Actuator constraints handling in higher harmonic control algorithms for vibration reduction

This paper discuses the advantages of using quadratic-programming-based higher harmonic control (HHC) algorithms for vibration reduction applications. Their benefits when dealing with actuator constraints in comparison with scaling, truncation and weight manipulation of the control efforts have been exposed in previous works. The main contribution of this work is the discussion in more detail of important implementation aspects of the quadratic programming in the context of Higher Harmonic Control. Equivalent translations of flapping constraints via constraints of the Fourier coefficients are not always possible in a quadratic-programming framework and approximations of the feasible region are required. Such approximations should be taken into consideration carefully to avoid significant loss of optimal performance. The benefits of incorporating quadratic programming algorithms in the HHC design problem are shown for a linearised representation of a five-blade coupled rotor-fuselage model augmented with active trailing edge flaps.