Dynamic Characteristics of Tractors mounted with Rotary Tillers (I)

Measurement and Analysis of Fundamental External Forces

Abstract

The rotary tillage torque fluctuates considerably in the short period. The dynamic behavior of the tractors caused by this torque fluctuations was investigated from the view point of the design engineering. The results were as follows;
1) The variations of the forward acceleration of the tractors were caused mainly by that of the rotary tillage torque in the low frequency range. The peak-to-peak amplitude of the travel speed was less than 6cm/sec for the ordinary travel speeds.
2) The frequency components of f₀ and 1/2f₀ were dominant for the variations of rear axle torque. (f₀: rotational frequency of the rotary axle, H_z) The fluctuations of the tractor braking force produced at the rear wheels were caused mainly by those of the travel speed.
3) The frequency component of 2f₀ was dominant for the variation of the vertical force on the front wheels. The peak-to-peak amplitude was less than 60kg which was about 1/6 of the static vertical force on them.
4) The frequency responses between the input rotary tillage torque and the output vertical force acting on the front wheels and the rear axle torque were estimated using the spectral analysis on the condition that the rotary tillage system was approximately linear and the disturbances entering the rotary tillage system were negligiably small.
5) The variations of the horizontal force F_H, which were transmitted to the tractors through the three point linkage, were approximately equal to those of the horizontal component of the rotary tillage resistances. The variations of the vertical conponent F_V were much smaller than those of the vertical component of the rotary tillage resistances.
6) The concept of coefficient of rolling resistance could not be applied to the dynamic relations between the vertical force and the rolling resistance acting on the depth wheels. Instead, they were expressed by Equation (1).