A Study of Significance in Lower Link Draft Sensing and Comparative Study over Top Link

One of the major impacts on tractor performance during cultivation is variation in soil draft. The control strategy shall be developed to maintain the soil draft which mainly depends on the sensitivity and accuracy of draft measurement. This paper presents the theoretical calculation of force on the lower link points of three point hitch system in tractor and selecting an optimum point for the fitment of draft sensor. The force distribution on the lower and top link was studied by developing the suitable mechanical frame with hydraulic actuation to simulate the soil draft. The control strategy was developed to maintain the draft force with tractor hydraulic system and field testing was performed on 58 hp (43 kW) tractor to compare the draft control operation with lower link draft sensing methodology and conventional top link based draft sensing. The Land was cultivated by driving the tractor on all combination of soil type transition (Hard, Medium and Soft soil) and effectiveness of draft control was analyzed. This simulation test results confirmed that the ratio of lower link point force versus simulated draft force was 0.9 to 1.04 which was significantly higher than top link sensed force ratio of 0.3 to 0.406. The field test results shown the performance of draft control was improved and the time lag between lower links sensing and top link sensing was varying between 50 ms to 150 ms depending on the soil condition and the depth variation in lower link sensing was 3.5 cm compared to 5 cm in top link sensing.