Isotropic Energies, Filters and Splines for Vector Field Regularization

The aim of this paper is to propose new regularization and filtering techniques for dense and sparse vector fields, and to focus on their application to non-rigid registration. Indeed, most of the regularization energies used in non-rigid registration operate independently on each coordinate of the transformation. The only common exception is the linear elastic energy, which enables cross-effects between coordinates. Cross-effects are yet essential to give realistic deformations in the uniform parts of the image, where displacements are interpolated.In this paper, we propose to find isotropic quadratic differential forms operating on a vector field, using a known theorem on isotropic tensors, and we give results for differentials of order 1 and 2. The quadratic approximation induced by these energies yields a new class of vectorial filters, applied numerically in the Fourier domain. We also propose a class of separable isotropic filters generalizing Gaussian filtering to vector fields, which enables fast smoothing in the spatial domain. Then we deduce splines in the context of interpolation or approximation of sparse displacements. These splines generalize scalar Laplacian splines, such as thin-plate splines, to vector interpolation. Finally, we propose to solve the problem of approximating a dense and a sparse displacement field at the same time. This last formulation enables us to introduce sparse geometrical constraints in intensity based non-rigid registration algorithms, illustrated here on intersubject brain registration.     

Distributed Cooperative Outdoor Multirobot Localization and Mapping

The subject of this article is a scheme for distributed outdoor localization of a team of robots and the use of the robot team for outdoor terrain mapping. Localization is accomplished via Extended Kalman Filtering (EKF). In the distributed EKF-based scheme for localization, heterogeneity of the available sensors is exploited in the absence or degradation of absolute sensors aboard the team members. The terrain mapping technique then utilizes localization information to facilitate the fusion of vision-based range information of environmental features with changes in elevation profile across the terrain. The result is a terrain matrix from which a metric map is then generated. The proposed algorithms are implemented using field data obtained from a team of robots traversing an uneven outdoor terrain.     

Adaptive generic model control for a class of nonlinear time-varying processes with input time delay

In this article, an adaptive control approach––Adaptive Generic Model Control (AGMC) for a class of nonlinear time-varying processes with input time delay is proposed. First, a nonlinear state predictor (NSP) is introduced, which extends the conventional generic model control (GMC) to a class of nonlinear processes with input time delay. Then a class of nonlinear time-varying processes with input time delay is further considered. A modified strong tracking filter (MSTF) is adopted to estimate the time-varying parameters of the nonlinear processes, and the state estimates are then utilized to update the plant models used in the NSP and MSTF, this results in an adaptive generic model control scheme for a class of nonlinear time-varying processes with input time delay. A modified mathematical model of a three-tank-system is used for computer simulations, the results show that the proposed AGMC algorithm is satisfactory, and it has definite robustness against model/plant mismatch in the measurement noise.     

多功能动平衡测量仪

多功能动平衡测量仪是以MCS - 96系列 80 98单片机为核心的一种基于微电子技术的数字化功能动平衡测量仪。该仪器采用 16位单片机、点阵式液晶显示屏、硬件滤波和软件滤波相结合的方法 ,使其具有操作简单、显示直观、精度高以及性能好的特点。本文给出了该系统的框图 ,同时从软件和硬件的角度介绍了该仪器的基本工作原理和工作流程。     

超声波电机速度特性测试技术研究

电机性能测试的离散数据中包含各种扰，必须对测试数据进行数字处理。文中用计算编程采集光电编码器脉冲值，并采用曲线拟合、数字滤波的方法对所测信号进行处理，得出电机运行特性曲线，为进一步改进超声波电机运行特性和提高控制的性能奠定基础。     

基于遗传算法无源电力滤波器的优化设计

针对现有无源电力滤波器的设计方法中过分依赖经验和优化能力不强的情况 ,提出了一种基于遗传算法的无源电力滤波器设计方法。从无源滤波器成本、无功补偿和滤波效果三个目标进行全局优化。通过改变遗传交叉和变异概率来改善早熟收敛的情况。同时开发出界面友好 ,多种参数自选的自动设计软件 ;实际仿真和实验结果表明 ,所提出的设计方法正确有效 ,所开发的软件实用性强     

Oscillation and convergence behaviours exhibited in an ‘unstable’ second‐order digital filter with saturation‐type non‐linearity

This letter explains the oscillatory behaviours exhibited in a second‐order digital filter with saturation‐type non‐linearity via the Hopf bifurcation theorem. It is shown that depending on the bifurcation parameter, the state variables may converge to zero even when the eigenvalues of the system matrix are outside the unit circle. Copyright © 2004 John Wiley & Sons, Ltd. abstract     

Structure generation and performance comparison of elliptic Gm‐C filters

Starting from a set of matrices describing a general G_m‐C filter topology, a procedure is developed for generating structures of lowpass filters. As the matrices and the filter topologies have a one‐to‐one correspondence, an algebraic method is used to identify filter topologies with desired properties, here, transfer functions with finite jω‐axis transmission zeros, specifically elliptic filters. Sensitivity expressions for these structures are derived and a performance comparison based on a set of chosen criteria is made. For a specified elliptic transfer function, filters with only grounded capacitors and those containing also floating capacitors emerge as alternative realizations, as are filters with a single input and those with distributed inputs. For third‐order functions, a detailed comparison is performed of leapfrog (LF) and inverse follow‐the‐leader‐feedback (IFLF), the most popular special cases, and of topologies that have also floating capacitors (LF_f, IFLF_f), as well as of a novel configuration that uses also distributed inputs (DI_f) and leads to a reduced element count. Design guidelines and restrictions are given, which follow from the derived results with focus on the circuits' sensitivity performance and other properties important for IC implementation. Copyright © 2004 John Wiley & Sons, Ltd.     

一种新的中压电机调速法--转子变频调速

介绍一种用中功率IGBT低压变频器调节大功率风机和泵用中压电机转速的方法——转子变频调速。采用该调速法的变频器主电路简单、无电抗器、运行功率因数高、谐波小、起动和旁路容易。     

三相并联有源滤波器输出滤波器设计方法研究

对三相并联有源滤波器的输出LRC低通滤波器进行了研究。根据瞬态电流跟踪指标要求,推导出并联APF输出电感的估算公式。在此基础上,详细介绍了LRC低通滤波器参数的设计方法。通过对整流负载补偿特性的仿真和实验分析,验证了该设计方法的可行性。采用该方法设计的输出滤波器,其补偿特性良好,补偿后的总谐波畸变率低,高频分量能够有效地被滤除。