CONCISE SOLUTION OF FORWARD KINEMATICS ANALYSIS OF PARALLEL MECHANISM IN 6-SPS SIMILAR PLATFORM

The forward kinematics analysis of a special 6-SPS Stewart platform is presented, in which both the base and the mobile platforms are hexagon and similar to each other. The forward kinematics of the parallel mechanism is a complicated nonlinear problem, however. there exists a class of parallel kinematics platforms that have the simplest forward kinematics. By introducing quaternion to represent the rotary transformation matrix and applying dual space method to eliminate the high degree polynomials, the forward kinematics can be expressed by a set of quadratic algebra equations, which decouple the position and the orientation of the mobile platform. The approach only requires solving one-variable quadratic equations. Besides, spurious complex roots are automatically avoided. Eight possible solutions are obtained from the approach. It discovers the inner symmetry relationship between the solutions of the forward kinematics.

NOVEL 6-SPS PARALLEL 3-DIMENSIONAL PLATFORM MANIPULATOR AND ITS FORCE/MOTION TRANSMISSION ANALYSIS

The unique design for a novel 6-SPS parallel 3-dimensional platformmanipulator with an orthogonal configuration is investigated. The layout feature of the parallelmanipulator is described. Its force/motion transmission capability, evaluation criteria arepresented. At the orthogonal configuration, the criteria and the relationships between the criteriaand the link lengths are analyzed, which is important since it can provide designer a piece ofvaluable information about how to choose the linear actuators. From the analysis of the results itis shown that the force/motion transmission capabilities of the parallel manipulator arecharacterized by isotropy at the orthogonal configuration. The manipulator is particularly suitablefor certain applications in 6-DOF micromanipulators and 6-axis force/moment transducers.

STRUCTURAL PARAMETERS CALIBRATION BY POSTURE MEASUREMENT ON PARALLEL 6-DOF PLATFORM

Some approaches to measure parallel 6-degree of freedom platform's posturestatically and to calibrate the platform's actual structural parameters by measuring a series of theplatform's varying postures are studied. In the case where high posture accuracy is requiredrelatively, to obtain the platform's actual structural parameters is very important. Threedimensions measurement with 2 theodolites are used to obtain the platform's postures statically andNewton iterative method is adopted to calibrate structural parameters. Some measures taken in themeasurement and the calibration are discussed in detail. And the experiment results of theplatform's posture control before and after the calibration are given. The results show that theplatform's posture control accuracy after the calibration is improved notably.

Cross-coupling integral adaptive robust posture control of a pneumatic parallel platform

A pneumatic parallel platform driven by an air cylinder and three circumambient pneumatic muscles was considered. Firstly, a mathematical model of the pneumatic servo system was developed for the MIMO nonlinear model-based controller designed. The pneumatic muscles were controlled by three proportional position valves, and the air cylinder was controlled by a proportional pressure valve. As the forward kinematics of this structure had no analytical solution, the control strategy should be designed in joint space. A cross-coupling integral adaptive robust controller(CCIARC) which combined cross-coupling control strategy and traditional adaptive robust control(ARC) theory was developed by back-stepping method to accomplish trajectory tracking control of the parallel platform. The cross-coupling part of the controller stabilized the length error in joint space as well as the synchronization error, and the adaptive robust control part attenuated the adverse effects of modelling error and disturbance. The force character of the pneumatic muscles was difficult to model precisely, so the on-line recursive least square estimation(RLSE) method was employed to modify the model compensation. The projector mapping method was used to condition the RLSE algorithm to bound the parameters estimated. An integral feedback part was added to the traditional robust function to reduce the negative influence of the slow time-varying characteristic of pneumatic muscles and enhance the ability of trajectory tracking. The stability of the controller designed was proved through Laypunov's theory. Various contrast controllers were designed to testify the newly designed components of the CCIARC. Extensive experiments were conducted to illustrate the performance of the controller.

An Inverse Kinematic Analysis Modeling on a 6-PSS Compliant Parallel Platform for Optoelectronic Packaging

Multiple degree of freedom motion platform is always one of the important components in optoelectronic packaging systems,its characteristics have a vital impact on the performances of optoelectronic packaging.This paper presents a 6-Prismatic-Spherical-Spherical compliant parallel platform for optoelectronic packaging.This platform is a kind of parallel layout structure,which uses the piezoelectric motors as active joints and the large-stroke flexure hinges are employed as passive joints.An inverse kinematic modeling based on elastokinematic analysis is analyzed and deduced.The elastokinematic analysis considers the elastic deformation of the large-stroke flexure hinges in movement process,and improves the positioning accuracy of the compliant parallel platform in applications.The finite element analysis model and the prototype of the compliant parallel platform are developed,and the validity of the proposed method is finally verified.This paper provides a theoretical reference and experimental data for the inverse kinematic analysis of six degrees of freedom motion compliant parallel platforms with large-stroke flexure hinges.

Orientation density and workspace analysis of a parallel stabilized platform testing system

An optimized workspace calculation method is proposed for parallel stabilized platform testing systems.This method refines the searched space progressively in order to approach the boundary of the workspace from both the inside and the outside of it.The orientation density is defined and used as an evaluation index to calculate the orientation workspace.The algorithm of the orientation density is embedded into the computer program of the workspace calculation.Then the workspaces of the testing system are solved.In the solution,the orientation density is regarded as a discrete function of the reachable workspace.As a result,the reachable workspace and the orientation workspace are represented in the same multidimensional graphs.Finally the useful workspace of the testing system is determined based on these results.This case study indicates that the calculation efficiency is enhanced by adopting the optimized method and the practicability of workspace study is improved by proposing the orientation density.

Spark平台下基于互信息计算的高光谱图像波段选择方法

随着遥感成像技术的发展和普及,高光谱图像中大量的波段使得大多数应用研究遇到休斯现象。而且随着高光谱图像数据量的快速增长,现有的传统串行算法计算复杂度较高,难以处理高维海量高光谱图像数据。针对以上问题,提出Spark平台下基于互信息计算的波段选择算法。利用熵和互信息理论定义波段相关性和多重相关性;基于Spark RDD编程模型设计数据列变换,将数据集划分为列矩阵,以降低计算负载;在Spark平台下对算法并行化,提高算法执行效率。实验结果表明,提出的算法达到了94.5%±0.5的整体分类精度,且加速性能良好,改善了数据可扩展性。

六自由度并联平台惯性参数辨识方法

惯性参数辨识对多自由度并联机构动力学控制至关重要,而传统的辨识方法存在操作复杂、精度差等问题。现提出一种基于动力学分析的六自由度并联平台惯性参数辨识方法。该方法以伺服电机的驱动电流为基础,采用Kane法对并联机构进行动力学分析,建立电流、转矩和推力之间的传递函数,在此基础上构建激励力与平台位姿的辨识方程,即可求解并联平台的惯性参数。基于MATLAB与ADAMS的六自由度并联平台参数辨识仿真分析结果表明,质量与转动惯量辨识误差分别小于2%与7%。与解体测量法和CAD法相比,本方法具有更快的辨识速度与更高的辨识精度,为并联平台动力学控制打下基础。

电液3-UPS/S并联稳定平台参数振动特性分析

针对电液3-UPS/S并联稳定平台驱动液压缸的压力脉动所产生的参数振动,建立了稳定平台的参数振动方程并利用多尺度法求解了主共振响应与组合共振响应的一次近似解;分析了主共振与组合共振响应特性以及振动幅值在初始工作空间内的变化规律,最后采用四阶龙格库塔法与模态试验对参数振动模型进行验证。结果表明:数值解与理论解之间的最大误差为4.20%,固有频率理论值与试验值之间的最大误差为4.66%,可验证参数振动模型的正确性。

面向跨平台可复用组件的交叉编译工具设计与实现

伴随着软件三化(通用化、系列化、组合化)的发展,军用领域软件跨平台可复用已成为一种趋势。针对这一趋势,文章设计并实现一种面向跨平台可复用组件的一体化交叉编译工具。首先介绍了基于组件框架的组件跨平台技术,其次从工具链管理、项目向导、并行构建管理等方面进行了交叉编译工具的设计,最后通过实现的编译工具同时编译出龙芯锐华、DSP锐华和ARM麒麟等多个目标平台的组件目标文件。实验结果表明,该交叉编译工具可支持组件的跨平台复用,提升了软件的复用性和可移植性,具有重要的理论和现实意义。

3UPU-UP并联平台可操作性与工作空间分析

6支链并联平台存在着复杂的位置约束,并且当控制算法失效时对机械结构容易造成损坏,因此,针对一种3UPU-UP并联平台对其进行运动学可操作性与工作空间分析。首先通过矢量法与运动学的分析,得出了3UPU-UP并联平台运动学模型,以此为基础,首次将串联机械臂可操作度的评价指标与3UPU-UP并联平台的机构结构特性相结合,对3UPU-UP并联平台的可操作度进行了计算、分析和可视化处理;并将蒙特卡洛法与正运动学相结合对并联平台的工作空间进行了计算、分析和可视化处理。能够更加直观、完整表述并联平台的可操作度和工作空间。研究成果为3UPU-UP并联平台的设计提供了理论依据并证实其理论上的可行性。

面向国产异构DCU平台的大规模并行矩量法研究

面向国产异构众核处理器超级计算机发展趋势,实现了基于CPU+DCU国产异构并行系统的大规模并行高阶矩量法。在同构并行矩量法负载均衡策略的基础上,提出了一种“MPI+openMP+DCU”的高效异构并行编程框架,解决了计算任务与计算能力不匹配的问题,实现了矩量法异构并行计算过程的负载均衡。采用细粒度任务划分策略与异步通信技术,对深度计算处理器计算过程进行了流水线优化设计,实现了计算与通信重叠,提升了矩量法异构协同计算的效率。通过与有限元法的仿真结果对比,验证了CPU+DCU异构并行矩量法的准确性。基于国产深度计算处理器异构平台的可扩展性分析结果表明,与单纯CPU计算相比,所实现的CPU+DCU异构协同计算方法能够获得5.5~7.0倍的加速效果,且在国家超级计算西安中心能够实现全系统运行,并行规模从360节点扩展到3 600节点(共1 036 800个处理器核心),并行效率可以达到约73.5%。

基于4-PSE并联机构的地质沉积模拟平台运动学分析

地质沉积模拟平台是定量研究地质沉积理论的重要装置。为满足沉积模拟大型化、精细化和定量化的研究需求,基于4-PSE并联机构设计一种可进行全方位调姿运动的地质沉积模拟平台,对其运动学特性进行研究。结合模拟平台的工作原理,对4-PSE并联机构的自由度进行计算,推导模拟平台的运动学方程。在ADAMS软件中建立模拟平台的虚拟样机模型,利用运动学仿真结果对其运动学参数进行理论验证。分析模拟平台的工作空间约束条件,求得其工作空间,绘制相关结构参数对工作空间的影响曲线。研究成果为后续地质沉积模拟平台的多块平台组合系统实验提供了理论基础。

Stewart平台神经网络非奇异终端滑模控制

针对Stewart平台的六自由度(six degrees of freedom,6-DOF)轨迹跟踪问题,提出一种基于神经网络的非奇异终端滑模控制方法并应用于Stewart平台的位置姿态控制中。通过分析Stewart平台的位置反解和速度反解,建立运动学方程,利用牛顿-欧拉方程建立动力学方程,并结合加速度反解得到了平台的状态空间表达式;基于非奇异滑模面函数,设计非奇异终端滑模控制律。考虑到径向基函数(radial Basis function,RBF)神经网络的逼近特性,采用RBF神经网络对模型未知部分进行自适应逼近,并利用Lyapunov第二法设计了自适应律;通过仿真证明控制器设计的有效性。仿真结果表明,相比于比例积分微分(proportional integral derivative,PID)控制器,提出的RBF神经网络非奇异终端滑模控制器具有更好的轨迹跟踪精度和动态特性。

机载光电平台主被动并联复合减振技术

针对制导跟踪系统中的机载光电平台在工作时受载机振动和气流扰动引起的宽频随机振动干扰,导致稳定精度下降、图像模糊、跟踪脱靶等问题,提出主被动并联复合减振控制技术。分别采用三环伺服控制和自抗扰位置控制策略,搭建基于音圈电机的单自由度机载光电平台主被动并联复合减振系统。仿真结果表明,主被动复合减振系统可有效降低振动信号对光电平台的影响,并且加入主动减振控制后的系统可以拓宽减振频宽,抑制低频振动信号且信号幅值可在被动减振基础上再次被有效衰减2个量级以上。

S-RPS-SPS并联机构稳定平台的运动学分析

舰船在海上会受到海浪、海风以及气流等环境影响,从而导致原本需要在稳定环境下工作的器材受到严重干扰,如起吊平台、雷达信号捕捉等。针对以上问题,提出了S-RPS-SPS并联机构稳定平台,该平台可以实现绕X轴横滚角的旋转以及绕Y轴俯仰角的旋转,从而间接消除船体在这两轴上的转动。在SolidWorks软件中建立该并联机构的模型并验证了自由度;选择位姿逆解的方法计算出两条驱动杆长度与动平台位姿角度之间的关系式,在该机构的动平台旋转角度和驱动杆伸缩长度范围内输入不同的角度,得到两组数据,对比了其误差;把计算公式、旋转角度范围以及坐标在Matlab软件中通过算法进行仿真,验证了动平台位姿的准确性。仿真结果表明,该机构在运动学方面的精度和可靠性都得到了很好的保证。

面向FT-M6678的对称矩阵特征值求解算法实现与优化

目前国产自主可控FT-M6678平台上没有对称矩阵特征值求解相关的实现,且平台上现有数学计算库不能很好地满足类似问题求解的需求。面向国产FT-M6678处理器,对对称矩阵特征值求解(SYEV)算法进行实现与优化,完善FT-M6678平台的线性代数计算库。通过对SYEV算法的实现过程以及运行热点的分析,基于FT-M6678平台进行编译优化、访存优化以及向量并行化优化,其中:编译优化是根据不同的编译选项指导编译器对程序优化以达到加速效果;访存优化包括缓存优化以及数据段与程序段的分配优化,用于提高矩阵数据的访存效率;向量并行化优化包括循环展开以及适配FT-M6678平台的单指令多数据流(SIMD)指令并行优化,用于提升程序的计算效率。在FT-M6678平台上对所实现并优化的算法进行正确性验证与优化性能分析,结果表明,算法能够正确通过LAPACK官方测试集测试,并且在FT-M6678平台上的加速效果可达到58.346倍,对比TMS320C6678平台速度可提升2.053倍。

基于BLF的三自由度并联稳定平台容错控制

针对具有不确定性和故障的三自由度并联稳定平台,提出一种基于障碍李雅普诺夫函数的反步容错控制方法。将模型不确定性、外部扰动和故障因素视为不确定性集合,通过固定时间扰动观测器对其进行实时估计,实现对控制器的补偿。通过引入障碍李雅普诺夫函数对系统状态进行约束,再结合反步法设计一种带有状态约束的容错控制器。通过稳定性理论证明该系统所有的闭环信号能够达到一致最终有界,仿真试验结果表明,该控制器能使平台在故障情况下保持稳定位姿,且能对不确定性集合进行快速、精确的估计以提升系统的稳定性。

基于Spark与优化分块的大幅面遥感影像SLIC分割方法

针对大幅面遥感影像在分块边界特征不连续和分割效率不高等问题,本文提出了结合Spark平台及最优紧密度评估的简单线性迭代聚类超像素分割算法(SLIC)。首先,使用结合最优紧密度的SLIC超像素分割方法完成图像分块,解决分块边界精度低的问题;然后,利用Spark对分块数据并行SLIC分割算法,提高运算效率;最后,将WorldView-2卫星影像和GF-2号影像作为试验数据,利用比值植被指数结合最大类间方差法改进SLIC算法以提高超像素分割精度。结果表明,改进SLIC方法在运算效率上比原方法提高了约9倍,边缘拟合精度提高了1.5%,欠分割误差提高了8.2%,边缘召回率提高了0.2%。