Control apparatus and control method for rear wheel steering system

1. A control apparatus for a rear wheel steering system configured to control rear wheels of a vehicle, the control apparatus comprising:

a first sensor and a second sensor spaced apart from each other and mounted on a rear portion of the vehicle;

a determiner configured to determine whether a trailer is mounted at a rear side of the vehicle using at least one of the first sensor or the second sensor;

a calculator configured to calculate a first distance between the first sensor and the trailer in a longitudinal direction of the vehicle and a second distance between the second sensor and the trailer in the longitudinal direction of the vehicle and calculate a target rear wheel steering angle based on difference between the first distance and the second distance; and

a controller configured to control the rear wheel steering system according to the target rear wheel steering angle calculated based on the difference between the first distance and the second distance when it is determined that the trailer is mounted at the rear side of the vehicle.

2. The control apparatus of claim 1 , wherein the calculator is configured to calculate the target rear wheel steering angle such that the difference between the first distance and the second distance is less than or equal to a threshold distance value.

3. The control apparatus of claim 2 , wherein the threshold distance value is determined according to at least one of a vehicle speed, a front wheel steering angle, a front wheel steering angular velocity, a yaw rate, a lateral acceleration, and a control mode of the rear wheel steering system.

4. The control apparatus of claim 1 , wherein the calculator is configured to calculate a width of the trailer, calculate a hitch angle using the calculated first distance, second distance, and width of the trailer, and calculate the target rear wheel steering angle such that the hitch angle becomes zero degrees.

5. The control apparatus of claim 4 , wherein the width of the trailer is calculated when the first distance is equal to the second distance.

6. The control apparatus of claim 1 , wherein the first sensor and the second sensor are included in a parking assist system.

7. The control apparatus of claim 1 , wherein each of the first sensor and the second sensor comprises at least one of an ultrasonic sensor, a laser sensor, lidar sensor and a camera sensor.

8. A control apparatus for a rear wheel steering system configured to control rear wheels of a vehicle, the control apparatus comprising:

a first sensor and a second sensor spaced apart from each other and mounted on a rear portion of the vehicle;

a determiner configured to determine whether a trailer is mounted at a rear side of the vehicle using at least one of the first sensor or the second sensor;

a calculator configured to:

calculate a first distance between the first sensor and the trailer in a longitudinal direction of the vehicle and a second distance between the second sensor and the trailer in the longitudinal direction of the vehicle,

calculate a first distance change rate, which is a change rate of the first distance per unit time,_ or a second distance change rat; which is a change rate of the second distance per unit time, and

calculate the target rear wheel steering angle calculated based on the first distance change rate or the second distance change rate such that the first or second distance change rate is less than or equal to a threshold change rate value; and

a controller configured to control the rear wheel steering system according to the target rear wheel steering angle calculated based on the first or second distance change rate when it is determined that the trailer is mounted at the rear side of the vehicle.

9. The control apparatus of claim 8 , wherein the threshold change rate value is determined according to at least one of a vehicle speed, a front wheel steering angle, a front wheel steering angular velocity, a yaw rate, a lateral acceleration, and a control mode of the rear wheel steering system.

10. A method of controlling a rear wheel steering system configured to control rear wheels of a vehicle comprising first and second sensors which are spaced apart from each other and mounted on a rear portion of the vehicle, the method comprising:

determining whether a trailer is mounted at a rear side of the vehicle using at least one of the first sensor or the second sensor;

calculating a first distance between the first sensor and the trailer in a longitudinal direction of the vehicle and a second distance between the second sensor and the trailer in the longitudinal direction of the vehicle and calculating a target rear wheel steering angle based on difference between the first distance and the second distance; and

controlling the rear wheel steering system according to the target rear wheel steering angle calculated based on the difference between the first distance and the second distance when it is determined that the trailer is mounted at the rear side of the vehicle.

11. The control method of claim 10 , wherein the calculating of the target rear wheel steering angle based on the difference between the first distance and the second distance comprises calculating the target rear wheel steering angle such that the difference between the first distance and the second distance is less than or equal to a threshold distance value.

12. The method of claim 11 , wherein the threshold distance value is determined according to at least one of a vehicle speed, a front wheel steering angle, a front wheel steering angular velocity, a yaw rate, a lateral acceleration, and a control mode of the rear wheel steering system.

13. The method of claim 11 , wherein the determining of whether the trailer is mounted and the calculating of the first distance and the second distance are performed in a parking assist system.

14. The method of claim 13 , wherein the calculating of the first distance change rate or the second distance change rate is performed in the parking assist system or in the rear wheel steering system.

15. The control method of claim 10 , further comprising:

calculating a first distance change rate, which is a change rate of the first distance per unit time, or a second distance change rate, which is a change rate of the second distance per unit time; and

calculating the target rear wheel steering angle such that the first or second distance change rate is less than or equal to a threshold change rate value.

16. The method of claim 15 , wherein the threshold change rate value is determined according to at least one of a vehicle speed, a front wheel steering angle, a front wheel steering angular velocity, a yaw rate, a lateral acceleration, and a control mode of the rear wheel steering system.

17. The method of claim 10 , further comprising:

calculating a width of the trailer;

calculating a hitch angle using the calculated first distance, second distance, and width of the trailer; and

calculating the target rear wheel steering angle such that the hitch angle becomes zero degrees.

18. The method of claim 17 , wherein the calculating of the width of the trailer is performed when the first distance is equal to the second distance.