Dear Lazaros,

Good day,

The Nyquist / Shannon or Shannon (as they call it) sampling theorem states that we must sample at a frequency at least twice the bandwidth of interest, but it is clear here that we must sample at a much higher rate with this approach.

Conventional wisdom among control engineers gives a “rule of thumb” that

we can probably ignore the error introduced by the discrete approximation to

the continuous controller if:

1/T > 30 x the bandwidth of the system, Where T is the sampling time.

To obtain the bandwidth, you either draw bode plot and get -3dB frequency which is the bandwidth frequency (that is required here).

please, see the following article.

Hello,

It has been almost thirty years since Shannon introduced the sampling theorem to communications theory. In this review paper we will attempt to present the various contributions made for the sampling theorems with the necessary mathematical details to make it self-contained.

You can find a complete tutorial at:

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1455040&url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F5%2F31259%2F01455040.pdf%3Farnumber%3D1455040

Dear Mr. Tahir.

Thank you very much for your answer. I had some trouble in the beggining with understanding the bandwidth and how to compute it, but thanks to the link you uploaded I understood it nicely! So thank you for your time!

My initial approach was to simply convert the natural frequency of the system (given in rad/sec) to Hz, and then apply rule of thumb and choose the sampling frequency to be 10 times faster. But this paper explains the procedure more thoroughly!

Dear Mr Gerson

Thank you too for your answer. If you would be kind enough to send me a copy of your conference paper i would be grateful, because I do not have access to all the IEEE explore conferences.