Multi-mode hybrid transmission and method for performing a quasi-asynchronous shift in a hybrid transmission

A method for executing a shift from an initial operating mode to a target operating mode in a multi-mode, electrically variable, hybrid transmission having at least an off-going clutch and an on-coming clutch clutches and operable to receive torque from an engine and at least one motor/generator assembly, the initial operating mode characterized by the off-going clutch in an applied state simultaneous with the on-coming clutch in a released state, and the target operating mode characterized by the off-going clutch in a released state simultaneous with the on-coming clutch in an applied state, the method comprising:

• filling the on-coming clutch to a predetermined pre-fill level;
• determining if the shift is completed using the on-coming clutch or the off-going clutch;
• slipping the off-going clutch prior to slipping the on-coming clutch if the shift operation is completed using the off-going clutch;
• determining if an over/under speed ratio is needed if the shift operation is completed using the on-coming clutch;
• determining on-coming clutch slip speed and acceleration profiles based upon said over/under speed ratio if the shift operation is completed using the off-going clutch or the shift operation is completed using the on-coming clutch and said over/under speed ratio is needed, said on-coming clutch slip speed and acceleration profiles being determined without said over/under speed ratio if the shift operation is completed using the on-coming clutch and said over/under speed ratio is not needed;
• determining if an on-coming clutch slip sign is correct;
• determining if the on-coming clutch is filled;
• calculating and applying an off-going clutch torque based at least in part upon an output torque command;
• locking the on-coming clutch and exhausting the off-going clutch if the shift operation is completed using the off-going clutch, said on-coming clutch slip sign is correct, and the on-coming clutch is filled;
• determining if an on-coming clutch slip is less than a predetermined slip threshold and exhausting the off-going clutch if the shift operation is completed using the on-coming clutch, said on-coming clutch slip sign is correct, and the on-coming clutch is filled;
• and
• locking the on-coming clutch if the shift operation is completed using the on-coming clutch and said on-coming clutch slip is less than said predetermined slip threshold.