Power demand and degradation information provision for a steering system of a road vehicle

A method to control a steering system or a sub-system of a road vehicle including a controller configured or programmed to operate in a normal mode with full steering functionality and no quality problems and at least two degraded operation modes with degraded operation of the steering system and an evaluator including an allocation between degradation levels of the steering system or the sub-system and operation modes, the method comprising:

• determining an overall degradation level for the steering system or the sub-system by collecting single individual degradation levels of the steering system or the sub-system in the evaluator;
• determining the overall degradation level as a level with a highest degradation of the single individual degradation levels which in a corresponding one of the operation modes provides enough performance of the steering system for an expected maximum power request;
• warning a driver of the road vehicle or transmitting the overall degradation level to another controller or a decision logic in the road vehicle when the overall degradation level is determined to correspond to an operation mode with degraded performance;
• wherein
• the steering system or the sub-system of the road vehicle includes a road wheel actuator which operates a gear rack via a rack-and-pinion gear.