Method for controlling ESC integrated braking system

1. A method for controlling an ESC integrated braking system, the method comprising:

checking, by a control unit, whether a brake is in an on state or a standby state as the braking system is activated;

checking, by the control unit, whether a current temperature value is in a low temperature state lower than specified reference temperature value; and

controlling, by the control unit, a current duty for driving a hydraulic control valve and a current component of a motor for driving a master cylinder according to the state of the brake and whether the current temperature value is in the low temperature state,

wherein, when the brake is in the on state and the current temperature value is in the low temperature state, the control unit performs maximum duty control for maintaining the operation state of the at least one constantly-operated hydraulic control valve specified in advance.

2. The method according to claim 1 , wherein, when the brake is in the standby state and the current temperature value is not in the low temperature state, the control unit performs minimum duty control for maintaining the operation state of the at least one constantly-operated hydraulic control valve specified in advance.

3. The method according to claim 2 , wherein the at least one constantly-operated hydraulic control valve is a hydraulic control valve specified in order to form pressure and pedal feel during a brake operation.

4. The method according to claim 1 , wherein, when the brake is in the standby state and the current temperature value is in the low temperature state, the control unit:

applies a magnetic flux contributing component current i d , which is a remaining current obtained by excluding a minimum torque contributing component current i q from a maximum current i s capable of constantly operating the motor, to the motor as a current for preventing a piston of a master cylinder from moving forward; and

drives all hydraulic control valves and inlet valves of the ESC integrated braking system while performing maximum duty control capable of constantly operating the valves.

5. The method according to claim 4 , wherein the magnetic flux contributing component current i d applied to the motor is a root (SQRT) value (i d =√{square root over (i s 2 −)}i q 2 ) of a value obtained by subtracting a square value i q 2 of the torque contributing component current i q from a square value i s 2 of the maximum current i s capable of constantly operating the motor for driving the master cylinder.

6. The method according to claim 1 , further comprising:

when the brake is in the on state, calculating, by the control unit, a required pressure corresponding to a displacement detected by a pedal stroke sensor, in order to adjust a current component of the motor for driving the master cylinder according to the displacement of a pedal.

7. The method according to claim 1 , further comprising, in order to check whether the current temperature value is in the low temperature state in the brake-on state:

checking, by the control unit, whether a difference between estimated master cylinder pressure Pme and master cylinder pressure Pm at a room temperature value is greater than a specified reference value; and

determining, by the control unit, that the current temperature value is in the low temperature state when the difference between the estimated master cylinder pressure Pme and the master cylinder pressure Pm at the room temperature value is greater than the specified reference value.

8. The method according to claim 7 , wherein the estimated master cylinder pressure Pme is calculated using Equation 1 below,

Pme=Pw+k*V+k 1* V 2   Equation 1

where Pme denotes the estimated master cylinder pressure, Pw denotes wheel pressure, V denotes a piston speed, and k/k1 denotes a constant associated with temperature characteristics of a valve orifice and a brake fluid.

9. The method according to claim 1 , wherein, when the brake is in the on state and the current temperature value is not in the low temperature state, the control unit:

controls the magnetic flux contributing component current i d during vector control of the motor for driving the master cylinder to be 0 (i d =0); and

performs minimum duty control for maintaining the operation state of the at least one constantly-operated hydraulic control valve specified in advance.

10. The method according to claim 1 , wherein, in a case where the brake is in the on state and the current temperature value is in the low temperature state, when the torque contributing component current i q for vector control of the motor is greater than the maximum current i s capable of constantly operating the motor, the control unit controls the magnetic flux contributing component current i d during the vector control of the motor for driving the master cylinder to be 0 (i d =0); and

performs minimum duty control for maintaining the operation state of the at least one constantly-operated hydraulic control valve specified in advance.

11. The method according to claim 10 , wherein, in the case where the brake is in the on state and the current temperature value is in the low temperature state, when the torque contributing component current i q is less than the maximum current i s capable of constantly operating the motor for driving the master cylinder,

the control unit applies the root (SQRT) value (i d =√{square root over (i s 2 −)}i q 2 ) of the value, which is obtained by subtracting the square value i q 2 of the torque contributing component current i q from the square value i s 2 of the maximum current i s capable of constantly operating the motor for driving the master cylinder, to the motor as a component current.