Abstract: A method to start operation of an internal combustion engine of a hybrid powertrain includes initiating rotation of a crankshaft of the engine with at least one electric machine in accordance with a first ramping profile until a first predetermined speed is achieved in response to an engine start event during a cold start condition. Engine speed is monitored and the engine is fired while controlling the engine speed to maintain the first predetermined speed with the at least one electric machine. The first ramping profile is adjusted at a rate corresponding to an estimated rate at which the engine speed is increasing during the engine firing. When at least one predetermined combustion quality parameter is achieved, the engine speed is controlled in accordance with a second ramping profile until a second predetermined speed is achieved based on controlling combustion parameters of the engine.

Abstract: A method to start operation of an internal combustion engine of a hybrid powertrain includes initiating rotation of a crankshaft of the engine with at least one electric machine in accordance with a first ramping profile until a first predetermined speed is achieved in response to an engine start event during a cold start condition. Engine speed is monitored and the engine is fired while controlling the engine speed to maintain the first predetermined speed with the at least one electric machine. The first ramping profile is adjusted at a rate corresponding to an estimated rate at which the engine speed is increasing during the engine firing. When at least one predetermined combustion quality parameter is achieved, the engine speed is controlled in accordance with a second ramping profile until a second predetermined speed is achieved based on controlling combustion parameters of the engine.

Abstract: An example hybrid vehicle includes a control unit that generates a control signal representing an expected torque, a first actuator that generates a first torque, a second actuator that generates a second torque associated with operating characteristics of the second actuator, and a gearbox that can receive the torque generated by the first and second actuators. A controller can determine whether the first torque produced by the first actuator is substantially the same as the expected torque based on one or more operating characteristics of the second actuator. An example method includes deriving an actual torque of the first actuator based on the operating characteristics of the second actuator, defining a torque deviation from the actuator torque and the expected torque, comparing the torque deviation to a calibration threshold, and diagnosing that the first actuator has failed if the torque deviation exceeds the calibration threshold.

Abstract: A hybrid powertrain system includes an internal combustion engine operatively connected to a second torque machine to transmit torque to an output member. A method for operating the hybrid powertrain system includes monitoring an operator torque request, determining an output torque command based upon the operator torque request, commanding a transition between an engine-off state and an engine-on state, monitoring an engine crank angle, spinning the engine unfueled, estimating cylinder pressure based upon the engine crank angle during the spinning of the engine, predicting a cylinder pulse torque based upon the cylinder pressure, determining a cancellation torque for the second torque machine based upon the predicted cylinder pulse torque, and controlling motor torque output from the second torque machine based upon the cancellation torque and the output torque command.

Abstract: A hybrid powertrain system includes an internal combustion engine operatively connected to a second torque machine to transmit torque to an output member. A method for operating the hybrid powertrain system includes monitoring an operator torque request, determining an output torque command based upon the operator torque request, commanding a transition between an engine-off state and an engine-on state, monitoring an engine crank angle, spinning the engine unfueled, estimating cylinder pressure based upon the engine crank angle during the spinning of the engine, predicting a cylinder pulse torque based upon the cylinder pressure, determining a cancellation torque for the second torque machine based upon the predicted cylinder pulse torque, and controlling motor torque output from the second torque machine based upon the cancellation torque and the output torque command.