Patent ID: 8397858

Claim:
A steering system comprising: a steering wheel; a steer-by-wire (SBW) valve in electrical communication with the steering wheel; a main steering pump in fluid communication with the SBW valve; a steering actuator in fluid communication with the main steering pump via the SBW valve; a steering control unit (SCU) in fluid communication with the steering actuator via a pair of fluid conduits, and having: an upper portion containing a first solenoid valve and a cross-over check valve assembly arranged between the pair of fluid conduits; and a lower portion containing a fluid control valve coupled to the steering wheel, and in fluid communication with the steering actuator via the cross-over check valve assembly; and an electronic control unit (ECU) configured for: generating a steering input signal in response to a rotation of the steering wheel; transmitting the steering signal input to the SBW valve to thereby selectively admit fluid to the SBW valve from the main steering pump; determining a predetermined condition in which at least one of the SBW valve and the main steering pump has failed; selectively controlling the first solenoid valve to a first state to deliver fluid from the lower portion of the SCU to the steering actuator via the cross-over valve assembly, and to thereby provide an emergency steering mode during the predetermined condition; and selectively controlling the first solenoid valve to one of the first state and a second state to thereby prevent fluid flow into the steering actuator, and to allow a recirculation of fluid within the lower portion of the SCU, thereby providing a torque feel mode.