Driving assist device, driving assist method, and driving assist system

Abstract

The invention ensures a proper vehicle attitude even if a friction coefficient of a contacted road surface with respect to wheels is small. A driving assist device obtains a first moment that is a moment necessary for an subject vehicle to follow a running course, on the basis of information about a running coursed of an subject vehicle, which is obtained on the basis of external environment information of the subject vehicle, which is acquired by an external environment recognition portion, a first physical quantity associated with a motion state of the subject vehicle, which is inputted by a vehicle motion state detection sensor, and specifications of the subject vehicle, further obtains a second moment that is a moment that can be generated in the subject vehicle on the basis of a friction coefficient of a contacted road surface with respect to the wheels of the subject vehicle, which is acquired by a road surface condition acquisition portion, and a second physical quantity associated with a motion state of the subject vehicle, which is inputted by the vehicle motion state detection sensor, and outputs to a braking control device a command to implement control for making a braking force generated in rear wheels of the wheels greater than a braking force generated in front wheels when the second moment is smaller than the first moment.