I can give the following description to the problem, but I don't specifically know what should be done to drive an actuator (specially a piezoeelctric one) in its resonance frequency using a feedback. **The sensor consists of a piezoelectric transducer and a vibration pickup. When an alternating voltage is applied across its electrode the piezo element is able to vibrate freely in the direction of its length. The pickup detects a vibration that is generated in the PZT element. As the amplification is increased in this system, and since the pickup transducer detects this frequency and feeds a small alternating signal to a driving amplifier, the feedback circuit system oscillates at the resonance frequency Hence, the driving amplifier always drives the PZT element at its resonance frequency. I'm very good with block diagrams, and formulas, and algorithms, in comparison to descriptions. Therefore, I would really appreciate it if you can give me your professional feedback.