Fault-tolerant strategies for double three-phase PMSM used in Electronic Power Steering systems

Safety-critical applications like Electronic Power Steering (EPS) systems demand highest reliability of electrical drives in automotive applications. Based on safety standards and associated requirements, the availability can be raised significantly through redundant system structures. In case of critical faults complete loss of steering assistance can be prevented by using different control methods and drive strategies adapted to the redundant structure. This paper shows fault-tolerant strategies for a double three-phase Permanent Magnet Synchronous Motor (PMSM) with independent motor windings and redundant voltage source inverters. Due to the redundant system structure and depending on critical faults it is possible to implement fault-tolerant methods. Fault compensation measures are discussed, making clear how unwanted effects on the steering torque can be contained. The new fault-tolerant strategies were performed on EPS systems to support fail-operational mode taking into account safety requirements.