In forward flight all helicopters are subject to a time-varying aerodynamic load that results in a severe vibratory forcing at the rotor hub. This dynamic excitation may result in high vibration levels in the helicopter fuselage that are a problem both for the operation of the aircraft, the fatigue life of the structure and the comfort of the crew. The vibration spectra are dominated by low frequency components corresponding to the fundamental blade passing frequency and its harmonics. These low frequency vibrations can be reduced effectively by installing an active multi-channel vibration control system that seeks to minimise the response by exciting the structure using a set of actuators. The reduction that can be achieved by an active vibration control system depends on the control algorithm, the number of actuators, their sizes and, critically, on where these actuators are positioned. Poor positioning might only allow a very slight reduction while the optimal configuration might allow the vibration levels to be reduced to 10 % or less of their original level. For simple structures the engineer might rely on intuition in choosing actuator locations. However, for more complicated three-dimensional structures, the optimal positioning of actuators may defy intuition. To find the optimal actuator configuration requires a systematic and efficient approach as the number of configurations rapidly exceeds billions of combinations. Simulated annealing has proved to be an effective discrete search algorithm for finding optimal actuator positions for three-dimensional structures. Theoretically, the algorithm will converge asymptotically towards the global minimum. For the cases herein that have been verified against exhaustive search results, it means that simulated annealing will either be able to find the global minimum or one of the next best 10 local minima. In choosing an active control system that can provide a given reduction, two strategies are possible, namely either using a large number of small actuators, or a small number of large actuators. The advantages of using a large number of small actuators are that the system will be better at adapting to variations in load. This system is also expected to be less vulnerable to failure of a single actuator and the weight penalty is expected to be the smallest. The advantages of a system based on few large actuators are that it is cheaper and simpler to install and easier to control.


    Access

    Access via TIB

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Optimal actuator placement for reduction of helicopter vibration


    Additional title:

    Optimale Aktor-Anordnung zur Reduzierung von Schwingungen bei Hubschraubern


    Contributors:
    Hugin, C.T. (author) / Hatch, C. (author)


    Publication date :

    2004


    Size :

    8 Seiten, 7 Bilder, 1 Tabelle, 4 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English