Three point hitch: draft control controller 1

[pietro82]

Hi all,

I need to simulate an eletronic draft control of a three point hitch. I use simulink to simulate this. Does anyone know how the draft controller works? Any suggestion, paper or reference is appreciated.

Thanks

Best regards

Pietro

 

[Coredordelasolas]

On my tractors there are the draft controller and the position controller. The draft controller acts like a "pressure controller" putting more or less force down on the implement in use. I set my position controller in the middle, "intermix". Then the draft controller I set as I need for pressure down harder or up for less. While operating the tractor and the implement I can feel the need for more or less force in the seat of my pants so to speak. Different soil conditions dictate the amount of force required to do the job.

 

[pietro82]

Hi Coredordelasolas,

thanks for your reply. But do you know the controller transfer function o how the controller works?

Thanks

cheers

Pietro

 

[avantibngrant]

Draft control for say 35 hp and down works by sensing the puch on the top link which is the reaction to the moment the load creates adound the lower link cross shaft. Larger tractors use lowe link sensing which senses the horizontal pull force right on the lower link mounts. Both system balance these forces against the the draft handle position. For a given handle position, if there is an increaes in draft, the system will actuate the valve and lift the implement to try to retain the same draft sensed. Conversely it will lower the implement on a lighter sensed load. Most hydraulics have only one way (lift) capabilities. The downward force is implement weight and suction say from a plow. The upside is an increase in draft will transfer a little weigh to the tractor when it lifts the implement due to an increase in draft say as from the implement going too deep if the tractor wheel drops into a hole. Make sense?
My tractorw with draft control - 540 and 550 Cockshutt use the top link sensing method. It works well with the 3 furrow plow. The draft control can be locked out for position control only.
Regards
Neil

 

[pietro82]

Hi,

thanks for your reply. I know how roughly the draft control works, but I have to model it with simulink, but I don't have no idea how to do it. Any suggestion is very appreciated

thanks

 

[pietro82]

does anyone have any idea on the kind of valve used to control the three point hitch? Is it a flow control valve?