Reliability Analysis of Satellite Turntable System under Multiple Operation Modes Based on Multi-Valued Decision Diagrams

As a payload support system deployed on satellites,the turntable system is often switched among different working modes during the on-orbit operation,which can experience great state changes.In each mode,the missions to be completed are different,consecutive and non-over-lapping,from which the turntable system can be considered to be a phased-mission system(PMS).Reliability analysis for PMS has been widely studied.However,the system mode cycle characteristic has not been taken into account before.In this paper,reliability analysis method of the satellite turntable system is proposed considering its multiple operation modes and mode cycle characteristic.Firstly,the multi-valued decision diagrams(MDD)manipulation rules between two adjacent mission cycles are proposed.On this basis,MDD models for the turntable system in different states are established and the reliability is calculated using the continuous time Markov chains(CTMC)method.Finally,the comparative study is carried out to show the effectiveness of our proposed method.

Load-induced error identification of hydrostatic turntable and its influence on machining accuracy

In heavy duty machine tools, hydrostatic turntable is often used as a means for providing rotational motion and supporting workpiece, so the accuracy of turntable is crucial for part machining. In order to analyze the influence of load-indcued errors on machining accuracy, an identification model of load-induced errors based on the deformation caused by applied load of hydrostatic turntable of computerized numerical control(CNC) gantry milling heavy machine is proposed. Based on multi-body system theory and screw theory, the space machining accuracy model of heavy duty machine tool is established with consideration of identified load-induced errors. And then, the influence of load-induced errors on space machining accuracy and the roundness error of a milled hole is analyzed. The analysis results show that load-induced errors have a big influence on the roundness error of machined hole, especially when the center of the milled hole is far from that of hydrostatic turntable.

Fault detection of switched linear systems with its application to turntable systems

This paper is concerned with the H∞ fault detection for continuous-time linear switched systems with its application to turntable systems.The solvability condition for a desired filter is established based on the proposed sufficient condition.Based on the double channel scheme of the turntable control system,the turntable system can be modeled as a switched system.Finally,by taking the turntable system as a numerical example,the effectiveness of the proposed theory is well validated.

Research on identifying the dynamic error model of strapdown gyro on 3-axis turntable

The dynamic errors of gyros are the important error sources of a strapdown inertial navigation system. In order to identify the dynamic error model coefficients accurately, the static error model coefficients which lay a foundation for compensating while identifying the dynamic error model are identified in the gravity acceleration fields by using angular position function of the three-axis turntable. The angular acceleration and angular velocity are excited on the input, output and spin axis of the gyros when the outer axis and the middle axis of a three-axis turntable are in the uniform angular velocity state simultaneously, while the inner axis of the turntable is in different static angular positions. 8 groups of data are sampled when the inner axis is in 8 different angular positions. These data are the function of the middle axis positions and the inner axis positions. For these data, harmonic analysis method is applied two times versus the middle axis positions and inner axis positions respectively so that the dynamic error model coefficients are finally identified through the least square method. In the meantime the optimal angular velocity of the outer axis and the middle axis are selected by computing the determination value of the information matrix.

Axis intersection measurement of three-axis turntable with two crosshair targets

In order to measure three-axis intersection error, two crosshair targets were fixed in the inner axis frame of a three-axis turntable. Also a theodolite was used to point its telescope to the targets and to measure the horizontal angles when three axes were on equi-spaced angle positions. The calculation equations of the axis intersection were deduced from the mounting position of the theodolite, positions of two targets, angular positions of three axes, and the measured horizontal angles with the theodolite. Finally, a practical measurement is carried out on a horizontal three-axis turntable and error analysis is conducted.

Coupling Analysis of Moment of Inertia & Dynamic on Optoelectronic Tracking Turntable

With photoelectric tracking system as the research object,based on the theorem of moment of momentum and Euler dynamic equation,Nonlinear biaxial coupling dynamic model of tracking turntable is established.Effects of moment of inertia coupling,speed coupling and the dynamic coupling between tracking turntable shafts were studied,the analytical relation between them was given in theory.Verify the change trend of theoretical model.And it provides the theory reference and model base,for the future design of the high precision tracking controller And control parameter selection and optimization.In the end,specific measures are made for structure optimization.

An Investigation into the Influence of the Airflow Path on the Convective Heat Transfer for an Eddy Current Retarder Turntable

In order to improve the convective heat transfer relating to an eddy current retarder,the finite element model has been used to assess the performances of different possible designs.In particular,assuming the steady running state of retarder as the working condition,flow and temperature fields have been obtained for the rotor.The influence of airflow path on heat dissipation has been analysed,and the influence of the temperature field distribution on the performance of retarder has been discussed accordingly.The results show that when the steady running state of the turntable is considered,the maximum temperature is lower,the level of turbulence flow is mitigated,and the temperature distribution becomes more regular.These factors contribute to improve the heat dissipation ability of the retarder.

USB Turntable

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Analysis and Research on the Load of the Box Girder Locomotive Turntable

The locomotive turntable is an essential device for the steering operation of the railway locomotive. This paper has introduced the structural composition and characteristics of the box girder locomotive turntable, has ana- lyzed its vertical load, horizontal load and torsional load, and has established a mechanical model for the symmet- rical structure of the box girder locomotive turntable under the action of positive and negative symmetric vertical loads. Furthermore, it has also demonstrated the safe and reliable structural performance of this type of locomotive turntable on the basis of the practical example of a 35 m box girder locomotive turntable.

Dynamic error research and application of an angular measuring system belonging to a high precision excursion test turntable

Angular measuring system is the most important component of a servo turntable in inertial test apparatus. Its function and precision determine the turntable’s function and precision. It attaches importance to research on inertial test equipment. This paper introduces the principle of the angular measuring system using amplitude discrimination mode. The dynamic errors are analyzed from the aspects of inductosyn, amplitude and function error of double-phase voltage and waveform distortion. Through detailed calculation, theory is provided for practical application; system errors are allocated and the angular measuring system meets the accuracy requirement. As a result, the schedule of the angular measuring system can be used in practice.

雷达转台液压系统可靠性影响评价预测研究

针对当前雷达液压系统可靠性合理建模及影响评价体系难以构建及评估的现状,以某典型机载雷达转台液压系统为研究对象,提出一种基于危害性分析的可靠性影响评价预测方法。利用模糊判断矩阵以获得指标的权重系数,对可靠性进行建模仿真分析,从而为准确预测系统的可靠性提供理论支撑。在此基础上,通过对转台液压系统故障原因进行全面梳理,构建了液压系统可靠性影响评价体系。运用Elman网络,结合实证分析对可靠性影响评价模型进行预测,为雷达转台液压系统故障的综合分析提供了整体解决方案。这也为进一步提高雷达液压系统的可靠性提供了合理思路。该研究可为雷达其他分系统可靠性分析提供参考。

考虑多工况的甘蔗收割机回转台轻量化研究

甘蔗收割机回转台在工作过程中承受过双侧凹坑、转向过坑等工况载荷及扭矩的作用,受力复杂,优化时需要多工况综合考虑。ESO多工况优化方法由于未考虑不同工况间的重要程度,不易获得全局最优解。因此提出一种多目标拓扑优化函数,采用带权重的线性加权法协调多个目标函数,构建多工况拓扑优化数学模型,运用层次分析法确定各工况的权重系数,基于inspire软件对回转台进行多目标拓扑优化,从而获得材料的最优分布。优化结果表明:优化后回转台结构最大应力与最大位移均有所下降且满足强度与刚度要求,实现了多目标同时优化。

动态病例情景结合快速评估转盘在出血评估技术工作坊中的应用

目的评价快速评估转盘应用于工作坊的培训模式对提高专科护士出血评估技术的效果。方法选取2022年1—12月在广州某三甲医院妇产科培训基地参加脱产专科培训的65名护士为研究对象,采用随机数字表法分为对照组(n=32)和研究组(n=33)。对照组在基于临床真实改编案例的工作坊进行实践练习,研究组在此基础上应用快速评估转盘练习评估技术,应用柯氏4级评估模式(反应、学习、行为和结果)对两组培训效果进行评价。结果研究组对培训形式、效果及总体满意度均高于对照组,出血量的评估效率及液体复苏的掌握率均明显高于对照组,且评估时间缩短至(8.82±2.13)min,两组间差异有统计学意义(t=8.38,P<0.05)。结论研究组学员对于快速评估转盘在出血评估技术工作坊的应用满意度较高,认为能显著提高对出血量的评估效率及液体复苏的掌握率,有一定的临床推广价值。

基于多软件平台的二维重载精密转台的控制特性仿真分析及优化

为提高二维重载精密转台动态特性,基于AMEsim、ADAMS以及Simulink多软件机电一体化联合仿真对系统控制特性进行仿真分析.本文使用AMESim建立电机模型,Adams建立二维重载系统的动力学模型,使用Simulink工具箱建立PID控制模型,最终建立三软件联合仿真模型对系统阶跃响应进行仿真分析;针对系统存在时变性、非线性和负载干扰等因素的问题,采用自适应模糊PID控制算法对系统进行控制优化.仿真结果表明,模糊PID控制算法有着响应快、无超调,稳定误差较普通PID控制减小37%左右等优点.

并联结构轴系回转误差建模及装配优化

为提高光电经纬仪等二维转台的轴系运动精度,本文基于雅可比旋量理论建立了一种可考虑零件结构误差及其耦合放大效应的数学模型。针对“一端固定、一端游动”的轴系结构,提出了局部并联结构的分析方法。通过数值仿真分析,获得了各零件结构误差对轴系运动精度的影响以及最优的轴系装配方案。光学口径为650 mm的光电经纬仪的装调结果表明:装配优化后的轴系运动精度较优化前提高了32.1%。所构造的轴系运动精度模型及优化方法为指导光电经纬仪等二维转台的轴系装调以及公差设计提供了一定的理论根据。

自动化专业实验创新平台设计与教学研究

面向新工科背景下培养创新人才的需求,结合目前自动化专业学生培养的现状,参照飞行器地面半实物仿真测试装备,开发并搭建了模拟飞行转台实验创新平台。该实验创新平台由机械结构、驱动系统、控制系统、人机交互界面和通信接口共同组成,可以实现俯仰、偏航和滚转的三自由度姿态模拟。教学实践结果表明,该平台不仅为学生提供被控对象拟合、PID控制器设计等基础实验,还可根据学生创新需求,使用预留接口自主设计创新实验;同时,具有形象生动、轻便易携带、人机交互简便、接口丰富、功能拓展性强等优势。

基于转台的多视角多姿态锁销点云模型重建

集装箱锁销曲面结构复杂,因而建立出一个曲面特征完整度较高的点云模型较为困难.考虑到在大多数场景下,位于固定高度的传感器搭配旋转的转台采集的曲面特征通常会存在一定的缺失.为此,提出了一种基于转台的多视角多姿态点云模型重建算法,还原锁销较完整的曲面特征.首先,利用转台参数标定结果,实现多视角三维点云的拼接,建立一个固定姿态下的点云模型;其次,通过提出的改进球面投影算法,选取锁销置于转台的摆放姿态,建立另一姿态下的点云模型;最后,融合多个姿态下的点云模型,提高其具备的曲面特征.实验结果表明,所提出的算法能建立出曲面特征完整度较高的锁销点云模型.

基于希尔伯特-黄变换的转台角速率测量方法研究

文中针对传统转台角速率测量采用定时测角、定角测时等时间段内求取平均值方法,无法获取转台随时间变化的瞬时角速率值的问题,对基于希尔伯特-黄变换原理的角速率测量方法开展研究。在分析莫尔信号自身特征的基础上,对莫尔信号进行希尔伯特-黄变换方法进行详细阐述;设计基于FPGA的角速率测量电路,详细说明了电路中经验模态分解设计方法。搭建转台转速测量实验平台验证希尔伯特-黄角速率测速效果,实验结果证明希尔伯特-黄角速率测量方法对比传统定时测角法的优越性;120(°)/s内的多个转速的实验显示希尔伯特-黄角速率测量方法角速率测量误差小于0.9×10^(-3),角速率测量稳定性优于0.5×10^(-4)。

基于模拟软件的上转盘铸件铸造工艺设计

介绍了灰铸铁上转盘铸件的结构及技术要求,根据铸件的结构特点,对其进行了工艺性分析。详细阐述了铸件的分型面、浇注系统、冒口以及冷铁的设计,并借助计算机模拟软件分析了铁液的充型过程及凝固过程,根据模拟结果选择优良的浇注方案,以确保铁液充型平稳。通过设计调整冒口及冷铁的设置位置与尺寸,建立合理的补缩系统,最大限度降低铸件的气孔和缩孔缺陷。

星载二维转台U型架结构轻量化与优化设计

星载二维转台是空间相机等光电设备的主要承载机构,U型架是转台的关键支撑部件。为了对星载二维转台U型架进行结构优化与轻量化设计,研制高承载比和轻量化的星载二维转台,本文设计了一种用于星载二维转台的碳纤维复合材料U型架。首先,利用碳纤维复合材料代替钛合金材料,结合考虑工艺性,设计了一种变截面管状结构U型架。接着,按照基于铺层工艺的有限元建模方法对碳纤维U型架进行有限元建模与仿真分析。然后,试制U型架样机并通过模态试验验证有限元模型的准确性。最后,提出一种理论分析法、遗传算法、有限元法相结合的三级优化方法对碳纤维U型架铺层角度、铺层厚度与铺层顺序进行优化设计。结果表明:模态试验与仿真得到的U型架振型完全一致,频率相差在5%以内。初始设计的碳纤维U型架比钛合金U型架质量减少了45.7%,通过对复合材料铺层的优化设计,使U型架质量进一步减少了13.8%,固有频率提升了10.14%。本文所采用的复合材料建模与优化方法正确,设计的碳纤维U型架满足星载二维转台轻量化设计需求。