Speed controlling an electric machine of a hybrid electric vehicle
A hybrid powertrain includes an engine having a crankshaft, and an electric motor having a rotor selectively coupled to the crankshaft via a disconnect clutch and configured to operate in torque control and in speed control. The powertrain further includes a transmission having a torque converter with an impeller fixed to the rotor, a turbine disposed on an input shaft of the transmission, and a bypass clutch configured to selectively transmit torque from the impeller to the turbine. A controller is configured to, in response to the motor switching from torque control to speed control, generate a torque command for the motor that defines a magnitude derived from an error between measured and estimated speeds of the impeller obtained during torque control to prevent a spike in motor speed when the motor switches from torque control to speed control.
1. A vehicle comprising:
an electric motor operable in torque control and speed control;
a torque converter having an impeller, a turbine, and a bypass clutch; and
a controller configured to, in response to the motor switching from torque control to speed control, generate a torque command for the motor based on a speed estimate correction, for the impeller, generated while the motor is in torque control and the bypass clutch is open or slipping.
2. The vehicle of claim 1 , wherein the speed estimate correction is derived from an error, between an estimated speed of the impeller and a measured speed of the impeller, obtained while the motor is in torque control.
3. The vehicle of claim 1 , wherein the torque command includes a feedforward component based on a driver-demanded torque, and a feedback component based on the speed estimate correction, wherein a magnitude of the torque command is equal to a sum of the feedforward component and the feedback component.
4. The vehicle of claim 3 , wherein the feedback component is further based on an error between a target speed of the impeller and a measured speed of the impeller obtained while the motor is in speed control.
5. The vehicle of claim 1 further comprising an engine selectively connected to the motor via a disconnect clutch.
6. The vehicle of claim 5 , wherein the controller is further configured to switch the motor from torque control to speed control in response to the engine being started.
7. The vehicle of claim 1 further comprising a transmission including an input shaft having the turbine disposed thereon.
8. The vehicle of claim 2 , wherein the estimated speed of the impeller is based on a speed of the turbine.
9. The vehicle of claim 2 , wherein the impeller is fixed to the motor, and further comprising a speed sensor disposed within the motor and configured to output a speed signal indicating a measured impeller speed.
10. A vehicle comprising:
an engine having a crankshaft;
an electric motor including a rotor selectively coupled to the crankshaft via a disconnect clutch and configured to operate in torque control and speed control;
a transmission including a torque converter having an impeller, a turbine disposed on an input shaft of the transmission, and a bypass clutch configured to selectively transmit torque from the impeller to the turbine; and
a controller configured to, in response to the motor switching from torque control to speed control, generate a torque command for the motor based on a speed estimate correction, for the impeller, generated while the motor is in torque control and the bypass clutch is open or slipping.
11. The vehicle of claim 10 , wherein the speed estimate correction is derived from an error, between an estimated speed of the impeller and a measured speed of the impeller, obtained while the motor is in torque control.
12. The vehicle of claim 10 , wherein the torque command includes a feedforward component based on a driver-demanded torque, and a feedback component based on the speed estimate correction, wherein a magnitude of the torque command is equal to a sum of the feedforward component and the feedback component.
13. The vehicle of claim 12 , wherein the feedback component is further based on an error between a target speed of the impeller and a measured speed of the impeller obtained while the motor is in speed control.
14. The vehicle of claim 11 , wherein the estimated speed of the impeller is based on a speed of the turbine.
15. The vehicle of claim 11 further comprising a speed sensor disposed within the motor and configured to output a speed signal indicating a measured impeller speed.
16. A vehicle comprising:
an electric motor operable in torque control and speed control;
a torque converter having an impeller, a turbine, and a bypass clutch; and
a controller configured to, in response to the motor switching from torque control to speed control, generate a torque command for the motor that defines a magnitude derived from an error between measured and estimated speeds of the impeller obtained during torque control to prevent a spike in motor speed when the motor switches from torque control to speed control.
17. The hybrid powertrain of claim 16 , wherein the controller is further configured to generate the torque command in response to the bypass clutch being open or slipping.
18. The hybrid powertrain of claim 16 , wherein the torque command further includes a feedforward component having a magnitude derived from a driver-demanded torque.
19. The hybrid powertrain of claim 18 , wherein the magnitude is equal to the feedforward component plus or minus a feedback component that is based on the error.
20. The hybrid powertrain of claim 19 , wherein the feedback component is further based on a difference between a target impeller speed and a measured impeller speed obtained during speed control.