Innovative High-Performance Active Dampers for Effective Mitigation of Helicopter Main Rotor Vibrations

Helicopter vibrations, primarily generated by the main rotor-gearbox assembly, are a major source of concern due to their impact on structural integrity, cockpit instrument durability, and crew comfort. These vibrations are mainly transmitted through the gearbox's rigid support struts to the fuselage, leading to increased cabin noise and potential damage to critical components. This paper presents a solution for vibration mitigation which involves replacing traditional gearbox support struts with low-weight, high-performance active dampers. Developed by Elettronica Aster S.p.A., these active dampers are designed as electro-hydraulic actuators embedded within a compliant structure. The parallel nested configuration of the system enables high power densities and effective vibration control, significantly reducing the transmission of harmful vibrations to the fuselage. The comprehensive model-based design process is detailed, describing the development and use of a high-fidelity physics-based mathematical model as a design digital twin. It allowed optimizing the damper's performance to meet the stringent operational requirements of the considered case study, consisting in a 15-seat medium-sized twin-engine helicopter. This model was essential to simulate and verify the system's behavior under various conditions to ensure a robust and reliable design and the proper setup of controller's parameters. Additionally, the paper presents the design, modelling and realization of a dedicated test bench for an experimental campaign, which aimed to validate the model results, tune parameters, and evaluate and verify the damper's real-world performance. The active damper prototype underwent rigorous experimental validation, confirming its ability to meet performance targets, significantly reduce vibration transmission and improve helicopter durability and crew comfort. The results of the extensive testing are shown, demonstrating the practical application of the fully integrated proposed solution. This innovative approach to vibration control offers a practical and efficient solution to a longstanding issue in helicopter operations, reinforcing the potential of the presented solution for effective vibration reduction.