Brake assist during vehicle one pedal drive

Abstract

Responsive to accelerator pedal release and a speed of a vehicle being less than a threshold in a presence of indication that available powertrain torque has been reduced for at least a predetermined period of time during an absence of brake pedal engagement, a controller operates friction brakes to bring the vehicle to a stop. Responsive to accelerator pedal release and the speed being less than the threshold in an absence of the indication that available powertrain torque has been reduced and brake pedal engagement, the controller operates an electric machine and not the friction brakes to bring the vehicle to a stop.

What is claimed is: 
     
         1 . A vehicle comprising:
 an electric machine;   friction brakes; and   a controller programmed to,
 responsive to accelerator pedal release and a speed of the vehicle being less than a threshold in a presence of automatic operation of the friction brakes for at least a predetermined period of time absent brake pedal engagement, operate at least the friction brakes to bring the vehicle to a stop, and 
 responsive to accelerator pedal release and the speed being less than the threshold in an absence of (i) automatic operation of the friction brakes and (ii) brake pedal engagement, operate the electric machine and not the friction brakes to bring the vehicle to a stop. 
   
     
     
         2 . The vehicle of  claim 1 , wherein the controller is further programmed to, responsive to the speed being less than the threshold, accelerator pedal release, the absence of automatic operation of the friction brakes, the absence of brake pedal engagement, and a battery state of charge exceeding a state of charge threshold, operate the friction brakes to bring the vehicle to a stop. 
     
     
         3 . The vehicle of  claim 1 , wherein the controller is further programmed to, responsive to the speed being less than the threshold, accelerator pedal release, the absence of automatic operation of the friction brakes, the absence of brake pedal engagement, and a state of the electric machine, operate the friction brakes to bring the vehicle to a stop. 
     
     
         4 . The vehicle of  claim 3 , wherein the state of the electric machine is a temperature of the electric machine. 
     
     
         5 . A vehicle comprising:
 an electric machine;   friction brakes; and   a controller programmed to,
 responsive to a speed of the vehicle being less than a threshold, accelerator pedal release, an absence of indication that available powertrain torque has been reduced, an absence of brake pedal engagement, and a presence of indication that available powertrain stopping torque has been limited, operate the friction brakes to bring the vehicle to a stop, and 
 responsive to the speed being less than the threshold, accelerator pedal release, the absence of indication that available powertrain torque has been reduced, the absence of brake pedal engagement, and an absence of the indication that available powertrain stopping torque has been limited, operate the electric machine and not the friction brakes to bring the vehicle to a stop. 
   
     
     
         6 . The vehicle of  claim 5 , wherein the controller is further programmed to, responsive to accelerator pedal release and the speed being less than the threshold in a presence of the indication that available powertrain torque has been reduced for at least a predetermined period of time during an absence of brake pedal engagement, operate at least the friction brakes to bring the vehicle to a stop, wherein the predetermined period of time depends on a cause of the indication that available powertrain torque has been reduced such that the predetermined period of time is different for different causes of the indication. 
     
     
         7 . The vehicle of  claim 6 , wherein the cause is a traction control event. 
     
     
         8 . The vehicle of  claim 6 , wherein the cause is a brake drag control event. 
     
     
         9 . The vehicle of  claim 5 , wherein the indication that available powertrain stopping torque has been limited depends on a temperature of the electric machine.