柔性支撑Stewart平台自适应交互PID隔振控制

为了实现500 m口径球面射电望远镜(five hundred meter aperture spherical radio telescope, FAST)二级精调稳定平台对馈源舱隔振控制的定位和指向精度, 首先提出了基于并联机构学原理的3维机动目标跟踪预测算法, 对柔性支撑Stewart平台的基座运动进行跟踪预测. 进而,在Stewart平台关节空间设计了自适应交互PID控制器, 引入自适应交互算法解决PID参数的实时调整, 以适应柔性支撑Stewart平台的参数变化对不同控制参数的需求. 采用现代机电系统仿真策略, 对柔性支撑Stewart平台隔振系统的动力学与控制问题进行了仿真, 结果表明: 与传统的PID控制器相比, 自适应交互PID控制器大大改善了隔振效果, 完全满足隔振目标的要求.     

巨型柔性Stewart平台解空间的研究

本文针对大型射电天文望远镜FAST中馈源系统的柔索结构及运动要求，提出了巨型柔 性Stewart平台的概念，并由馈源舱的非线性静平衡方程给出了解空间的定义．通过计算发 现六悬索巨型柔性Stewart平台的工作空间中存在六个解空间为零的面，不能保证馈源舱连 续平稳地做空间扫描．在综合考虑馈源舱运行规律及悬索受力特点的基础上，本文通过增加 两根向下拉的冗余悬索，设计了八悬索巨型柔性Stewart平台．计算结果表明八悬索巨型柔 性Stewart平台消除了解空间为零的位置，为大型射电天文望远镜FAST中采用八悬索而不是 六悬索巨型柔性Stewart平台提供理论基础和数值依据．     

基于Simulink的Stewart平台仿真研究

Stewart平台是一种6自由度的并联机器人机构，该文介绍了基于Simulink的SimMechanics模块集对Stewart平台进行仿真研究的方法，在具体分析SimMechanics模块集中各模块的使用及参数设置方法的基础上，运用该模块集对Stewart平台进行了建模。既便于使用SimMechanics模块集建立其他复杂机械系统的模型，又利于对Stewart平台进行深入研究。最后针对某Stewart平台的轨迹跟踪问题进行了仿真研究，获得了满意的结果。     

大射电望远镜精调Stewart平台非线性PID控制

为了实现大射电望远镜馈源指向跟踪系统精调Stewart平台的高精度轨迹跟踪,针对Stewart平台的系统特点,基于机器人关节控制策略,设计了一种非线性PID的Stewart关节调节器。该非线性PID算法构造了增益参数关于误差信号的非线性拟合函数,算法能够同时保证响应速度快、超调量小以及自适应能力强的系统特性。通过建立平台的数学模型,进行了典型信号输出响应数值仿真。仿真结果验证了关节空间控制策略以及非线性PID控制方法的可行性和有效性。     

6-6 SPS 6自由度Stewart并行机构位姿正解单解存

在获得了6-66自由度Stewart 并行机构位姿正解 的基础上,进一步提出了6-66自由度Stewart 并行机构位姿正解单解存在的条件．数字 模拟结果显示了该条件的适用性．     

节点坐标不确定的六自由度Stewart平台位置控制

针对Stewart平台铰节点坐标明显影响其动力规划的特点,基于节点坐标未知部分变化范围不大的具体情况,利用比例积分观测器(PIO)对动平台输出量进行有效的修正,并在此基础上得到了针对Stewart平台的多输入多输出高增益反馈控制器．数值结果说明了方法的有效性．     

带Stewart平台的航天器刚柔耦合动力学建模与仿真分析

本文采用柔性多体系统单向递推组集的建模方法,基于速度变分原理建立了带Stewart平台、柔性帆板和CMG组件的航天器刚柔耦合动力学模型.由于该模型自由度较大,无法满足实时控制的需求,因此建立了简化的Stewart平台等效模型,并通过与柔性Stewart平台完整模型对比,验证了所建立的动力学简化模型的正确性与高效性.分析了星体平台运动及柔性帆板的振动对有效载荷动力学响应的影响,指出了设计Stewart平台的微振动抑制方案时不能忽略下平台的运动及柔性附件的振动.本研究为带Stewart平台的航天器的微振动减振设计与高精度指向提供了有效的技术支撑.     

飞行模拟器经典洗出算法参数选择研究

为了保证Stewart平台能够在其工作空间内为飞行员提供逼真动感,对经典洗出算法的参数选择方法进行了研究.通过对二阶、三阶线性高通滤波器和二阶线性低通滤波器阶跃响应的分析,得出滤波器参数与阶跃响应之间的解析关系.并以此提出一种基于滤波器时域响应的滤波器参数选择方法,即对滤波器的各个参数在某一范围内进行定步长搜索,从而选择产生最优时域响应的滤波器参数.利用飞机起飞期间的飞行仿真数据和Stewart平台对其进行了实验验证,结果表明利用该方法选择的参数能充分利用Stewart平台的工作空间为飞行员提供逼真动感.     

基于Kane方法的Stewart传感器动力学及固有频率分析

通过线性化动力学方程并应用Kane方法,研究了Stewart传感器的固有频率．将Stewart传感器的上平台、上连杆、敏感元件及下连杆作为独立的子结构分别处理,依据矢量和张量理论对其运动学方程和动力学方程进行系统的推导,并经过简化导出Stewart传感器简洁的固有频率方程形式．为验证Kane方法的有效性,提供了MATHEMATICA数值算例．相比于传统的牛顿一欧拉方法及拉格朗日方法,Kane方法既简洁又高效,特别适合于计算机计算．     

控制FAST馈源的宏-微机器人系统

本文介绍了大射电望远镜FAST光机电一体化设计方案,给出了由贵州KARST地貌的地理位置 得到的线馈源扫描运动轨迹,对六悬索并联索系结构和Stewart平台组成的并联宏 微机器 人系统进行了运动学描述和分析．     

扫描探针显微镜的控制技术综述

扫描探针显微镜(SPM)具有高精度成像、纳米操纵等功能,是纳米科技、生命科学、材料科学和微电子等科学研究的重要工具.随着科学技术的发展,科学家和工程师们对科研工具SPM的性能也提出越来越高的要求.SPM控制技术作为提高SPM性能的关键技术之一,已经得到广泛的关注和研究.本文首先介绍SPM系统以及两种常用的SPM,讨论SPM扫描器(即压电驱动器)的特性及其数学模型;然后详细总结了SPM水平方向和竖直方向的控制技术,并且对扫描探针显微镜多输入多输出(SPM MIMO)控制技术进行了探讨;最后总结了SPM控制技术研究现状及其所面临的问题.     

The influence of river discharge and wind on Patos Lagoon,Brazil, Suspended Particulate Matter

Eight years (2008–2015) of reflectance data from the Moderate Resolution Imaging Spectroradiometer (MODIS) – Aqua sensor are used to quantify Suspended Particulate Matter (SPM) distribution and variability in Brazil’s Patos Lagoon. After application of an atmospheric correction suitable for extremely turbid coastal water and calculation of SPM concentrations from the reflectance values using an established algorithm, the daily remote sensing data were averaged into eight-day and monthly composites. The climatological patterns show a gradient from higher concentrations in the north to lower concentration in the south, with highest concentrations in austral spring and summer and lowest in autumn and winter. Strong interannual variability shows 2009 and 2012 to have the highest SPM concentrations and 2010 and 2014 to have the lowest. Time series of SPM were then compared with the main forces to the lagoon circulation (wind and river discharge). Peaks in SPM are associated with peaks in river discharge. Maximum SPM occurred following peaks in river discharge combined with strong northeast (NE) winds, suggesting that freshwater input and direction-specific winds are the major mechanisms of sediment transport in Patos Lagoon.     

Compiler‐assisted dynamic scratch‐pad memory management with space overlapping for embedded systems

Scratch‐pad memory (SPM), a small, fast, software‐managed on‐chip SRAM (Static Random Access Memory) is widely used in embedded systems. With the ever‐widening performance gap between processors and main memory, it is very important to reduce the serious off‐chip memory access overheads caused by transferring data between SPM and off‐chip memory. In this paper, we propose a novel compiler‐assisted technique, ISOS (Iteration‐access‐pattern‐based Space Overlapping SPM management), for dynamic SPM management with DMA (Direct Memory Access). In ISOS, we combine both SPM and DMA for performance optimization by exploiting the chance to overlap SPM space so as to further utilize the limited SPM space and reduce the number of DMA operations. We implement our technique based on IMPACT and conduct experiments using a set of benchmarks from DSPstone and Mediabench on the cycle‐accurate VLIW simulator of Trimaran. The experimental results show that our technique achieves run‐time performance improvement compared with the previous work. The average improvements are 13.15, 19.05, and 25.52% when the SPM sizes are 1KB, 512 bytes, and 256 bytes, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Spectral–spatial based sub-pixel mapping of remotely sensed imagery with multi-scale spatial dependence

Sub-pixel mapping (SPM) is a technique used to obtain a land-cover map with a finer spatial resolution than input remotely sensed imagery. Spectral–spatial based SPM can directly apply original remote-sensing images as input to produce fine-resolution land-cover maps. However, the existing spectral–spatial based SPM algorithms only use the maximal spatial dependence principle (calculated at the sub-pixel scale) as the spatial term to describe the local spatial distribution of different land-cover features, which always results in an over-smoothed and discontinuous land-cover map. The spatial dependence can also be calculated at the coarse-pixel scale to maintain the holistic land-cover pattern information of the resultant fine-resolution land-cover map. In this article, a novel spectral–spatial based SPM algorithm with multi-scale spatial dependence is proposed to overcome the limitation in the existing spectral–spatial based SPM algorithms. The objective function of the proposed SPM algorithm is composed of three parts, namely spectral term, sub-pixel scale based spatial term, and coarse-pixel scale based spatial term. Synthetic multi-spectral, degraded Landsat multi-spectral and real IKONOS multi-spectral images are employed in the experiments to validate the performance of the proposed SPM algorithm. The proposed algorithm is evaluated visually and quantitatively by comparing with the hard-classification method and two traditional SRM algorithms including pixel-swapping (PS) and Markov-random-field (MRF) based SPM. The results indicate that the proposed algorithm can generate fine-resolution land-cover maps with higher accuracies and more detailed spatial information than other algorithms.     

Singular perturbation margin and generalised gain margin for nonlinear time-invariant systems

In this paper, singular perturbation margin (SPM) and generalised gain margin (GGM) are proposed as the classical phase margin and gain margin like stability metrics for nonlinear systems established from the view of the singular perturbation and the regular perturbation, respectively. The problem of SPM and GGM assessment of a nonlinear nominal system is formulated. The SPM and GGM formulations are provided as the functions of radius of attraction (ROA), which is introduced as a conservative measure of the domain of attraction (DOA). Furthermore, the ROA constrained SPM and GGM analysis are processed through two stages: (1) the SPM and GGM assessment for nonlinear systems at the equilibrium point, based on the SPM and GGM equilibrium theorems, including time-invariant and time-varying cases (Theorem 5.3, Theorem 5.2, Theorem 5.4 and Theorem 5.5); (2) the establishment of the relationship between the SPM or GGM and the ROA for nonlinear time-invariant systems through the construction of the Lyapunov function for the singularly perturbed model (Theorem 6.1 and Section 6.2.3).     

Technical feasibility analysis of utilizing special purpose machine tools

Special purpose machine tools (SPMs) are primarily used for performing drilling-related operations and are widely used in mass production including automotive component manufacturing. Utilization of SPM is considerably widespread; however, this technology is relatively new and expensive. The important problems facing manufacturing industries wishing to utilize this technology is feasibility analysis to decide whether a SPM can be utilised for production of the given part and if it is feasible which SPM components would be appropriate. Since the cost of utilizing SPM is high, feasibility analysis must be performed before any investment on detailed design. This paper proposes a technical feasibility analysis method which assists in deciding whether SPM is applicable for machining a given part to achieve the highest productivity. The method is based on the framework which consists of relations between the desired part properties to the characteristics of the SPM components. These relations are captured as rules and constraints in an intelligent system which is implemented in Visual Basic. Applying the proposed method to a number of industrial parts shows that it is a very useful tool in deciding when SPMs should be utilized.     

A successive projection method for binary pattern recognition with multilayer feedforward neural networks

Error back-propagation (BP) is one of the most popular ideas used in learning algorithms for multilayer neural networks. In BP algorithms, there are two types of learning schemes, online learning and batch learning. The online BP has been applied to various problems in practice, because of its simplicity of implementation. However, efficient implementation of the online BP usually requires an ad hoc rule for determining the learning rate of the algorithm. In this paper, we propose a new learning algorithm called SPM, which is derived from the successive projection method for solving a system of nonlinear inequalities. Although SPM can be regarded as a modification of online BP, the former algorithm determines the learning rate (step-size) adoptively based on the output for each input pattern. SPM may also be considered a modification of the globally guided back-propagation (GGBP) proposed by Tang and Koehler. Although no theoretical proof of the convergence for SPM is given, some simulation results on pattern classification problems indicate that SPM is more effective and robust than the standard online BP and GGBP     

一种快速冗余容错编码方法及其在IP网络QoS控制中的应用

首先提出一种快速容错编码方法:混洗素矩阵 (ShuffledPrimeMatrix,SPM)码。SPM是对目前广泛应用于非实时环境 (例如RAID磁盘阵列 )中的Reed Solomon冗余容错码的变例。相对于后者,SPM码具有时间效率高、节省内存资源和程序实现简便等优势,因而更适合于实时环境或嵌入式应用的需求。给出了基于SPM码的IP网络端到端的QoS控制方案,并分析了其有益效果。     

Automatic and personalized recommendation of TV program contents using sequential pattern mining for smart TV user interaction

Due to the excessive number of TV program contents available at user’s side, efficient access to the preferred TV program content becomes a critical issue for smart TV user interaction. In this paper, we propose an automatic recommendation scheme of TV program contents in sequence using sequential pattern mining (SPM). Motivation of sequential TV program recommendation is based on TV viewer’s behaviors for watching multiple TV program contents in a row. A sequence of TV program contents for recommendation to a target user is constructed based on the features such as an occurrence and net occurrence of frequently watched TV program contents from the similar user group to which the target user belongs. Three types of SPM methods are presented—offline, online and hybrid SPM. To extract sequential patterns of preferably watched TV program contents, we propose a preference weighted normalized modified retrieval rank (PW-NMRR) metric for similar user clustering. In the offline SPM method, we effectively construct the sequential patterns for recommendation using a projection method, which yields good performance for relatively longer sequential patterns. The online SPM method mines sequential patterns online by effectively reflecting the recent preference characteristics of users for TV program contents, which is effective for short-sequence recommendation. The hybrid SPM method combines the offline and online SPM methods. The maximum precisions of 0.877, 0.793 and 0.619 for length-1, -2 and -3 sequence recommendations are obtained from the online, hybrid and offline SPM methods, respectively.     

Satellite multi-sensor mapping of suspended particulate matter in turbid estuarine and coastal ocean,China

In this work, five ocean-colour sensors, the Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite (Terra MODIS), Moderate Resolution Imaging Spectroradiometer aboard the Aqua satellite (Aqua MODIS), Medium Range Imaging Spectrometer aboard the Environmental Satellite (Envisat MERIS), Medium Resolution Spectral Imager aboard the FY-3 satellite (FY-3 MERSI), and Geostationary Ocean Colour Imager (GOCI), were selected to examine the compatibility of an algorithm proposed for suspended particulate matter (SPM) retrieval and concordance of satellite products retrieved from different ocean-colour sensors. The results could effectively increase revisit frequency and complement a temporal gap of time series satellites that may exist between on-orbit and off-orbit. Using in situ measurements from 17 cruise campaigns between 2004 and 2012, the SPM retrieval algorithm was recalibrated so as to be universal and adapted for multi-sensor retrievals. An inter-comparison of multi-sensor-derived products showed that GOCI-derived SPM and Envisat MERIS-derived SPM had the best fitting on a 1:1 scatterplot, with a statistic regression slope of 0.9617 and an intercept of 0.0041 (in units of g l^–1), respectively. SPM products derived from three sensors with nearly synchronous transit, Envisat MERIS, Terra MODIS, and FY-3 MERSI, exhibited excellent accordance with mean differences of 0.056, 0.057, and 0.013 g l^–1 in three field fixed stations, respectively, in the Yangtze estuary. Terra MODIS-derived SPM with GOCI-derived SPM, except in the high SPM waters of Hangzhou Bay, and Aqua MODIS-derived SPM with GOCI-derived SPM, except in the moderate SPM waters of the South Branch and south of the Subei Coast, showed a good correspondence. Meanwhile, synchronous multi-sensor-derived SPM with concurrent in situ SPM time series observed in fixed field stations mostly displayed a good correspondence. Results suggest that the algorithm is feasible and compatible for SPM retrieval by multiple sensors.