基于压缩感知的叶端定时信号参数辨识方法

叶端定时技术作为一种非接触式测量手段,在实际应用中的主要问题之一是测量信号欠采样。压缩感知方法是解决信号欠采样问题的有效手段,但由于求解过程中引入了正则化项,在提高稀疏度时,降低了幅值重构精度,而转子叶片振动幅值参数的准确辨识对于叶片动应力重构具有重要意义。将叶片振动方程设计矩阵与压缩感知字典相结合,在不依赖先验信息的条件下对叶片振动参数进行辨识。首先,根据振动方程设计矩阵形式及关注的最大振动频率,构造压缩感知字典;其次,通过叶端定时信号稀疏表示中的非零元素所在位置,从压缩感知字典中提取对应原子构成设计矩阵进而求得振动参数;接着,叶端定时（BTT）模拟仿真结果表明,所提方法可有效辨识叶片单模态、多模态振动参数;最后,开展旋转叶片振动测试试验,同时利用应变片和叶端定时系统采集振动信号,结果表明,与应变片测量结果相比,提出的方法振动频率辨识相对误差仅为0.14%;对比4个叶片的位移-应变传递比,其中偏离均值的最大百分比仅为2.15%。     

Multi-probe linear fitting and time of arrival linear correction method to analyze blade vibration based on blade tip timing without once-per-revolution

Blade vibration monitoring can ensure the safe operation of aero-engine rotor blades. Among the methods of blade vibration monitoring, Blade Tip Timing (BTT) method has attracted more and more attention because of its advantages of non-contact measurement. However, it is difficult to install the Once-Per-Revolution (OPR) probe in the confined space of aero-engine, and the failure and instability of the OPR signal will reduce the reliability of the blade vibration analysis results, which directly affects the accuracy of the blade vibration parameters identification. The Multi-Probe linear fitting and Time of Arrival (ToA) Linear Correction method based on the BTT (MP-LC-BTT) without OPR is proposed to reduce the errors of single probe linear fitting method for blade vibration displacement analysis. The proposed method can also correct the calculation error of blade vibration displacement due to the nonlinear change of rotation speed, which can improve the analysis accuracy of the blade vibration displacement. A new blade vibration model conforming to the actual vibration characteristics is established, and the effectiveness of the proposed method is verified by numerical simulation. Finally, the reliability and accuracy of the MP-LC-BTT method have been verified by the experiments which include two high-speed blade test-benches and an industrial axial fan. This method can be used in the actual aero-engine monitoring instead of the BTT method with OPR.     

基于任意传感器排布的叶尖定时信号压缩感知辨识方法

基于叶片振动和叶尖计时系统的特点,推导了任意传感器角度分布下叶片振动响应的分布规律,并基于叶尖定时信号频域的稀疏性,探究了压缩感知方法在叶尖定时信号的重构和倍频辨识上的应用。通过同步信号和非同步信号的大量数值实验,分析了包括信号重构误差、传感器数量、旋转周期数、频率分辨率和信噪比等因素对辨识效果的影响,提出了压缩感知重构叶尖定时信号的基本方法和步骤。进一步将压缩感知方法应用于某型号涡扇发动机钛合金宽弦风扇叶片有限元仿真获得的振动响应数据重构,验证了该方法的有效性。结果表明:在加入了叶尖测点位置误差和30 dB随机噪声的前提下,在80%、90%和100%三种转速工况下均清晰辨识出幅值较大的激励倍频。基于任意传感器角度分布的压缩感知方法对叶尖定时信号辨识效果较好。     

高可靠小条件数压缩感知叶尖定时信号辨识

为增强基于任意角度压缩感知(CS)叶尖定时信号(BTT)重构的稳定性,采用小生境微种群遗传算法提出了基于小条件数的高稳定性传感器安装布置方法。研究发现:任意角度CS的恢复矩阵条件数越小,不同信噪比下同步和非同步振动信号重构误差越趋于稳定在较低范围,优化后发现条件数为1的排布方案下,相邻传感器角度间隔趋向于均布2m取K的形式。利用条件数为1的矩阵冗余特性,设计了高可靠性的传感器排布方案,数值试验和有限元仿真验证表明叶尖定时系统在失效一个传感器的情况下仍可稳定得到准确的重构结果。在信噪比为5 dB时,冗余排布相比参考排布的主倍频幅值重构误差降低4.4%以上,验证了采用最小条件数排布的任意角度CS信号辨识方法在噪声及传感器失效情况下仍可保证BTT测量结果的有效性和可靠性。      

基于叶端定时的转子叶片动应变重构不确定性量化

基于叶片非接触式动应变重构理论,开展动应变重构不确定性量化方法研究。基于方差合成定理建立重构叶片动应变不确定性量化分析模型;以模拟转子叶片为研究对象,开展旋转叶片叶端定时试验,利用周向傅里叶算法获取不同叶端定时传感器布局下的测点振幅,通过最大熵方法拟合振幅分布概率密度函数,确定叶端定时测振的不确定性参数;结合Kriging代理模型和试验共振频率数据对叶片有限元模型进行修正,获取关键测点位移-应变转换因子,并获取考虑共振转速以及测点位置不确定性的转换因子不确定性参数;获取重构动应变的均值、标准不确定度和包含区间,与应变片测量数据作对比。结果表明,除5号叶片A测点外,测量动应变均位于重构动应变的95%置信度下的包含区间内,且所有叶片的应变片测点动应变重构误差不超过15%。     

Spatial transformation of general sampling-aliasing frequency region for rotating-blade parameter identification with emphasis on single-probe blade tip-timing measurement

Blade-health monitoring is intensely required for turbomachinery because of the high failure risk of rotating blades. Blade-Tip Timing (BTT) is considered as the most promising technique for operational blade-vibration monitoring, which obtains the parameters that characterize the blade condition from recorded signals. However, its application is hindered by severe undersampling and stringent probe layouts. An inappropriate probe layout can make most of the existing methods invalid or inaccurate. Additionally, a general conflict arises between the allowed and required layouts because of arrangement restrictions. For the sake of economy and safety, parameter identification based on fewer probes has been preferred by users. In this work, a spatial-transformation-based method for parameter identification is proposed based on a single-probe BTT measurement. To present the general Sampling-Aliasing Frequency (SAFE) map definition, the traditional time–frequency analysis methods are extended to a time-sampling frequency. Then, a SAFE map is projected onto a parameter space using spatial transformation to extract the slope and intercept parameters, which can be physically interpreted as an engine order and a natural frequency using coordinate transformation. Finally, the effectiveness and robustness of the proposed method are verified by simulations and experiments under uniformly and nonuniformly variable speed conditions.     

An active vibration control method based on energy-fuzzy for cantilever structures excited by aerodynamic loads

In wind tunnel tests for the full-model fixed with sting, the low structural damping of the long cantilever sting results in destructive low-frequency and large-amplitude vibration. In order to obtain high-quality wind tunnel test data and ensure the safety of wind tunnel tests, an energy-fuzzy adaptive PD (Proportion Differentiation) control method is proposed. This method is used for active vibration control of a cantilever structure under variable aerodynamic load excitation, and real-time adjustment of parameters is achieved according to the system characteristics of vibration energy. Meanwhile, a real-time method is proposed to estimate the real-time vibration energy through the vibration acceleration signal, and the average exciting power of aerodynamic load is obtained by deducting the part of the power contributed by the vibration suppressor from the total power. Furthermore, an energy-fuzzy adaptive PD controller is proposed to achieve adaptive control to the changes of the aerodynamic load. Besides, the subsonic and transonic experiments were carried out in wind tunnel, the results revealed that comparing to fixed gain PD controllers, the energy-fuzzy adaptive PD controller maintains higher performance.     

A novel LAAS pseudo-range error over-bound method based on improved pseudo-range error distribution model

The high level of safety demand of civil aviation requests local area augmentation system (LAAS) extremely high navigation integrity performance. A new LAAS pseudo-range error overbound method is proposed in this paper to improve the integrity of LAAS. Firstly, a more practical pseudo-range error distribution model is established. Then, by calculating the relationship between the statistical uncertainty of the model parameter and the integrity risk, a new method is proposed to calculate the pseudo-range error over-bound model. This method can effectively reduce the inflation factor and the resulting conservativeness of the over-bound model. Comparative experiments show that the method proposed in this paper performs better and satisfies the requirements of real applications.