• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.379-392
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• 1996

A mathematic model was developed for the simulation of sideways overturning of agricultural tractors on slopes. The overturning motion was described as a combination of the rotational motions with respect to the first and second tipping axes using the principle of conservation of angular mementum. A stability criterion was also established in terms of angular acceleration of tractor about the second tipping axis. Verification of the proposed model was provided by comparing the stability boundaries predicted by computer simulation with those observed experimentally for an equivalent 1/6 scaled mode tractor. A good agreement was shown between the simulation and experimental results.

• Journal of Biosystems Engineering
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• v.15 no.4
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• pp.298-309
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• 1990

A mathematical model was developed to simulate sideways overturning of agricultural tractor-trailer systems. Sideways overturn of a tractor-trailer system was described by oscillatory motions of the tractor with respect to the first and second tipping axes, and of the trailer with respect to the drawbar hitch point when either the tractor or trailer rides over an obstacle on slopes. By a computer simulation, critical slope angles of the ground on which the tractor-trailer system is likely to sideways overturn were evaluated under the given operational conditions. Validity of the proposed mathematical model was proved by comparing the results of computer simulation and experiment with a model tractor-trailer system. A close agreement was observed between the two results.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1997.06c
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• pp.25-31
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• 1997

• Journal of Biosystems Engineering
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• v.27 no.3
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• pp.185-194
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• 2002

The objective of this study was to analyze a stability of sideways overturning of a forwarder developed by the Forestry Research Institute. The stability analysis was conducted using a multibody dynamic analysis program. VisualNastran Desktop. A solid model of the forwarder was constructed and its physical properties such as mass, mass center and mass moment of inertia were determined on 3D CAD modeler of the Solid Edge 8.0. 3D simulations of sideways overturning of the forwarder were also performed on the Visual Nastran using the solid model when it traveled across the slope and traversed over an up-hill side obstacle. Stability comparison between a bogie-wheeled and a 6-wheeled forwarders was also made and found that the bogie-wheeled forwarder was more stable than the 6-wheeled one on slopes. The safety speeds of the forwarder predicted by the simulation under various conditions can be used as a guideline for safe operations of forwarders in mountainous area. The technique of using a solid model for the sability analysis can also be applied successfully to other vehicles like agricultural tractors, loaders and construction equipments.

• Journal of Biosystems Engineering
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• v.32 no.2 s.121
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• pp.69-76
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• 2007

This study was conducted to evaluate the sideways overturning stability of side loaded mini-forwarder. The model of a prototype was developed using a 3D CAD modeler and the performance was experimentally validated. The prototype model was run on the multibody dynamic analysis program, RecurDyn 6.0, to simulate motions when the model traversed over a circular bump on a inclined ground surface. The simulation was performed at a constant forward speed of 1.85 km/h under the loaded and unloaded conditions. The forward direction was also controlled to vary from 0 to 360 degrees with an increment of 10 degrees. Results of the simulation showed safe regions in which the mini forwarder could travel safely in terms of direction and slope of the ground. Even when the mini-forwarder was loaded by 20 logs of 3.6 m long and 12 cm diameter, it traveled safely within the ground slopes of 1 to 45 degrees by directions.

• Journal of Korean Society of Forest Science
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• v.104 no.1
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• pp.98-103
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• 2015

This study was conducted to analyze the running stability of a semi-crawler type mini-forwarder. The running stability analysis was performed by using a dynamic analysis program, RecurDyn. Physical properties of the semi-crawler type mini-forwarder was performed by using 3D CAD modeler, AutoCAD 3D. As a result from the computer simulation of stationary sideways overturning, it was found that the semi-crawler type mini-forwarder runs safely on a road with a slope not bigger than $20^{\circ}$ regardless whether it is empty or loaded, but in case of a road with a slope bigger than $20^{\circ}$, it is assumed that it is difficult for the car to run safely due to some dangers. In addition, it was found that the critical slope of its sideways overturning gets much smaller when empty since the location of its gravity center is elevated and much higher when it is loaded. As a result from the computer simulation of its hill-climbing ability, since the running speed is unstable in case of a road with a vertical slope not smaller than $28^{\circ}$, it is assumed that it is safe to drive it on a road with a slope not bigger than $28^{\circ}$. Taking a look at the result from an analysis of the running safety when it passes an obstacle, it was observed that a front tire comes off the ground when the running speed of the car is 5 and 4 km per hour respectively when it is empty and loaded while the gravity center of the front tire is watched. When taking a look at the changes in the location of the gravity center of the rear wheel crawler shaft, it was not found that the shaft comes off the ground at the test speeds both when it is empty and loaded.

• Journal of Biosystems Engineering
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• v.42 no.4
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• pp.235-241
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• 2017

Purpose: It is to develop an agricultural three-directional dumping vehicle that can help farmers reduce intensive labor when carrying heavy loads and for easy dumping. In addition, a novel mechanism was applied for controlling the direction of the tilting cargo box by using a single hydraulic cylinder and simple apparatus. The overturning safety was analyzed to provide safe-use ground slope region of the vehicle to be used at upland fields and orchards. Methods: The developed three-directional dumping vehicle was constructed using a cargo box, vehicle frame, driving components, lifting components, and controller. The novel mechanism of controlling the dumping direction involves the operation of two latching bars, which selectively release or collapse the connecting edge between the vehicle frame and cargo box. A multibody dynamics analysis software (RecurDynV8R5) was used to determine the safe-use ground slope area when tilting the cargo box at slopes. A computer analysis was conducted by increasing the ground slope while rotating the vehicle when the cargo box comprised loads of 300 and 500 kg and stacking heights of 40 and 80 cm, respectively. Results: The three-directional dumping vehicle was successfully manufactured, and the cargo box was tilted at $37^{\circ}$ and $35^{\circ}$ for dumping forward and sideways. The latching bars were manually and selectively collapsed with the vehicle frame to control the dumping direction. When forward dumping, the safe-use ground slope was over $20^{\circ}$ in all vehicle directions and loaded conditions. Conclusions: A three-directional dumping vehicle was developed to reduce labor-intensive work in the farming environment. The user can easily control the dumping direction by using the control panel. The vehicle was safe to be used in most of the Korean upland fields and orchards (area over 96%) for the forward dumping.