Abstract: A vehicle steering device includes: steering reaction force generation device having a steering wheel and a steering reaction force motor; steering reaction force motor resolver for detecting steering angle; turning device having a steering motor and capable of turning steered wheels, in a state being mechanically disconnected from the steering reaction force generation device; steering motor resolver for detecting turning angle; drive control section for performing drive control of the steering motor; and vehicle speed sensor for detecting the vehicle speed of vehicle. The drive control section performs drive control of the steering motor if vehicle speed exceeds vehicle speed threshold for the first time after ignition switch is turned on and if specific phase shift based on type and magnitude of phase shift occurs.

Abstract: A vehicle steering device includes: steering reaction force generation device having a steering wheel and a steering reaction force motor; steering reaction force motor resolver for detecting steering angle; turning device having a steering motor and capable of turning steered wheels, in a state being mechanically disconnected from the steering reaction force generation device; steering motor resolver for detecting turning angle; drive control section for performing drive control of the steering motor; and vehicle speed sensor for detecting the vehicle speed of vehicle. The drive control section performs drive control of the steering motor if vehicle speed exceeds vehicle speed threshold for the first time after ignition switch is turned on and if specific phase shift based on type and magnitude of phase shift occurs.

Abstract: The steering device includes first and second motors for steering which have common electric characteristics; first and second current sensors detecting first and second current values in the first and second motor, respectively; and abnormality diagnosis units. The abnormality diagnosis units make an abnormality diagnosis indicating that the steering device is abnormal when difference between the first and second current values exceeds a predetermined threshold value. When some abnormality occurs in the current detecting units for detecting the magnitudes of a current flowing through the steering motor, an abnormality diagnosis is rapidly made by comparing the difference with the predetermined value.

Abstract: The steering device includes first and second motors for steering which have common electric characteristics; first and second current sensors detecting first and second current values in the first and second motor, respectively; and abnormality diagnosis units. The abnormality diagnosis units make an abnormality diagnosis indicating that the steering device is abnormal when difference between the first and second current values exceeds a predetermined threshold value. When some abnormality occurs in the current detecting units for detecting the magnitudes of a current flowing through the steering motor, an abnormality diagnosis is rapidly made by comparing the difference with the predetermined value.

Abstract: A vehicle steering control system for conducting a steering assistance control, in which it is determined whether the vehicle operator has the intention to drive the vehicle by himself. This is done by discriminating the intention using the vehicle lateral deviation, the steering torque and the steering torque change. When it is discriminated that the vehicle operator does not have the intention in two or more discriminations, it is finally determined that the vehicle operator does not have the intention and the vehicle operator is alerted and/or the steering assistance control is discontinued, thereby preventing the vehicle operator from depending on the steer assist torque control excessively.

Abstract: A vehicle steering control system for conducting a steering assistance control in which a basic steering assist torque is determined based on a structural parameter relating to the lane structure such as its curvature. In parallel, corrective steering assist torques are determined based on positional parameters of the vehicle relating to the lane such as a lateral deviation from the lane center line and a vehicle heading angle, and are added to the basic steering assist torque to correct the same. Since the positional parameters are determined based on the image information at or close to the vehicle, this enables to determine the steering assist torque adequately, thereby enhancing the accuracy of the steering assistance control.

Abstract: In a front and rear wheel steering system for steering rear wheels of a vehicle at a certain ratio to front wheels of the vehicle, the rear wheel steering angle is determined according to the steering input and/or the operating conditions of the vehicle, additionally, taking into account the kind of the particular tires that are being used. In particular, it is advantageous to distinguish between normal tires and studless tires as they demonstrate significantly different properties. The kind of tires can be identified either by computing the frictional coefficient of the road surface or by a manual switch. Thus, the handling of the vehicle can be kept unchanged without regard to the kind of the tires that are being used.

Abstract: The road friction is determined from the deviation of the estimated yaw rate under a standard condition from the actually measured yaw rate. The system for determining the road friction includes a parameter identification unit which determines a parameter of a variation term defined in the transfer function of the model for the vehicle response. The variation term may consist of a zero-th order or a first-order transfer function which would not cause any large computation load, and may not depend on the vehicle speed. The determined road friction may be used for controlling the rear wheel steering angle of a four wheel steering vehicle.

Abstract: To the end of ensuring a brisk maneuverability of a front and rear wheel steering vehicle without causing any unstable behavior of the vehicle, the rear wheels are steered in an opposite phase relationship to the front wheels to offset an under-steer tendency of the vehicle when a lateral acceleration acting on the vehicle is between a first prescribed value and a second prescribed value higher than the first prescribed value, and the vehicle would otherwise demonstrate an under-steer tendency, and in a same phase relationship to the front wheels to prevent an excessive slip angle from developing in the rear wheels when the detected lateral acceleration is greater than the second prescribed value, and the slip angle of the rear wheels would otherwise develop an excessive slip angle.

Abstract: In a control system for a front and rear wheel steering vehicle which steers the rear wheels so as to cancel a deviation of an actual yaw rate from a standard yaw rate which can be computed from the steering input, the vehicle speed and other parameters, there is provided a feature to automatically and manually cancel the yaw rate feedback control. If the actual yaw rate continues to exceed a threshold level for more than a certain time period, the yaw rate feedback is canceled gradually so as not to cause any abrupt change in the handling of the vehicle. Alternatively, if the vehicle operator wishes to operate the vehicle under extreme conditions, he may manually cancel the yaw rate feedback control so as to avoid undesirable interference or conflict between the manual steering effort and the yaw rate feedback control action. Thus, the maneuverability of the vehicle under extreme conditions can be improved without losing the benefits of the yaw rate feedback control.

Abstract: A steering angle of rear wheels are steered according to a deviation between an ideal yaw rate response and an actual yaw rate response to the given steering wheel input. By combining feedback control and feed forward control, immunity from external disturbances and lateral stability can be both ensured each at a high level over the entire range of vehicle speed. By appropriately selecting the transfer function of the control system, it is possible to achieve desired responsiveness and stability. Furthermore, the vehicle response in the range where the cornering force of tires tends to saturate can be improved, and it is therefore possible to neutralize the steering property over the entire vehicle speed range.