resonant frequency monitor

[gjbinboston]

Good morning. I have created a program that will scan a range of frequencies and then feed the resonant  frequency to a signal generator. The problem I am having is that the resonant frequency changes with pressure. So if a pressure regulator is attached to the resonant pump, the resonant frequency may shift by 20 to 30 hertz. I don't know if it would be better to stop the generation and re-run a sweep every few seconds (ultimately that varies the pressure and does not solve the problem) or if there is some better way to dynamically shift the frequency generation with pressure. Currently I monitor the voltage and current phase difference. At resonance, this difference is at a minimum. Using an index I find the frequency that the minimum phase occurs and then feed that into a generator. Can anyone offer any suggestions on how to go about tracking the resonant frequency smoothly?

[Conseils]

You might use a PID loop to track the resonant frequency by using the phase as a reference.

Essentially the Set point for the PID is the resonant frequency phase difference that you want to maintain.

Problems that you will encounter are the PID settings and the overall loop response time.