One-pedal drive control on grade

1 . A vehicle comprising:

an electric machine configured to propel the vehicle; and

a controller programmed to,

while only front wheels of the vehicle are on a ramp being entered and climbed by the vehicle and a first ramp compensation torque is being commanded to the electric machine, reduce the first ramp compensation torque responsive to a rate of increase of the first ramp compensation torque exceeding a first rate threshold, and

while only rear wheels of the vehicle are on the ramp and a second ramp compensation torque is being commanded to the electric machine, responsive to a rate of decrease of the second ramp compensation torque exceeding a second rate threshold, reduce the second ramp compensation torque.

2 . The vehicle of claim 1 , wherein a magnitude of the first rate threshold is greater than a magnitude of the second rate threshold.

3 . The vehicle of claim 1 , wherein the controller is further programmed to operate the vehicle in a one-pedal drive mode during the reduction.

4 . The vehicle of claim 3 , wherein the controller is further programmed to selectively exit the one-pedal drive mode.

5 . The vehicle of claim 1 , wherein the rate is a quotient of the first ramp compensation torque and a distance traveled.

6 . A method comprising:

applying a first ramp compensation torque to an electric machine of a vehicle operating in a one-pedal drive mode while entering a ramp climb; and

responsive to a rate of increase of the first ramp compensation torque exceeding a first rate threshold, reducing the first rate compensation torque such that the rate becomes less than the first rate threshold, wherein the rate is a quotient of the first ramp compensation torque and a distance traveled.

7 . The method of claim 6 , further comprising:

applying a second ramp compensation torque to the electric machine while exiting the ramp climb; and

responsive to a rate of decrease of the second ramp compensation torque exceeding a second rate threshold, reducing the second rate compensation torque such that the rate of decrease becomes less than the first rate threshold.

8 . The method of claim 7 , wherein a magnitude of the first rate threshold is greater than a magnitude of the second rate threshold.

9 . The method of claim 6 , further comprising:

selectively exiting the one-pedal drive mode.

10 . A powertrain system of a vehicle, comprising:

a controller programmed to, while operating the vehicle in a one-pedal drive mode, responsive to detecting front wheels of the vehicle having entered a ramp and rear wheels of the vehicle not having entered the ramp, command a first torque compensation to an electric machine, and responsive to an increase of the first torque compensation at a rate exceeding a first threshold, reduce a magnitude of the first torque compensation until the rear wheels have entered the ramp.

11 . The powertrain system of claim 10 , wherein the controller is further programmed to, while operating the vehicle in the one-pedal drive mode, responsive to detecting front wheels of the vehicle having exited the ramp and rear wheels of the vehicle not having exited the ramp, command a second torque compensation to the electric machine, and responsive to decrease of the second torque compensation at a rate exceeding a second threshold, reduce a magnitude of the second torque compensation until the rear wheels have exited the ramp.

12 . The powertrain system of claim 11 , wherein a magnitude of the first threshold is greater than a magnitude of the second threshold.

13 . The powertrain system of claim 10 , wherein the controller is further programmed to operate the vehicle in a one-pedal drive mode during the reduction.

14 . The powertrain system of claim 13 , wherein the controller is further programmed to selectively exit the one-pedal drive mode.

15 . The powertrain system of claim 10 , wherein the rate is a quotient of the first compensation torque and a distance traveled.