A Study of Active Rotor-Blade Vibration Control Using Electro-Magnetic Actuation: Part 1 — Theory

This is the first paper in a two-part study on active rotor-blade vibration control using electro-magnetic actuation. Emphasis is focused on theoretical aspects of implementing active control into coupled rotor-blade systems, more precisely, into systems where rotor lateral motion is coupled to blades flexible motion. The theoretical investigation includes controllability and observability analyses of such a system in order to determine optimal actuator and sensor placement. An analysis methodology based on modal analysis in time-variant systems, due to the periodic time-variant nature of this kind of system, is presented. The method takes into account the strong vibration coupling which has a significant effect on the controllability and observability of bladed rotor systems. The analyses show that, for tuned bladed rotors, actuators will have to be located within the blades in order to make all vibration modes controllable. However, if the system is deliberately mistuned, rotor and blade vibrations can be controlled using shaft-based actuation and sensing only. Moreover, a controller design procedure for obtaining active periodic time-variant modal controllers, capable to cope with the time-periodicity of the system, is presented. Controllers are designed for a tuned as well as a deliberately mistuned system. The tuned system is controlled using both blade and shaft actuators while the mistuned system is controlled using only shaft actuation. Numerical simulations are provided to show the efficiency of the designed controllers.