Steering control system for vehicle

Abstract

A system for controlling steering of a vehicle, including a steering means such as a steering wheel with an electric motor which assists steering of the driven wheels of the vehicle, first steering control means for controlling the motor, a CCD camera for detecting a lane condition of a road on which the vehicle travels, a yaw rate sensor for detecting motion of the vehicle, steering assist torque calculating means for calculating a steering assist torque necessary for holding the lane, a torque sensor for detecting an actual steering torque manually applied to the steering means by the driver, and second steering control means for calculating a torque command to be output to the first steering control means based on the steering assist torque calculated by the steering assist torque calculating means and the actual steering torque such that the torque command decreases. In the system, the second steering control means transfers to the first steering control means an index indicative of a condition under which the steering assist torque was calculated, or an index indicative of an order in which the values of the steering assist torque are tansferred, thereby ensuring appropriate and highly reliable communication between the two control means.