KR100437208B1 - method for cruise control - Google Patents

Abstract

The present invention relates to a cruise control method of a vehicle in which the target vehicle distance (safety distance) between the own vehicle and the preceding vehicle can be variably controlled in consideration of the driving characteristics of the preceding vehicle. Calculate the deceleration by differentiating the vehicle speed of the preceding vehicle, and if the calculated deceleration is greater than the standard deceleration to classify it into the caution class, classify the preceding vehicle into the caution class, and classify the preceding vehicle into the caution class. In this case, by using the deceleration of the preceding vehicle, the preliminary inter-vehicle distance is calculated and included in the target inter-vehicle distance so that the inter-vehicle distance can be widened than usual. And smooth traffic flow by maintaining a narrower distance between vehicles when the preceding vehicle is relatively stable. This has the effect of to.

Description

Cruise control method of vehicle {method for cruise control}

The present invention relates to a cruise control method of a vehicle, and more particularly, to a cruise control of a vehicle to variably control a target distance (safety distance) between a host vehicle and a preceding vehicle in consideration of driving characteristics of the preceding vehicle. It relates to a control method.

In general, drivers traveling long distances have had to continue to press the accelerator pedal. Therefore, in order to alleviate this inconvenience, a cruise device has been developed to automatically maintain the speed and the distance between vehicles. That is, if there is no preceding vehicle ahead, the vehicle travels at a constant speed (constant speed driving mode) at the driver's driving speed.If there is a preceding vehicle ahead, the regular interval driving is maintained while maintaining a safe distance from the preceding vehicle. Was done.

1 illustrates such a cruise control method of a conventional vehicle, and when the preceding vehicle is present and the own vehicle is running, the traveling speed (vehicle speed) of the own vehicle is detected through the vehicle speed sensor (S1).

When the traveling speed (vehicle speed) of the own vehicle is detected in the detecting step S1, a target distance (safety distance) between the own vehicle and the front vehicle is calculated to prevent a collision accident caused by sudden braking of the preceding vehicle (S2). Here, the target distance is determined by equation (1).

(Equation 1) Target Distance = Headway Time * Driving Speed + Spare Distance

(Headway Time: the time from depressing the brake pedal to the braking state, preliminary clearance: any braking distance to improve safety)

When the target inter-vehicle distance is calculated in the calculation step S2, the inter-vehicle distance between the host vehicle and the preceding vehicle is measured by using the inter-vehicle distance detection sensor, for example, a laser radar (S3).

When the distance between the host vehicle and the preceding vehicle is measured in step S3, the distance between the vehicle and the target vehicle is compared (S4).

If the inter-vehicle distance is greater than the target inter-vehicle distance in the determination step S4, the microcomputer (not shown) issues an acceleration command to control the throttle valve (S5). As a result, the traveling vehicle speed of the host vehicle is accelerated to narrow the inter-vehicle distance.

On the contrary, when the inter-vehicle distance is smaller than the target inter-vehicle distance in the determination step S4, the microcomputer issues a deceleration command to control the brake (S6). As a result, the traveling vehicle speed of the host vehicle is decelerated, and the inter-vehicle distance is widened. In addition, if the distance between vehicles is reduced to a dangerous level, an alarm operation is performed.

However, in the conventional cruise control method, the target vehicle distance between the own vehicle and the front vehicle is determined according to how the driver sets the spare vehicle distance. Therefore, when the preliminary inter-vehicle distance is set to a large value, the inter-vehicle distance between the own vehicle and the front vehicle is kept wider than necessary, which hinders the smooth traffic flow. Since it is kept narrow, it is difficult to secure a safety distance during sudden braking of the preceding vehicle, and frequent warnings are performed due to the inability to secure the safety distance, and thus the driver must intervene.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The object of the present invention is to induce a smooth traffic flow while optimizing the target vehicle distance (safety distance) between the own vehicle and the preceding vehicle in consideration of the driving characteristics of the preceding vehicle, thereby inducing a smooth traffic flow. The present invention relates to a cruise control method of a vehicle that maintains a safe distance to prevent frequent driver intervention.

1 is a flowchart illustrating a cruise control method of a conventional vehicle;

2 is a block diagram of a cruise control apparatus for a vehicle applied to the present invention;

3 is a flowchart showing a cruise control method of a vehicle according to the present invention;

4 is a view showing a control example according to the cruise control method of FIG.

5 is a timing chart according to the control example of FIG. 4.

* Description of the symbols for the main parts of the drawings *

21: Vehicle speed sensor 22: Inter-vehicle distance detection sensor

23: control lever 30: control unit

40: actuator 50: display unit

51: Constant driving mode display lamp 52: Following control mode display lamp

53: alarm display lamp

The present invention is to achieve the above object, when the preceding vehicle is present in front of the own vehicle, the target vehicle distance calculation step of calculating the target vehicle distance and the target vehicle distance to be maintained, and the distance between the vehicle and the preceding vehicle And a vehicle speed control step of controlling a brake actuator or a throttle valve actuator such that the inter-vehicle distance measuring step of measuring and the inter-vehicle distance measured in the inter-vehicle distance measuring step converge to the target inter-vehicle distance calculated in the target inter-vehicle distance step. A cruise control method, comprising: a deceleration calculation step of calculating a deceleration speed of the preceding vehicle; and a maximum deceleration speed so that the target inter-vehicle distance can be varied when the deceleration speed calculated in the deceleration speed calculation step is larger than a reference deceleration speed. And calculating a preliminary inter-vehicle distance based on the preliminary inter-vehicle distance. It shall be.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a cruise control apparatus applied to the present invention will be described with reference to FIG. 2.

As shown in the figure, the inter-vehicle distance detection sensor 22 is installed in front of the vehicle as the inter-vehicle distance detection means so as to detect the inter-vehicle distance between the preceding vehicle and the own vehicle. ) Is preferably implemented with a laser radar.

Also, at least one wheel is provided with a vehicle speed sensor 21 which magnetically detects the rotational speed of the wheel as the vehicle speed detecting means so as to detect the traveling speed of the host vehicle.

In addition, a control lever 23 is provided in the driver's seat to adjust the vehicle speed when driving at a constant speed or to adjust the inter-vehicle distance when following a preceding vehicle.

In addition, the signals of the aforementioned sensors 21 and 22 and the control lever 23 are input to the controller 30. Here, the controller 30 includes the input / output ports 31 and 35, a ROM 33 in which a processing program to be described later is stored, a CPU 32 which performs calculation according to the program stored in the ROM 33, RAM 34 or the like which stores the calculation result from the CPU 32.

In addition, an actuator 40 for controlling the traveling speed of the vehicle, that is, a throttle actuator 41 and a brake actuator 42 is provided in accordance with the processing result of the CPU 32.

In addition, when the present inter-vehicle distance becomes narrower than the inter-vehicle distance allowed by the driver, an alarm operation is performed, and a display unit 50 for displaying whether the present control is vehicle speed control or inter-vehicle distance control is provided in the driver's seat. Here, the display unit 50 is composed of a constant speed driving mode display lamp 51 according to the vehicle speed control, the following control mode display lamp 52 according to the vehicle distance control and the alarm display lamp (and buzzer) 53 according to the alarm operation. do.

Next, a cruise control method according to the present invention will be described with reference to the aforementioned components and FIG. 3.

When the cruise control is selected from the driver and the inter-vehicle distance and vehicle speed information to be maintained are input through the control lever 23 installed in the driver's seat (S31), the CPU 32 advances the preceding vehicle through the inter-vehicle distance detection sensor 22. Determine the presence of (S32). For example, when the laser radar is used as the inter-vehicle distance detection sensor 22, it is determined whether the preceding vehicle is present depending on whether the vehicle exists within the effective measurement distance (about 100M).

<Constant Driving Mode>

When it is determined that the preceding vehicle does not exist in the determination step S32, the CPU 32 lights the constant speed driving mode display lamp 51 installed in the driver's seat so that the driver can recognize that the current driving mode is the constant speed driving mode ( Vi) to indicate that the vehicle is in the constant speed driving mode (S321).

In addition, the CPU 32 calculates a vehicle speed of the host vehicle by calculating a signal input through the vehicle speed sensor 21 (S322). That is, the vehicle speed of the host vehicle is measured by counting an input pulse signal in proportion to the number of revolutions of the wheel.

When the vehicle speed of the host vehicle is measured in measurement step S322, the CPU 32 reads the reference vehicle speed stored in the RAM 34 by the operation of the driver's control lever 23 in step S31 and displays the magnitude of the current vehicle speed. Compared with (S323).

When the vehicle speed of the host vehicle converges to the reference vehicle speed in the comparison determination step S323 (the host vehicle speed ≒ the reference vehicle speed), the control flow of the CPU 32 is returned without performing a separate control operation.

If the vehicle speed of the host vehicle is larger than the reference vehicle speed, the CPU 32 outputs a control signal to the actuator 50 so as to converge the vehicle speed of the host vehicle with the reference vehicle speed to decelerate the host vehicle (S324). Here, the deceleration control is performed by the brake actuator 42 of the electromagnetic hydraulic circuit, for example, the VDC system, which generates the brake hydraulic pressure and performs the braking operation irrespective of the brake pedal operation according to the driver's braking intention.

On the contrary, when the vehicle speed of the host vehicle is smaller than the reference speed in the determination step S323, the CPU 32 accelerates and controls the host vehicle by outputting a control signal to the actuator 40 so that the vehicle speed of the host vehicle converges on the reference vehicle speed. Here, the acceleration control is performed by the throttle valve actuator 41 for adjusting the opening and closing angle of the throttle valve regardless of the operation of the accelerator according to the driver's acceleration will.

As such, when there is no preceding vehicle, the constant speed driving mode is performed through steps S321-325.

<Following mode-Attention classification process>

On the other hand, when it is determined in step S32 that the preceding vehicle is present, the CPU 32 turns on the following driving mode display lamp 52 installed in the driver's seat so that the driver can recognize that the current driving mode is the following driving mode. Indicates that the vehicle is in the following driving mode (S33).

Further, the CPU 32 calculates the vehicle speed of the preceding vehicle by arithmetic processing the signal input through the inter-vehicle distance detection sensor 22 (S34).

When the vehicle speed of the preceding vehicle is measured in the measuring step S34, the CPU 32 calculates the deceleration speed A of the preceding vehicle by differentiating the measured vehicle speed (S35). Here, the reason for taking only the deceleration speed of the preceding vehicle without excluding the acceleration of the preceding vehicle is to consider the deceleration speed of the preceding vehicle, that is, the driving characteristics of the preceding vehicle due to sudden braking, as described below. This is to change the distance between cars (safety distance).

When the deceleration speed of the preceding vehicle is calculated in step S35, the CPU 32 calculates the reference deceleration speed SA (for example, 1.0 g) from the ROM 33 to determine the calculated deceleration speed A and the ambient demand grade. It reads and compares the size (S36). Here, the deceleration actually detected is compared and judged based on the negative value or its absolute value.

When the deceleration speed A of the preceding vehicle is greater than the standard deceleration speed SA in the comparison judgment step S36, the CPU 32 determines whether the current state is in the state of maintaining a demand grade (S37). Since the process has not been classified as the attention demand grade, the process proceeds to step S38, while the current state is classified as the attention demand grade, the calculated deceleration rate is stored in the RAM 34 at the maximum deceleration rate and the count is started (S38). Here, the purpose of starting the count is to determine the maintenance state of the attention demand grade.

When step S38 has been performed, the CPU 32 performs step S34 again to measure the vehicle speed of the preceding vehicle. Here, the reason for performing the step S34 again is for the release of the ambient demand grade over time.

When the vehicle speed of the preceding vehicle is measured in the measuring step S34, the CPU 32 calculates the deceleration speed A of the preceding vehicle by differentiating the measured vehicle speed (S35).

When the deceleration speed of the preceding vehicle is calculated in step S35, the CPU 32 calculates the reference deceleration speed SA (for example, 1.0 g) from the ROM 33 to determine the calculated deceleration speed A and the ambient demand grade. Read and compare the size (S36).

If the deceleration speed (A) of the preceding vehicle calculated in the comparison judgment step S36 is larger than the reference deceleration speed (SA), the CPU 32 determines whether the current state is the state of the attention demand grade (S37). In step S371, the process proceeds to step S371.

When the control flow proceeds to step S371, the CPU reads the calculated deceleration rate and the pre-stored maximum deceleration rate from the RAM 34 and compares the size thereof.

When the deceleration calculated in the comparison determination step S371 is greater than the previously stored maximum deceleration, the maximum deceleration previously input is discarded and the maximum deceleration is updated with the calculated deceleration (S372). Here, the reason for updating the maximum deceleration is to change the target inter-vehicle distance (safety distance) to the optimum (maximum) distance according to the deceleration speed of the preceding vehicle, as will be described later.

The CPU 32 also updates the attention grade classification time. That is, the time counted from step S38 is reset and a new count is started. Here, the reason for starting the count anew is to determine the maintenance state of the attention demand grade over time.

If the deceleration calculated in the comparison determination step S371 is smaller than the previously stored maximum deceleration, the flow advances to step S380 to update only the time point classified as the caution grade without updating the maximum deceleration. In other words, the count is newly started. The reason why the maximum deceleration is not updated is that the target inter-vehicle distance is calculated based on the maximum deceleration.

<Following Mode-Caution of Attention Level>

In the case of maintaining the caution grade by the above-described process, if the deceleration speed of the preceding vehicle calculated in step S35 is smaller than the standard deceleration speed based on the vehicle speed measured in step S34 (S36), the process proceeds to step S361 for a reference time. It is determined whether this has elapsed.

If it is determined that the time counted from the time classified as the attention demand grade in the determination step S361 has passed the reference time (for example, one minute), the attention attention grade is released and classified as a general driving grade (S362).

In addition, the CPU 32 resets the counted time from the time point classified as the caution class, and sets the maximum deceleration previously stored in the RAM 34 to '0' (S363). In other words, the driving pattern of the preceding vehicle is determined to be relatively stable, and thus the target inter-vehicle distance (safety distance) is optimally maintained (minimum) as will be described later.

If it is determined in step S361 that the reference time has not elapsed, the control flow returns to step S34.

<Following Mode-Calculation of Target Distance and Vehicle Control Process According to Attention Grade>

When maintaining the caution grade according to step S373 or step S380, the CPU 32 reads the maximum value of the deceleration speeds of the preceding vehicle stored in the RAM 34 and reserves it based on the equation stored in the ROM 33. The inter-vehicle distance is calculated and the calculation result is stored in the RAM 34 (S374). Here, the preliminary inter-vehicle distance is obtained by equation (2).

(Equation 2) Spare distance = basic distance + maximum acceleration speed of preceding vehicle * Headway Time * Headway Time

In the above formula, the basic inter-vehicle distance is an arbitrary value set according to the driver's safety awareness, and is usually set to be shorter than the conventional spare inter-vehicle distance.

Therefore, when the preceding vehicle frequently performs rapid deceleration, the inter-vehicle distance is increased by the maximum deceleration speed * Headway Time * Headway Time meter (m) of the preceding vehicle so as to prevent a collision accident due to sudden stop of the preceding vehicle during driving. do.

When the preliminary inter-vehicle distance is calculated in step S374, the CPU 32 reads the preliminary inter-vehicle distance from the RAM 34 and calculates the target inter-vehicle distance TL based on the arithmetic expression stored in the ROM 33. The result is stored (S375). Here, the target inter-vehicle distance TL is obtained by equation (3).

(Equation 3) Target Distance (TL) = Headway Time * Own Vehicle Speed + Spare Distance (m)

When the target inter-vehicle distance TL is calculated in the above step, the CPU 34 calculates a signal input through the inter-vehicle distance detection sensor and measures the inter-vehicle distance with the preceding vehicle (S376).

When the inter-vehicle distance (L) with the preceding vehicle is measured in step S376, the CPU 32 reads the measured inter-vehicle distance (L) and the target inter-vehicle distance (TL) from the RAM 34 and compares the size thereof. (S377).

When the vehicle speed of the host vehicle converges to the reference vehicle speed in the comparison determination step S377 (the host vehicle speed-the reference vehicle speed), the control flow of the CPU 32 is returned without performing a separate control operation.

If the inter-vehicle distance L is greater than the target inter-vehicle distance TL in the determination step S377, the CPU 32 sends a control signal to the actuator 50 such that the inter-vehicle distance L converges to the target inter-vehicle distance TL. The output is accelerated to control (S43). That is, the vehicle speed of the host vehicle is accelerated by adjusting (increasing) the opening and closing angle of the throttle valve.

On the contrary, when the inter-vehicle distance L is less than the target inter-vehicle distance TL in the determination step S377, the CPU 32 outputs a control signal to the actuator 40 to decelerate the control so that the inter-vehicle distance becomes wider to the target inter-vehicle distance. . That is, the brake hydraulic pressure is generated to perform the braking operation or to adjust (decrease) the opening and closing angle of the throttle valve to decelerate the vehicle speed of the host vehicle.

<Following Mode-Calculation of Target Distance and Vehicle Control Process According to General Driving Class>

On the other hand, when it is determined that the reference time has elapsed in the determination step S361, the CPU 32 releases the current caution grade (classified as the general driving grade) and resets the information stored in the RAM 34 (S362). ). That is, it is determined that the traveling pattern of the preceding vehicle is relatively stable.

When the attention demand grade is released in step S362, the CPU 32 sets the deceleration speed of the preceding vehicle to zero (S363).

If the deceleration speed of the preceding vehicle is set to 0 in step S363, the flow advances to step S374 to calculate the preliminary inter-vehicle distance based on Equation 2 described above. Therefore, the distance between the target vehicle = the base vehicle distance + 0, the vehicle distance becomes narrower by the maximum deceleration speed * HeadwayTime * HeadwayTime meter (m) than when the vehicle of attention demand in front of the vehicle. As a result, an excessive inter-vehicle distance with the preceding vehicle at the time of driving is reduced to an appropriate inter-vehicle distance, so that the traffic flow is relatively smooth.

When the target inter-vehicle distance TL 'is calculated in step S375, the inter-vehicle distance is variably controlled according to the traveling pattern of the preceding vehicle by sequentially performing the above-described steps S376-S379.

The following describes the classification, maintenance, and release process of the attentional grades disclosed in FIGS. 4 and 5 with reference to the above-described control flow.

Example 1 If the deceleration speed of the preceding vehicle calculated in step S35 is 1.5g, the condition of step S36 is satisfied, and the flow proceeds to step S37. At this time, since it has not been classified as the attention demand grade in the previous process, the process proceeds to step 38 to classify the current state as the attention demand grade, starts counting, and stores the calculated deceleration rate as the maximum deceleration rate. Here, observation of the deceleration of the front vehicle (prior vehicle) is repeated every predetermined period, but only a few times are shown for convenience.

If the deceleration of 0.5 g is calculated (step S35) at a time after the non-specified time, for example, 30 seconds has elapsed after being classified as the caution required grade, the condition of step S36 is not satisfied, and the flow proceeds to step S361. In addition, since the counted time has not passed the reference time (for example, one minute), the process returns to step S34. At this time, the time registered as the attention demand grade and attention demand grade (00:00) is maintained continuously.

In addition, when the deceleration of 0.7g is calculated (S35) at the time when the non-specific time, for example, one minute has elapsed (S35), the condition of step S36 is not satisfied. Proceeds to S362 to release the attention required grade (classified as a general driving grade) while setting the maximum deceleration (1.5g) previously stored to 0 (S363). Thereafter, the flow advances to step S374 to sequentially perform the above-described steps.

Example 2 If the deceleration speed of the preceding vehicle calculated in step S35 is 1.5g, the condition of step S36 is satisfied and the flow proceeds to step S37. At this time, since it has not been classified as the attention demand grade in the previous process, the process proceeds to step 38 to classify the current state as the attention demand grade, starts counting, and stores the calculated deceleration rate as the maximum deceleration rate.

If the deceleration of 1.2g is calculated (step S35) at a time after a specific time, for example, 34 seconds have elapsed after being classified as a precautionary grade, the step is greater than the reference deceleration (1.0g). Proceed to At this time, since the calculated deceleration rate (1.2g) is smaller than the preset maximum deceleration rate (1.5g), the flow proceeds to step S380 to update (register) the classification point of the demand grade from 00:00 to 00:34 and newly count. To start. Thereafter, the flow advances to step S374 to calculate the target distance, and returns to step S31 when there is no vehicle control.

In addition, when the deceleration of 0.5g is calculated (step S35) at a time when it is counted from the non-specified time, for example, the first attention demand grade, and 01:00 has elapsed, it is smaller than the reference deceleration (1.0g). If so, the flow proceeds to step S361. In addition, since the newly counted time has not passed the reference time (for example, one minute), the process returns to step S34. At this time, the time (00:34) registered as the attention demand rating and attention demand rating is maintained continuously.

In addition, when the deceleration of 0.4g is calculated (S35) at a non-specific time, for example, when the newly counted 1 minute elapses (01:34), the condition of step S36 is not satisfied, and the flow proceeds to step S361. Since the reference time has elapsed, the process proceeds to step S362 to release the caution class (classified as a general driving class), reset the count, and set the previously stored maximum deceleration (1.5 g) to 0 (S363). Thereafter, the flow advances to step S374 to sequentially perform the above-described steps.

Example 3 If the deceleration speed of the preceding vehicle calculated in step S35 is 1.6g, the condition of step S36 is satisfied, and the flow proceeds to step S37. At this time, since it has not been classified as the attention demand grade in the previous process, the process proceeds to step 38 to classify the current state as the attention demand grade, starts counting, and stores the calculated deceleration rate as the maximum deceleration rate.

If the deceleration of 2.1g is calculated (step S35) at a time after a non-specific time, for example, 56 seconds have elapsed after being classified as a cautionary grade, the step is greater than the reference deceleration (1.0g). Proceed to In this case, since the calculated deceleration speed 2.1g is greater than the preset maximum deceleration speed 1.5g, the flow proceeds to step 372 to update the preset maximum deceleration speed 1.6g to 2.1g. Further, the flow advances to step S373 to update (register) the attention grade classification time point from 00:00 to 00:56, and to start a new count. Thereafter, the flow advances to step S374 to calculate the target distance, and returns to step S31 when there is no vehicle control.

In addition, when the deceleration of 0g is calculated (step S35) at the time when 01:00 has elapsed since it is counted from the non-specified time, for example, as the first attention demand grade, the case is smaller than the reference deceleration (1.0g). The process proceeds to step S361. In addition, since the newly counted time has not passed the reference time (for example, one minute), the process returns to step S34. At this time, the time (00:56) updated (registered) to the attention demand grade, the maximum acceleration and the attention demand grade is continuously maintained.

In addition, when a deceleration of 0.2 g is calculated (S35) at a non-specific time, for example, when a newly counted 1 minute elapses (01:56), the condition of step S36 is not satisfied, and the flow proceeds to step S361. Since the reference time has elapsed, the flow advances to step S362 to release the caution grade (classified as a general driving grade), reset the count, and set the stored maximum deceleration speed (2.1g) to 0 (S363). Thereafter, the flow advances to step S374 to sequentially perform the above-described steps.

Example 4 If the deceleration speed of the preceding vehicle calculated in step S35 is 1.3g, the condition of step S36 is satisfied, and the flow proceeds to step S37. At this time, since it has not been classified as the attention demand grade in the previous process, the process proceeds to step 38 to classify the current state as the attention demand grade, starts counting, and stores the calculated deceleration rate as the maximum deceleration rate.

If the deceleration of 1.1g is calculated (step S35) at a time after a non-specific time, for example, 34 seconds have elapsed after being classified as a demand grade, it is the case that it is larger than the reference deceleration (1.0g), and then step S371. Proceed to At this time, since the calculated deceleration rate (1.1g) is smaller than the preset maximum deceleration rate (1.3g), the flow proceeds to step S380 to update (register) the classification point of the demand grade from 00:00 to 00:34 and newly count it. To start. Thereafter, the flow advances to step S374 to calculate the target distance, and returns to step S31 when there is no vehicle control.

In addition, when a deceleration of 2.0 g is calculated (step S35) at a time when it is counted from a non-specific time, for example, the first attention demand grade, and 00:55 elapses, it is larger than the reference deceleration (1.0 g). If so, the process proceeds to step 372 and the preset maximum deceleration (1.3g) is updated to 2.0g. In addition, the flow advances to step S373 to update (register) the attention grade classification time point from 00:34 to 00:55 and start a new count. Thereafter, the flow advances to step S374 to calculate the target distance, and returns to step S31 when there is no vehicle control.

In addition, when the deceleration of 0g is calculated (step S35) at a time when the time is classified as a non-specific time, for example, the first attention demand grade, and 01:55 has elapsed, the condition of step S36 is not satisfied. The process proceeds to S361, and since the reference time has elapsed, the process proceeds to step S362 to release the caution class (classified as a general driving class), reset the count, and set the previously stored maximum deceleration (2.0 g) to zero ( S363). Thereafter, the flow advances to step S374 to sequentially perform the above-described steps.

According to the present invention as described in detail above, by varying the target distance (safety distance) between the own vehicle and the preceding vehicle in consideration of the driving characteristics of the preceding vehicle, even if the preceding vehicle frequently performs a rapid deceleration, the inter-vehicle distance is wider To prevent collision accidents, to maintain smoother traffic flows by maintaining a narrower distance when the preceding vehicle is relatively stable, and to maintain the optimal safety distance according to the driving pattern of the preceding vehicle. There is an effect that can be prevented.

Claims (4)

A target inter-vehicle distance calculating step of calculating a distance between the preceding vehicle and the target vehicle to be maintained when the preceding vehicle exists in front of the own vehicle; an inter-vehicle distance measuring step of measuring the distance between the preceding vehicle and the own vehicle; In the cruise control method of a vehicle having a vehicle speed control step of controlling a brake actuator or a throttle valve actuator so that the inter-vehicle distance measured in the step is converged to the target inter-vehicle distance calculated in the target inter-vehicle distance calculation step, A deceleration calculation step of calculating a deceleration of the preceding vehicle; If the deceleration calculated in the deceleration calculation step is greater than the standard deceleration for determining the cautionary grade, the deceleration calculated in the deceleration calculation step is stored as the maximum deceleration and the target vehicle distance is calculated based on the deceleration. Cruise control method of a vehicle, characterized in that. The method of claim 1, A classification classification step of classifying the current state as a cautionary grade, starting counting, and storing the calculated deceleration rate as the maximum deceleration rate when the deceleration rate calculated in the deceleration calculation step is greater than the reference deceleration rate; In the classifying step, if it is classified as a cautionary grade and the count time does not pass the reference time, if the calculated deceleration is larger than the reference deceleration and the calculated deceleration is larger than the stored maximum deceleration, the maximum stored deceleration A maximum deceleration updating step of updating the speed to the calculated deceleration again, resetting the counted time and starting a new count; In the classifying step, if it is classified as a cautionary grade and the count time does not pass the reference time, if the calculated deceleration is larger than the reference deceleration and the calculated deceleration is smaller than the stored maximum deceleration, A attention grade classification time update step of resetting the counted time and starting a new count without updating the deceleration rate, And calculating a target distance based on the maximum deceleration stored in the maximum deceleration updating step or the caution class classification time updating step. The method of claim 2, A reference time elapsed step of judging whether the reference time has elapsed when the deceleration is classified as a cautionary grade in the classification step and the calculated deceleration is again smaller than the reference deceleration in the deceleration calculation step; If it is determined that the reference time has elapsed in the reference time elapsed judging step, and releases the attention demand grade, and resets the counted time and sets the maximum stored deceleration rate to zero, and includes a attention demand release step And a target vehicle distance is calculated based on the maximum deceleration stored in the caution required class release step. The method of claim 1, wherein the target distance calculation is In case of maintaining the caution class, set the maximum deceleration among the decelerations calculated in the deceleration calculation step above, and set the maximum deceleration to 0 when the caution class is released. Calculating by substituting the maximum deceleration x headway time x headway time).