JP7825367B2 - Driving assistance devices - Google Patents

Description

This invention relates to a device that provides assistance to facilitate vehicle driving operations, and in particular to a driving assistance device that controls the start of a vehicle by following a preceding vehicle.

When a vehicle travels, it is preferable for it to travel in coordination with other vehicles traveling in the same direction. However, because the flow of vehicles changes due to various factors, it is necessary to accelerate and decelerate in response to these changes. Adaptive cruise control (ACC control) is known as an example of control that reduces such acceleration and deceleration operations. ACC control detects a preceding vehicle using detection means such as radar or lidar, and if there is no preceding vehicle, controls the driving force to maintain the vehicle speed set by the driver (controlled vehicle speed). If a preceding vehicle is detected, ACC control controls the driving force while maintaining a predetermined distance from the preceding vehicle. More recently, a control system has been developed that stops the vehicle in pursuit of the preceding vehicle, and, when the preceding vehicle starts moving, starts the vehicle or allows the vehicle to start when the relative relationship between the vehicle and the preceding vehicle, such as the vehicle speed and distance, exceeds a predetermined threshold.

Patent Document 1 describes a device configured to start a vehicle using so-called tracking control. The device described in Patent Document 1 executes control to stop and start the vehicle in response to the stopping and restarting of a leading vehicle while controlling driving to follow the leading vehicle so as to maintain a safe distance from the leading vehicle. Specifically, the device described in Patent Document 1 estimates the vehicle speed of the leading vehicle a predetermined time after start-up based on the vehicle speed and acceleration when the leading vehicle restarts, and sets a target vehicle speed for resuming tracking driving based on the estimated vehicle speed and the following distance. Then, when the target vehicle speed exceeds a predetermined threshold, the device allows the driver to operate a switch to resume ACC control and starts the vehicle.

Patent Document 2 also describes a device configured to change the threshold value used to determine whether the host vehicle should start. The device described in Patent Document 2 is configured to reflect the behavior of other vehicles traveling parallel to the host vehicle and other vehicles in the oncoming lane in its start control when the host vehicle stops following a leading vehicle and then starts following the leading vehicle's departure. More specifically, the device described in Patent Document 2 increases the start threshold value when a vehicle in an adjacent lane is not traveling (stopped) compared to when it is traveling, and increases the start threshold value when an oncoming vehicle is not traveling (stopped) compared to when it is traveling. In other words, if a nearby vehicle traveling in the same direction as the host vehicle or an oncoming vehicle traveling in the opposite direction to the host vehicle is stopped, it is predicted that the leading vehicle will soon stop even if it is moving. Therefore, by increasing the start threshold value used as the basis for determining whether to follow the leading vehicle's departure, the host vehicle can appropriately follow the leading vehicle's slight starts and stops.

JP 2011-240927 A JP 2019-84924 A

In the device described in Patent Document 1, the host vehicle is allowed to start moving when the target vehicle speed exceeds a threshold value. In other words, even if the entire flow of vehicles, including the host vehicle, starts moving, if the preceding vehicle is delayed in starting, the target vehicle speed will not exceed the threshold value, preventing the host vehicle from starting, which causes the driver to feel a sense of delay in starting. In other words, the timing of the host vehicle's start is fixedly limited to the timing determined by the threshold value.

In addition, the device described in Patent Document 2 increases the departure threshold when nearby or oncoming vehicles are stopped, thereby avoiding or suppressing situations such as the host vehicle continuing to move despite being affected by the slight movement of the leading vehicle when the host vehicle is about to stop. However, because the departure threshold is increased, when the host vehicle restarts after stopping, the distance between the host vehicle and the leading vehicle may increase, or the host vehicle may not be able to start moving until the leading vehicle's speed increases significantly, resulting in a significant delay in starting. Furthermore, the lanes on which nearby or oncoming vehicles are traveling, which are referenced in the control described in Patent Document 2, are different from the lane on which the host vehicle is traveling. Therefore, the host vehicle and nearby or oncoming vehicles may differ in terms of whether they can move or the factors restricting their movement. In other words, the behavior of nearby or oncoming vehicles may not be useful for controlling the host vehicle's departure. As a result, the device described in Patent Document 2 may delay starting or approach the leading vehicle too closely, causing discomfort to the driver.

This invention was made in response to the above technical issues, and aims to provide a driving assistance device that enables a vehicle to start without delay by taking into account the behavior of the vehicle ahead that is traveling in the same lane as the vehicle in question when controlling the start of a vehicle following a preceding vehicle.

To achieve the above object, this invention provides a driving assistance device that enables the host vehicle to start following the preceding vehicle when the preceding vehicle starts moving from a stopped state following the preceding vehicle and the relative relationship between the preceding vehicle and the host vehicle exceeds a predetermined threshold. The device is characterized by being configured to determine whether another vehicle, a second preceding vehicle, is present in front of the preceding vehicle, determine whether the second preceding vehicle has started moving while the host vehicle was stopped following the preceding vehicle, and reduce the threshold value to make it easier for the host vehicle to start moving if it is determined that the second preceding vehicle has started moving.

In this invention, when it is determined that the preceding vehicle is not present ahead of the preceding vehicle that the host vehicle is following, the threshold value may be reduced to make it easier for the host vehicle to start moving.

In this invention, when the second-first vehicle starts moving from a state in which the vehicle in question and the preceding vehicle are stopped, the threshold value for determining whether to start following the preceding vehicle is reduced. Therefore, if the second-first vehicle starts moving, the subsequent forward movement of the preceding vehicle will almost certainly result in the preceding vehicle starting. In that case, the vehicle in question will start moving, or will be able to start moving, before the preceding vehicle moves forward and the distance between the vehicles becomes particularly large, or before the preceding vehicle's speed increases particularly. Therefore, this invention makes it possible to avoid or reduce the sense of delay when starting following the preceding vehicle.

Furthermore, if there is no vehicle ahead of you, the space ahead of the leading vehicle will be clear, so if the leading vehicle starts moving from a stopped state, the change in behavior is almost certainly an indication that the vehicle is starting to move. In such cases, too, by reducing the threshold, it is possible to avoid or reduce the perceived delay in starting when starting your own vehicle to follow the leading vehicle.

1 is a diagram schematically illustrating an example of a vehicle according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating the functional configuration of the controller. FIG. 2 is a schematic diagram showing the positional relationship between the host vehicle, a preceding vehicle, and a vehicle ahead of the preceding vehicle when stopped; 3 is a flowchart illustrating an example of control executed in the embodiment of the present invention.

Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely one example of how the present invention may be implemented, and is not intended to limit the scope of the present invention.

In an embodiment of the present invention, a vehicle travels while maintaining a distance from the vehicle immediately ahead that is at least a preset distance; if the vehicle ahead stops, the vehicle stops while maintaining a predetermined distance; and if the vehicle ahead starts moving, the vehicle starts moving after the vehicle ahead. One example of this type of driving control is a conventionally known control known as adaptive cruise control (ACC control). Therefore, as shown schematically in Figure 1, vehicle 1 includes a controller 2 that performs ACC control, a power controller (PCU) 3 that controls the driving force or braking force of vehicle 1 based on control signals from controller 2, and a radar sensor 4 that detects the vehicle ahead and the surrounding conditions.

Controls such as ACC control, which maintains a predetermined distance or greater from the preceding vehicle while driving, may be similar to the vehicle stop/start control described in the aforementioned Patent Document 2, or conventionally known constant-speed cruise control or ACC control. That is, a set vehicle speed (or control vehicle speed), which is a target vehicle speed during driving, and the following distance (predetermined following distance) from the preceding vehicle are manually input, and if the distance from the preceding vehicle is equal to or greater than the set following distance, the driving force is controlled so that the vehicle speed becomes equal to the set vehicle speed. Furthermore, if the distance to the preceding vehicle becomes shorter than the set following distance due to another vehicle cutting in, the vehicle decelerates to increase the distance from the preceding vehicle. Furthermore, in an embodiment of the present invention, when the preceding vehicle stops due to a stop light or other reason, the vehicle decelerates and closes to the following distance at the time of stopping, stopping the vehicle. Then, when the preceding vehicle starts moving, the relative relationship determined by the following distance, the vehicle speed, and other factors exceeds a predetermined threshold, and the vehicle starts moving after following the preceding vehicle.

Devices and systems are provided to detect data used for such driving control. A navigation system (NAV) 5 is provided to acquire data such as the vehicle's position and driving environment. NAV 5 is a conventionally known system that determines the vehicle's position and destination on a map by referencing a position determined by autonomous navigation using signals from GPS satellites and gyros, as well as a pre-prepared map. Furthermore, NAV 5 is preferably configured to be compatible with VICS (registered trademark), and is preferably configured to acquire road or environmental information around or in the vicinity of the vehicle via FM multiplex broadcasting, radio beacons, or optical beacons.

Furthermore, in order to drive in coordination with other vehicles around the vehicle, the vehicle is equipped with a vehicle-to-vehicle communication system 6 that acquires data about the other vehicles from those other vehicles. Data acquired by this vehicle-to-vehicle communication system 6 includes, for example, the speed, acceleration and deceleration, driving direction, and current position of the other vehicles.

The radar sensor 4 is a sensor for detecting vehicles ahead of the host vehicle, structures such as road facilities, obstacles, and even pedestrians, and may include a millimeter-wave radar sensor or a lidar sensor. In this embodiment of the invention, in addition to data on the preceding vehicle immediately ahead of the host vehicle, it is also configured to acquire data on the vehicle immediately ahead of the preceding vehicle (i.e., the vehicle two vehicles ahead of the host vehicle). The data on the vehicle two vehicles ahead may be the same as the data on the preceding vehicle, but is particularly data on the start and stop of the vehicle two vehicles ahead. This data is configured to be acquired by the NAV 5, radar sensor 4, or vehicle-to-vehicle communication system 6 described above.

When performing vehicle speed assistance control such as ACC control, the controller 2 is configured to determine the target vehicle speed based on data acquired by the above-mentioned radar sensor 4, NAV 5, or vehicle-to-vehicle communication system 6, or to determine whether to stop or start, and to calculate the stopping position, and to output the results as a control command signal to the PCU 3. Similar to vehicles equipped with conventional ACC control, the PCU 3 controls the driving force sources, including the engine, motor, and transmission, based on the input control command signal to maintain the vehicle speed at a set speed, or to decelerate or accelerate the vehicle depending on the distance to the preceding vehicle, and to stop or start the vehicle. Starting the vehicle may also require a driver's operation, such as a switch operation.

The controller 2 that performs the above control is an electronic control device primarily composed of a microcomputer consisting of arithmetic elements, memory elements, and input/output interfaces. A schematic diagram of the functional configuration for performing control in an embodiment of the present invention is shown in Figure 2. As mentioned above, the driving assistance device of the embodiment described here controls vehicle speed, starting, stopping, etc. based on the relative relationship between the preceding vehicle immediately before the host vehicle and the vehicle immediately preceding the preceding vehicle. Therefore, the controller 2 is equipped with a preceding vehicle information acquisition unit 2A and a preceding vehicle information acquisition unit 2B. The information acquired by these information acquisition units 2A and 2B is data obtained from the aforementioned radar sensor 4, NAV 5, or vehicle-to-vehicle communication system 6. The preceding vehicle information acquisition unit 2A acquires control data such as the presence or absence of a preceding vehicle, the distance between the preceding vehicle and the preceding vehicle, and the vehicle speed of the preceding vehicle. The preceding vehicle information acquisition unit 2B also acquires data such as the presence or absence of a preceding vehicle, its stopping and starting, etc. Therefore, in this embodiment of the present invention, the second-preceding vehicle information acquisition unit 2B corresponds to a function or means for determining whether the second-preceding vehicle is present, and a function or means for determining whether the second-preceding vehicle has departed.

The system is equipped with a departure threshold change unit 2C that changes the threshold value (departure threshold value) used to determine whether the host vehicle has departed. When following a preceding vehicle and stopping, and then starting to follow the preceding vehicle, it is necessary to determine whether the preceding vehicle has departed, and the departure threshold value is the threshold value used to make that determination. These threshold values include a threshold value for inter-vehicle distance and a threshold value for vehicle speed. The threshold value for inter-vehicle distance is predetermined by design to prevent rear-end collisions or excessive closeness. The threshold value for vehicle speed is also predetermined by design to determine whether the preceding vehicle has not simply moved forward but is gradually accelerating, i.e., has actually departed. Other data, such as the duration of the preceding vehicle's forward movement, may also be used to determine whether the preceding vehicle has departed; in that case, threshold values for the other data would also be set. Setting the departure threshold value to a large value can avoid or mitigate rear-end collisions, contact, or excessive closeness, but it also results in the host vehicle starting to depart later than the preceding vehicle. The departure threshold value is set taking these circumstances into consideration, but in this embodiment of the invention, the departure threshold value is shortened based on the status of the vehicle ahead, and the departure threshold value modification unit 2C modifies the departure threshold value. This modification is performed when it is determined that a vehicle ahead is present and has departed, and therefore the departure threshold value modification unit 2C corresponds to the function or means for shortening the threshold value in this embodiment of the invention.

The system also includes a departure determination unit 2D that determines whether the host vehicle, which is stopped following a preceding vehicle, should be allowed to start. This determination is similar to that made in normal ACC control, and the host vehicle is caused to start or permitted to start when the inter-vehicle distance to the preceding vehicle exceeds a threshold value, or when the vehicle speed of the preceding vehicle exceeds a threshold value. A departure instruction unit 2E is also provided that instructs the PCU 3 to start the host vehicle when the departure determination unit 2D determines that the host vehicle should start.

Next, an example of control according to an embodiment of the present invention will be described. FIG. 3 schematically illustrates a situation in which a group of vehicles, including host vehicle M0, are stopped at a red light Sr, and FIG. 4 shows a flowchart for explaining an example of control executed in this situation. Host vehicle M0 is stopped in the left lane of a two-lane road, with preceding vehicle M1 and preceding vehicle M2 stopped side by side ahead. Furthermore, other vehicles M3, M4, M5, etc. are stopped side by side in the right lane near the center. In this situation, host vehicle M0 acquires data, such as from the aforementioned radar sensor 4, NAV 5, or vehicle-to-vehicle communication system 6, that it is stopped at the red light Sr, that preceding vehicle M1 and preceding vehicle M2 are stopped, and that the inter-vehicle distance Gv between host vehicle M0 and preceding vehicle M1 is a predetermined distance.

In this stopped state, the control shown in Figure 4 is executed. First, it is determined whether the host vehicle M0 is stopped in accordance with the preceding vehicle M1 (step S1). If the determination in step S1 is negative, the routine shown in Figure 4 is temporarily terminated without any particular control. Conversely, if the determination in step S1 is positive, it is determined whether the second preceding vehicle M2 is present (step S2). If the determination in step S2 is positive because the second preceding vehicle M2 is present, it is determined whether the second preceding vehicle M2 has started moving (step S3). The determination of whether the second preceding vehicle M2 has started moving may be made based on whether the forward speed of the second preceding vehicle M2 is equal to or greater than a predetermined vehicle speed, whether the second preceding vehicle M2 has simply moved forward, or whether the forward distance has exceeded a predetermined value.

If step S3 returns a positive result because the preceding vehicle M2 has started moving, the threshold value (start threshold value) for determining whether the host vehicle M0 has started moving is reduced (lowered) (step S4). The reduction amount may be a predetermined amount in design. Conversely, if step S3 returns a negative result, the threshold value (start threshold value) is not changed but is maintained at the preset value (step S5).

Next, it is determined whether the relationship between the preceding vehicle M1 and the subject vehicle M0, such as the vehicle distance from the preceding vehicle M1 and the vehicle speed of the preceding vehicle M1, exceeds the above-mentioned departure threshold (step S6). In other words, it is determined whether the preceding vehicle M1 has moved forward and the subject vehicle M0 is ready to depart. Note that if the vehicle distance and vehicle speed have been detected, step S6 can set the condition for the subject vehicle M0 to depart that both the vehicle distance and vehicle speed exceed the departure threshold. However, as mentioned above, if it has already been determined that the vehicle M2 ahead of the subject vehicle M2 has departed, the condition for the subject vehicle M0 to depart can also be that only one of the vehicle distance or vehicle speed exceeds the departure threshold.

If the answer to step S6 is affirmative, a command to start or permission to start is output (step S7). Conversely, if the answer to step S6 is negative, the command to start or permission to start is not output, and the vehicle remains stopped (step S8).

Therefore, with the above control, when the preceding vehicle M1 that the host vehicle M0 is following starts moving and the relationship with the host vehicle M0, such as the inter-vehicle distance, exceeds the start threshold, the host vehicle M0 starts or is permitted to start. In this case, if the preceding vehicle M2 has already started moving, the start threshold is reduced, so when the preceding vehicle M1 starts moving, the inter-vehicle distance and other factors exceed the start threshold in a short period of time, eliminating or shortening the delay in the host vehicle M0's start. In other words, the perceived delay in starting can be eliminated. In particular, a driving assistance device configured to perform the above control controls the start of the host vehicle M0 based on the behavior of the preceding vehicle M1 and the preceding vehicle M2 in the same lane as the host vehicle M0, enabling appropriate start control. For example, in the situation shown in Figure 3, if start control is performed based on the behavior of vehicles M3 to M5 in adjacent lanes as the behavior of surrounding vehicles, and if the lane of vehicle M0 remains stopped due to a vehicle turning left, while vehicles are flowing smoothly in the adjacent right lane, start control will be performed based on the behavior of other vehicles unrelated to the start of vehicle M0, which could cause vehicle M0 to stop immediately after starting, or to get too close to leading vehicle M1.

If the answer to step S2 in Figure 4 is negative, the threshold value (start threshold value) for determining whether to start the host vehicle M0 is reduced (step S9), similar to the control in step S4 described above. If there is no vehicle M2 ahead of the host vehicle M1, it is considered normal for the host vehicle M1 to start moving forward and continue traveling in that direction. Therefore, even slight movement of the host vehicle M1 is enough to determine whether to start the host vehicle M0, enabling a quick start.

REFERENCE SIGNS LIST 1 Vehicle 2 Controller 2A Leading vehicle information acquisition unit 2B Second preceding vehicle information acquisition unit 2C Threshold value change unit 2D Start determination unit 2E Start instruction unit 3 Power control unit (PCU)
4 Radar sensor 5 Navigation system (NAV)
6 Inter-vehicle communication system M0: Vehicle M1: Leading vehicle M2: Second-lead vehicle

Claims (2)

1. A driving assistance device that enables a host vehicle to start following a preceding vehicle when the preceding vehicle starts moving from a stopped state following the preceding vehicle and a relative relationship between the preceding vehicle and the host vehicle exceeds a predetermined threshold value,
determining whether a second preceding vehicle is present ahead of the preceding vehicle;
determining whether the preceding vehicle has started moving while the host vehicle is stopped following the preceding vehicle;
A driving assistance device characterized in that, when it is determined that the second preceding vehicle has started moving, the threshold value is reduced so as to make it easier for the host vehicle to start moving. The driving assistance device according to claim 1,
A driving assistance device characterized in that, when it is determined that the preceding vehicle is not present in front of the preceding vehicle that the subject vehicle is following, the threshold value is reduced to make it easier for the subject vehicle to start moving.