A comparative simulation study of work processes in autonomous production cells

An approach to human‐centered design and assessment of work processes in flexible manufacturing systems with the help of dynamic task networks is presented. To model and simulate the task networks, the method of timed colored Petri Nets is used. Two task networks are developed. The first task network is a model of work processes in Autonomous Production Cells (APCs). The second task network represents work processes in conventional Computer Numerically Controlled (CNC)‐based manufacturing systems. The material processing technology is associated with 5‐axis milling. The values of attributes of task elements were acquired empirically on a fine‐grained level with reference to a sample milling order. Comparative hypotheses regarding time‐on‐task, supervisory control functions, levels of cognitive control, human error (HE), and labor division were then formulated. To test these hypotheses, several simulation experiments were conducted. The results from inferential statistics show that single‐operator APCs have a 30% higher efficiency in relation to total time‐on‐task. Moreover, the level of cognitive control is significantly shifted toward rule‐ and knowledge‐based behavior. Surprisingly, the simulation of minor HE does not demonstrate a significantly worse performance from APCs. A simulated labor division among central process planner and production operator allows an additional efficiency improvement of approximately 15%. However, the labor division has two important drawbacks: first, a sequential incompleteness of operators' task spectrum occurs; second, the operator has to cope with hierarchical task incompleteness. Finally, a sensitivity analysis was carried out to investigate the effects of varying lot sizes and number of processed orders. © 2002 John Wiley & Sons, Inc.     

Delineating compositionally different dykes in the Ulukışla basin (Central Anatolia,Turkey) using computer‐enhanced multi‐spectral remote sensing data

In the Uluk??la basin (Central Anatolia, Turkey) several geological mapping campaigns were carried out using conventional field methods to delineate compositionally different Middle–Upper Eocene dykes. However, complete and correct mapping of these dykes was hampered by rugged terrain, lack of road access, wide spatial dyke distributions with small exposures and diverse weathering of these dykes. For these reasons, Landsat‐5 Thematic Mapper (TM) satellite image of the study area was used to facilitate delineation of the exact boundaries of gabbroic, dioritic and trachytic dykes found in the area. Remotely sensed data were analysed using several image enhancement procedures, including colour composites, band ratios, principal components analysis (PCA), and Crosta technique. Results obtained from all the processes were examined, and it was found that dyke boundaries are best visible in the PCA123 image; RGB 731 colour composite; TM band ratio 5/7, 5/1, 4 combination; and 1457‐PC4 image obtained by Crosta technique. The alteration differences of three dyke groups are enhanced much better in the 1457‐PC4 image obtained by Crosta technique, which highlights the hydroxyl‐bearing minerals as white‐coloured pixels. Using computer‐enhanced multi‐spectral remote sensing data, we were able to map the boundaries and spatial distributions of compositionally different dykes, which otherwise is an overwhelmingly difficult task to achieve using conventional field methods. In similar settings, remote sensing techniques applied in this study may provide an efficient and low‐cost alternative to time‐consuming and physically demanding field‐mapping campaigns.     

A Comparative Study of Head‐Mounted and Table‐Mounted Augmented Vision Systems for Assembly Error Detection

Within the Cluster of Excellence “Integrative Production Technology for High‐Wage Countries,” a research project has been initiated to study self‐optimizing assembly cells and to design innovative ergonomic human–machine interfaces of the cell's numerical control. An experimental assembly cell was designed in which two robots carry out a certain repertoire of coordinated pick‐and‐place operations with small workpieces. To support the human operator while monitoring the operations and intervening in the case of assembly errors, an Augmented Vision System (AVS) has been designed and developed. The study described in this article deals with the ergonomic presentation of assembly information by the AVS to support the human operator in detecting assembly errors in small workpieces. Two laboratory experiments were carried out to compare two visual display types and to investigate different variations of presenting assembly information. Forty‐eight subjects participated in the experiments. The statistical analysis shows that the use of a head‐mounted display instead of a common table‐mounted display for the AVS increases the accuracy of assembly error detection significantly (α = 0.05). In contrast, a trend toward a longer detection time was found. © 2012 Wiley Periodicals, Inc.     

Online turnover‐free control for a mobile agent with a terrain prediction sensor

This paper proposes a turnover‐free control method for a teleoperated mobile agent (or vehicle) moving through uneven terrain. The teleoperated agent is primarily driven by an operator at a remote site and is able to react autonomously when a possible turnover is predicted. In order to predict the turnover, a low‐cost terrain prediction sensor has been developed using a camera vision with a structured laser light. Since it is difficult for an operator to predict the reactive motion of the agent, a force reflection technique with a force feedback joystick is employed to intuitively recognize the inconsistency between the intended motion and the reactive motion of the agent. Finally, to verify the feasibility and effectiveness of the proposed method, experiments with the ROBHAZ‐DT (actual mobile agent) have been carried out. In the experiments, the operator could recognize the reactive motion of the agent for turnover prevention through force reflection while the agent was moving on slopped terrain. © 2006 Wiley Periodicals, Inc.     

Mesh‐Free Discrete Laplace–Beltrami Operator

In this work we propose a new discretization method for the Laplace–Beltrami operator defined on point‐based surfaces. In contrast to the existing point‐based discretization techniques, our approach does not rely on any triangle mesh structure, turning out truly mesh‐free. Based on a combination of Smoothed Particle Hydrodynamics and an optimization procedure to estimate area elements, our discretization method results in accurate solutions while still being robust when facing abrupt changes in the density of points. Moreover, the proposed scheme results in numerically stable discrete operators. The effectiveness of the proposed technique is brought to bear in many practical applications. In particular, we use the eigenstructure of the discrete operator for filtering and shape segmentation. Point‐based surface deformation is another application that can be easily carried out from the proposed discretization method.     

Building‐based damage detection due to earthquake using the watershed segmentation of the post‐event aerial images

This paper presents an approach for detecting the damaged buildings due to earthquake using the watershed segmentation of the post‐event aerial images. The approach utilizes the relationship between the buildings and their cast shadows. It is based on an idea that if a building is damaged, it will not produce shadows. The cast shadows of the buildings are detected through an immersion‐based watershed segmentation. The boundaries of the buildings are available and stored in a GIS as vector polygons. The vector‐building boundaries are used to match the shadow casting edges of the buildings with their corresponding shadows and to perform assessments on a building‐specific manner. For each building, a final decision on the damage condition is taken, based on the assessments carried out for that building only. The approach was implemented in Golcuk, one of the urban areas most strongly hit by the 1999 Izmit, Turkey earthquake. To implement the approach, a system called the Building‐Based Earthquake Damage Assessment System was developed in MATLAB. Of the 284 buildings processed and analysed, 229 were correctly labelled as damaged and undamaged, providing an overall accuracy of 80.63%.     

Shape‐from‐Operator: Recovering Shapes from Intrinsic Operators

We formulate the problem of shape‐from‐operator (SfO), recovering an embedding of a mesh from intrinsic operators defined through the discrete metric (edge lengths). Particularly interesting instances of our SfO problem include: shape‐from‐Laplacian, allowing to transfer style between shapes; shape‐from‐difference operator, used to synthesize shape analogies; and shape‐from‐eigenvectors, allowing to generate ‘intrinsic averages’ of shape collections. Numerically, we approach the SfO problem by splitting it into two optimization sub‐problems: metric‐from‐operator (reconstruction of the discrete metric from the intrinsic operator) and embedding‐from‐metric (finding a shape embedding that would realize a given metric, a setting of the multidimensional scaling problem). We study numerical properties of our problem, exemplify it on several applications, and discuss its imitations.     

Tools and strategies for debugging distributed stream processing applications

Distributed data stream processing applications are often characterized by data flow graphs consisting of a large number of built‐in and user‐defined operators connected via streams. These flow graphs are typically deployed on a large set of nodes. The data processing is carried out on‐the‐fly, as tuples arrive at possibly very high rates, with minimum latency. It is well known that developing and debugging distributed, multi‐threaded, and asynchronous applications, such as stream processing applications, can be challenging. Thus, without domain‐specific debugging support, developers struggle when debugging distributed applications. In this paper, we describe tools and language support to support debugging distributed stream processing applications. Our key insight is to view debugging of stream processing applications from four different, but related, perspectives. First, debugging the semantics of the application involves verifying the operator‐level composition and inspecting the flows at the logical level. Second, debugging the user‐defined operators involves traditional source‐code debugging, but strongly tied to the stream‐level interactions. Third, debugging the deployment details of the application require understanding the runtime physical layout and configuration of the application. Fourth, debugging the performance of the application requires inspecting various performance metrics (such as communication rates, CPU utilization, etc.) associated with streams, operators, and nodes in the system. In light of this characterization, we developed several tools such as a debugger‐aware compiler and an associated stream debugger, composition and deployment visualizers, and performance visualizers, as well as language support, such as configuration knobs for logging and tracing, deployment configurations such as operator‐to‐process and process‐to‐node mappings, monitoring directives to inspect streams, and special sink adapters to intercept and dump streaming data to files and sockets, to name a few. We describe these tools in the context of Spade —a language for creating distributed stream processing applications, and System S —a distributed stream processing middleware under development at the IBM Watson Research Center. Published in 2009 by John Wiley & Sons, Ltd.     

Stability analysis in identification of interval type‐2 adaptive neuro‐fuzzy inference system: Contribution to a novel Lyapunov function

In recent years, control research has strongly highlighted the issue of training stability in the identification of non‐linear systems. This paper investigates the stability analysis of an interval type‐2 adaptive neuro‐fuzzy inference system (IT2ANFIS) as an identifier through a novel Lyapunov function. In so doing, stability analysis is initially conducted on the IT2ANFIS identifier, while performing the online training of both the antecedent and the consequent parameters by the gradient descent (GD) algorithm. In addition, the same stability analysis is carried out when the antecedent and the consequent parameters are trained by GD and forgetting factor recursive least square (FRLS) algorithms, respectively (GD + FRLS). A novel Lyapunov function is proposed in this study in order for the identifier stability to attain the required conditions. These conditions determine the permissible boundaries for the covariance matrix and the learning rates at every iteration of the identification procedure. Stability analysis reveals that wide range of learning rates is obtained. Furthermore, simulation results indicate that when the permissible boundaries are selected according to the proposed stability analysis, a stable identification process with appropriate performance is achieved.     

Hybrid flowshop with unrelated machines, sequence-dependent setup time, availability constraints and limited buffers

This paper presents a genetic algorithm for an important production scheduling problem. Since the problem is NP-hard, we focus on suboptimal scheduling solutions for the hybrid flowshop with unrelated machines, sequence-dependent setup time, availability constraints, and limited buffers. The production environment of a television assembly line for inserting electronic components is considered. The proposed genetic algorithm is a modified and extended version of the algorithm for a problem without limited buffers. It takes into account additional limited buffer constraints and uses a new crossover operator and stopping criteria. Experimental results carried out on real production settings show an improvement in scheduling when the proposed algorithm is used.     

Design of automation for telerobots and the effect on performance,operator situation awareness,and subjective workload

In this article we review and assess human‐centered level of automation (LOA), an alternate approach to traditional, technology‐centered design of automation in dynamic‐control systems. The objective of human‐controlled LOA is to improve human‐machine performance by taking into account both operator and technological capabilities. Automation literature has shown that traditional automation can lead to problems in operator situation awareness (SA) due to the out‐of‐the (control) loop performance problem, which may lead to a negative impact on overall systems performance. Herein we address a standing paucity of research into LOA to deal with these problems. Various schemes of generic control system function allocations were developed to establish a LOA taxonomy. The functions allocated to a human operator, a computer, or both, included monitoring system variables, generating process plans, selecting an “optimal” plan and implementing the plan. Five different function allocation schemes, or LOAs, were empirically investigated as to their usefulness for enhancing telerobot system performance and operator SA, as well as reducing workload. Human participants participated in experimental trials involving a high fidelity, interactive simulation of a telerobot performing nuclear materials handling at the various LOAs. Automation failures were attributed to various simulated system deficiencies necessitating operator detection and correction to return to functioning at an automated mode. Operator performance at each LOA, and during the failure periods, was evaluated. Operator SA was measured using the Situation Awareness Global Assessment Technique, and perceived workload was measured using the NASA‐Task Load Index. Results demonstrated improvements in human‐machine system performance at higher LOAs (levels involving greater computer control of system functions) along with lower operator subjective workload. However, under the same conditions, operator SA was reduced for certain types of system problems and reaction time to, and performance during, automation failures was substantially lower. Performance during automation failure was best when participants had been functioning at lower, intermediate LOAs (levels involving greater human control of system functions). © 2000 John Wiley & Sons, Inc.     

Depth‐map generation for multi‐view autostereoscopic 3‐D displays based on the SIFT algorithm constrained by boundary

Abstract— A depth‐map estimation method, which converts two‐dimensional images into three‐dimensional (3‐D) images for multi‐view autostereoscopic 3‐D displays, is presented. The proposed method utilizes the Scale Invariant Feature Transform (SIFT) matching algorithm to create the sparse depth map. The image boundaries are labeled by using the Sobel operator. A dense depth map is obtained by using the Zero‐Mean Normalized Cross‐Correlation (ZNCC) propagation matching method, which is constrained by the labeled boundaries. Finally, by using depth rendering, the parallax images are generated and synthesized into a stereoscopic image for multi‐view autostereoscopic 3‐D displays. Experimental results show that this scheme achieves good performances on both parallax image generation and multi‐view autostereoscopic 3‐D displays.     

Temporal Visualization of Boundary‐based Geo‐information Using Radial Projection

This work is concerned with a design study by an interdisciplinary team on visualizing a 10‐year record of seasonal and inter‐annual changes in frontal position (advance/retreat) of nearly 200 marine terminating glaciers in Greenland. Whilst the spatiotemporal nature of the raw data presents a challenge to develop a compact and intuitive visual design, the focus on coastal boundaries provides an opportunity for dimensional reduction. In this paper, we report the user‐centered design process carried out by the team, and present several visual encoding schemes that have met the requirements including compactness, intuitiveness, and ability to depict temporal changes and spatial relations. In particular, we designed a family of radial visualization, where radial lines correspond to different coastal locations, and nested rings represent the evolution of the temporal dimension from inner to outer circles. We developed an algorithm for mapping glacier terminus positions from Cartesian coordinates to angular coordinates. Instead of a naive uniform mapping, the algorithm maintains consistent spatial perception of the visually‐sensitive geographical references between their Cartesian and angular coordinates, and distributes other termini positions between primary locations based on coastal distance. This work has provided a useful solution to address the problem of inaccuracy in change evaluation based on pixel‐based visualization [ [BPC*10] ].     

On the computation of the gap metric for LTV systems

In this paper, we consider the robust stabilization problem for linear discrete time-varying (LTV) systems using the gap metric. In particular, we show that the time-varying (TV) directed gap reduces to an operator with a TV Hankel plus Toeplitz structure. Computation of the norm of such an operator can be carried out using an iterative scheme involving a TV Hankel operator defined on a space of Hilbert–Schmidt causal operators. The “infimization” in the TV directed gap formula is shown to be, in fact, a minimum by using duality theory. The latter holds as well in the time-invariant case.     

A Modified TOPSIS Method for Obtaining the Associated Weights of the OWA‐Type Operators

The ordered weighted averaging (OWA) operator proposed by Yager and its some extensions have been extensively utilized to perform the mean‐type aggregation of individual preference relations in group decision making. An important issue in the theory of the OWA‐type operators is the determination of the associated weights. In the present paper, the technique for order preference by similarity to ideal solution is modified to propose a new method for generating the associated weights under the environment of a group of additive reciprocal matrices. First, a consistent additive reciprocal matrix is obtained from each additive reciprocal matrix. It is further used to generate an ideal additive reciprocal matrix by using the arithmetic averaging operator. Then, a similarity degree between every additive reciprocal matrix and the ideal one is defined. Based on the similarity degree, the associated weights are determined by making use of an exponential function and they show that more importance is given to that with more similarity degree. Finally, a numerical example is carried out to illustrate the given method.     

The simple and powerful yfx operator precedence parser

Dynamic operator declarations were introduced in the first Prolog system in the early 1970s. Today several other logical and functional languages adopt the Prolog style of dynamic operators. Despite this widespread use, there are no guidelines to assist the development of dynamic operator parsers. This paper presents an in‐depth study of the built‐in classical dynamic operator parser in Prolog systems. It is a powerful operator precedence parser covering pre/in/postfix operators; it is table‐driven, allowing operators to be redefined at run‐time; it is encoded in a simple, small and fast code; and, finally, it is widely used as a standard parser by the logic programming community. In a stepwise refinement approach (from specification to implementation and evaluation), this paper presents a detailed analysis of this parser. As an additional contribution, it is also shown how to encode the parser as a plug‐in component in procedural languages. Copyright © 2007 John Wiley & Sons, Ltd.     

Evaluation of whole-body vibration exposure experienced by operators of a compact wheel loader according to ISO 2631-1:1997 and ISO 2631-5:2004

Limited studies were carried out to evaluate the whole-body vibration (WBV) exposure experienced by operators of compact wheel loaders (CWLs) according to ISO 2631-1:1997. No study was carried out according to ISO 2631-5:2004. Therefore, evaluation of the WBV exposure using these two standards was carried out and the results were compared in this study. Tri-axial accelerations were measured at the seat/operator interface on a medium-sized CWL. The vibration measurements were carried out in ten different operations, such as the V-cycle and the driving over different road surfaces. In order to represent the daily work of the CWL, seven scenarios were proposed. These scenarios are comprised of V-cycle and driving over different distances. The evaluation result according to ISO 2631-1:1997 showed that the permitted daily exposure durations of six scenarios estimated using the vibration dose value (VDV) method did not exceed 8 h. For the pure V-cycle and the combination of V-cycle and slow driving, the permitted daily exposure durations estimated according to ISO 2631-1:1997 were shorter than those estimated according to ISO 2631-5:2004. However, for the combination of V-cycle and fast driving, the permitted daily exposure durations estimated according to ISO 2631-1:1997 were longer than those estimated according to ISO 2631-5:2004.Relevance to industryThis study evaluated the effect of WBV arising from a CWL on human health according to ISO 2631-1:1997 and ISO 2631-5:2004. Evaluation results show that boundaries of the health guidance caution zone in ISO 2631-5:2004 are higher than those in ISO 2631-1:1997.     

Image Space Rendering of Point Clouds Using the HPR Operator

The hidden point removal (HPR) operator introduced by Katz et al. [KTB07] provides an elegant solution for the problem of estimating the visibility of points in point samplings of surfaces. Since the method requires computing the three‐dimensional convex hull of a set with the same cardinality as the original cloud, the method has been largely viewed as impractical for real‐time rendering of medium to large clouds. In this paper we examine how the HPR operator can be used more efficiently by combining several image space techniques, including an approximate convex hull algorithm, cloud sampling, and GPU programming. Experiments show that this combination permits faster renderings without overly compromising the accuracy.     

A recursive operator allocation approach for assembly line-balancing optimization problem with the consideration of operator efficiency

This paper addresses an optimization model for assembly line-balancing problem in order to improve the line balance of a production line under a human-centric and dynamic apparel assembly process. As the variance of operator efficiency is vital to line imbalance in labor intensive industry, an approach is proposed to balance production line through optimal operator allocation with the consideration of operator efficiency. Two recursive algorithms are developed to generate all feasible solutions for operator allocation. Three objectives, namely, the lowest standard deviation of operation efficiency, the highest production line efficiency and the least total operation efficiency waste, are devised to find out the optimal solution of operator allocation. The method in this paper improves the flexibility of the operator allocation on different sizes of data set of operations and operators, and enhances the efficiency of searching for the optimal solution of big size data set. The results of experiments are reported. The performance comparison demonstrates that the proposed optimization method outperforms the industry practice.     

A recursive operator allocation approach for assembly line-balancing optimization problem with the consideration of operator efficiency

This paper addresses an optimization model for assembly line-balancing problem in order to improve the line balance of a production line under a human-centric and dynamic apparel assembly process. As the variance of operator efficiency is vital to line imbalance in labor intensive industry, an approach is proposed to balance production line through optimal operator allocation with the consideration of operator efficiency. Two recursive algorithms are developed to generate all feasible solutions for operator allocation. Three objectives, namely, the lowest standard deviation of operation efficiency, the highest production line efficiency and the least total operation efficiency waste, are devised to find out the optimal solution of operator allocation. The method in this paper improves the flexibility of the operator allocation on different sizes of data set of operations and operators, and enhances the efficiency of searching for the optimal solution of big size data set. The results of experiments are reported. The performance comparison demonstrates that the proposed optimization method outperforms the industry practice.