Patent ID: 8744683

Claim:
A control device for regulating or controlling a servo-drive unit in a steering system of a vehicle, the servo-drive unit being an electro servo unit, and wherein a steering angle preset by a driver is transferred from a steering shaft to a steering linkage to adjust a wheel steering angle at the steered wheels of the vehicle, and wherein a support moment is produced by the servo-drive unit that effects the steering linkage; wherein the control device is configured to determine an initial zero position of the steering shaft by evaluating a value of at least one vehicle state variable that is supplied to the control device, wherein an initial zero position is present if the at least one vehicle state variable lies within a defined range of values, wherein the at least one vehicle state variable is not a steering angle variable, and wherein the initial zero position is determined without using a steering angle sensor at the steering shaft, wherein the at least one vehicle state variable is at least one of: a steering moment, an engine moment of the servo-drive unit in the steering system, a lateral acceleration of the vehicle, and a yaw rate, and wherein an index signal is used for improving and checking plausibility of the value of the at least one vehicle state variable.