<title>Experimental study of active control of wave transmission through hollow cylindrical struts</title>

Abstract

Experimental investigations conducted into active control of longitudinal waves transmitted through a hollow cylindrical strut are presented in this article. Following along the lines of our previous work, an active strut of finite extent length, instrumented with sensors, piezoelectric, and magnetostrictive actuators, is studied in the frequency range of 10 Hz to 2 kHz. Single and multiple actuator arrangements are employed in open loop control investigations, and the effectiveness of the control effort in minimizing longitudinal harmonic disturbances transmitted through the strut is experimentally investigated. Initial efforts towards development of feedforward and feedback boundary control algorithms for reducing longitudinal vibratory loads in finite length cylinders is also presented. For the feedback controller development, the strut-actuator ensemble is modeled by using the one dimensional wave equation and the direct method of Liapunov is used. The feedforward control algorithm is based on the previous model of the active strut and relies on measurements of axial strains and accelerations at the strut ends. The influence of the boundary conditions and static forces applied to the strut are also investigated. The relevance of the current work to control of structure-borne helicopter cabin interior noise is also discussed.