Device for predicting sudden deceleration

Abstract

To provide a device capable of predicting sudden deceleration of a preceding vehicle.SOLUTION: A device predicting sudden deceleration includes: a sensor detecting a traveling state of a preceding vehicle traveling ahead of a vehicle; and a control part determining on the basis of the traveling state of the preceding vehicle detected by the sensor that there is a risk of sudden deceleration of the preceding vehicle when the preceding vehicle decelerates at a prescribed deceleration or higher and deceleration of the preceding vehicle continues for a prescribed time or longer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a device for predicting sudden deceleration. [Background technology]

[0002] Patent Document 1 discloses a device for determining sudden deceleration of a preceding vehicle. This device determines that the preceding vehicle has suddenly decelerated if all of the following four conditions are met: The first condition is that the relative speed between the vehicle and the preceding vehicle is smaller than a set value. The set value is set to a value smaller than 0. The second condition is that the relative acceleration between the vehicle and the preceding vehicle is smaller than a set value. The set value is set to a value smaller than 0. The third condition is that the inter-vehicle time deviation between the vehicle and the preceding vehicle is equal to or smaller than a threshold value. The fourth condition is that the target acceleration / deceleration calculated based on the inter-vehicle distance deviation and the relative speed is smaller than a set value. The set value is set to approximately 0. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-312311 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, sudden deceleration of the preceding vehicle is determined based on four conditions, and the vehicle is suddenly decelerated after sudden deceleration of the preceding vehicle is determined. Therefore, in the device described in Patent Document 1, there is a risk that the timing of suddenly decelerating the vehicle may be delayed. The present disclosure provides a device that can predict sudden deceleration of the preceding vehicle. [Means for solving the problem]

[0005] According to an embodiment of the present disclosure, there is provided an apparatus including a sensor and a control unit. The sensor detects a driving state of a preceding vehicle traveling ahead of a vehicle. The control unit determines, based on the driving state of the preceding vehicle detected by the sensor, that there is a risk of the preceding vehicle suddenly decelerating if the preceding vehicle decelerates at a predetermined deceleration or more and the deceleration of the preceding vehicle continues for a predetermined time or more.

[0006] In this system, if a preceding vehicle decelerates at a predetermined deceleration or more and the deceleration of the preceding vehicle continues for a predetermined time or more, it is determined that there is a risk of the preceding vehicle suddenly decelerating. Self-driving vehicles generally include an automated driving system and an emergency stop system. The automated driving system is set to a maximum deceleration that it can output and drives the vehicle at or below the maximum deceleration. The emergency stop system can stop the vehicle at a deceleration greater than that of the automated driving system. If there is a preceding vehicle, the automated driving system drives the vehicle while maintaining a predetermined distance between the preceding vehicle and the system. The automated driving system starts decelerating the vehicle when the inter-vehicle distance becomes shorter. However, since the automated driving system cannot decelerate at or above the maximum deceleration, if the tendency for the inter-vehicle distance to become shorter does not improve, the automated driving system will drive at the maximum deceleration for a while, and then the emergency stop system will be activated when a collision with the preceding vehicle is predicted. In other words, an automated driving vehicle performs a unique operation in which the automated driving system attempts to decelerate and avoid an accident, and if collision with the preceding vehicle is still predicted, the emergency stop system will suddenly decelerate. This device determines whether the stopping behavior of the preceding vehicle is similar to the first half of the characteristic behavior described above, i.e., the stopping behavior of the automated driving system before the intervention of the emergency stop system, thereby enabling the device to predict sudden deceleration of the preceding vehicle.

[0007] In one embodiment, when the control unit determines that there is a risk of the preceding vehicle suddenly decelerating, it may operate the vehicle's braking device to decelerate the vehicle at a deceleration rate equal to or greater than the deceleration rate set for sudden braking.

[0008] In one embodiment, when the control unit determines that there is a risk of the preceding vehicle suddenly decelerating and further when the overlap rate between the vehicle and the preceding vehicle is greater than or equal to a predetermined percentage, the control unit may operate the vehicle's braking device to decelerate the vehicle at a deceleration greater than or equal to the deceleration set for sudden braking.

[0009] In one embodiment, when the vehicle is decelerating at a deceleration rate equal to or greater than the deceleration rate set for sudden braking, if the preceding vehicle is decelerating at a predetermined deceleration rate or greater and the vehicle speed is equal to or greater than the predetermined speed, the control unit may determine the deceleration rate of the vehicle so as to maintain a required margin of error, which is a distance between the vehicle and the preceding vehicle traveling at the maximum deceleration rate, to avoid contact with the vehicle. [Effects of the Invention]

[0010] According to the present disclosure, a technique is provided that can predict sudden deceleration of a preceding vehicle. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a vehicle equipped with a device according to an embodiment. [Figure 2] FIG. 2 is a graph showing an example of the change in deceleration over time. [Figure 3] 3A, 3B, and 3C are schematic diagrams showing an example of a deceleration state of a vehicle. [Figure 4] FIG. 4 is a flowchart showing an example of the operation of the device. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated description will be omitted.

[0013] [Vehicle configuration] Fig. 1 is a block diagram showing an example of the configuration of a vehicle equipped with an apparatus according to an embodiment. As shown in Fig. 1, the apparatus 1 is mounted on a vehicle 2, for example. The vehicle 2 is an autonomous vehicle, for example.

[0014] Vehicle 2 is not limited to an autonomous vehicle, but may be a vehicle having at least an autonomous driving system that follows a vehicle ahead of the vehicle and an emergency stop system that quickly stops the vehicle. The autonomous driving system is, for example, adaptive cruise control (ACC). The emergency stop system is, for example, pre-crash safety (PCS). Alternatively, vehicle 2 may be a vehicle that assists in driving operations to follow a vehicle ahead of the vehicle and in driving operations to quickly stop the vehicle. Driving operation assistance also includes cases where only information is provided.

[0015] The vehicle 2 includes a sensor group 3, a driving ECU 4 (an example of a control unit), and an actuator 5. The device 1 includes the sensor group 3 and the driving ECU 4.

[0016] The ECU (Electronic Control Unit) is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a CAN (Controller Area Network) communication circuit, etc. The functions performed by the device 1 are realized when the driving ECU operates an actuator 5 of the vehicle 2 based on the detection results of the sensor group 3.

[0017] The sensor group 3 includes, for example, a sensor (one example of a sensor) that detects the surrounding environment of the vehicle 2 and a sensor that detects the driving state of the vehicle 2. The sensor that detects the surrounding environment of the vehicle 2 includes, for example, at least one of a camera and a radar sensor, and as a more specific example, detects the driving state of a preceding vehicle that is driving in front of the vehicle 2. The sensor that detects the driving state of the vehicle 2 includes, for example, a GPS receiver, a vehicle speed sensor, an acceleration sensor, and a yaw rate sensor. The sensor group 3 may also include a sensor that detects driving operations by the driver. The sensor that detects driving operations by the driver includes, for example, a brake pedal sensor, an accelerator pedal sensor, and a steering operation sensor.

[0018] For example, the driving ECU 4 operates the actuator 5 to cause the vehicle 2 to follow a vehicle ahead of the vehicle 2 based on the detection results of the sensor group 3. In other words, the driving ECU 4 realizes an automated driving system. Following a vehicle ahead of the vehicle 2 means driving the vehicle 2 while maintaining a predetermined inter-vehicle distance. The driving ECU 4 is configured to operate the actuator 5 within a predetermined acceleration / deceleration range. For example, the driving ECU 4 operates the actuator 5 to quickly stop the vehicle 2 based on the detection results of the sensor group 3. In other words, the driving ECU 4 realizes an emergency stop system. In the emergency stop system, the driving ECU 4 stops the vehicle 2 at a deceleration greater than the maximum deceleration of the automated driving system.

[0019] The actuators 5 are devices used for controlling the running of the vehicle 2. The actuators 5 include at least a drive actuator, a brake actuator (an example of a braking device), and a steering actuator.

[0020] [Drive ECU details] The driving ECU 4 determines whether the driving state of the preceding vehicle detected by the sensor group 3 is similar to the driving state before an emergency stop specific to an autonomous vehicle. Specifically, the driving ECU 4 determines whether the preceding vehicle decelerates at a predetermined deceleration or more and the deceleration of the preceding vehicle continues for a predetermined time or more. The predetermined deceleration is set in advance to determine whether the preceding vehicle is in a driving state before an emergency stop specific to an autonomous vehicle. The predetermined deceleration may be, for example, the maximum deceleration of the autonomous driving system of the vehicle 2 or a general vehicle. The predetermined deceleration may be a speed within a predetermined speed range including the above-mentioned maximum deceleration. The predetermined time is set in advance to determine whether the preceding vehicle is in a driving state before an emergency stop specific to an autonomous vehicle. The predetermined time is set appropriately through simulation, etc. The driving ECU 4 may determine whether the preceding vehicle decelerates at the maximum deceleration of the autonomous driving system and the deceleration of the preceding vehicle continues for a predetermined time or more.

[0021] FIG. 2 is a graph showing an example of the change in deceleration over time. The vertical axis represents deceleration (m / s 2 ), with the horizontal axis representing time (s). The solid line graph is an example of the change in deceleration over time of an autonomously driven vehicle undergoing sudden deceleration. The dashed line graph is an example of the change in deceleration over time of a manually driven vehicle. A typical autonomously driven vehicle has an autonomous driving system and an emergency stop system, and as shown in Figure 2, the range of deceleration that each system can exert is set in advance. For example, the autonomous driving system can drive vehicle 2 at a deceleration in the range of 0 to D1. The emergency stop system can stop vehicle 2 at a deceleration in the range of D1 or higher.

[0022] Under an automated driving system, an automated vehicle decelerates at a deceleration rate in the range of 0 to D1 due to factors such as the deceleration of a preceding vehicle. The automated vehicle gradually increases its deceleration rate until it reaches a maximum deceleration rate D1 at time T1, at which point it maintains the maximum deceleration rate D1. Thereafter, for example, at time T2, it is determined that continuing deceleration at the maximum deceleration rate D1 could result in a risk of contact, and the emergency stop system initiates sudden braking, bringing the automated vehicle to a halt. In this way, the automated vehicle attempts to decelerate at the automated driving system's maximum deceleration rate D1, and if it is still determined that there is a risk of contact, the emergency stop system initiates sudden braking. The deceleration rate D3 of the emergency stop system's sudden braking is greater than the automated driving system's maximum deceleration rate D1.

[0023] The behavior shown by the solid line graph is unique to autonomous vehicles. When driven by a driver, the tendency is completely different, as shown by the dashed line graph. When driven by a driver, the vehicle tends to decelerate at an initial deceleration rate D2, which is greater than the maximum deceleration rate D1 of the autonomous driving system, to leave a certain amount of space between vehicles, and then ease off the deceleration rate before stopping.

[0024] If the preceding vehicle decelerates at a predetermined deceleration or more and the deceleration of the preceding vehicle continues for a predetermined time or more, the driving ECU 4 determines that there is a risk of the preceding vehicle suddenly decelerating. In other words, the driving ECU 4 determines that the preceding vehicle is behaving like an automatically driven vehicle before an emergency stop, and determines that there is a risk of the preceding vehicle suddenly decelerating.

[0025] When it is determined that there is a risk that the preceding vehicle will suddenly decelerate, the driving ECU 4 may operate the actuator 5 of the vehicle 2 to decelerate the vehicle 2 at a deceleration equal to or greater than the deceleration set for sudden braking. The deceleration set for sudden braking is preset to a value greater than the maximum deceleration of the automated driving system. The deceleration set for sudden braking is, for example, the deceleration used in an emergency stop system. This allows the vehicle 2 to apply sudden braking early when there is a risk that the preceding vehicle will suddenly decelerate, thereby avoiding the risk of the inter-vehicle distance becoming too close. The driving ECU 4 may apply sudden braking early, taking into account a delay in the operation of the actuator 5.

[0026] The driving ECU 4 may execute the above-described early sudden braking operation taking into consideration the overlap ratio. The overlap ratio is the degree of lateral overlap. For example, when the driving ECU 4 determines that there is a risk of the preceding vehicle suddenly decelerating and the overlap ratio is equal to or greater than a predetermined ratio, the driving ECU 4 operates the actuator 5 of the vehicle 2 to decelerate the vehicle 2 at a deceleration equal to or greater than the deceleration set for sudden braking. The predetermined ratio is a preset overlap ratio for determining whether to execute early sudden braking, and is set appropriately by simulation or the like.

[0027] 3A, 3B, and 3C are schematic diagrams showing an example of a deceleration state of a vehicle. As shown in FIG. 3A, a case will be described as an example in which a preceding vehicle 10 is traveling ahead of the vehicle 2. Assume that the vehicle 2 is traveling so as to maintain a distance from the preceding vehicle 10. As shown in FIG. 3B, when the preceding vehicle 10 begins to gradually decelerate, the distance between the vehicle 2 and the preceding vehicle 10 decreases. In this case, the vehicle 2 starts decelerating. If the preceding vehicle 10 decelerates at a predetermined deceleration or more and the deceleration of the preceding vehicle 10 continues for a predetermined time or longer, it is determined that there is a risk of the preceding vehicle 10 suddenly decelerating. Then, as shown in FIG. 3C, the vehicle 2 applies sudden braking. In this way, the vehicle 2 applies sudden braking not in response to the preceding vehicle 10 suddenly decelerating, but in response to a determination that the preceding vehicle 10 is likely to suddenly decelerate.

[0028] Fig. 4 is a flowchart showing an example of the operation of the device 1. The flowchart shown in Fig. 4 starts when the device 1 receives a start instruction operation.

[0029] As shown in Fig. 4, first, in step S10, the driving ECU 4 of the device 1 senses the behavior of the preceding vehicle. Based on the detection results of the sensor group 3, the driving ECU 4 stores the deceleration of the preceding vehicle in the memory of the ECU or the like. Next, in step S12, the driving ECU 4 determines whether the preceding vehicle is decelerating at a predetermined deceleration or more. The driving ECU 4 reads out the predetermined deceleration stored in advance in the memory of the ECU or the like, and compares it with the deceleration sensed in step S10.

[0030] If the preceding vehicle is decelerating at a rate equal to or greater than the predetermined deceleration rate (step S12: YES), the driving ECU 4 determines whether the deceleration of the preceding vehicle has continued for a predetermined time or longer in step S14. The driving ECU 4 determines whether the deceleration of the preceding vehicle has continued for a predetermined time or longer based on the deceleration rate stored in the memory.

[0031] If the deceleration of the preceding vehicle continues for a predetermined time or longer (step S14: YES), the driving ECU 4 determines, in step S16, that there is a risk of sudden deceleration of the preceding vehicle.

[0032] If the preceding vehicle does not decelerate at a rate equal to or greater than the predetermined deceleration (step S12: NO), if the deceleration of the preceding vehicle does not continue for a predetermined time or longer (step S14: NO), or if step S16 is completed, the flowchart shown in Fig. 4 ends. The driving ECU 4 restarts the flowchart shown in Fig. 4 from the beginning until the termination condition is met.

[0033] By executing the flowchart shown in Fig. 4, the device 1 can determine the risk of sudden deceleration of the preceding vehicle. If the flow chart shown in Fig. 4 determines that there is a risk of sudden deceleration of the preceding vehicle, the driving ECU 4 operates the actuator 5 to decelerate the vehicle 2 at a deceleration equal to or greater than the deceleration set for sudden braking. This allows the device 1 to apply sudden braking earlier, thereby making it possible to avoid contact with the preceding vehicle compared to a device that applies sudden braking in response to the detection of sudden deceleration of the preceding vehicle.

[0034] Since the driving ECU 4 operates the actuator 5 based on a prediction, the preceding vehicle may not actually suddenly decelerate. Alternatively, the preceding vehicle may accelerate, increasing the distance between the vehicle and the preceding vehicle. For this reason, when the vehicle 2 is decelerating at a deceleration equal to or greater than the deceleration set for sudden braking, the driving ECU 4 determines whether the preceding vehicle is decelerating at a predetermined deceleration or greater and whether the speed of the vehicle 2 is equal to or greater than the predetermined speed.

[0035] When the above conditions are met, the driving ECU 4 may determine the deceleration of the vehicle 2 so as to maintain a required margin of clearance, which is a distance that can avoid contact between the vehicle 2 and a preceding vehicle traveling at maximum deceleration. The required margin of clearance is a distance that can avoid contact with the preceding vehicle when the preceding vehicle decelerates at maximum. In other words, the required margin of clearance is a distance that will prevent contact even if the preceding vehicle suddenly decelerates by full braking. Once the required margin of clearance is determined, the deceleration to be requested of the vehicle 2 is determined. When the above conditions are met, the device 1 causes the vehicle 2 to travel so as to maintain the required margin of clearance. The device 1 calculates the required margin of clearance every moment and changes the deceleration, thereby avoiding constantly requesting deceleration that is greater than necessary. This allows the device 1 to maintain a distance that allows for reliable stopping while avoiding stopping with an excessively large inter-vehicle distance or being left behind by the preceding vehicle. This also reduces the risk of contact with a following vehicle.

[0036] [Summary of the embodiment] According to the device 1, if the preceding vehicle decelerates at a predetermined deceleration rate or more and the deceleration of the preceding vehicle continues for a predetermined time or more, it is determined that there is a risk of the preceding vehicle suddenly decelerating. An autonomously driven vehicle will attempt to decelerate and avoid an accident using the autonomous driving system, and if contact with the preceding vehicle is still predicted, it will suddenly decelerate using the emergency stop system, a unique behavior. The device 1 determines whether the stopping behavior of the preceding vehicle is similar to the first half of the unique behavior described above, i.e., the stopping behavior of the autonomous driving system before the emergency stop system intervened. This allows the device to predict sudden deceleration of the preceding vehicle.

[0037] Although exemplary embodiments have been described above, the present invention is not limited to the exemplary embodiments described above, and various omissions, substitutions, and modifications may be made. The driving ECU 4 may only notify the driver when it is determined that there is a risk of the preceding vehicle suddenly decelerating. [Explanation of symbols]

[0038] 1...device, 2...vehicle, 3...sensor group (an example of a sensor), 4...driving ECU (an example of a control unit).

Claims

1. a sensor for detecting the driving state of a preceding vehicle traveling in front of the vehicle; a control unit that determines, based on the traveling state of the preceding vehicle detected by the sensor, that there is a risk of the preceding vehicle suddenly decelerating when the preceding vehicle decelerates at a predetermined deceleration or more and the deceleration of the preceding vehicle continues for a predetermined time or more; and A device for predicting sudden deceleration, comprising:

2. 2. The device according to claim 1, wherein, when it is determined that there is a risk of the preceding vehicle suddenly decelerating, the control unit activates a braking device of the vehicle to decelerate the vehicle at a deceleration equal to or greater than a deceleration set for sudden braking.

3. 3. The device according to claim 2, wherein the control unit, when it is determined that there is a risk of the preceding vehicle suddenly decelerating and further when the overlap ratio between the vehicle and the preceding vehicle is equal to or greater than a predetermined ratio, activates a braking device of the vehicle to decelerate the vehicle at a deceleration equal to or greater than a deceleration set for sudden braking.

4. 4. The device according to claim 3, wherein when the preceding vehicle is decelerating at a deceleration equal to or greater than a deceleration set for sudden braking, and the preceding vehicle is decelerating at a predetermined deceleration or greater and the speed of the vehicle is equal to or greater than a predetermined speed, the control unit determines the deceleration of the vehicle so as to maintain a required margin of error, which is a distance between the vehicle and the preceding vehicle traveling at a maximum deceleration, that can avoid contact between the vehicle and the preceding vehicle.

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