Patent ID: 7322439

Claim:
A steering apparatus for a steerable vehicle, comprising: a steering unit configured to generate an assist steering effort to regulate a steer angle of the vehicle; an operating unit configured to receive a manual steering effort; a backup unit configured selectively to mechanically connect the steering unit and the operating unit, and to mechanically separate the steering unit from the operating unit; and a control unit connected electrically for signal communication to the steering unit, the operating unit, and the backup unit, and operable in at least two control modes including an SBW mode and a PS mode, the control unit being configured when in the SBW mode to: mechanically separate the steering unit from the operating unit; control the steer angle in accordance with the manual steering effort; determine whether or not an SBW-to-PS mode switch condition is satisfied, the SBW-to-PS mode switch condition being a condition that the steer angle is larger than or equal to a first threshold angle; and switch the control mode from the SBW mode to the PS mode when it is determined that the SBW-to-PS mode switch condition is satisfied, and the control unit being configured when in the SBW mode to: mechanically connect the steering unit and the operating unit; control the assist steering effort to boost the manual steering effort; determine whether or not a PS-to-SBW mode switch condition is satisfied, the PS-to-SBW mode switch condition being a condition that the steer angle is smaller than or equal to a second threshold angle; and switch the control mode from the PS mode to the SBW mode when it is determined that the PS-to-SBW mode switch condition is satisfied.