Fail-safe steering system for a vehicle

A fail-safe steering system for a vehicle comprising:

• first operating means for receiving and transmitting steering wheel torque;
• second operating means for transmitting torque;
• first steering means for transmitting torque;
• second steering means for steering steerable wheels of the vehicle;
• backup means for drivingly connecting the second operating means and the first steering means;
• first torque-transmitting means for selectively and operatively connecting and disconnecting the first operating means and the second operating means;
• and
• second torque-transmitting means for selectively and operatively connecting and disconnecting the first steering means and the second steering means.

A method of controlling a fail-safe steering system comprising a first operating member rotatable with a steering input device of the vehicle, a second operating member, a first steering member, a second steering member operatively associated with steerable wheels of the vehicle, for steering the steerable wheels, a backup mechanism having a portion connected to the second operating member and a portion connected to the first steering member, for transmitting torque between the second operating member and the first steering member, a first selectively engageable clutch mechanism operatively connectable between the first operating member and the second operating member, and a second selectively engageable clutch mechanism operatively connectable between the first steering member and the second steering member, the method comprising:

• enabling steer-by-control control when the system is turned on;
• disengaging the first clutch mechanism and the second clutch mechanism after the steer-by-wire control is enabled;
• determining whether or not an operating state of the backup mechanism is in a predetermined neutral condition;
• and
• engaging the second clutch mechanism and steering the steerable wheels based on the operating states of the vehicle when it is determined that the operating state of the backup mechanism is within the predetermined neutral condition.