Steering control apparatus
An improved steering control apparatus is provided, wherein a driver can easily operate a steering wheel while the automatic steering mode is active so as to steer the vehicle in coping with any situation. The steering control system 41 that is provided in the steering control apparatus can determine whether a driver operates a steering wheel 33 by checking whether the electric current command value I 1 for the assist control is more than a predetermined threshold value K 1 while the automatic steering mode is active. And, as the operation of the steering wheel 33 is given precedence to continuation of the automatic steering control in determining whether the steering control apparatus 11 is changed from the automatic steering mode to the manual steering mode, the driver can easily rotate the steering wheel 33 in a state where the electric motor 19 generates enough assist force.
1 . A steering control apparatus for an automobile vehicle provided with a steering control system for changing the steering control apparatus between the manual steering mode wherein an electric motor assists driver's steering operation to steer steered wheels under assist control and an automatic steering mode wherein the steered wheels are steered by the electric motor under positioning control to run the vehicle to a predetermined target position without the driver's manual steering operation, wherein the steering control system comprising:
an assist control section for calculating an electric current command value for the assist control based on a loaded torque applied to a rotational shaft of a steering wheel;
a positioning control section for calculating an electric current command value for the positioning control based on a deviation between a target steering angle determined according to the target position and an actual steering angle of the steered wheels;
an electric current changeover section for outputting the electric current command value for the assist control as an electric current command value for the electric motor in the manual steering mode and the sum of the electric current command value for the assist control and the electric current command value for the positioning control as the electric current command value for the electric motor in the automatic steering mode;
a command value checking section for determining whether the electric current command value for the assist control is more than a predetermined threshold value in the automatic steering mode; and
the electric current changeover section being operable to change the steering control apparatus from the automatic steering mode to the manual steering mode when the electric current command value for the assist control is more than the predetermined threshold value while the automatic steering mode is active, and to continue the automatic steering mode when the electric current command value for the assist control is not more than the predetermined threshold value while the automatic steering mode is active.
2 . The steering control apparatus as set forth in claim 1 , wherein the electric current changeover section is operable to change the steering control apparatus from the automatic steering mode to the manual steering mode by stopping output of the electric current command value for the positioning control from the positioning control section, and to continue the automatic steering mode by allowing the output of the electric current command value for the positioning control from the positioning control section.
3 . The steering control apparatus as set forth in claim 2 , wherein the positioning control section comprises a time-integrated value calculating section for varying the electric current command value for the positioning control according to the time-integrated value calculated by integrating the deviation with respect to time, and
a time-integrated value reset section for resetting a last time-integrated value before the automatic steering mode is resumed from the manual steering mode.
4 . The steering control apparatus as set forth in claim 1 , wherein the electric current changeover section causes the steering control system to output an informing signal for informing the changeover from the automatic steering mode to the manual steering mode.