捷联惯性导航系统中陀螺仪温度补偿技术的应用

大量的实验研究已证明温度的变化是影响陀螺仪误差主要因素之一。为了抑制陀螺仪温度变化带来的误差影响,本文首先根据实验数据辨识出器件的温度模型,然后推导出相应的补偿模型进行温度补偿,并采用Kalman滤波技术降低温度测量的噪声,从而提高陀螺仪稳定性。     

Neuro sliding mode control of robotic manipulators

In this paper, a synergistic combination of neural networks with sliding mode control (SMC) methodology is proposed. As a result, the chattering is eliminated and error performance of SMC is improved. In the approach, two parallel Neural Networks (NNs) are utilized to realize a neuro-SMC. The equivalent control and the corrective control terms of SMC are the outputs of the NNs. The weight adaptations of NNs are based on the SMC equations in such a way that the use of the gradient descent method minimizes the control activity and the amount of chattering while optimizing the error performance. The approach is almost model-free, requiring a minimal amount of a priori knowledge and robust in the face of parameter changes. Experimental studies carried out on a direct drive arm are presented, indicating that the proposed approach is a good candidate for trajectory control applications.     

Error Margin Estimating in Repeaters

In this paper a new method of estimating error margin inTcarrier repeaters is proposed. This estimate is based on two sets of data: (a) measurements from a commonly used test wherein bipolar violations are inserted into the line at an audio rate, and (b) the crosstalk environment in which the repeater is operating. An audio component due to violations in the bipolar signal causes a shift in the eye pattern resulting in a change of repeater error rate. This in turn changes the regenerated audio signal power by an amount depending on the initial undisturbed error rate of the repeater. This then gives a basis for extrapolating the operating error rate of a repeater from a test measurement. This error rate combined with a knowledge of the cable crosstalk parameters and number of operating systems during the test, is then used to estimate the error margin or eye opening of the repeater, assuming a Gaussian distribution for the interference. A method of ranking repeaters in a repeatered line to indicate their relative margin is proposed wherein the effect of errors on the audio signal to an intermediate test repeater is taken into account. Results presented are quite general and valid at any line rate and repeater spacing, and hence applicable for differentT-carriers such asT1, T1C, T2, etc.     

激光雨滴谱仪降水量反演及误差修正

对激光雨滴谱仪监测的降水粒子粒径、末速度、粒子数等信息进行分析,得到降水粒子的粒径-末速度函数和雨滴谱等关系函数。通过计算得到的降水强度与气象数据对比,得到误差函数;根据误差函数建立降水量反演算法,对降水强度进行修正得到修正后降水强度和降水量,修正后降水量误差减少了10%以上,最后给出降水类型的判断方法。     

激光主动成像结合距离选通技术的零时信号测量方法

针对火箭起飞过程中零时信号难以准确测量问题,提出了激光主动成像与距离选通技术相结合的测量方式,并通过求取光流的变化进而求取位移移动量获得火箭起飞的零时信号。对现有的零时信号测量方式进行了分析,确定了基于距离选通的ICCD成像方式,结合目标垂直上升的特性,提出目标轮廓与HS光流结合的抗光照干扰算法。实验结果表明:在模拟目标匀速上升过程中,在光照变化不大情况下,单独的边缘检测及单独的HS光流检测算法均能检测出目标的上升趋势;在光照变化剧烈情况下,边缘检测及HS光流检测算法均出现严重的误差,目标轮廓与HS光流结合算法排除了目标内部的干扰,得到的目标像素点位移量与真实的上升量基本一致,误差在亚像素量级,若图像帧频为25 fps,则时间精度为80 ms,完全符合零时信号提取的要求。     

An application-oriented error control scheme for high-speednetworks

Many new network applications demand interprocess communication (IPC) services that are not supported by existing transport protocol mechanisms. Large bandwidth-delay products of high-speed networks also render some of the existing error and flow control mechanisms less efficient. In particular, new error control schemes that can provide variable degrees of error recovery according to the application's requirements are desirable. This paper presents the design, evaluation, and implementation of an application-oriented error control-scheme that is aimed at supporting efficient IPC in high-speed networking environments. Our results indicate that the proposed error control scheme allows effective control of the trade-off between the amount of error an application can tolerate and the amount of delay it has to suffer     

Optimal resynchronization marker positioning method using a novel information measure

This paper presents a new resynchronization marker (RM) positioning technique to effectively block the error propagation caused by channel errors. The optimal technique can be defined as the one minimizing the information loss under an error condition. For realization of the optimal technique, the amount of the information lost by errors needs to be measured. Thus, we introduce a novel measure that is successful in reflecting the actual importance of the lost data, which is measured by using error concealment techniques. That is, the amount of information lost by an error at a certain location is numerically specified by the difference between the image recovered by the error concealment and the image normally decoded without any error. Since such a measurement method is appropriate for reflecting the actual damage by errors, it is very useful for determining the RM positions. With the new measure, the optimal RM positioning technique is proposed and verified by experiments.     

电磁张量姿态旋转不变量研究

首先研究了传统基于重叠偶极子模型的几何误差校正方法,该方法需要姿态角测量装置测得仪器的姿态角信息,且具有无法消除姿态角测量装置的安装角度误差、探测区域地形的起伏倾角误差以及感应误差的不足;基于类似的公式推导以及姿态角旋转矩阵中各分量间的等式关系,推导出在层状大地模型下的电磁张量姿态旋转不变量.由模型仿真结果可知,在一个测量周期内,当系统姿态角恒定不变时,垂直共轴、垂直共面以及水平共面三种常用线圈架构由姿态角引起的总误差,分别可以达到12%,11.5%,-11.5%,而不变量的总误差恒为零;当系统姿态角变化率恒定不变时,不变量的总误差随着初始姿态角以及姿态角变化量的增大而增大,且可以忽略发射频率以及大地电导率的影响.若选取的测量周期足够短,此时姿态角变化量足够小,则可以忽略不变量的总误差,从而不再需要测量系统的姿态角信息.已知RESOLVE系统在30 ms的测量周期内翻滚角及俯仰角的初始姿态角均为27°,姿态角变化量均为0.45°,得到不变量在H型层状大地下的总误差仅为-0.21%,验证了不变量的可行性.     

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     

On the atmosphere as an optical communication channel

A reasonable model for the atmosphere as an optical communication channel is presented and then reduced, with some approximation, to an equal-strength diversity system. By using the realistic assumption of a very large variance for the channel's random phase, the operations that the maximum-likelihood receiver must perform are determined. This resulting receiver is also a min-max receiver. Functional bounds to the error probability that results with orthogonal waveforms are determined. The variation of these bounds with the energy-to-noise ratio per diversity path and with the amount of atmospheric turbulence is discussed, and numerical results are presented for the low-rate (union-bound) performance. These results demonstrate that the error probability depends strongly on the amount of turbulence. However, if the amount of diversity can be controlled, the minimum energy-to-noise ratio per information bit for which the error probability can be made to vanish is independent of the turbulence. This minimum is just that which would exist in the absence of turbulence.     

基于抖动的Serdes接口误码率量产测试评价方法

高速串行接口应用的普及给集成电路性能测试带来了新的挑战。误码率(BER)是衡量通信系统性能的关键指标,衡量高速Serdes接口的误码率是十分必要的。通常测试误码率时需要发送大量数据通过长时间稳定的运行,统计接收到的错误比特数来计算误码率,测试时不仅需要大量测试时间,还需在测试路径等硬件中对信号完整性进行优化,避免出现由于测试本身对结果产生影响。从误码率产生的机理出发,探寻一种高效、可靠的误码率评价方法,提出一种基于抖动(jitter)的误码率量产测试方案。     

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     

Low-Dropout Regulators With Adaptive Reference Control and Dynamic Push–Pull Techniques for Enhancing Transient Performance

An adaptive reference control (ARC) technique is proposed for minimizing overshoot/undershoot voltage and settling time of low-dropout regulators. Linear operation provided by the ARC technique can dynamically and smoothly adjust the reference voltage so as to increase the slew rate of error amplifier thus forcing the output voltage back to its steady-state value rapidly. The amount of transient revision is proportional to transient state output voltage variation and load condition. In addition, a dynamic push-pull technique is used to enhance transient response. Experimental results demonstrate that the undershoot voltage, settling time, and load regulation are improved by 31%, 68.5%, and 70%, respectively, when load current changes between 1 and 100 mA.     

Error-resilient image and video transmission over the Internet using unequal error protection

This paper presents a new bit-plane-wise unequal error protection algorithm for progressive bitstreams transmitted over lossy networks. The proposed algorithm protects a compressed embedded bitstream generated by a 3-D SPIHT algorithm by assigning an unequal amount of forward error correction (FEC) to each bit-plane. The proposed algorithm reduces the amount of side information needed to send the size of each code to the decoder by limiting the number of quality levels to the number of bit-planes to be sent while providing a graceful degradation of picture quality as packet losses increase. We also apply our proposed algorithm to transmission of JPEG 2000 coded images over the Internet. To get additional error-resilience at high packet loss rates, we extend our algorithm to multiple-substream unequal error protection. Simulation results show that the proposed algorithm is simple, fast and robust in hostile network conditions and, therefore, can provide reasonable picture quality for video applications under varying network conditions.     

Step-out detection and error compensation for a micro-stepper motor using current feedback

We propose a method to detect step-outs for a micro-stepper motor and a way to compensate the missing steps to maintain appropriate operation. Coil currents and their behaviors are investigated to determine the onset and termination of a step-out. Exact step-out values are identified, and a corresponding compensation scheme is proposed. Even though the use of an encoder to measure position error provides a means of compensating for the error, the primary cause of the error due to the step-outs may not be clearly identified. Rather, the coil current feedback is used in place of encoder measurements, we can clearly determine amount of the step-outs which results in the position error compensation.     

基于校验方程符合度下的Turbo码编码器盲识别

针对目前Turbo码分量编码器参数识别算法容错性不好、计算量大的缺点,该文提出一种基于校验方程符合度的新算法。首先,根据码元约束长度较小的特点,构建出编码器生成多项式数据库,然后通过遍历多项式数据库,计算出每种多项式所对应的平均校验方程符合度值,其最大值所对应的索引号即为多项式库中的正确多项式索引号,从而完成编码多项式的识别。该算法仅仅遍历有限的多项式数据库,其计算量较小,只与截获的数据量有关;算法采用的数据为软判决信息,故其容错性能较好。仿真结果表明：在信噪比为0 dB条件下,仅需要截获10码块,交织长度为100的码元数据量,参数的识别率就能达到90%以上。     

滴胶过程中的Z轴误差补偿

在滴胶过程中能够得到一致性较好的滴胶效果,是芯片粘接的基本要求.影响胶滴一致性的因素有很多,其中滴胶高度是否一致是最主要的影响因素之一.通过对Z轴的误差进行补偿使得滴胶高度保持一致,以消除其对滴胶一致性的影响.实验证明,通过这种方法补偿可以得到满足实验一致性要求的滴胶效果.     

基于滤波方法的OFDM信道估计研究

维纳滤波和卡尔曼滤波都是基于最小均方误差准则的滤波方法,本文主要研究这两种滤波方法在OFDM信道估计中的应用。为了跟踪频率选择性信道的变化,采用在OFDM系统中易于实现的梳状导频进行研究。传统的MMSE在统计意义上是最好的线性估计器,但是需要对矩阵求逆,是一种计算量较大,算法较复杂的方法。LMMSE是频域维纳滤波方法,其减小了MMSE的复杂度,但只适用于慢衰落信道,针对时变信道,本文提出卡尔曼滤波的信道估计方法,仿真结果表明,卡尔曼滤波的信道估计方法在时变信道中具有良好的性能。     

Fuzzy error diffusion

Quantization errors are generally hidden by performing a dithering operation on the image. A common method is to utilize error diffusion. However, this method is prone to error accumulation, resulting in color impulses and streaks. This paper presents a new approach to error diffusion dithering through a fuzzy error diffusion algorithm. In this method, the amount of error to be diffused is determined by considering the relative location of the pixel not only to the closest codebook vector, but to all other palette entries. The goal is to hide the quantization errors by error diffusion, while preventing the excess accumulation of errors. This is achieved through an attraction-repulsion schema according to a fuzzy membership function. We also explored methods to speed up the fuzzy error diffusion process through a L-filter approach by determining a fixed set of membership values. We have implemented the fuzzy error diffusion algorithm for color images and achieved drastic improvements, resulting in superior quality dithered images and significantly lower mean squared error values. A different error measure modeling the characteristic of the human visual system also indicates the superiority of our method.     

The effect of low SNR in phase estimation in wideband CDMA

In wideband code-division multiple-access (CDMA) systems, where large diversity gains are used to mitigate the effects of multipath fading, system performance is increasingly limited by channel estimation error. In a packet-based system, the estimation error can be reduced by increasing the header length; however this, for a fixed bandwidth, reduces the amount of transmit energy available to the data symbols and reduces the processing gain of the system. To determine the allocation of the transmit energy between the data and estimation symbols in order to minimize the probability of bit error, we use an approximate upper bound on the probability of bit error for a RAKE receiver operating with imperfect phase estimates