Development of a terrain strength measuring system

An outline of the development of the experimental equipment capable of recording terrain strength tests carried out with a variety of soil probes. The equipment and instrumentation have been designed as a special type of bevameter, because of its capability of parametric soils strength analysis.     

Development of a new temperature measuring system for gas–liquid flow in spraying field

Based on previous work, a new temperature measuring system for gas–liquid flow, composed of shielded and unshielded thermocouples, on-line laser detection device for liquid droplets, vacuum pump and wavelet analysis data processor, is developed in this work. The necessity of vacuum pump and the criterion of mesh size selection are also described. Through an application of measuring temperature in saturator, it shows that the system can evaluate the separation of gas–liquid two-phase flow and measure the liquid droplet temperature and the gas temperature effectively in counter-current spraying field.     

Development of a data acquisition system for measuring the characteristics of real time forces by cage wheels

A new data acquisition system was introduced that could be used to monitor the real time wheel forces to solve the limitations of obtaining precise performance characteristics of actual cage wheels. Contrary to previous methods, in which the cage wheel forces were obtained by summing up the individual lug forces. The new method enables measurement of the components of lug force in three orthogonal directions simultaneously. A single unit dynamometer system, with two extended octagonal rings was designed and fabricated using a solid mild steel block, was able to measure force up to 5 kN in each direction. It was used in a soil-bin test rig to determine the characteristics of the forces produced by a cage wheel with opposing circumferential lugs. The characteristics of the pull and lift forces agreed with measured drawbar pull and calculated wheel forces respectively. The force signals fluctuated periodically with rotation angle and the corresponding period approximately equal to the interval of angular lug spacing. The side force fluctuated between positive and negative values and the average was closer to zero due to the balancing effect of opposing lugs. The new system showed better output compared to the previous attempts, confirming its applicability for accurate measurement of real time wheel forces.     

Development of ship waves in a nonhomogeneous liquid

The article discusses the three-dimensional problem of unsteady-state waves arising on a free surface and at the interface between two liquids of different densities, with motion of the source. Analogous problems for steady-state waves in a two-layer liquid have been investigated in [1–6], and for unsteady-state waves in a homogeneous liquid in [7, 8].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 137–146, July–August, 1970.     

A system for measuring the surface profile of a spinning disk

An autofocusing, laser-based system for measuring the surface topography of a spinning optical-quality disk is described. The essential feature of the system is high resolution of absolute surface profiles with large peak to peak variations. Illustrative experimental results are presented for glass and plastic disks. Applications of the instrument to surface accelerations and thickness measurements are also discussed.     

舰船波浪中航行时的变形分析及其IMU实时测量方法

大型舰船在水面上航行过程由于波浪的作用会产生一定的变形,该变形会降低舰船上姿态信息的精度,影响舰载武器系统的作战效能,针对这一问题,首先对舰船的变形进行理论分析,计算舰船所承受的波浪载荷,将波浪载荷加载到舰船的有限元模型,经计算得到的甲板各节点的角位移及线位移信息,以此来分析舰船的变形。在舰船的关键战位点安装由陀螺仪和加速度计组成的惯性测量单元(IMU),将IMU的输出信息与舰船主惯导的输出信息进行匹配,设计舰船变形估计的卡尔曼滤波器,实时估计IMU安装处的甲板变形角,为舰载武器装备提供准确的局部姿态信息,实验结果证明了所提方法的有效性。     

船舶动力定位系统

随着深海技术的不断发展,动力定位系统的在海洋工程上得到广泛应用。动力定位系统通过其控制系统驱动船舶推进器来抵消风、浪、流等作用于船上的环境外力,从而使船舶保持在确定的位置上或沿预期的航迹航行。本文在分析了国际海事组织和国际海洋工程承包商协会对动力定位系统定义及分级要求的基础上,阐述了国外船舶动力定位系统的发展及其应用状况,分析了动力定位系统的组成和工作原理,研究了动力定位系统的各种约束、控制策略、控制技术、推力分配等关键技术,指出动力定位系统精度取决于控制系统和测量系统性能,并提出了发展国产动力定位系统应采用的途径。     

Measurement of flows around modern commercial ship models

To document the details of flow characteristics around modern commercial ships, global force, wave pattern, and local mean velocity components were measured in the towing tank. Three modern commercial hull models of a container ship (KRISO container ship = KCS) and of two very large crude-oil carriers (VLCCs) with the same forebody and slightly different afterbody (KVLCC and KVLCC2) having bow and stern bulbs were selected for the test. Uncertainty analysis was performed for the measured data using the procedure recommended by the ITTC. Obtained experimental data will provide a good opportunity to explore integrated flow phenomena around practical hull forms of today. Those can be also used as the validation data for the computational fluid dynamics (CFD) code of both inviscid and viscous flow calculations. Received: 26 September 2000/Accepted: 22 May 2001     

Development of a micro-indentation device for measuring the mechanical properties of soft materials

Indentation is a simple and nondestructive method to measure the mechanical properties of soft materials, such as hydrogels, elastomers and soft tissues. In this work, we have developed a micro-indentation system with high-precision to measure the mechanical properties of soft materials, where the shear modulus and Poisson's ratio of the materials can be obtained by analyzing the load–relaxation curve. We have validated the accuracy and stability of the system by comparing the measured mechanical properties of a polyethylene glycol sample with that obtained from a commercial instrument. The mechanical properties of another typical polydimethylsiloxane sample submerged in heptane are measured by using conical and spherical indenters, respectively. The measured values of shear modulus and Poisson's ratio are within a reasonable range.     

激光陀螺组合体测量船体角形变中观测耦合效应的补偿（英文）

船体角形变是传递对准中的主要误差源,需要依靠测量仪器精确标定。根据姿态匹配方法使用两套激光陀螺组合体可以计算角形变。但是动态形变和船体运动角速度的交叉相关的观测耦合效应导致角形变的最优估计结果不准确,并且通过姿态匹配方法这种观测耦合效应是不能被准确测量的,需要结合其它角形变的测量信息进行计算。基于角速度匹配方法,研究了观测耦合效应,并得出其导致角形变估计的偏置误差,且受船体运动角速度调制的结论。通过补偿激光陀螺组合体测量的角速度,降低了观测耦合效应,得到了高精度的对准结果。仿真结果表明观测耦合效应主要导致了静态形变估计精度的不准确。     

船用光纤陀螺航姿系统动态对准

为提高船用航姿系统的对准精度和对准速度，提出了摇摆条件下的两位置对准方案。应用分段线性定常系统理论和可观测度的奇异值分解法，分析了动基座下航姿系统的可观测性和可观测度，并在摇摆台上进行了光纤陀螺航姿系统的两位置对准试验。理论分析结果表明，两位置对准可以提高系统状态变量的可观测度，尤其对加速度计误差和方位失准角的可观测度提高作用明显。摇摆试验的结果则表明，两位置对准可以使方位角对准精度提高3倍以上，同时加快了卡尔曼滤波器的收敛速度。摇摆条件下的两位置对准为船用航姿系统动态对准提供了新的途径。     

陀螺加速度计高速闭环动态测角系统设计

从运载火箭惯性导航系统的核心仪表-陀螺加速度计对测角系统的技术要求出发,设计一种新型的陀螺加速度计高速闭环动态测角系统。它选择变磁阻多级旋转变压器进行角位置测量,并采用两相绕组激磁、一相绕组输出的脉冲调宽型鉴幅的运行方式;在分析其工作原理的基础上,从放大器、控制器、数字函数发生器、输出接口四个方面给出了测角系统的具体设计方法,最后进行了误差测试与跟踪转速测试验证。实测结果表明,采用传感器误差为1.5′的测角系统,分辨率为0.84375′,综合误差约为2.5′,最大跟踪转速为538(°)/s。该系统满足使用要求,设计方案有效可行。     

微机械加速度计自动测试系统

为了精确、高效地测量微机械加速度计的各项性能指标,并尽可能地降低地线干扰,系统采用DAQ-2213数据采集卡采集加速度计输出电压,使用多个独立电源及差模接法来降低地线干扰;温度敏感元件采用Pt100,电阻到电压变换电路采用三线制接法,选择PCI-(A)9114数据采集卡采集变换电路输出的电压值;采用Labview7.0接口函数实时显示加速度计输出电压和温度值,并输出有图表的Word文档.系统经过标定,输出电压精度为40 μV,温度精度为0.277℃.实验表明,系统能实时测量微机械加速度计的输出电压和温度值,而采用独立电源和差模输入可有效减少各路信号之间的干扰.     

Numerical method and models for anti-plane strain of a system with a thin elastic wedge

The paper presents a general method to find asymptotics for a (multi-)wedge system containing a thin wedge. It employs separation of the symmetric and anti-symmetric parts of the boundary displacements and tractions of the wedge. The method is applicable when the angle of the thin wedge turns to zero. A physical interpretation of the derived equations is obtained by using power expansions of non-polynomial functions, which appear after the Mellin transform. We establish that the first term in the expansion of the symmetric part corresponds to shear, while the first term of the anti-symmetric part describes deflection of the wedge axis. Numerical experiments, performed by using a code developed on the basis of the theory, show that using only the first terms of the expansions insignificantly influence accuracy: the approximate results coincide with the exact values of roots to the third significant digit even for the wedge angle of 30°.     

Laser-dual-focus system for measuring the flow through narrow rod bundles

A non-disturbing optical instrument for the measurement of flow velocity in complicated flow channels, e.g. inclined flow through rod bundles is described. The measuring probe based on the laser-dual-focus principle is brought inside one of the plexiglass tubes forming the grid. A mirror which is situated inside the probe deflects the two laser beams producing the measuring volume into the flow field to be examined. An optical system for a thin probe has been developed which has to fit into one of the rods and which enables one both to produce the measuring volume as well as to receive the back-scattered light. The required laser power can be reduced to 2 mW. The photo-multiplier necessary for the evaluation of scattered light signals can be separated from the optical head by using light wave conductors. Examples are presented by which the applicability of the new probe to the described flow situation is demonstrated.     

Melnikov analysis for a ship with a general roll-damping model

In the framework of a general roll-damping model, we study the influence of different damping models on the nonlinear roll dynamics of ships through a detailed Melnikov analysis. We introduce the concept of the Melnikov equivalent damping and use phase-plane concepts to obtain simple expressions for what we call the Melnikov damping coefficients. We also study the sensitivity of these coefficients to parameter variations. As an application, we consider the equivalence of the linear-plus-cubic and linear-plus-quadratic damping models, and we derive a condition under which the two models yields the same Melnikov predictions. The free- and forced-oscillation behaviors of the models satisfying this condition are also compared.