Method for operating a steering system of a vehicle and vehicle steering system

A method for operating a steering system of a vehicle having a front-axle steering assembly, a rear-axle steering assembly, a steering wheel for issuing a steering command and an electric motor coupled to the steering wheel, the method comprising the following steps:

• a) detecting a failure of the front-axle steering assembly;
• b) in response to detecting the failure, locking an alignment of the front-axle assembly;
• c) steering the vehicle exclusively using the rear-axle steering assembly on the basis of the steering command issued by a driver via the steering wheel;
• d) continuously, by an on-board control, comparing at least one detected physical value of the steering command with at least one limit value derived from a maximum adjustment capability of the rear-axle steering assembly;
• and,
• e) upon the at least one detected physical value of the steering command reaching or exceeding at least one associated limit value, applying a torque acting on the steering wheel via the electric motor coupled to the steering wheel, wherein the torque counteracts the steering command and has a magnitude that is dynamically determined as a function of (i) the detected physical value and (ii) a current driving status comprising at least vehicle speed or slip angle, such that the torque limits further steering input that cannot be physically realized by the rear-axle steering assembly during the failure condition.