The present invention relates to a system and method of implementing fault detection and management strategy for sensor faults of a vehicle steer-by-wire system.
Steer-by-wire systems are becoming more common in the automotive industry. Steer-by-wire systems replace the mechanical linkage between a steering wheel and road wheels of a vehicle with electrical connections and components including road wheel actuators, road wheel position sensors, steering wheel position sensors, power electronic drivers, and electronic control units.
Due to the criticality of steering functionality, it is important that system designs provide safe handling of failures. For instance, during normal operation, a vehicle steer-by-wire system may experience component failure, e.g., a sensor fault, and should be capable of responding safely. Currently, many steer-by-wire systems include a redundancy of sensors, e.g., triple redundancy, to enable detection, isolation and management of faults including sensor faults. A vehicle steer-by-wire system having triple redundant sensors include three sensors configured to input data of one, vehicle variable, e.g., road wheel position. As such, one of the sensors may experience a fault which could be easily detected by comparison of the signals generated by all three sensors. Although adequate, a triple redundancy strategy involves relatively high costs and large volume density within a vehicle.
Steer-by-wire systems with double redundancy sensors typically have relatively limited capability. For example, a double redundancy fault detection system may only be capable of detecting a limited set of faults where the faulted sensor value is outside of its normal operating window. Thus, common faults such as drifting are still a concern in double redundancy systems.
Thus, it is one aspect of the present invention to provide a fault detection and management strategy for road wheel position sensor faults of a vehicle steer-by-wire system to reduce volume density and costs.
It is another aspect of the present invention to provide a fault detection and management strategy for road wheel position sensor faults of a vehicle steer-by-wire system to reduce the redundancies.
It is yet another aspect of the present invention to provide a fault detection and management strategy for road wheel position sensor faults of a vehicle steer-by-wire system having a reduced number of sensors while maintaining fault detection capabilities of a triple redundancy system.
One method of the present invention includes providing primary and secondary road wheel sensors configured to generate road wheel angle signals indicative of a road wheel angle to a microprocessor. In this embodiment, the primary road wheel sensor is in an active control mode and the secondary road wheel sensor is in a stand-by control mode within the steer-by-wire system. The method further includes receiving road wheel angle signals from the primary and secondary sensors and detecting a fault based on the road wheel angle signals from the primary and secondary sensors. The method further includes calculating an estimated road wheel angle based on a vehicle variable and comparing the primary sensor signal with the estimated road wheel angle. The method further includes managing control of the system based on the comparison of the primary sensor signal with the estimated road wheel angle.
Further objects, features and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.
FIG. 1 is a schematic diagram of an assembly for a vehicle steer-by-wire system implementing a fault detection and management strategy in accordance with one embodiment of the present invention;
FIG. 2 is a control logic diagram of the steer-by-wire system of FIG. 1 implementing the fault detection and management strategy for road wheel position sensor faults in accordance with one embodiment of the present invention; and
FIG. 3 is a flow-chart depicting one method of implementing the fault detection and management strategy for road wheel position sensor faults of the steer-by-wire system in FIG. 2.