Method and system for controlling the height of agricultural implement relative to the ground

1. A method for automatically controlling a height of an implement of an agricultural work vehicle relative to a ground surface, the method comprising:

monitoring, with at least one computing device, the height of the implement relative to the ground surface;

determining, with the at least one computing device, an implement height error by comparing the height of the implement with a predetermined target height;

calculating, with the at least one computing device, a proportional signal gain based on the implement height error, the proportional signal gain varying with the implement height error, wherein calculating the proportional signal gain comprises at least one of:

applying, with the at least one computing device, a discontinuous function such that the proportional signal gain is equal to a predetermined constant when the implement height error is less than a predetermined threshold error; or

applying, with the at least one computing device, a saturation function such that the proportional signal gain does not exceed a predetermined maximum gain;

calculating, with the at least one computing device, a proportional signal based on the implement height error raised to a power greater than one, wherein the proportional signal is based on a product of the implement height error and the proportional signal gain to raise the implement height error to the power greater than one; and

adjusting, with the at least one computing device, the height of the implement relative to the ground surface based on the proportional signal.

2. The method of claim 1 , wherein calculating the proportional signal gain includes normalizing the proportional signal gain based on the predetermined target height.

3. The method of claim 1 , wherein calculating the proportional signal gain comprises applying the saturation function such that the proportional signal gain does not exceed the predetermined maximum gain.

4. The method of claim 1 , wherein calculating the proportional signal gain comprises applying the discontinuous function such that the proportional signal gain is equal to the predetermined constant when the implement height error is less than the predetermined threshold error.

5. The method of claim 1 , wherein calculating the proportional signal includes applying an additional discontinuous function such that the proportional signal is equal to a predetermined proportional signal constant when the implement height error is less than a predetermined proportional signal threshold error.

6. The method of claim 1 , further comprising calculating an integral output signal based on an integral of the implement height error with respect to time, and wherein adjusting the height of the implement includes adjusting the height of the implement further based on the integral output signal.

7. The method of claim 1 , further comprising calculating a derivative output signal based on a derivative of the implement height error with respect to time, and wherein adjusting the height of the implement includes adjusting the height of the implement further based on the derivative output signal.

8. The method of claim 1 , wherein calculating the proportional signal includes squaring the implement height error.

9. The method of claim 1 , wherein adjusting the height of the implement includes controlling a valve fluidly coupled with an actuator configured to raise and lower the implement.

10. A height control system for an implement of an agricultural work vehicle, the control system comprising:

an implement connected with the agricultural work vehicle;

an implement height sensor configured to detect a height of the implement relative to a ground surface;

a controller communicatively coupled to the implement height sensor, the controller including a processor and associated memory, the memory storing instructions that, when executed by the processor, configure the implement controller to:

monitor the height of the implement relative to the ground surface based on signals received from the implement height sensor;

determine an implement height error by comparing the height of the implement with a predetermined target height;

calculate a proportional signal gain based on the implement height error, the proportional signal gain varying with the implement height error, wherein calculating the proportional signal Gain comprises at least one of:

applying a discontinuous function such that the proportional signal gain is equal to a predetermined constant when the implement height error is less than a predetermined threshold error; or

applying a saturation function such that the proportional signal gain does not exceed a predetermined maximum gain;

calculate a proportional signal based on the implement height or raised to a power greater than one, wherein the proportional signal is based on a product of the implement height error and the proportional signal gain to raise the implement height error to the power greater than one; and

adjust the height of the implement based on the proportional signal.

11. The height control system of claim 10 , further comprising an actuator configured to raise and lower the implement relative to the ground surface and a control valve fluidly coupled with the actuator, and wherein the controller is configured to control the flow of a fluid to the actuator using the control valve to adjust the height of the implement relative to the ground surface.

12. The height control system of claim 10 , wherein the controller is configured to normalize the proportional signal gain based on the predetermined threshold error.

13. The height control system of claim 10 , wherein the controller is configured to apply the saturation function such that the proportional signal gain does not exceed the predetermined maximum gain.

14. The height control system of claim 10 , wherein the controller is configured to calculate an integral output signal based on an integral of the implement height error with respect to time, and wherein adjusting the height of the implement includes adjusting the height of the implement further based on the integral output signal.

15. The height control system of claim 10 , wherein the controller is configured to calculate the proportional signal by squaring the implement height error.

16. The height control system of claim 10 , wherein the agricultural work vehicle is a harvester, and the implement is a header.

17. A method for automatically controlling a height of a header of an agricultural harvester relative to a ground surface, the method comprising:

monitoring, with at least one computing device, the height of the header relative to the ground surface;

determining, with the at least one computing device, a header height error by comparing the height of the header with a predetermined target height;

calculating, with the at least one computing device, a proportional signal gain based on the implement height error, the proportional signal gain varying with the implement height error, wherein calculating the proportional signal gain comprises at least one of:

applying, with the at least one computing device, a discontinuous function such that the proportional signal gain is equal to a predetermined constant when the implement height error is less than a predetermined threshold error; or

applying, with the at least one computing device, a saturation function such that the proportional signal gain does not exceed a predetermined maximum gain;

calculating, with the at least one computing device, a proportional signal based on the header height error raised to a power between 1.5 and 2.5, wherein the proportional signal is based on a product of the implement height error and the proportional signal gain to raise the implement height error to the power greater than one; and

adjusting, with the at least one computing device, the height of the header relative to the ground surface based on the proportional signal.