Friction engagement element control system and method of controlling friction engagement element

A method of controlling a friction engagement element including friction plates, which are an input-side friction plate and an output-side friction plate, and an actuation system configured to engage the input-side friction plate with the output-side friction plate with a pushing force, a characteristic formula defining a friction coefficient between the friction plates being a linear function having a negative slope in which the friction coefficient thereof decreases as a rotational difference between the friction plates increases, the method comprising:

• calculating the rotational difference between the friction plates;
• calculating a demanded transmission torque;
• determining that the friction engagement element is being engaged;
• responsive to determining that the friction engagement element is being engaged, calculating the pushing force based on the calculated rotational difference and the demanded transmission torque, such that a frictional force of the friction engagement element is controlled to decrease as the rotational difference decreases;
• and
• supplying the pushing force to the friction engagement element.