Absolute, high-resolution optical position encoder

Modern computer-controlled manufacturing machinery requires the absolute and highly accurate measurement of the linear position. Such an absolute, optical linear position encoder is described here. It is based on the transilluminance of a glass scale with an inexpensive light-emitting diode. The scale has two code tracks, one based on a pseudo-random binary sequence for the coarse determination of position and another periodic code for accurate fine-position measurement. A single-lens telecentric optical system images the code tracks in a mechanically insensitive way onto a custom photodetector. This special detector IC is capable of determining the components of the (complex) Fourier transform for the spatial frequency of the periodic code. The absolute optical position encoder shows a resolution of 10 nm and an absolute accuracy of better than 100 nm over short distances, verified with a commercial laser interferometer.     

基于伪随机序列的索引式绝对位置编码

提出了一种基于伪随机序列的索引式绝对位置编码,介绍了它在绝对位置角度传感器中的应用和生成方法。由于它是一种单码道绝对位置编码,克服了传统位置编码随精度提高而码道增多、工艺上不易实现的缺点,可缩减码盘的直径,为绝对位置角度传感器的高精度、小型化开辟了一条新的途径。     

Error-detecting unit-distance code

A particular kind of unit-distance code is proposed. Unit-distance codes are applied especially to absolute encoders (linear or rotary). The various positions of the encoder are represented by the various code words of the code. In contrast to conventional unit-distance codes, this code offers the possibility of detecting all single-bit errors except the two single-bit errors that cause a code word which represents the adjacent position. Unit-distance codes are characterized by a Hamming distance of 1. Thus, Hamming distance is not a unit of measurement for the code's error-detection ability. Therefore, a Hamming distance is defined especially for unit-distance codes excluding the adjacent code words from the calculation of distances. An application shows the utility of the code in the field of instrumentation and measurement     

超小型准绝对式编码器的研制

针对编码器日趋小型化的技术要求,本文提出一种全新的编码方式和独特的读数头设计结构,成功研制出了超小型准绝对式编码器.该新型编码器采用准绝对式编码方式,即距离编码与增量式编码进行组合编码,只用两圈码道进行编码,极大减少码道数量,整周设多个绝对参考位置,可迅速获得绝对位置信息.采用单读数头结构和相位补偿技术,缩小结构尺寸,直径Ф25 mm,经过电子学细分后可到达16位的分辨力,从而实现高精度编码器小型化.     

ISP器件在多圈绝对式编码器中的应用

多圈绝对式编码器既可以测量一周之内的角度值,又可以测量旋转轴的旋转圈数。ISP (在系统可编程)器件1016E在双盘多圈编码器中,主要完成码制转换、校正逻辑、加法逻辑及一些辅助逻辑等所有数字电路功能。ISP的应用减小了编码器体积,提高了稳定性,还使一种结构、多种输出组合成为可能,并可方便地将并行输出信号转换为串行信号。     

Method of all-optical frequency encoded decimal to binary and binary coded decimal, binary to gray, and gray to binary data conversion using semiconductor optical amplifiers

Conversion of optical data from decimal to binary format is very important in optical computing and optical signal processing. There are many binary code systems to represent decimal numbers, the most common being the binary coded decimal (BCD) and gray code system. There are a wide choice of BCD codes, one of which is a natural BCD having a weighted code of 8421, by means of which it is possible to represent a decimal number from 0 to 9 with a combination of 4 bit binary digits. The reflected binary code, also known as the Gray code, is a binary numeral system where two successive values differ in only 1 bit. The Gray code is very important in digital optical communication as it is used to prevent spurious output from optical switches as well as to facilitate error correction in digital communications in an optical domain. Here in this communication, the author proposes an all-optical frequency encoded method of ":decimal to binary, BCD," "binary to gray," and "gray to binary" data conversion using the high-speed switching actions of semiconductor optical amplifiers. To convert decimal numbers to a binary form, a frequency encoding technique is adopted to represent two binary bits, 0 and 1. The frequency encoding technique offers advantages over conventional encoding techniques in terms of less probability of bit errors and greater reliability. Here the author has exploited the polarization switch made of a semiconductor optical amplifier (SOA) and a property of nonlinear rotation of the state of polarization of the probe beam in SOA for frequency conversion to develop the method of frequency encoded data conversion.     

高精度绝对式编码器的信号处理

介绍了一种新的光栅编码器数据处理方案－－多读数头数字量相加,主要采用ＭＣＳ８０３１单片机为核心控制器,将编码器的多个读数头信号分别量化,再相加平均。该方法不仅能提高编码器的测角精度,更重要的是可大大提高编码器的工作可靠性。     

Concatenated peak-to-average power ratio reduction scheme with threshold limited selection for coded orthogonal frequency-division multiplexing

The authors propose a concatenated scheme to reduce the peak-to-average power ratio (PAPR) in coded orthogonal frequency-division multiplexing (OFDM) systems. First, they employ a label-bits-inserted encoder of a random-like code to achieve selected mapping (SLM). Then they set a threshold at the selector to limit the number of candidate sequences. Both analytical and numerical results show that the complexity of the SLM implemented by the label-bit-inserted encoder can be significantly reduced by threshold limited selection. With the same complexity, the performance of PAPR reduction is improved. The proposed concatenated PAPR reduction scheme enjoys many advantages including low-complexity, small overhead, no side information transmission and no performance loss or additional complexity at the receiver.     

一位码纠错编码器的可编程逻辑器件实现

纠正数字信号在传输中出现的差错,逐渐成为数字通讯系统中的一个突出问题,这就要求采取适当的编码方法,及时发现并纠正错误,来提高信息传输的可靠性。本文简单介绍了用（１２,８）码纠正一位错误码元的原理;详细讨论了用一片Ｌａｔｔｉｃｅ ｉｓｐＬＳＩ１０１６芯片实现（１２,８）码编码器和解码器的设计方法。     

25位绝对式编码器

介绍了在高位数、高精度光电绝对式轴有编码器小型化研制中,采用特殊的绝对编码技术和多读数头模拟量相加获得高质量的光栅信号,并用单片机实现高倍的电插补细分,成功地研制出了小尺寸的２５位高精度绝对式编码器。     

New Learning Algorithm for High-Quality Velocity Measurement and Control When Using Low-Cost Optical Encoders

A new compensation method that can greatly reduce the slit errors (i.e., transition location errors) due to nonidealities in optical incremental encoders caused by manufacturing limitations in the code wheel, optical components, and analog circuitry is presented. An M/T-type constant sample-time digital tachometer (CSDT), which involves pulse-count and high-frequency timer measurement, effectively time-stamps the encoder transitions. Using CSDT-based data, encoder compensation techniques that improve velocity measurement accuracy are presented. These do not require precise knowledge of the shaft velocity, thereby eliminating the need for high-accuracy reference equipment. During the initial learning stage (possibly performed in situ ), slit errors are calculated through pseudoinverse-based solutions of simple approximate linear equations or an iterative method that requires very little memory storage. Subsequent operation of the motion system utilizes adjusted slit positions for more accurate velocity calculation. The performance improvement in velocity measurement is experimentally demonstrated using motor drive systems, each of which includes a field-programmable gate array (FPGA) and a digital signal processor (DSP). Results from open-loop velocity measurement and closed-loop servo control applications are given, with the latter highlighting the resultant reduction in high-frequency motor torque. Slit error reductions in the range of 60%–86% are obtained (typically approximately 80%) with a similar improvement in velocity measurement error.      

High-resolution of rotary encoder analog quadrature signals

The paper describes a software technique to provide high-resolution absolute angular measurements from the analog quadrature signals of a rotary encoder. The method uses digitized samples of the sinusoidal quadrature signals and the output of a divide-by-four counter circuit. Dynamic measurements on an external trigger signal are possible allowing instantaneous up-to-date angular readings even at high speed. The resolution and hysteresis errors are only dependent on the encoder itself and the bandwidth and resolution of the sampling circuitry. The scheme allows up to 135 degrees of counter hysteresis and delay without loss of precision, thus also affording excellent noise immunity. The theoretical resolution for a 12-bit digital conversion of the analog signals is 1/3360 of a pitch. Experimental results on an encoder built into a laser-tracking measurement system and using 81000 pitches show a unidirectional precision of 0.3 arcsec (rms), a mean bidirectional hysteresis of about 1 arcsec and a worst case variation for a stationary encoder shaft of 0.06 arcsec     

Distributed source coding using symbol-based and non-binary turbo codes - applications to wireless sensor networks

A simple but powerful scheme for distributed source coding (DSC) based on the concept of binning and syndromes and non traditional turbo codes is proposed. The previous works on the compression with side information using turbo codes and the binning technique are focused on binary turbo codes. The source is considered to be binary or is converted to a binary stream. This conversion, however, reduces the redundancy that could be exploited by the compression algorithm. To achieve higher compression efficiency, the authors propose using a scheme based on a turbo decoder that decides over symbols rather than bits. In the same direction and for further performance improvement, at the cost of increased encoder complexity, they also present a DSC scheme based on non-binary turbo codes. The results demonstrate improved performance. Based on the suggested algorithms, a scheme for gathering real data in wireless sensor networks and assess the corresponding energy savings is proposed.     

Diffractive incremental and absolute coding principle for optical rotary sensors

Rotary sensors are an essential component in numerous applications where a rotation movement has to be detected. With optical encoders, a high angular resolution can be achieved. As a disadvantage, the resolution enhancement is associated with increasing cost. To overcome this issue, a coding principle is presented that uses a diffractive solid measure on a microstructured plastic disc. Like a DVD, this encoder disc can be manufactured in a cost effective injection molding process. For this approach, a differential incremental code, as well as an absolute code, has been developed.     

Covariance-based approach to texture processing

We present a simple and effective approach for texture processing that uses the eigenfeatures of local covariance measures. The covariance measures act as a texton encoder, producing texture code that is invariant to local and global textural rotations. This method uses only six features obtained from two scales of the invariant encoder to generate numerical representations for roughness, anisotropy, and other higher-order textural features. Classification results for synthetic and natural textures are presented. We discuss the effect of window sizes used at local and global scales on the performance of the classifier.     

新型绝对零位粗光栅的研究

本文在总结国内外粗线纹光栅绝对零位实现方法的基础上，提出了一种新型绝对零位粗光栅的方案。它克服了传统粗化栅采用栅动开关作为附加零位标志的缺点，将零位标志直接刻制在粗光栅尺上，采用编码识别的方法，用专用自扫描光电二极管列阵ＣＧ２００Ｓ提取粗定位信号，结合列阵自扫描起始信号Ｓ及其调相测量信号ＭＳ的边沿触发脉冲，产生高精度绝对零位脉冲。既保证了系统精度，又解决了粗光栅与绝对零位一体化的问题。为进一步研制     

Two-dimensional position recovery for a free-ranging automatedguided vehicle

An absolute position recovery method for an automated guided vehicle (AGV) which can move in any direction (free-ranging) on the floor using vision is introduced. The floor is permanently encoded with the terms of a pseudorandom binary array requiring only one bit of code per quantization interval, independent of the desired resolution     

A 3.2 kHz, 14-Bit Optical Absolute Rotary Encoder With a CMOS Profile Sensor

We have developed a 3.2 kHz, 14-bit optical absolute rotary encoder system using a profile sensor and a slit disc. The profile sensor, which we have designed for this purpose, is a unique CMOS area image sensor aimed at high-speed position detection of X and Y axes. Y axis profile data from the profile sensor is used for recognition of an index code on the slit disc, and X axis profile data is used for position detection of the index code. This combination of two-axis information enables high resolution even with a small number of index codes (64 indexes) and a small amount of digital calculations. Experimental results show that this system can detect rotation with an angular resolution of 14 bits (0.022deg) and a maximum detection speed of 3.2 kHz.     

A robust scheme for concurrent error diagnosis of MINs

Abstract

Two similar schemes for detecting and correcting errors as well as locating both permanent and temporary faults in multistage interconnection networks for multiprocessor systems are proposed. Depending on the design purpose, two systematic SEC‐DED‐AUED (single error correction‐double error detection‐all unidirectional errors detection) codes are chosen to meet the need of detecting all unidirectional errors which are prevalent in VLSI and to correct all single errors and some multiple errors. The results of encoding and error correcting may be checked by totally self‐checking checkers for Berger code if desired, and thus ensure the robust functioning of the encoder and corrector at the expense of more hardware redundancy. Locating the faulty spots can be done by analyzing the source and destination tags in the corrected packets. The result shows that the two proposed schemes improve the previous schemes at the expense of about 14% and 11% lower information rate for 64‐bit information.     

绝对值编码器在焙烧天车夹具提升机构中的应用

针对焙烧天车夹其提升运行中存在的问题，使用绝对值编码器进行保护。介绍绝对值编码器选型、安装及调试过程，以及在控制系统硬件和软件的组态方法，提高设备的安全性及稳定性。