基于T-S模糊神经网络的飞机防滑刹车系统研究

航空业的发展对飞机防滑刹车系统提出了更高的要求,而传统PID+PBM控制器存在着低速打滑、刹车效率较低等问题;针对刹车过程中的不确定性和非线性问题,提出采用T-S模糊神经网络来进行防滑刹车控制器设计;在MATLAB/SIMULINK平台建立飞机刹车总体仿真模型,将设计的控制器与传统控制器进行对比仿真试验;仿真结果表明,基于T-S模糊神经网络的控制器解决了传统PID+PBM系统存在的问题,具有良好的控制效果,系统具有鲁棒性,能够适应变化的跑道情况,为飞机防滑刹车控制提供了一种新的方法。     

Optimising the absorption and transmission properties of aircraft microperforated panels

A method for evaluating the absorption and transmission performances of multi-layer micro-perforated structures whose facings are excited by different noise sources is described here. It is applied to determine if the acoustical performances of a number of Micro-Perforated Panels (MPPs), optimised both in absorption and transmission, exceed those of typical aircraft panels undergoing internal and external acoustic excitations. A fully-coupled modal formulation is presented that accounts for the effects of the sub-structure volumetric resonances on the acoustical properties of the partitions. It is validated against full-scale measurements performed with a pressure–velocity probe and a laser vibrometer to estimate the absorption and transmission coefficients of single- and double-layer micro-perforated partitions. The model is used to optimise the sound power dissipated by three layouts obtained from a typical aircraft partition by micro-perforating the trim panel (MPP–Porous–Panel), removing the fibreglass material (MPP–Cavity–Panel) and adding a second MPP inside the separating cavity (MPP–MPP–Panel). It is concluded that the MPP–Porous–Panel and MPP–MPP–Panel layouts provide excess interior noise reduction above 1.8 kHz and 1.2 kHz respectively, whereas the MPP–Cavity–Panel is not acoustically more efficient than a typical aircraft panel.     

The role of messaging on acceptability of military aircraft sounds in Sequoia National Park

Opportunities to experience natural sounds are among the most important reasons for visiting parks, and mandates require that the National Park Service protect natural soundscapes. Due to its proximity to military installations, military aircraft are prevalent above Sequoia National Park, and exposure to sounds produced by aircraft have been found to detract from visitor experiences. Military overflights and associated acoustic impacts are likely to continue given Sequoia’s relationship with these agencies, and proximity to military installations, and in turn visitor experiences may be depreciated. This study examined whether educational messaging could significantly affect Sequoia visitor acceptability of military aircraft sounds, and evaluated the strengths and limitations of visitor communication strategies as they pertain to soundscape management. Results determined that informing visitors about the presence of military aircraft through a theoretically-derived message could improve acceptability of military aircraft sounds by as much as 15%. These results indicate that educational messaging may offer immediate benefits to Sequoia visitor experiences.     

作战飞机可靠性指标确定方法研究

作战飞机的可靠性决定了其完成作战任务的能力,在飞机研制阶段提出合理的可靠性指标,对提高飞机可用性和战备完好性具有重要作用.根据作战飞机实际使用需求,提出一种基于战斗出动强度的作战飞机可靠性指标确定方法,将飞机作战需求转换成和飞机出动强度有关的可靠性定量参数.