Electro-hydraulic tillage depth control system for rotary implements mounted on agricultural tractor Design and response experiments of control system

A tillage depth control system for rotary implements mounted on an agricultural tractor was designed and constructed to improve accuracy of tillage depth. The control system was composed of five main units: (1) a detecting unit to measure the tilting angle (position) of the lift arm, the pitching angle of the tractor and heights of sensors from ground surface, (2) a controlling unit, (3) a hydraulic unit to operate a three-point hitch linkage by a lift arm cylinder, (4) a three-point hitch linkage and rotary implements, and (5) a setting unit to put the reference tillage depth and a dead zone into the control circuit. The tillage depth was controlled by an on/off operation of a solenoid valve, of which time was proportional to the controlling time. Experiments to evaluate the response characteristics of the control system were conducted under various engine speeds, i.e. various flow rates of hydraulic oil, various tillage depths and some input frequencies. The results of the response experiments of the control system are discussed in this paper. (C) 1998 ISTVS. All rights reserved.