Semi active tunable mass damper for helicopters

Helicopters are among the most complex machines ever made. While ensuring high performance from the aeronautical point of view, they are not very comfortable due to vibration mainly created by the main rotor. Traditionally this problem is solved by mounting several TMD inside the helicopter, each tuned to the frequency of the disturbance the main associated with the main rotor. In particular, this frequency is equal to the angular speed of the main rotor times the number of blades. Despite the angular speed of the main rotor is kept fixed and constant during the flight, it happens that some changes may be needed in particular situations. Therefore it happens that the mass dampers are no more tuned and thus ineffective. This leads to a significant increase of the amplitude of vibration. This work proposes to replace the purely passive systems with semi-active systems that are able to change their own natural frequency in order to be effective at each angular speed of the main rotor. The paper deals with the preliminary analysis of the project to numerically and experimentally evaluate the feasibility of this solution.