Timeline for Choosing Drive Signals for System Identification?
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
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| Nov 3, 2014 at 8:33 | comment | added | P3trus | What if I know the model, e.g. First Order plus Deadtime and like to estimate the parameters. Is the correllation approach still the way to go? | |
| Apr 21, 2012 at 15:53 | history | edited | Dilip Sarwate | CC BY-SA 3.0 |
corrected typo, added processing gain connection
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| Apr 21, 2012 at 14:06 | comment | added | Jason R | What does the Bode plot of your system look like? If you have poles at 100 Hz, then you'll have significant rolloff by the time you get to 1 MHz. Just one pole at 100 Hz, at 20 dB/decade, would yield attenuation of -80 dB at 1 MHz. It gets worse if you have more poles, but the effect is mitigated somewhat if you have zeros that "hold up" the magnitude of the frequency response over that interval. | |
| Apr 21, 2012 at 3:15 | comment | added | Jason S | I understand that, but I have an ADC with limited resolution. | |
| Apr 21, 2012 at 1:35 | comment | added | Dilip Sarwate | (continued) or the reason why one averages measurements of a parameter: the sample mean has variance lot smaller than an individual measurement/sample because the signals add while the noise variances add and so the standard deviation of the noise goes down by a factor of $\sqrt{n}$. Same effect is helping here. | |
| Apr 21, 2012 at 1:31 | comment | added | Dilip Sarwate | @JasonS It is not the response of the system to the input that is directly of concern but the cross-correlation of the input and output which has to be computed over long period of time. So even if the output signal is buried in the mud as you call it, it does not matter: that long period of integration/summation gets all the signal components to add coherently and the noise to add incoherently. Think of spread-spectrum where the signal is buried in the noise (useful for covert communication) and the processing gain pulls the signal out (continued) | |
| Apr 20, 2012 at 22:16 | comment | added | Jason S | response of 1MHz pulses would be so far down in the noise floor I'd never be able to sense them. | |
| Apr 20, 2012 at 22:15 | comment | added | Dilip Sarwate | What would the response of your system be to a 1 MHz pulse train? The "impulses" in the PRBS idea are $2T$ wide at the base and $ANT$ tall, and so $T$ should be small enough that this looks reasonably enough like an impulse to the relatively slower system, while $N$ should large enough to get a tall spike. | |
| Apr 20, 2012 at 21:49 | comment | added | Jason S | So it's pretty clear from your answer that you want to make N large. But how do you pick T? I mean a 1MHz chip rate on a system with poles in the 1-100Hz rate seems like a bad idea. | |
| Apr 20, 2012 at 21:27 | history | answered | Dilip Sarwate | CC BY-SA 3.0 |