Method of determining torque limit with motor torque and battery power constraints

1. Method to determine a limit torque associated with an electro-mechanical transmission operatively coupled to first and second electric machines electrically connected to an electrical energy storage device to transfer mechanical power to an output member, comprising:

monitoring operation of the electro-mechanical transmission;

determining motor torque constraints of the first and second electric machines and battery power constraints for the electrical energy storage device;

determining a limit torque function and identifying an original form of the limit torque function;

transposing the limit torque function to a standard form;

transposing the motor torque constraints and the battery power constraints;

determining a transposed limit torque in the standard form based upon the transposed limit torque function and the transposed motor torque constraints and the transposed battery power constraints; and

retransposing the transposed limit torque from the standard form to the original form to determine the limit torque in the original form.

2. The method of claim 1 , further comprising:

transforming the motor torque constraints of the first and second electric machines and the battery power constraints and the limit torque function antecedent to transposing the limit torque function to the standard form,

retransforming the determined limit torque in the original form, and

controlling the first and second electric machines based upon the retransformed limit torque.

3. The method of claim 1 , further comprising controlling operation of the electro-mechanical transmission and the first and second electric machines based upon the limit torque.

4. The method of claim 3 , wherein the limit torque comprises an output torque to the output member.

5. The method of claim 3 , further comprising the electro-mechanical transmission including a selectively applicable torque transfer clutch and the limit torque comprising a reactive torque of the selectively applied torque transfer clutch.

6. The method of claim 3 , further comprising the electro-mechanical transmission including an input member and the limit torque comprising an input torque to the input member.

7. The method of claim 2 , comprising determining the transformed limit torque by simultaneously solving the transformed limit torque function, transformed motor torque constraints, and transformed battery power constraints to determine one of a maximum and a minimum transformed limit torque.

8. The method of claim 1 , wherein the limit torque comprises a minimum output torque to the output member achievable within the motor torque constraints and battery power constraints.

9. The method of claim 8 , wherein the minimum output torque to the output member comprises a maximum regenerative torque output for electric power generation.

10. The method of claim 1 , wherein the limit torque comprises a maximum output torque to the output member achievable within the motor torque constraints and the battery power constraints.

11. The method of claim 10 , wherein the maximum output torque to the output member comprises a maximum mechanical torque output for tractive power generation.

12. The method of claim 1 , wherein the standard form comprises a combination of a minimum torque output from the first electric machine and a maximum torque output from the second electric machine.

13. The method of claim 1 , further comprising transposing the motor torque constraints and the battery power constraints consistent with the transposing the limit torque function to the standard form.

14. Method to determine a limit torque associated with an electro-mechanical transmission, operatively coupled to first and second electric machines electrically connected to an electrical energy storage device to transfer mechanical power to an output member, comprising:

monitoring operation of the electro-mechanical transmission;

determining motor torque constraints of the first and second electric machines and battery power constraints for the electrical energy storage device;

determining a limit torque function and identifying an original form of the limit torque function;

transforming the motor torque constraints of the first and second electric machines, the battery power constraints, and the limit torque function to a TX/TY space;

transposing the transformed limit torque function to a standard form comprising a combination of a minimum torque output from the first electric machine and a maximum torque output from the second electric machine;

transposing the transformed motor torque constraints and the transformed battery power constraints;

determining a transposed transformed limit torque in the standard form based upon the transposed transformed limit torque function and the transposed transformed motor torque constraints and the transposed transformed battery power constraints;

retransposing the transposed transformed limit torque from the standard form to the original form to determine the transformed limit torque in the original form; and

retransforming the transformed limit torque in the original form.

15. The method of claim 14 , further comprising controlling operation of the electro-mechanical transmission and the first and second electric machines based upon the retransformed limit torque.

16. The method of claim 15 , wherein the limit torque comprises an output torque to the output member.

17. The method of claim 14 , further comprising the electro-mechanical transmission including a selectively applicable torque transfer clutch and the limit torque comprising a reactive torque of the selectively applied torque transfer clutch.

18. The method of claim 14 , further comprising the electro-mechanical transmission including an input member and the limit torque comprising an input torque to the input member.

19. The method of claim 14 , comprising determining the transformed limit torque by simultaneously solving the transformed limit torque function, transformed motor torque constraints, and transformed battery power constraints to determine one of a maximum and a minimum transformed limit torque.