| 摘要 |
In accordance with a steering apparatus ( 20 ), a grip state between a ground surface on which a steered wheel is grounded and the steered wheel is estimated by a grip degree estimation arithmetically operating process ( 30 a) which is arithmetically operated by AFS_ECU ( 30 ), and VGRS target angle is set such that a steering gear ratio is increased in the case that the grip degree gets close to a grip limit on the basis of an estimated grip state, in accordance with a grip degree vs gear ratio map ( 30 b). Accordingly, since it is possible to estimate the grip degree which is changed in correspondence to a magnitude of the road surface it, for example, in the case that the steered wheel gets close to the grip limit, it is possible to increase the steering gear ratio so as to set large even at a time when the vehicle runs at the low speed. Therefore, since it is possible to prevent a phenomenon that the steered wheel is largely controlled by a smaller steering angle from being generated in the case that the vehicle runs on the road surface having the low mu, there is obtained an effect that a stability in the vehicle motion can be improved.
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