Robust and distributed control of a smart blade

For the next generation of larger off-shore wind turbines, it has been suggested to use feedback to actively control the blade vibrations, thus decreasing fatigue damage and increasing the life of the machine. Because of both practical engineering difficulties and fundamental control theoretic limitations, it seems that individual pitch actuation may not be well suited for this type of control, prompting researchers to investigate other forms, such as tip actuation and the 'smart blade' concept. Most research in this area has been on the design of cheap, reliable and effective actuators and sensors, which are necessary for economic viability of the concept. We will argue that the design of a robust feedback controller is just as critical to the success of the smart blade concept, but has been so far overlooked because of the complexities of modeling and computation involved therein. In this paper, we take the first step in demonstrating how to build blade models with a distributed bounded uncertainty structure, in a framework appropriate for robust control analysis and design. We then discuss recent progress in distributed computationally efficient robust control techniques, scalable for very fine discretizations, and show that for coarse discretizations, even centralized techniques can be employed to design high-performance feedback controllers for a smart blade system, with guaranteed closed loop stability and performance for a variety of operating conditions and model mismatches. Copyright (C) 2009 John Wiley & Sons, Ltd.