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This study aims to enable solid-state aerodynamic force generation in high-dynamic-pressure airflow. A novel, high-load-output, bidirectional variable-camber airfoil employing a type of piezoceramic composite actuator known as a Macro-Fiber Composite is presented. The novel airfoil employs two active surfaces and a single four-bar (box) mechanism as the internal structure. The unique choice of boundary conditions allows variable and smooth deformation in both directions from a flat camber line. The paper focuses on actuation modeling and response characterization under aerodynamic loads. A parametric study of aerodynamic response is employed to optimize the kinematic parameters of the airfoil. The concept is fabricated by implementing eight Macro-Fiber Composite 8557-P1-type actuators in a bimorph configuration to construct the active surfaces. The box mechanism generates deflection and camber change as predicted. Wind-tunnel experiments are conducted on a 12.6% maximum thickness, 127 mm chord airfoil. Aerodynamic and structural performance results are presented for a flow rate of 15 m/s and a Reynolds number of 127,000. Nonlinear effects due to aerodynamic and piezoceramic hysteresis arc identified and discussed. A lift coefficient change of 1.54 is observed purely due to voltage actuation. Results are compared with conventional, zero-camber NACA and other airfoils. A 72% increase in the lift-curve slope is achieved when compared with a NACA 0009 airfoil. DOI: 10.2514/1.45452

Actuator disk models are commonly used for the analysis of rotary wing systems. The blade-element momentum model is probably the most popular one because of its simplicity, efficiency, and good accuracy in many cases. Yet momentum models fail to give satisfactory results in many other cases. The reason is probably the tact that momentum models include a basic assumption that the integral form of the equation of conservation of momentum can be replaced by its differential form. This paper presents a new actuator disk model that does not include the aforementioned assumption. It is assumed that the pressure difference between both sides of each point of the disk is a time average of the pressure difference between both sides of the blade elements that pass through that point. In addition to calculating the axial components of the induced velocity through the disk, the solution procedure also includes calculations of the radial component. The new model includes an iterative solution procedure that converges relatively fast and requires relatively small computing resources and short computing time. The paper describes the new model, presents the solution procedure, and compares the new results with known results from the literature. DOI: 10.2514/1.37383

We present the results of a series of measurements in which an array of capacitive V-dot probes are used to determine the surface potential in a single dielectric barrier discharge plasma operated as an aerodynamic plasma actuator. From these measurements, we determine the longitudinal electric field in the plasma. The results show that the surface immediately (within the first alternating current cycle of the plasma discharge) acquires a net positive surface charge, so that the electric field in the plasma is asymmetric, the magnitude of the maximum field being more than 50% larger in the negative than the positive polarity. The measurements also show that there is a region several millimeters downstream from the exposed electrode edge over which the electric field maintains a constant positive (downstream) polarity over the course of the discharge cycle. DOI: 10.2514/1.33973

DOI: 10.2514/1.28933 Reduced-size aeroservoelastic equations of motion are constructed and used for stability analysis and maneuver simulations with control-surface actuator nonlinearity caused by free play. A linear modal-based state-space aeroservoelastic formulation is expanded to address the nonlinear actuator stiffness characteristics by means of nonlinear feedback loops. The fictitious-mass method is used to accurately account for the actuator stiffness changes during simulations. The direct-force modeling approach is found to be more suitable for representing the stiffness-actuation mechanics than the control-mode approach. A modal-based aeroelastic trim analysis algorithm that takes into account the actuator free play is used to determine the initial aeroelastic states of the aircraft in a steady flight. Symmetric and antisymmetric normal modes of an unmanned aerial vehicle model with disconnected actuators are combined for asymmetric aeroservoelastic time-domain equations of motion with nonlinear actuator effects and full control-system dynamics. Simulations of the complete aircraft structural dynamic response to maneuver commands exhibit asymmetric limit-cycle oscillations when one of the actuator forces changes sign.

An adaptive algorithm applied on a digital signal processor was utilized in conjunction with an analog multiplier circuit to compensate for the feedthrough capacitance of piezoelectric sensoriactuator. The mechanical response of the piezoelectric sensoriactuator was resolved from the electrical response by adaptively modifying the gain imposed on the electrical circuit utilized for compensation.

The optimum placement of a piezoelectric sensor/actuator verifies the vibrational control of laminated composite beams. The finite element analysis reveals the structural characteristics of the beams. The interaction between sensor/actuator and the structure changes the mass, damping and stiffness of the whole structure. The modal damping defines the structural damping index (SDI). The maximum value of SDI corresponds to the sensor/actuator. The SDI depends upon the outer layer fiber orientations of the host structure.

The authors examine methods of optimum structure and control systems design. Topics include structural analysis, frequency responses, and actuators .

A theoretical method uses internal translational actuators to regulate static shapes of flexible structures. Finite element analysis of an adaptive rib model demonstrates the efficiency of the method in providing a close fit to any desired shape. Open- and close-loop studies of unloaded and loaded structures, respectively, help produce commanded shapes. The method, on application to the problem of keeping maximum airfoil shapes, reduces wind drag.

Actuator/substrate thickness ratio of three actuator-structure complexes attached to various regions of the substrate maximizes the strain induction and moment-induced curvatures in the substrates under external loading. The thickness ratio is a function of actuator activating level and boundary conditions and influences the response of the actuators to various parameters.

A Rayleigh-Ritz panel flutter model analyzes the effectiveness of actuator material integration in the structure and its ability to control panel deformation and increase panel flutter speeds. In-plane panel forces effectively control panel flutter. The test panel is flat and rectangular, and actuator materials include piezoelectrics and shape memory alloys.

A high-order linearized model of helicopter flight dynamics, with rotor, inflow and actuator dynamics, was created, and a new tin algorithm which precisely computes the steady-state response of the rotor blades was developed. The algorithm can be used with straight flight and steady coordinated turns. Numerical perturbations of a nonlinear, blade element-type mathematical model form the basis of the flight dynamics model. The firm algorithm is precise and maintains the periodic nature of the aircraft states.

A new method for the design and placement of piezoelectric sensors uses feedback control for panel flutter limit-cycle suppression. The shape and location of the sensors depend on the control feedback gain. The use of a constant gain direct feedback controller provides an optimal control performance. A numerical simulation of sensors shape using this technique demonstrates the panel flutter suppression. The design of the actuator, position and rate sensors is presented.