测量设备轴角编码器误差修正研究

针对现有测量设备轴角编码器误差修正方法的局限性,在介绍轴角编码器误差检测方法的基础上,给出了多个误差检测实例,对误差进行了分析,并根据不同的误差规律提出了不同的修正模型。结果表明,轴角编码器虽具有相同的工作原理,但误差规律不尽相同,在一定角度范围内对测量设备测角精度的影响可远超编码器本身的精度指标,应根据实际检测结果采用不同的修正方法和模型予以修正。     

一种PL/SQL程序包失效的解决方案

针对pl/sql程序包在运行中有时会出现＂程序包失效＂的异常情况,通过深入分析该错误与对象依赖机制、自动重编机制和程序包运行机制的关系,结合3个不同的实验,证实了该错误与程序包中全局变量/常量的独有特性有关,并提供了一种解决方案：对新开发程序包,应尽量避免使用全局变量,使用函数来代替全局常量;对现有程序包,在逐步实施代码改造同时,应密切监控错误的发生、定期检测失效的程序包并自动进行重新编译处理。     

Intersymbol interference reduction for differential MSK bynonredundant error correction

A theoretical analysis and experimental results for differential detection of minimum-shift keying (MSK) with nonredundant error correction are described. The proposed demodulator utilizes the output detected from the difference in phase over two or three time slot intervals along with the conventional detector output. A single error can be corrected by using two differential detectors, and a single and a double error can be corrected by using three detectors. It is shown that the error rate performance is improved, especially in the presence of intersymbol interference (ISI), without the addition to the transmitted data of redundant bits. Simulation and experimental results agree with the theoretical analysis, which shows that the degradation of differential detection relative to coherent detection is reduced from 2.2 dB without error correction to 1.2 dB with single error correction and to 0.7 dB with double error correction. The method can be applied effectively to mobile communications over a fading channel or to time-division multiple-access (TDMA) communications using burst mode transmission     

Delay detection method using cross-spectrum for multitransmitter simulcasting

The authors propose a precise delay detection method using cross-spectrum which can be adopted for phase synchronisation of high speed multitransmitter simulcasting mobile radio communication systems. It is also shown that the detection error of this method is improved by pseudorandom noise (PN) signals and the minimum square error estimation.<>     

基于DSP的光电编码器自动检测系统

传统的光电编码器的精度检测利用平行光管和多面体,其缺点是检测时间长,需要有经验的师傅;编码器误码检测则通过旋转编码器,使二进制灯排逐次进位,同样监测效率低,且容易错判。文中设计了一套光电编码器自动检测系统,基准编码器、电机和被检编码器同轴连接,其中24位基准编码器作为精度检测基准和位置反馈元件构成闭环系统,以DSP为核心的控制器控制自动检测系统工作在两种模式下,精度检测工作在位置模式下,错码检测工作在速度模式下,可以检测精度的同时对错码进行判别。采用该系统对两台14位编码器进行检测,实验结果表明精度检测数据与采用平行光管精度检测数据一致。该系统可提高检测效率,缩短编码器设计周期,可以推广到其他型号编码器调试与检测中。     

On error exponents in hypothesis testing

The classical result of Blahut, which characterizes achievable error exponents in binary hypothesis testing, is generalized in two different directions. First, in M-ary hypothesis testing, the tradeoff of all M(M-1) types of error exponents and corresponding optimal decision schemes are explored. Then, motivated by a power-constrained distributed detection scenario, binary hypothesis testing is revisited, and the tradeoff of power consumption versus error exponents is fully characterized. In the latter scenario, sensors are allowed to make random decisions as to whether they should remain silent and save power, or transmit and improve detection quality. It is then shown by an example that optimal sensor decisions may indeed be random     

Arithmetic coding-based continuous error detection for efficientARQ-based image transmission

Block cyclic redundancy check (CRC) codes are typically used to perform error detection in automatic repeat request (ARQ) protocols for data communications. Although efficient, CRCs can detect errors only after an entire block of data has been received and processed. We propose a new “continuous” error detection scheme using arithmetic coding that provides a novel tradeoff between the amount of added redundancy and the amount of time needed to detect an error once it occurs. This method of error detection, first introduced by Bell, Witten, and Cleary (1990), is achieved through the use of an arithmetic codec, and has the attractive feature that it can be combined physically with arithmetic source coding, which is widely used in state of-the-art image coders. We analytically optimize the tradeoff between added redundancy and error-detection time, achieving significant gains in bit rate throughput over conventional ARQ schemes for binary symmetric channel models for all probabilities of error     

New error recovery strategy for 64 kbit/s video codecs

A new error recovery strategy for 64 kbit/s video codecs is described. Unlike existing strategies of error recovery in which a new frame is transmitted on the detection of a channel error, the new strategy uses previous frames which are known to be correct. Computer simulations of the technique are performed and subjective and quantitative results are obtained     

光电经纬仪靶场精度检测数据误差分析

本文介绍了光电经纬仪靶场精度检测的试验方法及误差分析。靶场精度检测易受气候条件影响造成事后精度超差,无法反映设备的真实状况,文章提出了精度检测过程中的误差计算方法,并对事后误差数据中跟踪部位及脱靶量误差进行数据修正。实战任务表明,误差修正方法对校飞数据事后处理精度的提高具有很好的效果,事后经纬仪系统总误差精度由原来的60″提高到18″。     

Optimal detection of digital data over the nonselective Rayleighfading channel with diversity reception

Based on the criterion of minimum symbol error probability, an analysis is made of symbol-by-symbol detection of a sequence of digital data transmitted using linear suppressed-carrier modulation over L independent diversity channels with AWGN (additive white Gaussian noise) and slow nonselective Rayleigh fading. The optimal receiver is derived, but is found to be difficult to implement in practice because of its exponential growth in complexity as a function of sequence length. Suboptimal decision-feedback approximations are then suggested which are linear and readily implementable and can be integrated as generalized differentially coherent receivers. The exact bit error probabilities of these suboptimal receivers are obtained. Tight upper bounds on these error probabilities are also obtained which show simply how they behave as a function of signal-to-noise ratio and order of diversity. A main conclusion of this work is that optimal data detection on a fading channel should be performed using MMSE (minimum mean squared error) estimates of the quadrature amplitudes of the channel fading processes as a coherent reference     

On the effectiveness of residue code checking for parallel two'scomplement multipliers

The effectiveness of residue code checking for online error detection in parallel two's complement multipliers has only up until now been evaluated experimentally for few architectures. In this paper a formal analysis is given for most of the current multiplication schemes. Based on this analysis it is shown which check bases are appropriate, and how the original scheme has to be extended for complete error detection at the input registers and Booth recoding circuitry. In addition, we argue that the hardware overhead for checking can be reduced by approximately one half if a small latency in error detection is acceptable. Schemes for structuring the checking logic in order to guarantee it to be self-testing, and thus achieve the totally self-checking goal for the overall circuit, are also derived     

改进滤波法在热管换热系统稳态检测中的应用

热管换热系统在进行数据调和和稳态优化之前，必须保证系统处于稳定状态，而检测系统是否处于稳定状态的方法多种多样。改进滤波法是一种较为普遍的稳态检验方法，可以对包含过失误差的系统数据进行有效检测，从而判断系统是否处于稳态。热管换热系统由于电网电压的波动以及外界振动，易给传感器测温数据引入过失误差，运用改进滤波法可有效检测数据含过失误差的情况。数值试验结果表明，传统的滤波法用于检测数据含过失误差时稳态检测失效，而改进滤波法能有效检测出系统处于何种状态。     

大口径波片空间相位延迟量误差研究

波片相位延迟量的常用检测方法只是针对激光光束直径(2 mm左右)的光束测出的平均值,对于大口径波片空间相位延迟量的检测,本文提出基于菲索干涉仪的检测方法,建立了波片的空间相位延迟量误差与干涉图样之间的理论数学模型,理论分析了影响相位延迟量误差主要因素有:光源的光谱宽度、石英晶体的空间折射率分布以及波片的面形误差；利用MATLAB程序编程,进行了数值计算,若要求波片的相位延迟量总误差小于一般波片测试误差1°,则光源的光谱宽度应小于0.2 nm,石英晶体的空间折射率分布误差应小于0.005,面形误差应小于200 nm；实验室搭建菲索干涉仪,选取了口径25.4 mm的石英波片进行测试,测试效果良好,测量精度为0.05°。     

Continuous error detection (CED) for reliable communication

Block cyclic redundancy check (CRC) codes represent a popular and powerful class of error detection techniques used almost exclusively in modern data communication systems. Though efficient, CRCs can detect errors only after an entire block of data has been received and processed. In this work, we exploit the “continuous” nature of error detection that results from using arithmetic codes for error detection, which provides a novel tradeoff between the amount of added redundancy and the amount of time needed to detect an error once it occurs. We demonstrate how this continuous error detection framework improves the overall performance of communication systems, and show how considerable performance gains can be attained. We focus on several important scenarios: 1) automatic repeat request (ARQ) based transmission; 2) forward error correction (FEC frameworks based on (serially) concatenated coding systems involving an inner error-correction code and an outer error-detection code; and 3) reduced state sequence estimation (RSSE) for channels with memory. We demonstrate that the proposed CED framework improves the throughput of ARQ systems by up to 15% and reduces the computational/storage complexity of FEC and RSSE by a factor of two in the comparisons that we make against state-of-the-art systems     

Development of comprehensive accuracy assessment indexes for building footprint extraction

Presents a suite of indexes for comprehensively evaluating the results of automated building extraction. The indexes described include detection rate, correctness, matched overlay, area omission error, area commission error, root mean square error, corner difference, area difference, perimeter difference, and shape similarity. These proposed unbiased quality measures should enable the accuracy assessment of the building extraction process to address extraction issues such as completeness, geometric accuracy, and building shape similarity.     

点源目标质心探测中单个盲元线性插值补偿算法选取

自适应光学系统中应用哈特曼波前传感器对点源目标进行质心探测时,光电探测器上子孔径区域内存在的盲元会引入一定的附加质心探测误差,为了减小质心误差,需要选取合适的盲元补偿算法获得相对合理的补偿值。推导了哈特曼波前传感器子孔径内单个盲元补偿后造成的附加质心探测误差。利用仿真统计了各种利用盲元邻域正常像素进行线性插值的单个盲元补偿算法对点源目标质心探测误差的影响。提出了单个盲元邻域像素线性插值补偿算法选取的若干准则,指出选用盲元上下左右4邻域像素的均值进行补偿造成的平均质心误差最小,而选用盲元左右两个像素平均补偿算法可以在补偿误差较小的情况下简化运算。实验结果与仿真结果相符合。     

空间光通信中的分布式检测算法

分布式多输入多输出(MIMO)技术是抑制空间光通信中大气湍流效应和降低误包率的有效手段之一。文章首先介绍MIMO光通信系统的信道模型,采用Kalman滤波器对接收信号均值和方差进行自适应估计和预测。然后提出了空间光通信中分布式检测算法,并推导了全局误码率的迭代公式。仿真结果表明:与等增益似然检测算法相比,分布式检测算法在低信噪比时,有较优的误码性能,抗干扰性能强。随信噪比的增加,分布式检测算法的误码率达到一个稳态值。     

Bounds on performance for the noisy reference PSK channel

A lower bound is derived for the uncoded error probability of coherent digital phase-shift-keying without making any assumptions on phase-locked loop speed. An improved upper bound on bit error probability is also derived. The results are applicable to both lightwave homodyne detection, in which the laser's phase noise must be taken into account, and to general partially coherent detection of (binary phase-shift-keying) over the additive white Gaussian noise channel when a noisy phase reference is derived. Bit-error-rate and cut-off bounds are presented     

Design of parallel fault-secure encoders for systematic cyclic block transmission codes

In this paper, we consider the problem of designing parallel fault-secure encoders for various systematic cyclic linear codes used in data transmission. It is assumed that the data to be encoded before transmission are stored in a fault-tolerant RAM memory system protected against errors using a cyclic linear error detecting and/or correcting code. The main idea relies on taking advantage of the RAM check bits to control the correct operation of the cyclic code encoder as well. A slightly modified encoder allows not only for encoding the transmission data stream but also, independently and in parallel, to generate the reference check bits which allow for concurrent error detection in the encoder itself. The error detection capacity proves to be effective and grants good levels of protection as shown by error injection campaigns on encoders for various standard linear cyclic error detecting and error correcting codes. Moreover, the complexity evaluation of the FPGA implementations of the encoders shows that their fault-secure versions compare favorably against the unprotected ones, both with respect to hardware complexity and the maximal frequency of operation.     

Phase-locked loop with dual phase frequency detectors for high-frequency operation and fast acquisition

The sequential phase frequency detector (PFD) has an unlimited error detection range and the precharge PFD has one and a half times better resolution performance than the sequential PFD. Therefore, by selective operation of the appropriate PFD connected to the well-adjusted charge pump, an unlimited error detection range, a high-frequency operation, and a higher speed lock-up time can be achieved. In this paper, we propose a phase-locked loop (PLL) with dual PFDs in which advantages of both PFDs can be combined. This structure can improve the tradeoff between acquisition behavior and locked behavior.