Holding a hybrid electric vehicle on an inclined surface

A method for controlling a vehicle powertrain to hold the vehicle stationary on a grade, comprising the steps of:

• (a) if a state of charge of a battery is lower than a reference, and temperature of a first and a second electric machine is higher than a respective reference temperature, using an engine to produce torque required to hold the vehicle;
• (b) if the state of charge is higher than the reference, and neither machine alone can produce said torque, using the engine in combination with the machines if the temperature of the first and second machines is lower than the reference temperature to produce said torque;
• (c) if the state of charge is higher than the reference, one of the machines can produce said torque, and temperature of said one of the machines is lower that its reference temperature, using said one of the machines to produce said torque;
• (d) determining that the state of charge is lower than the reference;
• (e) determining that the first machine can produce said torque at the wheels in combination with the second machine;
• (f) determining that the temperature of the first machine is-lower than its reference temperature and the temperature of the second machine is lower than its reference temperature;
• and
• (g) using the first machine and the second machine concurrently to drive the wheels and produce said torque at the wheels.

A method for controlling a vehicle powertrain to hold the vehicle stationary on a grade, comprising the steps of:

• (a) if a state of charge of a battery is lower than a reference, and temperature of a first and a second electric machine is higher than a respective reference temperature, using an engine to produce torque required to hold the vehicle;
• (b) if the state of charge is higher than the reference, and neither machine alone can produce said torque, using the engine in combination with the machines if the temperature of the first and second machines is lower than the reference temperature to produce said torque;
• (c) if the state of charge is higher than the reference, one of the machines can produce said torque, and temperature of said one of the machines is lower that its reference temperature, using said one of the machines to produce said torque;
• and
• (d) using the engine in combination with the first machine if the temperature of the first machine is lower than the respective reference temperature, or the second machine if the temperature of the second machine is lower than the respective reference temperature, or both machines if the temperature of the first machine is lower than the respective reference temperature and the temperature of the second machine is lower than the respective reference temperature, to produce said torque.