Multi-mode electromechanical variable transmission

A drive system for a vehicle having a drive axle, the drive system comprising:

• a first gear set including a first sun gear, a first ring gear, a first plurality of planetary gears coupling the first sun gear to the first ring gear, and a first carrier rotationally supporting the first plurality of planetary gears;
• a second gear set including a second sun gear, a second ring gear, a second plurality of planetary gears coupling the second sun gear to the second ring gear, and a second carrier rotationally supporting the second plurality of planetary gears, wherein the first carrier is directly coupled to the second carrier;
• a first electrical machine coupled to the first gear set;
• a second electrical machine coupled to the second gear set;
• a connecting shaft coupling an engine to the first gear set;
• a brake positioned to selectively limit a rotational movement of the second ring gear when engaged;
• a clutch selectively rotationally coupling the second electrical machine to the connecting shaft and the engine when engaged;
• and
• a controller configured to engage the clutch and the brake in response to an engine start request,
• wherein:
• the drive system is selectively reconfigurable into an active neutral startup mode of operation whereby at least one of the first electrical machine and the second electrical machine provide a startup power in response to a rotational input from the engine;
• and
• at least one of the first electrical machine and the second electrical machine is actuatable into a desired operating state in response to the startup power exceeding a threshold level.

A method of operating a multi-mode transmission, comprising:

• receiving an engine start request associated with an engine, wherein the engine is coupled to a first electromagnetic device through a first gear set;
• engaging a clutch to selectively rotationally couple a second electromagnetic device and a second gear set to the engine;
• engaging a brake to selectively limit a rotational movement of a ring gear of the second gear set, wherein a carrier of the second gear set is coupled to a carrier of the first gear set;
• generating a startup power by providing a rotational input to the first electromagnetic device with the engine;
• and
• activating at least one of the first electromagnetic device and the second electromagnetic device into a desired operating state with a controller in response to the startup power exceeding a threshold level.