Method and apparatus for power flow management in electro-mechanical transmissions

A method for series hybrid operation in a power transmission system including an engine having an output shaft, a pair of planetary units between the engine output shaft and an output drive shaft, each planetary unit having a ring member located around a sun member, planet members located between the sun and ring members, and a carrier member coupled with the planets and providing axes about which the planet members rotate, one of the members of the first planetary unit engageable with one of the members of the second planetary unit to form a first compound member branch, another of the members of the first unit engageable with another of the members of the second planetary unit to form a second compound branch, a first electric machine coupled to the sun member of the first planetary unit, and a second electric machine coupled to the sun member of the second planetary unit, a power control unit coupled to the first and second electric machines, the method comprising:

• decoupling said first and second planetary trains from each other;
• configuring said first planetary train as a speed increaser;
• driving said first electric machine from said engine output shaft through said first planetary train to generate electrical power;
• configuring said second planetary train as a speed reducer;
• delivering said electrical power from said first electric machine to said second electric machine;
• driving said output drive shaft from said second electric machine through said secondary planetary train;
• and
• regulating said generation and delivery of electrical power from said first electric machine to said second electric machine to control said output drive shaft rotational speed.

A method for power regulation in a power transmission system including an engine having an output shaft, a pair of planetary units between the engine output shaft and an output drive shaft, each planetary unit having ring member located around a sun member, planet members located between the sun and ring members, and a carrier member coupled with the planets and providing axes about which the planet members rotate, at least one of the members of the first planetary unit engagable with one of the members of the second planetary unit to form a compound member branch, a first electric machine coupled to one member of the first planetary unit, and a second electric machine coupled to one member of the second planetary unit, a power control unit coupled to the first and second electric machines, the method comprising:

• identifying the output drive shaft rotational speed and driver inputs;
• calculating engine output utilizing said output drive shaft rotational speed and at least one driver input;
• determining a engine operating point based on a selected performance objective;
• calculating a speed ratio between said output drive shaft and said engine output shaft;
• selecting an operating regime for said power transmission system based upon said calculated speed ratio;
• selecting a control routine for each of said first and second electric machines based upon said calculated speed ratio;
• controlling one of said electric machines to provide torque to regulate said engine rotational speed based upon said operating regime and control routines;
• controlling a second of said electric machines to provide torque to balance power in said first and second planetary units based upon said operating regime and control routines;
• and
• regulating the engine to achieve a desired engine output torque based on a selected performance objective.