Stability domains of the vertical equilibrium state of a triple simple pendulum

The stability boundaries for the vertical equilibrium position of a triple simple pendulum subject to asymmetric follower force are analyzed. The effect of the upper spring and the magnitude of the follower force on the roots of the characteristic equation is studied Translated from Prikladnaya Mekhanika, Vol. 44, No. 10, pp. 122–134, October 2008.     

位置控制在HX-500E分断机中的应用

简述了HX500E玻璃分断机所以能切割特殊ITO玻璃的设计特点、工作原理及工艺过程,介绍了该机运动机构及控制组成,并以平台伺服的选型为例,介绍了伺服系统电机的选型方法,三菱定位模块FX2N-1PG的使用特点及应用,FX2N-1PG模块在位置控制中利用近点检测法和伺服编码器Z相脉冲组合完成伺服回归机械原点的方法,并指出了一些位置控制原点回归方法注意事项.     

First- and second-order sensitivities of beams with respect to cross-sectional cracks

This paper deals with a variational formulation for the sensitivity problem of beam systems in the context of deformable solids with cracks. Natural frequencies are defined as state variables involved in the energy functional of the system, while the cracks length and position are treated as system parameters. The hierarchical equation system is formed and solved for the first and second derivatives of the natural frequency functions with respect to the cracks length and position. An analytical procedure for calculations of the second-order sensitivities of natural frequencies is proposed for the non-symmetrical equation system operator. Numerical algorithms are worked out and implemented computationally. Analytical and numerical aspects of the problem are discussed in detail through a number of illustrative results.The support of this work by the State Committee for Scientific Research (KBN) under Grant No. 4-050-0148/17-98-00 is gratefully acknowledged.     

北斗双星/SINS组合导航系统滤波模型的一致性研究

北斗双星定位系统（简称双星定位）是我国自行建立的一种定位系统.根据北斗双星定位系统采用有源定位的特点,介绍了北斗双星与SINS组合的最优预测模型,该方法利用了双星定位系统提供的滞后定位信息对组合系统进行最优预测,进而校正惯导;同时为验证该滤波方法对状态估计的一致性,文中重点研究了滤波器一致性的准则,并给出了检验的统计量.理论研究和试验仿真证明,文中介绍的滤波器与系统是匹配的,具有较高的滤波性能和精度.     

A new modification of false position method based on homotopy analysis method

A new modification of false position method for solving nonlinear equations is presented by applying homotopy analysis method （HAM）. Some numerical illustrations are given to show the efficiency of algorithm.     

Costas环在无线扩频定位系统中的应用技术研究

分析了扩频定位系统中载波恢复和数据解调数学模型，设计了环路中应用的Butterworth低通滤波器和产生正交两路信号的Hilbert变换滤波器，在Simulink中建立了Costas环仿真模型。结果表明：该Costas环能够准确地实现扩频定位系统的载波恢复和发送端数据解调输出，理论仿真和实际工程实验基本一致。     

Experimental investigation of natural convection in a vertical rib-roughened channel with asymmetric heating

An experimental study in an open-ended vertical channel is carried out in order to describe the fluid dynamics and heat transfer of transient free convection inside a vertical rib-roughened channel asymmetrically heated at various uniform heat fluxes (650, 700, and 780 W/m²) corresponding to various modified Rayleigh numbers (3.65 × 10⁶, 3.93 × 10⁶ and 4.4 × 10⁶). Two ribs are symmetrically located on each wall. The investigations focused more specifically on the influence of the ribs positions inside the channel and the modified Rayleigh number (Ra^*) both in steady-state regime and during the transitional phase occurring just after the start of the heating on the flow structure and the heat transfer performance. The results showed the appearance of large-scale flow instabilities which will develop and propagate until the development of the pocket-like vortex (reversed flow). Also, the formation and breakup of recirculation eddies, vortex banishment, besides that a separation and shifting of the boundary layer from one wall to another are identified. The best position of the ribs for heat extraction depends on the magnitude of the Rayleigh number. In that case, the top position is the optimal position for the small and the moderate modified Rayleigh numbers.     

改变飞艇重心位置控制纵向运动

本文针对目前平流层飞艇的运动控制效率较低的问题,重点研究了改变平流层飞艇重心的轴向位置来控制飞艇的纵向运动。首先讨论了考虑飞艇重心位置的力和力矩平衡,并利用德国斯图加特大学风洞试验的数据,进行了算例分析。然后和常用的升降舵控制进行效率比较,得出了在空气密度较低的平流层采用改变重心位置比舵面控制具有优越性的结论。最后提出了改变飞艇重心位置的方法。     

陆用定位定向系统定位精度标准检测线设计

定位定向系统是自行火炮的核心设备,其定位精度直接影响火控系统射击诸元计算的准确性,是关键的战术技术指标。针对定位定向系统的定位精度在不同路线上的试验结果表现出的较大差异且陆用定位定向系统鉴定领域检测线不规范等问题,研究定位定向系统的定位误差产生机理,根据里程计标度因数误差和航向角误差这两种主要误差与定位误差定量关系,分析检测路形、路况对定位精度的影响,并通过行车实验验证了理论分析的准确性。考虑到建造成本和试验成本的实际问题,同时兼顾测试效率和工程可实现性,设计了一条简洁等效定位精度标准检测线,提出了定位定向系统定位精度试验场建设方案和选取最优原则,为科学鉴定定位定向系统的定位精度提供理论依据。     

基于车辆运动约束的里程计误差在线标定方法

为了降低里程计误差对捷联惯导/里程计组合定位定向精度的影响,提出了基于车辆运动约束条件的里程计误差在线标定方法。通过对里程计标度因数误差进行建模,推导建立了航位推算的误差模型,将航位推算的速度输出沿车体横向、垂向的投影作为量测的一部分,将捷联惯导输出的速度、位置信息与航位推算输出的对应信息相减作为另一部分量测,通过卡尔曼滤波获得里程计标度因数误差等状态量的最优估计值,实现里程计误差的在线标定。仿真结果表明,该方法能够有效地标定出里程计标度因数误差,从而确保了捷联惯导/里程计组合定位定向的精度。