Variable fan drive dependent on cleaning fan drive load

1. A combine comprising:

a feeder housing for receiving harvested crop;

a separating system for threshing the harvested crop to separate grain from residue;

a crop cleaning system including a cleaning fan powered by a fan drive to drive the cleaning fan at a speed and propel the residue into a residue system of the combine;

at least one sensor for detecting an operational parameter of the fan drive; and

a controller coupled to the at least one sensor, the controller configured to:

determine a load on the fan drive from the detected operational parameter, wherein the operational parameter is an amount of hydraulic pressure, electric power, or mechanical torque required in order to drive the cleaning fan at the speed,

compare the determined load to a load threshold, and

control the speed of the cleaning fan based on the comparison by:

reducing the speed of the cleaning fan in response to an increase in the load, and

increasing the speed of the cleaning fan in response to a decrease in the load.

2. The combine of claim 1 ,

wherein the controller is further configured to:

compare the load to the load threshold,

maintain the speed of the cleaning fan when the load is less than the load threshold, and

decrease the speed of the cleaning fan when the load is greater than the load threshold.

3. The combine of claim 1 ,

wherein the controller is further configured to:

compare the load to a second load threshold, and

control the speed of the cleaning fan based on the comparison between the load and the second load threshold.

4. The combine of claim 1 ,

wherein the controller is further configured to:

compare the load to the load threshold, and

increase the speed of the cleaning fan when the load is less than the load threshold.

5. The combine of claim 1 ,

wherein the fan drive includes a hydraulic motor, and the sensor includes a hydraulic pressure sensor, and

wherein the controller is further configured to:

determine the load on the fan drive from hydraulic pressure detected by the sensor, and

control the speed of the cleaning fan based on the detected hydraulic pressure.

6. The combine of claim 5 ,

wherein the fan drive includes a hydraulic pump, and

wherein the controller is further configured to:

control the hydraulic pump to control the speed of the cleaning fan.

7. The combine of claim 1 ,

wherein the fan drive includes a transmission and a motor, and the sensor includes a torque sensor, and

wherein the controller is further configured to:

determine the load on the fan drive from torque detected by the torque sensor, and

control the speed of the cleaning fan by controlling the power applied to the fan motor based on the detected torque or control a gear ratio of the fan drive transmission based on the detected torque.

8. The combine of claim 1 ,

wherein the fan drive includes an electric motor, and the sensor includes an electrical power sensor, and

wherein the controller is further configured to:

determine the load on the fan drive from electrical power detected by the sensor, and

control speed of the cleaning fan by controlling the power applied to the electric motor based on the detected electric power.

9. The combine of claim 8 ,

wherein the fan drive includes an electric motor driver circuit, and

wherein the controller is further configured to:

control the electric motor driver circuit to control the power applied to the electric motor.

10. The combine of claim 1 , further comprising:

a touch screen display,

wherein the controller is further configured to:

display an indicator on the touch screen display that indicates the operational parameter of the cleaning fan,

receive user input through the touch screen display indicating fan speed settings for a given operational parameter, and

control the speed of the fan based on the received input.

11. A method for controlling a combine comprising:

receiving, by a feeder housing, harvested crop;

threshing, by a separating system, the harvested crop to separate grain from residue;

cleaning, by a crop cleaning system including a cleaning fan powered by a fan drive, by driving the cleaning fan at a speed and propelling the residue into a residue system of the combine;

detecting, by at least one sensor, an operational parameter of the fan drive;

determining, by a controller coupled to the at least one sensor, a load on the fan drive from the detected operational parameter, wherein the operational parameter is an amount of hydraulic pressure, electric power, or mechanical torque required in order to drive the cleaning fan at the speed;

comparing, by the controller, the determined load to a load threshold; and

controlling, by the controller, the speed of the cleaning fan based on the comparison by:

reducing the speed of the cleaning fan in response to an increase in the load, and

increasing the speed of the cleaning fan in response to a decrease in the load.

12. The method of claim 11 , further comprising:

comparing, by the controller, the load to the load threshold;

maintaining, by the controller, the speed of the cleaning fan when the load is less than the load threshold; and

decreasing, by the controller, the speed of the cleaning fan when the load is greater than the load threshold.

13. The method of claim 11 , further comprising:

comparing, by the controller, the load to a second load threshold; and

controlling, by the controller, the speed of the cleaning fan based on the comparison between the load and the second load threshold.

14. The method of claim 11 , further comprising:

comparing, by the controller, the load to the load threshold; and

increasing, by the controller, the speed of the cleaning fan when the load is less than the load threshold.

15. The method of claim 11 , further comprising:

determining, by the controller, the load on the fan drive from a hydraulic pressure detected by a hydraulic pressure sensor included in the sensor; and

controlling, by the controller, the speed of the cleaning fan by controlling the power applied to a hydraulic motor included in the fan drive based on the detected hydraulic pressure.

16. The method of claim 15 , further comprising:

controlling, by the controller, a hydraulic pump included in the fan drive to control the power applied to the hydraulic motor.

17. The method of claim 11 , wherein the at least one sensor includes a torque sensor, the method further comprising:

determining, by the controller, the load on the fan drive from a torque detected by the torque sensor; and

controlling, by the controller, the speed of the cleaning fan by controlling the power applied to the motor based on the detected torque, or by controlling a gear ratio of a transmission included in the fan drive based on the detected torque.

18. The method of claim 11 , wherein the at least one sensor includes electric power sensor, the method further comprising:

determining, by the controller, the load on the fan drive from an electrical power detected by the electric power sensor; and

controlling, by the controller, the speed of the cleaning fan by controlling the power applied to an electric motor included in the fan drive based on the detected electric power.

19. The method of claim 18 , further comprising:

controlling, by the controller, an electric motor driver circuit included in the fan drive to control the power applied to the electric motor.

20. The method of claim 11 , further comprising:

displaying, by a touchscreen display, an indicator that indicates the operational parameter of the cleaning fan;

receiving, by the touchscreen display, user input indicating fan speed settings for a given operational parameter; and

controlling, the speed of the cleaning fan by controlling the fan drive power based on the received input.