At 10:11 PM 10/20/2005, Neil wrote:
>Wow, that's great info Robert, thanks. Actually, you reminded me that
>it's not as simple as I first described, because I will be including a
>temperature sensor on the VCXO. But you've given me a great start, and
>I'll get that working before I try to get it to compensate for
>temperature as well.

Another ad hoc control algorithm is a digital version of a PID controller. 
Just use a forward difference for the derivative and an Euler sum for the 
integral.

So long as the update frequency is fast enough, the system will be stable. 
If not, you would have to implement an implicit scheme with backward 
difference for the derivative and trapezoidal rule for the integral, and 
solve the implicit equations. (In EE terms, infinite impulse response.)

Again, a Kalman filter is most useful when you know a good differential 
model for the plant dynamics. Otherwise an ad hoc filter/tracker is 
typically used.

================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ral@lcfltd.com
Least Cost Formulations, Ltd.            URL: http://lcfltd.com/
824 Timberlake Drive                     Tel: 757-467-0954
Virginia Beach, VA 23464-3239            Fax: 757-467-2947

"Vere scire est per causas scire"
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