Hybrid powertrain speed control
In at least one embodiment, a vehicle powertrain includes an engine and an electric machine mechanically coupled by a clutch. The powertrain also includes a torque converter configured to fluidly couple the electric machine to an output shaft. A controller is programmed to command a rotational speed output of the electric machine to the torque converter based on a predicted torque delivered across the clutch. The controller is further programmed to modify the command based on a difference between the commanded rotational speed output and an actual rotational speed output of the electric machine.
1. A hybrid powertrain control method comprising:
issuing commands for an engine to generate and deliver an estimated torque across a clutch;
issuing a command for an electric machine to output rotational speed based on the estimated torque delivered across the clutch;
measuring actual rotational speed of the electric machine;
providing feedback from a feedback loop indicating a discrepancy between the commanded and actual rotational speeds; and
modifying the command for the electric machine to minimize the discrepancy.
2. The method of claim 1 further comprising, during vehicle travel speeds less than a speed threshold, issuing a command for the electric machine to output a rotational speed that is greater than a predetermined minimum rotational speed irrespective of the discrepancy.
3. The method of claim 1 wherein the hybrid powertrain includes a variable gear ratio transmission, and the method further comprising issuing a command for the electric machine to ramp up the rotational speed in response to the transmission shifted from a non-motive gear to a motive gear.
4. The method of claim 1 wherein the hybrid powertrain includes a torque converter configured to fluidly couple the electric machine to a powertrain output shaft, and in response to a downshift of a transmission gear ratio during vehicle travel speed less than a speed threshold, the command for the electric machine causes a predetermined rotational speed during a disengagement of the torque converter.
5. The method of claim 4 wherein the predetermined rotational speed of the electric machine comprises one of a constant speed or a speed profile having a rate of change less than a roughness threshold.
6. The method of claim 1 wherein the hybrid powertrain includes a torque converter configured to fluidly couple the electric machine to a powertrain output shaft, and during a powertrain idle condition, a combination of the commands for each of the engine and the electric machine causes an impeller speed of the torque converter to be greater than a predetermined minimum impeller speed.
7. The method of claim 1 further comprising, in response to the rotational speed of the electric machine being less than a threshold, disregarding the discrepancy between the commanded rotational speed and the actual rotational speed of the electric machine for a predetermined period of time.
8. A hybrid powertrain control method comprising:
issuing commands for an engine to generate and deliver an estimated torque across a clutch;
issuing a command for an electric machine to output rotational speed based on the estimated torque delivered across the clutch;
measuring actual rotational speed of the electric machine;
providing feedback from a feedback loop indicating a discrepancy between the commanded and actual rotational speeds;
modifying the command for the electric machine to minimize the discrepancy; and
in response to a downshift of a transmission gear ratio during vehicle travel speed less than a speed threshold, the command for the electric machine causes a predetermined rotational speed during a disengagement of a torque converter that is configured to fluidly couple the electric machine to a powertrain output shaft.
9. The method of claim 8 further comprising, during vehicle travel speeds less than a speed threshold, issuing a command for the electric machine to output a rotational speed that is greater than a predetermined minimum rotational speed irrespective of the discrepancy.
10. The method of claim 8 wherein the hybrid powertrain includes a variable gear ratio transmission, and the method further comprising issuing a command for the electric machine to ramp up the rotational speed in response to the transmission shifted from a non-motive gear to a motive gear.
11. The method of claim 8 wherein the predetermined rotational speed of the electric machine comprises one of a constant speed or a speed profile having a rate of change less than a roughness threshold.
12. The method of claim 8 wherein the hybrid powertrain includes a torque converter configured to fluidly couple the electric machine to a powertrain output shaft, and during a powertrain idle condition, a combination of the commands for each of the engine and the electric machine causes an impeller speed of the torque converter to be greater than a predetermined minimum impeller speed.
13. The method of claim 8 further comprising, in response to the rotational speed of the electric machine being less than a threshold, disregarding the discrepancy between the commanded rotational speed and the actual rotational speed of the electric machine for a predetermined period of time.