Hybrid control of a two-arm robot for complex tasks

For many coordinated tasks, a two-arm robot cannot be properly controlled by using a simple position control scheme and therefore requires a certain form hybrid control. Uchiyama and Dauchez recently proposed a symmetric hybrid position/force scheme for the manipulation of rigid objects rigidly held. The main results of this theory are summarized in this paper, and the limitations are pointed out. Several examples in which the relative motion of the end effectors cannot be neglected are presented: manipulation of rigid objects non-rigidly held, deformation of a flexible object, and assemblies of two objects “in space”. These tasks are analyzed and attempted control schemes are given for each of them. The dynamic effects are always neglected in this preliminary theoretical approach. An experimental setup built around two six axis PUMA arms and a parallel processing controller has been installed in order to validate our theoretical results. The hardware and software of this setup are also briefly described in this paper.     

Seated work postures for manual,visual and combined tasks

An awkward and static work posture has been recognized as a risk factor for workrelated musculoskeletal problems. The objective of this study was to investigate some of the factors that can influence the posture adopted during work and in particular aspects of the task and how their influence is affected by work height. Three types of task were studied: a peg-hole assembly task, which was largely manual with very little visual component; a visual character identification task; and a combination of the two. Two levels of difficulty were included in each of the manual and visual elements. Postures of the head/neck, trunk and arm were recorded during performance of these tasks. The results showed that type and difficulty of task do influence the posture adopted, and that some of the postural responses (although complex) are predictable so that poor postures could be improved by adjusting task design in addition to workplace layout.     

Seated work postures for manual, visual and combined tasks.

An awkward and static work posture has been recognized as a risk factor for work-related musculoskeletal problems. The objective of this study was to investigate some of the factors that can influence the posture adopted during work and in particular aspects of the task and how their influence is affected by work height. Three types of task were studied: a peg-hole assembly task, which was largely manual with very little visual component; a visual character identification task; and a combination of the two. Two levels of difficulty were included in each of the manual and visual elements. Postures of the head/neck, trunk and arm were recorded during performance of these tasks. The results showed that type and difficulty of task do influence the posture adopted, and that some of the postural responses (although complex) are predictable so that poor postures could be improved by adjusting task design in addition to workplace layout.     

X10-FT: Transparent fault tolerance for APGAS language and runtime

The asynchronous partitioned global address space (APGAS) model is a programming model aiming at unifying programming on multicore and clusters, with good productivity. However, it currently lacks support for fault tolerance (FT) such that a single transient failure may render hours to months of computation useless.     

Vision at work visual defect and the visual demand of tasks

Several related studies of visual tasks in a large communications undertaking have revealed much defect of vision and many sources of visual fatigue and inefficiency. The nature of visual fatigue is described briefly and a programme to facilitate visual tasks is outlined.     

Dual-key-binding cancelable palmprint cryptosystem for palmprint protection and information security

Biometric cryptosystems and cancelable biometrics are both practical and promising schemes to enhance the security and privacy of biometric systems. Though a number of bio-crypto algorithms have been proposed, they have limited practical applicability because they lack of cancelability. Since biometrics are immutable, the users whose biometrics are stolen cannot use bio-crypto systems anymore. Cancelable biometric schemes are of cancelability; however, they are difficult to compromise the conflicts between the security and performance. By embedded a novel cancelable palmprint template, namely “two dimensional (2D) Palmprint Phasor”, the proposed palmprint cryptosystem overcomes the lack of cancelability in existing biometric cryptosystems. Besides, the authentication performance is enhanced when users have different tokens/keys. Furthermore, we develop a novel dual-key-binding cancelable palmprint cryptosystem to enhance the security and privacy of palmprint biometric. 2D Palmprint Phasor template is scrambled by the scrambling transformation based on the chaotic sequence that is generated by both the user's token/key and strong key extracted from palmprint. Dual-key-binding scrambling not only has more robustness to resist against chosen plain text attack, but also enhances the secure requirement of non-invertibility. 2D Palmprint Phasor algorithm and dual-key-binding scrambling both increase the difficulty of adversary's statistical analysis. The experimental results and security analysis confirm the efficiency of the proposed scheme.     

Extraction and fusion of partial face features for cancelable identity verification

In this paper, we propose to extract localized random features directly from partial face image matrix for cancelable identity verification. Essentially, the extracted random features consist of compressed horizontal and vertical facial information obtained from a structured projection of the raw face images. For template security reason, the face appearance information is concealed via averaging several templates over different transformations. The match score outputs of these cancelable templates are then fused through a total error rate minimization. Extensive experiments were carried out to evaluate and benchmark the performance of the proposed method based on the AR, FERET, ORL, Sheffield and BERC databases. Our empirical results show encouraging performances in terms of verification accuracy as well as satisfying four cancelable biometric properties.     

Psychological evaluation and design of work tasks: two examples

Abstract

Practical experience with flexible production automation has provoked rising demands for human oriented job design. Prospective evaluation of work tasks based on status-quo analyses with the psychological instrument VERA, developed for the assessment of the available scope of action in fulfilling the task, has led to design proposals concerning technical and organizational aspects as well as questions of training and retraining. Procedure and results are shown by presenting two case studies dealing with a small flexible manufacturing system and a planned ‘production island’.     

Random area-perimeter method for generation of unimodal and multimodal cancelable biometric templates

Applied Intelligence - In recent times, biometric based authentication systems have seen a tremendous growth in various applications. However, if databases in multiple applications are created...     

A two-phase mathematical-programming heuristic for flexible assignment of activities and tasks to work shifts

In the service industry, workers perform work shifts and are assigned to interruptible activities and uninterruptible tasks during their shifts. The work shifts of regular employees are often established several weeks in advance of the operations when the activity and task demands are still uncertain. Just a few days before the operations when these demands are unveiled with more certainty, the planned schedules can be slightly modified and on-call temporary employees can be scheduled to satisfy the demands as best as possible. As acceptable modifications, extending the planned shifts and moving workers’ meal breaks are considered. In this paper, we are interested in the scheduling problem encountered in this second step, which also involves assigning activities and tasks to the scheduled work shifts. To produce good-quality solutions in fast computational times for large-sized instances, we develop a two-phase heuristic. In the first phase, an approximate mixed-integer programming model is used to suggest temporary shifts and extensions to regular shifts and to schedule and assign tasks. In the second phase, a column-generation heuristic embedded in a rolling horizon procedure determines the final shifts and assigns activities to them. Computational results obtained on randomly generated instances are reported to evaluate the validity of the proposed solution method.     

Ergonomic evaluation of work table for waste sorting tasks using digital human modelling

Waste sorting facilities rely heavily on plentiful human labour, and the lack of adequately designed work systems leads to musculoskeletal disorders among the workers. The present research explores the ergonomic design aspects of a cost-effective intervention, a work table for waste sorting in developing countries. This study evaluates the appropriate range of work height for the sorting tasks and proper location of hoppers to drop the sorted items. The ergonomic assessment was conducted by simulating postures involved in sorting tasks in a virtual environment and performing a biomechanical evaluation of the static postures by digital human modelling. Thirty male subjects from Indian population simulated the postures of sorting tasks. The compressive force at L4/L5 intervertebral disc, shoulder flexion moment, shoulder abduction moment, and elbow flexion moment were taken as the indicative parameters of the subject's physical workload. The appropriate table height was marginally lower than the elbow height of the subject and within 4 cm. The preferred hopper position was on the floor adjacent to the worker compared with the hopper on the top of the table.     

Exploring physical exposures and identifying high-risk work tasks within the floor layer trade

Introduction

Floor layers have high rates of musculoskeletal disorders yet few studies have examined their work exposures. This study used observational methods to describe physical exposures within floor laying tasks.

Methods

We analyzed 45 videos from 32 floor layers using Multimedia-Video Task Analysis software to determine the time in task, forces, postures, and repetitive hand movements for installation of four common flooring materials. We used the WISHA checklists to define exposure thresholds.

Results

Most workers (91%) met the caution threshold for one or more exposures. Workers showed high exposures in multiple body parts with variability in exposures across tasks and for different materials. Prolonged exposures were seen for kneeling, poor neck and low back postures, and intermittent but frequent hand grip forces.

Conclusions

Floor layers experience prolonged awkward postures and high force physical exposures in multiple body parts, which probably contribute to their high rates of musculoskeletal disorders.     

Postural analysis of paramedics simulating frequently performed strenuous work tasks

Paramedics who perform emergency rescue functions are highly susceptible to musculoskeletal injuries. Through an interview and survey process firefighters, many of whom are cross-trained paramedics in a consortium of 14 suburban fire departments, identified and rated tasks that were perceived to be both strenuous and frequently performed. The objective of the current study was to describe the working postures and the forces applied as firefighter/paramedics (FF/Ps) simulated specific roles within the following tasks identified by the survey: (1) transferring a patient from a bed to a stretcher using bedsheets, (2) transferring a patient from the ambulance stretcher to a hospital gurney, (3) carrying a victim down a set of stairs and around a landing using a stairchair, (4) carrying a victim down a set of stairs and around a landing using a backboard, and (5) carrying a victim down a set of stairs using a stretcher. Ten two-person teams of FF/Ps participated and were videotaped to obtain postural data for the upper and lower extremities as they performed each role in the simulated two-person tasks. Trunk postures were obtained using lumbar motion monitors. Static hand forces were estimated using a hand-held dynamometer at the most physically demanding points for each role within each task. The postural and force data were averaged across subjects performing identical roles to quantify the postures assumed by the FF/Ps at the most strenuous moments during task performance. Based on these analyses we concluded that: (1) when transferring victims from a bed to a stretcher the FF/P on the bed was able to maintain an upright and more stable posture by standing as opposed to kneeling, (2) an interface board should be used to reduce the frictional forces when transferring victims from a bed to a stretcher or from a stretcher to a gurney, thereby reducing the need to lift the victim with flexed torsos and/or shoulders, and (3) equipment and training that encourages the FF/P in the leader role to walk facing forward during victim transport, especially when descending stairs, potentially results in safer transit.     

Partial DCT-based cancelable biometric authentication with security and privacy preservation for IoT applications

Multimedia Tools and Applications - Biometric authentication is being vastly used in identity verification for several IoT applications, nowadays. The security and privacy of the...     

Biomechanical analyses of paramedics simulating frequently performed strenuous work tasks

Firefighters performing emergency rescue functions are at an elevated risk of musculoskeletal injuries. The objective of the current study was to analyze the biomechanical stresses placed on the body based on simulations of the following strenuous and frequently performed emergency rescue tasks: (1) transferring a patient from a bed to a stretcher using bedsheets, (2) transferring a patient from the ambulance stretcher to a hospital gurney, (3) carrying a victim down a set of stairs and through a landing using a stairchair, (4) carrying a victim down a set of stairs and through a landing using a backboard, and (5) carrying a victim down a straight set of stairs using a stretcher. Postural data were analyzed using the University of Michigan's Three-Dimensional Static Strength Prediction Program and the relative risk of low back disorder (LBD) was quantified using the trunk motion model published by Marras et al. (1993, spine 18, 617-628). Peak compression values and the probabilities from the Marras et al. (1993) model indicated that the most hazardous tasks performed as part of this simulation included pulling a victim from a bed to a stretcher, the initial descent of a set of stairs when using the stretcher, and lifting a victim on a backboard from the floor. Overall, the two models were well correlated in their assessment of the task components modelled (r = 0.78). These data indicate where engineering changes to equipment regularly used by emergency rescue personnel would have the greatest impact in reducing the risk of musculoskeletal injury.     

A capacity sharing and stealing strategy for open real-time systems

This paper focuses on the scheduling of tasks with hard and soft real-time constraints in open and dynamic real-time systems. It starts by presenting a capacity sharing and stealing (CSS) strategy that supports the coexistence of guaranteed and non-guaranteed bandwidth servers to efficiently handle soft tasks’ overloads by making additional capacity available from two sources: (i) reclaiming unused reserved capacity when jobs complete in less than their budgeted execution time and (ii) stealing reserved capacity from inactive non-isolated servers used to schedule best-effort jobs.CSS is then combined with the concept of bandwidth inheritance to efficiently exchange reserved bandwidth among sets of inter-dependent tasks which share resources and exhibit precedence constraints, assuming no previous information on critical sections and computation times is available. The proposed Capacity Exchange Protocol (CXP) has a better performance and a lower overhead when compared against other available solutions and introduces a novel approach to integrate precedence constraints among tasks of open real-time systems.     

Dynamic estimation of worker reliability in crowdsourcing for regression tasks: Making it work

One of the biggest challenges in crowdsourcing is detecting noisy and incompetent workers. A possible way of handling this problem is to dynamically estimate the reliability of workers as they do work and accept only those workers who are deemed to be reliable to date. Although many approaches to dynamic estimation of rater reliability exist, they are often only appropriate for very specific categories of tasks, for example, only for binary classification. They also can make unrealistic assumptions such as requiring access to a large number of gold standard answers or relying on the constant availability of any rater. In this paper, we propose a novel approach to the dynamic estimation of rater reliability in regression (DER³) using multi-armed bandits. This approach is specifically suited for real-life crowdsourcing scenarios, where the task at hand is labelling or rating corpora to be used in supervised machine learning, and the annotations are continuous ratings, although it can be easily generalised to multi-class or binary classification tasks. We demonstrate that DER³ provides high-accuracy results and at the same time keeps the cost of the rating process low. Although our main motivating example is the recognition of emotion in speech, our approach shows similar results in other application areas.     

The development and application of psychophysical methods in upper-extremity work tasks and task elements

This paper examines an approach to modeling the relationship between perceived acceptable work exposures and physical stressors in upper-extremity tasks using psychophysical methods. Several years of laboratory-based studies and results from a variety of simulated work tasks and task elements are summarized. The original impetus of these studies was founded in the pioneering work and successful application of psychophysical methods applied to manual materials handling tasks (e.g., lifting) generally beginning in the 1960s and 1970s. This approach provided unique and feasible solutions to work design problems involving exposure to the hazard of cumulative trauma. Presently, these methods were adapted to studying common upper-extremity tasks and task elements. Results provide conclusive evidence of the impact of required posture, force, gender and other variables on acceptable task frequency. These results and the psychophysical method in general, may be particularly helpful in establishing realistic and reasonable work design guidelines when workers are exposed to multiple, simultaneous hazards such as force, frequency, with deviated posture, etc, and in the absence of well-defined biomechanical or physiological-based models. Finally, a review of psychophysical theory and methods which can be applied to a wide range of occupational activities is provided.