平面光波导精密对准平台运动误差的敏感性分析

在阵列光纤与波导芯片的对准过程中,多自由度精密运动平台的运动精度直接影响其耦合效率。针对此问题,运用多体动力学理论,通过分析运动平台的各项误差源,建立了多自由度精密运动平台的误差模型。采用基于方差的Sobol法对运动平台的各项误差进行敏感性分析,从而得到了各误差参数在敏感方向的影响程度。试验结果与理论分析结果基本吻合,说明该模型具有一定的适用性。该模型可为多自由度精密运动平台的运动精度控制、误差补偿分析以及系统优化设计提供借鉴。     

助推器分离预试验设计及仿真分析

设计了模拟大型助推器分离的预试验系统,利用8个系统参数建立了参数化刚体动力学模型,优化设计后得到了满足运动姿态模拟要求的系统参数设计值。分析了运动姿态模拟效果对不同参数的敏感性,并对敏感性高的参数进行了误差控制。通过预试验得到了模拟件的运动姿态参数,与仿真计算结果的一致性较好。     

3自由度气浮台力学性能研究——自重作用下平台结构平衡敏感性分析

基于运动弹性动力学理论建立3自由度气浮台平台的力学模型。根据航天器姿态动力学理论推导出自重作用下在气浮台姿态变化过程中平台质心变化公式和所需配重公式,从而获得气浮台平台不平衡力矩的计算公式。应用有限元法计算不同结构参数值组合时平台自重变形产生的不平衡力矩;探究结构各方向刚度相同时参数的变化对不平衡力矩的影响,提出使平台结构不平衡力矩为零的平衡点概念;分析平台结构参数变化对不平衡力矩影响大小即平衡敏感性与平台结构刚度之间的关系。结果表明,平台结构中存在许多使平台各方向刚度相等从而不产生不平衡力矩的平衡点。在每个平衡点处,结构参数值的略微变化对平台自重变形产生的不平衡力矩影响相差很大。结构刚度越大,结构参数值变化对平台自重变形产生的不平衡力矩影响越小,即平衡敏感性越低。     

直角坐标串并联机器人及其冗余驱动运动参数敏感性分析

直角坐标串并联机器人的运动平台在运动过程中保持特殊形式的前提下,机构的运动学反解唯一确定,通过对6个直线输入运动参数分别对输出主轴在空间的位置和姿态的敏感性的实证研究与分析,得出机构的上层动平台和下层动平台的输入运动参数对输出主轴的空间位置和姿态变化的敏感性方面所起的不同关键作用,同时还对该机器人的冗余驱动结构形式的敏感性也做了分析,从而知道各输入运动参数在影响输出主轴位姿变化上的差异.     

DELTA机器人逆运动学的分析与控制

为实现DELTA机器人高效离线编程,根据机械结构,对传动杆件简化并分析运动学逆解,建立了运动学逆解方程和伺服电机与移动平台之间运动关系;根据机器人D-H坐标系参数,采用MATLAB建立三维模型;通过界面控制移动平台末端运动,求解出各运动杆件的运动参数。仿真分析表明:所述方法能够正确建立DELTA机器人模型,并可实现逆运动学求解。     

基于灵敏度分析与优化的精密运动平台模型修正

针对超精密运动平台部件中部分材料精确参数未知、粘结层准确模拟困难导致动力学建模精度相对较低的问题,提出一种基于参数灵敏度分析和优化的模型修正方法,获取面向精确动力学分析所需的高精度动力学模型.建立虚拟材料属性的粘结层单元代替原有的节点重合建模方法,利用参数灵敏度分析得到未知材料参数对结构模态影响的大小,以模态实验结果为目标选取灵敏度大的未知的材料参数进行优化,得到超精密运动平台部件的修正模型.实验结果证实,修正后动力学模型的模态频率及传递函数与实验结果之间的误差较修正前均明显降低,可用于后续超精密运动平台整体动力学特性的精确预测.     

半主动控制液压悬置动特性研究

建立半主动控制液压悬置的力学模型，推导出动刚度、动阻尼和传递率的数学模型，研究惯性通道内阻尼力的表达式，并依次改变悬置的这些主要结构参数，对悬置动特性进行仿真，观察各参数改变对悬置动特性的影响，以便得到较好的隔振效果。     

3自由度精密定位平台的运动特性和优化设计

为了实现3-RRR柔顺并联精密定位平台的精确运动,研究了它的封闭形式精确运动模型和尺寸优化设计。采用卡氏第二定理建立精密定位平台的封闭式柔度模型。根据柔顺并联机构的结构特点,将其划分为3个对称分布的运动支链,并结合铰链的柔度模型和机构力传递关系分别推导出各个支链的刚度模型,整个系统的刚度为所有支链在同一坐标系下的刚度的叠加。建立的刚度模型是以柔性铰链的柔度为变量的封闭形式模型。根据柔度矩阵可得到反映输入位移和输出位移之间关系的雅可比矩阵。理论模型与有限元分析的比较结果显示,两者所得的运动模型误差为1.0%～9.5%,证明了所推导运动模型的正确性和精确性。根据雅可比矩阵的封闭公式,分析其对结构参数的灵敏度,并由此选出对平台运动特性影响较大的优化设计变量。提出以最大化平台工作空间为目标,以铰链强度、最大输入力、几何尺寸和输入耦合为约束的优化模型。结果表明,优化后的结构参数能获得更大的输出位移,说明该方案能满足优化设计要求。     

溢流式高速缓冲气缸动力学建模与性能分析

针对具有内置溢流阀的溢流式高速缓冲气缸建立了非线性动力学模型,并运用Simulink软件建立仿真模型进行数值计算,得到气缸在缩回运动过程中的位移、速度以及各腔室压力的仿真数值解。为了验证仿真模型的正确性,搭建了高速气缸缓冲性能测试平台,对气缸在运动过程中的相关动态参数进行试验测试,通过试验数据与仿真结果的对比分析来对仿真模型进行验证。最后通过仿真分析了内置溢流阀的阀芯质量和预紧弹簧刚度对气缸缓冲性能的影响,结果表明,不同的溢流阀阀芯质量和预紧弹簧刚度都对气缸缓冲性能有较大的影响,为进一步研制更高性能的高速气缸缓冲结构提供了重要依据。     

直角坐标串并联机构奇异位形动力学分析

全新结构的直角坐标串并联机构处于奇异位形时,通过建立动力学方程和欧拉方程,对机构动平台各铰点处的受力状况进行了全面的分析.在给定空间位置和姿态下,已知机构输出端的受力、主轴的运动参数、连杆的运动参数、水平和垂直运动滑块的运动参数,可反向求出它们的动力学反解,并通过计算机语言编程计算和绘图得到直观有效的结果数据.     

Compliance modeling and analysis of a 3-RPS parallel kinematic machine module

The compliance modeling and rigidity performance evaluation for the lower mobility parallel manipulators are still to be remained as two overwhelming challenges in the stage of conceptual design due to their geometric complexities. By using the screw theory, this paper explores the compliance modeling and eigencompliance evaluation of a newly patented 1T2R spindle head whose topological architecture is a 3-RPS parallel mechanism. The kinematic definitions and inverse position analysis are briefly addressed in the first place to provide necessary information for compliance modeling. By considering the 3-RPS parallel kinematic machine（PKM） as a typical compliant parallel device, whose three limb assemblages have bending, extending and torsional deflections, an analytical compliance model for the spindle head is established with screw theory and the analytical stiffness matrix of the platform is formulated. Based on the eigenscrew decomposition, the eigencompliance and corresponding eigenscrews are analyzed and the platform＇s compliance properties are physically interpreted as the suspension of six screw springs. The distributions of stiffness constants of the six screw springs throughout the workspace are predicted in a quick manner with a piece-by-piece calculation algorithm. The numerical simulation reveals a strong dependency of platform＇s compliance on its configuration in that they are axially symmetric due to structural features. At the last stage, the effects of some design variables such as structural, configurational and dimensional parameters on system rigidity characteristics are investigated with the purpose of providing useful information for the structural design and performance improvement of the PKM. Compared with previous efforts in compliance analysis of PKMs, the present methodology is more intuitive and universal thus can be easily applied to evaluate the overall rigidity performance of other PKMs with high efficiency.     

并联机构主轴平台几何建模与仿真的一种方法

在对并联机构主轴平台结构分析的基础上,运用参数化设计软件Pro/e对其中的零部件进行了建模,并应用一定的装配关系和约束条件对这些零部件模型进行装配,由此完成了串并联型机床的几何模型;通过此模型运用Animation功能实现了运动主轴平台的仿真。     

一种新型2-DOF并联主轴平台机构运动学分析

提出了一种新型2-PRR两自由度并联主轴平台机构,介绍了其机构组成及其结构特点。针对此平台机构,建立了运动学方程,给出了机构的位置正反解,并绘制了所有正反解构成的空间曲面,由此得到了平台机构的工作空间。最后,基于雅克比矩阵,对平台机构进行了运动仿真研究,为并联主轴平台机构运动参数的正确设计及控制提供了理论依据。     

Dynamic Modeling and Eigenvalue Evaluation of a 3-DOF PKM Module

Due to the structural complexity, the dynamic modeling and quick performance evaluation for the parallel kinematic machines (PKMs) are still to be remained as two challenges in the stage of conceptual design. By using the finite element method and substructure synthesis, this paper mainly deals with the dynamic modeling and eigenvalue evaluation of a novel 3-DOF spindle head named the A3 head. The topological architecture behind the proposed A3 head is a 3-RPS parallel mechanism, which possesses one translational and two rotational capabilities. The mechanical features of the A3 head are briefly addressed in the first place followed by inverse position analysis. In the dynamic modeling, the platform is treated as a rigid body, the RPS limbs as the continuous uniform beams and the joints as lumped virtual springs. With the combination of substructure synthesis and finite element method, an analytical approach is then proposed to formulate the governing equations of motion of system using the compatibility conditions at interface between the limbs and the platform. Consequently, by solving the eigenvalue problem of the governing equations of motion, the distribution of lower natural frequencies of the A3 head throughout the entire workspace can be predicted in a quick manner. Modal analysis for the A3 head reveals that the distributions of lower natural frequencies are strongly related to the mechanism configuration and are axially symmetric due to system kinematic and structural features. The sensitivity analysis of the system indicates that the dimensional parameters of the 3-RPS mechanism have a slight effect on system lower natural frequencies while the joint compliances affect the distributions of lower natural frequencies significantly. The proposed dynamic modeling method can also be applied to other PKMs and can effectively evaluate the PKM's dynamic performance throughout the entire workspace.     

A two-step calibration methodology of multi-actuated mechanical servo press with parallel topology

We present a two-step calibration methodology of multi-actuated mechanical press with parallel topology and illustrate the method with a case study of a dual-actuated servo press with parallel topology. The kinematic model of the servo press is established firstly. From the total differentials of the kinematic equations, the error sensitivity matrix is obtained to find out linear dependent parameters and the effects of kinematic parameters on the press accuracy are studied. It is found that the press mechanism has the advantage that the press accuracy at the working area is less sensitive to the kinematic parameter errors. The experiment is carried out to measure the motions of the moving platform and slider. By the kinematic error model, the kinematic parameters of the active and passive chains are identified, respectively. Experimental results show that the accuracy of the servo press improves by 82% after kinematic calibration.     

Uncertainty propagation in calibration of parallel kinematic machines

This paper outlines in detail a method for determining the uncertainty present in the kinematic parameters (joint locations, initial strut lengths, and spindle location and orientation) for parallel kinematic devices after calibration. The uncertainty estimation method using Monte Carlo simulations was applied to a sequential method for determining the kinematic parameters of fully assembled Hexel Tornado 2000 (a 6–3 Stewart platform) milling machine. Results for the uncertainty present in the kinematic parameters of a Hexel Tornado 2000 milling machine after calibration using a SMX 4,000 laser tracker are shown.     

结构参数对大型射电望远镜舱索并联机构奇异性的影响

与Stewart平台机构相似，大型射电望远镜舱索并联机构存在奇异性问题。在舱索机构开环运动控制模型的基础上，探讨了结构参数对奇异性的影响，找到了通过修改结构参数消除奇异性的方法，给出了设计参数可行域。计算机仿真和模型现场实验证明了设计方法的可行性。     

Modelling,kinematic parameter identification and sensitivity analysis of a Laser Tracker having the beam source in the rotating head

This paper presents a new kinematic model, a parameter identification procedure and a sensitivity analysis of a laser tracker having the beam source in the rotating head. This model obtains the kinematic parameters by the coordinate transformation between successive reference systems following the Denavit–Hartenberg method. One of the disadvantages of laser tracker systems is that the end-user cannot know when the laser tracker is working in a suitable way or when it needs an error correction. The ASME B89.4.19 Standard provides some ranging tests to evaluate the laser tracker performance but these tests take a lot of time and require specialized equipment. Another problem is that the end-user cannot apply the manufacturer’s model because he cannot measure physical errors. In this paper, first the laser tracker kinematic model has been developed and validated with a generator of synthetic measurements using different meshes with synthetic reflector coordinates and known error parameters. Second, the laser tracker has been calibrated with experimental data using the measurements obtained by a coordinate measuring machine as nominal values for different strategies, increasing considerably the laser tracker accuracy. Finally, a sensitivity analysis of the length measurement system tests is presented to recommend the more suitable positions to perform the calibration procedure.     

数控车床主轴单元结构节能性优化设计

为降低数控车床使用过程中的能耗,针对主传动系统中的主轴部件提出一种面向节能的结构优化设计方法.首先构建主轴单元功率模型并分析其动静态性能指标;然后基于均匀试验和灵敏度分析,选取对主轴单元能耗和动静态性能影响较大的尺寸参数作为优化变量,再通过响应面法拟合指标函数;之后利用主成分分析法降低函数维度,建立主轴单元结构节能设计...