Closed-Loop Control of a Piezo-Fluidic Amplifier

Fluidic valves based on the Coanda effect are increasingly being considered for use in aerodynamic flow control applications. A limiting factor is their variation in switching time, which often precludes their use. The purpose of this paper was to demonstrate the closed-loop control of a recently developed novel piezo-fluidic valve that reduces response time uncertainty at the expense of operating bandwidth. Use is made of the fact that a fluidic jet responds to a piezo tone by deflecting away from its steady-state position. A control signal used to vary this deflection is amplitude modulated onto the piezo tone. Using only a pressure measurement from one of the device output channels, an output-based linear quadratic Gaussian regulator was designed to follow a desired reference deflection, achieving control of a 90 m.s(-1) jet. Finally, the controller's performance in terms of disturbance rejection and response time predictability is demonstrated.