Fixed Anchor Points Research Articles

Multi-view clustering with adaptive anchor and bipartite graph learning

Multi-view subspace clustering optimizes and integrates the graph structure information of each view. At present, the subspace clustering methods based on the abstract graph have better performance and improve the clustering results. Although the existing clustering algorithms have achieved excellent results, there are still four deficiencies: 1) Expensive time overhead, with most algorithms having a high time complexity; 2) Using fixed anchor points and the separation of anchor graph learning from subsequent graph construction, resulting in inadequate use of underlying graph structure between views; 3) Multi-view data have inevitable noise and in the original high-dimensional space data fusion may cause the loss of important information; 4) Most algorithms require additional post-processing to obtain clustering labels. To solve the above problems, we innovate a novel anchor-adaptive multi-view clustering algorithm based on a bipartite graph . Specifically, anchor graph learning and subspace graph construction are adaptively combined into a unified optimization framework. The projection matrix, consensus anchor matrix, and similarity matrix optimize each other to promote the clustering effect and structure a constrained bipartite graph to describe the relationship between representative points and sample points. At the same time, connectivity constraints are used to ensure that the connected components represent clusters directly. Our method has linear time complexity about sample size. Comparison experiments with the state-of-the-art algorithms demonstrate the effectiveness of the proposed method on various benchmark datasets. Moreover, our method is robust to noisy data and suitable for large-scale datasets.

A graph optimization approach to range-based relative location

With the development of multi-robot cluster system, the research of multi-node relative pose estimation is in the ascendant. However, for the environment without GNSS or fixed anchors, the problem of relative pose estimation is still challenging. In this paper, a general algorithm and system framework based on graph optimization algorithm is proposed to fuse inter- and intra-robot measurements, as well as mobility models with sliding windows for relative attitude estimation. In order to verify the feasibility and universality of the algorithm, the algorithm has used to design a relative positioning system based on UWB positioning with a “single-node multi-tags” system structure, which can simultaneously obtain reliable relative positions and directions. The design of multi-source fusion can further improve the accuracy and robustness of relative positioning. Experiment results shows that in the harsh environment without GNSS and fixed anchor points, the relative pose estimation accuracy of this system can reach centi-meter level, which may be the best potential choice for relative positioning of multi robot cluster in complex environment.

CCRobot-IV: An Obstacle-Free Split-Type Quad-Ducted Propeller-Driven Bridge Stay Cable-Climbing Robot

This letter presents CCRobot-IV, the fourth version of a climbing robot designed for bridge cable-inspection tasks. CCRobot-IV inherits design features from the previous CCRobot series, and has improved capability for crossing cables with obstacles such as helical ribs, small metal accessories, and various other obstacles. CCRobot-IV consists of a quad-ducted propeller-driven climbing precursor and an affiliated payload-carrying body. Because a quad-ducted propeller does not depend on friction generated by mutual contact and extrusion, the precursor’s locomotion is decoupled from the surface of the bridge cable and the obstacles on it. When the precursor climbs up to reach the set position, it uses its gripper’s self-locking palms to grasp the bridge cable, which creates a fixed anchor point that allows the payload-carrying body to pull itself up using wires and two winches (which are a type of driving wheel that do not require extrusion force on the cable to produce adhesion and friction). Therefore, the robot’s payload capacity is also decoupled from adhesion to the cable surface, and thus the entire system has obstacle-free operation. Experimental tests and field tests have demonstrated CCRobot-IV’s climbing performance, payload capacity, and potential application utility.

Real-Time Reconfiguration Planning for the Dynamic Control of Reconfigurable Cable-Driven Parallel Robots

Abstract The movable anchor points make reconfigurable cable-driven parallel robots (RCDPRs) advantageous over conventional cable-driven parallel robots with fixed anchor points, but the movable anchor points also introduce an inherent problem—reconfiguration planning. Scholars have proposed reconfiguration planning approaches for RCDPRs, taking into account the statics and kinematics of RCDPRs. However, a real-time reconfiguration planning approach that considers the dynamics of an RCDPR and is computationally efficient enough to be integrated into the RCDPR's dynamic controller is still not available in the literature yet. This paper develops a real-time reconfiguration planning approach for RCDPRs. A novel reconfiguration value function is defined to reflect the “value” of an RCDPR configuration and provide a reference index for the reconfiguration planning of an RCDPR. And then, the developed approach conducts reconfiguration planning based on the value of RCDPR configurations. The developed approach is computationally efficient, reducing the reconfiguration planning time by more than 93%, compared to single iteration of a box-constrained optimization-based reconfiguration planning approach. Such a high efficiency allows the developed approach to be integrated into an RCDPR's dynamic controller that usually runs with a high frequency. Integrating reconfiguration planning and dynamic control enhances the control performance of the RCDPR. To verify the effectiveness of the developed approach and the integration of reconfiguration planning and dynamic control for RCDPRs, a case study of an RCDPR with seven cables and four movable anchor points is conducted.

Efficient One-Pass Multi-View Subspace Clustering with Consensus Anchors

Multi-view subspace clustering (MVSC) optimally integrates multiple graph structure information to improve clustering performance. Recently, many anchor-based variants are proposed to reduce the computational complexity of MVSC. Though achieving considerable acceleration, we observe that most of them adopt fixed anchor points separating from the subsequential anchor graph construction, which may adversely affect the clustering performance. In addition, post-processing is required to generate discrete clustering labels with additional time consumption. To address these issues, we propose a scalable and parameter-free MVSC method to directly output the clustering labels with optimal anchor graph, termed as Efficient One-pass Multi-view Subspace Clustering with Consensus Anchors (EOMSC-CA). Specially, we combine anchor learning and graph construction into a uniform framework to boost clustering performance. Meanwhile, by imposing a graph connectivity constraint, our algorithm directly outputs the clustering labels without any post-processing procedures as previous methods do. Our proposed EOMSC-CA is proven to be linear complexity respecting to the data size. The superiority of our EOMSC-CA over the effectiveness and efficiency is demonstrated by extensive experiments. Our code is publicly available at https://github.com/Tracesource/EOMSC-CA.

Virtual indoor-GPS for measurement uncertainty determination in reconfigurable environments

In Line-less Mobile Assembly Systems, the mobilization of assembly resources and products enables rapid physical system reconfigurations to increase flexibility and adaptability. The clean floor approach discards fixed anchor points, so that assembly resources such as mobile robots and automated guided vehicles transporting products can adapt to new products and form new processes. Associated challenges are accurate spatial referencing between mobile resources to meet assembly tolerance requirements. There is a need for more accurate positioning data to locate and navigate mobile assembly resources. An indoor-GPS, as a distributed large-scale metrology system, is able to cover a wide shop floor area and to obtain positioning data with uncertainties in the submillimeter range. The measurement uncertainty of such a system depends on the spatial distribution of the transmitters and the receiver positions. To be able to validate positioning tolerance requirements of an assembly process, measurement uncertainties must be determined. Virtual measurements simulate measurement processes and model dependencies between the environment and the metrology system. This work presents a novel approach for a virtual indoor-GPS to determine measurement uncertainties during a process and to evaluate the measurement process capability. Experiments show the validity of the virtual indoor-GPS which can be used as a planning tool for metrology system setups within Line-less Mobile Assembly Systems.

Improving Indoor Localization Using Mobile UWB Sensor and Deep Neural Networks

Accurate localization in indoor environments with ultra-wideband (UWB) technology has long attracted much attention. However, due to the presence of multipath components or non-line of sight (NLOS) propagation of the radio signals, it has been converted to a critical challenge. Existing solutions use many fixed anchors in the indoor environment. Particularly, large areas require many anchor points and in the case of unexpected events that lead to the destruction of existing infrastructures, the fixed anchor points cannot be used. In this paper, a novel localization framework based on the transmitting signal from a mobile UWB sensor on the outside of the building and its received signal regarding the modified Saleh Valenzuela (SV) channel model is presented. After preprocessing the received signals, two new procedures to reduce the ranging error caused by multipath components are proposed. In the first procedure, two machine learning algorithms including multi-layer perceptron (MLP) and support vector machine (SVM) using the extracted features from the received UWB signal time and power vectors are implemented. Moreover, in the second procedure, two deep learning algorithms including MLP and convolutional neural networks (CNNs) using the received UWB signal time and power vectors are implemented to improve the performance of the indoor localization system. The simulation results show that the architecture designed for the convolutional neural network based on the hybrid dataset (the combination of the dataset related to received UWB signal time and power vectors) provides a mean absolute error (MAE) of about 3 cm.

A Single-Copter UWB-Ranging-Based Localization System Extendable to a Swarm of Drones

This paper presents a single-copter localization system as a first step towards a scalable multihop drone swarm localization system. The drone was equipped with ultrawideband (UWB) transceiver modules, which can be used for communication, as well as distance measurement. The location of the drone was detected based on fixed anchor points using a single type of UWB transceiver. Our aim is to create a swarm localization system that enables drones to switch their role between an active swarm member and an anchor node to enhance the localization of the whole swarm. To this end, this paper presents our current baseline localization system and its performance regarding single-drone localization with fixed anchors and its integration into our current modular quadcopters, which was designed to be easily extendable to a swarm localization system. The distance between each drone and the anchors was measured periodically, and a specially tailored gradient descent algorithm was used to solve the resulting nonlinear optimization problem. Additional copter and wireless-specific adaptations were performed to enhance the robustness. The system was tested with a Vicon system as a position reference and showed a high precision of 0.2 m with an update rate of <10 Hz. Additionally, the system was integrated into the FINken copters of the SwarmLab and evaluated in multiple outdoor scenarios. These scenarios showed the generic usability of the approach, even though no accurate precision measurement was possible.

Analysis, planning and control for cooperative transportation of tethered multi-rotor UAVs

The calculation of available wrench set of tethered multi-rotor UAVs is more challenging than that of the traditional cable-driven parallel robots (CDPRs) with fixed anchor points, due to the bounded thrust, motion acceleration and external disturbance acting on multi-rotor unmanned aerial vehicles (UAVs). To our best knowledge, this is the first work to investigate the dynamic available wrench set. We define an index called capacity margin to evaluate the robustness of the quasi-static motion for different system configurations and to represent the available maximum acceleration of the payload. Moreover, the feasible trajectories of multi-rotor UAVs are optimized using a tension distribution algorithm to accomplish the manipulation of the payload. Without the need of centralized ground control station, payload states and UAVs' velocity information, a decentralized output feedback control based on fixed-time extended state observer (ESO) is developed for the group of multi-rotor UAVs. The rigorous proof of stability of the closed-loop system is conducted. Finally, numerical simulations and comparative experiments are demonstrated to validate the proposed tension distribution algorithm and control strategy.

Rotational Workspace Expansion of a Planar CDPR with a Circular End-Effector Mechanism Allowing Passive Reconfiguration

Cable-Driven Parallel Robots (CDPR) operate over a large positional workspace and a relatively large orientation workspace. In the present work, the expansion of the orientation Wrench Feasible Workspace (WFW) in a planar four-cable passive reconfigurable parallel robot with three degrees of freedom was determined. To this end, we proposed a circular-geometry effector mechanism, whose structure allows automatic mobility of the two anchor points of the cables supporting the End Effector (EE). The WFW of the proposed circular structure robot was compared with that of a traditional robot with a rectangular geometry and fixed anchor points. Considering the feasible geometric and tension forces on the cables, the generated workspace volume of the robot was demonstrated in an analysis-by-intervals. The results were validated by simulating the orientation movements of the robot in ADAMS software and a real experimental test was developed for a hypothetical case. The proposed design significantly expanded the orientation workspace of the robot. The remaining limitation is the segment of the travel space in which the mobile connection points can slide. Overcoming this limitation would enable the maximum rotation of the EE.

ВНЕДРЕНИЕ СТАЦИОНАРНЫХ АНКЕРНЫХ УСТРОЙСТВ ДЛЯ БЕЗОПАСНОЙ ЭКСПЛУАТАЦИИ НА ВЫСОТЕ ОПОР ВОЗДУШНЫХ ЛИНИЙ СВЯЗИ И ЛИНИЙ ЭЛЕКТРОПЕРЕДАЧ

The results of the analysis of the existing safety measures for the production of works at altitude on overhead lines and power lines, which indicate the problems of organizing reliable insurance against falling from a height, are given. It is shown that there is not always a technical possibility to realize the fastening of flexible anchor points for securing safety systems to VL towers, which are designed to ensure the safety of work at height. Also, problems are shown in the organization of insurance when performing work on high-voltage power lines. Specific cases have been identified where it is technically impossible to put an anchor loop on a support or there are practical difficulties in the process of dressing-releasing a flexible anchor loop, or when putting an anchor loop on a support, it slips into parts that are not designed for the maximum load, which should be 22 kN. It is concluded that the use of flexible anchor points on the supports of overhead lines is not always possible or safe, and on the poles of the transmission line in general often violates the existing labor protection rules when working at height. A number of universal technical solutions to ensure the safety of work on overhead lines and transmission lines with the help of the organization of fixed anchor points and lines on the support, equipment which it is advisable to carry out at the stage of construction or reconstruction. It is also proposed to visualize the corresponding symbols of the anchor device on the overhead lines and power lines, which will facilitate the work on planning works on the supports and will improve the safety of work at height. The expediency of introduction at the legislative level of additions to the sectoral and intersectoral labor protection requirements for the installation of a fixed anchor point for fixing safety systems in the design, construction and reconstruction of overhead lines is shown.

Lightness, brightness, and anchoring.

The majority of work in lightness perception has evaluated the perception of lightness using flat, matte, two-dimensional surfaces. In such contexts, the amount of light reaching the eye contains a conflated mixture of the illuminant and surface lightness. A fundamental puzzle of lightness perception is understanding how it is possible to experience achromatic surfaces as specific achromatic shades in the face of this ambiguity. It has been argued that the perception of lightness in such contexts implies that the visual system imposes an "anchoring rule" whereby a specific relative luminance (the highest) serves as a fixed point in the mapping of image luminance onto the lightness scale ("white"). We conducted a series of experiments to explicitly test this assertion in contexts where this mapping seemed most unlikely-namely, low-contrast images viewed in dim illumination. Our results provide evidence that the computational ambiguity in mapping luminance onto lightness is reflected in perceptual experience. The perception of the highest luminance in a two-dimensional Mondrian display varied monotonically with its brightness, ranging from midgray to white. Similar scaling occurred for the lowest luminance and, by implication, all other luminance values. We conclude that the conflation between brightness and lightness in two-dimensional Mondrian displays is reflected in perception and find no support for the claim that any specific relative luminance value acts as a fixed anchor point in this mapping function.

Monitoring Sinew Contraction During Formation of Tissue-Engineered Fibrin-Based Ligament Constructs

The ability to study the gross morphological changes occurring during tissue formation is vital to producing tissue-engineered structures of clinically relevant dimensions in vitro. Here, we have used nondestructive methods of digital imaging and optical coherence tomography to monitor the early-stage formation and subsequent maturation of fibrin-based tissue-engineered ligament constructs. In addition, the effect of supplementation with essential promoters of collagen synthesis, ascorbic acid (AA) and proline (P), has been assessed. Contraction of the cell-seeded fibrin gel occurs unevenly within the first 5 days of culture around two fixed anchor points before forming a longitudinal ligament-like construct. AA+P supplementation accelerates gel contraction in the maturation phase of development, producing ligament-like constructs with a higher collagen content and distinct morphology to that of unsupplemented constructs. These studies highlight the importance of being able to control the methods of tissue formation and maturation in vitro to enable the production of tissue-engineered constructs with suitable replacement tissue characteristics for repair of clinical soft-tissue injuries.

Using experienced activity spaces to measure foodscape exposure

Researchers are increasingly interested in understanding how food environments influence eating behavior and weight-related health outcomes. Little is known about the dose-response relationship between foodscapes and behavior or weight, with measures of food exposure having mainly focused on fixed anchor points including residential neighborhoods, schools, or workplaces. Recent calls have been made to extend the consideration of environmental influences beyond local neighborhoods and also to shift away from place-based, to people-based, measures of exposure. This report presents analyses of novel activity-space measures of exposure to foodscapes, combining travel survey data with food store locations in Montreal and Quebec City, Canada. The resulting individual activity-space experienced foodscape exposure measures differ from traditional residential-based measures, and show variations by age and income levels. Furthermore, these activity-space exposure measures once modeled, can be used as predictors of health outcomes. Hence, travel surveys can be used to estimate environmental exposure for health survey participants.

Designing a Response Scale to Improve Average Group Response Reliability

Abstract Creating surveys is a common task in evaluation research; however, designing a survey instrument to gather average group response data that can be interpreted in a meaningful way over time can be challenging. When surveying groups of people for the purpose of longitudinal analysis, the reliability of the result is often determined by the response scale used. Likert scales and numeric continua are commonly used for this purpose. Both scales are relatively easy to create and both have distinct advantages and disadvantages. This paper reports the findings of a project to combine a fully anchored Likert scale with a numeric rating scale. The resulting scale for a follow-up survey utilises fixed anchor points along with visual cues to provide a layer of direction for the respondents; it also uses a numeric continuum to elicit a second layer of information that is more discriminating. The results are both easily interpreted on the original scale and are more appropriate for longitudinal comparison purp...

Metrology, essential to trade, industry and society

Internal markets as well as the globalization of trade, industry and society require comparability of calibration, measurement and test results through traceability to the International System of Units (SI), which represents the coherent and long-term stable fixed anchor points in measurement. Internal markets, trade and accreditation agreements also require that non-tariff barriers to trade are removed. The removal of Technical Barriers to Trade (TBT) and implementation of Sanitary and Phyto-Sanitary (SPS) measures should lead to a situation where ‘once measured or tested, everywhere accepted’. To achieve this situation, a credible, transparent metrology agreement needs to be implemented under the Inter-Governmental Treaty of the Metre Convention. The need for a reliable world metrology system is driven not only by trade requirements but equally by societal requirements. Improvement of the quality of life is highly served by reliable, traceable and more accurate measurements, particularly in areas such as health care, food safety and nutritional content, environmental and pollution control and climate change, forensics and security. In addition, credible ‘soft/perceptive’ measurements, such as smell, taste, colour, glance, form, among others, will contribute to the quality of life. Sustainable competitiveness and innovation require accurate, traceable measurement results, not only in the ‘classical’ field of physical measurements, but also in the fields of chemical analysis, advanced materials and material properties and in new fields like nano-metrology and biotechnology. These new areas of metrology also require the development of new measurement technologies. The wide application of information technology, in the form of fully automated, remote-controlled and monitored measurement systems, also requires new innovative approaches. In as much that accurate, comparable measurements are essential for a fair and safe society, it is evident that the authorities have formulated and are increasingly formulating regulations that contain requirements with respect to traceability and measurement uncertainty. The economic interest in good measurements is well demonstrated by the fact that global trade in commodities amounts to more than 12 trillion USD, of which 80% is affected by standards and regulation. The compliance costs are estimated to be about 10% of the production costs. The global markets of clinical chemistry and laboratory medicine and pharmaceuticals have a value of some 300 billion USD per year. Annual savings as a consequence of comparable, more accurate measurement results with a smaller measurement uncertainty will easily amount up to many billions of U.S. dollars. Presented at the 3rd International Conference on Metrology, November 2006, Tel Aviv, Israel.

Predicting quality of life outcomes as a guide for decision-making: the challenge of hitting a moving target

AbstractIn animal care, when current decisions are made to maximise long-term quality of life (QoL), a key necessity is being able to make accurate predictions about how current choices will affect the animal's future QoL. However, in the procession of any individual's life, many factors that influence QoL change — some are foreseeable, many are not. Moreover, QoL has no fixed anchor points; it is dynamic, mutable, with a shifting frame of reference over time. In addition to actual changes in QoL over time, numerous factors have been identified that influence one's ability to adopt the mindset of the individual at a later point in time — for one's self as well as that of others. It has been shown that in people, across a wide range of health conditions, individuals with illness or disability typically report greater happiness and QoL than do healthy people envisioning themselves in similar circumstances (‘the disability paradox‘). Difficulties in QoL outcome prediction fall into two categories: (1) predictions made with the wrong mindset, in which there is a mismatch between the mindset of the assessor/predictor and that of the assessee/experiencer; and (2) predictions made on the basis of unforeseen or incorrectly estimated psychological changes in the assessee/experiencer.

A new extreme quantile estimator for heavy-tailed distributions

The classical estimation method for extreme quantiles of heavy-tailed distributions was presented by Weissman (J. Amer. Statist. Assoc. 73 (1978) 812–815) and makes use of the Hill estimator (Ann. Statist. 3 (1975) 1163–1174) for the positive extreme value index. This index estimator can be interpreted as an estimator of the slope in the Pareto quantile plot in case one considers regression lines passing through a fixed anchor point. In this Note we propose a new extreme quantile estimator based on an unconstrained least squares estimator of the index, introduced by Kratz and Resnick (Comm. Statist. Stochastic Models 12 (1996) 699–724) and Schultze and Steinebach (Statist. Decisions 14 (1996) 353–372) and we study its asymptotic behavior. To cite this article: A. Fils, A. Guillou, C. R. Acad. Sci. Paris, Ser. I 338 (2004).

Gamut Mapping Algorithm Using Lightness Mapping and Multiple Anchor Points for Linear Tone and Maximum Chroma Reproduction

This article proposes a new gamut-mapping algorithm (GMA) that utilizes both lightness mapping and multiple anchor points. The proposed lightness mapping minimizes the lightness difference of the maximum chroma between two gamuts and produces the linear tone in bright and dark regions. In the chroma mapping, a separate mapping method that utilizes multiple anchor points with constant slopes plus a fixed anchor point is proposed to maintain the maximum chroma and produce a uniform tonal dynamic range. As a result, the proposed algorithm is able to reproduce high quality images using low-cost color devices.

Prop-imperfection subsea pipeline buckling

In-service buckling of subsea pipelines can occur due to the introduction of axial compressive forces caused by the constrained expansions set up by thermal and internal pressure actions. Proposed herein is a mathematical model relating to a pipeline, the otherwise horizontal and straight idealised lie of which is interrupted by an encounter with an isolated prop or point irregularity. The overbend produced can serve, in the presence of enhanced topologies involving trenching, burial, discrete or continuous, and fixed anchor points, to trigger vertical or upheaval buckling of the pipeline under in-service conditions. The results of a series of case studies are contrasted with data appertaining to alternative models available in the literature: experimental support is additionally noted. By questioning the implicit stress-free-when-straight assumption present in these alternative models, it is considered that a consistent, imperfection-prone isolated prop formulation is hereby provided, suitable for design application.