Vehicle steering system

A vehicle steering system mounted on a vehicle having a plurality of wheels that are steerable, comprising:

• a wheel steering device configured to steer the plurality of wheels independently of each other;
• and
• a controller configured to control the wheel steering device such that a steering amount of each of the plurality of wheels becomes equal to a target steering amount determined for each of the plurality of wheels based on a steering request,
• wherein, in a one-wheel improperly steered state in which one of the plurality of wheels is an improperly steered wheel, the controller determines, as a steering compensation wheel, at least one of the plurality of wheels except the improperly steered wheel, and changes the target steering amount of the steering compensation wheel so as to ensure a total sideways force that corresponds to the steering request, the total sideways force being a total of sideways forces to be generated respectively by the plurality of wheels,
• wherein, in the one-wheel improperly steered state, the controller estimates an improper sideways force, which is the sideways force being generated by the improperly steered wheel, and changes the target steering amount of the steering compensation wheel based on the estimated improper sideways force, and estimates the improper sideways force based on a steering force being applied to the improperly steered wheel.