Application of an Integrated Ergonomic Indicator (IEI) in evaluating forest machines

ABSTRACT Ergonomic evaluations of forest machines are carried out in isolation due to the lack of an adequate method that makes it possible to correlate the ergonomic variables simultaneously. The aim of this study was to evaluate the ergonomic performance of certain forest machines by using the Integrated Ergonomic Indicator (IEI), capable of correlating ergonomic variables simultaneously. Vibration, noise, heat, illuminance, posture, repeatability, visibility and productivity were obtained from a feller buncher, harvester, forwarder, skidder and processor machines in two work shifts with 24 operators. The ergonomic data were subjected to cluster analysis and standardized by their deviations from the average, being subjected to multivariate factor analysis to determine influencing factors in the composition of the IEI. The indicator for each factor was multiplied by the variance explained for each factor, with the result divided by the total explained variance. The values remained around 0 and the higher the result, the worse the ergonomic condition. The results showed that the variables that most negatively influenced the machines were vibration, noise and lateral visibility which were related to each other. The worst machine under the ergonomic aspect was the skidder, with an IEI of 2.82 and 1.60 for day and night shifts, respectively, caused by shocks and bumps in the work route, and also due to the operators spending a long time with their neck rotated. The best machines were the 8×8 harvester and the forest processor at night, with an IEI of −1.36 and −0.96, caused by vibration, noise and neck with little rotational deviation.