Hybrid engine operation selection strategy for mitigation of driveline disturbance

1. Method to control a hybrid powertrain comprising an engine, an electric machine, and a transmission, the method comprising:

monitoring operation of the powertrain;

determining, by a processor, whether conditions necessary for growl to occur excluding motor torque and engine torque are present; and

if the conditions are present, controlling the powertrain based upon avoiding a powertrain operating region wherein the growl is enabled.

2. The method of claim 1 , wherein controlling the powertrain comprises controlling the powertrain to operate only outside of the powertrain operating region wherein the growl is enabled.

3. The method of claim 1 , wherein controlling the powertrain comprises:

assigning a control penalty to operation that would be inside the powertrain operating region wherein the growl is enabled; and

controlling the powertrain based upon the control penalty.

4. The method of claim 1 , wherein controlling the powertrain comprises:

operating the engine to solely serve an accessory/charge load; and

identifying a powertrain transition to transition the engine from the operation serving the accessory/charge load to an engine off state, wherein the powertrain transition remains outside of the powertrain operating region wherein the growl is enabled.

5. The method of claim 1 , wherein controlling the powertrain comprises:

monitoring an initial operating point of the powertrain;

monitoring a destination operating point for the powertrain;

determining a transition point to transition the powertrain from the initial operating point to the destination operating point while remaining outside of the powertrain operating region wherein the growl is enabled; and

controlling a powertrain transition from the initial operating point to the destination operating point based upon the transition point.

6. The method of claim 5 , wherein controlling the powertrain further comprises:

determining a plurality of transition points; and

controlling the powertrain transition based upon the transition points.

7. The method of claim 5 , further comprising monitoring an available battery power; and

controlling the powertrain transition from the initial operating point to the destination operating point based upon the available battery power.

8. The method of claim 1 , wherein the conditions necessary for growl to occur comprises the motor torque being less than a threshold motor torque; and

wherein the powertrain operating region wherein the growl is enabled is determined based upon the threshold motor torque.

9. The method of claim 8 , wherein the conditions necessary for growl to occur further comprises the engine torque being greater than a threshold engine torque; and

wherein the powertrain operating region wherein the growl is enabled is determined further based upon the threshold engine torque.

10. The method of claim 1 , wherein the conditions necessary for growl to occur comprise:

an output speed of the transmission between an identified minimum output shaft speed and an identified maximum output shaft speed;

clutches within the transmission engaged in a clutch state conducive to growl; and

motor torque within a threshold low motor torque range.

11. Method to control a hybrid powertrain comprising an engine, an electric machine, and a transmission, the method comprising:

monitoring operation of the powertrain;

determining, by a processor, whether conditions making growl more likely to occur excluding motor torque and engine torque are present; and

if said conditions are present, controlling the powertrain based upon avoiding a powertrain operating region wherein the growl is made more likely.