Robust DOA estimation and target docking for mobile robots

Direction of arrival (DOA) guided automated target acquisition and docking system is proposed for mobile robots employing the dual-directional antenna system. The dual-directional antenna estimates the DOA of the signal of interest using the ratio of the signal strengths between two adjacent antennas. In practice, DOA estimation poses a significant technical challenge, since the RF signal is easily distorted by the environmental conditions. Therefore, the robot often loses its way in an electromagnetically disturbed environment. To cope with this problem, a robust DOA estimation algorithm is developed based on Kalman filtering. This algorithm allows the robot to reduce the potential error in the estimated DOA, and adjust the robot’s heading to the target transponder without needing to know the positions of current and previous measurements in a global coordinate system. The simulation and experiment results clearly demonstrate that the mobile robot equipped with the developed system is able to dock to a target transponder in an indoor environment partially occupied by obstacles.     

Indoor robot localization based on single RFID tag

With the mature of the RFID technology and the wide use of the Internet of Things technology, it is a new research hotspot that RFID technology was applied to robot localization and navigation. RFID tags have the characteristic of storing information, long reading distance and using conveniently. A novel robot localization method combining RFID with laser data is proposed in this paper. When the robot detects an RFID tag, RFID antenna angle probability model is determined based on the fuzzy reasoning algorithm. Then the Bayes rule is used to estimate the direction of the robot. Finally, the robot global localization is realized by fusion of the laser ranging data. The experimental results showed that the precision of the positioning based on single RFID tag is enhanced greatly by combining laser detecting data.     

Developing a vision-based auto-recharging system for mobile robots

This article describes a vision-based auto-recharging system that guides a mobile robot moving toward a docking station. The system contains a docking station and a mobile robot. The docking station contains a docking structure, a control device, a charger, a safety detection device, and a wireless RF interface. The mobile robot contains a power detection module (voltage and current), an auto-switch, a wireless RF interface, a controller, and a camera. The controller of the power detection module is a Holtek chip. The docking structure is designed with one active degree of freedom and two passive degrees of freedom. For image processing, the mobile robot uses a webcam to capture a real-time image. The image signal is transmitted to the controller of the mobile robot via a USB interface. We use an Otsu algorithm to calculate the distance and orientation of the docking station from the mobile robot. In the experiment, the proposed algorithm guided the mobile robot to the docking station.     

一种基于图像的移动机器人泊位方法

提出一种新的移动机器人泊位方法. 该方法采用一幅预先采集的参考图像定义机器人的期望泊位状 态（期望的位置和方向）,利用尺度不变特征变换（SIFT）算法和基于双向BBF 的特征匹配算法实现泊位站当前图 像与参考图像之间的匹配以获取视觉反馈信息,基于极点伺服策略根据参考图像准直机器人,采用质心跟踪法防止 目标图像出视场,采用RANSAC 算法求解当前图像与参考图像间的仿射变换,利用一个末段控制策略实现精确泊 位．本文方法不需要环境模型或人工标记．室内环境下的实验结果证实了该方法的有效性．     

电磁矢量互质阵中基于降维Capon的DOA和极化估计算法

将传统电磁矢量均匀阵列推广为电磁矢量互质阵列,突破了阵元间距不大于半波长的限制。提出了电磁矢量互质阵列中基于降维Capon的波达方向（Direction of arrival,DOA）和极化联合估计算法。该算法无需假设已知极化信息,且只需一维搜索,避免了多维搜索,可实现DOA和极化参数自动配对;与相同阵元数的均匀阵列相比,明显提高了角度估计性能,并拓展了天线孔径,具有相对较高的自由度,且降低了运算复杂度。相同阵列及参数条件下,本文算法的角度估计性能优于ESPRIT算法和三线性分解算法。     

机器人在已知三维自然环境中的路径规划算法

研究了移动机器人在三维环境的路径规划问题,针对该问题中存在环境适应性和全局性差的不足,对人工势场法进行改进,提出了一种新的路径规划的算法.该算法首先对已知的三维自然环境进行栅格化,建立栅格运行费用的评估模型,计算每个栅格的运行费用;然后依据栅格的运行费用建立斥力场,以目标点为中心的建立引力场,同时提出解决局部最小值的问题的方法;最后将两者合力的方向作为移动机器人在该点的路径走向,规划出一条从起始点到目标点的运行费用较低的路径.仿真实验结果表明,该算法能有效降低运行费用,适应性和全局性好,适合应用于移动机器人在三维自然环境中的路径规划.     

基于RFID技术的室内机器人定位方法的研究

近年来,随着RFID技术的日益成熟,它在机器人领域的应用变得越来越广泛而深入。文章首先分析了RFID技术在室内环境下应用于移动机器人自我定位的可行性,然后描述了使用蒙特卡罗概率统计模型对机器人附近的RFID标签进行方位定位的过程,并且阐述了利用在此过程中获得的数据对自身或者特定物在特定环境下进行方位定位的方法,最后文章分析了此技术在某些特定场合进行应用推广的可行性和前景。     

改进动态规划算法的移动机器人路径规划

针对静态栅格环境下的移动机器人全局路径规划问题,通过分析移动机器人到达目标的搜索方向和路径变化的动态特征,分别建立下降路径搜索动态规划模型和上升路径搜索动态规划模型,并依据整列元素路径值变化特点设计了两种模型交互使用的改进动态规划算法。仿真实验结果表明算法具有较好的路径规划效率,可以同时完成多个目标路径规划,且覆盖率越大的环境求解越快速。实验也表明改进动态规划算法同蚁群算法对比能够更快速有效地给出移动机器人较优通行路径。     

一种改进的基于定向天线的移动传感器网络定位算法

针对在无线传感器网络定位中,由于全向天线信号受环境影响而造成定位误差较大的问题,提出了一种改进的基于定向天线的移动无线传感器网络定位算法(DADLP),使用一个带有定向天线的移动锚节点广播位置信息,未知节点接收到信号后,将接收功率平均分为若干等级,缩小定位估计区域.仿真结果表明DADLP算法相对于Ssu、BLI、GGDI和RROI移动锚节点算法提高了定位精度,并且在非规则环境下有更低的平均定位误差.     

一种新型电网仓库物品管理算法

射频识别标签具有体积小,无需电源等特点;它在电网设备管理中具有重大作用;但现有的RFID定位系统存在需要专用设备,仅能够实现二维平面定位以及移动定位精度不高,可扩展性低等缺点;在此利用商用机器人和RFID设备提出了一个移动RF机器人三维空间定位系统;具体地说,通过不同的相位构造的三元组,可以得到不同精度的目标标签候选位置;然后,通过对偏差较小的定位结果赋予较大的权重,最终获得精确度较高的定位结果;此外通过利用目标标签与天线轨迹之间的几何关系,可以将该方法扩展到三维空间;通过实验结果表明,所提出的系统在二维和三维定位中存在较小的误差,大约为12cm。     

新的室内移动机器人自定位方法

针对现有室内移动机器人自定位方法中存在的定位精度不高,随时间积累定位误差增大,复杂室内环境下信号存在多径效应和非视距效应等问题,提出了一种基于蒙特卡罗定位(MCL)的新的移动机器人自定位方法。首先,通过分析基于无线射频识别(RFID)技术的移动机器人自定位系统,建立机器人运动模型;然后,通过分析基于接收信号强度指示(RSSI)的移动机器人自定位系统,提出机器人移动过程的观测模型;最后,针对粒子滤波定位执行效率不高的问题,提出粒子剔除策略和依据粒子方位赋予粒子权值策略,提高系统的定位精度和执行效率。仿真实验表明,机器人在移动过程中的自定位误差在X轴和Y轴方向上为3 cm,传统定位算法误差为6cm,新算法定位精度提高近1倍,且算法具有很好的鲁棒性。     

结合历史运动状态的机器人高效沿墙算法研究

针对目前室内移动机器人沿墙走算法过于复杂、路径易重复、不能完全遍历、效率低等问题, 采用室内未知环境下结合历史状态的机器人沿墙高效遍历研究来解决这些问题. 该算法由移动机器人的上一个周期历史环境运动状态(分8类)、当前环境运动状态(分8类)和旋向信息(分2类)建立运动规则库, 沿墙行走时移动机器人时时采集这三类信息(上一个周期历史环境运动状态、当前环境运动状态和旋向信息)决定移动机器人当前的运动方向, 如此循环直到完成指定的沿墙任务. 最后对该算法进行了仿真与实际实验, 实验结果证明该算法可以在不同的、复杂的环境中高效、快速地完成沿墙走的任务, 并且对室内未知环境有很好的适应性.     

一种新的基于RFID的室内移动机器人自定位方法研究

针对室内移动机器人自定位算法定位精度不高、定位误差存在波动的问题,提出了一种RTFL(RFID tag floor based localization)定位算法与RSSI定位算法相结合的室内移动机器人自定位方法。由RTFL定位算法给定机器人位置估算初值和机器人所在的范围,然后通过基于RSSI的机器人自定位系统进行机器人位置的进一步精确定位。求解过程中,通过遗传算法求解极大似然方程组,并且提出了染色体的筛选和剔除策略。仿真实验结果表明：该方法在有效的时间内完成定位,平均定位误差为0.1572m,与传统的改进方法0.33214m的定位误差相比,降低了近一倍。并且新方法受环境影响较小,鲁棒性较好,能够很好的满足室内移动机器人的定位要求。     

Fuzzy Motion Planning of Mobile Robots in Unknown Environments

A fuzzy algorithm is proposed to navigate a mobile robot from a given initial configuration to a desired final configuration in an unknown environment filled with obstacles. The mobile robot is equipped with an electronic compass and two optical encoders for dead-reckoning, and two ultrasonic modules for self-localization and environment recognition. From the readings of sensors at every sampling instant, the proposed fuzzy algorithm will determine the priorities of thirteen possible heading directions. Then the robot is driven to an intermediate configuration along the heading direction that has the highest priority. The navigation procedure will be iterated until a collision-free path between the initial and the final configurations is found. To show the feasibility of the proposed method, in addition to computer simulation, experimental results will be also given.     

Velocity planning for a mobile robot to track a moving target — a potential field approach

Potential field method has been widely used for mobile robot path planning, but mostly in a static environment where the target and the obstacles are stationary. The path planning result is normally the direction of the robot motion. In this paper, the potential field method is applied for both path and speed planning, or the velocity planning, for a mobile robot in a dynamic environment where the target and the obstacles are moving. The robot’s planned velocity is determined by relative velocities as well as relative positions among robot, obstacles and targets. The implementation factors such as maximum linear and angular speed of the robot are also considered. The proposed approach guarantees that the robot tracks the moving target while avoiding moving obstacles. Simulation studies are provided to verify the effectiveness of the proposed approach.     

Robot Localization Using the Phase of Passive UHF-RFID Signals Under Uncertain Tag Coordinates

An indoor global localization problem for a mobile robot based on Radio Frequency IDentification (RFID) is considered. The localization system consists of a reader installed on the robot which measures the phase of UHF-RFID signals coming from a set of passive tags deployed on the ceiling of the environment. Assuming only an approximate information is available at the beginning on the position of the tags, this paper presents an algorithm, based on a Multi-Hypothesis Extended Kalman Filter, which improves the initial estimate on the tag coordinates while simultaneously localizing the robot. Simulative and experimental results are reported to illustrate the effectiveness of the proposed approach.     

基于视觉与RFID的机器人自定位抓取算法

为实现机器人灵活的自定位,并使其准确地抓取物体,提出一种基于视觉与无线射频识别(RFID)技术的机器人自定位抓取算法。构建网格化环境,利用RFID技术确定机器人的初始位置、行进路线和方向,使用视觉系统获取物体的空间坐标,将其转换到手臂坐标系,采用改进的D-H模型对手臂进行建模,并给出机械臂逆解抓取算法。实验结果表明,该算法使得机器人定位的成功率达到76.7%,抓取成功率高达90%。     

未知环境下移动机器人实时路径规划

针对在未知环境下实现移动机器人实时的路径规划问题,提出了一种将快速扩展随机树（RRT）算法与视野域自适应的滚动窗口相结合的路径规划算法。该方法实时获取滚动窗口内的局部环境信息,根据环境的变化,滚动窗口视野域进行自适应调整,通过分析滚动窗口内传感器获取的信息,结合改进后的RRT算法筛选出可行的路径,控制移动机器人到达子目标点,在此过程中动态监测规划好的路径,确保路径合理,并重复上述过程,直至到达目标区域。实验对比分析表明,该方法能实时并有效实现未知环境下移动机器人的路径规划。     

A Smooth Path Tracking Algorithm for Wheeled Mobile Robots with Dynamic Constraints

In order to avoid wheel slippage or mechanical damage during the mobile robot navigation, it is necessary tosmoothly change driving velocity or direction of the mobile robot. This means that dynamic constraints of the mobile robotshould be considered in the design of path tracking algorithm. In the study, a path tracking problem is formulated asfollowing a virtual target vehicle which is assumed to move exactly along the path with specified velocity. The drivingvelocity control law is designed basing on bang-bang control considering the acceleration bounds of driving wheels. Thesteering control law is designed by combining the bang-bang control with an intermediate path called the landing curve whichguides the robot to smoothly land on the virtual target's tangential line. The curvature and convergence analyses providesufficient stability conditions for the proposed path tracking controller. A series of path tracking simulations and experimentsconducted for a two-wheel driven mobile robot show the validity of the proposed algorithm.     

OFDM超分辨率联合TOA/AOA定位

对无线信号到达时间（TOA）和到达角度（AOA）的精确估计是室内无线定位的关键。正交频分复用（OFDM）是适合多径衰落环境的一种高速传输技术。提出一种联合TOA和DOA的二维定位方法用于OFDM信号定位。算法首先通过信道估计得到信道的频率响应（CFR）,对CFR采用超分辨率算法估计信道时延。首径（first arrival path,FAP）的时延估计就是接收信号的TOA估计。将天线阵列接收信号通过DFT变换到频域,利用同样的算法估计信号各径的AOA/DOA。最后联合TOA和AOA在二维平面上确定目标位置。由于信号是多径、多载波信号,对各载波的DOA/AOA估计在载波间进行处理,再结合各径脉冲响应的幅值,选出属于首径的DOA/AOA估计。在多径环境下仿真表明算法有效且定位精度能够满足实际需要,尤其适合环境中只有一个基站或接入点的情况。