Dual clutch transmissions are a type of transmission employing two input clutches which connect a pair of input shafts to the prime mover, typically an internal combustion engine.  One clutch is used for odd numbered gears, and the other clutch is used for even numbered gears.  Synchronizers establish power flow paths between the input shafts and the transmission output.  While the vehicle is driving in an odd numbered gear, the synchronizers for the even numbered gears may be manipulated to select the next higher or lower gear ratio, and vice versa. 
For any dual clutch transmission, the ability to precisely actuate clutch capacity is important for drivability and shift quality.  For a hybrid powertrain with two input clutches for engine connection and disconnection to the transmission, it is important to be able to restart the engine and connect the disconnect clutch smoothly and quickly when engine operation is desired, to provide vehicle operator requested torque and acceleration.  Similarly, during gear shift events, accurate knowledge of clutch capacity is important for smooth transitions from one gear ratio to another.  Part-to-part variability and change over time are significant noise factors for clutch capacity control and estimation. 
Typically, vehicles with a dual clutch transmission are controlled to find opportunities for clutch adaptation during transient operation, usually in non-intrusive schemes.  Most of these schemes adapt while the clutch is transmitting positive torque to the wheels, but the clutch transfer function for both positive and negative slip/torque is important for consistent operation and shift quality.  For a vehicle comprising powertrain components including a belt integrated starter/generator (BISG) or a crank integrated starter/generator (crank ISG), and an electric machine positioned in the driveline downstream of a dual clutch transmission, opportunities for clutch adaptation may occur less frequently.  However, a vehicle with such an architecture may provide increased flexibility in how torque is delivered to the wheels, and may further provide unique opportunities to perform clutch adaptation as compared to a non-hybridized vehicle. 
The inventors herein have recognized these issues, and have developed systems and methods to address the above issues.  In one example, a driveline operating method for a vehicle is provided comprising operating a first clutch of a dual clutch transmission at a selected capacity to change a speed of a first transmission input shaft to a desired speed, adjusting values of a torque transfer function of the first clutch based on a rate of the speed change, and maintaining driver demanded wheel torque during the adjusting via controlling torque output of an electric motor positioned in the driveline.  In this way, clutch capacity may be utilized to control speed of the first input shaft such that values of a torque transfer function may be adjusted, while maintaining driver demanded wheel torque. 
As one example, changing speed of the first transmission input shaft to the desired speed includes decreasing speed of the first transmission input shaft to the desired speed responsive to transmission input shaft speed being greater than the desired speed, and further responsive to a speed of a combustion engine positioned upstream of the transmission being lower than the desired speed.  In another example, changing speed of the first input shaft to the desired speed includes increasing speed of the transmission input shaft to the desired speed responsive to transmission input shaft speed being lower than the desired speed, and further responsive to engine speed being greater than the desired speed. 
In this way, a pressure to torque transfer function may be adapted under conditions where the first input shaft is either increased to a desired speed, or decreased to a desired speed.  Accordingly, both positive and negative torque transfer functions may be adapted according to the systems and methods depicted herein. 
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. 
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description.  It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description.  Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.