What is the difference between position control and draft control?
In position control the lever position corresponds directly to the linkage height and the implement stays at a fixed height even if the soil changes; it is suitable for cultivators, seed drills, sprayers and fertiliser spreaders. In draft control the drawbar force is selected with the lever, and when the soil becomes firmer the system automatically raises the implement, reducing slip and engine bogging.
The two methods hold different quantities constant.
- Position control fixes the geometry. Every angle of the lever corresponds to a particular linkage height. It is preferred on implements with little soil contact or low draft resistance: cultivators, seed drills, sprayers, fertiliser spreaders.
- Draft control fixes the force. When the drawbar force read from the top link or the lower links increases, the linkage rises somewhat, and when the force falls it descends. On high-draft implements such as ploughs it reduces engine bogging and wheel slip.
Because pure draft control can behave over-sensitively, in practice mixed control is common: while the draft force is managed, the position lever acts as a lower limit, so the implement does not go below the set depth.
AXI retrofit kits are fitted to the hydraulic control side of the tractor; they do not change which type of control the existing mechanism offers, they move the lever of that mechanism electrically. In other words, if your tractor has draft control you continue to work with draft control, and if it does not you continue with position logic.
The full topic: Converting a tractor hydraulic lever to electronic control