| 摘要 |
The method for automatically controlling the height of a header used with a farm implement comprises the steps of: sensing the height of the header above ground; selecting a desired height of the header above ground; determining any difference error between the selected height and the sensed height; determining the direction of the difference error, up or down; generating an electrical correction pulse having a duty cycle directly related to the amount of the difference error; supplying the electrical correction pulse to solenoid operated valving means to cause same to supply and/or relieve a pulse of pressurized fluid to a mechanism for raising or lowering the header; and repeating the above steps automatically and continuously to move the header in intermittent pulses toward the selected height, thereby automatically to control the height of the header above ground. The apparatus for carrying out the method comprises: a potentiometer for sensing the height of the header above ground, a potentiometer for selecting a desired height of the header above ground, and a multifunction electrical circuit coupled to the sensing potentiometer and the selecting potentiometer. The circuit is capable of (a) determining the difference error between the selected height and the sensed height, (b) determining the direction of the difference error, up or down, (c) generating an electrical correction pulse having a duty cycle directly related to the amount of difference error, (d) supplying the electrical correction pulse to the solenoid operated valving means to cause same to supply and/or relieve a pulse of pressurized fluid to the mechanism for raising or lowering the header and (e) repeatedly determining the difference error and direction of the difference error, and cyclically generating correction pulses and supplying the correction pulses to the solenoid operated valving means to move the header in intermittent pulses toward the selected height, thereby automatically to control the height of the header above ground.
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