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A novel morphing control surface design employing piezoelectric macro-fiber composite actuators is compared to a servo-actuated system. The comprehensive comparison including aerodynamics, size, weight, power, bandwidth, and reliability has been extended to include flight test comparisons. Three flight vehicles were designed, built, and evaluated: a servo-controlled generic micro-aerial vehicle aircraft and two conformal actuator controlled versions based on thick and thin wing designs. Flight agility and control response of the morphing-actuated and servo-actuated configurations were quantified through state measurement during identical automated maneuvers. The morphing actuation scheme demonstrated control bandwidth that was an order of magnitude greater than for the servo-actuated system, but showed a 12% decrease in roll rate when compared to the servo-actuated baseline aircraft. The flight vehicles allowed system-level comparisons of conventional and morphing control, where conformal actuation occupied less volume, consumed equivalent power as micro servos and provided effective control power for maneuvering.

The purpose here is to enable peak-to-peak actuation of piezocomposite devices to perform shape control of structures, specifically bimorph variable-camber control surfaces on small aircraft. One of the major drawbacks in implementing control with piezocomposite actuation is its asymmetry in the positive and negative voltage directions. To remedy this situation, a novel, solid-state electrical circuit employing diodes and resistors is proposed. The circuit allows a single bipolar amplifier to control a bimorph composed of two piezoceramic composite actuators known as Macro-Fiber Composite (MFC). The MFCs have an asymmetric actuation range of -500 to 1500 V; hence an MFC bimorph with conventional serial or parallel electrical connection limits the actuation to the -500 to 500 V range. The proposed circuit allows the division of the input voltage so that: (1) The MFC that is in extension receives 1500 V, and (2) The MFC that is in compression receives -500 V. The circuit also allows the actuation in the opposite direction without any physical changes (i.e., not using any electromechanical switches) The input-output relationship of the circuit is characterized experimentally. An MFC bimorph is used to further demonstrate the capability of the circuit.

The research presented here employs solid-state actuators for flow separation delay or for forced attachment of separated flow seen in airfoils at low Reynolds numbers. To reduce separation, periodic excitation to the flow around the leading edge of the airfoil is induced by Macro-Fiber Composite actuated clamped-free unimorph benders. An electromechanical model of the unimorph is briefly presented and parametric study is conducted to aid the design of a unimorph to output high deformation at a desired frequency. The optimum frequency and amplitude for lift improvement at post-stall angles are identified experimentally. Along with aerodynamic force and structural displacement measurements, helium bubble flow visualization is used to verify existing separated flow, and the attached flow induced by flow control. The lift enhancement induced by several flow control techniques is compared. A symmetric and non-uniform (3D) flow excitation results in the maximum lift enhancement at post-stall region at the lowest power consumption level. A maximum lift coefficient increase of 27.5% (in the post-stall region) is achieved at 125 Hz periodic excitation, with the 3D symmetric actuation mode at 5 m/s and the reduced frequency of 3.78. Cl, max is increased 7.6% from the baseline.