Output torque error mitigation for strong hybrid PRNDL neutral operation

Method for controlling a powertrain system of a vehicle comprising an internal combustion engine, first and second electric machines, an electro-mechanical transmission comprising at least one planetary gear set configured to transmit torque to a driveline, the method comprising:

• in response to an operator input selecting neutral operation of the transmission, operating the transmission in neutral without mechanically decoupling the transmission from the driveline comprising:
• commanding a net zero output torque from the transmission to the driveline based on balancing torque commands among each of the engine and the first and second electric machines,
• monitoring engine torque, a first motor torque from the first electric machine and a second motor torque from the second electric machine,
• monitoring a first clutch grounding an element of the first planetary gear set;
• determining a presence of a torque error based on the monitored first clutch, the monitored engine torque, the first motor torque and the second motor torque, and
• allowing slippage within the first clutch to prevent net output torque reacting with the driveline from exceeding a motionless driveline threshold.

Apparatus for controlling neutral operation in a powertrain system of a vehicle, the apparatus comprising:

• an internal combustion engine;
• first and second electric machines;
• an electro-mechanical transmission mechanically-operatively coupled to the internal combustion engine and the first and second electric machines adapted to selectively transmit mechanical power to an output member that reacts with a driveline;
• a control module:
• enabling neutral operation of the transmission in response to an operator input,
• activating a first clutch coupled to a first element of a first planetary gear set,
• coordinating torque commands between the engine and the first electric machine to establish a net zero output torque condition, and
• if a violation of the net zero output torque condition is present, allowing slippage of the first clutch to dissipate net output torque from reacting with the driveline of the powertrain system.