Retrospective Cost Adaptive Control for Helicopter Vibration Reduction

A retrospective cost adaptive controller (RCAC) is examined for helicopter vibration reduction using active trailing-edge aps. Vibration reduction performance of the RCAC controller is compared to that of the adaptive Higher harmonic controller (HHC) on a hingeless rotor configuration resembling the MBB BO-105 equipped with a single 20%c trailing-edge ap on each of the blades. The comparison is performed at both a low-speed descending ight condition and a high-speed cruise condition. A linear approximate model of the dynamics between the vibratory loads and control surface de ections is used as the system information in the controllers. Robustness of the two controllers to errors in the approximate model is analyzed and compared. Robustness of the controllers to variations in the helicopter weight coefficient is also compared. The results show that the RCAC is as effective as the HHC and due to its adaptive nature, the RCAC has considerable potential for more complicated rotorcraft missions involving maneuvering flight.