Development of a High-Performance Low-Weight Hydraulic Damper for Active Vibration Control of the Main Rotor on Helicopters—Part 1: Design and Mathematical Model

Abstract

The helicopter vibrations generated by the main rotor/gearbox assembly are the principal cause of damage to cockpit instruments and discomfort of the crew in terms of cabin noise. The principal path of vibration transmission to the fuselage is through the gearbox rigid support struts. With the aim of reducing these vibrations, this paper presents the design of a low-weight high-performance active damper for vibration control developed by Elettronica Aster S.p.A. The system is intended to replace the conventional struts and is composed of an electro-hydraulic actuator hosted within a compliant structure. This parallel nested structure allows the system to reach a high-power density. A physics-based mathematical model was used as a design digital twin to optimize the performance to meet the strict requirements. The active damper was designed for a reference application of a 15-seat medium-sized twin-engine helicopter. The model was used to perform the tests specified in the acceptance and testing procedure document, showing the compliance with the requirements of the current design. The damper physical realization, test bench design, experimental campaign, and model validation will be presented in Part 2.

Development of a High-Performance Low-Weight Hydraulic Damper for Active Vibration Control of the Main Rotor on Helicopters—Part 2: Preliminary Experimental Validation

“…The ATP, described in detail in [18], has been developed as a comprehensive document containing the testing and acceptance procedure to ensure the suitability of the ADVC for integration into aircraft systems. It encompasses a range of tests designed to verify both static and dynamic characteristics of the system.…”

“…The mathematical model has been thoroughly described in Part 1 [18] as it has been used for the model-based design process. In fact, thanks to a preliminary linear model and, subsequently, its advanced nonlinear evolution, the required performance of the ADVC has been met in accordance with the ATP specifications, leading to the layout depicted in Figure 2.…”

“…The certification test results provided by the manufacturer also contained the flow/current frequency response and the characteristic bandwidth. As detailed in [18], the servo-valve dynamics has been condensed into a unique second-order transfer function representing the first stage and spool dynamics of the servo-valve. The values of the natural frequency and damping factor have been estimated by fitting the amplitude and phase plots on the experimental ones and then feeding them directly into the model transfer function.…”

“…The mathematical model has been fitted The work has been divided into two parts, as depicted in Figure 1. The first one [18] presents a comprehensive state of the art and introduces the proposed solution: it explains the conceptual architecture of the system and its working principle, together with a detailed description of the mathematical model used for the model-based design process. The acceptance and testing procedure (ATP) is outlined.…”

“…This paper provides the natural continuation of the research program, presenting the realized technological demonstrator and the physical implementation of a dedicated test bench appositely designed to perform ATP tests. The mathematical model has been fitted on the real prototype in order to validate the preliminary simulated results obtained in Part 1 [18]. Then, it has been used to gain additional insights into the system behavior and to inform the definition of control parameters to be used on the real equipment to pass ATP tests successfully.…”