A vibration suppression approach based on enhanced phase locked loop harmonic tracking

This article presents a novel algorithm for vibration suppression with inertial actuators. This algorithm is designed to cancel out harmonic disturbances and finds application in rotating machines like helicopters and, more in general, in structures connected to rotors, which generate a single-harmonic disturbance with a frequency far from any natural frequency of the structure. The existing control algorithms for inertial actuators are mainly designed to cancel out vibrations arising from slightly damped structural modes, so they are not suitable for this specific application, whereas the proposed control algorithm is based on the Enhanced Phase Locked Loop (EPLL), a non-linear adaptive bandpass filter originally designed to stabilize electrical systems. In this work, the use of the EPLL is extended to the vibration control of a mechanical system as it is used to track frequency and amplitude variations of the vibration acceleration and calculate the required control force to suppress it. In this article, the algorithm is described, and the parameters of the EPLL are tuned, analyzing their influence on the actuators’ performances. Numerical simulations are performed to discuss its stability, analyze its performance, and compare this novel algorithm to other existing control strategies. Finally, the proposed control algorithm is applied to a helicopter tailplane using two identical inertial actuators. The experiments have shown that the EPLL-based control can effectively cancel out single-harmonic vibrations far from the resonance and that it is robust to amplitude and frequency variations.