基于激光雷达的移动机器人避障控制研究

以VFH算法思想为基础,提出适用于激光雷达的数据处理算法,将其作为避障算法用于移动机器人的室内自主行进过程中。根据室内避障问题的特点,通过仿真研究设计了适用于室内避障的障碍物阈值规则。在移动机器人实验中发现,受室内地面环境影响,直接将仿真程序应用到移动机器人实际操作中,会出现打滑偏航乃至不能顺利到达目标点的严重后果。为此,根据航向角变化率提出了分段降速方法,应用该方法移动机器人在起始点与目标点可以自主移动,验证了算法的有效性与实用性。     

基于SR-Context的激光雷达点云闭环检测算法

针对传统激光雷达闭环检测算法受动态障碍物干扰较大、关键帧搜索以及特征匹配耗时较长的问题,采用MF-RANSAC算法并改进ScanContext,提出一种鲁棒性更强、耗时更短的SR-Context激光雷达闭环检测算法.首先,利用区域生长算法对扇形栅格化后的点云进行分割;随后,不依赖于目标识别和跟踪,借助动态区域多点选取和...     

基于背景特征参数的激光雷达目标检测

激光雷达的弱小目标检测是激光雷达的关键技术, 其主要研究难点之一是在低信噪比下, 可用于区分目标与背景噪声的特征少。研究的对象是激光雷达的远距离目标回波, 主要指空中飞机目标。根据试验得到的数据, 发现目标点在背景中往往是一些孤立的点, 与背景的相关性较小。而背景中的任一点与前后背景点相关性较强, 可以用周围的点进行线形或非线性表示。为解决低信噪比下激光雷达的目标检测问题, 提出了基于背景特征参数的目标检测算法。运用高阶统计量作为背景特征值对杂波数据进行处理。在一个小区域内, 背景的高阶统计量不会有很大的起伏, 而目标在它所在的区域内具有相对突出的变化。信噪比得以提高, 然后通过恒虚警检测和多帧相关检测, 获取真正的目标。试验结果表明该方法非常有效, 实时性强, 具有较高的实用价值。     

基于尾流激光雷达的能量对消式大动态接收技术

水下尾流激光雷达在近场就已开始与水体发生了激光的多次散射, 很容易导致接收系统因动态范围不够而饱和, 其反向恢复时间一般长达10² ns级, 影响远场信号接收.本文针对此问题分析了激光水体后向光散射强度衰减规律, 自主研发了一种能量对消式水下激光雷达前端接收系统. 该系统通过在近场强信号尖峰上叠加一个高速反向瞬态对消电流抑制接收系统饱和, 之后将两信号融合, 还原真实回波信号波形.分析了技术难点并给出了解决方案, 讨论了瞬态对消电流的生成时刻对强度的影响规律.经实测与分析, 该系统对消电流脉宽为5 ns, 幅度控制步进为122 nA, 幅度调节范围为135---360 μA, 成功实现了对近场强散射的抑制. 该系统完全可以满足尾流激光雷达大动态探测的需要.     

基于Kinect深度数据的移动机器人障碍检测方法研究

（北方工业大学,机械与材料工程学院,北京,100144） 摘要： 未知室内环境中的障碍检测是室内移动机器人领域的热点问题。在低成本条件下为更加准确的对环境中的障碍进行检测,提出一种基于低成本Kinect传感器点云数据进行环境障碍检测的有效方法。首先通过Kinect三维点云数据,对点云数据进行去燥处理,并进行三维数据到二维平面的投影的转换并通过DBSCAN聚类算法对投影的二维点云数据进行聚类分析。通过设置相邻顶点间最大距离阈值对convex-hull凸包算法进行改进,试验结果表明改进的凸包算法能够对障碍进行有效识别。该方法在Matlab中进行了方法验证,并在P3-DX移动机器人平台上进行了试验验证,结果表明该方法能够有效对环境中的障碍进行有效识别。     

激光雷达距离像的实时边缘检测

针对激光雷达距离像边缘检测精度低、抗噪性能差和需要人为设定阈值的问题,提出一种改进Sobel算子的边缘检测算法,算法通过增加梯度检测方向提高算法的边缘定位精度,采用中值滤波计算局部距离像边缘阈值,在实现自适应阈值的Sobel边缘检测的同时增强算法的抗噪性能,同时采用FPGA硬件加速,实现算法实时性边缘检测.此外,设计激...     

基于核密度估计的城市动态密集场景激光雷达定位

城市环境中的精确定位是自动驾驶领域的重点和难点,现有的激光雷达定位算法虽然能够在多数情况下保持较高的精度,但在一些比较复杂的城市动态场景中仍存在问题。针对这类场景中遮挡导致的全球定位系统定位精度下降,以及运动目标和环境变化导致的有效点云特征减少的问题,提出一个新的概率定位框架;该框架使用核密度估计的方法对改进后的多层次随机采样一致性算法和直方图滤波算法进行融合,以有效克服多层次随机采样一致性算法在部分场景中的定位波动问题,以及直方图滤波算法在位姿误差较大时的效率低下和局部最优问题。结果表明:所提框架在保证定位精度的前提下,提升了对动态密集场景的适用性,能够在现有算法容易出错的场景中实现更加稳定精确的定位,并能够容忍更大的初始位姿误差。     

基于红外与激光雷达融合的鸟瞰图空间三维目标检测算法

结合MEMS激光雷达和红外相机的优势,设计了一种简单轻量、易于扩展、易于部署的可分离融合感知系统实现三维目标检测任务,将激光雷达和红外相机分别设置成独立的分支,两者不仅能独立工作也能融合工作,提升了模型的部署能力。模型使用鸟瞰图空间作为两种不同模态的统一表示,相机分支和雷达分支分别将二维空间和三维空间统一到鸟瞰图空间下,融合分支使用门控注意力融合机制将来自不同分支的特征进行融合。通过实际场景测试验证了算法的有效性。     

荧光米激光雷达气溶胶团边界检测

有机气溶胶具有荧光效应,能在特定波长激光的激发下产生荧光,针对此类荧光气溶胶团,提出了一种基于水平探测荧光-米激光雷达的径向边界检测算法。该算法利用荧光和米双通道的回波信号构造一个去除大气影响的函数,并采用截距法检测荧光气溶胶团的突变特征信号以确定边界。数值仿真表明,该算法在不同能见度和信噪比下对单个和两个荧光气溶胶团的径向边界检测都具有较高的精确度和稳定性。利用该算法检测了荧光-米激光雷达对单个或两个荧光气溶胶团的径向边界,结果表明该算法有效提高了边界检测的准确度和稳定性,且具有检测单个荧光气溶胶团边界的时效性。     

Calibration of a multiple axes 3-D laser scanning system consisting of robot, portable laser scanner and turntable

A multiple axes 3-D laser scanning system consisting of a portable 3-D laser scanner, a industrial robot and a turntable is demonstrated. By using a criterion sphere, a robot tool center point (TCP) calibration approach is proposed to calibrate the relation between the laser 3-D scanner and the robot end-effector. In this approach, two different translational motions of robot are first made to determine the rotation part, and then at least three different rotational motions are made to determine the translation part. Meanwhile, by using the criterion sphere, a turntable approach is proposed to calibrate the pose of the turntable relative to the robot. In this approach, several rotational angles of turntable and two different heights of the sphere are made to determine the rotational axis of turntable. Experiment is performed on a portable laser scanner mounted on an industrial robot ABB IRB4400 with a turntable. The experiment results show that the two proposed calibration algorithms are stable and flexible. The application of 3-D measurement is also given to demonstrate the effectiveness and stability of the multiple axes 3-D laser scanning system.     

Fusion of 3D laser scanner and depth images for obstacle recognition in mobile applications

The problem of obstacle detection and recognition or, generally, scene mapping is one of the most investigated problems in computer vision, especially in mobile applications. In this paper a fused optical system using depth information with color images gathered from the Microsoft Kinect sensor and 3D laser range scanner data is proposed for obstacle detection and ground estimation in real-time mobile systems. The algorithm consists of feature extraction in the laser range images, processing of the depth information from the Kinect sensor, fusion of the sensor information, and classification of the data into two separate categories: road and obstacle. Exemplary results are presented and it is shown that fusion of information gathered from different sources increases the effectiveness of the obstacle detection in different scenarios, and it can be used successfully for road surface mapping.     

一种基于单目视觉的移动机器人室内导航方法

针对室内导航的环境特点,提出了一种简单快速的、以踢脚线为参考目标的移动机器人室内导航方法。该方法从图像中提取踢脚线作为参考直线,通过两条直线在图像中的成像特征,提取角度和横向偏离距离作为移动机器人的状态控制输入,从而实现移动机器人的横向运动控制。该方法无需进行摄像机的外部参数标定,大大简化了计算过程,提高了视觉导航的实时性。     

一种8行任意扫描的电光扫瞄器

 针对激光的快速智能扫描,综合利用晶体的双折射效应和电光效应,提出一种电控集成8行任意扫瞄的高速光扫描方案。主要由三级数字电光偏转器和8×1的周期性极化电光棱镜组构成,其中3个电光快门和3块双折射晶体构成三级数字偏转器,通过半波电压的控制实现行位置的转换,一定数目的周期性极化电光棱镜级联组成单行偏转器,通过控制电压进行单行扫描,根据电场施加方式可实现数字型或者连续型扫描。利用梯形结构的电光棱镜组设计了最大电压为5.822 kV时,扫描视场为17.256°的可通过联机控制进行任意行扫描的高速激光扫描器。     

二维定心激光扫描器及其摆角测量系统的研制

简要介绍了一种二维定心偏转激光扫描器的工作原理和结构设计。对二维摆角的两种不同测量方式的优劣进行了比较,并详细介绍了采用光电位置传感器(PSD)实现摆角测量的系统,包括它的测量原理、光学系统构造和PSD后续信号处理电路。结果表明,所研制的二维定心激光扫描器摆角测量系统可以实现±7.5°的二维摆角和30°圆锥角的大范围扫描,其重复精度为0 05°,分辨率为0 01°。具有快速灵巧、实时性强、工作稳定、抗环境干扰能力强等优点。     

Calibration procedure for a laser triangulation scanner with uncertainty evaluation

Most of low cost 3D scanning devices that are nowadays available on the market are sold without a user calibration procedure to correct measurement errors related to changes in environmental conditions. In addition, there is no specific international standard defining a procedure to check the performance of a 3D scanner along time. This paper aims at detailing a thorough methodology to calibrate a 3D scanner and assess its measurement uncertainty. The proposed procedure is based on the use of a reference ball plate and applied to a triangulation laser scanner. Experimental results show that the metrological performance of the instrument can be greatly improved by the application of the calibration procedure that corrects systematic errors and reduces the device's measurement uncertainty.     

Development of a Two-Dimensional Bar-Code Detection System Using Multi Laser Diodes with Time-Sharing Light Emission Operation

A new high-speed two-dimensional bar-code detection system using multi laser diodes with time-sharing light emission operation has been developed. A bias current allowing the laser diode to improve the light output rise time was optimized to slightly below the threshold of the diode, so that channel cross-talk among three-line bar-code signals caused by the bias light can be kept small and a high-speed pulse modulation operation can be achieved. The prototype system for a three-line bar code with spatially overlapping laser-diode heads has achieved an effective scanning speed two and nine tenths times that of conventional scanners. It is estimated that the number of time-sharing light emission laser diodes can be increased to at least four when the current photodetection amplifier with a bandwidth of 6.4 MHz is used. This number can be improved to six by using photodetection amplifiers with double the bandwidth of the present ones.     

Study on fast linear scanning for a new laser scanner

In the field of lidar system design, there is a need for laser scanners that offer fast linear scanning, are small size and have small a rotational inertia moment. Currently, laser scanners do not meet the above needs. A new laser scanner based on two amplified piezoelectric actuators is designed in this paper. The laser scanner has small size, high mechanical resonance frequencies and a small rotational inertia moment. The size of the mirror is 20 mm×15 mm. To achieve fast linear scanning performance, an open-loop controller is designed to compensate the hysteresis behavior and to restrain oscillations that are caused by the mechanical resonances of the scanner's mechanical structure. By comparing measured scanning waveforms, nonlinearities and scan line images between the uncontrolled and controlled scanner, it was found that the scanning linearity of linear scanning was improved The open-loop controlled laser scanner realizes linear scanning at 250 Hz with optical scan angle of ±12 mrad.     

Large depth-of-view portable three-dimensional laser scanner and its segmental calibration for robot vision

A portable 3D laser scanning system has been designed and built for robot vision. By tilting the charge coupled device (CCD) plane of portable 3D scanning system according to the Scheimpflug condition, the depth-of-view is successfully extended from less than 40 to 100 mm. Based on the tilted camera model, the traditional two-step camera calibration method is modified by introducing the angle factor. Meanwhile, a novel segmental calibration approach, i.e., dividing the whole work range into two parts and calibrating, respectively, with corresponding system parameters, is proposed to effectively improve the measurement accuracy of the large depth-of-view 3D laser scanner. In the process of 3D reconstruction, different calibration parameters are used to transform the 2D coordinates into 3D coordinates according to the different positions of the image in the CCD plane, and the measurement accuracy of is obtained experimentally. Finally, the experiment of scanning a lamina by the large depth-of-view portable 3D laser scanner used by an industrial robot IRB 4400 is also employed to demonstrate the effectiveness and high measurement accuracy of our scanning system.     

生物芯片扫描仪研究进展

介绍了生物芯片及其检测、扫描的基本原理。详细讨论了在生物芯片扫描仪中的关键技术及国内外的研究现状和目前存在的技术难点以及最新发展趋势和研究热点。着重分析了共聚焦光路与非共聚焦光路在生物芯片扫描仪中的应用特点,以及CVR技术指标。最后提出了生物芯片扫描仪的未来研究重点以及发展方向。