EFFECT OF DRAUGHT CONTROL RESPONSE ON PERFORMANCE OF AGRICULTURAL TRACTORS

Present methods of assessing the performance of agricultural tractors both theoretically and practically only consider steady-state operation. The dynamic behaviour of a tractor is, however, equally important in determining its usefulness. The most important factor which determines a tractor's dynamic performance is the operation of its draught control system. This has, therefore, been analysed theoretically in this paper so that it can be used in a more comprehensive dynamic analysis of the complete tractor and implement combination. Field experiments are described in which tractors with different draught control systems were used for ploughing. Measurements were made of the forces between the tractors and ploughs and of the movement of the ploughs relative to the ground and the tractors. The movement of the ploughs due to measured forces on the sensing elements of the control systems was determined. The dynamic responses of the control systems in the field were compared with the steady state responses measured in the laboratory. It was found that field performance was impaired by overshoot in the dynamic response. When allowance is made for this, the performance in a given field could be adequately predicted from the response measured in the laboratory and certain measured characteristics of the field. © 1969.