System and method for operating redundancy braking in case of breakdown of main brake for autonomous vehicle

1. A system for operating redundancy braking in case of a breakdown of a main brake for an autonomous vehicle, the system comprising:

a main brake control unit configured to output a control signal so that a frictional braking force is generated to the main brake of the autonomous vehicle by hydraulic pressure;

a redundancy braking control unit configured to perform communication with the main brake control unit and perform cooperative control between electronic stability control (ESC) and an electronic parking brake (EPB) so that a calculated target braking force is satisfied when it is determined that the main brake control unit has a function failure; and

a sensor unit configured to receive vehicle interior information and vehicle exterior information of the autonomous vehicle and transmit the vehicle interior information and the vehicle exterior information to the redundancy braking control unit,

wherein the redundancy braking control unit controls and replaces rear-wheel ESC braking force with rear-wheel EPB braking force when the rear-wheel ESC braking force satisfies the target braking force,

wherein the redundancy braking control unit includes a breakdown determining unit configured to determine whether the main brake control unit is broken down based on an autonomous driving mode or a driver driving mode,

wherein the redundancy braking control unit is configured to determine whether the main brake control unit is broken down based on wheel hydraulic pressure information received through the sensor unit when the communication between the redundancy braking control unit and the main brake control unit is failed, and

wherein when it is determined that the main brake control unit is broken down in the autonomous driving mode, the redundancy braking control unit is configured to calculate the target braking force based on information collected by the sensor unit and apply the target braking force until the autonomous driving mode is switched to the driver driving mode.

2. The system of claim 1 , wherein when it is determined that the main brake control unit is broken down in the driver driving mode, the redundancy braking control unit calculates the target braking force based on information about a pedal effort applied to a brake pedal.

3. The system of claim 1 , wherein the redundancy braking control unit includes a rear-wheel EPB braking force operating unit configured to simultaneously operate the rear-wheel EPB braking force and the rear-wheel ESC braking force.

4. The system of claim 2 , wherein the redundancy braking control unit includes a rear-wheel ESC braking force releasing unit configured to release the rear-wheel ESC braking force when the rear-wheel EPB braking force satisfies the target braking force.

5. The system of claim 1 , wherein the redundancy braking control unit includes a rear-wheel EPB braking force increasing unit configured to determine whether to add the rear-wheel EPB braking force after the rear-wheel ESC braking force is released, and a front-wheel ESC braking force decreasing unit configured to decrease front-wheel ESC braking force when the rear-wheel EPB braking force is added.

6. A method of operating redundancy braking in case of a breakdown of a main brake for an autonomous vehicle, the method comprising the steps of:

determining whether a main brake control unit and a redundancy braking control unit of the autonomous vehicle communicate with each other;

determining, by the redundancy braking control unit, whether the main brake control unit has a function failure;

calculating, by the redundancy braking control unit, a target braking force when it is determined that the main brake control unit has a function failure; and

performing, by the redundancy braking control unit, cooperative control between electronic stability control (ESC) and an electronic parking brake (EPB) so that the calculated target braking force is satisfied, and performing control to replace rear-wheel ESC braking force with rear-wheel EPB braking force when the rear-wheel ESC braking force satisfies the target braking force,

wherein the step of determining whether the main brake control unit and the redundancy braking control unit communicate with each other includes the step of determining whether the autonomous vehicle is in an autonomous driving mode or a driver driving mode when the main brake control unit and the redundancy braking control unit do not communicate with each other, and

wherein the step of calculating the target braking force when the function failure of the main brake control unit is determined includes the step of calculating the target braking force based on information collected by a sensor unit for a period time for which the autonomous driving mode is switched to the driver driving mode when the autonomous vehicle is in the autonomous driving mode and the main brake control unit is broken down.

7. The method of claim 6 , wherein the step of calculating the target braking force when the function failure of the main brake control unit is determined includes the step of calculating the target braking force based on information about a pedal effort applied to a brake pedal when the autonomous vehicle is in the driver driving mode and the main brake control unit is broken down.

8. The method of claim 6 , wherein the steps of performing cooperative control between the ESC and the EPB, and performing control to replace the real-wheel ESC braking force with the rear-wheel EPB braking force include the step of controlling and simultaneously operating, by the redundancy braking control unit, the rear-wheel EPB braking force and the rear-wheel ESC braking force.

9. The method of claim 6 , wherein the steps of performing cooperative control between the ESC and the EPB, and performing control to replace the real-wheel ESC braking force with the rear-wheel EPB braking force include step of controlling and releasing, by the redundancy braking control unit, the rear-wheel ESC braking force when the rear-wheel EPB braking force satisfies the target braking force.

10. The method of claim 9 , wherein the steps of performing cooperative control between the ESC and the EPB, and performing control to replace the real-wheel ESC braking force with the rear-wheel EPB braking force include steps of determining, by the redundancy braking control unit, whether to add the rear-wheel EPB braking force after the rear-wheel ESC braking force is released, and decreasing, by the redundancy braking control unit, front-wheel ESC braking force when the rear-wheel EPB braking force is added.