A novel control device for a vehicle power steering apparatus or system is improved
for providing preferable steering convergnecy even under the execution of VSC,
while ensuring the steering smoothness under normal running conditions. In the
control device, the target value of total modification torque to be added to steering
torque through an power steering apparatus, is calculated based upon steering assist
torque, calculated based upon at least steering torque; steering converging torque,
based upon a steering velocity; and behavioral deterioration-suppressing torque
for suppressing unwanted steering motions which would cause further deterioration
of a vehicle behavior under oversteered or understeered conditions. In this calculation,
when a predetermined condition is satisfied, the degree of contribution of the
target value of the behavioral deterioration-suppressing torque to the target value
of the total modification torque is rendered higher than the degree of contribution
of the target value of the steering converging torque to the target value of the
total modification torque.