Vehicle control system

Abstract

To provide a vehicle control apparatus configured to select an appropriate inter-vehicle gap without delay when making a lane change into an inter-vehicle gap formed between other vehicles on a lane on which a vehicle travels after the lane change.SOLUTION: A vehicle control apparatus includes: vehicle outside detection means 1 which detects inter-vehicle gaps formed between other vehicles traveling on a target lane L2; total candidate calculation means 31 which calculates the total number of candidates of target lane; prescribed skip calculation means 32 which calculates the number of prescribed skips from the total number of candidates; safety calculation means 33 which calculates degrees of safety of the detected inter-vehicle gaps; safety threshold setting means 34 which sets the maximum value of degree of safety of inter-vehicle gaps of candidate numbers equal to or less than the number of prescribed skips, as a safety threshold; and inter-vehicle gap selection means 35 which selects, as a target lane, an inter-vehicle gap having a degree of safety equal to or higher than the safety threshold. The total candidate calculation means 31 calculates the total number of candidates on the basis of an estimated traffic density value calculated by traffic density estimation means 30.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle control device that controls the operation of a vehicle such as an automobile.

Background Art

[0002] In the automatic driving control of a vehicle such as an automobile, there may be a need to change lanes from the own lane to another lane. As a technique related to such a lane change, for example, in Japanese Patent No. 6444067 (Patent Document 1), a technique is disclosed in which the inter-vehicle distance and the collision prediction time with another vehicle in the lane change destination are calculated, and the lane change is started when the inter-vehicle distance and the collision prediction time equal to or greater (less) than a threshold value are calculated.

[0003] Further, Japanese Unexamined Patent Application Publication No. 2020-52559 (Patent Document 2) discloses a technique for permitting a lane change when the relative relationship (collision margin time TTC) with the preceding vehicle or the following vehicle in the lane change destination is greater than a threshold value. In addition, Japanese Unexamined Patent Application Publication No. 2018-92484 (Patent Document 3) discloses a technique for permitting a lane change if the degree of influence on the surrounding environment when the own vehicle changes lanes (for example, the degree of deceleration of the vehicles in the lane change destination and the following vehicle) is within an allowable range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, when changing lanes while manually driving a vehicle, the driver observes the flow of traffic in the lane they are changing to, finds a relatively large gap depending on the level of congestion at the time, and then changes lanes into that gap. In autonomous driving, the same kind of flexible lane changes as in manual driving are required, but conventional technology has not been able to fully achieve this.

[0006] For example, in conventional technologies such as those described in Patent Documents 1-3, lane changes are performed based on predetermined thresholds and tolerance ranges. However, since the comparison with these thresholds is only performed within the sensor's detection range, even if a more suitable distance exists outside the detection range, it may be missed. Furthermore, there is no perspective that appropriately reflects the traffic environment during lane changes in the thresholds, which can lead to situations where the thresholds are not set appropriately in relation to the traffic volume.

[0007] This invention was made in consideration of the above circumstances, and its purpose is to provide a vehicle control device that can select a suitable gap between vehicles without delay when changing lanes into a gap formed between other vehicles in the destination lane. [Means for solving the problem]

[0008] To achieve the above objective, the present invention adopts the following solution. That is, as described in claim 1, a vehicle control device that controls the vehicle to change from its own lane to a gap between vehicles formed between another vehicle traveling in the destination lane, comprising: a gap detection means for detecting a gap between vehicles that has appeared in the destination lane; a safety degree calculation means for calculating the safety degree of the gap between vehicles detected by the gap detection means; a total candidate number calculation means for calculating the total candidate number, which is an estimated value of the total number of gaps between vehicles that are candidates for lane change destinations; and an integer obtained by truncating the decimal part of the square root of the total candidate number or the square of the total candidate number. The system includes: a means for calculating a specified number of skips, which sets an integer obtained by rounding up the decimal part of the root to the specified number of skips; a means for setting a safety threshold, which assigns a candidate number, which is a sequential number in the order of appearance, to the gaps between vehicles that appear in the lane to be changed, and sets the highest safety level among the gaps between vehicles whose candidate number is less than or equal to the specified number of skips as the safety threshold; and a means for selecting a gap between vehicles as the lane to be changed, which after the safety threshold has been set, compares the safety level of the gaps between vehicles that appear in the lane to be changed with the safety threshold, and selects a gap between vehicles with a safety level equal to or greater than the safety threshold as the lane to be changed.

[0009] According to the above solution method, it is possible to select the gap between vehicles with the highest expected safety value from among multiple potential gaps between vehicles for lane changes. This effectively avoids attempting to change lanes to gaps with insufficient safety, or continuing to search for a lane change destination even after a suitable gap has been found, thus enabling smoother and safer lane changes to be performed earlier.

[0010] A preferred embodiment based on the above solution method is as described in claim 2 and subsequent claims of the patent. That is, the safety degree calculation means sets the distance between the vehicle and the vehicle itself, which is the distance between the front vehicle and the rear vehicle that forms the vehicle gap, as the safety degree of the vehicle gap (corresponding to claim 2). In this case, the safety degree of the vehicle gap is appropriately evaluated by the distance between the front and rear vehicles, so that an appropriate lane change destination can be selected.

[0011] Furthermore, the safety threshold setting The method involves comparing the minimum safety level required to perform a safe lane change with the average safety level estimated from traffic flow, setting the smaller value as the lower limit of the safety level threshold, comparing the lower limit of the safety level threshold with the safety level threshold set as the maximum safety level among the vehicle gaps where the candidate number is less than or equal to the specified number of skips, and setting the larger value as the safety level threshold (corresponding to claim 3). In this case, the safety level threshold will never be smaller than the lower limit of the safety level threshold, so the safety level of the selected vehicle gap will not become too small. On the other hand, since the lower limit of the safety level threshold is set to the smaller of the minimum required safety level and the average safety level estimated from traffic flow, the safety level threshold may be smaller than the minimum required safety level (minimum inter-vehicle time). Therefore, even when traffic density is high and the distance between vehicles is generally small, selecting the vehicle gap itself does not become difficult, and the best selection can be made under that traffic density.

[0012] Furthermore, the system includes a traffic density calculation means for calculating an estimated value of the traffic density of the lane to be changed, and the total number of candidates calculation means calculates the total number of candidates based on the estimated value of the traffic density (corresponding to claim 4). In this case, the total number of candidates will appropriately reflect the traffic density at the time of lane change control, and can be set accurately.

[0013] The traffic density calculation means compares the calculated traffic density value calculated based on detection within the vehicle with the traffic density information value obtained from an external source, and sets the larger value as the estimated traffic density (corresponding to claim 5). In this case, for example, even if the calculated traffic density value becomes smaller than the actual traffic density due to an accidental event, the estimated traffic density can be accurately set.

[0014] Also, the above SelfIt is provided with an automatic driving control means for controlling the automatic driving of a vehicle, and the automatic driving control means executes a lane change to the inter-vehicle gap selected by the inter-vehicle gap selection means so as to control the Self vehicle (corresponding to claim 6). In this case, in automatic driving, it is possible to appropriately select the inter-vehicle gap that becomes the lane change destination, and a safe and suitable lane change can be executed without delay.

[0015] Also, the automatic driving control means changes the driving pattern in the lane change according to the safety level of the inter-vehicle gap selected as the lane change destination (corresponding to claim 7). In this case, in automatic driving, according to the safety level of the inter-vehicle gap at the change destination, an appropriate driving pattern can be flexibly selected. For example, when the safety level is low, by reducing the lateral speed of the host vehicle, a safe lane change can be smoothly executed. If the value is small, reduce the lateral speed of the vehicle.

Advantages of the Invention

[0016] According to the present invention, when changing lanes to the inter-vehicle gap in the target lane to be changed, a suitable inter-vehicle gap with the maximum expected safety level can be selected without delay.

Brief Description of the Drawings

[0017] [Figure 1] A block configuration diagram showing an example of the control system of the present invention. [Figure 2] A block configuration diagram showing an example of the control system of the present invention. [Figure 3] A diagram for explaining the outline of the present invention. [Figure 4] A diagram for explaining the calculation of the inter-vehicle time. [Figure 5] A flowchart showing an example of the control procedure for lane change control in the present invention. [Figure 6] A flowchart showing an example of the control procedure for estimating traffic density in the present invention. [Figure 7] A flowchart showing an example of the control procedure for estimating the total number of candidates in the present invention. ​ [Figure 8] A flowchart illustrating the control procedure when the number of vehicles is small. [Figure 9] A flowchart illustrating the control procedure for updating the safety threshold. [Figure 10] A flowchart showing the control procedure when the actual gap between vehicles is small. [Figure 11] A flowchart illustrating the control procedure for executing lane changes. [Figure 12] A diagram illustrating the method for performing a lane change according to the present invention. [Figure 13] A diagram illustrating the method for performing a lane change according to the present invention. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described below based on the attached drawings. Figure 1 shows a block diagram of an example of the control system of the present invention. As shown in the figure, the control system includes an electronic control unit (ECU) U. The electronic control unit U is a control device composed of, for example, a microcomputer. The control system includes a vehicle external detection means (vehicle gap detection means) 1, a vehicle state detection means 2, and an information acquisition means 3, and signals (information) are input to the electronic control unit U from each of the means 1 to 3. Furthermore, control signals are transmitted from the electronic control unit U to the vehicle control system 5.

[0019] The vehicle external detection means 1 is a means for detecting external conditions of the vehicle, such as the road conditions while driving and other vehicles in the surrounding area, and includes an external camera 10 and a radar detector 11. In the present invention, the vehicle external detection means 1 functions as a vehicle gap detection means for detecting the gap (distance between vehicles) between vehicles traveling on the lane to which the vehicle is changing lanes.

[0020] The vehicle state detection means 3 is a means for detecting the driving state of the vehicle and is equipped with the following sensors: a vehicle speed sensor 12, an acceleration sensor 13, a gyro sensor 14, a steering angle sensor 15, an accelerator sensor 16, and a brake sensor 17.

[0021] Information acquisition means 3 is a means for acquiring various information necessary for control, and includes a positioning sensor 18 consisting of GPS and a traffic information acquisition means 19 that acquires traffic information from an external traffic information system (e.g., probe data or road traffic census). Vehicle control system 5 is a means for controlling the operation of the vehicle, and consists of steering control means 21, engine control means 22, and brake control system 23.

[0022] As shown in Figure 2, the electronic control unit U includes a traffic density estimation means 30, a total number of candidate means 31, a specified number of skips calculation means 32, a safety level calculation means 33, a safety level threshold calculation means 34, a vehicle gap selection means 35, and an automatic driving control means 36 as functions for performing lane change control. These means are provided as programs within the electronic control unit U.

[0023] With the configuration described above, the vehicle control device of the present invention performs lane change control so that when the vehicle changes lanes, it selects a suitable gap between vehicles (vehicles) from among the gaps formed between vehicles in the destination lane and the vehicle, and drives the vehicle to change lanes to that gap. The lane change control by the vehicle control device of the present invention will be described in detail below.

[0024] Figure 3 shows an overview of lane change control by the vehicle control device of the present invention. As shown in the figure, the vehicle LE, which is driving autonomously using the vehicle control device of the present invention, is traveling in its own lane R1, which is the right lane of road R. In this situation, it may become necessary to change lanes to the destination lane R2, which is the left lane. For example, when turning left at an intersection or interchange ahead, or when stopping on the left shoulder of the destination lane R2, it is necessary to change the vehicle LE to the destination lane R2 beforehand. In such cases, lane change control by the vehicle control device is executed.

[0025] As shown in the diagram, multiple other vehicles L1, L2, ... are traveling in the destination lane R2, and gaps G1, G2, ... are formed between the preceding and succeeding vehicles LOj, LOj+1. In this example, the speed of the vehicle LE is lower than the speed of the other vehicles L1, L2, ... traveling in the destination lane R2. Therefore, the vehicle LE moves relatively backward relative to the line of other vehicles L1, L2, ..., and the driving position of the vehicle LE takes on positions adjacent to the gaps G1, G2, ... in sequence. The vehicle control device sequentially evaluates the gaps G1, G2, ... that appear in succession at adjacent positions, selects a gap suitable for lane change, and performs control to execute a lane change to that gap.

[0026] Although Figure 3 shows the case where the vehicle speed of the own vehicle LE is slower than the vehicle speed of other vehicle Lj in the destination lane R2, the same control can be performed even when the vehicle speed of the own vehicle LE is faster than the vehicle speed of other vehicle Lj in the destination lane R2. In that case, the own vehicle LE will sequentially overtake other vehicles on the destination lane R2, sequentially detect the gap Gi between vehicles that it has caught up with from behind, and select the gap between vehicles to which it will change lanes.

[0027] For the gap G between vehicles on the destination lane R2, a safety score S is set as an evaluation value that indicates the suitability of the lane as a destination. The safety score S is set so that the higher the safety of changing lanes across that gap, the higher the value. In one embodiment of the present invention, as will be described in more detail later, the safety score S is calculated as the time T between the vehicle LE and the vehicles before and after the gap G.

[0028] When changing lanes, the driver attempts to change to the lane with the highest possible safety level S from among the rows of gaps G1, G2, ... formed in the destination lane R2 based on the traffic flow at that time. In this case, assuming that it is not possible to return to a gap that has already been passed, the driver selects the best gap from among the multiple gaps that are passed in sequence.

[0029] In selecting the inter-vehicle gap for vehicle control, the vehicle control device of the present invention utilizes knowledge from the basic reward problem. Here, the basic reward problem is a type of optimal stopping problem (a variation of the secretary problem), in which, when selecting one candidate from a plurality of candidates that appear sequentially, an optimal policy is adopted to maximize the expected value of the reward of the selected candidate. In the optimal policy for the basic reward problem, there is an integer threshold for the number of candidates that should be skipped, and this threshold is floor(N), where N is the total number of candidates. 1 / 2 ) or ceil(N 1 / 2 It is known that ) holds true. Here, floor(x) is the floor function and ceil(x) is the ceiling function. The basic reward problem itself is well known, so no further explanation will be given.

[0030] When using the basic reward problem, the vehicle control device first calculates the total number of candidates N as an estimate of the total number of inter-vehicle gaps that could be candidates for change destinations, using the total number of candidate calculation means 31. Specifically, the total number of candidates N is calculated as the total number of inter-vehicle gaps that are expected to appear during the critical time TL in the traffic flow of the destination lane R2 at that time (estimated from the traffic density acquired by the traffic information acquisition means 19).

[0031] Here, the limit time TL is the amount of time that can be spent deciding whether or not to change lanes (the time that can be spent selecting the destination lane), and it is determined according to the driving route set in the autonomous driving system. For example, if the driving route is set to turn left at an intersection ahead, the decision on whether or not to change lanes must be made and the lane change completed before reaching that intersection. Therefore, the limit time TL is set so that the lane change can be completed before reaching this intersection.

[0032] Next, the predetermined skip number calculation means 32 calculates the predetermined skip number C based on the calculated total number of candidates N. Here, the predetermined skip number C corresponds to the threshold in the optimal policy (cutoff rule) of the basic reward problem, and is the number of candidates to be skipped in order to select the candidate whose expected value of the evaluation value is maximized. In this embodiment, in accordance with the basic reward problem, the floor function or ceiling function of the square root of the total number of candidates N is set as the predetermined skip number C. That is, the predetermined skip number C is calculated based on the following equation (1) or equation (2). C=floor(N 1 / 2 ) …(1) C=ceil(N 1 / 2 ) …(2) Based on the total number of candidates N and the specified number of skips C calculated in this way, the vehicle control device selects the vehicle gap to which the lane change will take place. Specifically, the vehicle control device detects vehicle gaps G that appear sequentially in the lane to which the lane change will take place R2, based on the analysis of images captured by the external camera 10 of the vehicle external detection means 1 and detection by the radar detector 11. A candidate number i is set as a sequential number in the detection order for the detected vehicle gaps G, and the safety level calculation means 33 calculates the safety level Si for each vehicle gap Gi. The vehicle control device then refrains from changing lanes to vehicle gaps Gi until the candidate number i of the vehicle gap Gi exceeds the specified number of skips C.

[0033] Furthermore, it is possible to set a predetermined sufficient threshold SE (a threshold for the level of safety required to allow for a sufficiently safe lane change) for the safety level of the gap between vehicles. If the evaluation value Si of the detected gap Gi is equal to or greater than the sufficient threshold SE, the system will execute a lane change to that gap Gi. This allows the system to complete the lane change quickly if a safe gap Gi is found without any problems, even before reaching the predetermined number of skips C.

[0034] Based on the safety degree Si (1 ≤ i ≤ C) of the gap between vehicles acquired while the lane change is being postponed, the safety degree threshold calculation means 34 determines the safety degree threshold ST. Specifically, the safety degree Smax, which is the highest safety degree Si among the gaps Gi between vehicles with candidate number i that are less than or equal to the specified number of skips C, is set as the safety degree threshold ST.

[0035] As described above, the safety threshold ST is generally set to the maximum safety level Smax, but it may be adjusted to improve safety during lane changes. More details will be provided later.

[0036] In this way, once the candidate number i of the inter-vehicle gap exceeds the specified number of skips C and the safety threshold ST is determined, the safety degree Si of each detected inter-vehicle gap Gi is calculated, and the inter-vehicle gap selection means 35 compares the safety degree Si with the safety threshold ST. If the safety degree Si of the inter-vehicle gap Gi is equal to or greater than the safety threshold ST, that inter-vehicle gap Gr is selected as the lane change destination. This maximizes the expected value of the safety degree Sr of the inter-vehicle gap Gr selected as the lane change destination, enabling a smooth and safe lane change.

[0037] The automatic driving control means 36 controls the driving control system 5 while referring to the signal from the vehicle state detection means 2 in order to change the lane of its own vehicle A to the selected gap Gr between vehicles, and executes the lane change.

[0038] Figure 3 shows that the total number of candidates N is 9, and the number of specified skips C is 3 (=9). 1 / 2This example illustrates the case where... In this example, no lane change is performed until candidate number i of the inter-vehicle gap reaches 3. Only the safety degrees S1, S2, and S3 of each inter-vehicle gap G1, G2, and G3 are detected, and the maximum value of safety degrees S1 to S3 is set to the safety threshold ST. Subsequently, for inter-vehicle gaps G4, G5, ... from candidate number 4 onwards, the detection of safety degrees S4, S5, ... is performed and compared with the safety threshold ST. When an inter-vehicle gap Gr with a safety degree Sr equal to or greater than the safety threshold ST is found, that inter-vehicle gap Gr is selected and a lane change is performed.

[0039] Next, the setting of the safety level S in one embodiment of the present invention will be described. In this embodiment, the safety level S of the gap between vehicles is set using the time T between the vehicle and another vehicle traveling in the lane to which the vehicle is changing.

[0040] Here, the interval time T is the value obtained by dividing the distance between the preceding vehicle and the following vehicle by the speed of the following vehicle (the time required for the following vehicle to travel the distance between itself and the preceding vehicle). Therefore, in this invention, for the vehicles before and after the vehicle that form the gap G between vehicles (the front vehicle LF and the rear vehicle LR), it is necessary to consider the front interval time TF between the vehicle LE and the front vehicle LF, and the rear interval time TR between the vehicle LE and the rear vehicle LR, as the interval time T.

[0041] Referring to Figure 4, the time between vehicles ahead TF is the distance DF between your vehicle LE and the vehicle ahead LF in the direction of travel, divided by the speed VE of your vehicle LE. In other words, the time between vehicles ahead TF is calculated using the following equation (3). TF = DF / VE …(3) The rear-end distance TR is the value obtained by dividing the distance DR between the rear vehicle LR and the vehicle LE in the direction of travel by the speed VR of the rear vehicle LR. In other words, the rear-end distance TR is calculated by the following equation (4). TR = DR / VR …(4) If the position of your vehicle LE overlaps laterally with the vehicle in front LF, the distance DF between your vehicle and the vehicle in front LF (distance DR) is 0, and therefore the distance between your vehicle and the vehicle in front (distance TF) is 0. Similarly, if the position of your vehicle LE overlaps laterally with the vehicle behind LR, the distance DR between your vehicle and the vehicle behind LR is 0, and therefore the distance between your vehicle and the vehicle behind (distance TR) is 0.

[0042] Furthermore, if visibility is poor due to factors such as the curvature and gradient of the road, surrounding structures, or weather conditions at the time of lane change, and other vehicles cannot be detected within the line of sight, the following time TR may be estimated by using the speed VR of the following vehicle LF as the average speed of vehicles in the destination lane R2 estimated from traffic density.

[0043] As can be seen from the above definition formulas (3) and (4), the longer the following time T (following time TF for the front vehicle, following time TR for the rear vehicle), the safer the lane change becomes. If it is too short, the risk is high, and a lane change with that following time T is unacceptable. Therefore, the minimum following time TM (following time TFM for the front vehicle, following time TRM for the rear vehicle) is defined as the minimum following time that is acceptable for performing a lane change (i.e., the minimum following time required for a lane change).

[0044] When performing a lane change, for example, if the distance between the vehicle in front (TF) and the vehicle behind (TR) are greater than or equal to the distance between the vehicle in front (TFM) and the distance between the vehicle behind (TRM), respectively, and more than 3 seconds have elapsed since the turn signal started flashing, the lane change will begin, generating lateral speed (starting to move towards the destination lane R2).

[0045] On the other hand, if either the front following time TF or the rear following time TR falls below the corresponding front following time TFM or rear following time TRM, the vehicle will not change lanes in principle. However, if there is a high necessity to change lanes, the vehicle will perform driving maneuvers to allow other vehicles in the destination lane R2 to pass, and will begin changing lanes when the front following time TF and rear following time TR are equal to or greater than the front following time TFM and rear following time TRM, respectively. Situations where there is a high necessity to change lanes include when it is necessary to turn right or left after changing lanes from the set driving route, or when it is necessary to exit at an interchange.

[0046] Next, an example of calculating the safety threshold ST when the safety level S is defined as the interval time T (a pair of the front interval time TF and the rear interval time TR) will be explained. In this case, the safety threshold ST is determined from the lower limit STL of the safety threshold, which is calculated based on the traffic density estimated by the traffic density estimation means 30, and the maximum value Smax of the safety level detected during the search up to the specified number of steps C. The lower limit STL of the safety threshold is set to accommodate situations where a lane change must be performed even when the interval time TM is below the minimum interval time, such as when there is a high need to change lanes.

[0047] To calculate the lower limit of the safety threshold STL, first, the estimated front-to-front-vehicle interval TFE and estimated rear-to-vehicle interval TFR are calculated as the average values ​​of the safety degree S (inter-vehicle interval T) estimated from the traffic flow at that time. In the calculation, first, the average inter-vehicle distance Da and average speed Va of the vehicles are estimated based on the traffic density estimated by the traffic density estimation means 30, and by assuming a predetermined ratio (m:n) between the front-to-front-vehicle interval TF and the rear-to-vehicle interval TR, the average front-to-front-vehicle interval DFa and average rear-to-vehicle interval DRa are calculated from the average inter-vehicle distance Da so as to satisfy this ratio. The estimated front-to-front-vehicle interval TFE and estimated rear-to-vehicle interval TFR are calculated by replacing the front-to-front-vehicle interval DF and rear-to-vehicle interval DR in the above equations (3) and (4) with the average front-to-front-vehicle interval DFa and average rear-to-vehicle interval DRa, respectively, and replacing the vehicle speed VE and rear-to-vehicle speed VR with the average vehicle speed Va.

[0048] The estimated front-to-front following time (TFE) and the minimum front-to-front following time (TFM) are compared, and the smaller value is set as the lower limit of the front safety threshold (STFL). Similarly, the estimated rear-to-front following time (TFR) is compared with the minimum rear-to-front following time (TRM), and the smaller value is set as the lower limit of the rear safety threshold (STRL).

[0049] The safety threshold ST is set as a pair of front safety threshold STF and rear safety threshold STR, so the settings for the front safety threshold STF and the rear safety threshold STR are performed separately. In addition, the safety degree Si of the vehicle gap Gi is detected as a pair of front gap time TFi and rear gap time TRi, but the maximum front gap time TFmax and the maximum rear gap time TRmax are determined separately for each of the front gap time TF and rear gap time TR (that is, the vehicle gap with TFmax may be different from the vehicle gap with TRmax).

[0050] The front safety threshold STF (front following time threshold TTF) is set to the larger of the maximum front following time TFmax and the lower limit of the front safety threshold STFL. Similarly, the rear safety threshold STR (rear following time threshold TTR) is set to the larger of the maximum rear following time TRmax and the lower limit of the rear safety threshold STFL.

[0051] With these settings, the front safety threshold STF and the rear safety threshold STR may be smaller than the front minimum following time TFM and the rear minimum following time TRM, respectively. In this case, the driving pattern in the lane change execution control, described later, will be changed to address the issue. This will appropriately prevent the vehicle from being unable to find a suitable gap for lane changes, even when traffic density is high and it is difficult to find a gap with a high safety level S, and will allow the vehicle to find the best gap and perform the lane change.

[0052] The safety degree S of the gap between vehicles is a pair of front-vehicle interval time TF and rear-vehicle interval time TR. The comparison of their magnitudes can be performed by defining an appropriate rule and following that rule. For example, one could first compare the front-vehicle interval times TF together to determine which is greater, and if the front-vehicle interval times TF are the same, then compare the rear-vehicle interval times TR together to determine which is greater.

[0053] Next, an example of the control procedure for lane change control by the vehicle control device of the present invention will be described in detail according to the flowcharts from Figure 5 onward. Figure 5 shows the overall flow of lane change control. Lane change control is initiated, for example, when the intention to change lanes from the vehicle's own lane R1 to another lane R2 is expressed during the autonomous driving of the vehicle LE.

[0054] In step S1, the time is initialized and the countdown to the limit time TL begins. In the following step S2, the data of the pre-calculated total number of candidates N and the specified number of skips C are obtained.

[0055] In step S3, vehicles within the line of sight are detected, and in the following step S4, it is determined whether the number of vehicles detected in step S3 is less than two. If the number of vehicles is less than two, the process proceeds to step S14, where the control for a small number of vehicles (see Figure 8) is executed, and the series of controls ends.

[0056] On the other hand, if it is determined in step S4 that there are two or more vehicles, the process proceeds to step S5 and the candidate number is set to 1. Subsequently, in step S6, the safety degree Si of the vehicle gap Gi for candidate number i, which is the target of detection at that time, is detected (if the process has proceeded from step S5, the safety degree S1 of the first vehicle gap G1 is detected).

[0057] In the following step S7, it is determined whether the limit time TL has elapsed since the start of control. If it is determined that the limit time has elapsed, the process proceeds to step S15, where it is determined whether the safety degree S of the vehicle gap Gi for candidate number i at that point is greater than or equal to the minimum vehicle interval time TM.

[0058] In step S15, if it is determined that the minimum following time TM is greater than or equal to the current time, the process proceeds to step S13, where the lane change is executed and the series of processes ends. On the other hand, if it is determined that the following time is less than the minimum time TM, the process proceeds to step S16, where the lane change using the current control (current driving route) is abandoned, a route recalculation is started, and the series of controls ends. In this way, if the limit time has elapsed, the current lane change control cannot be continued any further, so the process of terminating the lane change control is performed at that point.

[0059] On the other hand, if it is determined in step S7 that the limit time TL has not elapsed, the process proceeds to step S8, where it is determined whether the candidate number i at that point exceeds the specified number of steps C. If it does not, the process proceeds to step S17, where the safety threshold update process (see Figure 9) is executed. In step S18, the candidate number is updated (by adding 1 to i), and the process returns to step S6. In other words, the loop of steps S6-S8, S17, and S18 is repeated until the candidate number i reaches the specified number of steps C, and the detection of the safety degree Si of the vehicle gap Gi and the updating of the safety threshold ST based on the detected safety degree Si are repeated.

[0060] On the other hand, in step S8, if it is determined that candidate number i has exceeded the specified number of steps C, the process proceeds to step S9, where it is determined whether or not there is a vehicle gap Gi+1 for the next candidate number i+1. If it is determined that there is no gap (i.e., the actual number of vehicle gaps is less than predicted, and there are no vehicles left to form a gap), the process proceeds to step S19, where the control for when the actual number of vehicle gaps is small (see Figure 10) is executed, and the series of control operations ends.

[0061] On the other hand, if it is determined in step S9 that there is another candidate, then in step S10, it is determined whether candidate number i exceeds the total number of candidates N. If it is determined in this determination that the total number of candidates N does not exceed i, then step S11 is skipped and the process proceeds to step S12.

[0062] On the other hand, if it is determined in step S10 that candidate number i exceeds the total number of candidates N, the process proceeds to step S11, where it is determined whether the time limit TL has elapsed. If the time limit TL has elapsed, the process proceeds to step S15, where the same processing as when it was determined in step S7 that the time limit TL had elapsed is performed, and the series of controls is terminated.

[0063] On the other hand, if the determination in step S11 determines that the limit time TL has not elapsed, the process proceeds to step S12. In other words, even if candidate number i exceeds the total number of candidates N, if the limit time TL has not elapsed, it is assumed that more vehicles than expected have passed through up to that point, and the current gap Gi between vehicles would have originally been a candidate lane change destination with a candidate number less than or equal to the total number of candidates N (if the accuracy of traffic density estimation is high), so the search for a lane change destination continues.

[0064] In step S12, it is determined whether the evaluated value Si of the gap Gi between vehicles is equal to or greater than the safety threshold ST. If it is determined that it is not equal to or greater than the safety threshold ST, the process proceeds to step S18, the candidate number is updated, and the process returns to step S6. In other words, after the candidate number i exceeds the specified number of skips C, the loop of steps S6 to S12 and step S18 is repeated until the evaluated value Si of the gap Gi between vehicles exceeds the safety threshold ST, continuing the detection of the evaluated value Si of the gap Gi between vehicles and the safety threshold ST (searching for a gap between vehicles to change lanes to).

[0065] On the other hand, if a vehicle-to-vehicle gap Gi with a safety degree Si equal to or greater than the safety threshold ST is found in step S12, the process proceeds to step S13, where control is performed to change lanes in that vehicle-to-vehicle gap Gi (see Figure 11), and the series of control operations is terminated.

[0066] Figure 6 is a flowchart showing the processing procedure for estimating traffic density. Traffic density is the number of vehicles per kilometer and is an indicator of the degree of traffic congestion. In this embodiment, the traffic density estimation by the traffic density estimation means 30 is continuously performed while the vehicle LE is in motion, prior to the start of lane change control, and the estimated value of traffic density at that time is updated.

[0067] In step S21, the average inter-vehicle distance Da is calculated based on the detected inter-vehicle distances of other vehicles. That is, the vehicle external detection means 1 continuously detects the inter-vehicle distances of other vehicles prior to lane change control, and the traffic density estimation means 30 continuously calculates the average inter-vehicle distance Da at that time as the average value of the inter-vehicle distances detected within a predetermined time.

[0068] In the subsequent step S2, the traffic density at that time is estimated (calculated) based on the average inter-vehicle distance Da calculated in step S21, and the calculated traffic density value TDC is set as the estimated traffic density value TD. More specifically, the traffic density estimation means 30 calculates the traffic density (number of vehicles per kilometer) at that time using the average inter-vehicle distance Da, the assumed total length of the vehicles, and the average speed Va of the vehicles, and sets the calculated value (calculated traffic density value TDC) as the estimated traffic density value TD. The average speed Va of the vehicles is calculated based on detection by the vehicle external detection means 1.

[0069] In step S23, the traffic information acquisition means 19 acquires traffic density information from an external source (such as a road traffic information system) and sets it as the traffic density information value TDI. In the following step S24, the estimated traffic density value TD (for which the calculated density value TDC is set) is compared with the traffic density information value TDI, and if the traffic density information value TDI is not greater, the series of processes is terminated.

[0070] On the other hand, if the traffic density information value TDI is larger, the process proceeds to step S25, where the traffic density information value TDI is set to the estimated traffic density value TD, and the series of processes ends. In this way, in this embodiment, when setting the estimated traffic density value TD, the traffic density information value TDI is used in addition to the calculated traffic density value TDC, allowing for accurate setting of the estimated traffic density value TD. For example, even if the calculated traffic density value TDC is calculated to be smaller than the actual traffic density due to the effects of waiting at traffic lights, etc., accurate correction can be made using the traffic density information value TDI.

[0071] Figure 7 is a flowchart showing the procedure for calculating the total number of candidates N and the specified number of skips C. In step S31, the limit time TL is calculated. As mentioned above, the limit time TL is the time that can be used to decide whether or not to change lanes, and is determined by the set driving route.

[0072] In the following step S32, the number of passing vehicles that are estimated to pass alongside the vehicle LE during the limit time TL is calculated based on the limit time TL, the estimated traffic density TD, and the average speed Va of the vehicle in the lane change destination.

[0073] In step S33, the total number of candidates N is calculated by subtracting 1 from the number of passing vehicles. In the following step S34, the specified number of skips C is calculated using the above formula (1) or (2), and the series of processes is completed.

[0074] Figure 8 is a flowchart showing the control procedure for the case where the number of vehicles is small (step S14 in the flowchart of Figure 5). In this process, first, in step S41, it is determined whether or not the number of vehicles is 0. If the number of vehicles is 0, a lane change is performed in step S45 and the process ends.

[0075] On the other hand, if it is determined in step S41 that the number of vehicles is not zero (i.e., there is one vehicle), the process proceeds to step S42, where it is determined whether the time between the vehicle and the vehicle in question is equal to or greater than the minimum time. If it is equal to or greater than the minimum time, the lane change is performed in step S45, and the process ends.

[0076] On the other hand, if the determination in step S42 is found to be less than or equal to the minimum following time, the following time is adjusted in step S44, and then the lane change is performed in step S45, after which the process is terminated.

[0077] Figure 9 is a flowchart showing the control procedure for updating the safety threshold (step S17 in the flowchart of Figure 5). In this control, first, in step S51, it is determined whether the candidate number is 1 or not. If the candidate number is 1, the process proceeds to step S52, where the inter-vehicle gap time T (i.e., the front inter-vehicle gap time TF1 and rear inter-vehicle gap time TR1 of the initial inter-vehicle gap G1) is set to the safety threshold SL, and the series of processes ends.

[0078] On the other hand, if the candidate number is not 1, the process proceeds to step S53, where the maximum values ​​of the front and rear vehicle interval times TF and TR up to that point are set to the safety threshold SL, and the series of processes ends. Specifically, the front vehicle interval time TFi of the vehicle gap Gi is compared with the front safety threshold STF (front vehicle interval time threshold TTF) at that point, and the larger value is set to the front safety threshold STF. Similarly, the rear vehicle interval time TRi is compared with the rear safety threshold STR (rear vehicle interval time threshold TTR) at that point, and the larger value is set to the rear safety threshold STR, and the process ends.

[0079] Figure 10 is a flowchart showing the control procedure for the control (step S19 in the flowchart of Figure 5) that is executed when the actual number of gaps between vehicles is less than the estimated total number of candidates and the last gap between vehicles is reached.

[0080] In step S61, it is determined whether the safety level S of the gap between vehicles (the last gap between vehicles) is greater than or equal to the minimum interval time TM. If it is determined that it is greater than or equal to the minimum interval time TM, the process proceeds to step S63, where the last gap between vehicles is selected as the lane change destination, and in step S65, lane change execution control (see Figure 11) is executed to complete the series of processes.

[0081] On the other hand, if in step S61 it is determined that the safety level of the gap between vehicles is less than the minimum interval time TM, then in step S62 it is determined whether the last gap between vehicles is wider than the space behind the vehicles that make up the last gap. If it is determined that it is wider, the process proceeds to step S63, where the last gap between vehicles is selected as the lane change destination, and in step S65 the lane change execution control is executed to end the series of processes.

[0082] On the other hand, if in step S63 it is determined that the last gap between vehicles is not wider than the space behind, the process proceeds to step S64, where the space behind is selected as the lane change destination, and in step S65, lane change execution control is performed to end the series of processes.

[0083] Figure 11 is a flowchart showing an example of the control procedure for lane change execution control (step S13 in the flowchart of Figure 5). The vehicle gap selected as a candidate for lane change according to the present invention will be the one with the highest expected value of safety degree S (interval time T) among the total number of candidate candidates N, but as mentioned above, there is a possibility that a vehicle gap with an interval less than the minimum interval time TM may be selected. This lane change execution control is a control that takes such situations into account and changes the driving pattern during lane change according to the safety degree S (interval time T) of the selected vehicle gap to execute an appropriate lane change.

[0084] In step S71, it is determined whether the safety level S of the selected gap between vehicles is greater than or equal to the minimum interval time TM. If it is determined that the gap is greater than or equal to the minimum interval time TM, the process proceeds to step S72, where a lane change is performed in the situation shown in Figure 12, and the series of controls is terminated.

[0085] To explain in more detail, as shown in Figure 12, behind the front vehicle LF, there is a prohibited area A1 in which, if entered, the front vehicle interval TF becomes the minimum front vehicle interval TFM. Similarly, in front of the rear vehicle LR, there is a prohibited area A2 in which, if entered, the rear vehicle interval TR becomes the minimum rear vehicle interval TRM. When the safety degree S of the vehicle gap G is greater than or equal to the minimum vehicle interval TM, a gap is formed between prohibited areas A1 and A2.

[0086] When changing lanes, a lane changeable area A3 is assumed on the current lane R1 such that the length of the vehicle's direction of travel falls within the gap between prohibited areas A1 and A2. The vehicle LE is then moved into this lane changeable area A3 before changing lanes from the current lane R1 to the destination lane R2. The lane change in step S72 is an example of this.

[0087] On the other hand, if in step S71 it is determined that the safety level S of the selected gap between vehicles is not greater than or equal to the minimum interval time TM, the process proceeds to step S73, where it is determined whether the interval time T of the gap between vehicles G is greater than the interval time TC required to avoid a rear-end collision.

[0088] Here, the collision avoidance interval TC is the interval that allows a following vehicle to stop with ample margin without rear-ending the preceding vehicle, even if the preceding vehicle suddenly decelerates or stops abruptly. This is a less stringent standard than the minimum interval interval TM. The collision avoidance interval TC is calculated using the following formula (5), with respect to the speed v1 of the preceding vehicle, the speed v2 of the following vehicle, the deceleration a1 of the preceding vehicle, the deceleration a2 of the following vehicle, and the reaction time Tr of the following vehicle. TC = Tr - (v² / a² + v1 2 / v2·a1) / 2 …(5) In step 73, if it is determined that the time interval T of the gap G between vehicles is greater than the time interval TC required to avoid a rear-end collision, the process proceeds to step S73, where the lateral speed of the vehicle LE is reduced, and a lane change is performed.

[0089] To explain in more detail, as shown in Figure 13, in this situation, the interval time T of the gap G between vehicles is less than the minimum interval time TM, so there is no gap between the prohibited areas A1 and A2 based on the minimum interval time TM. On the other hand, the interval time T of the gap G between vehicles is greater than the collision avoidance interval time TC, so there is a gap between the prohibited areas A4 and A5 (shown in hatching) formed behind the front vehicle LF and in front of the rear vehicle LR based on the collision avoidance interval time TC. Therefore, in this situation, the vehicle LE should be moved into the lane changeable area A6, whose length in the direction of travel falls between the prohibited areas A4 and A5, and a careful lane change should be performed at a low lateral speed.

[0090] On the other hand, in step S73, if it is determined that the time T for the gap G between vehicles is less than or equal to the time TC for avoiding a rear-end collision, then it is not possible to change lanes as is. In this case, the vehicle LE moves closer to the center line or takes other actions to encourage the rear vehicle LR to yield the right of way. The vehicle waits for the gap G to widen and for a lane change to become possible, then performs the lane change and ends the series of controls. If, even after performing such driving, it is not possible to change lanes and the limit time TL has elapsed, the vehicle abandons the lane change, searches for an alternative route, and heads towards the destination.

[0091] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and appropriate modifications can be made within the scope described in the claims. For example, although the above embodiments have described the case in which the vehicle control device of the present invention is applied to automatic driving control, the scope of application of the present invention is not limited to automatic driving control, but broadly includes general driving assistance.

[0092] Furthermore, although the above embodiment described a case where one lane change is performed within the time limit, the present invention is also applicable when multiple lane changes are performed within the time limit. That is, when multiple lane changes are required within the time limit, the total number of candidates and the specified number of skips are calculated for the entire time limit, just as in the case of one lane change. If a safety threshold is obtained based on this specified number of skips, then the same safety threshold can be used to select the vehicle gap for subsequent lane changes.

[0093] Furthermore, although the above embodiment described an example in which the safety level is calculated by detecting the gap between vehicles one by one, the present invention can also be configured to simultaneously detect the gap between vehicles and calculate the safety level for multiple gaps between vehicles. [Industrial applicability]

[0094] This invention can be used for automatic driving control of vehicles such as automobiles. [Explanation of Symbols]

[0095] U Electronic Control Unit 1. Vehicle external detection means 2. Vehicle status detection means 3 Information acquisition means 5. Vehicle control system 10. Exterior car camera 11. Radar detector 12. Vehicle speed sensor 13. Accelerometer 14. Gyroscope sensor 15. Steering angle sensor 16 Accelerator sensor 17 Brake recovery 18 Positioning sensors 19 Means of obtaining traffic information 21 Steering control means 22 Engine control means 23 Brake control means 30 Traffic density estimation means 31. Method for calculating the total number of candidates 32. Means for calculating the number of specified skips 33 Safety level detection means 34 Safety threshold calculation means 35. Inter-vehicle gap selection means 36 Automatic driving control means LE (Likely referring to a vehicle) LO Other vehicles LF front vehicle LR rear vehicle G gap between vehicles R road R1 own lane R2 Destination lane

Claims

1. In a vehicle control device that controls the vehicle to change from its own lane to a gap formed between it and another vehicle traveling in the destination lane, A vehicle gap detection means for detecting the gap between vehicles that appears in the lane to which the vehicle is to be changed, A safety level calculation means for calculating the safety level of the gap between vehicles detected by the vehicle gap detection means, A means for calculating the total number of candidates, which is an estimated value of the total number of gaps between vehicles that could be candidates for lane changes, A means for calculating the number of predetermined skips, which sets the integer obtained by truncating the decimal part of the square root of the total number of candidates or the integer obtained by rounding up the decimal part of the square root of the total number of candidates as the predetermined number of skips; A safety threshold setting means assigns a candidate number, which is a sequential number in the order of appearance, to the gaps between vehicles that appear in the lane to be changed, and sets the safety threshold to the highest safety level among the gaps between vehicles where the candidate number is less than or equal to the specified number of skips. A vehicle gap selection means that, after setting the safety threshold, compares the safety level of the gaps between vehicles that appear in the lane to be changed to with the safety threshold, and selects a gap between vehicles with a safety level equal to or greater than the safety threshold as the lane to be changed to. A vehicle control device equipped with the following features.

2. In the vehicle control device according to claim 1, The safety level calculation means is a vehicle control device that sets the time between the vehicle itself and the front vehicle and the rear vehicle that form the vehicle gap as the safety level of the vehicle gap.

3. In the vehicle control device according to claim 1 or claim 2, The safety threshold setting means compares the minimum safety level required to perform a safe lane change with the average safety level estimated from traffic flow, sets the smaller value as the lower limit of the safety threshold, and compares the lower limit of the safety threshold with the safety threshold set as the maximum safety level among the safety levels of vehicle gaps where the candidate number is less than or equal to the specified number of skips, sets the larger value as the safety threshold.

4. In the vehicle control device according to any one of claims 1 to 3, The system includes a traffic density calculation means for calculating an estimated value of the traffic density of the lane to be changed, The total candidate number calculation means is a vehicle control device that calculates the total number of candidates based on the estimated traffic density.

5. In the vehicle control device according to claim 4, The traffic density calculation means is a vehicle control device that compares a calculated traffic density value calculated based on detection within the vehicle itself with a traffic density information value obtained from an external source, and sets the larger value as the estimated traffic density.

6. In the vehicle control device according to any one of claims 1 to 5, The vehicle is equipped with an automatic driving control means for controlling the automatic driving of the vehicle, The automatic driving control means is a vehicle control device that controls the vehicle to perform a lane change to the vehicle gap selected by the vehicle gap selection means.

7. In the vehicle control device according to claim 6, The aforementioned automatic driving control means is a vehicle control device that changes the driving pattern during lane changes so as to reduce the lateral speed of the vehicle itself when the safety level of the gap between vehicles selected for the lane change is small.

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