On demand machine rimpull adjustment to prevent tire slip

1. A system for proactively controlling a rimpull limit of a machine, the machine including an implement and a power train including an engine and producing a torque, the system comprising:

a hydraulic system, the hydraulic system including a lift cylinder to move the implement;

a lift cylinder pressure sensor that senses a hydraulic pressure of the lift cylinder and responsively produces a lift cylinder pressure signal; and

a controller in operable communication with the power train and the lift cylinder pressure sensor, the controller being configured to:

receive the lift cylinder pressure signal;

determine the rimpull limit based at least in part upon the lift cylinder pressure signal;

increase the rimpull limit in response to an increase in the hydraulic pressure of the lift cylinder; and

adjust the torque of the power train to the rimpull limit.

2. The system of claim 1 , wherein the power train includes a torque converter having an impeller clutch, the controller being further configured to adjust a pressure of the impeller clutch based on the rimpull limit.

3. The system of claim 1 , wherein the power train includes an electric motor in communication with a continuously variable transmission, the controller being further configured to adjust a current to the electric motor based on the rimpull limit.

4. The system of claim 1 , wherein the power train includes a hydrostatic motor in communication with a continuously variable transmission, the controller being further configured to adjust a displacement of a variator based on the rimpull limit.

5. The system of claim 1 , wherein the power train includes a torque converter, the controller being further configured to adjust a speed of the engine based on the rimpull limit.

6. The system of claim 1 , further comprising:

a lift position sensor that senses a lift position of the implement and responsively produces a lift position signal; and

a tilt position sensor that senses a tilt position of the implement and responsively produces a tilt position signal,

the controller being in operable communication with the lift position sensor and the tilt position sensor, the controller being further configured to determine the rimpull limit based upon the lift cylinder pressure signal, the lift position signal, and the tilt position signal.

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

receive a friction input that is related to a coefficient of friction for a given surface upon which the machine is operate, and

determine the rimpull limit based at least in part upon the friction input.

8. A system for proactively controlling tire slip of a machine, the machine including an implement and a power train including an engine and producing a rimpull, the system comprising:

a wheel having a tire and mounted on the machine in operable communication with the power train;

a hydraulic system including a lift cylinder to move the implement;

a lift cylinder pressure sensor that senses a pressure of the lift cylinder and responsively produces a lift cylinder pressure signal; and

a controller in operable communication with the power train and lift cylinder pressure sensor, the controller being configured to:

receive the lift cylinder pressure signal;

determine a downforce on the wheel based at least in part upon the lift cylinder pressure signal; and

increase the rimpull applied to the wheel in response to an increase in the downforce on the wheel.

9. The system of claim 8 , wherein the power train includes a torque converter having an impeller clutch, the controller being further configured to adjust a pressure of the impeller clutch to modify the rimpull.

10. The system of claim 8 , wherein the power train includes an electric motor in communication with a continuously variable transmission, the controller being further configured to adjust a current to the electric motor to modify the rimpull.

11. The system of claim 8 , wherein the power train includes a hydrostatic motor in communication with a continuously variable transmission, the controller being further configured to adjust a displacement of a variator to modify the rimpull.

12. The system of claim 8 , wherein the power train includes a torque converter, the controller being further configured to adjust a speed of the engine to modify the rimpull.

13. The system of claim 8 , further comprising a lift position sensor, the lift position sensor sensing a lift position of the implement and responsively producing a lift position signal,

the controller being in operable communication with the lift position signal, the controller being further configured to determine the downforce on the wheel based at least in part upon the lift cylinder pressure signal and the lift position signal.

14. The system of claim 13 , further comprising a tilt position sensor, the tilt position sensor sensing a tilt position of the implement and responsively producing a tilt position signal,

the controller being in operable communication with the tilt position signal, the controller being further configured to determine the downforce on the wheel based at least in part upon the lift cylinder pressure signal, the lift position signal, and the tilt position signal.

15. The system of claim 13 , wherein the controller is further configured to

receive a friction input that is related to a coefficient of friction for a given surface upon which the machine is operated, and

adjust the rimpull applied to the wheel based at least in part upon the friction input.

16. A method for on demand rimpull control of a machine, the machine including an implement in operable communication with a hydraulic lift cylinder and a power train including an engine and producing a torque, the method comprising:

sensing a hydraulic pressure of the hydraulic lift cylinder;

receiving within a controller a hydraulic pressure signal that is indicative of the hydraulic pressure of the hydraulic lift cylinder;

determining, via the controller, a rimpull limit based at least in part upon the hydraulic pressure signal;

increasing the rimpull limit in response to an increase in the hydraulic pressure of the hydraulic lift cylinder; and

adjusting the torque to the rimpull limit.

17. The method of claim 16 , further comprising:

sensing a lift position of the implement; and

determining, via the controller, the rimpull limit based at least in part upon the lift position of the implement.

18. The method of claim 16 , further comprising:

sensing a tilt position of the implement; and

determining, via the controller, the rimpull limit based at least in part upon the tilt position of the implement.

19. The method of claim 17 , further comprising:

receiving within the controller a friction input that is related to a coefficient of friction for a surface upon which the machine is operated; and

determining, via the controller, the rimpull limit based at least in part upon the friction input.