Abstract: A vehicle includes a powerplant, an accelerator pedal, and a wheel driven by the powerplant. A vehicle controller is programmed to, while a position of the accelerator pedal is constant and responsive to cessation of slip of the driven wheel due to the driven wheel transitioning from a first surface to a second surface, command torque from the powerplant such that the torque increases at a rate that depends on a last learned value of a coefficient of friction of the first surface at the transitioning.

Abstract: Methods and systems for adjusting wheel torque to a driver demand wheel torque after the wheel torque has been reduced below the driver demand wheel torque are described. In one example, a rate at which wheel torque is returned to driver demand wheel torque is based on sign changes for wheel speed.

Abstract: Methods and system are described for allocating power to two electric machines when closing of a disconnect clutch is requested. In one example, the allocation of power may be based on a level of urgency for closing the disconnect clutch. Priority for supplying power to a secondary drive unit may be increased in response to a high urgency level.

Abstract: Methods and a system for estimating a coefficient of friction of a surface being traveled upon by a vehicle is disclosed. The methods and systems may be active when wheel slip is not present and while wheel slip is present. The coefficient of friction for the surface being traveled upon may be estimated as a function of time since a most recent wheel slip event.

Abstract: Methods and a system for estimating a coefficient of friction of a surface being traveled upon by a vehicle is disclosed. The methods and systems may be active when wheel slip is not present and while wheel slip is present. The coefficient of friction for the surface being traveled upon may be estimated as a function of time since a most recent wheel slip event.

Abstract: A method of controlling torque in an all-wheel-drive vehicle limits the duration of loss of traction. During wheel slip events, a controller reduces the commanded torque from a driver demanded level. The controller calculates a normalized wheels speed for each wheel based on a measured yaw rate, measured wheel speeds, and calculated wheel diameters. The controller determines the end of the wheel slip event by comparing the normalized speeds of each while to one another.

Abstract: An all-wheel-drive vehicle includes a primary axle operably coupled to an engine and a secondary axle having an input operably coupled to the engine a first halfshaft, a second halfshaft, a first clutch selectively connecting the first halfshaft to the input, and a second clutch selectively connecting the second halfshaft to the input. A transmission has an input coupled to the engine and output coupled to the primary drive axle. A driveshaft couples a power-transfer unit and the input, and a third clutch selectively couples the output to the driveshaft. A controller is programmed to, during a power-limiting routine, command a torque to the engine based on closed-loop feedback control such that the torque decreases when a calculated slip of a selected one of the first and second clutches is greater than a target slip of the selected clutch and increases when the calculated slip is less than the target slip.

Abstract: A vehicle includes a powertrain having a powerplant and a clutch that selectively couples the powerplant to an axle. A controller is programmed to, in response to the powertrain being in a power-limiting routine, command a torque to the powerplant based on an error between a target slip of the clutch and a slip of the clutch.