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.

OBSERVER/FILTER STRUCTURE BASED ADAPTIVE FRICTION COMPENSATION FOR HIGH PRECISION TURNTABLE

Two adaptive friction compensation schemes are developed for a high precision turntable system with nonlinear dynamic friction to handle two types of parametric uncertainties in the friction. Both schemes utilize a nonlinear observer/filter structure to compensate for uncertainties in corresponding friction parameters associated with the turntable system. Moreover, in the second scheme, adjustable gains are introduced into the dual nonlin- ear filters and they can be tuned to improve the position tracking performance. In both cases, a Lyapunov-like argument is provided for the global asymptotic stability of the closed-loop system. Simulation results demonstrate the effectiveness of the proposed schemes.

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.

Effect of working parameters on performance characteristics of hydrostatic turntable by using FSI-thermal model

Effects of working parameters on performance characteristics of hydrostatic turntable are researched by applying the fluid-structure-thermal coupled model.Fluid-structure interaction(FSI)technique and computational fluid dynamics(CFD)method are both employed by this new model,and thermal effects are also considered.Hydrostatic turntable systems with a series of oil supply pressures,various oil recess depth and several surface roughness parameters are studied.Performance parameters,such as turntable displacement,system flow rate,temperature rise of lubrication,stiffness and damping coefficients,are derived from different working parameters(rotational speed of turntable and exerted external load)of the hydrostatic turntable.Numerical results obtained from this FSI-thermal model are presented and discussed,and theoretical predictions are in good agreement with the experimental data.Therefore,this developed model is a very useful tool for studying hydrostatic turntables.The calculation results show that in order to obtain better performance,a rational selection of the design parameters is essential.

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.

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 axe analyzed from the aspects of inductosyn, amplitude and function error of double-phase voltage and wavefonn 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.

USB Turntable

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Light pen whole space coordinate measuring system based on a tracking turntable

Light pen coordinate measuring system(LPCMS)is a kind of portable coordinate measuring technique based on vision metrology.In classical LPCMS,the measuring range is limited to the camera’s field of view.To overcome this defect,a new LPCMS is designed in this paper to fulfil whole space coordinate measurement.The camera is installed on a turntable instead of a tripod,so that the camera can rotate to track the movement of the light pen.The new system can be applied to large scale onsite measurement,and therefore it notably extends the application of LPCMS.To guarantee the accuracy of the new system,a method to calibrate the parameters of the tracking turntable is also proposed.Fixing the light pen at a stationary position,and changing the azimuth angles of the turntable’s two shafts,so that the camera can capture the images of the light pen from different view angles.According to the invariant spatial relationship between the camera and the pedestal of the tracking turntable,a system of nonlinear equations can be established to solve the parameters of the turntable.Experimental results show that the whole space coordinate measuring accuracy of the new system can reach 0.25 mm within 10 m.It can be concluded that the newly designed system can significantly expand the measuring range of LPCMS without losing too much accuracy.

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.

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。

某装备天线伺服系统算法研究

论文根据某装备伺服系统实际应用情况,考虑其实时跟踪目标特点,采用了快速最优算法+模糊PID算法相结合的控制策略,有效确保了天线的实时稳定运转。通过实验测试,采用快速最优算法+模糊PID算法的控制策略,天线稳定运行,全系统具有良好的动静态特性。

加工中心核心部件——数控转台关键技术探析

在加工中心发展方兴未艾的今天,其核心部件数控转台的重要性日益凸显。基于此,本文对加工中心数控转台常用产品进行了分类,并指出了常见的应用场景,对数控转台的结构和关键技术进行了总体介绍。希望可以帮助数控转台设计者和选用者理清思路,为数控转台研发技术路径提供参考。

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.