Structural Control Using Analog Phase-Locked Loops

Abstract

A study of the application of the phase-locked loop (PLL) to modal control of mechanical structures is performed. An analog PLL circuit is used to control the vibration of a cantilevered beam with piezoelectric sensors and actuators. By using the PLL controller, strain rate feedback is provided within a narrow and distinct frequency range about the fourth mode of the beam. The controller ignores all other modes and does not affect the phase outside of the frequency range. The PLL controller provides a simple, inexpensive, and effective method to control an individual structural mode or set of modes without causing spillover.