Quality Inspection Task in Modern Manufacturing

The development of numerically controlled machines, group technology, cellular manufacturing and just-in-time (JIT) production systems have revolutionized the way products are designed and manufactured. These technological and strategic advances have changed the role of human operators in the manufacturing environment. The highly specialized work force of the low-tech manufacturing system has evolved into the multi-skilled work force of the high- tech manufacturing system. Among the multiple tasks that an operator is expected to perform in advance manufacturing systems (AMS) are job scheduling, inventory planning, machine set-up, problem-solving and quality inspection. Throughout this evolution, human sensory detection capabilities have been a vital but often ignored component of the quality inspection task. Although automation is often employed to construct and assemble products within AMS, most inspections and quality checks are still done by human operators due to the inherent problems in machine vision and decision-making. While humans remain responsible for inspection, it has been widely accepted that the quality inspection task performed by humans is prone to error. Some studies indicate human inspectors typically find only ~80% of the defects. Despite the contributions of human factors research to the understanding of human performance in the quality inspection task, the manufacturing trend has been to design quality schemes that compensate for poor inspector performance instead of trying to improve it (Drury 1992)

Effects of Pacing When Using Material Handling Manipulators

Common manipulator-assisted materials handling tasks were performed in a laboratory simulation at self-selected and faster (paced) speeds. The effects of pacing on peak hand forces, torso kinematics, spine moments and forces, and muscle antagonism were determined, along with any influences of several task variables on these effects. The faster trials were performed 20% more rapidly than the self-paced trials. It was found that (a) achieving this level of performance required 10% higher hand forces and 5%-10% higher torso moments, (b) consistent torso postures and motions were used for both speed conditions, and (c) the faster trials resulted in 10% higher spine forces and 15% higher levels of lumbar muscle antagonism. On whole, these results suggest a higher risk of musculoskeletal injury associated with performance of object transfers at faster than self-selected speeds with and without a manipulator. Further analysis provided evidence that the use of manipulators involves higher levels of motor coordination than do manual tasks. Several implications regarding the use of material handling manipulators in paced operations are discussed. Results from this investigation can be used in the design, evaluation, and selection of material handling manipulators.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67067/2/10.1518_001872099779591240.pd

Effects of Aging on the Biomechanics of Slips and Falls

Although much has been learned in recent decades about the deterioration of muscular strength, gait adaptations, and sensory degradation among older adults, little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents. In general, the objective of this laboratory study was to investigate the process of initiation, detection, and recovery of inadvertent slips and falls. We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters, muscle strength, and sensory measurements. Forty-two young, middle-age, and older participants walked around a walking track at a comfortable pace. Slippery floor surfaces were placed on the track over force platforms at random intervals without the participants’ awareness. Results indicated that younger participants slipped as often as the older participants, suggesting that the likelihood of slip initiation is similar across all age groups; however, older individuals’ recovery process was much slower and less effective. The ability to successfully recover from a slip (thus preventing a fall) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals. Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults

Human performance reliability: On-line assessment using fuzzy logic

This paper presents an on-line approach to monitoring human performance in terms of conditional reliability when one is performing a task. Unlike traditional human reliability analysis, this approach develops a dynamic model that is able to cope with constantly changing conditions that affect operator performance. A fuzzy knowledge-based assessment approach is developed in order to deal with uncertainty and subjectivity associated with human performance assessment. This technology includes three main parts/functions: (i) on-line performance monitoring; (ii) real-time performance forecasting; and (iii) performance reliability assessment. The technology is demonstrated in real-time and provides timely conditioned reliability information regarding task success/failure. In general, this technology offers human reliability assessment under highly dynamic circumstances

Fuel Consumption Models for Tractor Test Reports

Five models for estimating fuel consumption for agricultural tractors with partial drawbar loads were compared. Data were collected from eight John Deere tractors, JD 7230R (e23), 7250R (e23), 7270R (e23), 7290R (e23), 8320R (16 speed), 7290R (IVT), 8345RT (IVT), 8370R (IVT), on the drawbar test track at the Nebraska Tractor Test Lab. The tractors were tested with seven load levels per speed at three different travel speeds as close as possible to 7.5, 10, and 13 km h-1. The IVT tractors were operated in auto mode, and the geared tractors were shifted up three gears and throttled back to the same travel speeds as obtained with the original gear (before shifting up) at maximum drawbar power. The seven loads were selected at 30%, 40%, 50%, 60%, 70%, 75%, and 80% of the drawbar pull at maximum power and rated engine speed at the selected travel speed. Model 1 (fuel consumption as a linear function of drawbar power on concrete), currently used in OECD Code 2, Section 4.4.8, resulted in a separate equation for each speed tested. When regression mean square errors were used for statistical comparison of the five fuel consumption models, model 5 (fuel consumption as a linear function of drawbar power and travel speed on concrete, and engine speed) was not significantly different from the model currently used in OECD Code 2, Section 4.4.8 (model 1, fuel consumption as a linear function of drawbar power on concrete, with separate equations specific to the three speeds tested). The simplest model (model 2), which used a single equation for fuel consumption as a linear function of drawbar power on concrete over the range of speeds tested, had significantly higher regression mean square errors compared to model 1 for half of the eight tractors tested. Model 5 (fuel consumption as a linear function of drawbar power and travel speed on concrete, and engine speed) was determined to be the best of the five models for estimating fuel consumption, with a single equation applicable over the range of speeds tested. Model 3 (fuel consumption as a linear function of drawbar power and travel speed on concrete) provided a statistically equivalent fuel consumption estimate to model 5 without the drawback of requiring an input value for engine speed

Interfollicular fibrosis in the thyroid of the harbour porpoise: An endocrine disruption?

Previous studies have described high levels of polychlorobiphenyls (PCB), polybrominated diphenylether (PBDE), toxaphene, ,p0-dichlorodiphenyltrichloroethane (DDT), and ,p0-dichlorodiphenyldichloroethylene (DDE) in the blubber of the harbour porpoise from the North Sea raising the question of a potential endocrine disruption in this species. In the present study, the thyroids of 57 harbour porpoises from the German and Danish (North and Baltic Seas), Norwegian, and Icelandic coasts have been collected for histological and immunohistological investigations. The number of follicles and the relative distribution of follicles, connective, and solid tissues (%) were quantified in the thyroid of each individual. Then, the potential relationship between the thyroid morphometry data and previously described organic compounds (namely, PCB, PBDE, toxaphene, DDT, and DDE) was investigated using factor analysis and multiple regressions. Thyroid morphology differed strongly between ampling sites. Porpoises from the German (North and Baltic Seas) and Norwegian coasts displayed a high percentage of connective tissues between 30 and 38% revealing severe interfollicular fibrosis and a high number of large follicles (diameter >200 lm). A correlation-based principal component analysis (PCA) revealed two principal components explaining 85.9% of the total variance. The variables PCB, PBDE, DDT, and DDE compounds loaded highest on PC1 whereas toxaphene compound loaded most on PC2. Our results pointed out a relationship between PC1 (PCBs, PBDE, DDE, and DDT compounds) and interfollicular fibrosis in the harbour porpoise thyroids. Such an association is not alone sufficient for a cause–effect relationship but supports the hypothesis of a contaminant-induced thyroid fibrosis in harbour porpoises raising the question of the longterm viability in highly polluted areas