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The control of tractor 3 point linkage control systems

This research is part of a comprehensive study of tractor-implement-linkage systems. A complete kinematic model to characterise the motion and geometry of the linkage has been developed; a measurement system to obtain linkage forces, linkage positions and implement depth has been designed, built and tested; and an initial set of field experiments using a 216kW tractor and a five tine cultivator has been carried out.

Year of Publication2011

Over recent years, there has been a resurgence of interest in tractor-implement operating efficiencies – driven by high fossil fuel prices and environmental issues linked to emissions and CO2 usage. The tractor 3 point linkage is actually a key element in this quest for optimum efficiency since it controls two important elements; first, by controlling the dynamic fluctuations of draught force it can enable the tractor to operate closer to its maximum tractive efficiency and second, by controlling the depth of the tillage process it can contribute to good crop growth conditions and ultimately to the maximum yield. The kinematics, dynamics and control of the 3 point linkage attracted a considerable amount of interest in the 1970s – and these analyses were used to influence calculations of optimum tractor-implement operating conditions. However, since that period, the fundamental control aspects of the 3 point linkage have received surprisingly little attention in the off-road vehicle research community. The current systems which are available on commercial tractors remain in principle remarkably similar to the original configuration proposed by Harry Ferguson. However, two significant changes have occurred; first, the systems now make considerable use of electronics – in contrast to the original hydro-mechanical layouts and second, from the operator’s viewpoint in the cabin, the range of control options, settings, levers and knobs can appear overwhelmingly complicated. The research described here is part of a comprehensive study of tractor-implement-linkage systems. A complete kinematic model to characterise the motion and geometry of the linkage has been developed. A measurement system to obtain linkage forces, linkage positions and implement depth has been designed, built and tested. And finally, an initial set of field experiments using a 216kW tractor and a five tine cultivator has been carried out. The experimental results have highlighted some interesting aspects of the trade-off between control of draught force and implement depth – and how these in turn affect the overall tractor-implement operating efficiency.

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Additional keywords/tags

position controlthree point linkagetractive efficiencycontrol systemdraught controllinkage kinematics
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