Vehicle direction estimation using transmission control information

1. A work vehicle, comprising:

a chassis;

an engine mounted on the chassis;

a transmission driven by the engine, the transmission including at least one clutch configured to engage the transmission in a forward gear ratio and at least another clutch configured to engage the transmission in a reverse gear ratio;

a plurality of wheels supporting the chassis for movement over the ground,

at least one of said wheels being coupled to the transmission to be driven thereby;

at least one steering actuator coupled to the chassis to steer the chassis with respect to the ground;

a navigation controller coupled to the at least one steering actuator to control the steering actuator; and

a transmission controller coupled to the transmission and to the navigation controller to sense a transmission parameter and communicate a vehicle direction to the navigation controller based upon the transmission parameter

2. The work vehicle of claim 1 , wherein the transmission parameter is a hydraulic fluid pressure of at least one clutch in the transmission parameter.

3. The work vehicle of claim 1 , wherein the transmission comprises an output shaft, and further wherein the transmission parameter is a speed of the output shaft.

4. The work vehicle of claim 1 wherein the navigation controller is configured to calculate a steering command based on the vehicle direction received from the transmission controller.

5. The work vehicle of claim 1 , further comprising GPS postion receiver coupled to the navigation controller and configured to provide the navigation controller with a position of the work vehicle.

6. The work vehicle of claim 1 wherein the transmission controller is configured to periodically determine whether a forward gear ratio is selected, and to transmit data indicative of vehicle movement in a forward direction based at least upon the forward gear ratio being selected.

7. The work vehicle of claim 1 , wherein the navigation controller and the transmission controller are both microprocessor-based ECUs, wherein the navigation controller and the transmission controller coupled together over a serial communication bus, and further wherein the transmission controller is configured to transmit the vehicle direction to the navigation controller over of the serial communication bus.

8. A method of determining a direction of travel of a work vehicle comprising a transmission, said transmission comprising a plurality of clutches and communicating that direction to a vehicle navigation system, the method comprising the steps of:

determining at least one operating state of the transmission;

determining a first direction of vehicle travel based upon the at least one operating state; and

communicating the first direction of vehicle travel to the vehicle navigation system

9. The method of claim 8 , wherein the step of determining at least one operating state includes the step of determining a pressure of a transmission clutch and comparing that pressure to a predetermined clutch pressure.

10. The method of claim 9 , wherein the step of dtermining at least one operating state includes the step of determining the pressures of a set of clutches sufficient to engage the vehicle in a forward gear ratio and comparing the pressures to a predetermined clutch pressure.

11. The method of claim 9 , wherein the step of determining at least one operating state includes the step of determining the pressures of a set of clutches sufficient to engage the vehicle in a reverse gear ratio and comparing the pressures to a predetermined clutch pressure.

12. The method of claim 8 , further including the steps of:

determining a second direction of vehicle travel based upon at least a second operating state; and

communicating the second direction of vehicle travel to the vehicle navigation system.

13. The method of claim 12 , wherein the at least one operating state is the full engagement of clutches sufficient to drive the vehicle in a forward direct.

14. The method of claim 13 , wherein the at least a second operating state is the engagement of clutches sufficient to drive the vehicle in a reverse direction.

15. A control system for a work vehicle including a transmission, the transmission including a plurality of clutches for driving the vehicle over the ground. the vehicle also including a navigation system and steering actuators coupled to the navigation system, the steering actuators being configured to steer the vehicle, the control system comprising:

means for determining a direction of travel of the vehicle by sensing current operating state of the transmission; and

means for communicating the direction of travel to the navigation system.

16. The control system of claim 15 , wherein the means for determining a direction of travel includes means for determining an engagement state of the plurality of clutches.

17. The control system of claim 15 , wherein the means for determining a direction of travel includes means for determining a pressure state of the plurality of clutches.

18. The control system of claim 15 , wherein the means for communicating includes a means for serially communicating coupling the means for determining a direction of travel to the navigation system.

19. The control system of claim 15 , wherein the means for determining a direction of travel includes means for determining whether a plurality of clutches sufficient to engage the vehicle in a forward gear ratio are engaged.

20. The control system of claim 19 , wherein the means for determining a direction of travel includes means for determining whether a second plurality of clutches sufficient to engage the vehicle in a reverse gear ratio are engaged.