Multirobot coordination in pick-and-place tasks on a moving conveyor

This paper considers the problem of multirobot coordination in pick-and-place tasks on a conveyor band. The robot team is composed of identical robots with mutually exclusive, but neighboring workspaces. The products are fed in at one end of the band, move through each workspace sequentially until being picked up and are collected at the other end—if not picked up interim. Each robot has the same task—that is picking up and packaging as many products as possible. We propose an approach based on noncooperative game theory where each robot uses local observations of the conveyor band and their neighbors' actions in order to decide on its actions. The developed algorithm has been implemented and tested in a simulated manufacturing environment using Webots. Results obtained from the simulations are analyzed using a variety of statistical performance measures.     

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Abstract

Industrial robots often operate at high speed, with unpredictable motion patterns and erratic idle times. Serious injuries and deaths have occurred due to operator misperception of these robot design and performance characteristics. The main objective of the research project was to study human perceptual aspects of hazardous robotics workstations. Two laboratory experiments were designed to investigate workers' perceptions of two industrial robots with different physical configurations and performance capabilities. Twenty-four subjects participated in the study. All subjects were chosen from local industries, and had had considerable exposure to robots and other automated equipment in their working experience. Experiment 1 investigated the maximum speed of robot arm motions that workers, who were experienced with operation of industrial robots, judged to be ‘safe’ for monitoring tasks. It was found that the selection of safe speed depends on the size of the robot and the speed with which the robot begins its operation. Speeds of less than 51 cm/s and 63cm/s for large and small robots, respectively, were perceived as safe, i.e., ones that did not result in workers feeling uneasy or endangered when working in close proximity to the robot and monitoring its actions. Experiment 2 investigated the minimum value of robot idle time (inactivity) perceived by industrial workers as system malfunction, and an indication of the ‘safe-to-approach’ condition. It was found that idle times of 41 s and 28 s or less for the small and large robots, respectively, were perceived by workers to be a result of system malfunction. About 20% of the workers waited only 10 s or less before deciding that the robot had stopped because of system malfunction. The idle times were affected by the subjects' prior exposure to a simulated robot accident. Further interpretations of the results and suggestions for operational limitations of robot systems are discussed.     

Operator strategies in a dynamic environment in relation to an operator model

Results of an analysis of the cognitive activity of operators in controlling incidents in a Steam Generating Heavy Water Reactor in relation to a computer-based model of an operator (COSIMO, Cacciabue et al. 1992) are presented. The analysis focuses on information checking and actions to be taken in five incidents of varying levels of specification. Two experienced and two less-experienced operators participated in the experiments. Techniques of video and protocol analysis have been employed. Results indicate that operators use strategies in order to overcome the dynamic feature of incidents; in particular they break down problems into elementary problems, and they aim at maintaining a stable situation. A central characteristic is the importance of actions in terms of their timing and their results. Actions are carried out incrementally, and their effects then used as pointers to guide the course of future problem-solving and future actions. Problems may be postponed when they are not urgent, or when system latency does not allow an effect to be obtained following an action. Finally the paper discusses some elements that should be modified in order to increase the predictive capability of the COSIMO model.     

The influence of low frequency vibration on pilot performance (as measured in a fixed base simulator)

This report describes a study on the effects of low frequency vibration on pilot performance. Army pilots acted as subjects and flew simulated helicopter missions in a realistic fixed base simulator environment. While flying the two-hour missions pilots were exposed to vibration stimuli varying in frequency from 6 to 12 Hz and in amplitude from ±0·1 to ±0·3g (measured at the floor). Measurements were taken of the vibration tramsmissibility of the pilot's seat so that the vibration actually felt by the subject could be determined.

Missions involved transporting external loads in a simulated logistics environment. Performance was evaluated by measuring flight path deviations from prescribed en route, approach, and hover parameters.

The vibration stimuli used did not degrade performance. In fact, performance tended to improve with increased stress. It is hypothesized that this trend was due to motivation, i.e. as subjects felt the onset of fatigue they compensated by working harder and thus tended to improve their performance.

On about 6% of their scores pilots exhibited sudden lapses in their ability to respond to display indications. This resulted in poor scores in the midst of otherwise normal data. These lapses are probably of very short duration (seconds in length) and seem to occur randomly. This same effect was also observed in a previous study by the author. It may be possible that lapses of this type are related to so called ‘pilot error’ accidents. Further research is needed to verify this.     

面向龙芯3A体系结构的BLAS库优化

双精度普通矩阵乘法DGEMM是BLAS库中最核心的函数之一,大部分三级BLAS库函数的核心计算都是通过调用DGEM M来实现的.该文针对龙芯3A具有128位访存指令的特点,通过理论分析,找到了最佳的循环展开方式;针对龙芯3A的Cache替换策略(随机替换),通过使用地址交错技术,减少了Cache的冲突失效;针对龙芯3A访存带宽有限的问题,通过使用共享数据的任务划分方式,减少了数据访存量.优化后的DGEMM单核和多核运算速度均是性能最高的开源BLAS库(Goto-BLAS)的2倍多.     

Older Adults as Adaptive Decision Makers: Evidence From the Iowa Gambling Task.

Older adults process emotional information differently than younger adults and may demonstrate less of a negativity bias on cognitive tasks. The Iowa Gambling Task designed by A. Bechara, H. Damasio, D. Tranel, and A. R. Damasio (1997) has been used to examine the integration of emotion and cognition in a risky-choice decision task and may give insight into differences in the decision-making strategies in younger and older adults. Eighty-eight younger adults (18-34 years) and 67 older adults (65-88 years) completed the Iowa Gambling Task. Using a theoretical decomposition of the task designed by J. R. Busemeyer and J. C. Stout (2002), the authors found that both groups were successful at solving the task but used very different strategies that reflected each group's strength. For younger adults, that strength was learning and memory. For older adults, that strength was an accurate representation of wins and losses (valence). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maximizing Reward in a Non-Stationary Mobile Robot Environment

The ability of a robot to improve its performance on a task can be critical, especially in poorly known and non-stationary environments where the best action or strategy is dependent upon the current state of the environment. In such systems, a good estimate of the current state of the environment is key to establishing high performance, however quantified. In this paper, we present an approach to state estimation in poorly known and non-stationary mobile robot environments, focusing on its application to a mine collection scenario, where performance is quantified using reward maximization. The approach is based on the use of augmented Markov models (AMMs), a sub-class of semi-Markov processes. We have developed an algorithm for incrementally constructing arbitrary-order AMMs on-line. It is used to capture the interaction dynamics between a robot and its environment in terms of behavior sequences executed during the performance of a task. For the purposes of reward maximization in a non-stationary environment, multiple AMMs monitor events at different timescales and provide statistics used to select the AMM likely to have a good estimate of the environmental state. AMMs with redundant or outdated information are discarded, while attempting to maintain sufficient data to reduce conformation to noise. This approach has been successfully implemented on a mobile robot performing a mine collection task. In the context of this task, we first present experimental results validating our reward maximization performance criterion. We then incorporate our algorithm for state estimation using multiple AMMs, allowing the robot to select appropriate actions based on the estimated state of the environment. The approach is tested first with a physical robot, in a non-stationary environment with an abrupt change, then with a simulation, in a gradually shifting environment.     

Simulator-mediated acquisition of a dynamic control skill

Uses of stored skill-models to accelerate simulator-based real-time training in a control skill are discussed. A real-time coach must deliver advice at three levels: (1) what to do next, (2) what to watch for, and (3) what went wrong. Human learning and machine learning results are presented using different screen representations of a pole-and-cart balancing task.     

Investigation of Functional Hemispheric Asymmetry of Language in Tinnitus Sufferers.

The authors tested functional hemispheric asymmetry through word dichotic listening and lateralized lexical decision tasks in tinnitus patients and controls stimulated by a continuous tinnitus-like noise to test the influence of a tinnitus-like external stimulation. A classic right-ear advantage was shown in the auditory task for all but right-ear tinnitus patients, who performed as equally badly when the stimuli were presented to the right and left ears. Concerning the visual task, all participants demonstrated the expected right visual field advantage for word stimuli. Moreover, those who submitted to external stimulation demonstrated normal asymmetric patterns. These data suggest a specific effect of tinnitus on central processing and provide evidence for a functional reorganization induced by this auditory phantom perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

谈业主方在项目各阶段的重点管理任务——装载机项目管理工作简析

随着国内工程机械行业的发展,工程机械厂房建设规模越来越大,论文结合装载机项目管理的实际情况,简要分析了业主方在项目管理各阶段的重点管理任务,并对项目管理实施过程中部分管理做法的优劣做简要分析。