Instance invariant visual servoing framework for part‐aware autonomous vehicle inspection using MAVs

Visual servoing approaches navigate a robot to the desired pose with respect to a given object using image measurements. As a result, these approaches have several applications in manipulation, navigation and inspection. However, existing visual servoing approaches are instance specific, that is, they control camera motion between two views of the same object. In this paper, we present a framework for visual servoing to a novel object instance. We further employ our framework for the autonomous inspection of vehicles using Micro Aerial Vehicles (MAVs), which is vital for day‐to‐day maintenance, damage assessment, and merchandising a vehicle. This visual inspection task comprises the MAV visiting the essential parts of the vehicle, for example, wheels, lights, and so forth, to get a closer look at the damages incurred. Existing methods for autonomous inspection could not be extended for vehicles due to the following reasons: First, several existing methods require a 3D model of the structure, which is not available for every vehicle. Second, existing methods require expensive depth sensor for localization and path planning. Third, current approaches do not account for the semantic understanding of the vehicle, which is essential for identifying parts. Our instance invariant visual servoing framework is capable of autonomously navigating to every essential part of a vehicle for inspection and can be initialized from any random pose. To the best our knowledge, this is the first approach demonstrating fully autonomous visual inspection of vehicles using MAVs. We have validated the efficacy of our approach through a series of experiments in simulation and outdoor scenarios.     

Experiments in contact control

This article describes the implementation, experimentation, and application of contact control schemes for a 7-DOF Robotics Research arm. The contact forces and torques are measured in the sensor frame by the 6-axis force/torque sensor mounted at the wrist, are compensated for gravity, and then are transformed to the tool frame in which the contact task is defined and executed. The contact control schemes are implemented on the existing robot Cartesian position control system at 400Hz, do not require force rate information, and are extremely simple and computationally fast. Three types of contact control schemes are presented: compliance control, force control, and dual-mode control. In the compliance control scheme, the contact force is fed back through a lag-plus-feedforward compliance controller so that the end-effector behaves like a spring with adjustable stiffness; thus the contact force can be controlled by the reference position command. In the force control scheme, a force setpoint is used as the command input and a proportional-plus-integral force controller is employed to ensure that the contact force tracks the force setpoint accurately. In the dual-mode control scheme, the end-effector approaches and impacts the reaction surface in compliance mode, and the control scheme is then switched automatically to force mode after the initial contact has been established. Experimental results are presented to demonstrate contact with hard and soft surfaces under the three proposed control schemes. The article is concluded with the application of the proposed schemes to perform a contact-based eddy-current inspection task. In this task, the robot first approaches the inspection surface in compliance control until it feels that it has touched the surface, and then automatically levels the end-effector on the surface. The robot control system then transitions to force control and applies the desired force on the surface while executing a scanning motion. At the completion of the inspection task, the robot first relaxes the applied force and then retracts from the surface. © 1996 John Wiley & Sons, Inc.     

基于多元优化算法的三维装箱问题的研究

用多元优化算法（Multi-variant optimization algorithm,MOA）实现三维装箱问题的求解.算法通过随机放置和局部调整从而逐步逼近最优解.随机放置是将随机选择的几个箱子装入容器中;局部调整是根据目标函数值对随机放置容器的箱子序列作局部调整优化;通过递推的随机放置和局部调整优化,目标函数值逐步逼近最优值,从而获得一个较为理想的三维装箱方案.算法通过对BR1~BR10共1000组三维装箱问题测试实例的测试仿真,得到理想的装箱效果,说明用多元优化算法实现三维装箱问题的有效性和可行性.     

基于云预存储技术的Docker在线迁移方法

针对基于Docker容器的分布式云计算下出现负载不均衡问题, 有必要将较高负载服务器中的Docker容器进程迁移到其他相对空闲的服务器上. 而传统的容器迁移算法忽视了容器本身的特征, 从而导致在迁移过程中传输效率低下. 基于此, 利用第三方管理平台和数据预存储阈值机制, 提出一种Docker容器动态迁移预存储算法PF-Docker. 首先将Docker容器内部进程运行相关文件和流动数据预存至云端存储器, 然后通过预存储阈值机制减少流动数据的无效传输, 最后在停机传输阶段将流动数据和冗余数据传输给目的服务器. 实验表明, 该方法在Docker容器迁移中能有效地降低迁移时间, 减少数据传输量, 提高容器的容错率.     

Perceptual correction for colour grading using sensor transformations and metameric data

We present a method of colour shade grading for industrial inspection of surfaces, the differences of which are at the threshold of human perception. This method converts the input data from the electronic sensor to the corresponding data as they would have been viewed using the human vision system. Then their differences are computed using a perceptually uniform colour space, thus approximating the way the human experts would grade the product. The transformation from the electronic sensor to the human sensor makes use of synthetic metameric data to determine the transformation parameters. The method has been tested using real data. Received: 17 November 1997 / Accepted: 15 September 1998     

Inspection strategy for availability improvement

In this paper, an inspection strategy is proposed for systems subject to random shocks and whose state is only known through inspection. The shocks magnitudes and times between shocks arrivals are random variables. Each shock induces an amount of damage to the system which is gradually weakened as damage accumulates. The system fails when the total damage exceeds some threshold level. The proposed inspection strategy suggests to inspect the system at predetermined times T₁, T₂,...T _k . If failure is detected, then the system is repaired to a state as good as new, otherwise, it is kept operating. The expression of the system availability is derived. A numerical procedure is developed to generate an inspection sequence which maximizes the system availability. The proposed strategy has been developed for some critical subsystems of trees harvesters. An illustrative example is provided.     

一种基于Cascade R-CNN的电子器件容器质检方法

电子器件容器生产是一种对安全性、高效性、完整性要求极高的过程,是各大企业必须要关注的问题。但是在实际的生产封装过程中,容器上的污渍、容器内的异物,外观的异常不可避免地出现,这些问题亟待解决。目前解决这些问题主要的检测方法还是人工检测和传统的机器视觉的方式,人工检测方式的缺点在于准确率高而效率低,传统机器视觉检测方式是效率高而准确率低,都难以满足高速自动化生产线要求。因此,本文提出一种基于Cascade R-CNN的电子器件容器质检方法,针对实际过程中的容器数据定向改进网络,加入Focal Loss检测难以区分的样本,使用可变形卷积更高效地提取特征,以多尺度训练方式训练强鲁棒性的模型,用于电子器件容器的多类别检测问题。实验结果表明提出的改进的基于Cascade R-CNN的电子器件容器质检模型具有高准确率和强鲁棒性。     

A chain heuristic for the Blocks Relocation Problem

In the Blocks Relocation Problem (BRP) one is given a block retrieval sequence and is concerned with determining a relocation pattern minimizing the total number of moves required to enforce the given retrieval sequence. The importance of the BRP has been constantly growing in recent years, as a consequence of its close connection with the operations inside of a container terminal. Due to the complexity of the BRP, a large number of methods has been developed for finding near optimal solutions. These methods can be divided in two main categories greedy heuristics and more complex methods. The latter achieve results of higher quality, but at the cost of very long execution times. In many cases, this increased calculation time is not an option, and the fast heuristic methods need to be used. Greedy heuristic approaches, in general, apply the heuristic based only on the properties of the block that is being relocated and the current state of the bay. In this paper we propose a new heuristic approach in which when deciding where to relocate a block we also take into account the properties of the block that will be moved next. This idea is illustrated by improving the Min–Max heuristic for the BRP. We compare the new heuristic to several existing methods of this type, and show the effectiveness of our improvements. The tests have been conducted on a wide range of sizes of container bays, using standard test data sets.     

基于CORBA的集装箱检查系统运行检查分系统的设计

“同方威视”大集装箱检查系统运行检查分系统是基于客户机／服务器模式的面积过程的分布式系统,分析了分布式系统各种不同实现技术优缺点。在此基础上提出了基于CORBA的分布式系统的实现技术,将其应用到原有系统中去,使该系统成为三层结构的面向对象的分布式系统,具有良好的可扩展性和可管理性。     

Deep-learning-based anomaly detection for lace defect inspection employing videos in production line

Defect inspection plays an essential role in ensuring quality of industrial products. The most widely used human visual inspection method has some drawbacks such as high cost and low efficiency, which bring an eager demand for the application of automatic defect inspection algorithm in actual production. However, few industrial production lines use automatic detection devices due to the gap between data collected in the actual production environment and ready-made datasets. Lace is one of the industrial products which completely depends on manual defect inspection. The complex and fine texture of lace makes it difficult to extract regular patterns using the existing image-based defect inspection methods. In this paper, we propose to collect lace videos in the weaving stage and design a deep-learning-based anomaly detection framework to detect lace defects. The framework contains three stages, namely video pre-processing stage, pixel reconstruction stage and pixel classification stage. In the offline phase, only defect-free lace videos are needed to train the pixel reconstruction model and calculate the detection threshold by our adaptive thresholding method. In the online phase, the proposed framework reconstructs lace videos and performs defect inspection using reconstruction error and the pre-set threshold. As far as we know, this paper the first to detect fabric defects by videos. Experimental results on artificial defect videos demonstrate the effectiveness of the proposed framework.     

An agent-based approach to multisensor coordination

This paper presents an automated system for multiple sensor placement based on the coordinated decisions of independent, intelligent agents. The problem domain is such that a single sensor system would not provide adequate information for a given sensor task. Hence, it is necessary to incorporate multiple sensors in order to obtain complete information. The overall goal of the system is to provide the surface coverage necessary to perform feature inspection on one or more target objects in a cluttered scene. This is accomplished by a group of cooperating intelligent sensors. In this system, the sensors are mobile, the target objects are stationary and each agent controls the position of a sensor and has the ability to communicate with other agents in the environment. By communicating desires and intentions, each agent develops a mental model of the other agents' preferences, which is used to avoid or resolve conflict situations. In this paper we utilize cameras as the sensors. The experimental results illustrate the feasibility of the autonomous deployment of the sensors and that this deployment can occur with sufficient accuracy as to allow the inspection task to be performed.     

VCS: A new heuristic function for selecting boxes in the single container loading problem

The single container loading problem consists of a container that has to be filled with a set of boxes. The objective of the problem is to maximize the total volume of the loaded boxes. For solving the problem, constructive approaches are the most successful. A key element of these approaches is related to the selection of the box to load next. In this work, we propose a new evaluation function for ranking boxes. Our function rewards boxes that fit well in the container, taking into account the previously placed ones. To construct a more robust function, we consider some other well-known evaluation criteria such as the volume of the block and the estimated wasted volume in the free space of the container. Our approach shows promising results when compared with other state-of-the-art algorithms on a set of 1600 well-known benchmark instances.     

基于知识库的输电线路巡检机器人的越障控制

介绍了一种高压输电线路巡检机器人越障控制方法。高压输电线路巡检机器人在翻越同一障碍物时重复同一套操作动作,可通过在实验室进行越障过程示教,离线学习形成操作知识库,实际越障时自动调用操作知识库并与在线信号相结合完成自主越障动作。讨论了知识库的一般组成和功能,并分析了激光传感器定位的方法以实现巡检机器人滚动轮与导线“对中”。经过实验验证,该控制方法具有稳定可靠,硬件结构简便,能可靠地完成控制任务,实现自主越障。     

A hierarchical threshold secret image sharing

In the traditional secret image sharing schemes, the shadow images are generated by embedding the secret data into the cover image such that a sufficient number of shadow images can cooperate to reconstruct the secret image. In the process of reconstruction, each shadow image plays an equivalent role. However, a general threshold access structure could have other useful properties for the application. In this paper, we consider the problem of secret shadow images with a hierarchical threshold structure, employing Tassa’s hierarchical secret sharing to propose a hierarchical threshold secret image sharing scheme. In our scheme, the shadow images are partitioned into several levels, and the threshold access structure is determined by a sequence of threshold requirements. If and only if the shadow images involved satisfy the threshold requirements, the secret image can be reconstructed without distortion.     

一种灰度化混合法在集装箱箱号识别中的运用

研究一种基于机器视觉的集装箱箱号识别方法。对于集装箱彩色图像预处理过程中的灰度化方法，传统的灰度化算法不能有效弥补图像中污损或其他信息缺失的部分，因此，本文提出使用主成分分析法（PCA）结合贝叶斯阈值估计灰度变化率的混合法对图像的灰度化进行优化，可以在判断图像中某一点灰度值与周围相邻像素点的灰度值的变化率后，弥补缺失信息，有效确定边缘特征，从而使后续的字符识别准确率大大提高。最后使用该算法模型设计实现一套用于港口集装箱的智能检测系统。经过Matlab实验验证，在对50幅港口集装箱箱号图像的识别中，通过使用本文提出的混合灰度化方法，与普通的均值法和加权平均法的灰度化方法相比，准确率更高，其中单一字符准确率可达96%，箱号准确率可达92%。     

集装箱装船顺序的多目标整数规划优化模型

为了解决集装箱堆场装船顺序问题,根据集装箱船舶和配载的实际情况,考虑集装箱的航程,结合集装箱的装载位置,以集装箱堆场的翻箱率、船舶卸载时的翻箱率以及装船后的稳性为目标,建立了装船顺序的多目标规划模型,并基于粒子群算法构造了求解算法,通过MATLAB进行仿真实验,数据结果表明,该模型具有一定的的合理性与可行性。     

Gamma/X-ray linear pushbroom stereo for 3D cargo inspection

For evaluating the contents of trucks, containers, cargo, and passenger vehicles by a non-intrusive gamma-ray or X-ray imaging system to determine the possible presence of contraband, three-dimensional (3D) measurements could provide more information than just 2D measurements. In this paper, a linear pushbroom scanning model is built for such a commonly used gamma-ray or X-ray cargo inspection system. Three-dimensional (3D) measurements of the objects inside a cargo can be obtained by effectively constructing a pushbroom stereo system using two such scanning systems with different scanning angles. A simple but robust calibration method is proposed to find the important parameters of the linear pushbroom sensors. Then, a fast stereo matching algorithm is developed to obtain 3D measurements of the objects under inspection. This algorithm is fully automatic based on free-form deformable registration. An interactive user interface is designed for 3D visualization of the objects of interest. Using the interactive tool, the automatic algorithm is also compared with a very simple semi-automatic algorithm based on point correlation. Experimental results of sensor calibration, stereo matching, 3D measurements and visualization of a 3D cargo container, and the objects inside, are presented.     

一种基于智能终端的温度/振动点检系统设计

工业设备在故障发生前通常伴随着异常振动或者局部超阈值高温，针对机械设备重要环节实施振动、温度监测对机械设备安全可靠运行和故障预警具有重要意义。鉴于当前设备状态点检系统自动化程度低、数据汇总滞后等问题，提出一种基于智能终端的温度/振动点检系统。系统由状态监测层、点检终端层和数据汇总层组成。状态监测层基于红外温度传感器和ICP型加速度传感器设计了便携式状态监测节点；点检终端层以Android系统为开发平台设计了终端软件，软件功能包括：数据曲线绘制、阈值报警、历史数据查看和数据统计参量获取等；数据汇总层利用Java和MySQL设计实现了数据库服务器。系统验证实验结果表明：状态监测节点加速度、温度测量准确，相比于标准测量系统，本系统加速度测量最大相对误差为0.21%，终端软件和数据库服务器运行正常，符合预期设计目标。     

Local Image Reconstruction and Subpixel Restoration Algorithms

This paper introduces a new class of reconstruction algorithms that are fundamentally different from traditional approaches. We deviate from the standard practice that treats images as point samples. In this work, image values are treated as area samples generated by nonoverlapping integrators. This is consistent with the image formation process, particularly for CCD and CID cameras. We show that superior results are obtained by formulating reconstruction as a two-stage process: image restoration followed by application of the point spread function (PSF) of the imaging sensor. By coupling the PSF to the reconstruction process, we satisfy a more intuitive fidelity measure of accuracy that is based on the physical limitations of the sensor. Efficient local techniques for image restoration are derived to invert the effects of the PSF and estimate the underlying image that passed through the sensor. The reconstruction algorithms derived herein are local methods that compare favorably to cubic convolution, a well-known local technique, and they even rival global algorithms such as interpolating cubic splines. Evaluations are made by comparing their passband and stopband performances in the frequency domain, as well as by direct inspection of the resulting images in the spatial domain. A secondary advantage of the algorithms derived with this approach is that they satisfy an imaging-consistency property. This means that they exactly reconstruct the image for some function in the given class of functions. Their error can be shown to be at most twice that of the "optimal" algorithm for a wide range of optimality constraints.     

Probability versus possibility and their application to actuator sensor networks

Communication range has a direct impact on the network capacity, and consequently, is a limiting parameter of actuator sensor network scalability. Hence, transmission power control is a critical component of actuator sensor network scalability. In this paper we present and analyze two different approaches, namely, probabilistic and possibilistic approaches. Through simulation the two methods will be examined, and their effect on network scalability will be analyzed. Both approaches have shown a significant improvement in the system throughput. Both approaches are complimented with a variable-step low-level controller to minimize interference.