A principal component least mean square (PC-LMS) adaptive algorithm is described that has considerable benefits for large control systems used to implement feedforward control of single frequency disturbances. The algorithm is a transform domain version of the multichannel filtered-x LMS algorithm. The transformation corresponds to the principal components of the transfer function matrix between the sensors and actuators in a control system at a single frequency. The method is similar to other transform domain LMS algorithms because the transformation can be used to accelerate convergence when the control system is ill-conditioned. This ill-conditioning is due to actuator and sensor placement on a continuous structure. The principal component transformation rotates the control filter coefficient axes to a more convenient coordinate system where (1) independent convergence factors can be used on each coordinate to accelerate convergence, (2) insignificant control coordinates can be eliminated from the controller, and (3) coordinates that require excessive control effort can be eliminated from the controller. The resulting transform domain algorithm has lower computational requirements than the filtered-x LMS algorithm. The formulation of the algorithm given here applies only to single frequency control problems, and computation of the decoupling transforms requires an estimate of the transfer function matrix between control actuators and error sensors at the frequency of interest. The feasibility of the method was demonstrated in real-time noise control experiments involving 48 microphones and 12 control actuators mounted on a closed cylindrical shell. Convergence of the PC-LMS algorithm was more stable than the filtered-x LMS algorithm. In addition, the PC-LMS controller produced more noise reduction with less control effort than the filtered-x LMS controller in several tests. / Ph. D.

Nos últimos anos, inúmeros trabalhos têm investigado como avaliar a percepção de conforto e desconforto no transporte aéreo. A literatura mostra que o conforto é um construto de natureza subjetiva, de difícil mensuração e, por este motivo, a avaliação de aspectos de desconforto é sugerida em alguns estudos. O objetivo geral desta pesquisa foi aprimorar os métodos de análise do conforto e do desconforto vivenciado pelo passageiro ao considerar as atividades realizadas durante um voo típico, contribuindo com o projeto de poltrona e de cabine de aeronaves. Para tal, este estudo propõe um método dividido em três fases: mapeamento de pressão de posturas estáticas, mapeamento contínuo de pressão e mapeamento de posturas típicas. O intuito da primeira fase foi identificar as contribuições e limitações dos métodos e técnicas descritos na literatura por meio de um experimento utilizando mapeamento de pressão de interface entre o ocupante e a poltrona em de posturas estáticas e um questionário de avaliação da poltrona. A segunda fase analisou as atividades de repousar e ler em um simulador que representa o interior de uma aeronave, com o apoio da técnica de medição contínua de pressão de interface em conjunto com observação de pesquisadores e relato pós-experimento. Após a realização dos ensaios, a equipe do projeto participou de sessões brainstorming onde melhorias do ambiente vivencial do passageiro foram identificadas e prototipadas em um segundo momento. A última fase avaliou a percepção de desconforto em cada parte do corpo em posturas pré-definidas que representaram as posturas mais utilizadas nos ensaios da fase anterior. Os resultados da pesquisa mostraram que cada fase que compõe o método possui um olhar diferente sobre a poltrona e o ambiente da cabine, mas que no conjunto se complementam com o intuito de identificar oportunidades de melhoria do projeto desses elementos. Além disso, uma mudança ocorreu também no time de concepção que, a partir da reflexão sobre a experiência vivida, se sensibilizou para aspectos de projeto que anteriormente passavam despercebidos, permitindo a geração de soluções que atendessem não somente aos requisitos de certificação e de produto, mas também propiciassem condições mais favoráveis para a realização de atividades em voo. / In recent years, numerous studies have investigated how to assess the perception of comfort and discomfort in the air transportation. Literature shows that comfort is a subjective construct, difficult to measure and, therefore, the assessment of discomfort aspects is suggested in some studies. The overall objective of this research was to improve the evaluation methods of passengers comfort and discomfort while considering the activities performed during a typical flight, contributing to seat and aircraft cabin project. Thus, this thesis proposes a method divided into three phases: static postures pressure mapping, continuous pressure mapping and typical postures mapping. The aim of the first phase was to identify the contributions and limitations of methods and techniques described in the literature by developing an experiment using static postures pressure mapping and a seat evaluation questionnaire. The second phase examined the activities of resting and reading in an aircraft interior simulator using continuous pressure measurement allied to observation and postexperiment report. After the tests, the design team participated in brainstorming sessions where improvements in seat and aircraft cabin were identified and prototyped in a further moment. The last phase evaluated discomfort perception in each body part when adopting the most common postures used in the previous phase. The results showed that each method phase brings a different view on the seat and aircraft cabin that contributes to identify opportunities for improving the design of these elements. Furthermore, the design team, reflecting on their own experience, could develop solutions for aircraft cabin project that not only met airworthiness and product requirements, but also provided more affordable conditions for performing in flight activities.

Nos últimos anos, inúmeros trabalhos têm investigado como avaliar a percepção de conforto e desconforto no transporte aéreo. A literatura mostra que o conforto é um construto de natureza subjetiva, de difícil mensuração e, por este motivo, a avaliação de aspectos de desconforto é sugerida em alguns estudos. O objetivo geral desta pesquisa foi aprimorar os métodos de análise do conforto e do desconforto vivenciado pelo passageiro ao considerar as atividades realizadas durante um voo típico, contribuindo com o projeto de poltrona e de cabine de aeronaves. Para tal, este estudo propõe um método dividido em três fases: mapeamento de pressão de posturas estáticas, mapeamento contínuo de pressão e mapeamento de posturas típicas. O intuito da primeira fase foi identificar as contribuições e limitações dos métodos e técnicas descritos na literatura por meio de um experimento utilizando mapeamento de pressão de interface entre o ocupante e a poltrona em de posturas estáticas e um questionário de avaliação da poltrona. A segunda fase analisou as atividades de repousar e ler em um simulador que representa o interior de uma aeronave, com o apoio da técnica de medição contínua de pressão de interface em conjunto com observação de pesquisadores e relato pós-experimento. Após a realização dos ensaios, a equipe do projeto participou de sessões brainstorming onde melhorias do ambiente vivencial do passageiro foram identificadas e prototipadas em um segundo momento. A última fase avaliou a percepção de desconforto em cada parte do corpo em posturas pré-definidas que representaram as posturas mais utilizadas nos ensaios da fase anterior. Os resultados da pesquisa mostraram que cada fase que compõe o método possui um olhar diferente sobre a poltrona e o ambiente da cabine, mas que no conjunto se complementam com o intuito de identificar oportunidades de melhoria do projeto desses elementos. Além disso, uma mudança ocorreu também no time de concepção que, a partir da reflexão sobre a experiência vivida, se sensibilizou para aspectos de projeto que anteriormente passavam despercebidos, permitindo a geração de soluções que atendessem não somente aos requisitos de certificação e de produto, mas também propiciassem condições mais favoráveis para a realização de atividades em voo. / In recent years, numerous studies have investigated how to assess the perception of comfort and discomfort in the air transportation. Literature shows that comfort is a subjective construct, difficult to measure and, therefore, the assessment of discomfort aspects is suggested in some studies. The overall objective of this research was to improve the evaluation methods of passengers comfort and discomfort while considering the activities performed during a typical flight, contributing to seat and aircraft cabin project. Thus, this thesis proposes a method divided into three phases: static postures pressure mapping, continuous pressure mapping and typical postures mapping. The aim of the first phase was to identify the contributions and limitations of methods and techniques described in the literature by developing an experiment using static postures pressure mapping and a seat evaluation questionnaire. The second phase examined the activities of resting and reading in an aircraft interior simulator using continuous pressure measurement allied to observation and postexperiment report. After the tests, the design team participated in brainstorming sessions where improvements in seat and aircraft cabin were identified and prototyped in a further moment. The last phase evaluated discomfort perception in each body part when adopting the most common postures used in the previous phase. The results showed that each method phase brings a different view on the seat and aircraft cabin that contributes to identify opportunities for improving the design of these elements. Furthermore, the design team, reflecting on their own experience, could develop solutions for aircraft cabin project that not only met airworthiness and product requirements, but also provided more affordable conditions for performing in flight activities.

This study involves the modeling and optimization of heterogeneous (HG) blankets for improved reduction of the sound transmission through double-panel systems at low frequencies. HG blankets consist of poro-elastic media with small, embedded masses, operating similar to a distributed mass-spring-damper system. Although most traditional poro-elastic materials have failed to effectively reduce low-frequency, radiated sound from structures, HG blankets show significant potential. A design tool predicting the response of a single-bay double panel system (DPS) with, acoustic cavity, HG blanket and radiated field, later a multi-bay DPS with frames, stringers, mounts, and four HG blankets, was developed and experimentally validated using impedance and mobility methods (IMM). A novel impedance matrix formulation for the HG blanket is derived and coupled to the DPS using an assembled matrix approach derived from the IMM. Genetic algorithms coupled with the previously described design tool of the DPS with the HG blanket treatment can optimize HG blanket design. This study presents a comparison of the performance obtained using the genetic algorithm optimization routine and a novel interactive optimization routine based on sequential addition of masses in the blanket. This research offers a detailed analysis of the behavior of the mass inclusions, highlighting controlled stiffness variation of the mass-spring-damper systems inside the HG blanket. A novel, empirical approach to predict the natural frequency of different mass shapes embedded in porous media was derived and experimentally verified for many different types of porous media. In addition, simplifying a model for poro-elastic materials for low frequencies that Biot and Allard originally proposed and implementing basic elastomechanical solutions produce a novel analytical approach to describe the interaction of the mass inclusions with a poro-elastic layer. A full-scale fuselage experiment performed on a Gulfstream section involves using the design tool for the positions of the mass inclusions, and the results of the previously described empirical approach facilitate tuning of the natural frequencies of the mass inclusions to the desired natural frequencies. The presented results indicate that proper tuning of the HG blankets can result in broadband noise reduction below 500Hz with less than 10% added mass. / Ph. D.