Resonant operating rotor assembly

A method of operating a cyclic pitch control system for controlling a blade pitch angle of a thrust generating rotor assembly for an aircraft, the method comprising:

• receiving an input control signal to control the aircraft comprising the cyclic pitch control system, wherein the cyclic pitch control system comprises:
• the rotor assembly, wherein the rotor assembly comprises a rotor torque assembly comprising a rotor shaft rotationally connected to a rotor blade assembly comprising rotor blades being able to tilt about a rotor blade axis;
• wherein the rotor blade assembly has a tilting moment of inertia about the rotor blade axis and a first rotational moment of inertia about a rotor shaft axis;
• wherein the rotor torque assembly includes a rotational part of a motor connected to the rotor torque assembly, and has a second rotational moment of inertia about the rotor shaft axis, that is smaller than the first rotational moment of inertia;
• at least one spring member, connected to both the rotor torque assembly and the rotor blade assembly, configured to transfer torque between the rotor torque assembly and the rotor blade assembly and deform in case of an alteration in torque resulting in a rotational offset between a rotational position of the rotor torque assembly and the rotor blade assembly;
• a motor controller configured to transform a control signal into control of a torque generated by the motor throughout each rotation;
• a connecting member configured to transfer changes in the rotational offset between the rotational position of the rotor torque assembly and the rotor blade assembly into changes in rotor blade pitch;
• wherein a rotational speed of the rotor blade assembly, due to its relatively higher first rotational moment of inertia, varies less than a rotational speed of the rotor torque assembly;
• and
• wherein characteristics of the at least one spring member, the tilting moment of inertia and the second rotational moment of inertia, are configured with respect to each other to provide a rotational resonance frequency range of the rotor torque assembly within a range of rotational frequencies of operation for the rotor assembly, thereby providing a resonant gain effecting the rotational offset in relation to changes in torque generated by the motor;
• determining a time advance and an amplitude of a torque variation based, at least in part, on the control signal;
• and
• controlling the motor connected to the rotor torque assembly to generate the torque variation according to the determined time advance and amplitude.