Robust Linear Interpolation and Extrapolation of Stationary Time Series in Lp

To deal with uncertainty of the spectral distribution, we consider minimax interpolation and extrapolation problems in L^p for stationary processes. The interpolation and extrapolation problems can be regarded as a linear approximation problem on the unit disk in the complex plane. Although the robust one-step-ahead predictor and interpolator has already been considered separately in the previous literature, we give two conditions for the uncertainty class to find the minimax interpolator and extrapolator in the general framework from both the point of view of the observation set and the point of view of evaluation on the interpolation and extrapolation error under the L^p-norm. We show that there exists a minimax interpolator and extrapolator for the class of spectral densities ε-contaminated by unknown spectral densities under our conditions. When the uncertainty class contains spectral distribution functions which are not absolutely continuous to the Lebesgue measure, we show that there exists an approximate interpolator and extrapolator in L^p such that its maximal interpolation and extrapolation error is arbitrarily close to the minimax error when the spectral distributions have densities. Our results are applicable to the stationary harmonizable stable processes.     

CNC加工中直线插补刀路的误差评估修正研究

在精加工中,CNC机床扮演者极其重要的角色.CNC机床的加工水平已经成为衡量一个国家生产力和工业实力的重要指标.本文将针对传统的CNC机床控制器的直线插补功能上的缺点作深入的研究与分析,并使用Runge-Kutta法则对样条刀路进行误差评估修正,利用对于误差的评估-修正的方法求出最佳的曲线参数,推导出机床各轴控制系统的相对取样时间的进给量.通过仿真试验证明本文提出的算法在轮廓加工精度上优于传统的直线插补方法.     

LOOK-AHEAD ALGORITHM FOR VELOCITY CONTROL BASED ON PARAMETERIZED CURVE INTERPOLATOR

To avoid suffering gouge and transient overshooting in high speed cutting machining, a novel parametefized curve interpolator model with velocity look-ahead algorithm is proposed. Based on a prearrangement step interpolation algorithm for parameterized curves and considering high curvature points, parameterized curve tool path is divided into acceleration segments and deceleration segments by look-ahead algorithm. Under condition of characteristics of acceleration and deceleration stored in control system, deceleration before high curvature points and acceleration after high curvature points are realized in real-time in high speed cutting machining. Based on new parameterized curve interpolator model with velocity look-ahead algorithm, a real cubic spline is machined simulativly. The simulation results show that velocity look-ahead algorithm improves velocity changing more smoothly.     

一种新的图像实时放大技术

该文提出了一种视频图像整数倍放大的实时插值方案一改进的像素填充插值法,给出了其基本原理及软、硬件实现方法.与重复插值法、线性插值法、像素填充插值法和小波放大法等进行了比较,并给出了放大后图像的主观和客观评价。结果表明改进的像素填充插值法的效果明显优于其他实时放大方法,且其硬件实现并不复杂,可用于视频图像实时放大的软、硬件设计。     

基于传动系统动力学的NURBS曲线插补算法

对机床传动系统、伺服驱动系统和数控插补模块进行动力学建模和求解。提出一种新的NURBS插补算法,按照进给率自适应轨迹规划算法进行当前插补周期的速度设定,并且根据曲线当前位置的曲率特性,进行基于曲率的最大速度限定,通过求解动力学模型,获得按照这一速度进行插补时系统需要的最大驱动力,若该驱动力超过系统能够提供的最大驱动力,则再次按照用户设定的加速度进行减速,获得的速度作为指令速度,按照一阶泰勒展开近似进行插补点的计算。该算法不仅在NURBS曲率较大的区域自动降低进给速度,保证要求的弦误差,而且使输出的插补速度指令区域平滑,保证不会出现插补输出的位置值系统无法进行位置控制造成更大的加工误差。     

A parametric interpolator with minimal feed fluctuation for CNC machine tools using arc-length compensation and feedback correction

Traditionally, approximation methods are utilized in the parametric interpolation because of the nonanalytic relationship between the spline parameter and the arc length. The approximation error has been considered as the source of the feedrate fluctuation. This paper shows that the discrepancy between the desired tool path and the target trajectory of the motion system is another primary source, and presents a feedback interpolator to eliminate the feedrate fluctuation. To evaluate the initial parameter value for the interpolator, an arc-length based Taylor's expansion with arc-length compensation is proposed, which alleviates greatly the feedrate command error caused by the trajectory deviation. Then, a feedback correction scheme is developed to further reduce the feedrate command error that results from the approximation error. Both computational load analysis and numerical simulations are conducted, and the results show that the present interpolator has very good performance in both efficiency and accuracy, thus is a good choice for high speed and high precision CNC machines.     

基于步进传动标记机系统的设计

论述了标记系统组成原理，简要地介绍了计算机与系统之间接口模块及步进电机驱动器的设计。最后，给出了本系统采用的逐点比较法直线插补器的实现方法。     

曲线的通用参数插补算法

一般的ＣＮＣ系统往往只提供直线和圆弧插补功能。尽管一些较新的系统也提供了二次曲线或某些样条曲线的插补程序，但仍然不能满足ＣＡＤ系统的曲线和曲面造型能力对ＣＡＭ系统的要求。本文研究了曲线的参数插补技术，提出了曲线的通用参数插补算法。     

一种3阶Mash结构的Σ-Δ音频数模转换器

针对传统的Mash结构由于各级失配导致信噪比低的问题,本文采用一阶相位累加器来实现传统的sigma-delta（Σ-Δ）架构,并将其采用硬件描述语言来实现,这样整个系统均在数字域实现,从根本上解决了各级间的失配问题.在插值滤波器的设计上,使用优化了的半带滤波器结构和级联积分梳状滤波器,节省了硬件资源.电路采用的是Magnachip 180nm 1P4M标准CMOS工艺,芯片面积只有0.2025mm²（0.45×0.45）,实测芯片得到的信噪失真比（SNDR）达到90dB.     

Development and implementation of a NURBS curve motion interpolator

This paper deals with the issues of development and implementation of a real-time NURBS interpolator for a six-axis robot. Using an open-architecture controller system as a testbed, a real-time NURBS curve interpolator was developed, implemented and tested. Sample runs were conducted with the resulting trajectories measured in real-time during robot motion. The resulting trajectories are analyzed, discussed and compared with those from a commonly used point-to-point approximation technique. The real-time NURBS curve interpolator's feasibility, advantages and related issues are also discussed.