Automatic modulation recognition of radiation source signals based on two-dimensional data matrix and improved residual neural network

Automatic modulation recognition(AMR)of radiation source signals is a research focus in the field of cognitive radio.However,the AMR of radiation source signals at low SNRs still faces a great challenge.Therefore,the AMR method of radiation source signals based on two-dimensional data matrix and improved residual neural network is proposed in this paper.First,the time series of the radiation source signals are reconstructed into two-dimensional data matrix,which greatly simplifies the signal preprocessing process.Second,the depthwise convolution and large-size convolutional kernels based residual neural network(DLRNet)is proposed to improve the feature extraction capability of the AMR model.Finally,the model performs feature extraction and classification on the two-dimensional data matrix to obtain the recognition vector that represents the signal modulation type.Theoretical analysis and simulation results show that the AMR method based on two-dimensional data matrix and improved residual network can significantly improve the accuracy of the AMR method.The recognition accuracy of the proposed method maintains a high level greater than 90% even at -14 dB SNR.

Single-cell manipulation by two-dimensional micropatterning

Cells are highly sensitive to their geometrical and mechanical microenvironment that directly regulate cell shape,cytoskeleton and organelle,as well as the nucleus morphology and genetic expression.The emerging two-dimensional micropatterning techniques offer powerful tools to construct controllable and well-organized microenvironment for single-cell level investigations with qualitative analysis,cellular standardization,and in vivo environment mimicking.Here,we provide an overview of the basic principle and characteristics of the two most widely-used micropatterning techniques,including photolithographic micropatterning and soft lithography micropatterning.Moreover,we summarize the application of micropatterning technique in controlling cytoskeleton,cell migration,nucleus and gene expression,as well as intercellular communication.

基于Distance-2算法的并行Jacobian矩阵计算及其在耦合问题中的应用

并行Newton-Krylov方法是求解大规模多物理耦合问题的有效方法,如何高效自动计算Jacobian矩阵是一大难点。利用有限差分方法,可避免推导Jacobian矩阵的表达式,实现矩阵的自动计算。现有工作表明,在串行环境下利用矩阵的稀疏性和图着色算法,Jacobian矩阵的计算效率可提高至少1个量级。但在并行环境下,串行着色算法失效,需采用相应的并行着色算法。本研究将图论领域的Distance-2算法应用于Jacobian矩阵的并行着色。通过求解一个简化多物理耦合问题检验了该并行算法的正确性和计算效率。测试结果表明,该并行算法得到的Jacobian矩阵完全正确;着色数随着并行核数的增加略微有所增加,100个进程下并行效率为56%;基于该算法求解多物理耦合问题,其计算时间和Krylov迭代次数较JFNK减少了约1/2。

Eigenfunction expansion method of upper triangular operator matrixand application to two-dimensional elasticity problems based onstress formulation

This paper studies the eigenfunction expansion method to solve the two dimensional （2D） elasticity problems based on the stress formulation. The fundamental system of partial differential equations of the 2D problems is rewritten as an upper tri angular differential system based on the known results, and then the associated upper triangular operator matrix matrix is obtained. By further research, the two simpler com plete orthogonal systems of eigenfunctions in some space are obtained, which belong to the two block operators arising in the operator matrix. Then, a more simple and conve nient general solution to the 2D problem is given by the eigenfunction expansion method. Furthermore, the boundary conditions for the 2D problem, which can be solved by this method, are indicated. Finally, the validity of the obtained results is verified by a specific example.

Stewart并联机构运动Jacobian矩阵表达形式的多样性

现有文献中Jacobian矩阵存在多种表达形式,不利于指标值的统一评估和对比。为此,通过剖析Stewart并联机构运动Jacobian矩阵的机理,找到引起上述现象的根本原因,用欧拉角及其导数描述动平台的转动速度并运用位置方程求导法推导出第1类形式的Jacobian矩阵;用角速度矢量描述动平台的转动速度,并运用环路方程法推导出第2类形式的Jacobian矩阵;将动平台上与静坐标系原点重合的点选为线速度基点,并运用环路方程法推导出第3类形式的Jacobian矩阵。运用角速度加法公式和线速度基点法,构建不同形式Jacobian矩阵之间的映射;运用矩阵理论推导各Jacobian矩阵行列式之间的关联。通过数值算例验证上述结论的正确性,并绘制机构的奇异曲面。所得结论为并联机构的型综合、型优化提供了理论指导。

Separation of Comprehensive Geometrical Errors of a 3-DOF Parallel Manipulator Based on Jacobian Matrix and Its Sensitivity Analysis with Monte-Carlo Method

Parallel kinematic machines （PKMs） have the advantages of a compact structure,high stiffness,a low moving inertia,and a high load/weight ratio.PKMs have been intensively studied since the 1980s,and are still attracting much attention.Compared with extensive researches focus on their type/dimensional synthesis,kinematic/dynamic analyses,the error modeling and separation issues in PKMs are not studied adequately,which is one of the most important obstacles in its commercial applications widely.Taking a 3-PRS parallel manipulator as an example,this paper presents a separation method of source errors for 3-DOF parallel manipulator into the compensable and non-compensable errors effectively.The kinematic analysis of 3-PRS parallel manipulator leads to its six-dimension Jacobian matrix,which can be mapped into the Jacobian matrix of actuations and constraints,and then the compensable and non-compensable errors can be separated accordingly.The compensable errors can be compensated by the kinematic calibration,while the non-compensable errors may be adjusted by the manufacturing and assembling process.Followed by the influence of the latter,i.e.,the non-compensable errors,on the pose error of the moving platform through the sensitivity analysis with the aid of the Monte-Carlo method,meanwhile,the configurations of the manipulator are sought as the pose errors of the moving platform approaching their maximum.The compensable and non-compensable errors in limited-DOF parallel manipulators can be separated effectively by means of the Jacobian matrix of actuations and constraints,providing designers with an informative guideline to taking proper measures for enhancing the pose accuracy via component tolerancing and/or kinematic calibration,which can lay the foundation for the error distinguishment and compensation.

Globally robust nonlinear PID controllers for robot manipulators with an uncertain Jacobian matrix

Based on a continuous piecewise-differentiable increasing functions vector, a class of robust nonlinear PID (RN-PID) controllers is proposed for setpoint control with uncertain Jacobian matrix. Globally asymptotic stability is guaranteed and only position and joint velocity measurements are required. And stability problem arising from integral action and integrator windup, are consequently resolved. Furthermore, RN-PID controllers can be of effective alternative for anti-integrator-wind-up, the control performance would not be very bad in the presence of rough parameter tuning.

Design of Discrete-time Repetitive Control System Based on Two-dimensional Model

This paper presents a novel design method for discrete-time repetitive control systems （RCS） based on two-dimensional （2D） discrete-time model. Firstly, the 2D model of an RCS is established by considering both the control action and the learning action in RCS. Then, through constructing a 2D state feedback controller, the design problem of the RCS is converted to the design problem of a 2D system. Then, using 2D system theory and linear matrix inequality （LMI） method, stability criterion is derived for the system without and with uncertainties, respectively. Parameters of the system can be determined by solving the LMI of the stability criterion. Finally, numerical simulations validate the effectiveness of the proposed method.

Study on singularity analysis with differential transform method for 3-RRUR parallel robot based on Jacobian matrix

Parallel robot is used in many different fields nowadays, but the singularity of 3-RRUR parallel robot is more complicated, so a method to analyze the singularity of the 3-RRUR parallel robot is very necessary. First, the Jacobian matrix was built based on the differential transform method through the transfer matrixes between the poles. The connection between the position parameters and singularity condition was built through the analysis of the Jacobian matrix. Second, the effect on the singularity from the position parameters was analyzed, and then the singularity condition was confirmed. The effect on the singularity condition from position parameters was displayed by the curved surface charts to provide a basic method for the designing of the parallel robot. With this method, the singularity condition could be got when the length of each link is firmed, so it can be judged that if a group of parameters are appropriate or not, and the method also provides warrant for workspace and path planning of the parallel robot.

Fast forward modeling of gravity anomalies for two-dimensional bodies of arbitrary shape and density distribution

A fast and high precision spatial domain algorithm is presented for forward modeling of two-dimensional(2D)body gravity anomalies of arbitrary shape and density distribution.The new algorithm takes advantage of the convolution properties of the expression for 2D gravity anomalies,uses a rectangular cell as a grid subdivision unit,and then 2D bodies with irregular cross-sections are approximated by a combination of 2D bodies with a rectangular cross section.The closed-form expression is used to calculate the gravitational anomalies of the combination of 2D bodies with a rectangular cross section.To improve computing effi ciency,the new algorithm uses a fast algorithm for the implementation of the Toeplitz matrix and vector multiplication.The synthetic 2D models with rectangular and circular cross-sections and constant and variable densities are designed to evaluate the computational accuracy and speed of the new algorithm.The experiment results show that the computation costs less than 6 s for a grid subdivision with 10000×10000 elements.Compared to the traditional forward modeling methods,the proposed method significantly improved computational effi ciency while guaranteeing computational accuracy.

Further studies on stability analysis of nonlinear Roesser-type two-dimensional systems

This paper is concerned with further relaxations of the stability analysis of nonlinear Roesser-type two-dimensional （2D） systems in the Takagi-Sugeno fuzzy form. To achieve the goal, a novel slack matrix variable technique, which is homogenous polynomially parameter-dependent on the normalized fuzzy weighting functions with arbitrary degree, is developed and the algebraic properties of the normalized fuzzy weighting functions are collected into a set of augmented matrices. Consequently, more information about the normalized fuzzy weighting functions is involved and the relaxation quality of the stability analysis is significantly improved. Moreover, the obtained result is formulated in the form of linear matrix inequalities, which can be easily solved via standard numerical software. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed result.

基于新一代几何技术规范的装配误差建模

针对由于公差设计不合理而导致的服役于复杂工况的机械装备性能下降等问题,提出一种综合考虑制造与装配误差的机械产品装配精度分析方法。该方法首先利用有限元分析机械装备零部件装配误差导致的变形,并提取发生形变的关键特征面;然后基于新一代几何技术规范(GPS)将特征面的变形转化为尺寸与形位公差数据,并与设计公差进行叠加,实现变形—误差—公差的转换;随后基于雅可比旋量理论,构建综合考虑制造与装配误差的公差分析模型支撑机械装备的公差精量化设计;最后以某型机载作动筒为工程应用对象,对比分析了是否考虑受力变形条件下装配精度分析的结果差异,结果显示该方法相较于原有方法具有更高的计算准确性,能为精密机械产品精度设计提供更加准确的指导。

自由度可调模块单元系统运动学并行建模

针对多个自由度可调模块单元组成的系统,提出含标准化流程的模块化机器人拓扑结构数学描述及运动学并行建模方法。首先,建立模块单元运动传递库,并提出含标准化流程的四元组矩阵模块化机器人拓扑结构数学描述。接着,以模块单元运动学模型为基础,考虑多分支模块化机器人各分支间耦合影响,建立适用于链式模块化机器人的位置级与速度级运动学模型。随后,提出模块化机器人运动学并行建模方法,理论分析和仿真结果均表明该算法能够适应各类型拓扑结构模块化机器人的快速建模。拓扑结构数学描述与并行计算的引入降低了模块化机器人建模难度,提升了建模效率。

可重构3-RPR平面并联机构的静刚度研究

以3-RPR平面并联机构为研究对象,通过设计一种在驱动、被动和锁定3种状态之间相互切换的移动副和转动副锁定装置,实现机构的重构。对重构前、后机构的静刚度特性进行理论建模和软件仿真。通过锁定任意两个运动副的方式,实现机构的拓扑重构。根据动平台的运动状态对锁定方式进行分类,并建立机构的反向运动学模型。对机构的雅克比进行推导,并基于虚功原理,推导静刚度矩阵。最后,对重构前、后的机构进行静力学虚拟实验,对比分析实验数据。结果表明:拓扑重构可以提升平面并联机构的静刚度性能。特别地,动平台做定轴转动时,其静刚度的提升效果尤其明显。这为少自由度可重构并联机构的性能评价和参数优化提供了理论依据。

2P6R拼装机械臂的运动学分析

目前隧道管片修复加固工作自动化程度低,存在施工安全隐患大、效率低、成本高、工人劳动强度大等问题.为实现隧道管片加固钢板的自动化拼装,首先,提出一种2P6R拼装机械臂方案,建立机械臂正运动学模型.其次,采用解析法对机械臂进行逆向运动学求解,以限制关节超限作为代价函数进行冗余解的选取,并在Beckhoff C6030-0080的TwinCAT 3平台进行逆运动学求解测试,验证算法具有较好的实时性.再次,利用微分变换法求得机械臂的雅可比矩阵,识别并列举边界奇异及内部奇异位形示例.最后,利用图解法绘制出机械臂可达工作空间截面及完整的三维可达工作空间,并进一步对机械臂进行灵活度分析,绘制出灵活度分布图.研究结果表明:2P6R拼装机械臂可以满足隧道管片加固钢板自动化拼装需求,为机械臂的应用提供理论基础.

基于Jacobian矩阵的6-6 Stewart平台结构校准

针对简化误差源模型 (含 42个误差量 ) ,建立了基于 Jacobian矩阵的 6 -6 Stewart平台误差模型 ,并依据该模型 ,提出了一种 6 -6 Stewart平台外部校准算法 ,仿真研究表明 ,该算法具有理论上的正确性和工程上的可行性。同时指出了该算法的关键是以系数矩阵

工业机器人奇异规避轨迹规划方法

针对激光追踪仪测量工业机器人定位误差测量中出现的六轴机器人运动学奇异问题,提出了奇异区域预测及实时优化的奇异规避轨迹规划方法。以国产配天AIR50-A机器人为研究对象,建立六自由度串联机器人运动学模型,解算机器人笛卡尔空间与关节空间映射关系。基于雅克比矩阵与奇异位形的关系模型,分析和预测机器人运动轨迹中存在的奇异区域。当机器人末端处于奇异区域或奇异预测域时,记录初始关节角序列作为奇异区域轨迹规划输入,利用五次多项式插值方法迭代更新奇异区域内的轨迹路径,机器人既定的运动路径与更新后的奇异规避路径结合形成机器人新的规划轨迹路径,保证机器人关节角运动学参数连续性的同时,规避奇异区域。实验结果表明,提出的奇异预测域及实时优化的奇异规避轨迹规划方法,能够抑制机械臂奇异区域附近关节角速度的激变,减少奇异位形对机器人运动性能的影响。

自动铺丝机器人Jacobian矩阵空间算子代数描述

应用空间算子代数理论,在mathmatica环境下对7自由度自动铺丝机器人的Jacobian矩阵进行了求解.通过对采用空间算子代数求解的自动铺丝机器人的Jacobian矩阵和采用微分法和矢量叉积方法得出的Jacobian矩阵进行对比,发现用空间算子代数理论求出的机器人的Jaco-bian矩阵形式简捷和具有明确的物理意义,并且对于任意结构形式的串联机器人的空间算子代数形式的Jacobian矩阵都具有解析的表达形式.研究表明采用空间算子代数求解串联机器人的Jacobian矩阵也是一种行之有效的方法.

Stewart型并联机器人的奇异对其运动精度的影响

以9-3 Stewart型并联机器人为研究对象,分析其在机构接近奇异位形时动平台运动精度的情况。通过计算并联机器人速度Jacobian矩阵的行列式得到奇异点的坐标。通过虚拟样机实验,得到动平台参考点位置反解和正解计算的相对误差。用转动Jacobian矩阵条件数的倒数来度量机构接近奇异的程度,并分析该程度与上述相对误差之间的映射关系。研究结果表明:当指标值大于7.027×10^(-5)时,正、反解的相对误差可忽略不计,这为奇异规避、路径规划等后续工作提供了理论参考。

Corrigendum to“Atomic-scale electromagnetic theory bridging optics in microscopic world and macroscopic world”

The signs of the electric field markers in Figs.2 and 4 of the paper[Chin.Phys.B 32104211(2023)]have been corrected.These modifications do not affect the results derived in the paper.