JP7848725B2 - Driving assistance device and driving assistance method - Google Patents

Description

This invention relates to a driver assistance device and a driver assistance method.

Patent Document 1 discloses a driver assistance device that prevents a vehicle from failing to stop at a designated stopping point or entering a slow-speed zone at high speed due to driver inattention. This driver assistance device alerts the driver when the distance between the vehicle's position and the stopping point or slow-speed zone is less than or equal to a warning distance set based on road information, and the time required to reach the stopping point or slow-speed zone is less than or equal to a predetermined time.

Patent No. 4765844

However, the need to slow down is not limited to the area immediately before a stopping point or a slow-down zone. For example, if there is a point ahead where the speed limit decreases, the vehicle must slow down before reaching that point.

Furthermore, at points where the speed limit is reduced, other vehicles may not necessarily be traveling at the new speed limit. For example, if the actual speed is lower than the new speed limit, simply slowing down to the new speed limit may be insufficient.

Therefore, in view of the above-mentioned problems, the object of the present invention is to assist a vehicle in decelerating in a manner that is appropriate to the actual driving environment when there is a point ahead of the vehicle where the speed limit decreases.

The gist of this disclosure is as follows:

(1) A driver assistance device comprising: a target speed setting unit that acquires the actual speed at a point in front of the vehicle where the speed limit decreases and sets a target speed for the vehicle at that point based on the actual speed; a deceleration calculation unit that calculates the deceleration required for the vehicle to slow down to the target speed at that point; and a notification unit that notifies the driver of the vehicle of a warning when the deceleration is greater than a predetermined threshold.

(2) The information notification device described in (1) above, in which the actual speed is set for each lane.

(3) The information notification device according to (1) or (2) above, wherein the target speed setting unit sets the target speed to a value obtained by adding a predetermined setting amount set by the vehicle driver to the actual speed.

(4) The information notification device according to any one of (1) to (3) above, wherein the threshold is set to the deceleration when the vehicle's accelerator is released.

(5) A driving assistance method performed by a computer, comprising: acquiring the actual speed at a point in front of the vehicle where the speed limit decreases; setting a target speed for the vehicle at the point based on the actual speed; calculating the deceleration required for the vehicle to slow down to the target speed at the point; and notifying the driver of the vehicle of a warning when the deceleration is greater than a predetermined threshold.

According to the present invention, when there is a point ahead of the vehicle where the speed limit decreases, it is possible to assist the vehicle in decelerating in a manner that is appropriate to the actual driving environment.

This diagram schematically shows a part of the configuration of a vehicle equipped with a driver assistance device according to an embodiment of the present invention. This is a functional block diagram of the ECU processor. This is a flowchart showing the control routine for warning processing. This figure shows an example of a situation where the speed limit decreases in front of a vehicle.

The embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, similar components will be given the same reference numerals.

Figure 1 is a schematic diagram showing a part of the configuration of a vehicle 1 equipped with a driver assistance device according to an embodiment of the present invention.

As shown in Figure 1, Vehicle 1 (the vehicle itself) is equipped with a surrounding information detection device 2, a GNSS (Global Navigation Satellite System) receiver 3, a map database 4, a navigation device 5, a vehicle behavior detection device 6, a Human Machine Interface (HMI) 7, a communication device 8, and an Electronic Control Unit (ECU) 10. The surrounding information detection device 2, GNSS receiver 3, map database 4, navigation device 5, vehicle behavior detection device 6, HMI 7, and communication device 8 are electrically connected to the ECU 10 via an in-vehicle network compliant with standards such as CAN (Controller Area Network).

The surrounding information detection device 2 acquires data (images, point cloud data, etc.) around the vehicle 1 (the vehicle itself) and detects surrounding information of the vehicle 1 (e.g., surrounding vehicles, signs, etc.). For example, the surrounding information detection device 2 includes a millimeter-wave radar, a camera (monocular camera or stereo camera), a LiDAR (Laser Imaging Detection And Ranging), or an ultrasonic sensor (sonar), or any combination thereof. The output of the surrounding information detection device 2, i.e., the surrounding information of the vehicle 1 detected by the surrounding information detection device 2, is transmitted to the ECU 10.

The GNSS receiver 3 detects the current position of vehicle 1 (e.g., the latitude and longitude of vehicle 1) based on positioning information obtained from multiple (e.g., three or more) positioning satellites. Specifically, the GNSS receiver 3 acquires multiple positioning satellites and receives radio waves transmitted from them. Then, the GNSS receiver 3 calculates the distance to the positioning satellite based on the difference between the transmission time and reception time of the radio waves, and detects the current position of vehicle 1 based on the distance to the positioning satellite and the position (orbital information) of the positioning satellite. The output of the GNSS receiver 3, i.e., the current position of vehicle 1 detected by the GNSS receiver 3, is transmitted to the ECU 10. The GNSS receiver includes a GPS receiver.

The map database 4 stores map information. The ECU 10 retrieves map information from the map database 4. Alternatively, the map database may be located outside the vehicle 1 (e.g., on a server), and the ECU 10 may retrieve map information from outside the vehicle 1.

The navigation device 5 sets the driving route for vehicle 1 to its destination based on the vehicle's current position detected by the GNSS receiver 3, map information from the map database 4, and input from the vehicle's occupants (e.g., the driver). The driving route set by the navigation device 5 is transmitted to the ECU 10.

The vehicle behavior detection device 6 detects parameters indicating the behavior of the vehicle 1. The vehicle behavior detection device 6 includes, for example, a vehicle speed sensor for detecting the speed of the vehicle 1, a yaw rate sensor for detecting the yaw rate of the vehicle 1, and the like. The output of the vehicle behavior detection device 6, i.e., the parameters detected by the vehicle behavior detection device 6, is transmitted to the ECU 10.

The HMI 7 is installed inside the vehicle and facilitates the exchange of information between the vehicle 1 and its occupants (e.g., the driver). The HMI 7 includes an output unit (e.g., display, speaker, light source, vibration unit, etc.) that provides information to the occupants of the vehicle 1, and an input unit (e.g., touch panel, operation buttons, operation switches, microphone, etc.) that receives information from the occupants of the vehicle 1. The output of the ECU 10 is notified to the occupants of the vehicle 1 via the HMI 7, and the input from the occupants of the vehicle 1 is transmitted to the ECU 10 via the HMI 7. The HMI 7 is an example of an input device, output device, or input/output device. Alternatively, the occupants' mobile terminals (smartphones, tablet devices, etc.) may be connected to the ECU 10 via wired or wireless connection and function as the HMI 7. Furthermore, the HMI 7 may be integrated with the navigation device 5.

The communication device 8 is capable of communicating with the outside of vehicle 1 and enables communication between vehicle 1 and the outside of vehicle 1. For example, the communication device 8 includes a wide-area communication device that enables wide-area communication between vehicle 1 and the outside of vehicle 1 (e.g., a server) via a communication network such as a carrier network or the Internet network; a vehicle-to-vehicle communication device that enables vehicle-to-vehicle communication between vehicle 1 and surrounding vehicles using a predetermined frequency band; and a vehicle-to-infrastructure communication device that enables vehicle-to-infrastructure communication between vehicle 1 and roadside equipment using a predetermined frequency band.

The ECU 10 performs various controls for the vehicle 1. As shown in Figure 1, the ECU 10 includes a communication interface 11, a memory 12, and a processor 13. The communication interface 11 and the memory 12 are connected to the processor 13 via signal lines. In this embodiment, one ECU 10 is provided, but multiple ECUs may be provided for each function.

The communication interface 11 has an interface circuit for connecting the ECU 10 to the in-vehicle network. The ECU 10 is connected to other in-vehicle equipment via the communication interface 11.

Memory 12 includes, for example, volatile semiconductor memory and non-volatile semiconductor memory. Memory 12 stores programs, data, etc., used when various processes are executed by the processor 13.

The processor 13 has one or more CPUs (Central Processing Units) and their peripheral circuits. The processor 13 may also have additional arithmetic circuits such as a logic unit or a numerical arithmetic unit.

Figure 2 is a functional block diagram of the processor 13 of the ECU 10. In this embodiment, the ECU 10 functions as a driver assistance device that supports the driver of the vehicle 1. The processor 13 of the ECU 10 has a target speed setting unit 14, a deceleration calculation unit 15, and a notification unit 16. The target speed setting unit 14, the deceleration calculation unit 15, and the notification unit 16 are functional modules realized by the execution of a computer program stored in the memory 12 of the ECU 10 by the processor 13 of the ECU 10. These functional modules may each be realized by dedicated arithmetic circuits provided in the processor 13.

The target speed setting unit 14 sets the target speed for vehicle 1. For example, if there is a point ahead of vehicle 1 where the speed limit decreases (hereinafter referred to as a "deceleration point"), vehicle 1 needs to decelerate by the time it reaches that point. Furthermore, at the deceleration point, other vehicles may not necessarily be traveling at the changed speed limit. For example, if the actual speed is lower than the changed speed limit, simply decelerating the vehicle to the changed speed limit may be insufficient. Therefore, the target speed setting unit 14 acquires the actual speed at the deceleration point and sets the target speed for vehicle 1 at the deceleration point based on the actual speed.

The deceleration calculation unit 15 calculates the deceleration required for vehicle 1 to slow down to the target speed at a deceleration point. The notification unit 16 then notifies the driver of vehicle 1 of a warning when the deceleration calculated by the deceleration calculation unit 15 exceeds a predetermined threshold. This allows the driver of vehicle 1 to decelerate at an appropriate time, and helps vehicle 1 decelerate in a manner appropriate to the actual driving environment when there is a point ahead where the speed limit decreases.

The following describes the control process flow described above, with reference to Figure 3. Figure 3 is a flowchart of the warning processing control routine. This control routine is repeatedly executed at predetermined intervals by the processor 13 of the ECU 10 (target speed setting unit 14, deceleration calculation unit 15, and notification unit 16).

First, in step S101, the target speed setting unit 14 determines whether the speed limit decreases in front of the vehicle 1. That is, the target speed setting unit 14 determines whether a deceleration point exists in front of the vehicle 1. The speed limit is determined by the legal maximum speed in areas without speed limit signs, and by the speed limit sign in areas with speed limit signs.

For example, the target speed setting unit 14 determines whether the speed limit in front of vehicle 1 decreases based on the output of the surrounding information detection device 2. Specifically, if the speed limit indicated by the speed limit sign detected by the surrounding information detection device 2 (e.g., a front camera) that detects information in front of vehicle 1 is lower than the current speed limit, the target speed setting unit 14 determines that the speed limit in front of vehicle 1 decreases. Figure 4 shows an example of a situation in which the speed limit in front of vehicle 1 decreases. In the example in Figure 4, the speed limit in front of vehicle 1 changes from 120 km/h to 90 km/h.

Furthermore, the target speed setting unit 14 may determine whether the speed limit decreases in front of the vehicle 1 based on the map information stored in the map database 4. In this case, the map information includes speed limit information for each point on the map. For example, the target speed setting unit 14 determines whether the speed limit decreases in front of the vehicle 1 by comparing the driving route of the vehicle 1 set by the navigation device 5 with the map information.

If it is determined in step S101 that the speed limit in front of vehicle 1 does not decrease, this control routine terminates. On the other hand, if it is determined in step S101 that the speed limit in front of vehicle 1 does decrease, this control routine proceeds to step S102.

In step S102, the target speed setting unit 14 acquires the actual speed at the deceleration point ahead of the vehicle 1. For example, the actual speed is set to a speed lower than the speed limit by a predetermined value (e.g., 5 km/h to 10 km/h). For example, if the predetermined value is 10 km/h, then when the speed limit at the deceleration point is 90 km/h, the actual speed will be set to 80 km/h.

The actual speed may be adjusted depending on weather conditions, time of day, etc. For example, the actual speed may be lower when it is raining or snowing compared to when it is sunny or cloudy. Weather conditions are detected, for example, based on the output of a rain sensor installed on vehicle 1. Furthermore, the actual speed may be lower during morning commute hours (e.g., 7:00 AM to 9:00 AM) and evening commute hours (e.g., 5:00 PM to 8:00 PM) compared to other times. The time of day is detected, for example, by a digital clock built into the ECU 10. Weather and time of day information may also be acquired from outside vehicle 1 via wide-area communication or vehicle-to-infrastructure communication.

Furthermore, the actual speed may be set for each lane. For example, on a road with two lanes (a driving lane and a passing lane), the actual speed in the passing lane may be higher than the actual speed in the driving lane. This allows for obtaining a more appropriate actual speed that takes into account the lane in which vehicle 1 is traveling.

Furthermore, the target speed setting unit 14 may acquire the actual speed by obtaining the speed of surrounding vehicles traveling ahead of vehicle 1 at deceleration points, based on the output of the surrounding information detection device 2 or via vehicle-to-vehicle communication. Alternatively, an external server may calculate the actual speed at each location based on speed information transmitted from multiple vehicles, and vehicle 1 may receive the actual speed at deceleration points from the server.

After step S102, in step S103, the target speed setting unit 14 sets the target speed of vehicle 1 at the deceleration point based on the actual speed. For example, the target speed setting unit 14 sets the target speed to the actual speed. Alternatively, the target speed setting unit 14 may set the target speed to a value obtained by adding a preset amount set by the vehicle 1 driver to the actual speed. This allows the driver's preference to be reflected in the target speed, enabling the vehicle 1 driver to decelerate at a more appropriate timing. For example, three preset amounts are provided (e.g., +2 km/h, +5 km/h, and +10 km/h), and the vehicle 1 driver selects a preset amount via the HMI 7. If the actual speed is 80 km/h and the preset amount is +5 km/h, the target speed is set to 85 km/h. Note that the preset amount may also be a negative value.

Next, in step S104, the deceleration calculation unit 15 calculates the deceleration required for the vehicle 1 to decelerate to the target speed set in step S103 at the deceleration point. For example, the deceleration a (m/s²) is calculated by the following formula ( ¹ ) based on the current speed Vc (m/s) of the vehicle 1, the target speed Vt (m/s) of the vehicle 1, and the distance L from the current position of the vehicle 1 to the deceleration point.
a=(Vc ² -Vt ² )/2L...(1)

The current speed Vc of vehicle 1 is obtained based on the output of the vehicle speed sensor of the vehicle behavior detection device 6, and the value of the target speed set in step S103 is used as the target speed Vt of vehicle 1. The distance L to the deceleration point is obtained based on the output of the surrounding information detection device 2, or based on the output of the GNSS receiver 3 and the map information stored in the map database 4. For example, if the current speed Vc of the vehicle is 33.33 m/s (120 km/h), the target speed Vt of vehicle 1 is 29.16 m/s (85 km/h), and the distance L to the deceleration point is 150 m, then the deceleration a will be 0.87 m/ ^s² (0.089 G).

Next, in step S105, the notification unit 16 determines whether the deceleration calculated in step S104 is below a predetermined threshold. The threshold is set to a fixed value, for example, 0.1G (0.98 m/ ^s² ). The threshold may also be set to the deceleration when the accelerator of the vehicle 1 is released. This helps the vehicle 1 to decelerate to the target speed through natural braking such as engine braking or regenerative braking.

The deceleration when the accelerator is released is pre-stored in the memory 12 of the ECU 10, or calculated based on vehicle specifications (weight, powertrain, etc.), road gradient information, road surface conditions, etc. Vehicle specifications are pre-stored in the memory 12 of the ECU 10. Road gradient information is obtained, for example, based on the output of the GNSS receiver 3, map information stored in the map database 4, or the output of the G sensor installed on the vehicle 1. Road surface conditions are obtained, for example, based on the output of the surrounding information detection device 2 or the output of the rain sensor installed on the vehicle 1.

Furthermore, the threshold may be set by the driver of vehicle 1. This allows vehicle 1 to decelerate to the target speed at the driver's preferred deceleration rate. For example, three threshold options (e.g., 0.05G, 0.1G, and 0.2G) are provided, and the driver of vehicle 1 pre-selects a threshold via HMI 7.

If the deceleration is determined to be greater than the threshold in step S105, the control routine proceeds to step S106. In step S106, the notification unit 16 notifies the driver of vehicle 1 of a warning via the HMI 7. For example, the notification unit 16 notifies an auditory warning, such as a buzzer sound or voice, via the speaker of the HMI 7. Alternatively, the notification unit 16 may notify a visual warning by displaying text or images prompting the vehicle 1 to decelerate via the display of the HMI 7. Furthermore, the notification unit 16 may notify a tactile warning via a vibration unit of the HMI 7 located on the steering wheel or accelerator pedal of vehicle 1.

After step S106, the control routine proceeds to step S107. However, if it is determined in step S105 that the deceleration is below a threshold, the control routine skips step S106 and proceeds to step S107. In step S107, the notification unit 16 determines whether the vehicle 1 has passed the deceleration point. This determination is made, for example, based on the output of the surrounding information detection device 2, or based on the output of the GNSS receiver 3 and the map information stored in the map database 4.

If it is determined in step S107 that vehicle 1 has passed the deceleration point, this control routine terminates. On the other hand, if it is determined in step S107 that vehicle 1 has not passed the deceleration point, this control routine returns to step S104, and steps S104 and S105 are executed again to determine whether a warning is necessary.

While preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims. For example, a server capable of communicating with the vehicle 1 via a wide-area communication network, such as a communication network, may function as a driver assistance device. In this case, vehicle information such as the position and speed of the vehicle 1 is periodically transmitted from the vehicle 1 to the server, and the notification unit of the server sends an instruction to the ECU 10 of the vehicle 1, thereby notifying the driver of the vehicle 1 via the HMI 7 of the vehicle 1 of a warning.

Furthermore, the computer program that enables the computer to implement the functions of each part of the ECU 10's processor 13 may be provided in a form stored on a computer-readable recording medium. Examples of computer-readable recording media include magnetic recording media, optical recording media, or semiconductor memory.

1. Vehicle 10. Electronic Control Unit (ECU)
13 Processor 14 Target speed setting unit 15 Deceleration calculation unit 16 Notification unit

Claims (5)

A target speed setting unit obtains the actual speed at a point in front of the vehicle where the speed limit decreases by obtaining the speed of surrounding vehicles traveling in front of the vehicle at the same point, or by obtaining the speed at the same point calculated by a server based on speed information of many vehicles from the server , and sets a target speed for the vehicle at the same point based on the actual speed.
A deceleration calculation unit that calculates the deceleration required for the vehicle to slow down to the target speed at the aforementioned point,
A driving assistance device comprising a notification unit that notifies the driver of the vehicle of a warning when the deceleration is greater than a predetermined threshold. The driving assistance device according to claim 1, wherein the actual speed is set for each lane. The driving assistance device according to claim 1 or 2, wherein the target speed setting unit sets the target speed to a value obtained by adding a preset amount set by the vehicle's driver to the actual speed. The driving assistance device according to claim 1 or 2, wherein the threshold is set to the deceleration when the vehicle's accelerator is released. A driving assistance method performed by a computer,
The actual speed at a point in front of a vehicle where the speed limit decreases is obtained by acquiring the speed of surrounding vehicles traveling in front of the vehicle at the same point, or by obtaining the speed at the same point calculated by a server based on the speed information of a large number of vehicles from the server .
Setting a target speed for the vehicle at the aforementioned point based on the actual operating speed,
To calculate the deceleration required for the vehicle to slow down to the target speed at the aforementioned point,
A driving assistance method that includes notifying the driver of the vehicle of a warning when the deceleration is greater than a predetermined threshold.