolbox.

- Sebastian

[meghana madhusudhan]

thank you sebastian.

I tried the following code and obtained a transfer function for my scope data.

tfdata=iddata(input,output,t); N=2; sys=tfest(tfdata,N); bodeplot(sys)

the numerator of my transfer function is a negative number. does it make sense?

I need to use the obtained transfer function to design a PID controller.

Answer 2

[meghana madhusudhan]

thank you sebastian.

I tried the following code and obtained a transfer function for my scope data.

tfdata=iddata(input,output,t); N=2; sys=tfest(tfdata,N); bodeplot(sys)

the numerator of my transfer function is a negative number. does it make sense?

I need to use the obtained transfer function to design a PID controller.