[6-1015-D] Other Categories (3)

[6-1015-D-02] Driving Force Control for Suppression of Tractor’s Dynamic Pitching Angle

*Yuya Aoyagi¹, Masami Matsui² (1. Tokyo University of Agriculture and Technology (Japan), 2. Utsunomiya University(Japan))

Keywords:Tractor, Traveling simulation, Torque control, Prevent accident, Suppression for attitude angle

In recent years, Japan’s agricultural industry has had the highest mortality rate among all other industries. The agricultural industry has also become one of the most dangerous in other countries, and this is becoming a serious problem worldwide. In Japan, the highest number of fatalities (approximately 100 fatalities per annum) result from accidents involving tractors, with the most common being rollovers. Overturning accidents can occur either when a tractor is traveling along sloped, rough terrain because the uneven road surface increases the dynamic pitch angle beyond the overturning limit, or when the operator loses control as a result of the front wheels bouncing. To prevent these accidents, it is important to control the pitch angle when traveling along such terrain. In a previous study on the attitude stabilization of vehicles while they are being driven, attitude control technology using driving torque was developed. This technology improves riding comfort in automobiles traveling along paved roads. By applying such control to a tractor, it is expected that pitching overturn accidents can be prevented. In this scenario, it is important to confirm the dynamic effect on the pitching suppression by driving torque control. Overall, in this study, a three degrees-of-freedom, vertical, pitching, and forward/backward movement behavior model of a tractor that considers the influence of the driving force on the pitch angle was developed. The reaction force that each wheel received from the road surface was calculated, and numerical calculations were performed for the acceleration along each degree of freedom. The feedback control system had a static pitch angle on the input terrain as the target value, which was applied to the model. In the control system, using PID control, the driving force was calculated from each term (proportional, integrated, and derivative) of deviations, which consist of the difference between the target value and the dynamic pitch angle. The coefficients of the PID system were determined to become effective for this condition. The limits of the driving force were set according to the specification value of the tractor engine power and the power required for slope climbing. Driving simulation using the topographic information on a site of an actual tractor overturn accident was performed with both the driving-force control model and the constant-speed traveling model. The suppression of the pitch angle by controlling the driving force was examined through a comparative analysis of the results. The pitch angle of the driving-force control model was smaller than that of the constant-speed traveling model, enabling travel along the terrain. Thus, dynamic pitch angle control was implemented and validated. The maximum pitch angle of the driving-force control model was approximately 10% smaller than that of the constant-speed traveling model. In addition, a driving force corresponding to the attitude was generated within the usable driving-force range. Pitch angle suppression was confirmed by controlling the driving force. In our study, driving simulation using topographical information on the actual accident site was conducted to examine the suppression of the dynamic pitch angle by driving-force control. Consequently, the pitch angle of the driving-force control model enabled travel along the terrain. The maximum pitch angle of the control model was approximately 10% smaller than that of the constant-speed traveling model. The results suggest that the attitude angle can be suppressed by driving-force control to prevent tractor rollover accidents.