Development of General Motors’ eAssist Gen3 Propulsion System

General Motors’ 3^rd generation eAssist propulsion systems build upon the experience gained from the 2^nd generation 115v system and the 1^st generation 36v system. Extensive architectural studies were conducted to optimize the new eAssist system to maintain the performance and fuel economy gains of the 2^nd generation 115v system while preserving passenger and cargo space, and reducing cost. Three diverse vehicle applications have been brought to production. They include two similar pickup trucks with 5.3 liter V8 engines and 8 speed transmissions, a 4-door passenger car with 2.5 liter 4 cylinder normally aspirated gasoline engine and a 6-speed automatic transmission, and a crossover SUV with a 2.0-liter turbocharged engine and 9 speed transmission. The key electrification components are a new water cooled induction motor/generator (MG), new water cooled power electronics module, and two major variants of 86v lithium ion battery packs. All three applications share variations of the same components, showing the bandwidth of the 3^rd generation system. The engines include special dual tensioner accessory drive systems to couple the MG to the crankshaft. The transmissions are all modified to support the eAssist system. The torque based control system of the 2^nd generation eAssist system was carried into these applications and integrated with the latest GM corporate common electrical and controls architectures.