Patent ID: 8135526

Claim:
Method for controlling regenerative braking and friction braking in a vehicle, the vehicle comprising a powertrain system and a friction braking system communicating tractive torque with a driveline, the powertrain system including a torque machine, and an energy storage device connected to the torque machine, said torque machine communicating tractive torque with the driveline, the method comprising: monitoring a vehicle operating point; determining a braking torque request; determining a regenerative braking motor torque ratio based upon the vehicle operating point wherein the regenerative braking motor torque ratio is non-linearly dependent on the vehicle operating point; and actuating the friction brake based upon the regenerative braking motor torque ratio and the braking torque request, wherein the regenerative braking motor torque ratio is determined based upon the vehicle operating point such that a profile correlating the vehicle operating point to the regenerative braking motor torque ratio comprises a first region in which the regenerative braking motor torque ratio exponentially decreases with decreasing vehicle operating point, a second region in which the regenerative braking motor torque ratio decreases at a substantially constant rate with decreasing vehicle operating point, and a third region in which the regenerative braking motor torque ratio logarithmically decreases with decreasing vehicle operating point.