Method and apparatus for controlling an electrified powertrain system of a vehicle

A method for controlling a multi-mode powertrain system including an electric machine mechanically rotatably couplable to a gear train coupled to a driveline via a controllable activatable motor disconnect clutch in response to a command to deactivate the motor disconnect clutch, the method comprising:

• deactivating the motor disconnect clutch,
• controlling an inverter circuit to decrease a motor speed of the electric machine to a first inactive speed threshold,
• controlling the inverter circuit to an inactive state and monitoring the motor speed,
• deactivating the inverter circuit,
• monitoring the motor speed, and
• pulse-activating the inverter circuit to operate the electric machine to increase motor speed to the first inactive speed threshold and then deactivating the inverter circuit when the motor speed has decreased to a second minimum inactive speed threshold.

A powertrain system for propelling a vehicle, comprising:

• an electric machine mechanically rotatably couplable to a driveline via a controllable motor disconnect clutch;
• an inverter circuit electrically connecting a high-voltage DC power bus to the electric machine;
• an inverter controller controlling the inverter circuit;
• a controller, executing a control routine for controlling the powertrain system, including deactivating the motor disconnect clutch in response to a command to deactivate the motor disconnect clutch, wherein the control routine includes the following steps:
• controlling the inverter circuit to decrease motor speed of the electric machine to a first inactive speed threshold,
• controlling the inverter circuit to an inactive state and monitoring the motor speed,
• deactivating the inverter circuit,
• monitoring the motor speed, and
• when the motor speed decreases to a second minimum inactive speed threshold, pulse-activating the inverter circuit to operate the electric machine to increase the motor speed to the first inactive speed threshold, and then deactivating the inverter circuit.