Closed-loop control of a piezo-fluidic amplifier

Abstract

Fluidic valves based on the Coandă 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 is 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 LQG regulator was designed to follow a desired reference deflection, achieving control of a 90 ms −1 jet. Finally, the controller's performance in terms of disturbance rejection and response time predictability is demonstrated. Nomenclature Miscellaneous αFeed-forward gain (-) δx(t)State deviation from equilibrium (-) δx(t)State deviation estimate (-) δy(t)Output deviations from reference (-) δy ′ (t)Noisy measurement of δy (-) δy(t)Output deviation estimate (-) δu(t)Control input deviation from equilibrium (-) Φ yu (ω) Output-input cross-spectral density (dB/Hz)

Novel Operating Mode of a Fluidic Oscillator

“…Fluidic actuators have the potential to overcome these challenges, with recent studies making strides into understanding their operation and improving bandwidth and authority limitations [14][15][16]. Switching time uncertainty is addressed by Nicholls et al [17] through the use of closed-loop control. Since they contain no moving parts, fluidic devices do not suffer from wear and therefore require less maintenance.…”