Abstract: A perpendicular axis turbine having at least two blades, wherein the blades are longitudinally offset with respect to one another, reducing the effects of blade-vortex interaction and providing increased power generation. In one embodiment, the blades are longitudinally offset such that the attachment point of one blade is halfway between the attachment points for the other blade.

Abstract: A perpendicular axis turbine having at least two blades, wherein the blades are longitudinally offset with respect to one another, reducing the effects of blade-vortex interaction and providing increased power generation. In one embodiment, the blades are longitudinally offset such that the attachment point of one blade is halfway between the attachment points for the other blade.

Abstract: Disclosed herein are control systems relating generally to the field of aerodynamics and more particularly to the control of vibration of rotor blades such as helicopter blades. Such systems involve devices for vibration control of each rotor blade, which incorporate control systems of the flow control type (e.g. actively controlled flap) and structural control type (e.g. active pitch link). Also disclosed are related methods of controlling vibration in a rotor blade, wherein the rotor blade is coupled to a rotor hub and has at least a torsional stiffness and a pitch angle associated therewith.

Abstract: Disclosed herein are control systems relating generally to the field of aerodynamics and more particularly to the control of vibration of rotor blades such as helicopter blades. Such systems involve devices for vibration control of each rotor blade, which incorporate control systems of the flow control type (e.g. actively controlled flap) and structural control type (e.g. active pitch link). Also disclosed are related methods of controlling vibration in a rotor blade, wherein the rotor blade is coupled to a rotor hub and has at least a torsional stiffness and a pitch angle associated therewith.

Abstract: A structural component having a stiffness which can be actively varied to control vibrations, for example in a helicopter rotor, an aircraft wing or tail, or in a robotic manipulator. The component has at least one recess or notch with opposed walls, which walls, in the absence of any intervening member, tend to move relative to each other when the component is stressed. A stiffness control element is situated in the recess or notch, this element comprising electrically or magnetically expandable material capable of being rapidly expanded from a first condition in which the element is out of contact with one of the walls, to an expanded condition in which the element extends across the recess or notch and transmits forces from one of the walls to the other, thus altering the stiffness of the component. The preferred expandable material is a stack of piezoelectric crystals.