Preventing gear shift cycling of a hybrid electric vehicle

1. A method for controlling a vehicle powertrain, comprising:

(a) producing a first wheel torque by transmitting torque from a power source and a motor to a transmission input in response to a demanded wheel torque;

(b) using a second motor connected to an output of the transmission to increase wheel torque greater than an increased demanded wheel torque while the vehicle is cornering and without downshifting.

2. The method of claim 1 further comprising operating the transmission in a desired gear to produce the first wheel torque and the increased wheel torque.

3. The method of claim 1 wherein the increased demanded wheel torque occurs upon exiting a cornering maneuver.

4. The method of claim 1 further comprising the steps of:

preparing a gear shift schedule that establishes a boundary between a range of operating states for each transmission gear as a function of the demanded wheel torque and vehicle speed; and

using the demanded wheel torque, the vehicle speed and the shift schedule to determine a desired gear.

5. The method of claim 1 wherein step (b) further comprises the steps of:

determining a current magnitude of wheel torque able to be produced by the motor; and

using the second motor to increase wheel torque greater than an increased demanded wheel torque, if the current magnitude of wheel torque able to be produced by the second motor is equal to or greater than a difference between the increased demanded wheel torque and the first wheel torque.

6. The method of claim 1 wherein step (b) further comprises the steps of:

determining a current magnitude of wheel torque able to be produced by the motor; and

making no use of the motor, if the current magnitude of wheel torque able to be produced by the motor is less than a difference between the demanded wheel torque and the first wheel torque; and

performing a downshift.

7. A method for controlling a vehicle powertrain, comprising:

(a) operating an engine and a transmission in a current gear to produce a first wheel torque;

(b) if a first wheel torque produceable by the engine and a motor connected to an input of the transmission is less than demanded wheel torque, performing a downshift;

(c) using a second motor connected to an output of the transmission to increase wheel torque greater than an increased demanded wheel torque while the vehicle is cornering without downshifting.

8. The method of claim 7 further comprising the step of:

determining that the second electric motor has a current ability to produce a second wheel torque, whose magnitude is equal to or greater than a difference between the increased demanded wheel torque and the first wheel torque.

9. The method of claim 7 wherein step (c) further comprises the step of:

determining that the increased demanded wheel torque is greater than the first wheel torque able to be produced in the current gear by the engine and first electric motor.

10. The method of claim 7 wherein step (b) further comprises the step of increasing the demanded wheel torque upon exiting a curved path.

11. The method of claim 7 further comprising the steps of:

preparing a gear shift schedule that establishes a boundary between a range of operating states for each transmission gear as a function of the demanded wheel torque and vehicle speed; and

using the demanded wheel torque, the vehicle speed and the shift schedule to determine the current gear.

12. The method of claim 7 wherein step (d) further comprises the steps of:

determining a current magnitude of wheel torque able to be produced by the second motor; and

using the second motor to provide the second wheel torque, if the current magnitude of wheel torque able to be produced by the second electric motor is equal to or greater than a difference between the increased demanded wheel torque and the magnitude of wheel torque able to be produced in the current gear.

13. The method of claim 7 wherein step (b) further comprises the steps of:

determining a current magnitude of wheel torque able to be produced by the motor; and

making no use of the motor, if the current magnitude of wheel torque able to be produced by the motor is less than a difference between the demanded wheel torque and the magnitude of the first wheel torque able to be produced in the current gear.

14. A method for controlling a vehicle powertrain, comprising:

(a) operating an engine and transmission to produce wheel torque;

(b) if a first wheel torque producable by the engine and a motor connected to an input of the transmission is less than demanded wheel torque, performing a downshift;

(c) if a first wheel torque producable by the engine and the motor is greater than demanded wheel torque, using a second motor connected to an output of the transmission to increase wheel torque greater than an increased demanded wheel torque while the vehicle is cornering without downshifting.

15. The method of claim 14 wherein step (d) further comprises the steps of:

determining a current magnitude of wheel torque able to be produced by the motor; and

making no use of the motor, if the current magnitude of wheel torque able to be produced by the motor is less than a difference between the demanded wheel torque and the magnitude of the first wheel torque able to be produced in the current gear.

16. The method of claim 14 further comprising the step of:

determining that the second electric motor has a current ability to produce a second wheel torque, whose magnitude is equal to or greater than a difference between the increased demanded wheel torque and the first wheel torque.

17. The method of claim 14 wherein step (d) further comprises the step of:

determining that the increased demanded wheel torque is greater than the first wheel torque able to be produced in the current gear by the engine and first motor.