Abstract:
Disclosed is a control method for use in a system for controlling a distance between vehicles. The method comprises a) controlling, in response to the leading vehicle&#39;s deceleration, deceleration of the control vehicle; b) controlling stop speed of the control vehicle so that the control vehicle approaches the leading vehicle at a constant speed without stopping; c) controlling the control vehicle to stop smoothly exactly at a position spaced from the leading vehicle by a predetermined stop distance; and d) controlling the start of the control vehicle after determining whether the leading vehicle has started or moved forward.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Korean Patent Application No. 10-2010-0034409, filed on Apr. 14, 2010, the entire contents of which are incorporated herein for all purposes by this reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a method for controlling a distance between vehicles, and more particularly to a method for optimally controlling automatic stop and start of a vehicle using a system for controlling a distance between vehicles. 
         [0004]    2. Background Art 
         [0005]    Some vehicles are equipped with an adaptive cruise control (ACC) system, that is, a system for controlling a distance between vehicles. A recent ACC system provides a full speed range control including a function of stop and go. 
         [0006]    The full speed range ACC system may secure the credibility for sensing and controlling obstacles in a short distance area at a low speed, and may quickly recognize a vehicle approaching the vehicle equipped with the ACC system, such that the vehicle can be adequately controlled. 
         [0007]    In some vehicles, the ACC system is functionally coupled with a local optical radar that can sense a wide-angle at a short distance. Accordingly, in case of a vehicle with such system, other vehicles running ahead of the vehicle on the same road as well as other vehicles running on an adjacent road can be recognized at a short distance. 
         [0008]    Some methods for controlling a distance between vehicles were proposed, as disclosed in Japanese Patent Application Publication Nos. 2004-322729, 2002-067733, and 2000-043618, which are incorporated herein by reference. 
         [0009]    These methods, however, are disadvantageous in some respects. For example, some of the methods cannot control the vehicle to start in response to the start of a vehicle ahead of the vehicle. Some of the methods cannot control the decelerating speed and/or stopping speed of the vehicle. Moreover, as shown in  FIG. 1 , a view for explaining the relationship of a relative distance and a request stop distance between a leading vehicle  100  and a following vehicle  200  equipped with a system for performing the control method(s), even when the vehicle  100  stops, the vehicle  200  is controlled to stop well prior to approaching the vehicle  100  in spite of quite a distance error to fit the relative speed. In addition, some of the methods may not control the vehicle to stop at a targeted position and may sacrifice driver&#39;s driving feel. 
         [0010]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE DISCLOSURE 
       [0011]    In an aspect, the present invention provides a method for optimally controlling automatic stop and start for use in a system for controlling a distance between vehicles. The control method is performed in a deceleration control area, a stop speed control area, a stop control area and a start control area. 
         [0012]    In the deceleration control area, in response to the leading vehicle&#39;s deceleration, deceleration of the control vehicle is controlled by considering a relative acceleration, a relative speed and a relative distance of the control vehicle with respect to the leading vehicle. 
         [0013]    In the stop speed control area, stop speed of the control vehicle is controlled so that the control vehicle approaches the leading vehicle at a constant speed without stopping, prior to entering the deceleration control area. 
         [0014]    In the stop control area, the control vehicle is controlled to stop smoothly exactly at a position spaced from the leading vehicle by a predetermined stop distance; and 
         [0015]    In the start control area, the control vehicle is controlled to start by the result of determination of whether the leading vehicle has started or moved forward. 
         [0016]    In another aspect, the present invention provides a system for controlling a distance between vehicles. A stop &amp; go system is a system for enabling automatic stop and start in a conventional system for controlling a distance between vehicles. The stop &amp; go system comprises an electronic control unit (ECU), a sensor and an actuator. The ECU includes an exclusive ECU for the stop &amp; go system or is included in a conventional brake control system (i.e., electronic stability control (ESC) system). The sensor for the stop &amp; go system includes a sensor for sensing front objects such as radar, lidar and vision. Although one sensor is used basically, two or more sensors may be simultaneously used in order to improve reliability. The actuator includes an engine and brake. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a view for explaining the relationship of a relative distance and a request stop distance between a leading vehicle and a following vehicle in a system for controlling a distance between vehicles. 
           [0018]      FIG. 2  is a view for explaining that a method for controlling a distance between vehicles according to an embodiment of the present invention is performed in a deceleration control area, a stop speed control area, a stop control area, and a start control area. 
           [0019]      FIG. 3  is a flowchart of a method for optimally controlling automatic stop and start according to an embodiment of the present invention. 
           [0020]      FIG. 4  is a detailed flowchart for a step of stop speed control and a step of stop prevention control shown in  FIG. 3 . 
           [0021]      FIG. 5  is a detailed flowchart for a step of stop control shown in  FIG. 3 . 
           [0022]      FIG. 6  is a detailed flowchart for a step of decision of stop condition shown in  FIG. 5 . 
           [0023]      FIG. 7  is a detailed flowchart for a step of start control shown in  FIG. 3 . 
           [0024]      FIG. 8  is a view for illustrating the speed of a leading vehicle, the speed of a following vehicle, and a relative distance between the vehicles when the following vehicle is optimally controlled by a method according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    With reference to the accompanying drawings, reference will now be made in detail to exemplary embodiments of the present invention so that those skilled in the art may embody easily. But, the present invention may be embodied in various embodiments, which are not limited by the embodiments illustrated herein. In the accompanying drawings, some elements regardless of the description of the present invention are omitted in order to describe the present invention clearly, and, like reference numerals refer to the like elements throughout. 
         [0026]    As shown in  FIG. 2 , a method for controlling a distance between vehicles according to the present invention is performed in 4 areas: a deceleration control area, a stop speed control area, a stop control area, and a start control area. The reference number  200  is referred to a vehicle (“control vehicle”) in which the control method is performed and the reference number  100  is referred to a vehicle (“leading vehicle”) running ahead of the vehicle  200 , unless otherwise specified. 
         [0027]    The deceleration control area refers to an area in which the deceleration of the control vehicle  200  is controlled considering a relative acceleration, a relative speed and a relative distance of the control vehicle  200  with respect to the leading vehicle  100  according as the leading vehicle  100  decelerates. 
         [0028]    The stop speed control area refers to an area in which the stop speed of the control vehicle  200  is controlled so that the control vehicle  200  may keep constant the approaching speed without stopping prior to entering the deceleration control area. 
         [0029]    The stop control area refers to an area in which the control vehicle  200  is controlled to stop at a targeted position exactly and smoothly. 
         [0030]    The start control area refers to an area in which whether the leading vehicle  100  is started or moved forward a little is determined and according to the determination the control vehicle  200  is controlled to start. 
         [0031]    Referring to  FIG. 3 , a method for optimally controlling a distance between vehicles according to an embodiment of the present invention is described. 
         [0032]    The method includes a step of deceleration control S 100 , a step of stop speed control S 200 , a step of stop prevention control S 300 , a step of stop control S 400  and a step of start control S 500 . 
         [0033]    In step S 100 , according as the leading vehicle  100  decelerates, the control vehicle  200  is controlled to decelerate considering a relative acceleration, a relative speed and a relative distance of the control vehicle  200  with respect to the leading vehicle  100 . 
         [0034]    In step S 200 , the control vehicle  200  is controlled, prior to entering the deceleration control area, to approach the leading vehicle  100  at a constant speed without stopping. 
         [0035]    In step S 300 , in case where the leading vehicle  100  stops and the control vehicle  200  is going to stop at a position farther than a request stop distance from the control vehicle  200 , the control vehicle  200  is controlled to move to a position that meets the request stop distance without stopping by adjusting a value of the relative distance with regard to the relative speed of the control vehicle  200 . 
         [0036]    In step S 400 , the control vehicle  200  is controlled to be able to stop at an exact position that meets the request stop distance smoothly. 
         [0037]    In step S 500 , whether the leading vehicle  100  is started or moved forward a little is determined and the control vehicle  200  is controlled to start according to the determination result. 
         [0038]    The above-described steps of S 100  to S 500  will now be explained in more detail with reference to  FIGS. 4 to 7 . 
         [0039]      FIG. 4  is a detailed flowchart for a step of stop speed control and a step of stop prevention control shown in  FIG. 3 . 
         [0040]    According to a conventional TJA (Traffic Jam Assist) system, the amount of the deceleration of the control vehicle is calculated from a relative distance between the control vehicle and the leading vehicle, a relative speed of the control vehicle with regard to the leading vehicle, and the acceleration of the leading vehicle. In case where the leading vehicle stops ahead of the control vehicle, however, there is a problem that the control vehicle may stop well prior to approaching the leading vehicle in spite of quite a distance error to fit the relative speed, as described above with reference to  FIG. 1 . In order to overcome the problem, the control method according to the present invention defines the stop speed control area. 
         [0041]    Referring to  FIG. 4 , in step S 210 , whether the speed of the leading vehicle  100  is lower than a predetermined low driving speed is determined. If it is determined that the speed of the leading vehicle  100  is not lower, the step S 100  is performed. 
         [0042]    On the other hand, if it is determined that the speed of the leading vehicle  100  is lower, the speed of the leading vehicle  100  is set to the predetermined low driving speed (S 220 ). 
         [0043]    In other words, the step of stop speed control S 200  decides whether the speed of the leading vehicle  100  is lower than the low driving speed in order to decide whether the leading vehicle  100  stops or not, and, if not, sets the speed of the leading vehicle  100  to the low driving speed so that the control vehicle  200  may drive at the low driving speed. Accordingly, it is possible to prevent that the control vehicle  200  stops at a position longer than the request stop distance. 
         [0044]    In case where the control vehicle  200  stops at a position longer than the request stop distance in spite of the above-described step of stop speed control S 200 , the control method may, optionally, include a step of stop prevention control S 300 . That is, in step S 300 , in case where the leading vehicle  100  stops and the control vehicle  200  is going to stop at a position longer than the request stop distance, a value of the relative distance with respect to the relative speed of the control vehicle  200  may be adjusted so that the control vehicle  200  moves to the request stop distance without stopping. 
         [0045]    More specifically, in case where the control vehicle  200  is going to stop at a position longer than the request stop distance, whether the relative distance is longer than the request stop distance and whether the control vehicle  200  is stopped are determined (S 310 ). 
         [0046]    If it is determined that the relative distance is longer than the request stop distance and the control vehicle  200  is stopped, a value of the relative distance with respect to the relative speed of the control vehicle  200  is adjusted (S 320 ). If, however, it is determined that the relative distance is not longer than the request stop distance or the control vehicle  200  is not stopped, or if the value of the relative distance with respect to the relative speed of the control  200  is adjusted, the step of stop control S 400  is performed. 
         [0047]      FIG. 5  is a detailed flowchart for a step of stop control shown in  FIG. 3 , and  FIG. 6  is a detailed flowchart for a step of stop control decision shown in  FIG. 5 . 
         [0048]    In general, in order to stably stop a vehicle and remain the stop status, the amount of deceleration should be greater than the one in a general deceleration control. 
         [0049]    Referring to  FIG. 5 , in step S 400 , whether predetermined stop conditions of the control vehicle  200  are satisfied is determined (S 410 ). Here, referring to  FIG. 6 , in step S 410 , for example, whether the leading vehicle  100  stops or not, whether the speed of the control vehicle  200  is lower than the stop speed or not, and whether the relative distance is shorter than the request stop distance may be determined (S 411 ). 
         [0050]    If any of the predetermined stop conditions is not satisfied, it is determined that the stop condition of the control vehicle  200  is not satisfied (S 413 ), in which case the step S 200  is performed. 
         [0051]    On the other hand, if it is determined that the predetermined stop conditions are satisfied, it is determined that the stop condition of the control vehicle  200  is satisfied (S 412 ). In this case, control gains of acceleration, a speed and a distance are changed (S 420 ), and then, a required deceleration is changed on the basis of the changed control gains (S 430 ). According to the changed deceleration, the control vehicle  200  can stably stop (S 440 ). 
         [0052]    Namely, stop conditions of the control vehicle  200  are determined, and a required deceleration is changed by changing the control gains of acceleration/speed/distance of the control vehicle  200  so that the control vehicle  200  is stably stopped. 
         [0053]      FIG. 7  is a detailed flowchart for a step of start control shown in  FIG. 3 . 
         [0054]    In general, for controlling a distance between vehicles, a control vehicle should be controlled to stop if the leading vehicle stops, and start if the leading vehicle starts. If the leading vehicle moves, the relative distance from the control vehicle to the leading vehicle changes. The control vehicle should be controlled to move in order to fit the request distance. But, if the leading vehicle moves by a short distance (for example, 1 m or so), it may be difficult to control the control vehicle to be moved corresponding to the moved distance because of the response time of an actuator, and also, such a control may cause an excessive jolt occasionally. 
         [0055]    In order to prevent the problems, according to an embodiment of the present invention, the control vehicle  200  is controlled to start in only case where the leading vehicle  100  is outside the start control area. 
         [0056]    Referring to  FIG. 7 , in the step of start control S 500 , whether the relative distance is longer than the length of the start control area and whether the speed of the leading vehicle  100  is higher than a predetermined speed of the leading vehicle  100  are determined (S 510 ). 
         [0057]    If it is determined that the relative distance is not longer than the length of the start control area and the speed of the leading vehicle  100  is not higher than the predetermined speed of the leading vehicle  100 , the control vehicle  200  remains stopped (S 520 ). 
         [0058]    If, on the other hand, it is determined that the relative distance is longer than the length of the start control area or the speed of the leading vehicle  100  is higher than the predetermined speed of the leading vehicle  100 , the control vehicle  200  is controlled to start (S 530 ). 
         [0059]    Preferably, the length of the start control area may be determined by tuning. Although the range of the start control area is determined by tuning, the range needs to satisfy at least a value of request stop distance +α. It means that the range of the start control area is required to be larger than the request stop distance. The amount of +α is determined by tuning and a driving environment. 
         [0060]    In addition, in order not to respond to a little movement of the leading vehicle  100 , and in order to restrict the request acceleration according to a small distance error, a dead zone for the distance error may, suitably, be set in the start control area. 
         [0061]      FIG. 8  is a view for illustrating the speed of a leading vehicle, the speed of a following vehicle, and a relative distance between the vehicles when the following vehicle is optimally controlled by a method according to an embodiment of the present invention. 
         [0062]    As shown in  FIG. 8 , according to an embodiment of the present invention, if the speed of the leading vehicle  100  is lower than the low running speed, the control vehicle  200  is controlled to approach the leading vehicle  100  at a constant speed within a specific distance, and the stop conditions of the control vehicle  200  is determined and based on the determination, the control vehicle  200  is controlled to smoothly stop and remain the stop status. Besides, the control vehicle  200  is controlled to smoothly start in response to the start of the leading vehicle  100  while not responding to a little movement of the leading vehicle  100 . 
         [0063]    With the control methods according to the present invention, the control vehicle  200  can smoothly stop while not deteriorating driving quality of a driver and can stop exactly at a position required by the driver. 
         [0064]    The foregoing description of the present invention is intended to be illustrative, and those of ordinary skill in the art will understand that the present invention may be changed into other specific forms without modifying technical conceptions or essential characteristics according to the present invention. Therefore, it must be understood that the above-described embodiment is to be illustrative not to be definitive. 
         [0065]    The present invention is intended to fall within the scope of the following appended claims not within the scope of the detailed description, and accordingly, it must be understood that the meaning and scope of the appended claims and all such changes, modifications and variations induced by the equivalents are included in the scope of the present invention.