Incremental digital position encoder with error detection and correction

A digital position encoder is described which combines features of absolute and incremental encoders. A track encoded with a pseudorandom sequence provides absolute position information for an incremental encoder, allowing the detection and correction of errors, while requiring only two code tracks and four read heads.<>     

光电编码器动态误差评估系统

在批量生产小型光电编码器的过程中,出厂检验不仅要对光电编码器动态误差进行检测,也要对不达标编码器进行误差溯源及修正。在实现对光电编码器高、低转速下的动态误差检测的同时,需要快速的定位光电编码器动态误差超标的原因,使生产者能够根据误差超标原因对编码器进行调校。为此,提出了光电编码器检测方法及评估方法,设计了小型光电编码器动态误差检测及评估系统。首先,从低、中、高频率方面对光电编码器误差组成分析,明确了各频率误差的产生原因;然后,提出了采用AR模型谱估计法对动态误差进行评估的方法,并根据误差评估结果给出误差产生因素判定;最后,设计了小型光电编码器动态误差评估系统,实现了对光电编码器的动态误差检测,并给出误差评估结果。所设计的检测系统工作转速范围为0.5~8 r/s,检测精度优于2;误差评估系统能够清晰的显示出动态误差在各频率下的均方值,使生产者能够轻易地找到不达标编码器的调校方法。该系统准确可靠、显示直观,为批量生产光电编码器提供了简单有效的检测评估手段     

Fault tolerant encoders for Single Error Correction and Double Adjacent Error Correction codes

Error correction codes (ECCs) are commonly used to deal with soft errors in memory applications. Typically, Single Error Correction-Double Error Detection (SEC-DED) codes are widely used due to their simplicity. However, the phenomenon of more than one error in the memory cells has become more serious in advanced technologies. Single Error Correction-Double Adjacent Error Correction (SEC-DAEC) codes are a good choice to protect memories against double adjacent errors that are a major multiple error pattern. An important consideration is that the ECC encoder and decoder circuits can also be affected by soft errors, which will corrupt the memory data. In this paper, a method to design fault tolerant encoders for SEC-DAEC codes is proposed. It is based on the fact that soft errors in the encoder have a similar effect to soft errors in a memory word and achieved by using logic sharing blocks for every two adjacent parity bits. In the proposed scheme, one soft error in the encoder can cause at most two errors on adjacent parity bits, thus the correctness of memory data can be ensured because those errors are correctable by the SEC-DAEC code. The proposed scheme has been implemented and the results show that it requires less circuit area and power than the encoders protected by the existing methods.     

基于空间位置的增量式光电编码器误差检测系统

增量式光电编码器输出信号的正交性和均匀性是其重要技术指标之一,对增量式光电编码器的精度检测是编码器研制和生产过程中的重要环节。传统信号质量的检测是基于时间位置进行检测的,其检测准确度受转速均匀度影响,在高速、变速转动下对增量式光电编码器的动态性能检测并不准确。提出了一种基于空间位置的信号质量检测方法,并设计了相应的检测系统。检测系统采用直流无刷电机带动高精度角脉冲发生器和被检增量式编码器同轴旋转,并采集高精度角脉冲发生器在被检增量式编码器输出信号边沿时刻的数值,进行误差计算。该检测系统极大地减小了由于转速不均匀造成的测量不准确度。运用该检测系统对输出脉冲周期数为32 400的增量式编码器进行检测,并与时间位置检测法进行对比实验。实验结果表明:该检测系统检测结果不受电机转速变化的影响,可有效地提高检测精度及检测效率,能够实现动态检测。该系统的研制为批量生产增量式光电编码器提供了极大的便捷。     

基于FPGA的光电编码器接口设计

基于减小导弹舵机系统的体积的目的,采用一个控制器控制四个舵机,舵机控制器以DSP＋FPGA为核心架构,控制器中的编码器接口通过FPGA来实现。根据增量式光电码盘进行位置检测的原理,本文采用Verilog语言,提出了一种基于FPGA的实现增量式光电编码器接口的设计方案。通过实验证明,该接口具有数字滤波、方向鉴别、双向计数、复位等功能,能够与DSP等多种CPU相连。     

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.     

基于CANopen协议的多圈绝对光电编码器的设计

光电编码器是用来检测角度、位置、速度和加速度的传感器。依靠轴杆、齿轮、测量轮或绳缆的控制,线性位移就能被检测。光电编码器把实际的机构参数转换成电气信号,这些信号可以被计数器,转速表、PLC和工业PC处理。光电编码器为每一个轴的位置提供一个独一无二的编码数字值,特别是在定位控制系统中,光电编码器减轻了电子设备的计算任务,从而省去了复杂和昂贵的输入装备。CANopen协议以其成熟的结构,以及抗干扰能力强等优势越来越多地应用到各种工业活动中,成为各种行业的标准,已成为未来现场总线发展的一种趋势。该文介绍使用C8051F504单片机芯片实现光电编码器数据采集和CANopen协议的方法并给出其软硬件设计方案。     

高精度光电编码器莫尔条纹信号质量分析方法

针对莫尔条纹信号质量对高精度编码器细分误差的影响,提出了基于离散傅里叶变换分析莫尔条纹信号质量的方法。该方法利用信号重构和傅里叶变换算法得到信号参数,真实地反应了莫尔条纹信号质量,提高了细分误差测量的准确性。编码器转动时,采集相位差为/2 的两路精码正弦光电信号,通过对采样信号的重构得到信号波形,利用离散傅里叶变换算法分析重构波形,求解信号的直流分量、幅值、相位和谐波分量等各项参数。最后,根据信号参数与细分误差的关系得到光电编码器的细分误差值,并进行了实验验证。实验结果表明,对某24 位绝对式光电轴角编码器细分误差进行测量,细分误差的峰值为+0.48和-0.21。相对于传统的细分误差测量方法,此方法测量速度快,测量精度高,适用于工作现场。     

非均匀采样光电编码器莫尔条纹信号分析方法

为实现高精度光电编码器非匀速转动时动态细分误差的检测,提出了一种基于非均匀采样的莫尔条纹光电信号分析方法.首先,利用曲线拟合的最小二乘法将采集到的编码器非均匀信号数据重构出真实的信号波形.然后,根据离散傅里叶变换算法分析重构信号,同时推导出信号的频率、幅值和相位的计算表达式,运用软件仿真评估算法可行性.最后,采用该方法对某21位绝对式光电轴角编码器精码信号进行分析,根据信号参数与细分误差的关系获得动态细分误差,其细分极值误差为+2.41"和-3.08".实验结果表明,该方法利用信号重构和傅里叶变换算法得到信号参数,真实的反应了莫尔条纹信号质量,在编码器非匀速转动时,可有效地测量动态细分误差,为实际工作现场编码器精度误差的实时检测奠定了基础.     

循环汉明码编译码器的设计与FPGA实现

分析了循环码的特性,提出一种循环汉明码编译码器的设计方案。编译码器中编码采用除法电路,译码采用梅吉特译码器,易于工程应用。对编译码器在FPGA上进行了实现,通过参数化设置,具有较高的码率,适用于(255,247)及其任意缩短码的循环汉明码,并给出了译码器的仿真和测试结果。结果表明:编译码器运行速率高、译码时延小,在Virtex-5芯片上,最高工作时钟频率大于270 MHz。在码组错误个数确定的系统应用中,可以有效降低误码率,一般可将误码率降低一个量级。实践表明,该设计具有很强的工程实用价值。     

Convolutional codes I: Algebraic structure

A convolutional encoder is defined as any constant linear sequential circuit. The associated code is the set of all output sequences resulting from any set of input sequences beginning at any time. Encoders are called equivalent if they generate the same code. The invariant factor theorem is used to determine when a convolutional encoder has a feedback-free inverse, and the minimum delay of any inverse. All encoders are shown to be equivalent to minimal encoders, which are feedback-free encoders with feedback-free delay-free inverses, and which can be realized in the conventional manner with as few memory elements as any equivalent encoder, Minimal encoders are shown to be immune to catastrophic error propagation and, in fact, to lead in a certain sense to the shortest decoded error sequences possible per error event. In two appendices, we introduce dual codes and syndromes, and show that a minimal encoder for a dual code has exactly the complexity of the original encoder; we show that systematic encoders with feedback form a canonical class, and compare this class to the minimal class.     

Autocorrelation properties of channel encoded sequences-applicability to blind equalization

Many blind channel equalization/identification algorithms are derived assuming the transmitted information sequence to be white. In practical communication systems, redundancy is added to the source sequence in order to detect and correct symbol errors in the receiver. It is not obvious how channel encoding will affect the assumption of whiteness. The autocorrelation function of some commonly used channel codes is analyzed in order to study the validity of assumptions used in blind equalization. The codes are presented in terms of a Markov model for which the autocorrelation is analytically expressed. The various encoded sequences are used in a prediction error based blind equalizer, and the performance is empirically compared with the case of unencoded data. A blind equalization example using a practical GSM speech encoder combined with a convolutional channel encoder is also given.     

光电编码器的动态误码检测系统

为了实现对光电编码器在动态状态下的误码检测，提高批量生产时对光电编码器的误码检测速度，设计了光电编码器动态误码检测系统。首先，对光电编码器误码产生原因进行了分析，并对光电编码器误码进行特征识别。其次，针对光电编码器误码的特征，采用微分方法对光电编码器进行动态误码检测。然后，搭建了光电编码器动态误码检测系统，设计了软硬件电路。最后，对所设计光电编码器动态误码检测系统进行实验验证。实验表明:所设计的动态误码检测系统能够实现对0~8 r/s转速下光电编码器的误码检测，检测结果直观、准确。检测系统极大的提高了批量生产光电编码器时的检验速度。     

基于FPGA的多路增量式光电编码器测角电路设计方法

提出了一种基于FPGA的多路增量编码器测角电路设计方案,它主要由4倍频电路、方向判别电路和计数电路组成。计数采用单时钟,能输出表示光电编码器位置的12位数字量和旋转方向指示电平。整个电路设计在Altium Desig-ner 6.0软件环境下由电路图和VHDL编程混合输入,采用Xilinx公司的XC25300E-6PQ208C型芯片进行仿真验证。仿真和实现结果验证了该方案可应用于高转速下的多路测角系统。     

Sensorless Maximum Power Point Tracking of Wind by DFIG Using Rotor Position Phase Lock Loop (PLL)

This paper presents an invention, the rotor position phase lock loop (PLL), which enables maximum power point (MPPT) tracking of wind by doubly-fed induction generators without needing a tachometer, an absolute position encoder, or an anemometer. The rotor position PLL is parameter variation insensitive, requiring only an estimate of the magnetization inductance for it to operate. It is also insensitive to noise in the electrical measurements. Proof of concept is by: (1) digital simulations and (2) experimental testing of a laboratory prototype.     

基于径向基函数神经网络的高精度基准编码器误差补偿

高精度角度基准编码器的角度误差,对小型绝对式光电编码器误差检测装置的测量精度有着重要的影响。影响基准编码器角度误差的因素众多,难以用准确的数学模型来描述。为此提出一种通过径向基函数神经网络进行误差修正的方法。首先,为增加基准编码器检测采样点,使用多种多面体对基准编码器进行检测,并将误差合成在同一坐标曲线上。然后,利用检测误差结果作为训练样本,建立径向基函数神经网络模型,使其输出逼近真实角度。最后,通过补偿电路的设计,对小型编码器误差检测装置的基准编码器进行补偿。实验表明,补偿电路的处理速度快,实现简单,不受算法复杂度影响。补偿后的编码器精度提高了2 倍,有效改善了检测装置的检测精度。     

增量式数字光纤传感器的数码检测

当测量要求采取不受漂移和强度误差影响的数字形式时,采用线性或角度数字编码器,本文设计了一种数字光纤传感器,通过光的反射实现增量式数码器的数码读取与识别,我们提出了用2个码道的编码器响应在左－右（或顺时针－逆时针）2个方向上的变化,分析表明该位移传感器具有较强的抗零漂和抗强度误差的能力。     

A rotary encoder based on magneto-optical storage

A new kind of the rotary encoder based on the magneto-optical (MO) storage is proposed. Using the MO methods, a small high-precision high-response rotary encoder can be realized. High precision is achieved by a two-stage process in which the code disk is firstly written using the direct transfer recording, and then rewritten using the corrections based on the measured errors. The systems for writing to, reading from, and evaluating the MO encoder are developed, with the optimal MO encoder reading and writing parameters determined experimentally. A trial MO encoder with a resolution of 9000 pulses/revolutions is created directly from a reference encoder, delivering an accuracy of approximately 2.8 in. The maximum resolution and response frequencies achieved are 18000 p/r and 400 kHz. After the corrected transfer recording, accuracies of 1.3 in at a resolution of 2250 p/r and 1.7 in at 9000 p/r are achieved.     

莫尔条纹光电信号细分误差的实时补偿

为了保证高精度光电轴角编码器在恶劣工作条件下的细分精度,设计了基于高分辨率数字电位计的实时补偿处理系统。依据莫尔条纹光电信号的数学模型,说明了由信号等幅性偏差和直流电平漂移引起的细分误差的空间分布特征,并得出误差规律及计算公式,从编码器的光机装调、码盘均匀性、光敏元件调试等制作环节出发,指出了编码器光电信号细分误差的根本特性;受高精度光电编码器分辨力的约束,从编码器光敏元件输出莫尔条纹信号的形式出发,构建了分辨率为0.1 的数字电位计查找表;并设计了实时补偿的关键算法。以23位光电编码器为实验对象,在-40～60 ℃条件下对补偿处理系统测试,实验结果表明:直流漂移1.2%,等幅性2%,且自动补偿时间约为3 s,满足编码器分辨力（0.154）和工作实时性的要求。该方法可实际应用于编码器系统,能够提高编码器的环境适应性和测角可靠性。     

低功耗低误码率的传感器网络节点芯片数字基带设计

本文针对无线传感器网络节点片上系统特点和需求,研究一种低功耗、高性能、低误码率的数字基带(Easibaseband),提出了一种复用加法器和乘法器的设计方法,实现了匹配滤波器,可节省硬件资源并提高系统性能;提出了一种自适应门限的自动增益控制方法,可配合软硬件协同的工作方式,节省接收机的功耗;提出了采用自适应门限的施密特触发器方式进行信号相位判决的方法,降低了解调误码率.本设计在Xilinx的Spartan-3E FPGA上验证并实现,测试结果表明,本收发机的数据传输率可达到111kb/s并支持ISM2.4GHz频段的射频芯片,比传统的并行滤波器节省了5/6的硬件资源,比不采用自动增益控制节省了10.8%的接收机功耗,在信噪比13dB时,误码率在10-4以下,远低于WiseNET的接收误码率.