Method for coupling a trailer to a towing vehicle, coupling control device and vehicle

A method for coupling a semi-trailer with a top plate to a truck tractor with a coupling plate includes: importing a reference height profile assigning a reference gradient to different actual values for the relative height of the chassis to the rear axle of the truck-tractor; changing the relative height such that the coupling plate approaches the top plate; continuously determining actual height values and height gradients while changing the relative height, wherein an actual height value is assigned the currently determined actual height gradient; checking a coupling criterion by comparing a currently determined actual height gradient with the reference gradient, wherein the reference gradient which in the imported reference height profile is assigned to the same actual height value as the currently determined actual height gradient is applied; and, maintaining the relative height when the currently determined actual height gradient deviates from the reference gradient.