Regenerative brake method of vehicle

1. A regenerative brake method of a vehicle, the method comprising:

selecting and inputting one of a plurality of regenerative brake modes by a driver and recognizing the regenerative brake mode selected by the driver, by a controller;

determining an on/off-state of an active shift control (ASC) function by the controller when the regenerative brake mode selected by the driver is an efficiency-preferred mode or an intermediate mode;

controlling a motor speed during regenerative brake and simultaneously performing ASC control for changing a gear stage, by the controller when the ASC function is in the on-state; and

controlling gear shift for changing the gear stage without control of the motor speed during regenerative brake, by the controller when the ASC function is in the off-state.

2. The method of claim 1 , wherein, when a battery state of charge (SOC) state is a high SOC state with a predetermined setting level or greater, the controller controls regenerative brake of a drivability-preferred mode for gear shift using a drivability-preferred gear shift map during regenerative brake.

3. The method of claim 1 , wherein, when a battery state of charge (SOC) state is not a high SOC state with a predetermined setting level or greater, the selecting and inputting, the determining, the controlling the motor speed, and the controlling the gear shift are performed.

4. The method of claim 1 , wherein, when the regenerative brake mode selected by the driver is not an efficiency-preferred mode and an intermediate mode, if a battery state of charge (SOC) state is a low SOC state with a predetermined setting level or less, the controller determines the on/off-state of the ASC function and then performs the controlling the motor or the controlling the gear shift.

5. The method of claim 1 , wherein the determining the on/off-state includes:

when the regenerative brake mode selected by a user is the efficiency-preferred mode or the intermediate mode, if a current state is a regenerative brake on-state satisfying a regenerative brake condition, calculating each of regenerative power when a gear stage is changed and regenerative power when a current gear stage is maintained, by the controller; and

when the regenerative power when the gear stage is changed is larger than the regenerative power when the current gear stage is maintained, determining the on/off-state of the ASC function, by the controller.

6. The method of claim 5 , wherein the determining includes:

when the regenerative power when the gear stage is changed is larger than the regenerative power when the current gear stage is maintained, determining whether a predetermined constraint condition is satisfied, by the controller; and

when the predetermined constraint condition is satisfied, determining the on/off-state of the ASC function, by the controller.

7. The method of claim 6 , wherein, when the regenerative power when the gear stage is changed is equal to or less than the regenerative power when the current gear stage is maintained, or the constraint condition determined when the gear stage is changed not satisfied, the controller controls regenerative brake of a drivability-preferred mode in which gear shift is performed using a drivability-preferred gear shift map during regenerative brake.

8. The method of claim 6 , wherein the constraint condition includes a condition in which a motor speed and motor torque are present in an allowable range after gear shift.

9. The method of claim 6 , wherein the constraint condition includes a condition in which an elapsed time after immediately previous gear shift is within a setting time when the same gear stage number as the immediately previous gear shift is returned.

10. The method of claim 1 , wherein the controlling the motor speed includes:

when the ASC function is in the on-state, predicting a regenerative energy amount in a case of ASC and a regenerative energy amount when a current gear stage is maintained, by the controller; and

comparing the regenerative energy amount in the case of ASC with the regenerative energy amount when the current gear stage is maintained, and when the regenerative energy amount in the case of ASC is larger than the regenerative energy amount when the current gear stage is maintained, controlling the motor speed during regenerative brake and simultaneously performing ASC control for changing a gear stage.

11. The method of claim 10 , wherein, when the regenerative energy amount in the case of ASC is equal to or less than the regenerative energy amount when the current gear stage is maintained, the controller controls regenerative brake of a drivability-preferred mode for gear shift using a drivability-preferred gear shift map during regenerative brake.

12. The method of claim 1 , wherein the controlling the gear shift includes controlling regenerative brake of an efficiency-preferred mode or intermediate mode for gear shift using an efficiency-preferred gear shift map or an intermediate mode gear shift map during regenerative brake, by the controller when the ASC function is in the off-state.

13. The method of claim 1 , wherein the controlling the motor speed includes:

when the ASC function is in the on-state, predicting a regenerative energy amount in a case of ASC and a regenerative energy amount when a current gear stage is maintained, by the controller; and

comparing the regenerative energy amount in the case of ASC with the regenerative energy amount when the current gear stage is maintained, and when the regenerative energy amount in the case of ASC is larger than the regenerative energy amount when the current gear stage is maintained, performing ASC control using an efficiency-preferred gear shift map or an intermediate mode gear shift map during regenerative brake.

14. The method of claim 1 , wherein the controlling the motor speed includes:

when the ASC function is in the on-state, performing ASC control using an efficiency-preferred gear shift map for ASC or an intermediate mode gear shift map for ASC during regenerative brake, by the controller.