Controlling engine idle sailing in a vehicle using relative vehicle speed

1. A method comprising:

detecting, by an electronic control unit (ECU) of a host vehicle, a distance between the host vehicle and a preceding vehicle and a current speed of the preceding vehicle;

calculating, by the ECU, a relative speed of the host vehicle with respect to the preceding vehicle based on a current speed of the host vehicle and the detected current speed of the preceding vehicle;

determining, by the ECU, whether to activate an engine idle sailing (EIS) function of the host vehicle, in which a driving gear of the host vehicle shifts to neutral, based on the relative speed of the host vehicle with respect to the preceding vehicle and the detected distance between the host vehicle and the preceding vehicle; and

in response to determining to activate the EIS function of the host vehicle, controlling, by the ECU, operation of the host vehicle so as to activate the EIS function of the host vehicle, causing the driving gear of the host vehicle to shift to neutral,

wherein the determining of whether to activate the EIS function of the host vehicle, in which the driving gear of the host vehicle shifts to neutral, comprises:

determining, by the ECU, whether to activate the EIS function of the host vehicle, in which the driving gear of the host vehicle shifts to neutral, based further on whether an accelerator pedal and a brake pedal of the host vehicle are depressed and whether the current speed of the host vehicle exceeds a predetermined EIS activation speed.

2. The method of claim 1 , further comprising:

determining, by the ECU, whether the distance between the host vehicle and the preceding vehicle exceeds a distance threshold; and

in response to determining that the distance between the host vehicle and the preceding vehicle exceeds the distance threshold, controlling, by the ECU, operation of the host vehicle so as to activate the EIS function of the host vehicle, causing the driving gear of the host vehicle to shift to neutral.

3. The method of claim 2 , wherein the distance threshold is calculated based on the relative speed of the host vehicle with respect to the preceding vehicle.

4. The method of claim 3 , further comprising:

comparing, by the ECU, the relative speed of the host vehicle with respect to the preceding vehicle with one or more predetermined relative speed thresholds; and

calculating, by the ECU, the distance threshold based on the comparison of the relative speed of the host vehicle with respect to the preceding vehicle with the one or more predetermined relative speed thresholds.

5. The method of claim 4 , wherein the one or more predetermined relative speed thresholds includes an upper relative speed threshold and a lower relative speed threshold.

6. The method of claim 5 , wherein the comparing of the relative speed of the host vehicle with respect to the preceding vehicle with one or more predetermined relative speed thresholds comprises:

comparing, by the ECU, the relative speed of the host vehicle with respect to the preceding vehicle with the lower relative speed threshold; and

when the relative speed of the host vehicle with respect to the preceding vehicle is greater than or equal to the lower relative speed threshold, comparing, by the ECU, the relative speed of the host vehicle with respect to the preceding vehicle with the upper relative speed threshold.

7. The method of claim 6 , further comprising:

when the relative speed of the host vehicle with respect to the preceding vehicle is less than the lower relative speed threshold, calculating, by the ECU, the distance threshold so as to correspond to a first distance threshold;

when the relative speed of the host vehicle with respect to the preceding vehicle is greater than the upper relative speed threshold, calculating, by the ECU, the distance threshold so as to correspond to a second distance threshold which is less than the first distance threshold; and

when the relative speed of the host vehicle with respect to the preceding vehicle is less than the upper relative speed threshold and greater than the lower relative speed threshold, calculating, by the ECU, the distance threshold so as to correspond to a third distance threshold which is less than the first distance threshold and greater than the second distance threshold.

8. The method of claim 3 , further comprising:

calculating, by the ECU, the distance threshold based on the relative speed of the host vehicle with respect to the preceding vehicle and a current traffic condition.

9. The method of claim 3 , further comprising:

determining, by the ECU, the distance threshold based on the relative speed of the host vehicle with respect to the preceding vehicle using a look-up table.

10. The method of claim 2 , further comprising:

in response to determining that the distance between the host vehicle and the preceding vehicle does not exceed the distance threshold, controlling, by the ECU, operation of the host vehicle so as to cause the driving gear of the host vehicle to shift to drive.

11. The method of claim 1 , wherein detecting of the distance between the host vehicle and the preceding vehicle and the current speed of the preceding vehicle comprises:

sensing, by an advanced driver-assistance system (ADAS) equipped in the host vehicle, measurements indicating the distance between the host vehicle and the preceding vehicle and the current speed of the preceding vehicle; and

detecting, by the ECU, the distance between the host vehicle and the preceding vehicle and the current speed of the preceding vehicle using the measurements sensed by the ADAS.

12. The method of claim 11 , further comprising:

receiving, by the ECU, acceleration signals generated by the host vehicle; and

compensating, by the ECU, the measurements sensed by the ADAS using the acceleration signals generated by the host vehicle.

13. A system comprising:

an advanced driver-assistance system (ADAS) equipped in a host vehicle, the ADAS configured to detect a distance between the host vehicle and a preceding vehicle and a current speed of the preceding vehicle; and

one or more electronic control units (ECUs) of the host vehicle including a memory storing program instructions and a processor configured to execute the stored program instructions, which when executed cause the one or more ECUs to:

calculate a relative speed of the host vehicle with respect to the preceding vehicle based on a current speed of the host vehicle and the detected current speed of the preceding vehicle;

determine whether to activate an engine idle sailing (EIS) function of the host vehicle, in which a driving gear of the host vehicle shifts to neutral, based on the relative speed of the host vehicle with respect to the preceding vehicle and the distance between the host vehicle and the preceding vehicle; and

in response to determining to activate the EIS function of the host vehicle, control operation of the host vehicle so as to activate the EIS function of the host vehicle, causing the driving gear of the host vehicle to shift to neutral,

wherein the stored program instructions, which when executed cause the one or more ECUs to determine whether to activate the EIS function of the host vehicle, in which the driving gear of the host vehicle shifts to neutral, further cause the one or more ECUs to:

determine whether to activate the EIS function of the host vehicle, in which the driving gear of the host vehicle shifts to neutral, based further on whether an accelerator pedal and a brake pedal of the host vehicle are depressed and whether the current speed of the host vehicle exceeds a predetermined EIS activation speed.

14. A non-transitory computer readable medium containing program instructions, which when executed by one or more electronic control units (ECUs) of a host vehicle cause the one or more ECUs to:

detect a distance between the host vehicle and a preceding vehicle and a current speed of the preceding vehicle;

calculate a relative speed of the host vehicle with respect to the preceding vehicle based on a current speed of the host vehicle and the current speed of the preceding vehicle;

determine whether to activate an engine idle sailing (EIS) function of the host vehicle, in which a driving gear of the host vehicle shifts to neutral, based on the relative speed of the host vehicle with respect to the preceding vehicle and the distance between the host vehicle and the preceding vehicle; and

in response to determining to activate the EIS function of the host vehicle, control operation of the host vehicle so as to activate the EIS function of the host vehicle, causing the driving gear of the host vehicle to shift to neutral,

wherein the program instructions, which when executed cause the one or more ECUs to determine whether to activate the EIS function of the host vehicle, in which the driving gear of the host vehicle shifts to neutral further cause the one or more ECUs to:

determine whether to activate the EIS function of the host vehicle, in which the driving gear of the host vehicle shifts to neutral, based further on whether an accelerator pedal and a brake pedal of the host vehicle are depressed and whether the current speed of the host vehicle exceeds a predetermined EIS activation speed.