Active Control of Rotor Aerodynamics and Geometry: Status, Methods, and Preliminary Results

The overall study explores two major categories of rotor aerodynamic modification. The first is devices or methods that can be used to actively alter the local aerodynamic properties of the rotor blade. The active aerodynamic devices being considered for the overall study include: flaps, slats, ailerons, active (MEM) tabs and vortex generators, "smart" materials such as shape memory alloys and piezioelectrics, and "morphing" structure technology for both large changes (i.e., camber modifications) and local shape changes (i.e., leading edge curvature). These devices would typically have response times on the order of, or faster than, a full-span, variable-pitch system. The control algorithms will employ linear state space methods that include individual blade pitch and multi-input, multi-output control of the selected aerodynamic devices. The second category of active rotor modifications is geometry control, based on variable-length blades. These technologies are applied to a virtual turbine design, originally developed under the WindPACT program and up-rated for this study to a 90-m diameter, 2.5 MW, variable- speed, variable-pitch turbine. The approach will include simulations using MSC-ADAMS and detailed cost modeling based on the simulated loads. The paper will present details of the aerodynamic and geometric designs developed to date, as well as the control strategy employed for both. Preliminary load results will be presented for the extendable blade design and for aerodynamic control using microtabs.