The advances and innovation in PIANO are summarized in the following points:
Innovative nature of ATPA method: it potentially characterizes completely a mechanical system, by means of its topology. It can give a complete information about transmission paths in a complex system
In the context of PIANO tilt-rotor application, the method will give among other information, the split between air-borne and structure-borne noise. This can be obtained from the same test. It has never been applied before in aeronautics. So far, only force contribution has been studied in this field, and it is not enough when trying to find suitable and optimal countermeasures to reduce interior noise
The project aims at further developing and applying an objective method able to automatically identify subsystems in a complex mechanical system. A very promising methodology based on the powers of the direct transfer matrix and clustering techniques will be applied. This methodology allows as well to do an estimation of the degree of coupling amongst subsystems (quantifying it). It is a great advantage in front of current methods which need to calculate the modal density through FEM numerical calculations and are not able to limit the error, since degree of coupling cannot be quantified
In addition to the key role that the subsystem identification plays in the subsystems selection for an ATPA test, it must not be forgotten that the subdivision of a mechanical system into subsystems according to their vibroacoustic response is a task required in several modelling methods, e.g. SEA. Besides, a quantification of the degree of coupling can be very helpful to decide whether a subsystem may be analysed in a computer model or in a laboratory independently of the rest of the system or not
Local ANC strategy, as a first priority for PIANO, will address tones generated by propellers and TBL broadband noise in the bandwidth below 500 Hz. Primary target in PIANO is to enhance the extent, robustness and frequency range of the quiet zone around the passenger head, through the application of advanced ANC algorithms. Improvement of the passenger comfort by implementing binaural and psychoacoustic ANC as well as novel headrest design will be also addressed in order to optimize as much as possible the comfort feeling of passengers.
Global ANC strategy will focus on cancellation of low frequency global modes (e.g. well below 100Hz) and better spatial localization and enhancement of the extent of the quiet zones, especially at cabin areas with high noise level and poor LANC results. Efficient GANC algorithms will be implemented, such as Acoustic mode cancellation, Wave-Field synthesis and Multichannel Equalization, Non-linear and Artificial Intelligence Based approaches.
The result of ATPA will be exploited in global ANC strategy as inputs for the ANC filter implemented. Moreover, it is expected to significantly reduce the number of actuators allowing good performances with an important reduction of the weight of the solution in cabin.
The controllers used in PIANO will pilot a certain number of sensors and actuators with dedicated algorithm for each strategy. This controller design will be particularly important in order to significantly reduce the power consumption and its price. Dedicated architecture will be defined in function of the necessary strategy of control.
Inflight tests will allow to measure and optimize ANC reduction performances in-situ and will be also the opportunity to define the primary elements that can be used in other tilt-rotor aircraft models. Starting from the PIANO results, it will be possible to offer a range of solution based on this experience in a shorter time without significant extra-cost design for other models of tilt-rotor aircraft.