Method for Controlling a Brake Actuation of a Tractor-Trailer Combination

The present invention relates to a method for controlling the brake actuation of a brake system of tractor towing a trailer. The tractor only comprises an electro-mechanical brake system, whereas the trailer comprises a pneumatical brake system. The scope of the control is to keep the coupling force between the tractor and the trailer close to a desired coupling force. The brake force of the electro-mechanical brake actuators is directly measured by measuring the clamp force, the friction force and/or the position of an actuating element moving a brake pad towards a brake disk. On the basis of the measured brake force an approximated vehicle retardation is calculated. Furthermore, the actual vehicle retardation is measured. In case of the approximated vehicle retardation differing from the actual vehicle retardation this difference is taken as an indicator that it is necessary to change the actuation of the trailer brake system and/or the actuation of the electro-mechanical brake actuators of the tractor. The inventive method is useful for increasing the accuracy of the control of the brake actuation of a trailer and for approximating a desired coupling force between the tractor and the trailer.