High-efficiency aircraft antiskid brake control algorithm via runway condition identification based on an on-off valve array

The aircraft antiskid braking system is an important hydraulic system for preventing tire bursts and ensuring safe take-off and landing. The brake system adjusts the force applied on the brake discs by controlling the brake pressure. Traditional aircraft antiskid braking systems achieve antiskid performance by controlling the braking pressure with an electrohydraulic servo valve. Because the pilot stage of an electrohydraulic servo valve is easily blocked by carbonized hydraulic oil, the servo valve would become a dangerous weak point for aircraft safety. This paper proposes a new approach that uses an on-off valve array to replace the servo valve for pressure control. Based on this new pressure control component, an efficient antiskid control algorithm that can utilize this discontinuous feature is proposed. Furthermore, the algorithm has the ability to identify the runway circumstances. To overcome the discontinuity in the process of using an on-off valve array, the Filippov framework is introduced. The conditions of convergence of the system are also discussed. The results of the digital simulations and the hardware-in-the-loop (HIL) braking experiments are used to verify the efficiency and stability of the proposed control algorithm. The method also proves that the on-off valve array can replace the servo valve perfectly as a new type of antiskid braking pressure control component.     

举办应用型本科教育的探索与思考

面对我国应用型本科教育不断发展和壮大的新形势,准确把握和正确认识其办学基本定位和办学规律,科学有效地实施应用型本科教育,是高等教育面临的一个重要课题。通过从发展环境、基本现状、努力方向等方面对应用型本科教育进行的论述与剖析,为决策好、研究好、实施好应用型本科教育提供了一定的参考。     

Experimental investigation on dynamic response of flat blades with underplatform dampers

One test rig with three blades and two Under-Platform Dampers (UPDs) is established to better understand the dynamical behavior of blades with UPDs. A pre-loaded spring is used to simulate the centrifugal load acting on the damper, thereby achieving continuous adjustment of the pressing load. UPDs with different forms, sizes and materials are carefully designed as experimental control groups. Noncontact measurement via a laser Doppler velocimeter is employed and contact excitation which is performed by an electromagnetic exciter is adopted to directly obtain the magnitude of the excitation load by a force sensor mounted on the excitation rod. Particular attention is paid to the influence of the contact status of the contact surfaces, e.g. the pressure-sensitive paper is used to measure the effective contact area of the UPDs. The experimental variables are selected as the centrifugal force, the amplitude of the excitation force, the damper mass, the effective contact area, and the damper material. The Frequency Response Function (FRF) of the blade under different experimental parameters is obtained by slow frequency sweep under sinusoidal excitation to study the influence of each parameter on the dynamic characteristics of the blade and the mechanism analysis is carried out combined with the experimental results.     

学校图书馆的人文素质教育功能

本通过对当前大学生人素质现状的分析，指出图书馆应在人素质教育中起重要作用，并对如何发挥图书馆人素质教育功能的提出了建议。     

格的微分

在偏序关系的基础上给出了格的微分定义,同时也给出了恒等微分和保序微分的定义。通过格微分的弱正则性和正则性,研究格的微分的一些性质。     

基于四边形网格细分曲面的生成

基于Catmull-Clark细分模式，提出了一种有效的四边形网格的细分曲面生成方法。对细分算法的数据结构特点进行了详细的分析，根据细分规则，给出了算法的生成矩阵以及连接规律。该方法具有局部性好、简单、易操作的特点，可成功应用于工程实际，解决细分曲面的生成问题。     

高职教育办学特色的构建与实施

详细介绍了西安航专高职教育办学特色的理论基点和实践历程，分析了西安航专办学特色和做法，重点从明确服务面向、构建合作平台、建设实训基地、开展“订单”培养、实施能力本位和解决企业难题实现互动双赢这六个方面总结了西安航专校企合作开展人才培养的具体做法和取得的显著效果。     

Two freedom linear parameter varying μ synthesis control for flight environment testbed

To solve the problem of robust servo performance of Flight Environment Testbed(FET)of Altitude Ground Test Facilities(AGTF) over the whole operational envelope, a two-degree-offreedom μ synthesis method based on Linear Parameter Varying(LPV) schematic is proposed, and meanwhile a new structure frame of μ synthesis control on two degrees of freedom with double integral and weighting functions is presented, which constitutes a core support part of the paper. Aimed at the problem of reference command's rapid change, one freedom feed forward is adopted, while another freedom output feedback is used to meet good servo tracking as well as disturbance and noise rejection; furthermore, to overcome the overshoot problem and acquire dynamic tuning,the integral is introduced in inner loop, and another integral controller is used in outer loop in order to guarantee steady errors; additionally, two performance weighting functions are designed to achieve robust specialty and control energy limit considering the uncertainties in system. As the schedule parameters change over large flight envelope, the stability of closed-loop LPV system is proved using Lyapunov inequalities. The simulation results show that the relative tracking errors of temperature and pressure are less than 0.5% with LPV μ synthesis controller. Meanwhile, compared with non-LPV μ synthesis controller in large uncertainty range, the proposed approach in this research can ensure robust servo performance of FET over the whole operational envelope.     

小波理论及其在信号处理中的应用

文章主要从信号处理的角度阐述了小泼理论,不同的小波和小波包函数具有不同的时间（空间）一频率性质,具体表现为正则度、消失矩、滤波器的幅频和相频响应等。在此基础上,通过例子说明小波理论在通信信号处理中的一些应用。