A method for controlling a flying projectile which rotates during flight, comprising: determining an angle of rotation of an inertial mass spinning about an axis during flight; and controlling at least one actuator for altering at least a portion of an aerodynamic structure, selectively in dependence on the determined angle of rotation and a control input, to control aerodynamic forces during flight. An aerodynamic surface may rotate and interact with surrounding air during flight, to produce aerodynamic forces. A sensor determines an angular rotation of the spin during flight. A control system, responsive to the sensor, produces a control signal in dependence on the determined angular rotation. An actuator selectively alters an aerodynamic characteristic of the aerodynamic surface in response to the control signal.

A method of generating a pressure wave proximate an airflow surface and altering airflow to promote a localized lowering of skin friction over the airflow surface is described herein. A series of pressure waves may be configured to create a virtual riblet to control turbulent vortices in a boundary layer adjacent to the airflow surface creating a virtual riblet. The pressure waves may be configured to prevent disruption of the flow of air relative to at least one of a step or a gap associated with the airflow surface. The pressure wave generating system may be comprised of at least one of a thermoacoustic material, a piezoelectric material and a semiconductor material, and a microelectric circuit.

A cooperative actuator system for active flow control, a vehicle comprising such cooperative actuator system, and a method for operating an actuator system for active flow control. The cooperative actuator system includes actuators, a control unit, and a data unit. The actuators are distributed along the surface in at least a first group and a second group downstream of the first group. The control unit is configured to control the actuators of the first group so that they form a first flow structure along the surface. The data unit is configured to provide data of the first flow structure. The control unit is further configured to control the actuators of the second group based on the data of the first flow structure, so that the actuators of the second group cooperatively interact with the first flow structure to form a second flow structure along the surface.

An apparatus for determining a movement direction of a component of a mechanism. The apparatus includes an acoustic emission sensor arranged to detect acoustic emission from the mechanism, and a processor arranged to determine a Doppler shift in a frequency characteristic of the measured acoustic emission and to determine a movement direction of a component of the mechanism on the basis of the determined Doppler shift. A method of determining a movement direction of a component of a mechanism including detecting acoustic emission from the mechanism and determining a Doppler shift in a frequency characteristic of the measured acoustic emission and, determining, based on the Doppler shift in the frequency characteristic, a movement direction of the component of the mechanism.

A method of generating a pressure wave proximate an airflow surface and altering airflow to promote a localized lowering of skin friction over the airflow surface is described herein. A series of pressure waves may be configured to create a virtual riblet to control turbulent vortices in a boundary layer adjacent to the airflow surface creating a virtual riblet. The pressure waves may be configured to prevent disruption of the flow of air relative to at least one of a step or a gap associated with the airflow surface. The pressure wave generating system may be comprised of at least one of a thermoacoustic material, a piezoelectric material and a semiconductor material, and a microelectric circuit.

For adaptively influencing a flow with little intrusion into the surface, a flow control device is provided to influence the flow of a fluid medium on a fluid-dynamical surface of a fluid-dynamical profile body. An acoustic wave generating device is used to generate a standing acoustic wave with locally defined antinodes and nodes, and/or a sonic pulse is focused in a locally defined manner.

An air vehicle includes an airfoil designed for transonic flight. The airfoil has a region of supersonic flow during transonic flight. A surface of the airfoil has upstream and downstream orifices at or within the region. The air vehicle further includes an active flow control system for controlling air vehicle motion during transonic flight by controlling flow through the orifices to alter strength and location of a shock wave in the region. The system creates an aerodynamic imbalance to move the shock wave.

A cooperative actuator system for active flow control, a vehicle comprising such cooperative actuator system, and a method for operating an actuator system for active flow control. The cooperative actuator system includes actuators, a control unit, and a data unit. The actuators are distributed along the surface in at least a first group and a second group downstream of the first group. The control unit is configured to control the actuators of the first group so that they form a first flow structure along the surface. The data unit is configured to provide data of the first flow structure. The control unit is further configured to control the actuators of the second group based on the data of the first flow structure, so that the actuators of the second group cooperatively interact with the first flow structure to form a second flow structure along the surface.

Drag experienced by a vehicle traveling through an environmental media, such as air or water, may be modified by one or more energy beams which may increase or decrease drag. A control system may be used to actively modulate the drag of the vehicle by selectively transmitting energy beams. Energy beams may include electric pulse signals, pulsed air, piezoelectric, infrared, ultraviolet, laser, optical band, microwave, thermal other known acoustic, electric, optical, or other electromagnetic energy and any combination thereof. This could be a constant or pulsed energy beam and adjusted for the speed and/or vertical lift, frequency, density, angle, pulse and wavelengths experienced by the vehicle. Charged particles may be emitted from the vehicle itself and then utilized in front or behind the vehicle via electric current to improve the boundary layer, boundary flow.

The invention relates to fluid actuator for influencing the flow along a flow surface through ejection of a fluid. By means of a like fluid actuator, a continuous flow is distributed to at least two outlet openings in order to generate fluid pulses out of these outlet openings. Control of this distribution takes place inside an interaction chamber which is supplied with fluid flow via a feed line. Into this interaction chamber there merge at least two control lines via control openings to which a respective different pressure may be applied. Depending on the pressure difference at the control openings, the flow in the interaction chamber is distributed to the individual outlet openings.