JP2020157835A - Control device of vehicle, control method of vehicle, and program - Google Patents

Abstract

To provide a control device of a vehicle and a method which can stabilize vehicle behavior in switching from automatic driving to manual driving.SOLUTION: A control device 200 of a vehicle includes: a road surface friction coefficient calculation part 210 which estimates a friction coefficient of a road surface on which the vehicle travels; an automatic driving enabling/disabling determination part 220 which determines, in carrying out automatic driving, whether to enable or disable continuing the automatic driving; and a vehicle control part 230 which, when the automatic driving enabling/disabling determination part 220 determines to disable continuing the automatic driving, limits drive force of the vehicle in manual driving on the basis of a limit value defined from the estimated friction coefficient.SELECTED DRAWING: Figure 1

Description

The present invention relates to a vehicle control device, a vehicle control method and a program.

Conventionally, for example, in Patent Document 1 below, when it is determined that it is difficult to continue automatic driving, the awakening state of the driver is grasped, and when the driver has manual driving ability, the automatic driving is shifted to manual driving and the manual operation is performed. It is stated that if there is no driving ability, an emergency evacuation is required.

Japanese Unexamined Patent Publication No. 2016-115356

The automatic driving of the vehicle is performed based on various sensor information. For example, when a situation occurs in which valid sensor information cannot be obtained, it is assumed that automatic operation will be switched to manual operation. However, when switching from automatic driving to manual driving, if the driver suddenly operates the accelerator, brakes, steering wheel, etc., it is assumed that the behavior of the vehicle becomes unstable. The technique described in Patent Document 1 does not consider that the vehicle behavior is disturbed when switching to manual driving.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is a new and improved vehicle capable of stabilizing vehicle behavior when switching from automatic driving to manual driving. The purpose is to provide a vehicle control device, a vehicle control method, and a program.

In order to solve the above problems, according to a certain viewpoint of the present invention, a friction coefficient estimation unit that estimates the friction coefficient of the road surface on which the vehicle travels and a determination unit for determining whether or not automatic driving can be continued when automatic driving is performed. Vehicle control that limits the driving force of the vehicle in manual driving based on the limit value determined from the estimated friction coefficient when the automatic driving possibility judgment unit and the automatic driving possibility judgment unit determine that the automatic driving cannot be continued. A vehicle control device comprising the unit and the vehicle is provided.

The friction coefficient estimation unit estimates the friction coefficient determined by the upper limit value and the lower limit value, and the vehicle control unit limits the driving force based on the limit value determined from the lower limit value of the friction coefficient. There may be.

Further, the vehicle control unit may release the limitation over a predetermined time after limiting the driving force.

Further, the vehicle control unit may increase the limit value determined from the lower limit value to the limit value determined from the upper limit value over a predetermined time after limiting the driving force. Further, the vehicle control unit may increase the limit value determined from the lower limit value to the limit value determined from the upper limit value at a predetermined ascending speed after limiting the driving force.

Further, the vehicle control unit may limit both the driving force of the front wheels and the rear wheels.

Further, it may be provided with an operation switching unit for switching to manual operation when it is determined that the automatic operation cannot be continued.

Further, in order to solve the above problems, according to another viewpoint of the present invention, a step of estimating the friction coefficient of the road surface on which the vehicle travels and a determination of whether or not the automatic driving can be continued when the automatic driving is performed are performed. Provided is a vehicle control method including a step of limiting the driving force of the vehicle in manual driving based on a limit value determined from the estimated friction coefficient when it is determined that the automatic driving cannot be continued. Will be done.

Further, in order to solve the above problem, according to another viewpoint of the present invention, a means for estimating the friction coefficient of the road surface on which the vehicle travels, and when automatic driving is performed, it is determined whether or not automatic driving can be continued. A program for operating a computer is provided as a means, a means for limiting a driving force of a vehicle in manual driving based on a limit value determined from the estimated friction coefficient when it is determined that the automatic driving cannot be continued. ..

According to the present invention, it is possible to stabilize the vehicle behavior when switching from automatic driving to manual driving.

It is a schematic diagram which shows the structure of the vehicle system 1000 which concerns on one Embodiment of this invention. It is a schematic diagram which shows the map used when the road surface friction coefficient calculation part determines the road surface condition. The map of FIG. 3A is a schematic view showing a three-dimensional map decomposed into a two-dimensional map. The map of FIG. 3A is a schematic view showing a three-dimensional map decomposed into a two-dimensional map. The map of FIG. 3A is a schematic view showing a three-dimensional map decomposed into a two-dimensional map. The map of FIG. 3A is a schematic view showing a three-dimensional map decomposed into a two-dimensional map. It is a schematic diagram which shows the example of the database which prescribed the relationship between the road surface condition and the friction coefficient. It is a flowchart which shows the process performed in the vehicle system 1000 of this embodiment. It is a schematic diagram for demonstrating the driving force according to the road surface condition in step S22 of FIG. It is a timing chart which shows how the driving force is limited when switching to a manual operation.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

First, the configuration of the vehicle system 1000 according to the embodiment of the present invention will be described with reference to FIG. The vehicle system 1000 is mounted on a vehicle such as an automobile. In the present embodiment, the vehicle on which the vehicle system 1000 is mounted is a vehicle capable of automatic driving and manual driving. As shown in FIG. 1, the vehicle system 1000 according to the present embodiment includes a first sensor 150, a second sensor 160, a vehicle speed sensor 170, a control device 200, a vehicle control drive device 300, a steering device 400, and an information presentation device. It is configured to have 500.

The control device 200 controls the entire vehicle system 1000. The control device 200 includes a road surface friction coefficient calculation unit (road surface friction coefficient estimation unit) 210, an automatic driving possibility determination unit 220, a vehicle control unit 230, a limit value calculation unit 240, an information presentation processing unit 250, and an operation switching unit 260. are doing. The component of the control device 200 shown in FIG. 1 can be composed of a circuit (hardware), a central processing unit such as a CPU, and a program (software) for functioning the central processing unit.

The first sensor 150 includes a camera that images the front of the vehicle, a temperature sensor (outside temperature sensor, road surface temperature sensor), a near infrared sensor, a millimeter wave radar, a laser radar (LiDAR), and a laser light sensor (TOF (Time of Flight)). It is a hybrid type sensor equipped with a non-contact type sensor (environment recognition sensor) such as a sensor), and detects environmental information such as an image in front of the vehicle, temperature, and road surface condition. When determining the road surface condition by the first sensor 150, for example, the method described in JP-A-2006-46936 may be adopted.

The second sensor 160 is a sensor used when the vehicle automatically drives, and includes a position sensor (GPS), a camera that images the front of the vehicle, a millimeter wave radar, a laser radar, and the like. A part or all of the first sensor 150 and the second sensor 160 may be configured in common.

The road surface friction coefficient calculation unit 210 of the control device 200 calculates the road surface friction coefficient in real time based on the detection of the image, temperature, etc. in front of the vehicle by the first sensor 150.

Specifically, the road surface friction coefficient calculation unit 210 acquires the color of the road surface in front of the vehicle, the road surface roughness, and the like from the image of the camera of the first sensor 150. Further, the road surface friction coefficient calculation unit 210 acquires the outside air temperature and the road surface temperature from the non-contact thermometer of the first sensor 150.

Further, the road surface friction coefficient calculation unit 210 acquires the water content of the road surface from the detection value of the near infrared sensor of the first sensor 150. When the road surface is irradiated with near infrared rays, if the road surface has a large amount of water, the amount of near infrared rays reflected decreases, and if the road surface has a small amount of water, the amount of near infrared rays reflected increases. Therefore, the road surface friction coefficient calculation unit 210 can acquire the water content of the road surface based on the detected value of the near infrared sensor.

Further, the road surface friction coefficient calculation unit 210 acquires the road surface roughness from the laser light sensor of the first sensor 150. More specifically, the roughness (unevenness) of the road surface in front of the vehicle can be acquired based on the time from the irradiation of the laser beam to the detection of the reflected light. The road surface friction coefficient calculation unit 210 acquires the roughness of the road surface in the region in front of the vehicle based on the vehicle speed and in consideration of the amount of movement of the road surface due to the traveling of the vehicle.

The road surface friction coefficient calculation unit 210 determines whether the road surface condition is dry (D), wet (W), snow (S), or ice (I) from these information acquired from the first sensor 150. FIG. 2A is a schematic view showing a map used by the road surface friction coefficient calculation unit 210 to determine the road surface condition. The map shown in FIG. 2A is a three-dimensional map whose parameters are normalized values of the road surface temperature, the road surface unevenness, and the water content of the road surface. 2B to 2E are schematic views showing the map three-dimensional map of FIG. 2A decomposed into two-dimensional maps. FIG. 2B shows a coordinate system of road surface temperature (Z-axis), road surface unevenness (X-axis), and road surface moisture content (Y-axis), and FIG. 2C shows a two-dimensional map of surface (1) of FIG. 2B. 2B shows a two-dimensional map of the (2) plane of FIG. 2B, and FIG. 2E shows a two-dimensional map of the (3) plane of FIG. 2B. The road surface friction coefficient calculation unit 210 applies the road surface temperature, road surface unevenness, and road surface water content acquired from the values detected by the first sensor 150 to the map of FIG. 2A to determine the road surface condition.

Then, the road surface friction coefficient calculation unit 210 calculates the road surface friction coefficient μN by reflecting the road surface state determined from the map of FIG. 2A in a database in which the relationship between the road surface state and the road surface friction coefficient is predetermined. FIG. 3 is a schematic diagram showing an example of a database in which the relationship between the road surface condition and the friction coefficient is defined in advance. In the database shown in FIG. 3, in the vertical direction, the coefficient of friction according to the road surface conditions "asphalt", "concrete", "gravel", "ice", and "snow" is shown. Further, in the lateral direction, the friction coefficient corresponding to dry (dry (D)) and wet (wet (W)) is shown as the road surface condition.

The road surface friction coefficient calculation unit 210 applies the road surface condition determined from the map of FIG. 2A to the database of FIG. 3 and calculates the road surface friction coefficient μ _N. At this time, regarding the determination of "asphalt", "concrete", and "gravel", the image of the road surface acquired from the camera of the first sensor 150 and the previously acquired "asphalt", "concrete", and "gravel" From the result of determining the similarity with each image of "", it is determined whether the road surface in front of the vehicle is "asphalt", "concrete", or "gravel".

Further, when the road surface friction coefficient calculation unit 210 determines that the road surface in front of the vehicle is "asphalt", the road surface image acquired from the camera of the first sensor 150 and the "new pavement" acquired in advance. , "Normal pavement", "Pavement wear", "Excessive tar" The road surface in front of the vehicle is "asphalt", and "new pavement", "normal pavement" , "Pavement wear" or "Tar excess" is determined. Similarly, when the road surface friction coefficient calculation unit 210 determines that the road surface in front of the vehicle is "concrete" or "gravel", it can make a further subdivided determination.

Based on the above, the road surface friction coefficient calculation unit 210 calculates the road surface friction coefficient μf in front of the vehicle from the database of FIG. 3 based on the road surface condition and the vehicle speed. For example, from the image of the camera of the first sensor 150, it is determined that the road surface is "new pavement" of "asphalt", the vehicle speed detected by the vehicle speed sensor 170 is 40 km / h, and the map of FIG. 2A. When the road surface condition is determined to be dry (dry (D)), the value of the road surface friction coefficient μf is calculated as 0.82 to 1.02.

The automatic driving possibility determination unit 220 determines whether or not automatic driving is possible based on the information acquired from the second sensor 160. The automatic operation possibility determination unit 220 determines that automatic operation is impossible when appropriate sensor information cannot be collected by the second sensor 160. Specifically, for example, the position sensor (GPS) cannot be used near a building, in a tunnel, or the like, and in such a case, the automatic driving possibility determination unit 220 determines that automatic driving is not possible. To do. Further, for example, when the camera constituting the second sensor 160 captures a scene with an inappropriate light source such as nighttime or backlight, or a scene with bad weather such as heavy fog, heavy rain, heavy snow, or heavy fog, an appropriate image cannot be captured. Therefore, it is judged that automatic operation is not possible.

Further, regarding the millimeter wave radar constituting the second sensor 160, the spatial resolution at the time of detection is inferior to that of other sensors, for example, when an object having low radio wave reflectance such as a cardboard box or foam styrene is detected. Since it is difficult to identify the object, it is judged that automatic operation is not possible.

Further, since the laser radar constituting the second sensor 160 uses infrared light, the detection performance deteriorates in bad weather such as heavy rain, heavy snowfall, and heavy fog. In such a case, the automatic operation possibility determination unit 220 determines that the automatic operation is impossible.

Further, the automatic operation possibility determination unit 220 may determine that the automatic operation is impossible when it is determined that the sensor does not function accurately due to the combination of the above conditions.

Further, the automatic operation possibility determination unit 220 determines that the automatic operation is impossible when the sensor fails due to damage or failure of the core component of the second sensor 160.

The operation switching unit 260 switches the operation mode from the automatic operation to the manual operation when it is determined that the automatic operation is impossible. The vehicle control unit 230 controls the vehicle control drive device 300. In particular, the vehicle control unit 230 controls the vehicle control drive device 300 to limit the driving force of the vehicle during manual driving when it is determined that automatic driving is not possible. The limit value calculation unit 240 calculates a driving force limit value for limiting the driving force of the vehicle when it is determined that automatic driving is not possible. When it is determined that automatic driving is not possible, the information presentation processing unit 250 controls the information presentation device 500 to present information to the occupants of the vehicle to switch to manual driving.

The vehicle control drive device 300 is a device that controls the vehicle. Specifically, the vehicle control device 300 is a device such as a motor, an engine (internal combustion engine), and a friction brake that drive the wheels of the vehicle and generate electricity by regeneration. The steering device 400 is a device that mainly steers the front wheels of the vehicle by steering. The steering device 400 can steer the front wheels by the driving force of the actuator. The steering device 400 may steer the rear wheels.

The information presenting device 500 is composed of a display, a speaker, and the like installed in the vehicle, and presents information to the occupants of the vehicle to switch from automatic driving to manual driving based on the instruction of the information presenting processing unit 250.

Next, the process performed by the vehicle system 1000 of the present embodiment will be described based on the flowchart of FIG. First, in step S10, the vehicle equipped with the vehicle system 1000 automatically drives. The automatic driving is performed by the vehicle control unit 230 controlling the vehicle control drive device 300 and the steering device 400 based on the information detected by the second sensor 160.

In the next step S12, the first sensor 150 detects the environmental information for calculating the road surface friction coefficient in order to grasp the road surface condition. In the next step S14, the road surface friction coefficient calculation unit 210 calculates the road surface friction coefficient of the currently traveling road surface based on the information detected by the first sensor 150.

In the next step S16, the automatic driving possibility determination unit 220 collects information indicating whether the automatic driving can be continued based on the information detected by the second sensor 160. In the next step S18, the automatic operation possibility determination unit 220 determines whether or not the automatic operation can be continued based on the information collected in step S16.

If it is determined in step S18 that the automatic operation can be continued, the process returns to step S10. On the other hand, if it is determined in step S18 that the automatic operation cannot be continued, the process proceeds to step S20. In step S20, the occupant of the vehicle is notified of a warning to switch to manual driving (non-automatic driving). The warning is given when the information presentation processing unit 250 issues a command to the information presentation device 500.

After step S20, the process proceeds to step S22. In step S22, the limit value calculation unit 240 calculates the limit value of the driving force of the vehicle according to the road surface condition. In the next step S24, the automatic operation is switched to the manual operation, and the manual operation is performed based on the limit value calculated in the step S22.

In step S24, the occupant (driver) of the vehicle operates the accelerator by manual driving, and the vehicle control drive device 300 limits the driving force. At this time, if the driving force of the vehicle instructed by the accelerator operation exceeds the limit value calculated in step S22, the driving force of the vehicle is limited up to the limit value.

FIG. 5 is a schematic diagram for explaining the driving force set according to the road surface condition based on the limit value calculated in step S22 of FIG. In FIG. 5, the driving forces of the front (front wheels) and the rear (rear wheels) of the vehicle are shown by friction circles. The friction circle shown by the broken line in FIG. 5 indicates the driving force (driving force during automatic operation) at the time when it is determined in step S18 of FIG. 4 that the automatic operation cannot be continued. On the other hand, the friction circle shown by the alternate long and short dash line in FIG. 5 indicates the driving force during manual operation limited by the limit value calculated according to the road surface condition in step S24 of FIG.

In the calculation by the road surface friction coefficient calculation unit 210, the upper limit value and the lower limit value of the road surface friction coefficient μN are calculated based on FIG. In step S22 of FIG. 4, in anticipation of safety, the limit value of the driving force is calculated using the lower limit value (minimum friction coefficient) of the road surface friction coefficient. Specifically, the radius of the driving force shown by the one-point chain line in FIG. 5 is obtained by multiplying the lower limit value of the road surface friction coefficient calculated in step S14 by the vertical load of the wheel. The driving force is limited at both the front and the rear. As a result, the driving force is controlled below the limit value at both the front and the rear.

As described above, when the automatic driving cannot be continued, the driving force (or braking force) by the vehicle control driving device 300 is limited to a value corresponding to the current lower limit value of the friction coefficient. As a result, the driving force can be limited according to the current road surface condition, and the vehicle behavior can be stabilized when switching from automatic driving to non-automatic driving (manual driving). In particular, by limiting the driving force to a value corresponding to the current lower limit of the coefficient of friction of the road surface, the driving force can be limited to the minimum value that allows for safety, so that the vehicle behavior is surely stabilized. Can be done.

On the other hand, in the above-mentioned example, the driving force is limited to a value corresponding to the lower limit of the current road surface friction coefficient, but the driving force limit value may be set based on the current road surface friction coefficient. , It does not necessarily have to be a value corresponding to the lower limit value. For example, the limit value may be set based on a value between the upper limit value and the lower limit value of the road surface friction coefficient. In addition, when the calculation accuracy of the road surface friction coefficient is very high and the difference between the upper limit value and the lower limit value is very small, the friction coefficient that allows for safety obtained by subtracting a predetermined amount from the calculated road surface friction coefficient. The limit value may be set based on.

In the present embodiment, various methods can be used as the method of limiting the actual driving force based on the driving force limiting value. For example, the accelerator opening degree of the accelerator operated by the driver may be limited, or the accelerator opening speed may be limited. Further, in the case of an electric vehicle, the electric power of the motor for driving the wheels may be limited.

FIG. 6 is a timing chart showing how the driving force is limited when switching to non-automatic operation. FIG. 6 shows how the state of the automatic driving impossible flag and the driving force limit values of the front wheels and the rear wheels change with the passage of time.

The time t0 shown in FIG. 6 indicates the time when the automatic operation is switched to the manual operation in step S24 of FIG. Before time t0, automatic driving is performed, and the driving force of the front wheels and the rear wheels is limited to the driving force obtained from the upper limit value of the friction coefficient calculated in step S14. If it is determined that the automatic operation cannot be continued at time t0, the automatic operation impossible flag is raised.

Further, when it is determined that the automatic driving cannot be continued at time t0, the driving force of the vehicle is lowered up to the limit value calculated by the limit value calculation unit 240, and the driving force of the front wheels and the rear wheels is limited. .. The driving force limit value corresponds to the driving force obtained from the lower limit of the friction coefficient calculated in step S14, and corresponds to the driving force of the friction circle shown by the alternate long and short dash line shown in FIG. As a result, the torque of the front wheels and the rear wheels is reduced, the vehicle behavior when switching from automatic driving to non-automatic driving is stabilized, and safety can be ensured.

The torque down is continuously performed until the time t1, the driving force limit value gradually increases after the time t1, and returns to the value before the time t0 at the time t2. As described above, the driving force limit value before the time t0 is a value obtained from the upper limit value of the friction coefficient. The time from time t1 to t2 is a predetermined time (n seconds). By raising the driving force limit value over n seconds, it is possible to prevent acceleration failure from occurring. Further, after the time t1, the driving force limit value may be gradually increased at a predetermined ascending speed to return to the value before the time t0 at the time t2.

If the road surface friction coefficient calculated by the road surface friction coefficient calculation unit 210 has changed from the time point in step S14 at time t2, the driving force is limited based on the road surface friction coefficient at time t2. You can call it. For example, if the road surface condition is "dry" before time t0 and the road surface condition changes to "frozen" at time t2, the driving force is limited based on the road surface friction coefficient at time t2. As a result, the vehicle behavior can be stabilized in response to changes in the road surface condition during the transitional period when switching from automatic driving to manual driving.

After that, when the automatic operation availability determination unit 220 determines that it is possible to return to the automatic operation based on the information detected by the second sensor 160 or the like, the automatic operation can be restored.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

200 Control device 210 Road surface friction coefficient calculation unit 220 Automatic driving availability judgment unit 230 Vehicle control unit

Claims (9)

A friction coefficient estimation unit that estimates the friction coefficient of the road surface on which the vehicle travels,
When automatic driving is being performed, the automatic driving availability judgment unit that determines whether or not automatic driving can be continued, and
A vehicle control unit that limits the driving force of a vehicle in manual driving based on a limit value determined from the estimated friction coefficient when the automatic driving possibility determination unit determines that automatic driving cannot be continued.
A vehicle control device, characterized in that. The friction coefficient estimation unit estimates the friction coefficient determined by the upper limit value and the lower limit value, and
The vehicle control device according to claim 1, wherein the vehicle control unit limits the driving force based on the limit value determined from the lower limit value of the friction coefficient. The vehicle control device according to claim 1 or 2, wherein the vehicle control unit releases the limitation over a predetermined time after limiting the driving force. The second aspect of the present invention, wherein the vehicle control unit limits the driving force and then raises the limit value determined from the lower limit value to the limit value determined from the upper limit value over a predetermined time. Vehicle control device. According to claim 4, the vehicle control unit limits the driving force and then raises the limit value determined from the lower limit value to the limit value determined from the upper limit value at a predetermined ascending speed. The vehicle control device described. The vehicle control device according to any one of claims 1 to 5, wherein the vehicle control unit limits both the driving force of the front wheels and the rear wheels. The vehicle control device according to any one of claims 1 to 6, further comprising an operation switching unit that switches to manual driving when it is determined that the automatic driving cannot be continued. Steps to estimate the coefficient of friction of the road surface on which the vehicle travels,
Steps to determine whether or not to continue automatic driving when automatic driving is being performed,
A step of limiting the driving force of the vehicle in manual driving based on a limit value determined from the estimated friction coefficient when it is determined that the automatic driving cannot be continued.
A vehicle control method, characterized in that. A means of estimating the coefficient of friction of the road surface on which the vehicle travels,
Means for determining whether or not autonomous driving can be continued when autonomous driving is being performed,
A means for limiting the driving force of a vehicle in manual driving based on a limit value determined from the estimated friction coefficient when it is determined that the automatic driving cannot be continued.
A program to make your computer work as.

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