Vehicle turning control apparatus

1. A vehicle turning control device controlling a turning characteristic of a vehicle having braking/driving sources capable of independently controlling a braking/driving torque which is a braking torque or a driving torque for each of wheels, the vehicle turning control device comprising:

a yaw moment control device configured to control a yaw moment that occurs in the vehicle; and

a slip determination device configured to determine a road surface state from an angular velocity and an angular acceleration of the wheel of the vehicle and a vehicle speed,

wherein

the yaw moment control device includes

a control gain calculator configured to calculate a control gain,

a target yaw rate calculator configured to calculate a target yaw rate from the vehicle speed, a steering angle thereof, and the control gain calculated by the control gain calculator, and

a yaw moment calculator configured to calculate the braking/driving torque for each wheel of the vehicle in accordance with the target yaw rate calculated by the target yaw rate calculator, and

the control gain calculator calculates the control gain in accordance with a predetermined condition on the basis of a determination result of the slip determination device.

2. The vehicle turning control device as claimed in claim 1 , wherein

the yaw moment control device includes a road surface frictional coefficient estimator configured to estimate a road surface frictional coefficient, and

when the determination result of the slip determination device satisfies a predetermined first condition, the control gain calculator calculates the control gain using the road surface frictional coefficient estimated by the road surface frictional coefficient estimator, and when the determination result of the slip determination device satisfies a predetermined second condition different from the first condition, the control gain calculator returns the control gain from a control gain which determines an initial yaw response characteristic to a control gain corresponding to an original yaw response characteristic of the vehicle.

3. The vehicle turning control device as claimed in claim 2 , wherein

the slip determination device calculates a slip rate of the wheel from the angular velocity of the wheel and the vehicle speed, and determines the road surface state in accordance with the angular acceleration and the slip rate of the wheel,

the first condition is that an absolute value of the slip rate is equal to or greater than a first threshold value and an absolute value of the angular acceleration is smaller than a second threshold value, and

the second condition is that the absolute value of the slip rate is equal to or greater than the first threshold value and the absolute value of the angular acceleration is equal to or greater than the second threshold value.

4. The vehicle turning control device as claimed in claim 3 , wherein

the road surface frictional coefficient estimator estimates the road surface frictional coefficient in accordance with the slip rate calculated by the slip determination device, a deviation between an actual lateral acceleration detected by a lateral acceleration detector provided to the vehicle and a target lateral acceleration, and a deviation between an actual yaw rate detected by a yaw rate detector provided to the vehicle and the target yaw rate.

5. A vehicle turning control device for controlling a turning characteristic of a vehicle having braking/driving sources capable of independently controlling a braking/driving torque which is a braking torque or a driving torque for each of wheels, the vehicle turning control device comprising:

a memory configured to store instructions; and

a processor configured to execute each of the instructions to:

control a yaw moment that occurs in the vehicle,

determine a road surface state from an angular velocity and an angular acceleration of the wheel of the vehicle and a vehicle speed,

calculate a control gain,

calculate a target yaw rate from the vehicle speed, a steering angle thereof, and the control gain,

calculate the braking/driving torque for each wheel of the vehicle in accordance with the target yaw rate, and

calculate the control gain in accordance with a predetermined condition on the basis of a determination result of the road surface state.