Collision damage reduction device

Abstract

To provide a collision damage reduction device which can balance a collision damage reduction performance with risk reduction at the time of defect of a collision damage reducing function.SOLUTION: A collision damage reduction device includes a guard function part comprising the steps of: outputting, when inputting a deceleration request signal from a control determination part and acquiring deceleration amount of an own vehicle from the time when the input of the deceleration request signal is started, the inputted value of the deceleration request signal as it is till the deceleration amount of the own vehicle reaches a deceleration amount limitation threshold value (Step S8); and outputting, after the deceleration amount of the own vehicle reaches the deceleration amount limitation threshold value, the value which is obtained by limiting the inputted deceleration request signal (Step S9). The guard function part includes the steps of: evaluating risk at the time of defect of a collision damage reducing function (Step S4); and changing the deceleration amount limitation threshold value according to the evaluated risk (Step S5).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a collision damage reduction device. [Background technology]

[0002] Patent document 1 describes that, in order to prevent excessive activation of the collision damage mitigation brake in certain situations, activation of the collision damage mitigation brake is suppressed when it is determined that the vehicle is approaching an intersection or ETC gate based on the vehicle's current position on a map. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-81911 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, a collision damage mitigation device is generally provided with a function to detect a collision damage mitigation brake malfunction (failure of the collision damage mitigation function). Furthermore, in consideration of a situation in which a collision damage mitigation brake malfunction cannot be detected, a guard function may be added to limit the deceleration amount of the collision damage mitigation brake regardless of whether the collision damage mitigation brake is malfunctioning or not.

[0005] However, the inherent performance of the collision mitigation brake and the risk reduction in the event of a collision mitigation brake failure due to the guard function are in a contradictory relationship, making it difficult to achieve both.

[0006] The present invention has been made in light of the circumstances described above, and aims to provide a collision damage mitigation device that can achieve both collision damage mitigation performance and risk reduction in the event that the collision damage mitigation function fails. [Means for solving the problem]

[0007] The present invention provides a collision damage mitigation device having a collision damage mitigation function that decelerates the host vehicle so as to reduce collision damage to occupants of the host vehicle when there is a high possibility of a collision of the host vehicle, the device comprising: an obstacle detection unit that detects an obstacle in front of the host vehicle; a control judgment unit that judges whether to decelerate the host vehicle when an obstacle is detected by the obstacle detection unit and outputs a deceleration request signal; a guard function unit that receives the deceleration request signal from the control judgment unit, acquires the deceleration amount of the host vehicle from the point at which the deceleration request signal starts to be input, and outputs the value of the input deceleration request signal as is until the deceleration amount of the host vehicle reaches a deceleration amount limit threshold, and outputs a limited value of the input deceleration request signal after the deceleration amount of the host vehicle reaches the deceleration amount limit threshold; and a braking control unit that receives the deceleration request signal from the guard function unit and controls a braking device to decelerate the host vehicle in accordance with the input deceleration request signal, wherein the guard function unit assesses a risk in the event of a failure of the collision damage mitigation function, and changes the deceleration amount limit threshold in accordance with the assessed risk. [Effects of the Invention]

[0008] As described above, according to the present invention, it is possible to provide a collision damage mitigation device that can achieve both collision damage mitigation performance and reduced risk in the event that the collision damage mitigation function fails. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of a vehicle equipped with a collision damage reduction device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the transition of input and output values ​​of a deceleration request signal in a guard function unit of a collision damage reduction device according to one embodiment of the present invention. [Figure 3] FIG. 3 is a diagram illustrating the transition of the deceleration amount and the deceleration amount limit threshold in the guard function unit of the collision damage reduction device according to one embodiment of the present invention. [Figure 4]FIG. 4 is a flowchart illustrating the guard function of the guard function unit of the collision damage reduction device according to one embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of an encounter evaluation function for the inter-vehicle time with a following vehicle, which is used in the guard function unit of the collision damage reduction device according to one embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing an example of a damage assessment function for the inter-vehicle time with a following vehicle, which is used in the guard function unit of the collision damage reduction device according to one embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example of an encounter evaluation function for precipitation used in the guard function unit of a collision damage mitigation device according to one embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of a damage assessment function for precipitation amount used in the guard function unit of a collision damage mitigation device according to one embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing an example of an encounter evaluation function for road gradient used in the guard function unit of a collision damage reduction device according to one embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing an example of a damage assessment function for road gradient used in the guard function unit of a collision damage mitigation device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] A collision damage mitigation device according to one embodiment of the present invention is a collision damage mitigation device having a collision damage mitigation function that decelerates the host vehicle so as to reduce collision damage to occupants of the host vehicle when there is a high possibility of a collision of the host vehicle, and comprises: an obstacle detection unit that detects obstacles in front of the host vehicle; a control judgment unit that judges whether to decelerate the host vehicle when an obstacle is detected by the obstacle detection unit and outputs a deceleration request signal; a guard function unit that receives the deceleration request signal from the control judgment unit, acquires the deceleration amount of the host vehicle from the point at which the deceleration request signal starts to be input, outputs the value of the input deceleration request signal as is until the deceleration amount of the host vehicle reaches a deceleration amount limit threshold, and outputs a limited value of the input deceleration request signal after the deceleration amount of the host vehicle reaches the deceleration amount limit threshold; and a braking control unit that receives the deceleration request signal from the guard function unit and controls a braking device to decelerate the host vehicle in accordance with the input deceleration request signal, and is characterized in that the guard function unit assesses the risk in the event of a failure of the collision damage mitigation function and changes the deceleration amount limit threshold in accordance with the assessed risk. As a result, the collision damage mitigation device according to one embodiment of the present invention can achieve both collision damage mitigation performance and reduced risk in the event that the collision damage mitigation function fails. [Example]

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle equipped with a collision damage reduction device according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0012] As shown in Fig. 1, the vehicle 1 is equipped with a braking device 9 and a collision damage mitigation device 10. The braking device 9 is made up of brakes that brake wheels (not shown), and decelerates the vehicle 1 by operating the brakes.

[0013] When there is a high possibility of a collision of the host vehicle, the collision damage mitigation device 10 controls the braking device 9 to decelerate the host vehicle so as to reduce collision damage to the vehicle occupants. In this way, the collision damage mitigation device 10 has a collision damage mitigation function.

[0014] The collision damage mitigation device 10 includes an obstacle sensor 2, a control determination unit 3, a guard function unit 7, and a braking control unit 8.

[0015] The obstacle sensor 2 detects an obstacle ahead of the vehicle. The obstacle sensor 2 detects an obstacle ahead using, for example, a millimeter wave radar (not shown) and measures the distance to the obstacle. When an obstacle is detected by the obstacle sensor 2, the control determination unit 3 determines whether or not to decelerate the vehicle and outputs a deceleration request signal. The deceleration request signal is a signal that indicates the deceleration (negative acceleration) requested of the vehicle 1.

[0016] The guard function unit 7 receives a deceleration request signal from the control determination unit 3, acquires the deceleration amount of the host vehicle from the start of input of the deceleration request signal, and outputs the value of the input deceleration request signal as is until the deceleration amount of the host vehicle reaches the deceleration amount limit threshold. After the deceleration amount of the host vehicle reaches the deceleration amount limit threshold, the guard function unit 7 outputs a limited value of the input deceleration request signal. In this embodiment, the guard function unit 7 outputs zero as the limited value of the deceleration request signal, but this is not limited to zero. The guard function unit 7 may also output a value smaller than the input value as the limited value of the deceleration request signal. The deceleration amount is the difference obtained by subtracting the current vehicle speed after deceleration (or during deceleration) from the vehicle speed before deceleration. The limited value of the deceleration request signal means that the deceleration value included in the deceleration request signal is limited.

[0017] The braking control unit 8 receives the deceleration request signal from the guard function unit 7 and controls the braking device 9 to decelerate the vehicle in accordance with the received deceleration request signal.

[0018] The control determination unit 3, guard function unit 7, and braking control unit 8 are configured by a computer unit having a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory, input ports, and output ports. The ROM of the computer unit stores various constants, maps, and the like, as well as programs for causing the computer unit to function as the control determination unit 3, guard function unit 7, and braking control unit 8. That is, in the computer unit, the CPU executes the programs stored in the ROM, causing the computer unit to function as the control determination unit 3, guard function unit 7, and braking control unit 8 in this embodiment.

[0019] The collision damage mitigation system 10 detects an obstacle ahead using the obstacle sensor 2 and determines the possibility of a collision with the host vehicle. If a collision is likely, the collision damage mitigation system 10 activates the braking system 9 to decelerate the host vehicle, thereby avoiding a collision with the obstacle or mitigating the damage caused by the collision. For example, if the host vehicle approaches a slow obstacle ahead (speed Vf) at a vehicle speed Va, and then determines the possibility of a collision and begins to decelerate, the host vehicle's speed is reduced by ΔVa from the vehicle speed Va when the host vehicle is closest to the obstacle, thereby avoiding a collision with the obstacle or mitigating the damage caused by the collision. In this case, the collision damage mitigation effect (performance) corresponds to the relative speed (Va-ΔVa)-Vf at the time of closest approach to or collision with the obstacle.

[0020] On the other hand, a malfunction of the collision damage mitigation device 10 may cause the host vehicle to suddenly decelerate unintentionally. A malfunction of the collision damage mitigation device 10 refers to a failure of the collision damage mitigation function due to an abnormality in the obstacle sensor 2, etc. If a following vehicle is traveling behind the host vehicle when the collision damage mitigation device 10 malfunctions, the driver of the following vehicle will suddenly brake to avoid a collision, but depending on the speed and duration of the sudden deceleration of the host vehicle and the distance between the host vehicle and the following vehicle, a collision may be unavoidable. The damage (risk) of a collision increases depending on the relative speed at the time of the collision.

[0021] For example, if a failure in the collision damage mitigation device 10 causes the vehicle to suddenly decelerate, and the following vehicle applies the brakes suddenly to avoid a collision, and when the following vehicle approaches the vehicle closest to the vehicle, the vehicle speed of the vehicle has decreased by ΔVa from the initial vehicle speed Va, and the vehicle speed of the following vehicle has decreased by ΔVb from the initial vehicle speed Vb, the damage (risk) of the collision will depend on the relative speed at the time of collision (Vb-ΔVb)-(Va-ΔVa).

[0022] To address this problem of unintended sudden deceleration of the vehicle due to a malfunction of the collision damage mitigation system 10, it is conceivable to incorporate a safety mechanism that prevents unintended sudden deceleration by detecting the malfunction. However, such a safety mechanism is not perfect and may not be able to detect the malfunction.

[0023] Therefore, the guard function unit 7 limits the amount of deceleration of the vehicle speed when the braking device 9 is activated if there is a possibility of a collision between the host vehicle and an obstacle, regardless of whether the collision damage reduction device 10 has failed. The function of the guard function unit 7 to limit the amount of deceleration of the vehicle speed is hereinafter referred to as the guard function. By limiting the amount of deceleration using this guard function, it is possible to avoid a collision with a following vehicle caused by an unintended sudden deceleration of the host vehicle, or to reduce damage.

[0024] The guard function unit 7 is disposed between the control determination unit 3 and the braking control unit 8. A deceleration request signal is input to the guard function unit 7 from the control determination unit 3. The guard function unit 7 measures the vehicle speed from the time when the deceleration request is started and calculates the change in vehicle speed as the deceleration amount. Alternatively, the guard function unit 7 calculates the deceleration amount by integrating the input deceleration request signal over time. The guard function unit 7 outputs the value of the input deceleration request signal as is to the braking control unit 8 until the calculated deceleration amount reaches the deceleration amount limit threshold, and after the calculated deceleration amount reaches the deceleration amount limit threshold, the guard function unit 7 limits the deceleration amount of the host vehicle by setting the value of the deceleration request signal output to the braking control unit 8 to zero.

[0025] The guard function of the guard function unit 7 will be described in detail with reference to FIGS.

[0026] As shown in Fig. 3, when the deceleration amount ΔVa has not reached the deceleration amount limit threshold ΔVs, the guard function unit 7 outputs the input value of the deceleration request signal as the output value as is, as shown in Fig. 2. After the input of the deceleration request signal (a value greater than zero) begins, the guard function unit 7 measures the vehicle speed (or time-integrates the input value of the deceleration request signal) and observes the deceleration amount ΔVa, as shown in Fig. 3. After the time Ts when the deceleration amount ΔVa reaches the deceleration amount limit threshold ΔVs, the guard function unit 7 sets the output value of the deceleration request signal to zero, regardless of the input value of the deceleration request signal, as shown in Fig. 2. Therefore, the vehicle 1 is not braked after Ts and coasts.

[0027] Here, the guard function unit 7 is capable of limiting the deceleration request signal regardless of whether the fault detection is successful or not, so it is effective even when the fault detection fails. However, since it also functions during the normal braking operation when there is a possibility of a collision with an obstacle ahead, depending on the value of the deceleration amount limit threshold ΔVs, it may reduce the normal collision damage mitigation performance (braking performance).

[0028] For example, if the deceleration amount limit threshold ΔVs is set to a large value, the deceleration request signal is less likely to be limited, improving the inherent collision damage mitigation performance against obstacles ahead, but increasing the risk of a collision with a following vehicle due to sudden deceleration in the event of a breakdown. Conversely, if the deceleration amount limit threshold ΔVs is set to a small value, the risk of a collision with a following vehicle due to sudden deceleration in the event of a breakdown decreases, but the inherent collision damage mitigation performance against obstacles ahead decreases. In other words, there is a trade-off between the inherent collision damage mitigation performance against obstacles ahead and the risk of a collision with a following vehicle due to sudden deceleration in the event of a breakdown.

[0029] If the deceleration limit threshold ΔVs is set to a fixed value of 50 km / h, even if the host vehicle approaches a stopped vehicle (obstacle) ahead while traveling at 50 km / h, deceleration can be completed before reaching the deceleration limit threshold ΔVs, and a collision with the obstacle can be avoided. However, if the host vehicle approaches a stopped vehicle (obstacle) ahead while traveling at 80 km / h, the deceleration limit threshold ΔVs will be reached when the host vehicle decelerates to 30 km / h, resulting in a collision with the obstacle at 30 km / h, and the collision cannot be avoided. On the other hand, if the host vehicle experiences an unintended sudden deceleration due to a malfunction while traveling at 80 km / h and a following vehicle is following, the driver of the following vehicle may suddenly brake to avoid a collision and decelerate to 40 km / h. In this case, the host vehicle will decelerate to 30 km / h, and the collision speed (relative speed) between the host vehicle and the following vehicle will be 10 km / h.

[0030] If the deceleration amount limit threshold ΔVs is set to a fixed value of 80 km / h, even if the host vehicle approaches a stopped vehicle (obstacle) ahead while traveling at 80 km / h, deceleration can be completed before the deceleration amount limit threshold ΔVs is reached, and a collision with the obstacle can be avoided. On the other hand, if an unintended sudden deceleration occurs due to a malfunction while the host vehicle is traveling at 80 km / h and a following vehicle is following, the driver of the following vehicle may apply the brakes suddenly to avoid a collision and decelerate to 40 km / h. In this case, the host vehicle will decelerate from 80 km / h to 0 km / h, and the collision speed (relative speed) between the host vehicle and the following vehicle will be 40 km / h.

[0031] In this way, if the deceleration amount limit threshold ΔVs is set to a fixed value, it is not possible to achieve both the original collision damage mitigation performance against obstacles ahead and the risk of collision with following vehicles due to sudden deceleration in the event of a malfunction.

[0032] Therefore, in this embodiment, the guard function unit 7 is configured to change the deceleration amount limit threshold value ΔVs to an optimum value according to the risk of a breakdown occurring, based on the current state of the vehicle.

[0033] The guard function unit 7 evaluates the risk in the event of a failure of the collision damage mitigation function, and changes the deceleration amount limit threshold in accordance with the evaluated risk.

[0034] The guard function unit 7 determines the risk when the collision damage mitigation function fails based on an encounter evaluation value that indicates the frequency of encountering a situation in which the host vehicle may be rear-ended by a following vehicle when the collision damage mitigation function fails, and a damage evaluation value that indicates the extent of damage to the occupants of the host vehicle when a rear-end collision by a following vehicle occurs when the collision damage mitigation function fails. Note that the encounter evaluation value can also be called an exposure evaluation value, as it indicates the degree of exposure to a situation in which a rear-end collision is possible.

[0035] The collision damage mitigation device 10 includes a rear vehicle sensor 4 that detects the distance between the host vehicle and a following vehicle. The guard function unit 7 determines the encounter evaluation value and the damage evaluation value based on at least the inter-vehicle time obtained by dividing the inter-vehicle distance by the vehicle speed of the host vehicle.

[0036] The collision damage mitigation device 10 includes a raindrop sensor 5 that acquires precipitation information. The guard function unit 7 determines the encounter assessment value and the damage assessment value based on at least the precipitation information.

[0037] The collision damage mitigation device 10 includes an inclination sensor 6 that detects the road gradient. The guard function unit 7 determines the encounter assessment value and the damage assessment value based on at least the road gradient.

[0038] If the risk in the unlikely event of a breakdown in the current situation of the vehicle is defined as the risk potential, this risk potential can be understood as the degree of damage that would be caused if a breakdown occurs in the current situation of the vehicle. The current risk potential can be quantified (quantified) based on the frequency with which the current situation of the vehicle is encountered and the magnitude of the damage.

[0039] The risk potential evaluation value R, which quantifies the current risk potential, can be defined by the formula R = Re * Rs, where Re is the current encounter evaluation value and Rs is the current damage evaluation value. The standard value for each evaluation value of R, Re, and Rs is 1, and if it is greater than 1, the risk is high (high encounter or high damage), and if it is less than 1, the risk is low (low encounter or low damage).

[0040] The deceleration amount limit threshold ΔVs that reflects the current risk potential is defined as the dynamic deceleration amount limit threshold ΔVsr. If the deceleration amount limit threshold for the standard guard function is ΔVs, the dynamic deceleration amount limit threshold ΔVsr can be defined by the formula ΔVsr=ΔVs / R. In this way, in this embodiment, rather than using a fixed deceleration amount limit threshold ΔVs, the standard deceleration amount limit threshold ΔVs is divided by the risk potential evaluation value R that corresponds to the current situation of the vehicle 1, and the dynamic deceleration amount limit threshold ΔVsr calculated by this calculation is used.

[0041] The operation of the guard function unit 7 will be described with reference to the flowchart shown in Fig. 4. This operation is repeatedly executed at a predetermined cycle.

[0042] 4, the guard function unit 7 grasps the current situation of the vehicle 1 (step S1). Here, the guard function unit 7 acquires the vehicle speed Va of the vehicle, the inter-vehicle distance D to the following vehicle, the amount of precipitation W, and the road gradient S.

[0043] Next, the guard function unit 7 calculates an encounter evaluation value (denoted as encounter evaluation (Re) in the drawing) of the current situation of the vehicle 1 (step S2).

[0044] Next, the guard function unit 7 calculates a damage assessment value (denoted as damage assessment (Rs) in the drawing) due to the occurrence of a failure in the current state of the vehicle 1 (step S3).

[0045] Next, the guard function unit 7 calculates the risk potential evaluation value (denoted as risk potential evaluation (R) in the figure) (step S4). Here, the guard function unit 7 calculates the risk potential evaluation value using the formula R=Re*Rs.

[0046] Next, the guard function unit 7 calculates the dynamic deceleration amount limit threshold (ΔVsr) (step S5). Here, the guard function unit 7 calculates the dynamic deceleration amount limit threshold (ΔVsr) by dividing the deceleration amount limit threshold (ΔVs) of the standard guard function by the current risk potential evaluation value (R).

[0047] Next, the guard function unit 7 determines the amount of deceleration (ΔV) of the current vehicle speed (step S6).

[0048] Next, the guard function unit 7 determines whether the deceleration amount has exceeded the limit (step S7). Here, the guard function unit 7 compares the current deceleration amount (ΔV) with the dynamic deceleration amount limit threshold (ΔVsr), and determines that the deceleration amount has exceeded the limit if ΔV≧ΔVsr.

[0049] If the deceleration amount does not exceed the limit (NO in step S7), the guard function unit 7 outputs the deceleration request signal input as a deceleration request output (step S8), and ends the current operation.

[0050] If the deceleration amount exceeds the limit (YES in step S7), the guard function unit 7 outputs zero as the deceleration request output regardless of the deceleration request signal input (step S9), and ends the current operation.

[0051] A first example and a second example will be given below in which specific numerical values ​​are applied to the flowchart shown in FIG.

[0052] In a first example, if the occurrence probability of the current vehicle situation is low (rarely encountered) in step S2, Re is evaluated as 0.7. If the damage if a breakdown occurs in that situation is within the expected standard, Rs is evaluated as 1 in step S3. In step S4, the risk potential is calculated as R = Re * Rs = 0.7 * 1 = 0.7. In step S5, assuming that the deceleration limit threshold ΔVs is 60 km / h, which is a standard value (a preset value), the dynamic deceleration limit threshold ΔVsr is calculated as ΔVs / R = 60 / 0.7 = 85.7 km / h. In step S8, if the current deceleration ΔV does not exceed the dynamic deceleration limit threshold ΔVsr = 85.7 km / h, the input value of the deceleration request signal is output as is. In step S9, if the current deceleration ΔV exceeds the dynamic deceleration limit threshold ΔVsr = 85.7 km / h, the deceleration request signal is set to zero.

[0053] In the second example, in step S2, if the probability of encountering the current vehicle situation is high (normally encountered), Re is evaluated as 1.2. In step S3, if the damage if a breakdown occurs in that situation is within the expected standard, Rs is evaluated as 1. In step S4, the risk potential is calculated as R = Re * Rs = 1.2 * 1 = 1.2. In step S5, assuming that the deceleration limit threshold ΔVs is 60 km / h, which is a standard value (a preset value), the dynamic deceleration limit threshold is calculated as ΔVsr = ΔVs / R = 60 / 1.2 = 50 km / h. In step S8, if the current deceleration ΔV does not exceed the dynamic deceleration limit threshold ΔVsr = 50 km / h, the input value of the deceleration request signal is output as is. In step S9, if the current deceleration ΔV exceeds the dynamic deceleration limit threshold ΔVsr = 50 km / h, the deceleration request signal is set to zero.

[0054] In these first and second examples, the dynamic deceleration amount limit threshold ΔVsr related to the guard function is changed depending on the situation. The performance of mitigating collision damage with a vehicle (forward obstacle) stopped ahead when the host vehicle is traveling at 80 km / h and approaches the vehicle, and the risk when an unintended sudden deceleration occurs due to a malfunction and the driver of the following vehicle suddenly brakes to decelerate to 40 km / h to avoid a collision can be understood as follows.

[0055] In the first example, the dynamic deceleration limit threshold ΔVsr was set to 85.7 km / h, and the collision damage mitigation performance was high in collision avoidance performance. Also, as for the risk of breakdown, the occurrence frequency of the encounter was low, and the damage was the result of a collision at 40 km / h. Therefore, the risk is at an acceptable level because the occurrence frequency is low, although the damage is large.

[0056] In the second example, the dynamic deceleration limit threshold ΔVsr was set to 50.0 km / h, and the collision damage mitigation performance was poor, with the collision occurring at a relative speed of 28.3 km / h. Furthermore, the risk of breakdown was high in terms of the frequency of encounters, and damage was low in terms of collisions at 10 km / h. Therefore, the risk was high in terms of frequency, but the damage was small, making it an acceptable level.

[0057] An example of the encounter evaluation function for the inter-vehicle time D / Va with the following vehicle will be described with reference to FIG.

[0058] In Figure 5, Red (D / Va) on the vertical axis represents the function value of the encounter evaluation function, and the horizontal axis represents the value of the inter-vehicle time D / Va (s: seconds) with the following vehicle as an argument. It is considered that situations where the inter-vehicle distance is short and the inter-vehicle time is extremely small, 0.4 (s), are rare, so the encounter evaluation value is set to 0.5. Situations where the inter-vehicle distance is long and the inter-vehicle time is quite large, 3.4 (s), are not very common, so the encounter evaluation value is set to 0.8. Situations where the inter-vehicle time is between 1.0 (s) and 2.4 (s), are considered common situations, and the encounter evaluation value is set to 1.0.

[0059] An example of a damage assessment function for the inter-vehicle time D / Va with the following vehicle will be described with reference to FIG.

[0060] In Figure 6, the vertical axis Rsd(D / Va) represents the function value of the damage assessment function, and the horizontal axis represents the value of the inter-vehicle time D / Va (s: seconds) with the following vehicle as an argument. In a situation where the inter-vehicle distance is short and the inter-vehicle time is extremely short at 0.4 (s), the following vehicle cannot brake in time, but because the inter-vehicle distance is short and the time until collision is short, the collision occurs before the host vehicle has had much time to decelerate, and the collision speed is relatively small, so the damage assessment value is 0.7. In a situation where the inter-vehicle time is short, between 0.8 (s) and 1.2 (s), the following vehicle cannot brake in time, but there is still time until collision, so the collision speed is high and the damage assessment value is 1.5. In a situation where the inter-vehicle time is normal, between 1.5 (s) and 3.0 (s), the damage assessment value is 1.0. In a situation where the inter-vehicle time is quite long, at 3.6 (s), the following vehicle can brake in time, so the damage assessment value is 0.2.

[0061] An example of an encounter evaluation function for precipitation amount W will be described with reference to FIG.

[0062] In Figure 7, Rew(W) on the vertical axis represents the function value of the encounter evaluation function, and the horizontal axis represents the precipitation W value (mm) as an argument. Precipitation W of 1 mm or more is considered rain, and the probability of rain (encounter evaluation value) is set to 0.3. Precipitation W of 10 mm or more is considered heavy rain, and the probability of heavy rain (encounter evaluation value) is set to 0.2.

[0063] An example of a damage assessment function for precipitation W will be described with reference to FIG.

[0064] In Figure 8, the vertical axis Rsw(W) represents the function value of the damage assessment function, and the horizontal axis represents the value of precipitation W (mm) as an argument. As precipitation increases, the road surface becomes wetter, reducing the coefficient of friction with the tires and reducing unintended deceleration (deceleration force). As deceleration decreases, the time required to achieve a certain speed reduction increases, making it easier for following vehicles to brake in time and increasing the ability of following vehicles to avoid an accident, resulting in a lower collision speed and reduced damage. When precipitation is 5 mm or more, the road surface is thought to have some effect on deceleration, so the damage assessment value is set to 0.9. When precipitation is 10 mm or more, the road surface is thought to have some effect on deceleration in heavy rain, so the damage assessment value is set to 0.7.

[0065] An example of an encounter evaluation function for a road gradient S will be described with reference to FIG.

[0066] In Figure 9, Res(S) on the vertical axis represents the function value of the encounter evaluation function, and the horizontal axis represents the value (%) of the road gradient S as an argument. Road gradients are defined as + for uphill gradients and - for downhill gradients, but since there is no distinction between the probability of existence of uphill and downhill gradients, the absolute value |S| is used for the road gradient value. Roads with gradients of 3% or less are considered flat, and the probability of existence (encounter evaluation value) for a 6% gradient is set to 0.5, and the probability of existence for a 9% gradient is set to 0.3. As a 16% gradient is considered to be quite rare, the probability of existence is set to 0.1.

[0067] An example of a damage assessment function for a road gradient S will be described with reference to FIG.

[0068] In Figure 10, Rss(S) on the vertical axis represents the function value of the damage assessment function, and the horizontal axis represents the value (%) of the road gradient S as an argument. An uphill road gradient is defined as +, and a downhill road gradient as -. On an uphill gradient, gravitational acceleration always acts in the deceleration direction depending on the incline, and unintended deceleration increases accordingly. As deceleration increases, the time required to achieve a certain speed reduction decreases, making it more difficult for the following vehicle to brake in time and reducing the ability of the following vehicle to avoid a collision, resulting in an increase in collision speed and greater damage. On a downhill gradient, gravitational acceleration always acts in the acceleration direction depending on the incline, and unintended deceleration decreases accordingly. As deceleration decreases, the time required to achieve a certain speed reduction increases, making it easier for the following vehicle to brake in time and improving the ability of the following vehicle to avoid a collision, resulting in a decrease in collision speed (relative velocity at the time of collision) and reduced damage.

[0069] An example in which specific values ​​are applied to these damage assessment functions will be described below. Here, the standard value of the deceleration amount limit threshold is set to ΔVs=60 km / h.

[0070] For example, if the time interval between the vehicle and the following vehicle is 3.4 seconds (the distance between the vehicles is quite long), the weather is fine, and the road is flat, then ΔVsr = 158 km / h as shown below, and the risk potential of the current vehicle situation is evaluated to be quite low, so the guard threshold can be lowered significantly below the standard, maximizing performance.

[0071] The calculation process for ΔVsr is explained below. D / Va = 3.4 s, so from the above function definition example, Red(D / Va) = 0.8, Rsd(D / Va) = 0.47. W = 0 mm, so from the above function definition example, Rew(W) = 1.0, Rsw(W) = 1.0. S = 0%, so from the above function definition example, Res(S) = 1.0, Rss(S) = 1.0. Re = Red(D / Va) * Rew(W) * Res(S) = 0.8 * 1.0 * 1.0 = 0.8. Rs = Rsd(D / Va) * Rsw(W) * Rss(S) = 0.47 * 1.0 * 1.0 = 0.47. R = Re * Rs = 0.8 * 0.47 = 0.38. Therefore, ΔVsr = ΔVs / R = 60 / 0.38 = 158 km / h.

[0072] Also, for example, if the inter-vehicle time with the following vehicle is 1.0 s (somewhat short), the weather is fine, and the road is flat, ΔVsr = 40 km / h as shown below, and the risk potential of the current vehicle condition is evaluated as high, so the guard threshold is lowered below the standard, ensuring safety while sacrificing some performance.

[0073] The calculation process for ΔVsr is explained below. Since D / Va = 1.0s, from the above function definition example, Red(D / Va) = 1.0 and Rsd(D / Va) = 1.5. Since W = 0mm, from the above function definition example, Rew(W) = 1.0 and Rsw(W) = 1.0. Since S = 0%, from the above function definition example, Res(S) = 1.0 and Rss(S) = 1.0. Re = Red(D / Va) * Rew(W) * Res(S) = 1.0 * 1.0 * 1.0 = 1.0. Rs = Rsd(D / Va) * Rsw(W) * Rss(S) = 1.5 * 1.0 * 1.0 = 1.5. R = Re * Rs = 1.0 * 1.5 = 1.5. Therefore, ΔVsr = ΔVs / R = 60 / 1.5 = 40 km / h.

[0074] Also, for example, if the time interval between the vehicle and the following vehicle is 1.0 s, there is 1 mm of rain, and the road is on a 3% uphill slope, ΔVsr = 121 km / h as shown below, and the risk potential of the current vehicle condition is evaluated as low, so the guard threshold can be raised above the standard, improving performance while ensuring safety.

[0075] The calculation process for ΔVsr will be explained. Since D / Va = 1.0s, from the above function definition example, Red(D / Va) = 1.0, Rsd(D / Va) = 1.5. Since W = 1mm, from the above function definition example, Rew(W) = 0.3, Rsw(W) = 1.0. Since S = +3%, from the above function definition example, Res(S) = 1.0, Rss(S) = 1.0. Re = Red(D / Va) * Rew(W) * Res(S) = 1.0 * 0.3 * 1.0 = 0.3. Rs = Rsd(D / Va) * Rsw(W) * Rss(S) = 1.5 * 1.0 * 1.0 = 1.5. R = Re * Rs = 0.3 * 1.5 = 0.45. Therefore, ΔVsr = ΔVs / R = 60 / 0.45 = 133 km / h.

[0076] In this way, the deceleration amount limit threshold of the guard function is dynamically changed according to the current vehicle situation.

[0077] Here, the deceleration request signal represents the deceleration (instantaneous deceleration) required of the vehicle 1, and deceleration is a negative acceleration. The output value of the deceleration request signal shown in FIG. 2 is constantly output from the guard function unit 7. That is, when no obstacle is detected ahead, the deceleration (instantaneous deceleration) required of the vehicle is zero. Even in such a case, a signal requesting a deceleration of zero (a signal that does not decelerate the vehicle) is constantly output as the deceleration request signal. If the deceleration request signal is an analog signal, the analog deceleration request signal is output as is. If the deceleration request signal is a digital signal, the requested instantaneous deceleration value becomes numerical data of the digital signal. The instantaneous deceleration can be set to any value, and can be changed over time. The guard function unit 7 can calculate the deceleration amount by accumulating the deceleration amount from the start of input of the deceleration request signal. For example, the guard function unit 7 can simply calculate the deceleration amount by accumulating the time during which a deceleration request signal with an instantaneous deceleration greater than zero is output. Alternatively, the guard function unit 7 can be configured to start deceleration when the deceleration request signal starts to be output and to end deceleration when the deceleration request signal stops being output. In this case, the instantaneous deceleration is a fixed value. However, by gradually increasing the deceleration from 0 when the deceleration request signal starts to be output and maintaining it at a predetermined value when it reaches that value, it is possible to achieve the deceleration shown in the graph in Figure 2 and avoid sudden changes in deceleration. In this configuration, the deceleration amount can be calculated by integrating the time during which the deceleration request signal is output.

[0078] As described above, in this embodiment, the collision damage reduction device 10 includes the obstacle sensor 2 that detects an obstacle ahead of the host vehicle, the control determination unit 3 that determines whether to decelerate the host vehicle when an obstacle is detected by the obstacle sensor 2 and outputs a deceleration request signal, the guard function unit 7 that receives the deceleration request signal from the control determination unit 3, acquires the deceleration amount of the host vehicle from the time when the deceleration request signal starts to be input, outputs the value of the received deceleration request signal as is until the deceleration amount of the host vehicle reaches the deceleration amount limit threshold, and outputs a limited value of the received deceleration request signal after the deceleration amount of the host vehicle reaches the deceleration amount limit threshold, and the braking control unit 8 that receives the deceleration request signal from the guard function unit 7 and controls the braking device 9 to decelerate the host vehicle in accordance with the received deceleration request signal. The guard function unit 7 evaluates the risk of a failure of the collision damage reduction function and changes the deceleration amount limit threshold in accordance with the evaluated risk.

[0079] This allows the risk of the collision mitigation function failing to be evaluated, and the deceleration amount limit threshold to be changed in accordance with the evaluated risk. As a result, it is possible to achieve both collision mitigation performance and reduced risk of the collision mitigation function failing. In other words, if the risk of the collision mitigation function failing is high, the deceleration amount limit threshold can be reduced to reduce the deceleration amount and deceleration time, thereby reducing the possibility of a rear-end collision with a following vehicle and the damage caused by the rear-end collision even if the collision mitigation function is accidentally activated. If the risk of the collision mitigation function failing is low, the deceleration amount limit threshold can be increased to increase the deceleration amount and deceleration time, thereby maintaining the collision mitigation performance and enabling the collision mitigation function to be activated against objects, vehicles, etc. located in front of the vehicle.

[0080] In addition, in this embodiment, the guard function unit 7 determines the risk in the event of a failure of the collision damage mitigation function based on an encounter evaluation value that indicates the frequency with which the vehicle will encounter a situation in which it may be rear-ended by a following vehicle when the collision damage mitigation function fails, and a damage evaluation value that indicates the extent of damage to the occupants of the vehicle when a rear-end collision by a following vehicle occurs when the collision damage mitigation function fails.

[0081] As a result, the risk when the collision damage mitigation function fails is determined based on an encounter evaluation value that indicates the frequency with which the vehicle will encounter a situation in which it may be rear-ended by a following vehicle when the collision damage mitigation function fails, and a damage evaluation value that indicates the extent of damage to the occupants of the vehicle when a rear-end collision by a following vehicle occurs when the collision damage mitigation function fails, thereby enabling an accurate assessment of the risk when the collision damage mitigation function fails.

[0082] In this embodiment, the collision damage mitigation device 10 also includes a rear vehicle sensor 4 that detects the distance between the host vehicle and a following vehicle. The guard function unit 7 determines the encounter evaluation value and the damage evaluation value based on at least the inter-vehicle time obtained by dividing the inter-vehicle distance by the vehicle speed of the host vehicle.

[0083] As a result, the encounter assessment value and the damage assessment value are determined based on at least the inter-vehicle time, so that the risk in the event of a failure of the collision damage mitigation function can be accurately assessed.

[0084] In this embodiment, the collision damage mitigation device 10 also includes a raindrop sensor 5 that acquires precipitation information. The guard function unit 7 determines the encounter evaluation value and the damage evaluation value based on at least the precipitation information.

[0085] As a result, the encounter assessment value and the damage assessment value are determined based on at least precipitation information, so that the risk in the event of a failure of the collision damage mitigation function can be accurately assessed.

[0086] In this embodiment, the collision damage mitigation device 10 also includes an inclination sensor 6 that detects the road gradient. The guard function unit 7 determines the encounter assessment value and the damage assessment value based on at least the road gradient.

[0087] As a result, the encounter assessment value and the damage assessment value are determined based on at least the road gradient, so that the risk in the event of a failure of the collision damage mitigation function can be accurately assessed.

[0088] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0089] 1 vehicle 2 Obstacle sensor (obstacle detection section) 3. Control decision section 4. Rear vehicle sensor (following vehicle detection section) 5 Raindrop sensor (precipitation information acquisition part) 6 Inclination sensor (gradient detection part) 7 Guard function section 8 Braking control section 9 Braking device

Claims

1. A collision damage mitigation device having a collision damage mitigation function that decelerates a host vehicle so as to reduce collision damage to a host vehicle occupant when there is a high possibility of a collision of the host vehicle, an obstacle detection unit that detects an obstacle ahead of the host vehicle; a control determination unit that determines whether to decelerate the host vehicle when an obstacle is detected by the obstacle detection unit and outputs a deceleration request signal; a guard function unit that receives the deceleration request signal from the control determination unit, acquires the deceleration amount of the host vehicle from the start of input of the deceleration request signal, outputs the input value of the deceleration request signal as is until the deceleration amount of the host vehicle reaches a deceleration amount limit threshold, and outputs a limited value of the input deceleration request signal after the deceleration amount of the host vehicle reaches the deceleration amount limit threshold; a braking control unit that receives the deceleration request signal from the guard function unit and controls a braking device to decelerate the host vehicle in accordance with the received deceleration request signal, The collision damage mitigation device is characterized in that the guard function unit evaluates the risk in the event of a failure of the collision damage mitigation function and changes the deceleration amount limit threshold in accordance with the evaluated risk.

2. The guard function unit reduces the risk of failure of the collision damage mitigation function by: an encounter evaluation value indicating the frequency of encountering a situation in which the host vehicle may be rear-ended by a following vehicle following the host vehicle when the collision damage mitigation function fails; 2. The collision damage mitigation device according to claim 1, wherein the determination is based on a damage assessment value indicating the extent of damage to the occupants of the vehicle in the event of a rear-end collision by the following vehicle when the collision damage mitigation function fails.

3. a following vehicle detection unit that detects a distance between the host vehicle and the following vehicle, 3. The collision damage reduction device according to claim 2, wherein the guard function unit determines the encounter evaluation value and the damage evaluation value based on at least the inter-vehicle time obtained by dividing the inter-vehicle distance by the vehicle speed of the host vehicle.

4. a precipitation information acquisition unit for acquiring precipitation information; 3. The collision damage reduction device according to claim 2, wherein the guard function unit determines the encounter assessment value and the damage assessment value based on at least the precipitation information.

5. A gradient detection unit is provided to detect a road gradient, 3. The collision damage reduction device according to claim 2, wherein the guard function unit determines the encounter assessment value and the damage assessment value based on at least the road gradient.

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