Engine Stall Recovery and Restart Procedure for Hybrid Electric Vehicles 2024-01-2783

Engine stall, a noteworthy occurrence in traditional vehicles, poses challenges due to the inability to disconnect the engine from the driveline. Consequently, in such scenarios, the vehicle experiences a loss of propulsion, necessitating the driver to pull over. The severity of propulsion loss events is underscored by regulatory bodies like the National Highway Traffic Safety Administration (NHTSA), potentially leading to costly recalls for Automotive Manufacturers. Therefore, proactive measures to avert Loss of Propulsion (LoP) events, including the exploration of remedial actions, are strongly encouraged during powertrain controls design. In contrast, hybrid electric vehicles offer a unique advantage. Given the ability to connect or disconnect the engine from the driveline in hybrid or electric-only modes, an engine stall in hybrid mode need not result in a complete loss of propulsion. In such situations, a hybrid electric vehicle can seamlessly transition to electric-only mode while concurrently attempting an engine restart. However, a predefined safety procedure must be adhered to, involving the disconnection of the engine from the driveline and its shutdown before initiating a restart. Considering diverse propulsion architectures and hybrid types like mild hybrid or plug-in hybrids, Stellantis Hybrid Torque Control employs a sophisticated software strategy. This strategy orchestrates the seamless disconnection of the engine from the driveline and preserves the engine restart functionality. Following a successful restart, the engine is reconnected to the driveline, allowing the resumption of normal driving operations. This paper illustrates the application of such a strategy with a case study example for P1P2 hybrid architecture, supported by vehicle validation data encompassing multiple engine stalls in a single drive cycle and the subsequent successful recovery of the engine in these scenarios.