Modification and evaluation of continuous roll prediction model for front drive mowers.

摘要

Front drive mowers are often operated on a slope where operators are subjected to potential continuous roll conditions. The continuous roll increases the opportunity of operator fatalities. The recently approved ASAE Standard S547 addressed a continuous roll prediction model for Roll-Over Protective Structure (ROPS) design. The existing model described in this Standard did not take into account the influence of the mower deck on the rollover behavior. This project involved evaluating the accuracy of the existing continuous roll model and modifying it to include the mower deck size, yaw and slide downhill.; The existing model was revised to include (1) the deck size, (2) yaw and (3) slide down the slope. Using the revised model, the minimum ROPS height required to stop the roll (critical ROPS height (CRH)) could be determined. The CRH predicted by the revised model was 2.50 m, and 2.63 m, with the deck transportation and working position, respectively, and ROPS in the regular position (the top of ROPS tilting backward). The CRH predicted by the revised model for the ROPS in the inverted position (the top of ROPS tilting forward) was 2.00 m.; In order to evaluate the accuracy of the revised model, field tests with a Deere F925 mower at ROPS height of 1.90 m, 2.22 m, 2.42 m, 2.55 m, and 2.67 m on a slope of 35 degree were conducted. For Deere F925 mower with the regular ROPS, the measured CRH were 2.55 m with the deck in transportation position (up) and 2.67 m with the deck in working position (down). For Deere F925 mower with the inverted ROPS, field tests showed a CRH of 2.03 m with deck in mowing position.; In order to quantitatively evaluate the revised model prediction accuracy, an accuracy factor (AF) (the critical ROPS height (CRH) predicted by the revised model divided by the measured critical ROPS height (CRH))(expressed as a percentage) was defined. The accuracy factor (AF) of the revised model for deck up, deck down, and inverted ROPS (98, 98, and 99%, respectively) indicates a better prediction than the original model (85, 83, and 82%, respectively). Field lateral upset tests showed that the revised model result was very close to the field test result.