Vehicle control device, vehicle control method and program

Abstract

To provide a vehicle control device that is able to reduce a possibility that a driver has a sense of incongruity due to an increase in time taken for an amount of control to coincide with a target amount of control and is able to reduce a possibility that a vehicle collides with other object when steering control is stopped.SOLUTION: A vehicle control device executes steering control for making an amount of control in a lateral direction of a vehicle coincide with a target amount of control acquired based on a peripheral environment of the vehicle. If it is assumed that the steering control is stopped when the steering control is being executed, the vehicle control device sets an upper limit value of the target amount of control to a larger value as a stop-period collision risk that the vehicle will collide with an object is lower, and executes the steering control such that the amount of control does not become larger than the upper limit value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device that performs steering control to match a lateral control amount of a vehicle with a target control amount obtained based on the vehicle's surrounding environment, a vehicle control method in which a computer mounted on a vehicle performs steering control, and a program that causes a computer mounted on a vehicle to perform steering control. [Background technology]

[0002] BACKGROUND ART Conventionally, vehicle control devices that perform steering control such as Lane Tracing Assist (LTA), Advanced Drive Traffic Jam Assist (ADTJA), and Lane Change Assist (LCA) have been known.

[0003] For example, a vehicle control device described in Patent Document 1 (hereinafter referred to as the "conventional device") controls the steering angle so that the magnitude of the steering angle does not exceed a first steering angle guard value and the magnitude of the steering angular velocity does not exceed a first steering angular velocity guard value when a specific recognition situation does not occur during LTA execution. A specific recognition situation is a situation in which only one of the left and right lane markings of a driving lane is recognized, and the recognized lane marking changes between the left and right lane markings. When a specific recognition situation occurs, the position of the target driving line changes significantly, which could result in unstable vehicle behavior. Therefore, when a specific recognition situation occurs, the conventional device controls the steering angle so that the magnitude of the steering angle does not exceed a "second steering angle guard value smaller than the first steering angle guard value" and the magnitude of the steering angular velocity does not exceed a "second steering angular velocity guard value smaller than the first steering angular velocity guard value." This reduces the possibility of unstable vehicle behavior due to a significant change in the position of the target driving line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-14369 Summary of the Invention

[0005] If steering control is stopped for some reason, the risk of the vehicle colliding with an object increases compared to when steering control is not stopped. This collision risk due to the stoppage of steering control is called the "stoppage collision risk." This stoppage collision risk is not constant, but changes depending on the external environment of the vehicle, the vehicle's driving state, the driver's state, etc.

[0006] Conventional devices do not set upper limits (steering angle guard value and steering angular velocity guard value) for the control amount (steering angle) of steering control taking into account the risk of a collision when stopping. Here, it is assumed that the upper limit is set to a constant value on the premise that the risk of a collision when stopping is constant. If this upper limit is set to a low value, it will take a long time for the control amount to match the target control amount. This may cause the driver to feel uncomfortable with the steering control. On the other hand, if the upper limit is set to a high value, it will increase the possibility that the vehicle VA will collide with another object when the steering control is stopped.

[0007] The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to provide a vehicle control device that can reduce the possibility of the driver feeling uncomfortable due to the long time it takes for the control amount to match the target control amount, and can reduce the possibility of the vehicle colliding with another object when steering control is stopped.

[0008] The driving assistance device of the present invention (hereinafter referred to as "the device of the present invention") A vehicle control device (10) that performs steering control to make a lateral control amount (C) of a vehicle coincide with a target control amount acquired based on a surrounding environment of the vehicle, The vehicle control device includes: When the steering control is being performed, the upper limit value (Clmt) of the target control amount is set to a larger value as the stop collision risk (step 205) of the vehicle colliding with an object when the steering control is assumed to be stopped is lower (step 210); The steering control is executed so that the control amount does not exceed the upper limit value (steps 220 to 230). It is structured as follows.

[0009] According to the device of the present invention, the lower the risk of a collision when stopping, the larger the upper limit value is set, and steering control is performed so that the control amount does not exceed the upper limit value. This reduces the possibility that it will take a long time for the control amount to match the target control amount, and also reduces the possibility that the vehicle will collide with another object even if steering control is stopped. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a driving assistance device according to an embodiment of the present invention; [Figure 2] 4 is a flowchart illustrating an operation of the driving assistance device according to the embodiment of the present invention. [Figure 3] 10A and 10B are explanatory diagrams of time-series changes in steering torque when the LTA is stopped and a predicted course when the LTA is stopped. DETAILED DESCRIPTION OF THE INVENTION

[0011] As shown in FIG. 1, a vehicle control device according to this embodiment (hereinafter referred to as "the device 10") is applied to a vehicle VA, and includes the components shown in FIG.

[0012] The vehicle control ECU 20 executes steering control to control the steering motor 40, which will be described later, so that the control amount C in the lateral direction (vehicle width direction) of the vehicle VA coincides with a "target control amount Ctgt obtained based on the surrounding environment of the vehicle VA." Hereinafter, the vehicle control ECU 20 will be referred to as "ECU 20."

[0013] In this specification, an "ECU" is an electronic control device that includes a microcomputer as its main component. The ECU is also called a control unit, a controller, or a computer. The microcomputer includes a CPU (processor), a ROM, a RAM, an interface (I / F), and the like. At least one function of the ECU 20 may be realized by multiple ECUs.

[0014] The front camera 22 acquires image data by capturing images of the scenery ahead of the vehicle VA. The front camera 22 acquires boundary information and object information based on the image data. The boundary information is information relating to the position, relative to the vehicle VA, of the boundary that separates the current driving area in which the vehicle VA is currently traveling and the adjacent driving area adjacent to the current driving area. The object information is information relating to the position, relative to the vehicle VA, of an object that exists ahead of the vehicle VA. The front camera 22 transmits the boundary information and object information to the ECU 20.

[0015] The navigation device 24 has a GNSS (Global Navigation Satellite System) receiver 24a and a storage device 24b. The GNSS receiver 24a receives GNSS signals from multiple satellites. The GNSS signals are signals for identifying the "latitude and longitude" that represent the current position of the vehicle VA. The map information includes information on road types. Road types include expressways, general national roads, general prefectural roads, etc.

[0016] The navigation device 24 identifies the current position of the vehicle VA based on the GNSS signal, and identifies the type of road corresponding to the current position of the vehicle VA based on map information. The navigation device 24 transmits road type information relating to the identified type of road to the ECU 20.

[0017] The vehicle speed sensor 26 detects the vehicle speed Vs, which indicates the speed of the vehicle VA. The yaw rate sensor 28 detects the yaw rate Yr of the vehicle VA. The acceleration sensor 30 detects the longitudinal acceleration Gx of the vehicle VA and the lateral acceleration Gy of the vehicle VA (vehicle width direction). The acceleration Gy is also referred to as the lateral acceleration Gy. The steering angle sensor 32 detects the steering angle θ of the steered wheels of the vehicle VA. The steering torque sensor 34 detects the steering torque Tr, which indicates the torque acting on a steering shaft (not shown) connected to a steering wheel (not shown) of the vehicle VA. The steering torque sensor 34 detects the steering torque Tr, which turns the vehicle VA right, as a positive value, and the steering torque Tr, which turns the vehicle VA left, as a negative value. The contact sensor 36 detects the driver's contact with the steering wheel.

[0018] The steering motor 40 is incorporated into a steering mechanism 42. The steering mechanism 42 is a mechanism for steering the steered wheels in response to the operation of the steering wheel. In response to a command from the ECU 20, the steering motor 40 generates an assist torque in the steering mechanism 42 to assist the operation of the steering wheel, and generates an automatic steering torque in the steering mechanism 42 to change the steering angle of the steered wheels.

[0019] The display device 44 displays a presentation screen for presenting to the driver whether the upper limit control amount (upper limit value) Clmt of the control amount C is high or low.

[0020] (Activated) The operation of the ECU 20 of the device 10 will be described with reference to the flowchart shown in FIG.

[0021] When the CPU of the ECU 20 (hereinafter, when written as "CPU", unless otherwise specified, it refers to the CPU of the ECU 20) is executing steering control, it executes the routine shown in Fig. 2 every time a predetermined time has elapsed. When an appropriate time arrives, the CPU starts processing from step 200 in Fig. 2 and executes steps 205 to 220 in order.

[0022] Step 205: The CPU acquires a risk index value In that indicates the risk of the vehicle VA colliding with another object if steering control is stopped for some reason (hereinafter referred to as "stop collision risk"). The higher the stop collision risk, the larger the risk index value In. A specific example of acquiring the risk index value In will be described later.

[0023] Step 210: The CPU obtains the upper limit control amount Clmt based on the risk index value In. In particular, the CPU sets the upper limit control amount Clmt to a larger value as the risk index value In becomes smaller (i.e., as the stop collision risk becomes lower).

[0024] Step 215: The CPU acquires the target control amount Ctgt based on information representing the surrounding environment of the vehicle VA. The information representing the surrounding environment includes at least white line information.

[0025] Step 220: The CPU determines whether the target control amount Ctgt is greater than the upper limit control amount Clmt.

[0026] If the target control amount Ctgt is greater than the upper limit control amount Clmt, the CPU determines "Yes" in step 220 and executes steps 225 and 230. Step 225: The CPU sets the target controlled variable Ctgt to a value corresponding to the upper limit controlled variable Clmt. Step 230: The CPU controls the steering motor 40 so that the control amount C coincides with the target control amount Ctgt. Thereafter, the CPU proceeds to step 295 and temporarily ends this routine.

[0027] On the other hand, if the target control amount Ctgt is equal to or less than the upper limit control amount Clmt, the CPU determines "No" in step 220 and proceeds to step 230. Thereafter, the CPU proceeds to step 295 and temporarily ends this routine.

[0028] As described above, according to the present device 10, the lower the risk of a collision when stopping, the larger the value set for the upper limit control amount Clmt. Therefore, when the risk of a collision when stopping is low, it is possible to reduce the possibility that it will take a long time for the control amount to match the target control amount, and when the risk of a collision when stopping is high, it is possible to reduce the possibility that the vehicle will collide with another object even if steering control is stopped.

[0029] (Steering control) Examples of steering control to which this embodiment can be applied include lane keeping control and lane change assist control.

[0030] <Lane Keeping Control> Lane keeping control is a control that changes the lateral position of the vehicle VA so that the lateral position of the vehicle VA is maintained near the center (predetermined position) of the "own driving area (own lane) in which the vehicle VA is traveling." Lane keeping control includes first lane keeping control and second lane keeping control.

[0031] The first lane keeping control is a control that requires the driver to hold the steering wheel. An example of the first lane keeping control is LTA. Details of the first lane keeping control are described in JP 2019-14369 A. The second lane keeping control is a control that does not require the driver to hold the steering wheel when the vehicle speed Vs is equal to or lower than the upper limit vehicle speed Vlmt. An example of the second lane keeping control is the ADTJA. However, with the second lane keeping control, the driver must hold the steering wheel when the vehicle speed Vs becomes higher than the upper limit vehicle speed Vlmt.

[0032] <Lane change assist control> Lane change assist control is a control that assists at least a part of the driver's steering operation to change lanes from the current driving area (current lane) to an adjacent driving area (adjacent lane) adjacent to the current driving area (current lane). Lane change assist control is sometimes referred to as LCA. Details of lane change assist control are described in JP 2018-103769 A.

[0033] In both lane keeping control and lane change assist control, the ECU 20 obtains the target steering angle θtgt based on image data and controls the steering motor 40 so that an automatic steering torque Tr is generated in the steering mechanism 42 to match the steering angle θ with the target steering angle θtgt.

[0034] (Risk of collision when stopping) The CPU acquires a risk index value In representing the risk of a collision when stopping based on at least one of the following (1) to (5). (1) The closest approach distance Dmin when the vehicle VA traveling along the "predicted course PR when steering control is stopped" comes closest to the object (2) The driver's grip on the steering wheel (3) The type of road on which the vehicle VA is currently traveling (4) The number of pedestrians and / or bicycles present within a specified range in front of the vehicle VA. (5)Vehicle speed Vs

[0035] <(1) Closest distance Dmin> In the example shown in FIG. 3, the process of acquiring the closest approach distance Dmin when LTA (first lane keeping control) is being executed as steering control will be described.

[0036] In the example shown in Figure 3, it is assumed that the LTA being executed stops for some reason at time t1 while the vehicle VA is traveling around a curve. For the following reasons 1 and 2, the steering torque Tr becomes "0" at time t1. Reason 1: Because the LTA is being executed immediately before time t1, the steering motor 40 causes the steering mechanism 42 to generate a steering torque (automatic steering torque) Tr for matching the steering angle θ with the target steering angle θtgt of the LTA. However, because the LTA stops at time t1, the automatic steering torque Tr becomes "0." Reason 2: During the execution of LTA, the driver is simply gripping the steering wheel but is not performing any steering operation (that is, the driver is not generating steering torque Tr).

[0037] The CPU estimates the future steering angle θft based on the current steering angle θ, assuming that the following assumptions 1 and 2 are true. Assumption 1: At time t2, when a predetermined time Ttd has elapsed from time t1, the driver starts steering. Assumption 2: After time t2, the driver performs a steering operation so that the steering torque Tr increases at a constant rate (see the dashed dotted line in the graph of FIG. 3).

[0038] The CPU estimates a predicted path PR of the vehicle VA after the LTA stops based on the future steering angle θft, the current vehicle speed Vs, and the current yaw rate Yr. The CPU acquires the closest approach distance Dmin (more specifically, the distance in the vehicle width direction of the vehicle VA) when the vehicle VA traveling along the predicted path PR comes closest to an object (the guardrail GR on the left side of the vehicle VA in the example shown in FIG. 3).

[0039] The shorter the closest distance Dmin, the higher the risk of a collision when stopping. The CPU acquires the reciprocal of the closest distance Dmin as the risk index value In. Therefore, the larger the risk index value In, the higher the risk of a collision when stopping.

[0040] The change in steering torque Tr when the steering motor 40 is unable to generate assist torque for some reason when LTA is not being executed is shown by the dotted line in the upper graph of Figure 3. The predicted path PR' in this case is shown by the dotted line in the lower graph of Figure 3.

[0041] When LTA is not being performed, the driver generates a predetermined steering torque Tr before time t1, which is different from when LTA is being performed. This difference in steering torque Tr is the difference between the predicted path Pr and the predicted path Pr'.

[0042] <(2) Gripping state> Based on the detection value from the contact sensor 36, the CPU determines whether the driver is gripping the steering wheel in a non-grip state, a one-hand grip state, or a non-grip state.

[0043] The non-grip state is a state in which the driver is not gripping the steering wheel, and the response time from when steering control stops until the driver starts steering is the longest. Therefore, the non-grip state is the state in which the risk of a collision when stopping is the highest.

[0044] In the two-handed state, the driver is holding the steering wheel with both hands, and the response time is the shortest. Therefore, the risk of a collision when stopping is lowest in the two-handed state.

[0045] The one-handed state is a state in which the driver grips the steering wheel with one hand, and the response time is shorter than that in the non-grip state and longer than that in the two-handed state. Therefore, the risk of a collision when stopping in the one-handed state is lower than that in the non-grip state and higher than that in the two-handed state.

[0046] The CPU sets the risk index value In to a non-grasp value Ina when the grip state is a non-grasp state, sets the risk index value In to a one-handed grip value Inb when the grip state is a one-handed grip state, and sets the risk index value In to a two-handed grip value Inc when the grip state is a two-handed grip state. Among the non-grasp value Ina, one-handed grip value Inb, and two-handed grip value Inc, the non-grasp value Ina is set to the maximum value, and the two-handed grip value Inc is set to the minimum value.

[0047] <(3) Road Type> The CPU acquires road type information from the navigation device 24 and identifies the type of road on which the vehicle VA is currently traveling based on the road type information.

[0048] In general, the width of the driving area tends to vary depending on the type of road. For example, among expressways, general national roads, and general prefectural roads, expressways have the widest driving area, followed by general roads, and general prefectural roads have the narrowest driving area.

[0049] The wider the width of the driving area, the more likely the vehicle VA will jump out of the driving area if steering control is stopped. Therefore, the wider the width of the driving area, the higher the possibility that the vehicle VA will collide with an object outside the driving area if steering control is stopped (i.e., the higher the risk of a collision when stopping). Therefore, the CPU acquires a risk index value In such that the narrower the width of the driving area specified by the road type, the larger the risk index value In.

[0050] The CPU may also acquire image data from the front camera 22, obtain the width of the driving area in which the vehicle VA is currently driving based on the image data, and obtain the risk index value In based on the width.

[0051] <(4) Number of pedestrians and / or cyclists> The CPU obtains the number of pedestrians and / or bicycles present outside the current driving area based on the image data.

[0052] The greater the number of pedestrians and / or bicycles outside the vehicle's own driving area, the greater the possibility that the vehicle VA will collide with these pedestrians and / or bicycles if steering control is stopped (i.e., the higher the collision risk when stopping). Therefore, the CPU acquires a risk index value In such that the greater the number of pedestrians and / or bicycles, the greater the risk of collision when stopping.

[0053] <(5) Vehicle speed Vs> The CPU acquires a risk index value In such that the greater the vehicle speed Vs, the greater the centrifugal force. Therefore, the greater the vehicle speed Vs, the greater the risk of a collision when stopping.

[0054] As an example, the CPU applies the risk index values ​​In1 to In5 obtained based on the above (1) to (5) to the following formula (1) to obtain the risk index value In. In=α1·In1+α2·In2+α3·In3+α4·In4+α5·In5…Formula (1) α1 to α5 in the above formula (1) are weighting coefficients that are set to appropriate values ​​between "0" and "1".

[0055] The CPU may obtain the risk index value In based on at least one of the risk index values ​​In1 to In5.

[0056] (Controlled amount C, target controlled amount Ctgt and upper limit controlled amount Clmt) As described above, the CPU changes the steering torque Tr when steering control is performed. When the steering torque Tr is changed, the steering angle θ and the lateral acceleration Gy are also changed. Therefore, the control variable C of the steering control can be expressed as any one of the steering torque Tr, the steering angle θ, and the lateral acceleration Gy. The target control variable Ctgt is also expressed as any one of the steering torque Tr, the steering angle θ, and the lateral acceleration Gy. Similarly, the upper limit control variable Clmt is expressed as any one of the steering torque Tr, the steering angle θ, and the lateral acceleration Gy.

[0057] The CPU may change the upper limit vehicle speed Vlmt when the second lane keeping control is being executed as steering control, based on the risk index value In. Specifically, the CPU may change the upper limit vehicle speed Vlmt so that it becomes lower as the stop collision risk decreases (i.e., as the risk index value In decreases). This means that when the stop collision risk is relatively low, the driver does not need to grip the steering wheel even if the vehicle speed Vs is relatively high.

[0058] (Cause of steering control failure) The CPU stops steering control when the following causes 1 to 4 occur. Cause 1: When a failure is detected in a part related to steering control (such as the steering motor 40 and "parts that make up the steering mechanism 42") Cause 2: When the lens of the front camera 22 is dirty or blocked Cause 3: The temperature outside the vehicle is outside the operating range of the electronic components. Cause 4: When the object detection accuracy of the front camera 22 decreases

[0059] (Presentation screen) When the upper limit control amount Clmt is equal to or less than a predetermined first threshold, the CPU causes the display device 44 to display a first presentation screen for notifying the driver that the upper limit control amount Clmt has been set low. On the other hand, when the upper limit control amount Clmt is equal to or greater than a predetermined second threshold, the CPU causes the display device 44 to display a second presentation screen for notifying the driver that the upper limit control amount Clmt has been set high.

[0060] This allows the driver to know whether the upper limit control amount Clmt is high or low. Therefore, even if the driver feels uncomfortable with the steering control, the driver can understand that the cause is due to the upper limit control amount Clmt.

[0061] The driving assistance device 10 is applicable to vehicles such as engine vehicles, hybrid vehicles, plug-in hybrid vehicles, fuel cell vehicles, and electric vehicles.

[0062] The present invention can also be understood as a non-transitory computer-readable storage medium on which a program for realizing the functions of the device 10 is stored. [Explanation of symbols]

[0063] 10...vehicle control device, 20...vehicle control ECU, 22...front camera, 40...steering motor, 42...steering mechanism

Claims

1. A vehicle control device that performs steering control to make a lateral control amount of a vehicle coincide with a target control amount acquired based on a surrounding environment of the vehicle, The vehicle control device includes: When the steering control is being performed, the upper limit value of the target control amount is set to a larger value as the risk of a stop collision in which the vehicle collides with an object when the steering control is assumed to be stopped decreases; The steering control is performed so that the control amount does not exceed the upper limit value. A vehicle control device configured as above.

2. 2. The vehicle control device according to claim 1, The vehicle control device is configured to acquire the stop-time collision risk based on a distance when the vehicle traveling along the predicted path of the vehicle in the event of the steering control being stopped comes closest to the object. Vehicle control device.

3. 2. The vehicle control device according to claim 1, The vehicle control device is configured to acquire the stop collision risk based on a grip state of a steering wheel of the vehicle by a driver. Vehicle control device.

4. A vehicle control method in which a computer mounted on a vehicle performs steering control to match a lateral control amount of the vehicle with a target control amount acquired based on a surrounding environment of the vehicle, The vehicle control method includes: a first step of setting, when the computer is executing the steering control, an upper limit value of the target control amount to a value that increases as the risk of a stop collision in which the vehicle collides with an object when the steering control is assumed to be stopped decreases; a second step of the computer executing the steering control so that the control amount does not exceed the upper limit value, Vehicle control method.

5. A program for causing a computer mounted on a vehicle to execute steering control for matching a lateral control amount of the vehicle with a target control amount acquired based on a surrounding environment of the vehicle, the program comprising: The program a first step of causing the computer to set an upper limit value of the target control amount to a value that increases as a collision risk at a stop of the vehicle, that is, a collision of the vehicle with an object when the steering control is stopped, decreases, when the computer is causing the computer to execute the steering control; a second step of causing the computer to execute the steering control so that the control amount does not exceed the upper limit value. program.

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