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Li Z.,Laboratory of Bioproduction Engineering | Mitsuoka M.,Laboratory of Bioproduction Engineering | Inoue E.,Laboratory of Bioproduction Engineering | Okayasu T.,Laboratory of Bioproduction Engineering | And 3 more authors.
Journal of the Faculty of Agriculture, Kyushu University | Year: 2015

A mathematical model for tractor dynamics was expanded by considering the rotatable tractor front end. The fundamental shortcoming of the simplified model was revealed by the loss of contact of the tire with a rigid horizontal surface in an obstacle-passing case. Further shortcomings of the simplified model arise from aspects of the motion and vibration characteristics. The improved model provides a better and more realistic representation of the tire-ground contact condition and is applicable to tractors on lateral slopes. The independent roll motions of the two main tractor parts (the front end and main body) significantly reduce the motions of the tractor and thus increase its stability. Furthermore, the effects of the forward tractor speed and obstacle height were studied for a tractor on a 10° lateral slope. By analyzing the motion amplitude and tire-ground contact condition, the tractor speed and obstacle height parameters associated with danger and risk were evaluated. The results suggest the greater capability of the improved model to predict tractor dynamic response in Phase I overturn.


Li Z.,Laboratory of Bioproduction Engineering | Mitsuoka M.,Laboratory of Bioproduction Engineering | Inoue E.,Laboratory of Bioproduction Engineering | Okayasu T.,Laboratory of Bioproduction Engineering | And 3 more authors.
Journal of the Faculty of Agriculture, Kyushu University | Year: 2015

Tractor stability predominantly determines operator's safety. For a tractor parking on lateral slopes, overturning accidents have been frequently discussed using mathematical models. While the existing static models remarkably contribute tractor overturning mechanisms, few of them have considered the stability from the perspective of tractor sideslip. In our study, a relatively precise quasi-static model presented recently was adopted as the base model. We expanded it by introducing potential tractor sideslips. While the original model pointed out the lateral slope angle as the main factor influencing tractor overturns, we investigated tractor slipping stability under the influences of the slope angle and the coefficient of friction. The dimensional parameters of the example tractor for simulation were set the same as those in the original work. It was found that the allowable friction forces of both the front and rear tires primarily depended on the coefficient of friction rather than the slope angle. By comparing the surfaces of the allowable friction forces and the corresponding friction forces, tractor slipping thresholds for the front and rear tires were identified. Caution areas implying certain ground conditions that will definitely cause tractor sideslip were marked accordingly. The results shown in this study provide a relatively comprehensive way to understand tractor static stability when both tractor sideslip and overturn are concerned.


Kim B.-J.,Laboratory of Bioproduction Engineering | Kim B.-J.,Tong Yang Co. | Kang Y.-S.,Laboratory of Bioproduction Engineering | Kang Y.-S.,Tong Yang Co. | And 8 more authors.
Journal of the Faculty of Agriculture, Kyushu University | Year: 2015

This study examined the performance of the separating system of a self-propelled peanut harvester by analyzing the relationship between a shaking screen and rotational speeds of winnowing. The shaking screen was manufactured to have rotational speeds of 370, 470, 570 rpm and winnowing was manufactured to have rotational speeds of 1,500, 1,760, 2,020 rpm by adjusting the pitch circle diameter of each pulley. The sample was prepared based on the yields of an actual self-propelled peanut harvester and analyzed with Statistical Analysis Software after measuring the weight of peanuts and stems. The stem separation ratio was high as 95.3% when rotational speeds were 570 rpm (shaking screen) and 2,020 rpm (winnowing). The peanut loss ratio was low as 0% when rotational speeds were 370 rpm (shaking screen) and 1,500 rpm (winnowing). The results indicated that the stem separation ratio was improved with high rotational speeds of shaking screen and winnowing; the peanut loss ratio was reduced with low rotational speeds of shaking screen and winnowing. However, the rotational speed of winnowing did not influence on the peanut loss ratio; as a result, separation performance was improved with low rotational speed of shaking screen and high rotational speed of winnowing. Low rotational speed of shaking screen, however, may cause congestion during process, thus follow-up studies are needed.

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