Electronic parking brake system and control method thereof

1. An electronic parking brake system comprising:

a pair of brake pads arranged on opposite sides of a brake disc;

a piston configured to press at least one of the brake pads;

a nut member configured to press the piston;

a spindle member configured to move the nut member;

an electric motor configured to rotate the spindle member; and

a controller configured to move the nut member from a parking operation position in which the brake pads are pressed by a forward movement of the nut member to a parking complete release position in which the pressing on the brake pad is completely released by the a backward movement of the nut member, and estimate a wear amount of the brake pads by comparing the movement distance of the nut member from the parking operation position to the parking complete release position with a preset distance.

2. The electronic parking brake system of claim 1 ,

wherein the parking complete release position is a position in which the nut member moved backward is in close contact with the spindle member.

3. The electronic parking brake system of claim 1 , further comprising:

a current sensor configured to detect a current flowing through the electric motor;

wherein the controller detects the current flowing through the electric motor while moving the nut member in a reverse direction, and when a current value detected is greater than a preset value, the controller determines that the nut member has reached the parking complete release position.

4. The electronic parking brake system of claim 1 , further comprising:

a current sensor configured to detect a current flowing through the electric motor; and

a voltage sensor configured to detect a voltage input to the electric motor;

wherein the controller determines a movement speed of the nut member based on the current and the voltage of the electric motor, and determines the movement distance of the nut member based on the determined movement speed and a movement time while the nut member reaches the parking complete release position from the parking operation position.

5. The electronic parking brake system of claim 1 , further comprising:

a rotary sensor configured to detect a motor speed;

wherein, the controller detects the motor speed while the nut member reaches the parking complete release position from the parking operation position, and determines the movement distance of the nut member according to the detected motor speed.

6. The electronic parking brake system of claim 1 ,

wherein the controller, when a vehicle is in a start-off state and a traveling distance of the vehicle is greater than a preset traveling distance, estimates the wear amount of the brake pad based on a change in the movement distance of the nut member.

7. An electronic parking brake system, comprising:

a pair of brake pads arranged on opposite sides of a brake disc;

a piston configured to press at least one of the brake pads;

a nut member configured to press the piston;

a spindle member configured to move the nut member;

an electric motor configured to rotate the spindle member;

a current sensor configured to detect a current flowing through the electric motor;

a voltage sensor configured to detect a voltage input to the electric motor; and

a controller configured to:

drive the electric motor to move the nut member from a parking operation position to a parking complete release position when a vehicle is in a start-off state;

determine a movement speed of the nut member based on the current and the voltage of the electric motor;

determine a movement distance of the nut member based on the determined movement speed and a movement time of the nut member while the vehicle reaches the parking complete release position from the parking operation position; and

estimate a wear amount of the brake pads by comparing the determined movement distance with a preset distance.

8. The electronic parking brake system of claim 7 ,

wherein the parking operation position is a position of the nut member when the brake pad is pressed by a forward movement of the nut member, and

the parking complete release position is a position of the nut member when the pressing on the brake pad is fully released by a backward movement of the nut member.

9. The electronic parking brake system of claim 8 ,

wherein the parking complete release position is a position in which the nut member moved backward is in close contact with the spindle member.

10. The electronic parking brake system of claim 8 ,

wherein the controller detects current value of the electric motor when the nut member moves forward, and determines whether a current position of the nut member is the parking operation position based on the detected current value, and

the controller detects the current value of the electric motor when the nut member moves backward, and determines whether the current position of the nut member is the parking complete release position based on the detected current value.

11. A control method of the electronic parking brake system of claim 7 , comprising:

driving the electric motor to move the nut member from the parking operation position to the complete parking release position when the vehicle is in the start-off state;

determining the movement speed of the nut member based on the current and the voltage of the electric motor;

determining the movement distance of the nut member based on the determined movement speed and the movement time of the nut member while the nut member reaches the parking complete release position from the parking operation position; and

estimating the wear amount of the brake pads by comparing the determined movement distance with the preset distance.

12. The method of claim 11 ,

in the nut member movement,

wherein the parking operation position is a position of the nut member when the brake pad is pressed by a forward movement of the nut member, and

the parking complete release position is a position of the nut member when the pressing on the brake pad is fully released by a backward movement of the nut member.

13. The method of claim 12 ,

in the nut member movement,

wherein the parking complete release position is a position in which the nut member moved backward is in close contact with the spindle member.

14. The method of claim 11 , further comprising:

in the nut member movement,

when the nut member moves forward, detecting a current value of the electric motor and determining whether a current position of the nut member is the parking operation position based on the detected current value,

when the nut member moves backward, detecting the current value of the electric motor and determining whether the current position of the nut member is the parking complete release position based on the detected current value.