Lane change support device

Abstract

To provide a lane change support device capable of preferably exploring a space of a target lane for change by controlling speed of one's own vehicle depending on traveling conditions of the vehicle, such as the urgency of lane change.SOLUTION: Provided is a lane change support device configured to estimate a speed Vad of another vehicle traveling in a target lane for change, determine a minimum length of a space that is needed for the target lane for change on the basis of the other vehicle's speed, estimate an actual length of the space of the target lane for change, and determine whether or not to change to the target lane on the basis of the minimum length and the actual length. When it is determined that the lane change is not possible, a target relative speed of the own vehicle to the other vehicle is calculated based on an allowable acceleration / deceleration for the own vehicle set on the basis of the traveling state of the own vehicle, and while the speed of the own vehicle is controlled so as for the relative speed to be a target relative speed, the space that is needed for the target lane for change is explored.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a lane change assistant for vehicles such as automobiles. [Background technology]

[0002] One known lane change assistance device is one that determines whether or not the vehicle can change lanes, and if the vehicle cannot change lanes, controls the vehicle speed to search for space for a lane change in the lane to which the vehicle is to change lanes.

[0003] For example, the following Patent Document 1 describes a lane change assist device that determines whether or not a lane change of the vehicle is permitted, and when the lane change is not permitted, accelerates or decelerates the vehicle according to the speed of another vehicle traveling in the lane to which the vehicle is to change lanes, thereby determining whether or not the vehicle can change lanes. This type of lane change assist device can more efficiently determine whether or not a lane change is permitted, compared to when the vehicle is not accelerated or decelerated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-149119 Summary of the Invention

[0005] [Problem to be solved by the invention] However, in conventional lane change assistance devices such as the device described in Patent Document 1, the vehicle is accelerated or decelerated only in accordance with the speed of other vehicles traveling in the lane to which the lane is to be changed, without taking into consideration the urgency of the lane change, etc. Therefore, it is not possible to preferably search for a space for changing lanes while controlling the speed of the vehicle in accordance with the traveling conditions of the vehicle, such as the urgency of the lane change.

[0006] The present invention provides an improved lane change assistance device that can preferably search for space for changing lanes by controlling the speed of the vehicle in accordance with the driving conditions of the vehicle, such as the urgency of changing lanes. [Means for solving the problems and effects of the invention]

[0007] According to the present invention, there is provided a lane change assistance device (100) including a target information acquisition device (18) that acquires information on targets around the vehicle (102), and a control unit (driving assistance ECU 10) configured to estimate a vehicle speed (Vad) of another vehicle (112, 114) traveling in a lane (110) to which the vehicle is to change lanes based on the information acquired by the target information acquisition device, determine a minimum length (Lsre) of a space in the lane to which the vehicle is to change lanes based on the estimated vehicle speed of the other vehicle (S10), estimate an actual length (Ls) of a space in the lane to which the vehicle is to change lanes based on the information acquired by the target information acquisition device, and determine whether or not the vehicle is to change lanes to the lane to which the vehicle is to change lanes based on the minimum length and the actual length (S20).

[0008] When it is not possible to determine whether or not the lane change is possible (S20), the control unit (driving assistance ECU10) is configured to set the permissible acceleration / deceleration (Gxma) of the host vehicle based on the driving conditions of the host vehicle (S30), calculate a target relative speed (Vrma) of the host vehicle with respect to the other vehicle based on the permissible acceleration / deceleration (S40), and search for space in the lane to which the host vehicle is to change lanes, which is necessary for the host vehicle to change lanes, while controlling the speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed (S80, S100, S130, S150).

[0009] According to the above configuration, when the possibility determination is impossible, the allowable acceleration / deceleration of the host vehicle is set based on the traveling situation of the host vehicle, and the target relative speed of the host vehicle with respect to the other vehicle is calculated based on the allowable acceleration / deceleration. Furthermore, while controlling the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed, a space in the lane to which the host vehicle is to change lanes, which is necessary for the host vehicle to change lanes, is searched for.

[0010] Therefore, the vehicle speed of the host vehicle can be controlled so that the relative speed of the host vehicle to other vehicles traveling in the lane to which the host vehicle is to change lanes becomes the target relative speed calculated according to the traveling conditions of the host vehicle. Therefore, compared to a case in which the host vehicle is accelerated or decelerated according to only the speed of other vehicles and a space is searched for, it is possible to preferably search for a space in the lane to which the host vehicle is to change lanes. [Mode of the invention]

[0011] In one aspect of the present invention, when the vehicle speed (Vo) of the host vehicle is greater than the vehicle speed (Vad) of the other vehicle (S50) and the vehicle speed of the host vehicle is equal to or less than the sum of the vehicle speed of the other vehicle and the target relative speed (Vad+Vrma) (S60), the control unit (driving assistance ECU 10) is configured to search for a space of equal to or greater than the minimum length in the lane to which the lane is to be changed (S80), while controlling the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed.

[0012] In another aspect of the present invention, when the speed of the host vehicle is greater than the speed of the other vehicle (S50) and greater than the sum of the speed of the other vehicle and the target relative speed (Vad+Vrma) (S60), the control unit (driving assistance ECU10) is configured to determine an achievable relative speed (Vrmaa) of the host vehicle relative to the other vehicle, determine a modified minimum length (Lsrea) of a space in which the host vehicle can change lanes based on the achievable relative speed (S90), and search for a space of equal to or greater than the modified minimum length in the lane to which the lane is to be changed lanes while controlling the speed of the host vehicle so that the relative speed of the host vehicle relative to the other vehicle becomes the achievable target relative speed (-Vrmaa) (S100).

[0013] Furthermore, in another aspect of the present invention, when the speed of the host vehicle is equal to or less than the speed of the other vehicle (S50) and is equal to or greater than the difference (Vad-Vrma) between the speed of the other vehicle and the target relative speed (S110), the control unit (driving assistance ECU10) is configured to search for a space of equal to or greater than the minimum length in the lane to which the lane is to be changed (S130), while controlling the speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed.

[0014] Furthermore, in another aspect of the present invention, when the speed of the host vehicle is equal to or lower than the speed of the other vehicle (S50) and is smaller than the difference (Vad-Vrma) between the speed of the other vehicle and the target relative speed (S110), the control unit (driving assistance ECU10) is configured to determine an achievable relative speed (Vrmaa) of the host vehicle relative to the other vehicle, determine a modified minimum length (Lsrea) of a space in which the host vehicle can change lanes based on the achievable relative speed (S140), and search for a space of equal to or greater than the modified minimum length in the lane to which the lane is to be changed lanes while controlling the speed of the host vehicle so that the relative speed of the host vehicle relative to the other vehicle becomes the achievable target relative speed (Vrmaa) (S150).

[0015] In the above description, other objects, other features and attendant advantages of the present invention will be easily understood from the following description of the embodiments of the present invention which will be described with reference to the drawings. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic configuration diagram showing a lane change assistance device according to an embodiment; [Diagram 2] 5 is a flowchart corresponding to a lane change assist control program in the embodiment. [Diagram 3] FIG. 13 is a diagram showing a map for calculating a reference length Lsre as a minimum length of space in the lane of the lane change destination required for the host vehicle to change lanes, based on a vehicle speed Vad of another vehicle in the lane change destination. [Figure 4]FIG. 13 is a diagram showing a map for calculating the magnitude Vrma of the maximum relative speed when searching for a space ahead of a lane change, based on the magnitude Gxma of the allowable acceleration / deceleration. [Diagram 5] 1 is a diagram showing a situation in which a vehicle changes lanes between a preceding vehicle and a following vehicle in a lane to which the vehicle is to change lanes, the preceding vehicle being slower than the vehicle itself; FIG. [Figure 6] 1 is a diagram showing a situation in which a vehicle changes lanes between a leading vehicle and a following vehicle in a lane to which the vehicle is to change lanes and the following vehicle is traveling faster than the vehicle; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lane change assist device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] As shown in Fig. 1, a lane change assist device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driving assist ECU 10. The vehicle 102 is an autonomous vehicle and includes a drive ECU 20, a braking ECU 30, an electric power steering ECU 40, and a meter ECU 50. ECU refers to an electronic control unit having a microcomputer as a main component. In the following description, the electric power steering is referred to as EPS.

[0019] The microcomputer of each ECU includes a CPU, ROM, RAM, a readable / writable non-volatile memory (N / M), and an interface (I / F). The CPU realizes various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are connected to each other via a Controller Area Network (CAN) 104 so that they can exchange data (communicate). Therefore, the detection values ​​of sensors (including switches) connected to a specific ECU are also sent to other ECUs.

[0020] The driving assistance ECU 10 is a central control device that performs driving assistance control such as lane change assistance control, lane keeping control, etc. In the embodiment, the driving assistance ECU 10 executes lane change assistance control of the vehicle 102 in cooperation with other ECUs, as will be described in detail later.

[0021] The driving assistance ECU 10 is connected to a camera sensor 12, a radar sensor 14, and a setting operation device 16. The camera sensor 12 and the radar sensor 14 each include a plurality of camera devices and a plurality of radar devices. The camera sensor 12 and the radar sensor 14 function as a target information acquisition device 18 that acquires target information around the vehicle 102.

[0022] Although not shown in the figure, each camera device of the camera sensor 12 includes a camera unit that captures images of the surroundings of the vehicle 102, and a recognition unit that analyzes image data captured by the camera unit to recognize targets such as white lines on the road and other vehicles. The recognition unit supplies information about the recognized targets to the driving assistance ECU 10 at predetermined time intervals.

[0023] Each radar device of the radar sensor 14 includes a radar transmission / reception unit and a signal processing unit (not shown). The radar transmission / reception unit emits millimeter-wave radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves (i.e., reflected waves) reflected by a three-dimensional object (e.g., another vehicle, a bicycle, etc.) present within the emission range. The signal processing unit supplies information indicating the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the vehicle, etc. to the driving assistance ECU 10 at predetermined time intervals based on the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the time from transmitting the millimeter waves to receiving the reflected waves. Note that a LiDAR (Light Detection And Ranging) may be used instead of or in addition to the radar sensor 14.

[0024] The setting operation device 16 is provided at a position operable by the driver, like a steering wheel (not shown in Fig. 1), and is adapted to be operated by the driver. Although not shown in Fig. 1, the setting operation device 16 includes a lane change assist switch. As will be described in detail later, the driving assistance ECU 10 starts lane change assist control when the lane change assist switch is on and a predetermined condition (described later) is satisfied.

[0025] The drive ECU 20 is connected to a drive device 22 that accelerates the vehicle 102 by applying a drive force to drive wheels 24. The drive ECU 20 normally controls the drive device 22 so that the drive force generated by the drive device 22 changes according to the driving operation by the driver, and when a command signal is received from the driving assistance ECU 10, the drive ECU 20 controls the drive device 22 based on the command signal.

[0026] A braking device 32 that applies a braking force to wheels 34 to decelerate the vehicle 102 is connected to the braking ECU 30. The braking ECU 30 normally controls the braking device so that the braking force generated by the braking device 32 changes according to the braking operation by the driver, and when it receives a command signal from the driving assistance ECU 10, it performs automatic braking by controlling the braking device 32 based on the command signal. When a braking force is applied to the wheels, a brake lamp not shown in FIG. 1 is turned on.

[0027] An EPS device 42 is connected to the EPS-ECU 40. The EPS-ECU 40 controls the EPS device 42 in a manner known in the art based on the steering torque Ts and vehicle speed Vo detected by a driving operation sensor 60 and a vehicle state sensor 70 described below, thereby controlling the steering assist torque and reducing the steering burden on the driver. The EPS-ECU 40 also controls the EPS device 42 to steer the steered wheels 44 as necessary. Thus, the EPS-ECU 40 and the EPS device 42 function as an automatic steering device that automatically steers the steered wheels as necessary.

[0028] As can be seen from the above description, the drive ECU 20, the drive device 22, the brake ECU 30, the brake device 32, the EPS·ECU 40 and the EPS device 42 function as a driving control device 90 that controls the driving of the vehicle 102, such as braking / driving and turning.

[0029] A touch panel type display 52 that displays the status of control by the driving assistance ECU 10 is connected to the meter ECU 50. The display 52 may be, for example, a multi-information display that displays meters and various information, or may be a display of a navigation device 80 described later. As described later, when the display 52 receives a signal from the driving assistance ECU 10, it displays the status of lane change assistance control.

[0030] The driving operation sensor 60 and the vehicle condition sensor 70 are connected to the CAN 104. Information detected by the driving operation sensor 60 and the vehicle condition sensor 70 (called sensor information) is transmitted to the CAN 104. The sensor information transmitted to the CAN 104 can be used appropriately in each ECU. Note that the sensor information may be information of a sensor connected to a specific ECU and transmitted to the CAN 104 from the specific ECU.

[0031] The driving operation sensor 60 includes a driving operation amount sensor that detects the operation amount of an accelerator pedal, a braking operation amount sensor that detects the master cylinder pressure or the depression force on a brake pedal, etc. The driving operation sensor 60 also includes a steering angle sensor that detects a steering angle θ, a steering torque sensor that detects a steering torque Ts, etc. The driving operation sensor 60 also includes a turn lever that is operated when the driver wishes to change lanes, and a mode switch that switches the driving mode of the vehicle 102 between a sports mode and a comfort mode. The sports mode is a mode that prioritizes the steering response of the vehicle over the ride comfort, and the comfort mode is a mode that prioritizes the ride comfort over the ride response of the vehicle.

[0032] The vehicle condition sensor 70 includes a vehicle speed sensor that detects the vehicle speed Vo of the vehicle 102, a longitudinal acceleration sensor that detects the longitudinal acceleration of the vehicle, a lateral acceleration sensor that detects the lateral acceleration of the vehicle, and a yaw rate sensor that detects the yaw rate of the vehicle.

[0033] Furthermore, the navigation device 80 is also connected to the CAN 104. The navigation device 80 includes a GPS receiver for detecting the position of the vehicle 102, a storage device for storing map information and road information, and a communication device for acquiring the latest map information and road information from the outside. The navigation device 80 functions as a device for acquiring information on the current location of the vehicle 102, and outputs a signal indicating the current location of the vehicle on the map to the driving assistance ECU 10. Furthermore, when a destination is input, the navigation device 80 determines a target route from the current location of the vehicle 102 to the destination, and guides the vehicle to travel along the target route. In particular, when there is a branch point ahead of the vehicle and a lane change is required before the branch point in order for the vehicle to travel along the target route, the navigation device 80 notifies the driver that a lane change is required on the display 52 and notifies the driving assistance ECU 10.

[0034] In this embodiment, the ROM of the driving assistance ECU 10 stores a lane change assist control program corresponding to the flowchart shown in Fig. 2. The CPU of the driving assistance ECU 10 performs lane change assist by executing lane change assist control in accordance with this program. <Lane Change Assist Control (Fig. 2)>

[0035] Next, a lane change assist control program in the embodiment will be described with reference to the flowchart shown in Fig. 2. The lane change assist control according to the flowchart shown in Fig. 2 is started by the CPU of the driving assist ECU 10 when the turn lever is operated or a signal indicating that a lane change is required is input from the navigation device 80 while the lane change assist switch is on, and is repeatedly executed at predetermined time intervals.

[0036] First, in step S10, the CPU estimates the vehicle speed Vad of the other vehicle based on the change in the positional relationship between the other vehicle at the lane change destination and the host vehicle 102 acquired by the target information acquisition device 18 and the vehicle speed Vo of the host vehicle. Furthermore, based on the vehicle speed Vad of the other vehicle, the CPU calculates a reference length Lsre as the minimum length of space in the lane at the lane change destination required for the host vehicle to change lanes, from the map shown in Fig. 3. As shown in Fig. 3, the reference length Lsre is calculated so as to be larger as the vehicle speed Vad of the other vehicle is larger.

[0037] 5 and 6 show a situation in which the vehicle changes lanes between a leading vehicle 112 and a following vehicle 114 traveling in a destination lane 110, respectively, when the leading vehicle 112 and the following vehicle 114 are slower and faster than the vehicle 102. In particular, (A) shows the situation before the lane change, and (B) shows the situation after the lane change.

[0038] If there is a large space in the lane to which the lane is to be changed, searching for the space is not necessary. However, if the space in the lane to which the lane is to be changed is small, searching for the space is necessary, and the lane is changed so as to secure the minimum inter-vehicle distance Lmin between the vehicle 102 and the preceding vehicle 110 and between the vehicle 102 and the following vehicle 112 when the lane change is completed.

[0039] As can be seen from (B), if the length of the vehicle 102 is Lv, the vehicle cannot change lanes unless there is a space of 2Lmin+Lv or more in the lane to which the vehicle is to change lanes. Therefore, the reference length Lsre may be 2Lmin+Lv. As shown in Fig. 3, the reference length Lsre is calculated so that it increases as the vehicle speed Vad of the other vehicle increases. Note that, when a leading vehicle 112 and a following vehicle 114 are present in the lane 110 to which the vehicle is to change lanes and have different vehicle speeds, the vehicle speed Vad may be the average value of the vehicle speeds of the two vehicles.

[0040] In step S20, the CPU estimates the length Ls of the space in the lane of the lane change destination in an area where the vehicle 102 may be able to change lanes, based on the information of the lane change destination acquired by the target information acquisition device 18. Furthermore, the CPU determines whether or not the space length Ls is equal to or greater than the reference length Lsre, that is, whether or not the lane change is possible without searching for a space. If the CPU makes a positive determination, it advances this control to step S170, and if the CPU makes a negative determination, it advances this control to step S30.

[0041] In step S30, the CPU sets the magnitude Gxma of the allowable acceleration / deceleration of the host vehicle, i.e., the maximum value of the magnitude of the longitudinal acceleration / deceleration allowed for the host vehicle, based on the traveling conditions of the host vehicle. In the embodiment, the traveling conditions of the host vehicle are at least one of the distance Ld (see Figs. 5 and 6) from the current position of the host vehicle 102 to the branch point Pbp, the traveling mode of the host vehicle, and the type of lane change request. The magnitude Gxma of the allowable acceleration / deceleration is set to a larger value as the distance Ld is smaller, and is set to a larger value when the traveling mode is the sports mode compared to when the traveling mode is the comfort mode. Furthermore, the magnitude Gxma of the allowable acceleration / deceleration is set to a larger value when the lane change request is a request by the driver (operation of the turn lever) compared to when the lane change request is a request by the navigation device 80 (a request for control).

[0042] In step S40, the CPU calculates the magnitude Vrma of the maximum relative speed when searching for a space at the lane change destination based on the magnitude Gxma of the allowable acceleration / deceleration, using the map shown in Fig. 4. The magnitude Vrma of the maximum relative speed is the maximum value of the magnitude of the relative speed Vr (=Vo-Vad) of the host vehicle 102 with respect to another vehicle at the lane change destination.

[0043] Next, the reason why the relationship between the magnitude of the permissible acceleration / deceleration Gxma and the magnitude of the maximum relative velocity Vrma is as shown in FIG. 4 will be described.

[0044] Assuming that the acceleration / deceleration of the host vehicle 102 is Gxo, in the situation shown in Figures 4 and 5, when the host vehicle is decelerated and accelerated, respectively, the distance Lr that the host vehicle displaces relative to the other vehicle until the vehicle speed Vo of the host vehicle becomes the vehicle speed Vad of the other vehicle is expressed by the following equation (1). Lr = Vr * Vr / (2 * Gxo) ... (1)

[0045] 5, in order to make the inter-vehicle distance between the host vehicle 102 and the preceding vehicle 112 equal to or greater than the minimum inter-vehicle distance Lmin after a lane change, it is necessary to start decelerating the host vehicle when the inter-vehicle distance between the host vehicle 102 and the preceding vehicle 112 is equal to or greater than Lmin-Lr. Also, in order to make the inter-vehicle distance between the host vehicle 102 and the following vehicle 114 equal to or greater than the minimum inter-vehicle distance Lmin after a lane change, it is necessary to start decelerating the host vehicle when the inter-vehicle distance between the host vehicle 102 and the following vehicle 114 is equal to or greater than Lmin+Lr.

[0046] In addition, when the host vehicle starts to change lanes while traveling ahead of the preceding vehicle to which the host vehicle is to change lanes, the inter-vehicle distance between the host vehicle and the preceding vehicle after the lane change may become too small. Therefore, in order to make the inter-vehicle distance between the host vehicle and the preceding vehicle after the lane change the minimum inter-vehicle distance Lmin, the inter-vehicle distance between the host vehicle and the preceding vehicle at the start of the lane change needs to be Lfront or more, and Lfront is a smaller value as the relative speed Vr is higher, and may be 0 when the host vehicle starts to move to change lanes.

[0047] If Lmin-Lr is smaller than Lfront, the distance between the vehicle and the preceding vehicle at the start of the lane change is Lfront. After the lane change is completed, the distance between the vehicle and the preceding vehicle is Lfront+Lr, which is larger than Lmin. Therefore, the vehicle cannot change lanes to a space whose length is 2Lmin+Lv.

[0048] In order for the vehicle to change lanes into a space with a length of 2Lmin+Lv, Lfront must be equal to or greater than Lmin-Lr. If Lfront is equal to Lmin-Lr, the following equation (2) is established from the above equation (1), so the relative speed Vr is expressed by the following equation (3). Lfront = Lmin-Lr = Lmin-Vr*Vr / (2*Gxo) …(2) Vr={(Lmin-Lfront)*2*Gxo} 1 / 2 …(3)

[0049] 6, in order to make the inter-vehicle distance between the host vehicle 102 and the preceding vehicle 112 equal to or greater than the minimum inter-vehicle distance Lmin after a lane change, it is necessary to start accelerating the host vehicle when the inter-vehicle distance between the host vehicle 102 and the preceding vehicle 112 is equal to or greater than Lmin+Lr. Also, in order to make the inter-vehicle distance between the host vehicle 102 and the following vehicle 114 equal to or greater than the minimum inter-vehicle distance Lmin after a lane change, it is necessary to start accelerating the host vehicle when the inter-vehicle distance between the host vehicle 102 and the following vehicle 114 is equal to or greater than Lmin-Lr.

[0050] In addition, when the host vehicle starts to change lanes while traveling behind the following vehicle ahead of the lane change destination, the inter-vehicle distance between the host vehicle and the following vehicle after the lane change may become too small. Therefore, in order to set the inter-vehicle distance between the host vehicle and the following vehicle after the lane change to the minimum inter-vehicle distance Lmin, the inter-vehicle distance between the host vehicle and the following vehicle at the start of the lane change needs to be equal to or larger than Lrear, where Lrear is a smaller value as the relative speed Vr increases and may be 0 when the host vehicle starts to move to change lanes.

[0051] If Lmin-Lr is smaller than Lrear, the distance between the vehicle and the following vehicle at the start of the lane change is Lrear. After the lane change is completed, the distance between the vehicle and the following vehicle is Lrear+Lr, which is larger than Lmin. Therefore, the vehicle cannot change lanes to a space with a length of 2Lmin+Lv.

[0052] In order for the vehicle to change lanes into a space with a length of 2Lmin+Lv, Lrear must be equal to or greater than Lmin-Lr. If Lrear is equal to Lmin-Lr, the following equation (4) is established from the above equation (1), so the relative speed Vr is expressed by the following equation (5). Lrear = Lmin-Lr = Lmin-Vr*Vr / (2*Gxo) …(4) Vr = {(Lmin-Lrear)*2*Gxo} 1 / 2 …(5)

[0053] In the above formulas (3) and (5), when Lfront and Lrear are set to 0 and Lfront and Lrear must be equal to or greater than Lmin-Lr, the following formula (6) is established. Therefore, the relationship between the magnitude of the allowable acceleration / deceleration Gxma and the magnitude of the maximum relative velocity Vrma is as shown in FIG. Vr = (Lmin * 2 * Gxo) 1 / 2 …(6)

[0054] In step S50, the CPU determines whether or not the vehicle speed Vo of the host vehicle 102 is greater than the vehicle speed Vad of the other vehicle ahead of the lane change, i.e., whether or not the host vehicle is faster than the other vehicle ahead of the lane change. If the CPU makes a negative determination, it advances this control to step S110, and if the CPU makes a positive determination, it advances this control to step S60.

[0055] In step S60, the CPU determines whether or not the vehicle speed Vo of the host vehicle 102 is greater than the sum Vad+Vrma of the vehicle speed Vad of the other vehicle about to change lanes and the magnitude of the maximum relative speed Vrma. That is, the CPU determines whether or not the relative speed Vr (=Vo-Vad) of the host vehicle 102 with respect to the other vehicle is greater than the magnitude of the maximum relative speed Vrma. If the CPU makes a negative determination, it advances this control to step S80, and if the CPU makes a positive determination, it advances this control to step S70.

[0056] In step S70, the CPU determines whether or not the host vehicle 102 can be decelerated. When the CPU determines that the host vehicle 102 is not decelerated, the CPU advances this control to step S90, and when the CPU determines that the host vehicle is not decelerated, the CPU advances this control to step S80. It may be determined that the host vehicle cannot be decelerated when the inter-vehicle distance between the host vehicle and the following vehicle in the same lane is equal to or less than the reference inter-vehicle distance for deceleration determination. In this case, the reference inter-vehicle distance for deceleration determination may be a positive constant, but may be variably set to be larger as the relative vehicle speed of the following vehicle to the host vehicle increases.

[0057] In step S80, the CPU outputs a command signal to the cruise control device 90 so that the relative speed Vr of the host vehicle 102 with respect to another vehicle in the lane ahead becomes -Vrma, and while controlling the vehicle speed of the host vehicle, searches for a space in the lane ahead of the lane ahead that has a length equal to or greater than the reference length Lsre.

[0058] In step S90, the CPU determines the magnitude Vrmad of the achievable relative speed of the host vehicle with respect to the other vehicle at the lane change destination based on the vehicle-to-vehicle distance between the host vehicle 102 and the following vehicle at the lane change destination and the relative vehicle speed of the following vehicle at the lane change destination relative to the host vehicle. The magnitude Vrmad of the relative speed is smaller than the magnitude Vrma of the maximum relative speed. The CPU also determines the correction reference length Lsred as the correction minimum length of the space in the lane at the lane change destination required for the host vehicle to change lanes based on the magnitude Vrmad of the relative speed. In this case, the correction reference length Lsred is determined so as to be larger as the magnitude Vrmad of the relative speed is larger.

[0059] In step S100, the CPU outputs a command signal to the cruise control device 90 so that the relative speed Vr of the host vehicle 102 with respect to another vehicle in the lane ahead becomes -Vrmad, and while controlling the vehicle speed of the host vehicle, searches for a space in the lane ahead of the lane ahead that has a length equal to or greater than the revised reference length Lsred.

[0060] In step S110, the CPU determines whether the vehicle speed Vo of the host vehicle 102 is smaller than the difference Vad-Vrma between the vehicle speed Vad of the other vehicle ahead of the lane change and the maximum relative speed magnitude Vrma. That is, the CPU determines whether the relative speed Vr (=Vo-Vad) of the host vehicle 102 with respect to the other vehicle is smaller than the sign-inverted value -Vrma of the maximum relative speed magnitude Vrma. If the CPU makes a negative determination, it advances this control to step S130, and if the CPU makes a positive determination, it advances this control to step S120.

[0061] In step S120, the CPU determines whether or not the host vehicle 102 can be accelerated. If the CPU determines that the host vehicle 102 is not accelerating, the CPU advances this control to step S140. If the CPU determines that the host vehicle is not accelerating, the CPU advances this control to step S130. It may be determined that the host vehicle cannot be accelerated when the inter-vehicle distance between the host vehicle and the preceding vehicle in the same lane is equal to or less than the reference inter-vehicle distance for acceleration determination. In this case, the reference inter-vehicle distance for acceleration determination may be a positive constant, but may also be variably set to be smaller as the relative vehicle speed of the preceding vehicle with respect to the host vehicle increases.

[0062] In step S130, the CPU outputs a command signal to the cruise control device 90 so that the relative speed Vr of the host vehicle 102 with respect to another vehicle in the lane ahead becomes Vrma, and while controlling the vehicle speed of the host vehicle, searches for a space in the lane ahead of the lane ahead that has a length equal to or greater than the reference length Lsre.

[0063] In step S140, the CPU determines the magnitude Vrmaa of the achievable relative speed of the host vehicle with respect to the other vehicle at the lane change destination based on the vehicle-to-vehicle distance between the host vehicle 102 and the preceding vehicle at the lane change destination and the relative vehicle speed of the preceding vehicle at the lane change destination relative to the host vehicle. The magnitude Vrmaa of the relative speed is smaller than the magnitude Vrma of the maximum relative speed. The CPU also determines the correction reference length Lsrea as the correction minimum length of the space in the lane at the lane change destination required for the host vehicle to change lanes based on the magnitude Vrmaa of the relative speed. In this case, the correction reference length Lsrea is determined so as to be larger as the magnitude Vrmaa of the relative speed is larger.

[0064] In step S150, the CPU outputs a command signal to the cruise control device 90 so that the relative speed Vr of the host vehicle 102 with respect to another vehicle in the lane ahead becomes Vrmaa, and while controlling the vehicle speed of the host vehicle, searches for a space in the lane ahead of the lane ahead that has a length equal to or greater than the modified reference length Lsrea.

[0065] In step S160, the CPU determines whether or not a space that satisfies the length requirement is present as a result of the search in step S80, S100, S130, or S150. If the CPU determines that the space satisfies the length requirement, the CPU advances control to step S180, and if the CPU determines that the space satisfies the length requirement, the CPU advances control to step S170.

[0066] In step S170, the CPU outputs a command signal to the cruise control device 90 to cause the vehicle 102 to move to a space that satisfies the length requirement by automatic driving, thereby executing a lane change of the vehicle to the lane to be changed to. Note that the lane change by automatic driving may be executed in any manner known in the art.

[0067] In step S180, the CPU determines whether or not a reference time Δt (positive constant) or more has elapsed since the start of this control. If the CPU determines negative, it terminates this control once and returns the control to step S10, whereas if the CPU determines positive, it terminates this control without executing a lane change of the host vehicle, outputs a command signal to the meter ECU 50, and displays the end of this control on the display 52.

[0068] As can be seen from the above description, according to the embodiment, the reference length Lsre as the minimum length of the space in the lane of the lane to which the host vehicle is to change lanes is calculated so as to be larger as the vehicle speed Vad of the other vehicle in the lane to which the host vehicle is to change lanes is larger (S10). The length Ls of the space in the lane of the lane to which the host vehicle 102 is to change lanes is estimated in an area where the host vehicle 102 may be able to change lanes, and it is determined whether the lane change is possible without searching for a space by determining whether the length Ls of the space is equal to or larger than the reference length Lsre (S20).

[0069] When the length Ls of the space is less than the reference length Lsre, the magnitude of the allowable acceleration / deceleration Gxma of the host vehicle, i.e., the maximum value of the magnitude of the longitudinal acceleration / deceleration allowed for the host vehicle, is set based on the traveling conditions of the host vehicle (S30). Furthermore, the magnitude Vrma of the maximum relative speed when searching for a space to change lanes is calculated based on the magnitude Gxma of the allowable acceleration / deceleration from the map shown in Fig. 4 (S40).

[0070] Furthermore, the cruise control device 90 is controlled to accelerate or decelerate the host vehicle so that the relative speed of the host vehicle to the other vehicle becomes the target relative speed, while searching for a space of a minimum length or more in the lane to which the lane is to be changed (S80, S130).

[0071] The magnitude Gxma of the allowable acceleration / deceleration is set to a larger value as the distance Ld from the current position of the vehicle 102 to the branch point Pbp is smaller, and is set to a larger value when the driving mode is the sports mode compared to when the driving mode is the comfort mode. Furthermore, the magnitude Gxma of the allowable acceleration / deceleration is set to a larger value when the lane change request is a driver's request (operation of the turn lever) compared to when the lane change request is a request from the navigation device 80 (request for vehicle driving control).

[0072] Therefore, the vehicle speed Vo of the host vehicle can be controlled so that the relative speed Vr (=Vo-Vad) of the host vehicle with respect to another vehicle traveling in the lane to which the host vehicle is to change lanes becomes the target relative speed Vrma calculated according to the traveling conditions of the host vehicle, such as the distance Ld from the current position of the host vehicle to the branch point. Therefore, a space in the lane to which the host vehicle is to change lanes, which is necessary for the host vehicle to change lanes, can be preferably searched for, compared with a case in which the host vehicle is accelerated or decelerated and a space is searched for according only to the speed of the other vehicle, regardless of the traveling conditions of the host vehicle.

[0073] In particular, when the vehicle speed Vo of the host vehicle 102 is greater than the vehicle speed Vad of the other vehicle at the lane change destination (S50) and the vehicle speed of the host vehicle is equal to or less than the sum (Vrma+Vrma) of the vehicle speed of the other vehicle and the target relative speed (S60), the cruise control device 90 is controlled to control the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed, while searching for a space of equal to or greater than the minimum length Lsre in the lane at the lane change destination (S80). Thus, a space of equal to or greater than the minimum length can be searched for while controlling the vehicle speed of the host vehicle so that the relative speed becomes the target relative speed.

[0074] On the other hand, when the vehicle speed Vo of the host vehicle 102 is higher than the vehicle speed Vad of the other vehicle (S50), but the vehicle speed of the host vehicle is higher than the sum of the vehicle speed of the other vehicle and the target relative speed (S60), and the host vehicle cannot be decelerated (S70), a realizable relative speed Vrmad of the host vehicle with respect to the other vehicle is determined (S90). In addition, a corrected minimum length Lsred of a space in which the host vehicle can change lanes is determined based on the realizable relative speed (S90). Furthermore, a space in the lane to which the lane is to be changed is searched for that is equal to or longer than the corrected minimum length Lsred, while controlling the vehicle speed of the host vehicle by controlling the cruise control device so that the relative speed of the host vehicle with respect to the other vehicle becomes the realizable target relative speed (-Vrmad). Thus, a space that is equal to or longer than the corrected minimum length can be searched for while controlling the vehicle speed of the host vehicle so that the relative speed becomes the realizable target relative speed.

[0075] Furthermore, when the vehicle speed Vo of the host vehicle 102 is equal to or lower than the vehicle speed Vad of the other vehicle (S50) and is equal to or higher than the difference (Vad-Vrma) between the vehicle speed of the other vehicle and the target relative speed (S110), the cruise control device 90 is controlled to control the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed, while searching for a space of equal to or higher than the minimum length Lsre in the lane to which the lane is to be changed (S130). Thus, a space of equal to or higher than the minimum length can be searched for while controlling the vehicle speed of the host vehicle so that the relative speed becomes the target relative speed.

[0076] On the other hand, when the vehicle speed Vo of the host vehicle 102 is equal to or lower than the vehicle speed Vad of the other vehicle (S50), but the vehicle speed of the host vehicle is less than the difference (Vad-Vrma) between the vehicle speed of the other vehicle and the target relative speed (S110), and the host vehicle cannot accelerate (S120), a realizable relative speed Vrmaa of the host vehicle with respect to the other vehicle is determined (S140), and a corrected minimum length Lsrea of ​​a space in which the host vehicle can change lanes is determined based on the realizable relative speed (S140). Furthermore, a space in the lane to which the lane is to be changed is searched for that is equal to or higher than the corrected minimum length Lsrea, while controlling the vehicle speed of the host vehicle by controlling the cruise control device so that the relative speed of the host vehicle with respect to the other vehicle becomes the realizable target relative speed Vrmaa (S150). Thus, a space that is equal to or higher than the corrected minimum length can be searched for while controlling the vehicle speed of the host vehicle so that the relative speed becomes the realizable target relative speed.

[0077] Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various other embodiments are possible within the scope of the present invention.

[0078] For example, in the above embodiment, in step S10, the reference length Lsre is calculated to be larger as the vehicle speed Vad of the other vehicle about to change lanes is larger, but the reference length Lsre may be a fixed value.

[0079] In the above embodiment, in step S30, the magnitude Gxma of the allowable acceleration / deceleration of the host vehicle is set based on the traveling conditions of the host vehicle, and the traveling conditions of the host vehicle are the distance Ld from the current position of the host vehicle 102 to the branch point, the traveling mode of the host vehicle, and the type of lane change request. However, any of the distance Ld, the traveling mode of the host vehicle, and the type of lane change request may be omitted.

[0080] Furthermore, in the above embodiment, in steps S70 and S120, it is determined whether or not the host vehicle 102 can be decelerated and accelerated, respectively. However, these steps may be omitted. [Explanation of symbols]

[0081] 10... driving assistance ECU, 12... camera sensor, 14... radar sensor, 18... target information acquisition device, 22... drive device, 32... braking device, 42... EPS device, 90... driving control device, 100... lane change assistance device, 102... vehicle, 112... preceding vehicle, 114... following vehicle

Claims

1. 1. A lane change assist device including: a target information acquisition device that acquires information on targets around a vehicle; and a control unit configured to estimate a vehicle speed of another vehicle traveling in a lane to which the vehicle is to change lanes based on the information acquired by the target information acquisition device, determine a minimum length of a space in the lane to which the vehicle is to change lanes based on the estimated vehicle speed of the other vehicle, estimate an actual length of a space in the lane to which the vehicle is to change lanes based on the information acquired by the target information acquisition device, and determine whether or not the vehicle is to change lanes to the lane to which the vehicle is to change lanes based on the minimum length and the actual length, the control unit, when the possibility determination is impossible, sets an allowable acceleration / deceleration of the host vehicle based on a traveling state of the host vehicle, calculates a target relative speed of the host vehicle with respect to the other vehicle based on the allowable acceleration / deceleration, and searches for a space in the lane of the lane change destination that is necessary for the host vehicle to change lanes while controlling a vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed.

2. 2. The lane change assistance device according to claim 1, wherein the control unit is configured to, when the vehicle speed of the host vehicle is greater than the vehicle speed of the other vehicle and is equal to or less than the sum of the vehicle speed of the other vehicle and the target relative speed, search for a space of equal to or greater than the minimum length in the lane to which the lane is to be changed, while controlling the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed.

3. 2. The lane change assistance device according to claim 1, wherein the control unit is configured to, when a vehicle speed of the host vehicle is greater than a vehicle speed of the other vehicle and is greater than a sum of the vehicle speed of the other vehicle and the target relative speed, determine a achievable relative speed of the host vehicle with respect to the other vehicle, determine a corrected minimum length of a space in which the host vehicle can change lanes based on the achievable relative speed, and search for a space in the lane to which the lane is to be changed that is greater than or equal to the corrected minimum length while controlling the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the achievable target relative speed.

4. 2. The lane change assistance device according to claim 1, wherein the control unit is configured to search for a space having a length equal to or greater than the minimum length in the lane to which the lane is to be changed, while controlling the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the target relative speed when the vehicle speed of the host vehicle is equal to or less than the vehicle speed of the other vehicle and is equal to or greater than the difference between the vehicle speed of the other vehicle and the target relative speed.

5. 2. The lane change assistance device according to claim 1, wherein the control unit is configured to, when a vehicle speed of the host vehicle is equal to or lower than a vehicle speed of the other vehicle and is smaller than a difference between the vehicle speed of the other vehicle and the target relative speed, determine a achievable relative speed of the host vehicle with respect to the other vehicle, determine a corrected minimum length of a space in which the host vehicle can change lanes based on the achievable relative speed, and search for a space in the lane to which the lane is to be changed that is equal to or greater than the corrected minimum length while controlling the vehicle speed of the host vehicle so that the relative speed of the host vehicle with respect to the other vehicle becomes the achievable target relative speed.

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