雷达遥感农业应用综述

雷达遥感具有全天时、全天候监测的能力,对植被具有一定的穿透能力,对植被散射体形状、结构、介电常数敏感;这些特性使得其在农业应用中极具潜力。该文首先介绍了雷达遥感在农业中的应用领域,概略总结了目前在农作物识别与分类、农田土壤水分反演、农作物长势监测等多个领域研究的综述文献;然后分别阐述了雷达散射计和各类SAR特征(包括:SAR后向散射特征、极化特征、干涉特征、层析特征)在农业各领域中应用的现状和取得的研究成果,最后结合农业应用需求和SAR技术发展总结了目前研究中存在的问题和原因,并对未来的发展进行了展望。      

Active microwave sensing of the Earth's surface--A mini review

Radar has been used for remotely sensing the surface of the land and sea since the middle of World War II, but only since the mid-1960's has this technique become widely used for civil purposes. The nature of radar backscatter and theoretical models that have been used to describe it are briefly described. The state of knowledge of radar return from both land and sea is summarized. The principal radar remote sensing instruments are briefly described. A summary is presented of applications of sidelooking radar to observing the land and of various radar sensors (SLAR, scatterometers, altimeters) to observing the sea. Finally, the future of this technique is assessed both in terms of the applications and instruments to be expected during the remainder of the 1970's and the following decade and in terms of research that is needed for radar remote sensing to realize its full potential.     

基于成像激光雷达的地形辅助导航研究

成像激光雷达通过扫描可以测量高精度的地形数据,基于成像激光雷达的地形辅助导航系统是纠正惯导误差的有效手段.根据激光雷达测距模型提出了基于成像激光雷达的地形辅助导航系统,将激光雷达看作一个多维距离传感器阵列,利用卡尔曼滤波器迭代估计系统的状态误差,从而纠正惯导累积误差.根据激光雷达测距关系推导了系统的扩展卡尔曼滤波方程,并对成像激光雷达多维测量数据采用最小均方误差准则进行融合,融合滤波器组合了多个测量数据的信息,有效克服了测量噪声和数据丢失对单个滤波器的影响,从而提高了导航性能.然后利用局部可观测性对系统的性能进行了分析,并对提出的算法作了大量的仿真实验进行验证.     

Noise Temperature Characteristics and Gain-control of Avalanche Photodiodes for Laser Radar

Avalanche photodiodes（APDs） are promising light sensors with high quantum efficiency and low noise. It has been extensively used in radiation detection, laser radar and other weak signal detection fields. Unlike other photodiodes, APD is a very sensitive light detector with very high internal gain. The basic theory shows that the gain of APD is related to the temperature. The internal gain fluctuates with the variation of temperature. Investigated was the influence of the variation of the gain induced by the fluctuation of temperature on the output from APD for a very weak laser pulse input in laser radar. An active reverse-biased voltage compensation method is used to stabilize the gain of APD. An APD model is setup to simulate the detection of light pulse signal. The avalanche process, various noises and temperature＇s effect are all included in the model. Our results show that for the detection of weak light signal such as in laser radar, even a very small fluctuation of temperature could cause a great effect on APD＇s gain. The results show that the signal-tonoise ratio of the APD＇s output could be improved effectively with the active gain-control system.     

Development of 3D Scanning System for Robotic Plasma Processing of Medical Products with Complex Geometries

This paper describes the development of an intelligent automated control system of a robot manipulator for plasma treatment of medical implants with complex shapes. The two-layer coatings from the Ti wire and hydroxyapatite powders are applied on the surface of Ti medical implants by microplasma spraying to increase the biocompatibility of implants. The coating process requires precise control of a number of parameters, particularly the plasma spray distance and plasma jet traverse velocity. Thus, the development of the robotic plasma surface treatment involves automated path planning. The key idea of the proposed intelligent automatic control system is the use of data of preliminary three-dimensional (3D) scanning of the processed implant by the robot manipulator. The segmentation algorithm of the point cloud from laser scanning of the surface is developed. This methodology is suitable for robotic 3D scanning systems with both non-contact laser distance sensors and video cameras, used in additive manufacturing and medicine.     

Design of 24 GHz Radar with Subspace‐Based Digital Beam Forming for ACC Stop‐and‐Go System

For an adaptive cruise control (ACC) stop‐and‐go system in automotive applications, three radar sensors are needed because two 24 GHz short range radars are used for object detection in an adjacent lane, and one 77 GHz long‐range radar is used for object detection in the center lane. In this letter, we propose a single sensor‐based 24 GHz radar with a detection capability of up to 150 m and ±30° for an ACC stop‐and‐go system. The developed radar is highly integrated with a high gain patch antenna, four channel receivers with GaAs RF ICs, and back‐end processing board with subspace based digital beam forming algorithm.     

激光雷达截面在系统设计评价中的应用分析

讨论分析了激光雷达截面在激光测量系统设计评价中的应用.分析了激光雷达截面的物理意义,给出了目标激光雷达截面的计算、测量原理与方法,从激光雷达截面的理论定义出发,推导出普遍适用于各类激光测量系统和各种散射特性目标的基本测量方程,该方程利用激光雷达截面表征目标的激光散射特性.通过典型实例说明了该方程在激光测量系统设计评价中的应用.与其他用于表征目标激光散射特性的指标相比,激光雷达截面更容易通过计算或测量得到,且更适用于复杂散射特性目标,因此,在激光测量系统的设计评价中应采用由目标激光雷达截面表述的激光测量方程.     

Development of automated real-time data acquisition system for robotic weld quality monitoring

The lack of reliable non-contact, non-destructive, online sensors with the ability to detect defects as they form and with the capacity to operate at high temperatures and in harsh environments is a big obstacle to fully automated robotic welding. This paper presents a non-contact automated data acquisition system for monitoring a robotic gas–metal arc welding process based on laser ultrasonic technology. While a robot welds between two 1040 steel strips, a Nd:YAG Q-switched pulse laser generates ultrasound on one side of the weld by ablation, and a non-contact electro-magnetic acoustic transducer (EMAT) placed on the opposite side of the weld detects ultrasound transmitted through the weld bead. Ablation is employed because high temperature specimens require strong signals to compensate for attenuation within the bulk of the material. The data is then analyzed to determine the time required for ultrasound to travel from the laser source to the EMAT, termed as the time of flight (ToF). When experimental ToF is compared to theoretical ToF, it is determined that surface waves are detected by this system. Therefore, this system can measure weld bead reinforcement distance. In most cases, weld bead geometry is an indication of the weld quality, and can be used as feedback to control a welding process.     

Bioinspired Triboelectric Nanogenerators as Self‐Powered Electronic Skin for Robotic Tactile Sensing

Electronic skin (e‐skin) has been under the spotlight due to great potential for applications in robotics, human–machine interfaces, and healthcare. Meanwhile, triboelectric nanogenerators (TENGs) have been emerging as an effective approach to realize self‐powered e‐skin sensors. In this work, bioinspired TENGs as self‐powered e‐skin sensors are developed and their applications for robotic tactile sensing are also demonstrated. Through the facile replication of the surface morphology of natural plants, the interlocking microstructures are generated on tribo‐layers to enhance triboelectric effects. Along with the adoption of polytetrafluoroethylene (PTFE) tinny burrs on the microstructured tribo‐surface, the sensitivity for pressure measurement is boosted with a 14‐fold increase. The tactile sensing capability of the TENG e‐skin sensors are demonstrated through the characterizations of handshaking pressure and bending angles of each finger of a bionic hand during handshaking with human. The TENG e‐skin sensors can also be utilized for tactile object recognition to measure surface roughness and discern hardness. The facile fabrication scheme of the self‐powered TENG e‐skin sensors enables their great potential for applications in robotic dexterous manipulation, prosthetics, human–machine interfaces, etc.     

Force sensing microinstrument for measuring tissue properties and pulse in microsurgery

Miniaturized and "smart" instruments capable of characterizing the mechanical properties of tiny biological tissues are needed for research in biology, physiology, and biomechanics, and can find very important clinical applications for diagnostics and minimally invasive surgery (MIS). We are developing a set of robotic microinstruments designed to augment the performance of surgeons and clinicians during MIS. These microtools are intended to restore (or even enhance) the finger palpation capabilities that the surgeon exploits to characterize tissue hardness and to measure pulsating vessels in traditional surgery, but which are substantially reduced in MIS. This paper describes the main applications and the performance of a prototype miniature robotic instrument consisting of a microfabricated microgripper, instrumented with semiconductor strain-gauges as force sensors. The experimental set-up used for the in vitro tests reported in this paper consists of the microprobe mounted on a workstation and teleoperated. A haptic interface provides force feedback to the operator. We have demonstrated that the system can discriminate, both qualitatively and quantitatively, tiny skin samples based on their different elastic properties, and "feel" microvessels on the basis of pulsating fluid flowing through them.     

A cascadable polarization-based 1-to-9 multimode optical fiberswitch using a PMMA fiber array holder

We have constructed an optical fiber switch, which allows to route an information carrying laser beam to nine multimode optical fibers. The fibers are accurately positioned in a polymethylmethacrylate (PMMA) fiber array holder, fabricated with deep proton lithography. To switch light from one fiber to another, we use active control of the polarization of light by means of nematic liquid crystal retarders or ferroelectric polarization rotators. The system shows insertion losses as low as 3 dB and crosstalk ratios below -30 dB. These figures are still susceptible to considerable improvements. The switching speed is on the order of 10 Hz using nematic liquid crystals and was extended to 10 kHz with ferroelectric liquid crystals. Potential applications of the fiber switch are discussed. As an illustration we have demonstrated the multiplexing of optical fiber proximity sensors. We also describe scale reduction and cascadability issues     

Hybrid integration of GaAs-based VCSEL array with amorphous silicon sensor

We describe an optoelectronic module incorporating a vertical-cavity surface-emitting laser (VCSEL) array with a semitransparent light monitor. The power monitor is a p-i-n amorphous silicon photodetector fabricated on glass. Sets of micromachined springs for electrical contacting are also fabricated in the same process on the same glass substrate. Hybrid packages are formed by pressing the compliant springs against individual contact pads of the GaAs VCSEL array in a flip-chip assembly process. The light sensor is aligned directly on top of the laser elements. Most of the laser light is transmitted through the sensor, yet a large dynamic range is maintained because of the sensors exceedingly low dark current.     

光子学技术与环境污染监测

工业革命在使生活现代化的同时也把一个污染的环境留给了人类．光子学技术（包括光谱技术、二极管激光气体传感技术、光纤化学传感器及激光雷达）可广泛地应用于环境污染监测．     

钬激光应用与进展

钬激光是高相干辐射光,在雷达、测距以及医疗等多方面有着广泛的应用。根据钬激光的发展历程,总结出提高其输出功率及效率所需改进的几个方向,包括晶体材料的选择、掺入杂质及浓度的研究。进一步阐述了钬激光在各领域的应用与前景,并重点讨论了Ho:YAG激光在医疗领域的应用。     

激光雷达应用技术研究进展

随着激光成像雷达技术的快速发展,激光雷达三维点云数据在多个领域展现出良好的应用前景。本文首先概述了激光雷达的基本原理和性能优势,进而重点阐述了激光雷达在调查监测、建模测绘、探测测量、医疗、军事等各方面的实际应用。     

Neural network optimization for multi-target multi-sensor passivetracking

In this paper, we review a number of neural network approaches to combinatorial optimization. We specifically address the difficult problem of localizing multiple targets using only passive sensors, i.e. the sensors detect only bearing angles. Thus, target positions must be found through triangulation. An efficient solution to this problem has been of particular interest in air defence applications. In this paper, we describe two different neural network based approaches for solving this passive tracking problem. In particular, we demonstrate the use of a Hopfield neural network to preface the subsequent development of the multiple elastic modules (MEM) model. The MEM model is presented as a significant extension to current self-organizing neural networks. We describe the unique features of the MEM model, including nonhomogeneous adaptive temperature field for escaping from poor local optima, and locking and expectation features used for dealing with dynamic real-world problems. Applications of the MEM model to other areas including computer vision, are also briefly described     

二极管泵浦固体激光雷达技术及其应用

二极管泵浦固体激光雷达是最近几年成像激光雷达发展的重点,它采用高重复频率、高峰值功率的二极管泵浦固体激光器、高灵敏度的雪崩二极管探测器,其主要优点是体积小、价格低,可用扫描成像或非扫描 成像,探测大多采用直接探测体制,在军事和国民经济中都有着广阔应用前景。文中简要介绍了二极管泵浦固体激光雷达的研究及其在军事中的应用,包括精确制导、风速测量和直升机防撞等。以几种典型激光雷达为例,概括了激光雷达研究中需要解决的部分关键技术。     

Wireless identification and sensing using surface acoustic wave devices

Today Surface Acoustic Wave (SAW) devices are used in many electronic products, e.g. as filters in communications applications or for signal processing in radar systems. Due to the dependence of the propagation characteristic of the microacoustic wave on many physical parameters (e.g. temperature or strain) it is possible to build SAW sensors for a great variety of physical, chemical and biological parameters. SAW sensors are not only small, rugged and show small aging rates, they also can be used as wirelessly interrogable and completely passive sensors for many hostile environments. In this contribution the SAW device principles, design procedures and technological issues as well as examples of their use in certain measurement and identification applications are reviewed.     

An intelligent robotic system for rehabilitation of joints andestimation of body segment parameters

An an application of robotics in physical rehabilitation therapy, a robotic system consisting of two planar robot arms, each with two degrees of freedom, is considered. This robotic system, when coupled across a human joint, provides a vehicle for rehabilitation of the joint following surgery or trauma. A novel approach for estimation of body segment parameters is formulated that uses state and output information from the robot system to improve these estimates. In addition, redundant sensors are used to improve the accuracy of the estimates. The dynamic equations for a single robot arm are provided and the system is simulated. Therapeutic applications of the robotic system are discussed and the sensitivity of the measured forces with respect to the robot arm joint angles is studied in order to find an optimum orientation of the system for the best possible estimation. The application of this system to both rehabilitation and sports medicine is also discussed