Tractors incorporate draught, controls for two reasons, to limit
variations in implement depth and to limit fluctuations in the load,
i.e. the draught force, imposed on the tractor by the implement.
Efficient operation of this control is important because many farmers
demand a consistent tillage depth and also, if the load is controlled,
the tractor can be operated at its maximum output without excessive
wheel slip or engine stall.
The work for this thesis involved a theoretical investigation of draught control response and its effect on overall tractor performance.
A computer model was devised to simulate draught control and its
effect on dynamic performance of the tractor-implement combination.
Input data for the simulation was provided by laboratory measurements.
Two series of field work were carried out to measure response of a
linkage force sensing experimental control to sinusoidal and random
draught variations and the response of a control which sensed driveline
torque. Comparisons between measured and predicted results, confirmed
the validity of the theoretical analysis.
Suggestions for improving control performance, particularly
stability, are made and the likely improvement predicted using the
computer simulation. Other possible methods of implement control or
improvements to draught controls are discussed in relation to the
likely requirements of future tractors.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy at Loughborough University.