Fault-tolerant switched reluctance motor propulsion system for eVTOLs

eVTOLs are receiving a lot of attention as a potential solution to urban air mobility challenges. Many configurations are multirotors, which are open loop unstable, therefore very susceptible to actuator failures. Due to their usually short mission duration (20-30 min), fault-tolerance of the propulsion system is of greater importance then reliability. Thus, novel approaches to enhance this capability are required. This study proposes a new fault-tolerant propulsion system using 4-phase switched reluctance motors. It is designed for an 8-10 kg scale multirotor eVTOL, to replace redundant coaxial brushless DC motors with a single fault-tolerant drive. Acknowledging the role of fault-tolerant control algorithms, the propulsion system is validated in terms of the loss of effectiveness metric, typically used in the evaluation of control solutions. The switched reluctance motor propulsion system was found to be highly resilient to open phase and current sensor faults, but susceptible to position sensor faults. This can, however, be mitigated with sensorless control solution. Extending the findings to full-scale eVTOLs is also discussed.