基于改进扩展关联模型的飞机组件测试性研究

多信号流图模型是一种简单而有效的系统建模方法,已广泛地应用于测试性分析和故障诊断领域;为了减少飞机维修过程中组件的不必要更换,提高维修效率,对多信号流图模型的建模方法进行研究,以飞机音频管理组件(AMU)为例,建立多信号流图模型,构建故障一测试关联矩阵和故障一故障关联矩阵;为与实际出现的组件故障信息相匹配,对故障一故障矩阵进行改进,构建了实际故障信息一故障关联矩阵,对组件模型进行测试性分析;由实际维修经验可知,该信号模型可快速地定位故障,给出相应的维修措施,减少通常维修中采取的不必要措施,降低了人为因素的影响,大大地缩短了维修时间.     

基于自由摆的平板精确控制与激光追踪系统

以TI公司的MSP430F5438单片机为控制核心,结合步进电机和精密电位器WDD35D-4,实现了基于自由摆的平板控制与激光追踪系统。当摆杆摆角为45°～60°时,平板可以承载8枚一元硬币,并在5个摆动周期内维持稳定;当摆杆摆角为30°～60°时,固定在摆杆平板上的激光笔可以在15s内找到并跟踪1.5m远处的靶心。     

Optimal tracking performance of MIMO discrete‐time systems with communication constraints

The optimal tracking problem for multiple‐input multiple‐output linear‐time‐invariant discrete‐time systems with communication constraints in the feedback path is studied in this paper. The tracking performance is measured by the energy of the error signal between the output of the plant and the reference signal. The objective is to obtain an optimal tracking performance, attainable by all possible stabilizing compensators. It is shown that the optimal tracking performance consists of two parts, one depends on the nonminimum phase zeros and zero direction of the given plant, as well as the reference input signal direction, and the other depends on the nonminimum phase zeros, unstable poles, and pole direction of the given plant, as well as the bandwidth and additive white Gaussian noise of the communication channel. It is also shown that, if the constraint of the communication channel does not exist, the optimal tracking performance reduces to the existing tracking performance of the control system without communication constraints. A typical example is given to illustrate the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimal Performance in Tracking Stochastic Signal Under Disturbance Rejection

The analysis method of optimal tracking performance is proposed for multiple‐input multiple‐output (MIMO) linear time‐invariant (LTI) systems under disturbance rejection. An H₂ criterion of the error signal between the output of the plant and the reference signal is used as a measure for the tracking performance. Spectral factorization is applied to obtain the optimal solution of the system tracking error. The explicit expressions are derived for this minimal tracking error with respect to random reference signals under disturbance rejection. It is shown that the nonminimum phase zeros, the zero direction, the unstable poles, the pole direction of a given plant, statistical characteristics of the reference input signal, and disturbance signal have a negative effect on a feedback system's ability to reduce the system error with disturbance rejection. The results show that the optimal tracking performance will further be damaged because of disturbance rejection. Some typical examples are given to illustrate the theoretical results.     

A new admissibility condition of discrete-time singular systems with time-varying delays

This paper gives a novel delay-dependent admissibility condition of discrete-time singular systems with time-varying delays. For convenience, the time-varying delay is assumed to be the sum of delay lower bound and the integral multiples of a constant delay. Specially, if the constant delay is of unit length, the delay is an interval-like time-varying delay. The proposed admissibility condition is presented and expressed in terms of linear matrix inequality (LMI) by Lyapunov approach. Generally, the uncertainty of time-varying delay would lead to conservatism. In this paper, this critical issue is tackled by accurately estimating the time-varying delay. Consequently, the proposed admissibility condition is less conservative than the existing results, which is demonstrated by a numerical example.     

变风量空调系统优化控制策略研究

变风量空调系统是多变量,大滞后、非线性和不确定性的系统,普通的模糊神经网络控制已难以满足其多变量动态控制的要求,为改善变风量空调系统控制性能,本文提出了一种小波模糊神经网络预测控制方法,实现变风量空调的温湿度有效控制.通过小波神经网络预测器在线建立被控对象的数学模型,并用模糊RBF神经网络控制器对所得到的信息在线修正,优化控制器参数,从而改善系统的控制效果.仿真结果表明,小波模糊神经网络预测控制具有很强的鲁棒性和自适应能力,控制精度高,控制效果好,安全可靠等优点,具有广泛的应用价值.     

人性化设计理念在剑杆织机设计中的应用

文章主要从设计层次的三个方面:合理性、用户体验和人文关怀对剑杆织机设计过程中的人性化设计理念做出分析,从而使人们对人性化设计理念有更清楚和全面的认识并在设计中给予充分的应用和体现。     

使用报表脚本实现报表续打套打

报表文件的续打套打是一个常见的需求,通过程序的参数设置和计算操控报表脚本从而实现规范的报表续打可以报表规范的续打。     

超重力对燃烧合成Ti（C，N）-TiB2复合粉体的影响

以Ti和B4C为起始反应物，分别在常规和超重力条件下通过燃烧合成技术制备出Ti（C,N）-TiB2复合粉体，利用XRD和SEM对燃烧产物进行了表征，研究了起始组成和超重力条件对燃烧产物相组成和微观形貌的影响。结果表明，燃烧产物主要由Ti（C，N）和TiB2组成，通过改变起始配方中Ti／B4C的摩尔比，可以调节产物中Ti（C，N）和TiB2的相对含量。超重力条件下，反应物颗粒接触更加充分，碰撞更加频繁，因而晶粒形态发育更加完整，生成规则的多面体。     

美国大学教学评估及其对中国高等教育的启示

美国大学和学院，学生对教师教学进行有效性评估。不同大学对教学有不同要求和标准；美国学术界对教学评估体系利与弊展开过辩论，而学生和老师的背景特征可能引起偏见。美国学生对老师进行教学评估的体系，对中国高等教育教学可能有一定的他石意义，但是，评估体系的现实条件有差异，中国不应当照抄或照搬美国教学评估，尤其应该摒弃将教与学关系扭曲为买方和卖方关系的观念。取其精华而弃其糟粕，建立适应中国的教学评估体系才能提高高等教育质量。