Hydraulic cylinder cushioning

1. A system for damping the extension and retraction of a hydraulic cylinder of the work vehicle at the ends of the cylinder's stroke, the system comprising:

a manually operable operator input device configured to generate a command signal indicative of desired direction of cylinder movement and speed of cylinder movement for movement over the cylinder's entire range of motion;

a hydraulic cylinder having a retraction limit position and an extension limit position;

a sensor configured to generate a signal indicative of hydraulic cylinder position;

a valve coupled to the cylinder to control flow rate of hydraulic fluid to and from the cylinder; and

an electronic controller that is coupled to the operator input device to receive the input device signal, wherein the controller is coupled to the sensor to receive the sensor signal and is coupled to the valve to command valve opening and closing;

wherein the controller is configured to (1) damp retraction of the cylinder near its retraction limit position, (2) damp extension of the cylinder near its extension limit position, and (3) automatically stop damping retraction and extension upon receipt of a damping cancellation signal from the input device.

2. The system of claim 1 , wherein the operator input device includes a member having a central neutral position that can be deflected into directions away from the neutral position.

3. The system of claim 1 , wherein the damping cancellation signal from the input device is a function of at least two specific and successive movements of the input device occurring within a predetermined period of time.

4. The system of claim 3 , wherein the controller maintains an internal timer indicating the time between the occurrence of the at least two specific and successive movements.

5. The system of claim 4 , wherein a first movement of the two movements is a first reversal of an operator command and a second movement of the two movements is a second reversal of an operator command.

6. The system of claim 1 , wherein the cylinder has a central range of positions between the extension limit position and the retraction limit position in which the damping cancellation signal provided by the input device does not cancel damping.

7. A system for damping the extension and retraction of a hydraulic cylinder of the work vehicle at the ends of the cylinder's stroke, the system comprising:

means for generating a command signal indicative of desired cylinder movement direction and cylinder movement rate over the cylinder's entire range of motion;

a hydraulic cylinder having a retraction limit position and an extension limit position;

means for sensing a position of the hydraulic cylinder;

means for controlling fluid flow to and from the hydraulic cylinder; and

means (1) for receiving the command signal, (2) for receiving the sensor signal, and (3) for commanding the means for controlling;

wherein the means for commanding is configured to (1) damp retraction of the cylinder near its retraction limit position, (2) damp extension of the cylinder near its extension limit position, and (3) automatically stop damping retraction and extension upon receipt of a damping cancellation signal from the input device.

8. The system of claim 7 , wherein the means for generating includes a member having a central neutral position that can be deflected into directions away from the neutral position.

9. The system of claim 7 , wherein the damping cancellation signal from the input device is a function of at least two specific and successive movements of the input device occurring within a predetermined period of time.

10. The system of claim 9 , wherein the means for commanding maintains an internal timer indicating the time between the occurrence of the at least two specific and successive movements.

11. The system of claim 10 , wherein a first movement of the two movements is a first reversal of an operator command and a second movement of the two movements is a second reversal of an operator command.

12. The system of claim 9 , wherein the cylinder has a central range of positions between the extension limit position and the retraction limit position in which the damping cancellation signal provided by the means for generating does not cancel damping.

13. An electronic controller configured to damp the extension of a hydraulic cylinder in a work vehicle, the work vehicle including a hydraulic cylinder having a retraction limit position and an extension limit position, a means for sensing a position of the hydraulic cylinder, a valve coupled to the electronic controller for controlling fluid flow to and from the hydraulic cylinder, an operator input device coupled to the electronic controller for generating a command signal indicative of desired cylinder movement over the cylinder's entire range of motion, the electronic controller comprising:

at least one digital microprocessor; and

at least one ROM memory coupled to the at least one digital microprocessor;

wherein the at least one ROM memory includes instructions that direct the digital microprocessor to (1) damp retraction of the cylinder near its retraction limit position, (2) damp extension of the cylinder near its extension limit position, and (3) automatically stop damping retraction and extension upon receipt of a damping cancellation signal from the input device.

14. The controller of claim 13 , wherein the ROM memory includes instructions directing the microprocessor to interpret at least two specific and successive movements of the input device occurring within a predetermined period of time as the damping cancellation signal.

15. The controller of claim 14 , wherein the ROM memory includes instructions commanding the digital microprocessor to maintain an internal timer indicating the time between the occurrence of the at least two specific and successive movements.

16. The controller of claim 14 , wherein the ROM memory includes instructions configured to interpret a first reversal of an operator command as a first movement of the two movements and a second reversal of an operator command as a second movement of the two movements.

17. The controller of claim 13 , wherein the at least one ROM memory includes instructions that direct the digital microprocessor to (4) automatically resume damping retraction and extension upon receipt of a damping resumption signal.

18. The controller of claim 17 , wherein the at least one ROM memory includes instructions directing the microprocessor to interpret the passage of the second predetermined interval of time between two successive damping cancellation signals as the damping resumption signal.

19. The controller of claim 13 , wherein the at least one ROM memory includes instructions that direct the digital microprocessor to linearly damp motion of the cylinder near its extension limit position and its retraction limit position.