System and method for detecting combine rotor slugging

1. A method to sense incipient slugging in a combine having a rotor for threshing crop material, an internal combustion engine configured to be coupled to the rotor to drive the rotor; and a hydraulic motor configured to be coupled to the rotor to drive the rotor, the method comprising the steps of:

sensing a first motor speed with a motor speed sensor;

sensing an engine speed with an engine speed sensor;

sensing a rotor speed with a rotor speed sensor;

a controller combining the engine speed and the rotor speed to provide a second motor speed;

the controller determining incipient slugging based upon the first motor speed and the second motor speed;

wherein if slugging is determined, disengaging the rotor from both the engine and the motor;

wherein if slugging is not determined, determining rates of change of a signal from the motor speed sensor, a signal from the engine speed sensor and a signal from the rotor speed sensor; and

determining incipient slugging based upon the three rates of change.

2. The method of claim 1 , wherein the motor is driven by a hydraulic pump, the method further comprising the steps of, the controller:

determining a first flow rate of hydraulic fluid through the pump;

determining a second flow rate of hydraulic fluid through the motor;

determining a difference between the first and second flow rates, and

determining incipient slugging based upon the difference.

3. The method of claim 1 , wherein the step of determining incipient slugging further comprises the steps of, the controller:

selecting a first threshold motor speed based at least upon a first selected gear ratio; and

comparing the first and second motor speeds with the first threshold motor speed.

4. The method of claim 3 , further comprising the step of:

the controller comparing the first and second motor speeds against a second threshold motor speed different from the first threshold motor speed when a second gear ratio different from the first gear ratio is selected.

5. The method of claim 1 , further comprising the step of:

disengaging the rotor from both the engine and the motor based at least upon the steps of determining.

6. A system to sense incipient slugging in a combine having a rotor for threshing crop material, an internal combustion engine configured to be coupled to the rotor to drive the rotor; and a hydraulic motor configured to be coupled to the rotor to drive the rotor, the system comprising:

at least one electronic controller;

a motor speed sensor coupled to the at least one electronic controller and to the motor to sense a first motor speed;

an engine speed sensor coupled to the at least one electronic controller and to the engine to sense the engine speed; and

a rotor speed sensor coupled to the at least one electronic controller and to the rotor to sense the rotor speed;

wherein the electronic controller is configured to

receive an engine speed signal from the engine speed sensor,

receive a rotor speed signal from the rotor speed sensor,

combine the engine speed signal and the rotor speed signal to provide a second motor speed, and

determine incipient slugging based upon the first motor speed and the second motor speed,

wherein the motor is driven by a hydraulic pump and, when incipient slugging is not determined, the controller is further configured to:

determine a first flow rate of hydraulic fluid through the pump;

determine a second flow rate of hydraulic fluid through the motor;

determine a difference between the first and second flow rates; and

determine incipient slugging based upon the difference.

7. The system of claim 6 , wherein the controller is further configured to;

determine rates of change of the motor speed signal, the engine speed signal and the rotor speed signal; and

determine incipient slugging based upon the three rates of change.

8. The system of claim 6 , wherein the controller is further configured to:

select a first threshold motor speed based at least upon a first selected gear ratio; and

compare the first and second motor speeds with the first threshold motor speed.

9. The system of claim 8 , wherein the controller is further configured to:

compare the first and second motor speeds against a second threshold motor speed different from the first threshold motor speed when a second gear ratio different from the first gear ratio is selected.

10. The system of claim 6 , wherein the controller is further configured to:

disengage the rotor from both the engine and the motor based at least upon the step of determining.

11. A system to sense incipient slugging in a combine having a rotor for threshing crop material, an internal combustion engine configured to be coupled to the rotor to drive the rotor; and a hydraulic motor configured to be coupled to the rotor to drive the rotor, the system comprising:

means for sensing a first motor speed;

means for sensing engine speed;

means for sensing rotor speed; and

electronic control means, the control means further comprising:

means for receiving an engine speed signal from the means for sensing engine speed;

means for receiving a rotor speed signal from the means for sensing rotor speed;

means for combining the engine speed signal and the rotor speed signal to provide a second motor speed; and

means for determining incipient slugging based upon the first motor speed and the second motor speed;

means for disengaging the rotor from both the engine and the motor when incipient slugging is determined.

12. The system of claim 11 , wherein the means for controlling further comprises:

means for determining rates of change of the motor speed signal, the engine speed signal and the rotor speed signal; and

means for determining incipient slugging based upon the three rates of change.

13. The system of claim 11 , wherein the motor is driven by a hydraulic pump and the means for controlling further comprises:

means for determining a first flow rate of hydraulic fluid through the pump;

means for determining a second flow rate of hydraulic fluid through the motor;

means for determining a difference between the first and second flow rates; and

means for determining incipient slugging based upon the difference.

14. The system of claim 11 , wherein the means for controlling further comprises:

means for selecting a first threshold motor speed based at least upon a first selected gear ratio; and

means for comparing the first and second motor speed with the first threshold motor speed.

15. The system of claim 14 , wherein the means for controlling further comprises:

means for comparing the first and second motor speed against a second threshold motor speed different from the first threshold motor speed when a second gear ratio different from the first gear ratio is selected.