Dynamic Analysis of Rotary Tillage

Abstract

Greater stress should be placed on the dynamic analysis of tractors during rotary tillage.
To clarify these pending problems substantially three kinds of analysis were conducted under tropical conditions: 1) Power distribution during tractor rotary tiller operation. 2) PTO torque distribution by means of extreme value method. 3) Power spectral density (PSD) analysis of PTO torque fluctuations. To record the rear wheel shaft torque, a strain gege type transducer was fabricated at the International Rice Research Institute, the Philippines. The following conclusions can be drawn:
1) In upland, major tractor power consumption was directed to required PTO hp showing in contrast the slight variation of required rear axle hp lay thrust action (Tab. 3). It can be noted that the required rear axle hp might not exceed 5.0% of the corresponding required PTO hp. In lowland difference of these two values on required hp became smaller gradually if not rapidly with the increase of travel speed (Tab. 4). It might be of interest to note that under heavy wetland conditions like treatment g in Tab. 4, the rear axle torque showed more than three times than that required in upland conditions.
2) Every curve shown in Fig. 10 can be considered as nearly normal distributions. Values as the foot of the extreme sides in reference to mode range±1.7 times in the 1st and in the 2nd gears while±1.4 times in the 3rd and in the 4th gears. Absolute values of mode in lowland go so much down as compared with upland. Comparing results with upland in the 1st gear, it shifts down to half for crest and trough and in the 2nd gear almost identical to crest of upland but half to trough, and then decrese from 1/9 to 1/11 in the 3rd and in the 4th gear (Fig. 11). It is a salient feature to observe the action of negative torque due to big inertia force of the rotary tiller itself and small loads under this field condition.
3) It is clearly evident in Fig. 12 (a) that dominant frequency, that is 109. 1cps, seems to be inherent one composed of intricate accumulative noise for which specification, arrangement and natural frequency of rotary tines might have major effects. What is more, a couple of distinguishable frequencies can be seen in Fig. 12 (b), in which slack and frequent periodicity can be recognized. The former shows 12.0cps which approximates speed of rotary tine shaft, thus another periodicity shows same frequency as Fig. 12 (a). In Fig. 12 (c), earlier periodic wave collapses into less amplitude gradually with lapse of time tending to show a certain frequency, 119.1cps. Although the wave form in Fig. 12 (d) looks random, it can be recognized that sinusoidal phenomena might be exposed on the outside clearly indicating 61.7cps.
Pronounced values in the PSD correspond completely with the frequencies which were evaluated in the correlogram at time domain and hence it is easy to observe the extent of intensity of each frequency quantitatively. Travel speed seems to affect the transfer of frequency. But these values coincide approximately with the caluculated value in terms of line spectrum (Fig. 9) and so validity of the theory of rotary tine arrangement is partly verified.