A progressive approach to predict shot peening process parameters for forming integral panel of Al7050-T7451

In this paper, a progressive approach to predict the multiple shot peening process parameters for complex integral panel is proposed. Firstly, the invariable parameters in the forming process including shot size, mass flow, peening distance and peening angle are determined according to the empirical and machine type. Then, the optimal value of air pressure for the whole shot peening is selected by the experimental data. Finally, the feeding speed for every shot peening path is predicted by regression equation. The integral panel part with thickness from 2 mm to 5 mm and curvature radius from 3200 mm to 16000 mm is taken as a research object, and four experiments are conducted. In order to design specimens for acquiring the forming data, one experiment is conducted to compare the curvature radius of the plate and stringer-structural specimens, which were peened along the middle of the two stringers. The most striking finding of this experiment is that the outer shape error range is below 3.9%, so the plate specimens can be used in predicting feeding speed of the integral panel. The second experiment is performed and results show that when the coverage reaches the limit of 80%, the minimum feeding speed is 50 mm/s. By this feeding speed, the forming curvature radius of the specimens with different thickness from the third experiment is measured and compared with the research object, and the optimal air pressure is 0.15 MPa. Then, the plate specimens with thickness from 2 mm to 5 mm are peened in the fourth experiment, and the measured curvature radius data are used to calculate the feeding speed of different shot peening path by regressive analysis method. The algorithm is validated by forming a test part and the average deviation is 0.496 mm. It is shown that the approach can realize the forming of the integral panel precisely.     

Fully distributed time-varying formation tracking control for multiple quadrotor vehicles via finite-time convergent extended state observer

This paper investigates a time-varying anti-disturbance formation problem for a group of quadrotor aircrafts with time-varying uncertainties and a directed interaction topology. A novel Finite-Time Convergent Extended State Observer (FTCESO) based fully-distributed formation control scheme is proposed to enhance the disturbance rejection and the formation tracking performances for networked quadrotors. By adopting the hierarchical control strategy, the multi-quadrotor system is separated into two subsystems: the outer-loop cooperative subsystem and the inner-loop attitude subsystem. In the outer-loop subsystem, with the estimation of disturbing forces and uncertain dynamics from FTCESOs, an adaptive consensus theory based cooperative controller is exploited to ensure the multiple quadrotors form and maintain a time-varying pattern relying only on the positions of the neighboring aircrafts. In the inner-loop subsystem, the desired attitude generated by the cooperative control law is stably tracked under a FTCESO-based attitude controller in a finite time. Based on a detailed algorithm to specify the cooperative control protocol, the feasibility condition to achieve the time-varying anti-disturbance formation tracking is derived and the rigorous analysis of the whole closed-loop multi-quadrotor system is given. Some numerical examples are conducted to intuitively demonstrate the effectiveness and the improvements of the proposed control framework.     

Review and propositions for the sliding/impact wear behavior in a contact interface

A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior. It results in contact damage until systems fail, which may cause significant economic losses and catastrophic consequences. The key point of solving this problem is to reveal the coupling damage mechanism of the sliding/impact behavior in typical systems and life characterization under a complicate evolving environment. This has been a hot topic in the area of mechanical reliability. The main work in this paper can be concluded as follows. Firstly, the main industries in which the “sliding/impact behavior” takes place have been introduced. Then, existing studies on the wear mechanism and degree analysis are presented, which includes surface morphology analysis, wear debris analysis, and wear degree measurement. Meanwhile, existing problems in theoretical modeling and experiments in current research are summarized, so as to point out a bright direction for future research on wear prediction. They include interface contact modeling, mathematic coupling mechanism modeling, wear equation establishment, and wear life characterization, which can provide some new ideas for improving the existing studies on the sliding/impact wear behavior.     

门限自回归模型参数的局部正交设计寻优法

在采用点值图确定门限区间个数的基础上，对门自回归模型中门限值、滞后步长、各门限区间模型阶数，利用正交设计方法寻优，计算工作量锐减，却可得到精度较高的预报模型。     

一种基于移步预测消除脉冲串扰的快速算法

以毫米波主被动复合探测器为工程应用背景,通过分析信号的特点,提出一种基于移步预测思想的快速算法来消除脉冲调制信号对被动通道信号的串扰。仿真分析和实验结果表明,该方法对改善信噪比效果明显,而且具有成本低、速度快和易于工程化实现的优点。     

多传感器数据融合与弹道落点的预报

为了更精确地对弹道落点进行预报，对多传感器数据融合技术进行了,分批人出了雷达、红外系统和光测系统与传感器融合子系统连用的实例，并得出结论：单传感器的精度是难以满足现代战争需要的，寻求一种较好的融合方法来提高落点预报精度虽是一个难题，但仍是可行的。     

具L2有界不确定性扰动系统最优跟踪问题的时域解

本文对Ｌ２有界不确定性扰动下的一性系统在时域提出Ｍａｘｍｉｎ最优跟踪问题，给出了问题的时域状态反馈解，这一问题与相应的Ｈ∞问题具有某种一致性，因此，问题的求解方法可为解决领域不确定系统的Ｈ∞最优跟踪问题提供一种时域途径。     

航天器舷窗玻璃的强度检验方法和寿命预测

以断裂力学为基础,结合热钢化玻璃应力分布的特点,首次提出了热钢化玻璃的检验试验和寿命预测方法,为热钢化舷窗玻璃的强度检验提供了理论基础。分析示例的计算表明,即使通过相同的检验应力,在不同的使用环境中允许的使用应力是不同的;不同环境下,同样的使用应力,玻璃的使用寿命相差很大。     

体现裕度定制思想的轴流压气机二维特性预估方法

为实施裕度定制，本文开发了能够体现裕度定制思想的轴流压气机二维特性预估方法。精细考虑了前后缘形状、最大弯度位置等，尤其是通过考虑叶片力而全面包含掠影响是本方法的重要特色。为初步验证本方法，对NASA37和NASA67转子进行了性能预估并与试验结果进行了对比。结果表明，本方法基本可靠，可以用于裕度定制目的。     

跨音多级轴流压气机对突变型扰动的动态响应

基于多级轴流压气机的逐级特性详细研究了跨音多级轴流压气机对突变型温度扰动、突变型压力－温度联合扰动的动态响应和气动稳定性。同时还给出了动态扰动下多级轴流压气机失稳识别的新的预估方法。