Foot placements are critical determinants of musculoskeletal loading in manual materials handling (MMH) tasks because of their effects on torso and upper-extremity posture. In spite of this importance, current ergonomic assessment tools lack valid models to predict the foot locations workers will chose. To address this need, a new comprehensive approach for modeling stepping behavior in MMH tasks was developed, based on field observations and a laboratory study. A method for qualitatively describing stepping strategies, the Lexical Transition Classification System (L-TRACS), was developed from observations of experienced operators performing MMH transfer tasks in an automotive assembly plant. Based on the field observations, the patterns of foot motions during object transfer tasks were hypothesized to be usefully described by a hybrid discrete/continuous model structure that predicts both strategies (behaviors) and the scaling of step placements within behaviors based on statistical analyses of laboratory data. A similar set of stepping behaviors was observed for both the laboratory and plant study. The four most frequently utilized strategies in the laboratory study accounted for 81% of the behaviors observed in the plant study. The results suggest that a majority of the stepping progressions used for MMH transfer tasks can be represented by a concise set of scalable behaviors that are a significant subset of those observed for everyday activity. The Transition Stepping (TRANSIT) model uses a new Quantitative Transition Classification System (Q-TRACS) that defines step placements during object pickups and deliveries. Multiple regression models were developed for five unique stepping strategies. The placement and orientation of the terminal stance lead foot is predicted moderately well by subject and task attributes (R2 of 0.69, 0.43, and 0.68 for lateral placement, fore-aft placement, and foot orientation, respectively). An Integrated Stepping Model (ISM) is proposed that integrates the TRANSIT model with a model of gait using a flexible scaling structure to mediate between gait and transition stepping. An example of gait following a straight-line path is presented under the Q-TRACS formulation, allowing the ISM to be considered as a general framework for representing foot placements for volitional tasks. The combined results provide a foundation for the future development of biomechanical based models of acyclic stepping.Ergonomics, 47(13): 1365a 1385. Kuorinka, I., Lortie, M., and Gautreau, M. ( 1994). Manual handling in warehouses: the illusion of correct working postures. Ergonomics, 37(4):655-661 . Lockett, J., Assmann, E., Green, R., Reed, M., Raschke, anbsp;...
|Title||:||Classification and Modeling of Acyclic Stepping Strategies Used During Manual Material Handling Transfer Tasks|
|Author||:||David William Wagner|
|Publisher||:||ProQuest - 2008|