Timeline for How can I plot the frequency response on a bode diagram with Fast Fourier Transform?
Current License: CC BY-SA 4.0
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| Apr 19, 2020 at 20:30 | comment | added | euraad | Great! Thank you for that answer. By the way! I have made OCID now and included more litterature about it. Very hard to find. Check out mataveid. I need some help with ERA/DC and OCID. | |
| Apr 19, 2020 at 3:26 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 19, 2020 at 3:12 | comment | added | Dan Boschen | Let us continue this discussion in chat. | |
| Apr 19, 2020 at 3:09 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 19, 2020 at 2:45 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 19, 2020 at 2:16 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 19, 2020 at 2:08 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 19, 2020 at 1:19 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 19, 2020 at 1:07 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 18, 2020 at 18:27 | comment | added | euraad | Wrote a message for you in the chat. I'm done with SSFD. Now I'm going to work on OCID. | |
| Apr 17, 2020 at 14:45 | comment | added | euraad | To create OCID, I need to work on equaton 16 to equation 26 | |
| Apr 17, 2020 at 14:44 | comment | added | euraad | pdfs.semanticscholar.org/2320/… | |
| Apr 17, 2020 at 14:43 | comment | added | euraad | That report is OCID. It's estimate a control law (LQR) + kalman filter + model of measurement data. Very easy. I can help you understand it. Very equal to okid.m in Mataveid | |
| Apr 17, 2020 at 14:42 | comment | added | euraad | You're welcome to contribute to Mataveid. I have a report named "Identification of System, Observer, and Controller from Closed-Loop Experimental Data". Created by the same author for ERA/DC and OKID. He is the guy who made hubble and space craft Galeleio work. | |
| Apr 17, 2020 at 14:41 | comment | added | Dan Boschen | Cool- I would definitely post that as a new question then in particular for a case where a strong white Gaussian noise is present and see what other good answers may come up (then add yours there too). It would be very interesting and would help draw attention to Mataveid if it out-performs all other approaches offered. | |
| Apr 17, 2020 at 14:40 | comment | added | euraad | That's good too. I'm also into embedded systems. Writing OKID and ERA/DC into pure C code for embedded systems such as STM32. | |
| Apr 17, 2020 at 14:39 | comment | added | euraad | I have methods like N4SID and MOESP as well. But they are sensitive against noise. | |
| Apr 17, 2020 at 14:39 | comment | added | Dan Boschen | nice - I use normalized angular frequency for digital systems so the time unit is in samples and $\omega$ then always goes from $0$ to $2\pi$--- it eliminates having to deal with $T$ in all the equations, especially when differentiating and integrating as it changes the scale. | |
| Apr 17, 2020 at 14:37 | comment | added | euraad | I'm working on Mataveid. It works both for MATLAB and Octave. I have done a huge research on what methods are good and what is more for studies. OKID, ERA/DC, RLS, SSFD and OCID seems to be the most used and practical methods because they are strong against noise. | |
| Apr 17, 2020 at 14:36 | comment | added | euraad | Well, in this case it's $G(z = e^{jwT})$ where $T$ is the sampling rate. Yes. I working on it. Just as a free hobby. Here is a function to estimate a discrete TF in time domain. github.com/DanielMartensson/Mataveid/blob/master/sourcecode/… | |
| Apr 17, 2020 at 14:29 | comment | added | Dan Boschen | oh, you mean given only the magnitude and phase of $G(z=e^{j\omega})$ can you determine the general polynomial $G(z)$? I have in fact experimentally in the lab on hardware for temperature control implementations. This would be a good additional question you should ask as others may have optional good approaches over what I should suggest. | |
| Apr 17, 2020 at 14:25 | comment | added | euraad | Ok. absolute value in other words. Have you tried to identify a transfer function from frequency response before? I just wondering how the results become in practice. | |
| Apr 17, 2020 at 14:24 | comment | added | Dan Boschen | No, G(z) is just a ratio of polynomials in z so the coefficients are in normal scale. When we plot the magnitude of the frequency response, specifically $|G(z=e^{j\omega})|$ we typically plot that in a dB scale | |
| Apr 17, 2020 at 14:13 | comment | added | euraad | By the way! Should $G(z)$ be in $20log_{10}$ unit? E.g dB? | |
| Apr 17, 2020 at 14:09 | comment | added | euraad | Thank you. That's a good answer. I'm going to write the SSFD algorithm from NASA now. I can give it to you later if you want. The SSFD algorithm creates a state space model (the best linear models IMO) from frequency responses :) | |
| Apr 17, 2020 at 13:48 | comment | added | Dan Boschen | It is because of equation 1 in my answer, and see the linked post for more details, but in short the instantaneous frequency is the derivative of the phase, and for your case with $cos(\theta(t))$ the phase is going at the rate of $t^2$ so that derivative gives you an extra factor of 2: d/dt of $t^2 = 2t$ | |
| Apr 17, 2020 at 12:36 | comment | added | euraad | Is it because I cut the vector in 2? | |
| Apr 17, 2020 at 12:35 | comment | added | euraad | Why does 4 work? But not 2? | |
| Apr 17, 2020 at 11:26 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 17, 2020 at 9:50 | comment | added | euraad | Thank you. Can you explain number 4? | |
| Apr 17, 2020 at 5:16 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 17, 2020 at 1:49 | comment | added | euraad | I have posted an answer. You might want to look at it :) | |
| Apr 17, 2020 at 1:47 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 17, 2020 at 0:09 | vote | accept | euraad | ||
| Apr 16, 2020 at 21:51 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 16, 2020 at 21:41 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 16, 2020 at 19:15 | comment | added | Dan Boschen | Let us continue this discussion in chat. | |
| Apr 16, 2020 at 19:14 | history | edited | Dan Boschen | CC BY-SA 4.0 |
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| Apr 16, 2020 at 18:40 | history | answered | Dan Boschen | CC BY-SA 4.0 |