KR101405600B1 - Distance control method - Google Patents

Abstract

More particularly, the present invention relates to a method of controlling an inter-vehicle distance, more precisely, by determining the on / off state of a brake accurately, thereby reducing an unstable or frightening feeling given to a driver when the target inter- The present invention relates to an inter-vehicle distance control method.

To this end, according to the present invention, when the inter-vehicle distance from the preceding vehicle is shorter than the target inter-vehicle distance and the relative speed of the subject vehicle is faster than the preceding vehicle, the inter-vehicle distance control method .

Brake, Vehicle distance, Brake booster, Master cylinder, ABS

Description

Distance control method {Distance control method}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a headway distance control method, and more particularly, to a headway distance control method capable of eliminating an anxiety or a fear given to a driver in a travel control apparatus.

Generally, in a running control device equipped with an inter-vehicle distance control device and a target speed control device, if the preceding vehicle decelerates, the vehicle automatically decelerates. Fig. 1 is a block diagram showing a conventional running control apparatus. The target deceleration is calculated and compared with the deceleration of its own vehicle detected by the acceleration sensor 5, the braking is controlled so as to coincide with the target deceleration .

1 is an inter-vehicle distance measuring device, 2 is a vehicle speed sensor, 3 is an inter-vehicle distance control unit, 6 is a target vehicle speed control unit, 7 is a brake control unit, and 8 is acceleration control.

2 shows a general configuration of an ACC (Adaptive Cruise Control). ACC is a device that automatically travels at a constant speed while maintaining a constant distance from the preceding vehicle.

The ACC controls the inter-vehicle distance to the preceding vehicle and controls to maintain the specified inter-vehicle distance. For example, if the measured inter-vehicle distance is smaller than the specified inter-vehicle distance, the vehicle automatically brakes to reduce the speed. If the inter-vehicle distance from the preceding vehicle is greater than the designated inter-vehicle distance, the vehicle accelerates to increase the speed.

Japanese Patent Laying-Open No. 4-314638 discloses a collision avoidance apparatus in which the target deceleration is calculated from the relative speed and the inter-vehicle distance of a preceding vehicle interposed in a train of cars, and the braking is controlled based on the target deceleration. In this case, if the speed of the preceding vehicle is slow, it is possible to determine the target deceleration without a rapid brake even if the inter-vehicle distance is short. That is, abrupt braking can be avoided.

Japanese Unexamined Patent Publication No. 11-11273 discloses a running control apparatus that prevents rapid braking if the preceding vehicle suddenly decelerates. When the preceding vehicle suddenly decelerates, the target deceleration of the own vehicle becomes large. Therefore, the deceleration of the preceding vehicle is detected to avoid the sudden braking, and the braking is controlled so that the deceleration is performed at a faster speed.

Although the time required for the driver to step on the brake pedal differs depending on the driver and the degree of reaction is different from each other, it is possible to avoid a sudden braking by increasing the allowance time of the braking even if the driver presses the brake pedal late.

However, the above-described conventional travel control device avoids abrupt braking and does not give the driver a sense of incongruity, and it can not be said that the time to start braking is necessarily an appropriate time. For example, in ACC, when the inter-vehicle distance from the preceding vehicle is shorter than the predetermined inter-vehicle distance, the braking operation is performed. Therefore, there is a time delay until the braking is applied, so that the inter-vehicle distance becomes shorter.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a brake control apparatus and a brake control method for accurately determining the on / off state of a brake and eliminating an anxiety or fear of giving to a driver when a target vehicle distance becomes short, The present invention provides an inter-vehicle distance control method.

The above object is achieved by a headway distance control method,

And the target inter-vehicle distance is varied according to the subject vehicle speed when the inter-vehicle distance from the preceding vehicle is shorter than the target inter-vehicle distance and the relative speed of the subject vehicle is faster than the preceding vehicle.

Preferably, measuring an inter-vehicle distance and a vehicle speed from the vehicle-to-vehicle distance measuring device and the vehicle speed sensor; Obtaining a brake pressure from the inter-vehicle distance and the vehicle speed on the assumption that the brake pressure is proportional to a value obtained by multiplying the vehicle mass by the acceleration; And controlling the brake pressure to fall within a brake pressure range of an upper limit and a lower limit determined by the function of the vehicle speed.

The step of controlling the brake pressure to fall within the upper and lower limits of the brake pressure range determined by the function of the vehicle speed includes steps of increasing the brake pressure so as not to rotate the wheel by the valve and reducing the brake pressure to rotate the wheel And alternately performing the steps.

Therefore, according to the headway distance control method of the present invention, braking of the vehicle can be accurately determined by controlling the on / off of the brake with the offset to the target inter-vehicle distance and the offset target, There is no overrun or approach to the preceding vehicle, and does not give the driver any anxiety or fear.

In addition, sudden deceleration can be solved by controlling the brake pressure to fall within the brake pressure range of the upper and lower limits determined by the function of the vehicle speed.

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

3 is a block diagram showing a configuration of a travel control apparatus according to an embodiment of the present invention.

3, the ACC refers to the travel control unit 10, and the travel control unit 10 controls the ON and OFF of the direct brake.

The travel control unit 10 is provided with an inter-vehicle distance measuring device for measuring the distance to the preceding vehicle traveling ahead of the subject vehicle (s), and the distance is measured by a Milli-wave radar, A laser radar, an ultrasonic sensor, or the like.

Further, since the travel control unit 10 receives a signal from the vehicle speed sensor and the acceleration sensor can calculate the vehicle acceleration from the vehicle speed sensor, the acceleration sensor may not be provided in the travel control unit 10. [ In addition, the target inter-vehicle distance is set in advance in the travel control section 10, and the throttle 12 (Throttle) is turned off at the time of brake control.

The headway distance control method according to the present invention will now be described in detail.

Fig. 4 is a graph showing the inter-vehicle distance according to the break timing of the prior art prior to the improvement. When the target inter-vehicle distance from the preceding vehicle in the vehicle deceleration is set to the brake line, It is impossible to maintain the target inter-vehicle distance.

FIG. 5 is a graph showing the inter-vehicle distance according to the brake timing according to the present invention after improvement. As shown in the figure, according to the speed of the subject vehicle, it is offset by τ, that is, So that the own vehicle is widened beyond the distance between the target preceding vehicle and the preceding vehicle, so that the vehicle does not approach the preceding vehicle.

FIG. 6 is a graph for explaining a brake control method according to the present invention. When the brake control is turned on, the brake pressure is controlled to fall between the brake pressure upper limit (upper limit Line) and the brake lower limit. In this case, the dotted line indicates the case where the brake pressure is not controlled, and the solid line indicates the case where the brake pressure is controlled according to the present invention.

Fig. 7 is a block diagram showing the configuration of the brake control section 12. Fig. The brake control unit 12 is constituted by a brake booster 14, a master cylinder 15 and an ABS 16 (Antilock Brake system).

The brake booster receives the brake signal and amplifies the brake signal. The master cylinder receives the amplified signal to generate the brake hydraulic pressure. The ABS 16 receives the generated hydraulic brake pressure, adjusts the pressure, .

The ABS alternately performs the steps of stopping the rotation of the wheel by boosting the brake pressure by the valve control, reducing the brake pressure, and rotating the wheel.

Such a mechanism further includes a hydraulic pressure sensor to control the upper limit of the brake pressure and the lower limit of the brake pressure.

The preceding vehicle traveling at a speed v _leading and characters for the vehicle as the speed v _real in the running and have, inter-vehicle distance to the preceding vehicle from the chair vehicle distance d, the throttle 12 to a position where the chair vehicle that the preceding vehicle Throttle Off, Assuming Deceleration Acceleration a Using the _{sup position} , the time to travel until the speed becomes equal to the preceding vehicle is as follows.

Here, assuming that the vehicle speed of the preceding vehicle is constant and the relative vehicle is regarded as a reference relative to the preceding vehicle, it is considered that the subject vehicle is approaching the preceding vehicle stopping at the acceleration a _{sup position} , second speed v _real -v _leading . At this time, the relative distance d * at which the host vehicle travels until the relative speed becomes zero is expressed by the following equation.

If Equation 1 is substituted into Equation 2,

Here, _{supposing that} 2a _{sup position} = a _{sup_ para} , equation (4) is expressed by the following equation.

The condition that the vehicle travels at the same speed as the preceding vehicle by the target inter-vehicle distance τ _set · v _l (τ _set is the set inter-vehicle time) is expressed by the following equation.

In addition, in order to restrict deceleration, a logic for controlling the brake is added when the speed falls within a certain speed difference.

Break-on condition

Using the following Equation (7), the parameters are added and the position for operating the brake is defined as follows.

τ _{Brake_on_para} is a parameter introduced to offset the value obtained by Equation (6).

In this case, the following equation is introduced to stop the braking at the point where the speed drops below the preceding vehicle because v < _real <v _leading leads to excessive deceleration and becomes lower than the controllable speed.

And? _{V brake_on_para} is a parameter that defines a speed range for performing braking.

In the case of the break-on, the equations (7) and (8) are determined as the and condition.

Break-off condition

Using Equation (6), the positions where the parameters are added and the brakes are released are defined as follows.

τ _{Brake_on_para} is a parameter introduced to offset the value obtained by Equation (6) as well as the break-on condition.

In the current program, control is performed using the same value.

Since the deceleration is excessively lowered by this condition alone, it becomes lower than the controllable speed. Therefore, the following expression is introduced to stop the operation at a point where the speed is lower than the preceding vehicle.

And? _{V brake_on_para} is a parameter that defines a speed range for performing braking.

In the case of the break-off, the equations (9) and (10) are determined as the or condition.

Processing when the brake determination condition is not suitable

When the above condition is not satisfied, the following rules are applied.

1. Initial condition

It is called break-off condition at start-up.

2. Break-on time

Even when the brake-on condition is not satisfied, it is called "brake-on" until the brake-off condition is satisfied.

3. At break-off time

Even when the brake-off condition is not satisfied, it is called "brake-off" until the brake-on condition is satisfied.

In addition, in order to adjust the inter-vehicle distance from the preceding vehicle by using the above-mentioned brake timing, the brake pressure should be given to the driver. Here, the present invention proposes a method of relieving brake pressure.

The inter-vehicle distance is the acceleration of the square of the relative speed of the preceding vehicle and the secondary of the vehicle. The acceleration at the time of braking has a proportional relationship between the brake pressure and the acceleration multiplied by the vehicle mass. Therefore, the brake pressure is obtained from the equation obtained by multiplying the vehicle mass by the proportional coefficient as a parameter and obtaining the inter-vehicle distance.

If there is a preceding vehicle relative to the preceding vehicle, the relative acceleration a _{real_relativity} of the subject vehicle and the time t required for the velocity change between Δv _{real_relativity} = 0 where the relative vehicle velocity of the subject vehicle becomes zero, The following relation holds.

Δv _{real_relativity} = a _relativity · t

The relative distance traveled at this time is shown in the following equation.

Substituting Equation 1 into Equation 1 yields

This data can be summarized as the following equation (12).

Here, the following relationship is established between the weight m of the vehicle, the relative acceleration a _{real_relativity,} and the brake pressure P _brake .

From the equations (12) and (13), the travel distance d =? V _{real_relativity} dt is _expressed as follows.

Here, if the inter-vehicle distance in the current state is L and the target inter-vehicle time τ _{brake_pressure_para in} which the vehicle speed v _leading of the preceding vehicle and the vehicle speed become equal to each other, the distance d running until the same speed as the preceding vehicle is expressed as follows .

The following equations are required from equations (14) and (15).

From the above equation, a non-dimensional term is obtained, and the part is multiplied by a parameter to obtain an adjustment term.

If the vehicle speed v _real is used to express the equation,

Calculate the brake pressure in the above equation.

However, the upper limit value P _{upper_limit} and the brake booster 14, the lower limit value P _{lower_limit} to cope with if the pressure is too increased is input to the following equation.

Are parameters for determining the upper and lower limits of the pressure of the brake, respectively.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And all of the various forms of embodiments that can be practiced without departing from the technical spirit.

1 is a block diagram showing a conventional travel control apparatus,

2 is a block diagram showing a general configuration of an ACC,

3 is a block diagram showing a configuration of a travel control apparatus according to an embodiment of the present invention,

4 is a graph showing the inter-vehicle distance according to the break timing of the prior art before the improvement,

5 is a graph showing the inter-vehicle distance according to the brake timing of the present invention after improvement,

6 is a graph for explaining a brake control method according to the present invention,

7 is a block diagram showing a configuration of a brake control unit according to the present invention.

Description of the Related Art

10: Driving control unit 11: Excel

12: Throttle 13: Brake control section

14: Brake booster 15: Master cylinder

16: ABS 17: Brake pedal

Claims (3)

delete In the headway distance control method, When the inter-vehicle distance from the preceding vehicle is shorter than the target inter-vehicle distance and the relative speed of the subject vehicle is faster than the preceding vehicle, the target inter-vehicle distance is varied according to the subject vehicle speed, Measuring an inter-vehicle distance and a vehicle speed from an inter-vehicle distance measuring device and a vehicle speed sensor; Obtaining a brake pressure from the vehicle-to-vehicle distance and the vehicle speed on the assumption that the brake pressure is proportional to a value obtained by multiplying the vehicle mass by the acceleration; And controlling the brake pressure to fall within an upper and lower brake pressure range defined by a function of the vehicle speed. The method of claim 2, The step of controlling the brake pressure to fall within the upper and lower limits of the brake pressure range defined by the function of the vehicle speed includes steps of stepping up the brake pressure so as not to rotate the wheel by the valve and releasing the brake pressure to rotate the wheel To-vehicle distance control.

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