Control law design for handling qualities improvement and structural load alleviation in rotorcraft

Recent results are presented on the modelling, control and identification of helicopters carried out under the Helicopter Active Control (HELI-ACT) project. Designing high-bandwidth control systems pushes the existing flight mechanics models to their limits, especially if structural load prediction and alleviation are to be investigated. We describe how engine dynamics have been added to the simulations we have developed and how time-domain system identification has been used to obtain an updated linearized model. This has been done in an effort to address deficiencies that were observed in the original models. The use of nonlinear elements is discussed in the context of optimizing handling quality metrics. Results are presented from the flight-test of control laws incorporating nonlinear elements, designed to optimize attitude quickness, and it is shown how extremely accurate predictions of bandwidth and quickness were made using the new model.