Normalizing deceleration of a vehicle having a regenerative braking system
A method of operating a vehicle having a friction braking system and a regenerative braking system is presented here. The method determines a regenerative torque capacity, calculates a desired regenerative torque amount for the braking system, detects that the desired regenerative torque amount exceeds the regenerative torque capacity by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting. Another operating method determines a coastdown torque capability of the vehicle, calculates a desired coastdown torque amount, detects that the desired coastdown torque amount exceeds the coastdown torque capability by at least a threshold amount, and controls actuation of the friction braking system in response to the detecting.
1. A method of operating a vehicle having a friction braking system and a regenerative braking system, the method comprising:
determining a regenerative torque capacity of the vehicle;
calculating a desired regenerative torque amount for the regenerative braking system;
setting a threshold amount as a function of vehicle speed;
detecting that the calculated desired regenerative torque amount exceeds the determined regenerative torque capacity by at least the threshold amount; and
in response to the detecting, controlling actuation of the friction braking system.
2. The method of claim 1 , wherein the determined regenerative torque capacity is based on a current operating state of the vehicle.
3. The method of claim 1 , wherein the calculated desired regenerative torque amount is based on a current operating state of the vehicle.
4. The method of claim 1 , wherein the calculating calculates a desired coastdown regenerative torque amount that corresponds to a coastdown state of the vehicle.
5. The method of claim 4 , wherein the calculating calculates the desired coastdown regenerative torque amount as a function of vehicle speed and accelerator pedal travel.
6. The method of claim 1 , wherein the calculating calculates a desired braking regenerative torque amount that corresponds to an active braking state of the vehicle.
7. The method of claim 6 , wherein the calculating calculates the desired braking regenerative torque amount as a function of brake pedal travel.
8. The method of claim 1 , wherein the threshold amount is a static value.
9. A vehicle comprising:
a road wheel;
an energy storage system (ESS);
an electric motor/generator mechanically coupled to the road wheel and electrically coupled to the ESS;
a friction braking system for the road wheel; and
a regenerative control system for the ESS, wherein the regenerative control system is operable to implement a method comprising:
determining a regenerative torque capacity of the vehicle;
calculating a desired regenerative torque amount for the regenerative braking system;
setting a threshold amount as a function of vehicle speed;
detecting that the calculated desired regenerative torque amount exceeds the determined regenerative torque capacity by at least the threshold amount; and
in response to the detecting, controlling actuation of the friction braking system.
10. The vehicle of claim 9 , wherein the calculating calculates a desired coastdown regenerative torque amount that corresponds to a coastdown state of the vehicle.
11. The vehicle of claim 10 , wherein:
the calculating calculates the desired coastdown regenerative torque amount as a function of vehicle speed and accelerator pedal travel; and
controlling actuation of the friction braking system comprises:
generating a friction brake torque command as a function of vehicle speed and accelerator pedal travel; and
actuating the friction braking system in response to the friction brake torque command.
12. The vehicle of claim 9 , wherein the calculating calculates a desired braking regenerative torque amount that corresponds to an active braking state of the vehicle.
13. The vehicle of claim 12 , wherein:
the calculating calculates the desired braking regenerative torque amount as a function of brake pedal travel; and
controlling actuation of the friction braking system comprises:
generating a friction brake torque command as a function of brake pedal travel; and
actuating the friction braking system in response to the friction brake torque command.
14. A method of operating a vehicle having a friction braking system, the method comprising:
determining a coastdown torque capability of the vehicle;
calculating a desired coastdown torque amount for the vehicle;
setting a threshold amount as a function of vehicle speed;
detecting that the calculated desired coastdown torque amount exceeds the determined coastdown torque capability by at least the threshold amount; and
in response to the detecting, controlling actuation of the friction braking system.
15. The method of claim 14 , wherein the determined coastdown torque capability is based on a current operating state of the vehicle.
16. The method of claim 14 , wherein the calculated desired coastdown torque amount is based on a current operating state of the vehicle.
17. The method of claim 14 , wherein the calculating calculates the desired coastdown torque amount as a function of vehicle speed and accelerator pedal travel.
18. The method of claim 14 , wherein the threshold amount is a static value.