Handling large-scale node failures in mobile sensor/robot networks

In Wireless Sensor Networks (WSNs), maintaining connectivity with the sink node is a crucial issue to collect data from sensors without any interruption. While sensors are typically deployed in abundance to tolerate possible node failures, a large number of simultaneous node failures within the same region may result in partitioning the network which may disrupt the network operation significantly. Given that WSNs are deployed in inhospitable environments, such node failures are very likely due to storms, fires, floods, etc. The self-recovery of the network from these large-scale node failures is challenging since the nodes will not have any information about the location and span of the damage. In this paper, we first present a distributed partition detection algorithm which quickly makes the sensors aware of the partitioning in the network. This process is led by the sensors whose upstream nodes fail due to damages. Upon partition detection, sensors federate the partitions and restore data communication by utilizing the former routing information stored at each sensor to the sink node and exploiting sensor mobility. Specifically, the locations of failed sensors on former routes are used to assess the span of the damage and some of the sensors are relocated to such locations to re-establish the routes with the sink node. Relocation on such former routes is performed in such a way that the movement overhead on sensors is also minimized. Our proposed approach solely depends on the local information to ensure autonomicity, timeliness and scalability. The effectiveness of the proposed federation approach is validated through realistic simulation experiments and has been shown to provide the mentioned features.     

Sub-optimality analysis of mobile robot rolling path planning

Rolling planning is an efficient method for path planning in uncertain environment. In this paper, the general principle and algorithm of mobile robot path planning based on rolling windows are studied. The sub-optimality of rolling path planning is analyzed in details and explained with a concrete example.     

Lattice independent component analysis for appearance-based mobile robot localization

This paper introduces an approach to appearance-based mobile robot localization using a new approach to dimensional reduction based on the notion of Lattice Independence called Lattice Independent Component Analysis (LICA). Any algorithm that can select a set of Strong Lattice Independent (SLI) vectors from the data can be applied inside LICA, this paper applies a specific Endmember Induction Algorithm (EIA) developed by our research group. The fact that SLI vectors are Affine Independent allows the coupling of non-linear Lattice Associative Memories (LAM) and linear unmixing for data exploration and dimensionality reduction. To perform an appearance-based mobile robot visual localization, images from the on-board camera robot are transformed into low dimension feature vector representations for classification. For validation, we compare LICA against several Independent Component Analysis (ICA) approaches over a collection of recorded image sequences taken from the robot following some predefined paths. Results show that LICA improves most of the ICA approaches, and it is only slightly improved by the Molgedey and Schouster ICA in some data instances.     

Generation of workpiece orientations for machining using a rule-based system

This paper deals with the automatic generation of workpiece orientations on a machine for machining operations. A system capable of this has a wide spectrum of applications in many areas of manufacturing planning and is essential to the development of dynamic process planning systems. However, such a system requires the ability to reason about geometrical and spatial relationships, a topic of great difficulty for automatic reasoning. A study of the problem characteristics is made and its results are implemented in a rule-based system. This system, when given a workpiece along with operation instructions and machine specifications is capable of generating a good orientation for the workpiece. The functioning of the system is demonstrated by an example.     

移动机器人自适应行为选择的混沌特性分析

针对移动机器人运行环境的复杂非线性特性,提出一种将重构相空间理论应用到移动机器人自适应行为选择中的混沌非线性分析方法。在所采集的一维自适应行为动作选择随机序列的基础上,重构时间序列的相空间,并计算相空间的嵌入维数、混沌吸引子和最大Lyapunov指数。计算结果表明,当运行环境中障碍物的分布密度较大时,移动机器人的自适应行为选择规律呈现混沌特性。这为结合混沌理论,给移动机器人的自适应行为选择提供更精确的控制,提供了理论基础。     

一种全方位移动机器人

研制了一种新型全方位轮式移动机器人,该机器人主要由三个特殊的轮式结构—MY轮组成.MY轮利用球体的运动原理,将球体分为接触区和非接触区,利用两球体的接触区与非接触区的相互补充实现了万向轮的功能.两部分球体的被动旋转轴成45度交叉布置,实现了与地面的连续接触;同时该结构也增加了万向轮的强度.对轮式移动机构的运动学分析和仿真证明了该机构能够实现全方位移动.机器人的运动实验也证明了该万向轮机构不仅能够实现全方位运动,而且还能够跨越障碍物.     

Hard material small-batch industrial machining robot

Hard materials can be cost effectively machined with standard industrial robots by enhancing current state-of-the-art technologies. It is demonstrated that even hard metals with specific robotics-optimised novel hard-metal tools can be machined by standard industrial robots with an improved position-control approach and enhanced compliance-control functions. It also shows that the novel strategies to compensate for elastic robot errors, based on models and advanced control, as well as the utilisation of new affordable sensors and human-machine interfaces, can considerably improve the robot performance and applicability of robots in machining tasks. In conjunction with the development of safe robots for human-robot collaboration and cooperation, the results of this paper provide a solid background for establishing industrial robots for industrial-machining applications in both small- and medium-size enterprises and large industry. The planned short-term and long-term exploitation of the results should significantly increase the future robot usage in the machining operations.     

Investigation of automatic workpiece selection for machining from bar stock inventories

Given a feature-based CAD model of a part's geometry, the problem is to select the shape, size and cut-off length of bar stock from which the part can be made. The standard stock shapes and sizes available in any shop vary, so the task is to select the best-suited stock geometry from the available inventory. The requirements of a system to perform this task are presented along with several alternative methods: shape coding, shrinking bounding box, silhouette projection, extremal point network, principal machining directions, and face extension. None of these methods was found to be completely satisfactory, so a hybrid method was synthesized and implemented. A coding scheme is used to select the workpiece shape, based on primary features and their relationships. Prismatic workpieces are selected by a silhouette projection method using quadtree-based matching. Pure rotational parts are distinguished from those with major axes deviations by a face extension method that looks for intersections with a candidate rotational shape. Once the overall part shape has been determined, it is matched with available workpiece shapes. The workpiece is then sized using a version of the bounding box method.     

Measurement and analysis on large-scale offline mobile app dissemination over device-to-device sharing in mobile social networks

Recently, the issue of offloading cellular data while reducing the duplicated cellular transmission has gained more and more attention. Several studies have shown that sharing contents through Device-to-Device (D2D) to offload traffic to local connections nearby can offer better performance for mobile users. Nevertheless, most existing proposals are somewhat confined to small-scale data sets or limited feature dimensions, relied on unconsolidated hypotheses and measurements of data sets. This paper presents a prior work of large-scale measurements on 3.56 TBytes of real-world data sets, which contain D2D content sharing activities from a popular D2D sharing application (APP). We conduct a comprehensive analysis of multi-dimensional features, including time series, structural properties, meeting dynamics, location relationship, and propagation tree. Our analysis reveals that (i) D2D sharing makes the hops between users shorter (in 3 or 4 degrees), (ii) the maximum spreading distance of content dissemination is 27 hops, (iii) we provide a new evidence of log-normal distribution of all user encounters (named meeting dynamics in this paper) based the fit of inter-TX time, Inter-Content Time (ICT) and Contact Time, (iv) online factor (O) and social factor (S) demonstrate the largest positive correlation and indicate that the two factors have high linear correlation. Finally, we analyze the correlations among all the impact factors by Pearson coefficient, principal component analysis, and latent semantic analysis, respectively. Results reveal that online factor (O) and social factor (S) have a high correlation, especially both of them have a great effect on D2D sharing activities.

     

Stability analysis of the internal dynamics of a wheeled mobile robot

The stability of the internal dynamics of a wheeled mobile robot is analyzed. It is shown that the wheeled mobile robot exhibits unstable internal dynamics when moving backwards. Most control methods of wheeled mobile robots are designed based on input-output relations. Since the internal dynamics are not represented in input-output relations, stability properties of the internal dynamics are generally neglected. Nevertheless, the internal dynamics do affect the behavior of mobile robots. Taking the look-ahead control method as an example, it is shown that, by using a novel Liapunov function, the internal dynamics of a two-wheel differential-drive mobile robot are unstable when it is commanded to move backwards. Both simulation and experimental results are provided to verify the analysis. ©1997 John Wiley & Sons, Inc.     

Empirical learning in mobile robot navigation

The purpose of this study is to improve the locomotion performance for autonomous mobile robots in outdoor environments. In this paper improvement of an environment model is called empirical locomotion performance leaming. A system avoids wasting time of observations and actions by analyzing data from the last run. We propose a method of empirical learning. The method is expressed by rewriting the rules on the trajectory data. Brief route information for navigating a robot is represented with motion directions at intersections and metric distances between intersections. The behavior of our robot is based on a locomotion strategy 'sign pattern-based stereotyped motion'. The behaviors are implemented on our mobile robot HARUNOBU-4 and tested at our university campus. Experimental results show a robustness of our proposed behaviors under dynamic environments with existing obstacles. Furthermore, they showed that our proposed rewriting rules improved the locomotion performance. In particular, searching time was shortened by 87% (from 453 to 61 s) and the travel distance was shortened by 10% (from 173.8 to 157.5 m).     

移动机器人导航控制研究的重要进展—-评专著《未知环境中移动机器人导航控制理论与方法》

蔡自兴、贺汉根、陈虹等教授的新著《未知环境中移动机器人导航控制理论与方法》已在科学出版社问世,成为《21世纪先进制造技术丛书》的一枝新秀,作为该丛书的主编,我深感荣幸。专著是三位教授和研究组成员,在智能机器人领域多年来辛苦耕耘,取得丰硕成果的基础上,精心凝练写成的,高屋建瓴,叶茂根深。它的出版值得大家庆贺。     

Method of decomposition in mobile robot control

A complex of the problems of controlling the mobile wheel robots was solved in various formulations. A methodology of designing the generator of realizable driving actions was developed, that is, the question of feasibility analysis of the given trajectory stands no longer. Developed was a two-level decomposition procedure for designing a control system of the mobile two-wheel robot driving it to the desired trajectory and then along it with the prescribed velocity. Forced equation relating the linear and angular deviations enabled reduction of the design problem to the elementary subproblems where the dimensions of the state vectors and controls coincide. The sliding-mode observers are used for informational support of the basic control laws, which enables one to establish the current estimates of the functional components and exogenous disturbances and simplifies substantially the computer-aided realization of the control algorithms. The results of modeling corroborated efficiency of the developed algorithms.     

An autonomous vision-based mobile robot

This paper describes the theoretical development and experimental implementation of a complete navigation procedure for use in an autonomous mobile robot for structured environments. Estimates of the vehicle's position and orientation are based on the rapid observation of visual cues located at discrete positions within the environment. The extended Kalman filter is used to combine these visual observations with sensed wheel rotations to produce optimal estimates continuously. The complete estimation procedure, as well as the control algorithm, developed are time independent. A naturally suitable quantity involving wheel rotations is used as the independent variable. One consequence of this choice is that the vehicle speed can be specified independently of the estimation and control algorithms. Reference paths are “taught” by manually leading the vehicle through the desired path. Estimates produced by the extended Kalman filter during this teaching session are then used to represent the geometry of the path. The tracking of taught reference paths is accomplished by controlling the position and orientation of the vehicle relative to the reference path. Time-independence path tracking has necessitated the development of a novel, geometry-based means for advancing along the reference path     

An autonomous fuzzy mobile robot

Autonomous mobile robots should have the capability of recognizing their environments and manoeuvring through those environments on the basis of their own judgement. Fuzzy control is suitable for autonomous mobile robot control where the amount of information to be handled is limited as much as possible and the processing is simple. Autonomous mobile control of a robot is derived from two kinds of controls: for obstacle avoidance and for guidance following an appropriate path to a destination point. Fuzzy control of a robot for obstacle avoidance based on finding permissible passageways using the edges between the floor and the wall or obstacles obtained by processing the image from a CCD camera in front of the robot is developed. Furthermore, guidance control of the robot over paths that are specified in terms of maps may be developed by a process that treats a wrong path as a virtual obstacle on the screen, and the robot advances in the designated direction when it reaches intersections. An autonomous fuzzy robot based on the above method is fabricated as a trial and its usefulness is demonstrated.     

动态未知环境中移动机器人的滚动路径规划及安全性分析

借鉴预测控制滚动优化原理,研究了全局环境未知且存在动态障碍物情况下的机器人路径规划问题.提出的基于滚动窗口的移动机器人路径规划方法充分利用机器人实时测得的局部环境信息,以滚动方式进行在线规划,合理结合了优化与反馈,对动态环境具有良好的适应性.还对规划算法的安全性进行了分析.     

Four-legged intelligent mobile autonomous robot

This paper presents the design and development of a four-legged mobile robot with intelligent sensing and decision-making capabilities. Multiple sensors with embedded knowledge bases and learning capabilities are used in a novel approach towards environmental perception and reaction. These sensors continuously monitor the environment as well as their own operating parameters. Priority is given to any one or a group of sensors based on prevailing environmental conditions. Intelligent sensing is shown to be the key towards a high degree of autonomy for a mobile robot. Nicknamed Flimar, this robot has the ability to function at varying degrees of intelligence made possible by an object-oriented architecture with embedded intelligence at various levels. This architecture is shown to be conducive towards incremental learning. Each of the four legs has three degrees of freedom, i.e. Flimar has a total of 12 motors on its four legs. Flimar can walk and turn without dragging or skidding, and also turns about its center of gravity with a zero radius. Flimar responds to light, sound and touch in different ways, based on prevailing environmental conditions. The overall goal of the paper is to present a novel walking principle and control architecture for a walking robot.     

移动机器人运动轨迹控制系统

以移动机器人的轨迹控制为主要目标,研究了线性控制算法在机器人轨迹控制中的具体实现方法.论证了其可行性,分析了算法的稳定性约束条件,通过仿真分析了控制参数对运动轨迹的影响.将该算法应用到实际的机器人控制中,设计出了基于陀螺仪和光电编码器的温室移动机器人控制系统.