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An ergonomic intervention method based on QOC Matrix the workers' voice was implemented in a study case. The diagnosis and analysis developed are used in improvement proposals for workstation redesign. The workers' voice resulting from reports of the employee' complaints and symptomatology was the base for a standardized method that comprises: (a) QOC questionnaire application, (b) risk factor categorization, (c) determination of unsafe and unhealthy ergonomic metrics, (d) figuring out the task content impact in the workers' body, and (e) work system diagnosis. Since workers' voice, the risk identification made included: (1) the task content linked to work method: repetitiveness associated with the sensor activation using the fingers and the repetitive movements include twist and the stretch of wrist, (2) workplace design regarding container height and injuries caused in wrists and elbows due to hits, (3) task developed regarding risk time exposition and workers position, and (4) workplace design regards to housing collector distance from filling area linked to workers position adopted for reach bags. Improvements included redesign of the workstation with a system of 90° exit discharge curve, one elevation system, and a photoelectric sensor in filling nozzle for automatic filling. As an improvement result, the activity called bags provision was eliminated from the task.

In this work, we propose a fuzzy inference as a decision support system built in the MATLAB Fuzzy Logic Designer for evaluating manual material handling risk conditions. The input variables for the fuzzy decision were: (1) the total time duration of the manual material handling in one shift of 450 min, with 3 h considered the maximal exposition time; (2) 25 kg as a maximal mass reference which should never be exceeded; (3) the repetitiveness of the manual material handling task through the shift considering as the maximal frequency of four lifts per min. Results of 135 earlier direct ergonomic evaluations made using the method proposed by the ISO 11228-1 were used as validator results, and called “expected results”. The experimentation intended to simulate an ergonomic evaluation in different boundary conditions of work and verify if the fuzzy interface could correctly replicate the results of the ergonomic evaluations. As validation, the list with the 135 expected results was compared against the evaluation made by the fuzzy logic interface, called “Work_Conditions”. From the comparison, only three evaluations (0.02%) differed with respect to the expected results. Consequently, it is concluded that the fuzzy interface can be used as a tool for automating the determination of manual material handling ergonomic risk levels, with great precision.

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