Development of a self-leveling system for the bucket of an agricultural front-end loader using an electro hydraulic proportional valve and a tilt sensor

A front-end loader (FEL) mounted on an agricultural tractor is one of the most commonly used implements for farm work. However, when the tractor carries material using the bucket attached to the FEL on a sloping ground, the materials can spill or roll back over the operator due to the tilted body, thereby requiring the bucket surface to remain level at a constant value regardless of varying slopes. In this study, an active system for controlling the angle of the FEL bucket on a tractor based on the real-time measurement of ground slopes was developed to enable the bucket to constantly remain level. A FEL simulator operated based on an electro hydraulic proportional valve (EHPV) was constructed in the laboratory to develop a proportional-integral-derivative (PID) controller forming a virtual electronic control unit (ECU) on the computer, which could automatically adjust the bucket angles depending on varying input angles while sending SAE-J1939 associated messages via CAN BUS to the EHPV. The different parameter values for the PID controller due to the gravity effect of the bucket were determined using a manual PID tuning method while assuming that the tractor travels on either an ascending slope or a descending slope. The developed PID control-based self-leveling system showed a mean of steady-state errors of within 1° and a mean of delayed times of ~ 0.8s when the step input of +20° was given, implying that the developed system and control algorithm would be effective in maintaining the bucket angle at a certain value. Future studies include the improvement of the control algorithm to reduce such a time delay as well as the application of the developed algorithm to the FEL mounted on a tractor tested at a testing ground. * Corresponding author: kimhj69@snu.ac.kr 1 Department of Biosystems Engineering, Seoul National University, Seoul 08826, Korea 2 KSF Co.,ltd. Ik-San si, Jeon-Bkuk, Korea 3 TAESUNG Co.,ltd. Yang-Ju si, Gyeonggi-do, Korea Copyright C 2015, KSFC This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http:// creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 기호 설명  : response angle signal, V  : output angle signal, V  : set horizontal bucket angle, deg.  : bucket angle variation, deg.  : flow rate of cylinder(head), l/min  : flow rate of cylinder(rod), l/min  : flow coefficient  : open area of valve, cm 2  : area of piston(head), cm 2  : area of piston(rod), cm 2  : supply pressure, kgf/cm 2