Smart material actuators as a means of UAV flight control

Abstract

The use of piezo-ceramic actuators for UAV flight control has been shown to be effective both in the wind tunnel and in flight test. Macro fiber composite (MFC) actuators are a high strain variant of the lead zirconate titanate (PZT) actuator, and have been employed in a bimorph configuration to cause morphing camber control of aerodynamic surfaces in less than 0.5 m wingspan UAV applications. One of the challenges of operating these conformal actuators is to quantify the voltage input/displacement output relationship given hysteresis and aerodynamic loading effects. The work presented provides a framework for the practical implementation of these actuators by using both open and closed loop feedback systems for displacement control. Results are presented for thick airfoil designs where only the trailing edge is deflected using smart materials. The two main sources of non-linear behavior include dynamic pressure and actuator hysteresis, and knowledge of these parameters can be used for reasonably good open loop displacement control. Results are presented for 2-D airfoil section testing. Nomenclatureb airfoil spanwise length V free stream wind velocity L lift force D drag force β wind tunnel support angle α angle of attack A airfoil area C L coefficient of lift C D coefficient of drag c chord ρ air density TE trailing edge t time

Piezoelectric Morphing versus Servo-Actuated MAV Control Surfaces

“…The airfoil in the tests presented incorporated two 85mm x 14mm MFC bimorphs. Probst et al describe these experimental results in [27], but a summary will be included here for completeness. The lift and drag data from wind tunnel tests at 13 m/s and Reynolds number of 107,900 are presented in Figure 12.…”

“…Probst et al [27] investigated the 2-D aerodynamics of MFC morphing airfoils and the control response of such designs. This present work is a continuation of the research in MFC morphing actuation in [26] and [27], attempting to provide a multidisciplinary, quantitative comparison between morphing flight control actuation and industry-standard servomotor actuation.…”

“…An inverse hysteresis operator (IHOp) has been developed from a reduced-order model of the hysteretic behavior to accomplish this. The details of these developments may be referenced in [27]. A plot of the experimental hysteresis deflections and model fit are shown in Figure 7, as well as the linearization of a morphing actuator using the hysteresis inversion.…”

Piezoelectric Morphing versus Servo-Actuated MAV Control Surfaces, Part II: Flight Testing

“…Ohanian et al presented the first part of a comprehensive comparison between morphing and servo actuation in [5]. This present work is a continuation of the research in MFC morphing actuation from [5], [27] and [28], providing the completed assessment of MFC-based morphing versus traditional actuation methods. …”

“…In [19], Marques [27]. Probst et al [28] investigated the 2-D aerodynamics of MFC morphing airfoils and the control response of such designs. Ohanian et al presented the first part of a comprehensive comparison between morphing and servo actuation in [5].…”