Apparatus, method and computer readable medium for calculating target steering angle considering yaw moment by torque vectoring when turning driving of electric vehicle in autonomous driving

1. An apparatus of determining a target steering angle, the apparatus comprising:

one or more processors, and

a storage medium storing computer-readable instructions that, when executed by the one or more processors, cause the one or more processors to:

determine a feed forward steering angle reflecting a yaw moment generated by torque vectoring during turning driving of an electric vehicle in autonomous driving; and

obtain the target steering angle by adding the determined feedforward steering angle to a feedback steering angle, the feedback steering angle being a steering angle measured through a steering angle sensor; and

controlling the autonomous driving of the electric vehicle based on the target steering angle.

2. The apparatus of claim 1 , wherein the one or more processors is configured to:

obtain the yaw moment generated by the torque vectoring during the turning driving of the electric vehicle,

obtain lateral force of a tire of each of a front wheel and a rear wheel of the electric vehicle by reflecting the obtained yaw moment,

obtain a tire slip angle of each of the front wheel and the rear wheel based on the obtained lateral force of the tire of each of the front wheel and the rear wheel, and

obtain the feedforward steering angle based on the obtained tire slip angle of each of the front wheel and the rear wheel.

3. The apparatus of claim 2 , wherein the yaw moment is expressed by the following equation:

M zTV ={(T FR +T RR −(T FL +T RL )} w/r

where, M Z,TV is a yaw moment, T FR is a torque applied to a motor on a right side of the front wheel by the torque vectoring, T RR is a torque applied to a motor on a right side of the rear wheel by the torque vectoring, T FL is a torque applied to a motor on a left side of the front wheel by the torque vectoring, T RL is a torque applied to a motor on a right side of the rear wheel by the torque vectoring, w is a lateral distance from center of gravity (CG) to the wheel, and r is a dynamic radius of the tire.

4. The apparatus of claim 2 , wherein the lateral force of the tire is expressed by the following equation:

F

y

,

F

=

ma

y

⁢

I

R

l

-

M

Z

,

TV

l

F

y

,

R

=

ma

y

⁢

I

F

l

-

M

Z

,

TV

l

where, F y,F is lateral force of the tire of the front wheel, F y,R is lateral force of the tire of the rear wheel, m is mass of the electric vehicle, a y is lateral acceleration, I R is a length from center of gravity of the electric vehicle to the rear wheel, l is an inter-axle distance, M Z,TV is a yaw moment, and when is a length from the center of gravity of the electric vehicle to the front wheel.

5. The apparatus of claim 2 , wherein the tire slip angle is expressed by the following equation:

α

F

=

F

y

,

F

C

a

,

F

α

R

=

F

y

,

R

C

a

,

R

where, α F is the tire slip angle of the front wheel, F y,F is lateral force of the tire of the front wheel, C α,F is tire stiffness of the front wheel, α R is a tire slip angle of the rear wheel, F y,R is lateral force of the tire of the rear wheel, and C α,R is tire stiffness of the rear wheel.

6. The apparatus of claim 2 , wherein the feedforward steering angle is expressed by the following equation:

δ FF =lκ ref −(α F −α R )

where, δ FF is a feedforward steering angle, l is a length between the front wheel and the rear wheel, kref is 1/(R*cos β), where, R is a turning radius, β is a lateral slip angle at center of gravity, α F is a tire slip angle of the front wheel, and α R is a tire slip angle of the rear wheel.

7. A method for determining a target steering angle, which is performed on a computing device comprising one or more processors and a storage medium storing computer-readable instructions that can be executed by the one or more processors, the method comprising:

determining, by the one or more processors, a feedforward steering angle by reflecting a yaw moment generated by torque vectoring during turning driving of an electric vehicle in autonomous driving;

obtaining, by the one or more processors, a target steering angle by adding the determined feedforward steering angle to a feedback steering angle, the feedback steering angle being a steering angle measured through a steering angle sensor; and

controlling the autonomous driving of the electric vehicle based on the target steering angle.

8. The method of claim 7 , wherein the determining a feedforward steering angle includes:

obtaining the yaw moment generated by the torque vectoring during turning driving of the electric vehicle;

obtaining lateral force of a tire each of a front wheel and a rear wheel by reflecting the obtained yaw moment;

obtaining a tire slip angle each of the front wheel and the rear wheel based on the obtained lateral force of the tire of each of the front wheel and the rear wheel; and

obtaining the feedforward steering angle based on the obtained tire slip angle of each of the front wheel and the rear wheel.

9. The method of claim 8 , wherein the yaw moment is expressed by the following equation:

M zTV ={(T FR +T RR −(T FL +F RL )} w/r

where, M Z,TV is a yaw moment, T FR is a torque applied to a motor on a right side of the front wheel by the torque vectoring, T RR is a torque applied to a motor on a right side of the rear wheel by the torque vectoring, T FL is a torque applied to a motor on a left side of the front wheel by the torque vectoring, T RL is a torque applied to a motor on a right side of the rear wheel by the torque vectoring, w is a lateral distance from center of gravity (CG) to the wheel, and r is a dynamic radius of the tire.

10. The method of claim 8 , wherein the lateral force of the tire is expressed by the following equation:

F

y

,

F

=

ma

y

⁢

I

R

l

-

M

Z

,

TV

l

F

y

,

R

=

ma

y

⁢

I

F

l

-

M

Z

,

TV

l

where F y,F is lateral force of a tire of the front wheel, F y,R is lateral force of a tire of the rear wheel, m is mass of the electric vehicle, a y is lateral acceleration, I R is a length from center of gravity of the electric vehicle to the rear wheel, l is an inter-axle distance, M Z,TV is a yaw moment, and I F is a length from the center of gravity of the electric vehicle to the front wheel.

11. The method of claim 8 , wherein the tire slip angle is expressed by the following equation:

α

F

=

F

y

,

F

C

a

,

F

α

R

=

F

y

,

R

C

a

,

R

where, α F is a tire slip angle of the front wheel, F y,F is lateral force of a tire of the front wheel, C α,F is tire stiffness of the front wheel, α F is a tire slip angle of the rear wheel, F y,R is lateral force of a tire of the rear wheel, and C α,R is tire stiffness of the rear wheel.

12. The method of claim 8 , wherein the feedforward steering angle is expressed by the following equation:

δ FF =lκ ref −(α F −α R )

where, δ FF is a feedforward steering angle, l is a length between a front wheel and a rear wheel, kref is 1/(R*cos β), where, R is a turning radius, β is a lateral slip angle at center of gravity, α F is a tire slip angle of the front wheel, and α R is a tire slip angle of the rear wheel.

13. A non-transitory computer-readable storage medium storing computer-readable instructions which causes a computing device to:

determine, a feedforward steering angle by reflecting a yaw moment generated by torque vectoring during turning driving of an electric vehicle in autonomous driving; and

obtain, a target steering angle by adding the determined feedforward steering angle to a feedback steering angle, the feedback steering angle being a steering angle measured through a steering angle sensor; and

control the autonomous driving of the electric vehicle based on the target steering angle.