Agricultural harvester with closed loop header control

A control system for an agricultural harvester having a frame and a cut crop receiving header, the header having a position which is adjusted by applying fluid under pressure to a hydraulic cylinder, comprising:

• first proportional control valve means fluidly coupled to the cylinder responsive to a first input signal for applying fluid to the cylinder when the header is below a setpoint position, until the header reaches the setpoint position;
• second proportional control valve means fluidly coupled to the cylinder responsive to a second input signal for receiving fluid from the cylinder when the header is above the setpoint position, until the header reaches the setpoint position;
• means for producing an electrical position signal that represents the position of the header;
• means for determining the first and second input signals as a function of the difference between the value of the position signal and the value of the setpoint position, for maintaining the position of the header substantially at the setpoint value, thereby maintaining the position of the header substantially constant, the determining means comprising:
• (a) means for generating respective first, second and third signal components that are proportional to the difference between the position signal and the setpoint value, the integral of the difference with respect to time and the derivative of the difference with respect to time, and
• (b) means for combining the first, second and third signal components to form the first and second input signals.

A control system for an agricultural harvester having a frame, a feeder house pivotally mounted on the frame and a cut crop receiving header, the header having a position which is adjusted by applying fluid under pressure to a hydraulic cylinder, comprising:

• first proportional control valve means fluidly coupled to the cylinder responsive to a first input signal for applying fluid to the cylinder when the header is below a setpoint position, until the header reaches the setpoint position;
• second proportional control valve means fluidly coupled to the cylinder responsive to a second input signal for receiving fluid from the cylinder when the header is above the setpoint position, until the header reaches the setpoint position;
• means for producing an electrical position signal that represents the position of the header;
• means for determining the first and second input signals as a function of the difference between the value of the position signal and the value of the setpoint position, for maintaining the position of the header substantially at the setpoint value, thereby maintaining the position of the header substantially constant;
• a plurality of ground sensors attached to the header, for measuring the position of the header, the ground sensors having a maximum working height;
• and
• means for measuring an angle between the feeder house and the frame and for computing the position of the header from the angle when the header is above the maximum working height.

A control system for an agricultural harvester having a frame and a feeder house pivotally mounted oil the frame and a cut crop receiving header coupled to the feeder house, the header having a plurality of ground sensors, comprising:

• means for measuring an angle between the feeder house and the frame and for computing the position of the header from the angle;
• means for monitoring a plurality of feedback signals from the ground sensors while lowering the header from a raised position to the ground;
• means for identifying the highest position at which the respective feedback signal from each respective ground sensor changes in response to further lowering of the header as the maximum working height of that ground sensor;
• means for identifying the highest position below the maximum working height at which the respective feedback signal from each respective ground sensor does not change in response to further lowering of the header as the minimum working height of that ground sensor;
• means for correlating the respective values of the feedback signal from each sensor at its respective maximum and minimum working heights with respective measurements of the positions determined by the angle measuring means at the maximum and minimum working heights, thereby calibrating each of the ground sensors.