Method and apparatus for controlling a multi-mode powertrain system to avoid an operating region

1. A method for controlling a powertrain system including an engine coupled to a multi-mode transmission configured to transfer tractive torque to an output member coupled to a ground wheel, comprising:

identifying an undesirable operating region for the multi-mode transmission conducive to driveline growl, the undesirable operating region defined by an input torque range and an output torque range; and

in response to a command to traverse the undesirable operating region from a first operating region to a second operating region, executing a fast engine torque transition including controlling the engine as a fast-adjusting torque actuator to control input torque from the engine to the multi-mode transmission and correspondingly controlling motor torque from a torque machine to the multi-mode transmission to maintain output torque from the multi-mode transmission responsive to an output torque request while traversing the undesirable operating region from the first operating region to the second operating region rapidly to minimize operating time in the undesirable operating region.

2. The method of claim 1 , further comprising pre-loading engine torque prior to executing the fast engine torque transition including controlling the engine as the fast-adjusting torque actuator to control the input torque to the multi-mode transmission.

3. The method of claim 2 , wherein pre-loading the engine torque prior to executing the fast engine torque transition comprises increasing engine torque capability by increasing an engine air torque and maintaining the input torque to the multi-mode transmission at an unchanged magnitude by retarding engine spark timing.

4. The method of claim 1 , wherein controlling the engine as the fast-adjusting torque actuator to control the input torque to the multi-mode transmission and correspondingly controlling the motor torque from the torque machine to the multi-mode transmission to maintain output torque from the multi-mode transmission responsive to the output torque request comprises increasing the input torque and correspondingly decreasing the motor torque.

5. The method of claim 1 , wherein controlling the engine as the fast-adjusting torque actuator to control the input torque to the multi-mode transmission and correspondingly controlling the motor torque from the torque machine to the multi-mode transmission to maintain the output torque from the multi-mode transmission responsive to the output torque request comprises decreasing the input torque and correspondingly increasing the motor torque.

6. The method of claim 1 , wherein controlling the engine and correspondingly controlling the torque machine to maintain output torque from the multi-mode transmission responsive to the output torque request while traversing the undesirable operating region from the first operating region to the second operating region rapidly to minimize operating time in the undesirable operating region comprises controlling the engine and correspondingly controlling the torque machine to traverse the undesirable operating region over a sufficiently brief period of time so as the motor torque does not fall in the undesirable operating range for enough time for driveline growl to take place.

7. The method of claim 1 , further comprising aborting the command to traverse the undesirable operating region when a commanded engine air torque fails to achieve a long-term engine torque request within a predetermined period of time.

8. A computerized process for controlling a powertrain system configured to transfer tractive torque to an output member coupled to a ground wheel of a vehicle, the process comprising:

within a computerized processor, identifying an undesirable operating region for a multi-mode transmission, the undesirable operating region conducive to driveline growl and defined by an input torque range and an output torque range;

in response to a command to traverse the undesirable operating region, controlling input torque from an engine configured to transfer torque to an input member of the multi-mode transmission as a fast-adjusting torque actuator and correspondingly controlling torque from a torque machine to the multi-mode transmission to maintain output torque from the multi-mode transmission; and

transitioning operation of the multi-mode transmission across the undesirable operating region from a first operating region to a second operating region rapidly to minimize the operating time of the multi-mode transmission in the undesirable operating region.

9. The method of claim 8 , further comprising pre-loading engine torque prior to executing the fast engine torque transition including controlling the engine as a fast-adjusting torque actuator to control the input torque to the multi-mode transmission.

10. The method of claim 9 , wherein pre-loading engine torque prior to executing the fast engine torque transition comprises increasing engine torque capability by increasing an engine air torque and maintaining the input torque to the multi-mode transmission at an unchanged magnitude by retarding engine spark timing.

11. The method of claim 8 , wherein controlling the engine as the fast-adjusting torque actuator to control the input torque to the multi-mode transmission and correspondingly controlling the motor torque from the torque machine to the multi-mode transmission to maintain output torque from the multi-mode transmission responsive to an output torque request comprises increasing the input torque and correspondingly decreasing the motor torque.

12. The method of claim 8 , wherein controlling the engine as the fast-adjusting torque actuator to control the input torque to the multi-mode transmission and correspondingly controlling the motor torque from the torque machine to the multi-mode transmission to maintain output torque from the multi-mode transmission responsive to an output torque request comprises decreasing the input torque and correspondingly increasing the motor torque.

13. The method of claim 8 , wherein controlling the engine and correspondingly controlling the torque machine to maintain output torque from the multi-mode transmission responsive to an output torque request while traversing the undesirable operating region from the first operating region to the second operating region rapidly to minimize the operating time of the multi-mode transmission in the undesirable operating region comprises controlling the engine and correspondingly controlling the torque machine to traverse the undesirable operating region over a sufficiently brief period of time so as the motor torque does not fall in the undesirable operating range for enough time for driveline growl to take place.

14. The method of claim 8 , further comprising aborting the command to traverse the undesirable operating region when a commanded engine air torque fails to achieve a long-term engine torque request within a predetermined period of time.

15. The method of claim 8 , wherein identifying an undesirable operating region for the multi-mode transmission including the input torque range and the output torque range comprises identifying the operating region associated with objectionable driveline growl in an off-line environment.