Closed-Loop Control of the Resonant Flow-Structure Interaction Using PID Controllers

Abstract

Closed-loop control of vortex shedding and flow-induced vibration of a spring-supported square cylinder in cross flow is experimentally investigated. The fluid field is perturbed through the cylinder surface oscillation generated by three piezoelectric ceramic actuators, embedded underneath the surface and controlled by a Proportional-Integral-Derivative (PID) controller. Three control strategies were investigated using different feedback signals, including the turbulent flow signal measured by a hot-wire, structural oscillating signal obtained by a laser vibrometer and a combination of both signals. Investigation was conducted at the resonance condition, when the vortex-shedding frequency coincided with the natural frequency of the fluid-structure system. The flow and structural vibration were measured using particle image velocimetry, laser-induced fluorescence flow visualization, laser Doppler anemometer and laser vibrometer. It is observed that the closed-loop perturbation may lead to an almost complete destruction of the Kármán vortex street and a reduction in the structural vibration, vortex shedding strength and drag coefficient by 82%, 65% and 35%, respectively, outperforming by far an open-loop control.