Road surface condition detection device

Abstract

To provide a road surface condition detection device that allows a user to easily determine the necessity of road surface repairs.SOLUTION: A road surface condition detection device includes a computer 4 that receives a detection value of a left wheel speed sensor 2 and a detection value of a right wheel speed sensor 3. The computer 4 calculates the left wheel acceleration which is the wheel acceleration of the left wheel 91 on the basis of the detection value of the left wheel speed sensor 2, calculates the right wheel acceleration which is the wheel acceleration of the right wheel 92 on the basis of the detection value of the right wheel speed sensor 3, and determines whether or not the detected irregularity of the road surface is a specific step that is not the repairing object of the road surface on the basis of the information related to a maximum value of the left wheel acceleration and the information related to a maximum value of the right wheel acceleration in a prescribed period with detection of the irregularity of the road surface as a trigger of counting of the elapsed time when the irregularity of the road surface is detected on the basis of the left wheel acceleration and the right wheel acceleration.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a road surface condition detection device. [Background technology]

[0002] An apparatus for determining the unevenness of a road surface using the detected value from a wheel speed sensor is described, for example, in Japanese Patent Publication No. 60-596. This apparatus calculates the wheel acceleration from the detected value from the wheel speed sensor and determines the unevenness of the road surface based on the variance, the difference between the maximum and minimum values, etc. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-596 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Conventional road surface condition detection devices detect certain bumps that do not require road repair, such as bridge joints, as road surface roughness, just like potholes and other irregularities that do require repair. In other words, conventional road surface condition detection devices could not determine whether a large input to the wheels was due to road surface roughness or a road joint. Consequently, with conventional road surface condition detection devices, users could not easily determine the necessity of repairs when planning road surface repairs.

[0005] The object of the present invention is to provide a road surface condition detection device that can easily enable users to determine whether or not road surface repair is necessary. [Means for solving the problem]

[0006] The road surface condition detection device of the present invention is provided for the left wheel and includes a left wheel speed sensor that detects the wheel speed of the left wheel, and is provided for a right wheel arranged opposite to the left wheel in the left-right direction, and a right wheel speed sensor that detects the wheel speed of the right wheel, and a computer that receives the detection value of the left wheel speed sensor and the detection value of the right wheel speed sensor. The computer calculates a left wheel acceleration, which is the wheel acceleration of the left wheel, based on the detection value of the left wheel speed sensor, and calculates a right wheel acceleration, which is the wheel acceleration of the right wheel, based on the detection value of the right wheel speed sensor. The computer detects unevenness of the road surface based on the left wheel acceleration and the right wheel acceleration. When the computer detects unevenness of the road surface, based on information related to the maximum value of the left wheel acceleration and information related to the maximum value of the right wheel acceleration in a predetermined period triggered by counting the elapsed time of the detection of the unevenness of the road surface, it determines whether the unevenness of the road surface is a specific step that is not a repair target of the road surface.

Effect of the Invention

[0007] According to the present invention, based on information related to the maximum value of the wheel acceleration of each of the left and right wheels in the same predetermined period (constant period) for the left and right wheels, it is determined whether the detected unevenness of the road surface is a specific step. Information related to the maximum value is, for example, the magnitude of the maximum value or the time point (time) when the wheel acceleration becomes the maximum value. When the vehicle passes through a specific step such as a joint of a bridge, the left and right wheels are likely to change simultaneously and with the same magnitude. That is, the computer can determine whether the unevenness of the road surface is a specific step by referring to information related to the maximum value within a predetermined period, for example, the left and right maximum values and / or the acquisition times of the left and right maximum values. According to the present invention, it is possible to classify a specific step and unevenness that is not so, and it is possible to facilitate the user's judgment on the necessity of road surface repair.

Brief Description of the Drawings

[0008] [Figure 1] It is a conceptual diagram showing the configuration of the road surface condition detection device of the present embodiment. [Figure 2]This flowchart shows an example of the control of the road surface condition detection device according to this embodiment. [Figure 3] This is a time chart showing an example of the variation in wheel acceleration of each wheel in this embodiment. [Figure 4] This is a time chart showing an example of the variation in wheel acceleration of each wheel in this embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, a road surface condition detection device 1, which is one embodiment of the present invention, will be described in detail with reference to the figures. In addition to the embodiments described below, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

[0010] As shown in Figure 1, the road surface condition detection device 1 of this embodiment includes a left wheel speed sensor 2, a right wheel speed sensor 3, and a computer 4. The left wheel speed sensor 2 is provided for the left wheel 91 and detects the wheel speed of the left wheel 91. The right wheel speed sensor 3 is provided for the right wheel 92, which is positioned opposite the left wheel 91 in the left-right direction, and detects the wheel speed of the right wheel 92. The left wheel 91 and the right wheel 92 are positioned at the same location in the front-rear direction of the vehicle. In other words, as in this embodiment, if the vehicle is a four-wheeled vehicle with left and right front wheels and left and right rear wheels, then if the left wheel 91 is the left front wheel, then the right wheel 92 is the right front wheel, and if the left wheel 91 is the left rear wheel, then the right wheel 92 is the right rear wheel. In this description, the left wheel 91 is the left front wheel and the right wheel 92 is the right front wheel.

[0011] Computer 4 comprises one or more processors 41 and one or more memories 42. Computer 4 may be composed of multiple computers that can communicate with each other. Computer 4 includes an on-board computer installed in the vehicle. Communication within the vehicle is performed by CAN (car area network or controllable area network). Computer 4 transmits acquired road surface information to an external server or the like via wireless communication.

[0012] Computer 4 receives the detection values ​​from the left wheel speed sensor 2 and the right wheel speed sensor 3. Based on the detection value from the left wheel speed sensor 2, Computer 4 calculates the left wheel acceleration, which is the wheel acceleration of the left wheel 91, and based on the detection value from the right wheel speed sensor 3, it calculates the right wheel acceleration, which is the wheel acceleration of the right wheel 92. Wheel acceleration can be calculated by taking the time derivative of the wheel velocity.

[0013] Computer 4 detects road surface irregularities based on the calculated left wheel acceleration and right wheel acceleration. In this embodiment, when detecting road surface irregularities, Computer 4 determines (detects) that there are irregularities on the road surface if the absolute value of at least one of the left wheel acceleration and right wheel acceleration exceeds a predetermined threshold (Const). Since the road surface irregularities detected here are the irregularities that are subject to determination as to whether or not they are specific steps, Computer 4 detects inputs that are sufficiently large (inputs that exceed the threshold) as irregularities subject to determination.

[0014] When computer 4 detects an irregularity in the road surface, it determines whether the detected irregularity is a specific step that does not require road surface repair, based on information related to the maximum value of the left wheel acceleration and information related to the maximum value of the right wheel acceleration during a predetermined period in which the detection of the irregularity in the road surface triggered the counting of elapsed time.

[0015] Computer 4 stores time-series data of wheel acceleration for each of the left and right wheels (see Figures 3 and 4). When Computer 4 detects unevenness in the road surface (the presence of relatively large unevenness in the road surface), it searches a predetermined period from the time the wheel speed that was the detection element was acquired until a predetermined time has elapsed, and searches for the maximum value of the left and right wheel acceleration from the time-series data of each wheel. From the stored calculation data (time-series data), Computer 4 extracts the maximum value of the wheel acceleration within the predetermined period for each of the left and right wheels, and the time when that maximum value was reached.

[0016] Computer 4 calculates the maximum value difference, which is the difference between the maximum value of the left wheel acceleration and the maximum value of the right wheel acceleration within a predetermined period. The maximum value difference can be any value that represents the difference between the maximum values ​​of the left and right wheels, and may be the value obtained by subtracting the maximum value of one from the maximum value of the other, or the value obtained by dividing the maximum value of one by the maximum value of the other. In the former case, the closer the calculated value is to 0, the closer the two values ​​will be, and in the latter case, the closer the calculated value is to 1, the closer the two values ​​will be. In this example, the latter is used, and Computer 4 calculates the ratio of the maximum value of the left wheel acceleration and the right wheel acceleration to the maximum value of one of the left wheel accelerations (hereinafter also referred to as the maximum value ratio) as the maximum value difference.

[0017] Furthermore, computer 4 calculates the maximum time difference, which is the time difference between the point in time when the left wheel acceleration reaches its maximum value and the point in time when the right wheel acceleration reaches its maximum value within a predetermined period. Based on the maximum time difference and the maximum time difference, computer 4 determines whether or not the unevenness of the road surface is a specific step.

[0018] The closer the ratio of the maximum values ​​within a given period is to 1 (the smaller the difference between the maximum value on the left and the maximum value on the right), that is, the closer the maximum values ​​on the left and right within a given period, the more likely it is that the left and right wheels traveled over the same single bump or uneven surface. Specific bumps, such as bridge joints, extend in a similar shape in the direction of the road width, intersecting (for example, perpendicular to) the direction of road extension, and it is highly likely that the left and right wheels traveling over them will fluctuate (react) similarly. In other words, if the maximum values ​​of wheel acceleration within a given period are close for the left and right wheels, it is highly likely that this is the result of traveling over a specific bump or uneven surface. Therefore, the computer 4 has set one of the conditions for determining that a bump or uneven surface is a specific bump or uneven surface: the difference between the maximum values ​​is less than a predetermined threshold.

[0019] Furthermore, the smaller the maximum time difference, the more likely it is that the left and right wheels traveled over the uneven surface at similar timings. In other words, the smaller the maximum time difference, the more likely it is that the left and right wheels traveled over a single common uneven surface. A single common uneven surface is likely to be a specific step extending in the width direction of the road. Therefore, computer 4 has set one of the conditions for determining that the uneven surface is a specific step: the maximum time difference being less than a predetermined threshold time.

[0020] The information related to the maximum value may consist only of the maximum value itself, or only of the time when the maximum value was reached. Computer 4 may determine that the unevenness is a specific step if the difference in maximum values ​​within a predetermined period is less than a threshold, or it may determine that the unevenness is a specific step if the time difference between maximum values ​​is less than a threshold time. In this way, computer 4 may determine whether or not the unevenness is a specific step based on at least one of the difference in maximum values ​​and the time difference between maximum values. However, using both determination conditions will result in a more accurate determination.

[0021] Furthermore, if the second largest value among the maximum values ​​of wheel acceleration is referred to as the "second maximum value," the computer 4 may also calculate the maximum value time difference, which is the time difference between the time when the left wheel acceleration reaches the second maximum value and the time when the right wheel acceleration reaches the second maximum value within a predetermined period, and determine whether or not the unevenness is a specific step based on the calculated maximum value time difference. A maximum value is recognized as a single peak in a section in which wheel acceleration of a predetermined value (for example, predetermined value = 0) or higher is continuously detected, and the maximum value of that peak (the value of the peak, the extreme value, the maximum value) is the value of that peak. The predetermined value may be a value greater than 0. The computer 4 compares the maximum values ​​of each peak within the predetermined period, and takes the largest value as the maximum value (which can also be called the first maximum value), and the second largest value as the second maximum value.

[0022] Computer 4, similar to when acquiring information related to the maximum value, extracts from the stored calculation data (time-series data) the second maximum value of wheel acceleration and the time when that second maximum value occurred for each of the left and right wheels within a predetermined period. Computer 4 calculates the time difference of the maximum value by subtraction. According to experimental data for a specific step, if the difference between the time difference of the maximum value and the time difference of the maximum value (specific time difference) is less than a predetermined threshold time, there is a high probability that the unevenness is a specific step. Therefore, if the specific time difference is less than a predetermined threshold, Computer 4 may determine that the unevenness is a specific step.

[0023] Furthermore, the above theory regarding maximum values ​​can also be applied to minimum values. The relationship between wheel acceleration (vertical axis) and time (horizontal axis) becomes a waveform, and the wheel acceleration can also be a negative value (see Figures 3 and 4). When the left and right wheels travel over a specific step, the time difference between the minimum values ​​of the left and right wheels tends to be small. Therefore, computer 4 may further consider the time difference between the minimum values ​​to determine whether or not the unevenness is a specific step. In other words, computer 4 calculates the time difference between the point in time when the left wheel acceleration is at its minimum and the point in time when the right wheel acceleration is at its minimum within a predetermined period. Based on the time difference between the minimum values, computer 4 may determine whether or not the unevenness of the road surface is a specific step.

[0024] Furthermore, if the second smallest value among the wheel acceleration localities is called the "second local minimum," the computer 4 may calculate the local minimum time difference, which is the time difference between the time when the left wheel acceleration reaches the second local minimum and the time when the right wheel acceleration reaches the second local minimum within a predetermined period. The computer 4 may also determine whether or not the unevenness is a specific step based on the calculated local minimum time difference. A local minimum is defined as the minimum value (bottom value, extreme value, local minimum value) of a valley, where a section in which wheel acceleration below a predetermined value (for example, predetermined value = 0) is continuously detected is recognized as a single valley. The predetermined value may be a value less than 0. The computer 4 compares the minimum values ​​of each valley within the predetermined period, takes the smallest value as the minimum value (which can also be called the first local minimum), and the second smallest value as the second local minimum.

[0025] According to experimental data for specific steps, if the difference between the minimum time difference and the local minimum time difference (the specific time difference on the minimum side) is less than a predetermined threshold time, there is a high probability that the unevenness is a specific step. Therefore, computer 4 may determine that the unevenness is a specific step if the specific time difference is less than a predetermined threshold.

[0026] In this way, computer 4 extracts specific values ​​of wheel acceleration (maximum value, minimum value, second maximum value, second minimum value) within a predetermined period from the time-series data of wheel acceleration, and obtains information on the magnitude of the values ​​and the time of day. Computer 4 calculates the difference (percentage) and time difference between the specific values ​​on the left and right sides, and uses the calculation results as a determination factor.

[0027] (Control example) An example of control will be explained with reference to Figures 2, 3, and 4. Computer 4 obtains the wheel acceleration for each of the left and right wheels 91 and 92 by calculation (S1). Based on the acceleration of each of the left and right wheels, Computer 4 determines whether or not there has been a large input (S2). In this example, Computer 4 determines whether or not the absolute value of the acceleration of at least one of the left or right wheels exceeds a predetermined threshold. If the absolute value of the wheel acceleration exceeds the threshold, it is determined that there has been a large input (S2: Yes), and a timer that measures a predetermined period is started (S3). If the absolute value of the wheel acceleration is less than or equal to the threshold, it is determined that there is no large input (S2: No), and it is determined that there is no specific step on the road surface (S8). This calculation control is a calculation control that uses a window function that calculates only a predetermined period.

[0028] Computer 4 determines when the timer counts time to a predetermined threshold T th1 If the threshold T is reached (S4: Yes), various specific values ​​are extracted (detected) from the time-series data of wheel acceleration for each wheel within a predetermined period. The specific values ​​here are the maximum value, minimum value, second maximum value, and second minimum value. th1 If the value has not been reached (S4: No), computer 4 continues to calculate the wheel acceleration (S41).

[0029] Based on the information related to the extracted specific values, computer 4 calculates the following equations (1) to (7). T maxd is the maximum value time difference, and T maxr is the time when the right wheel acceleration reaches the maximum value, and T maxl is the time when the left wheel acceleration reaches the maximum value. T 2ad is the extreme value time difference, and T 2ar is the time when the right wheel acceleration reaches the second extreme value, and T 2al is the time when the left wheel acceleration reaches the second extreme value. TΔ1 is the specific time difference on the maximum value side of the wheel acceleration. T mind is the minimum value time difference, and T minr is the time when the right wheel acceleration reaches the minimum value, and T minl is the time when the left wheel acceleration reaches the minimum value. T 2ir is the time when the right wheel acceleration reaches the second minimum value, and T 2il is the time when the left wheel acceleration reaches the second minimum value. T 2id is the minimum value time difference. TΔ2 is the specific time difference on the minimum value side of the wheel acceleration. dV rate is the maximum value difference (maximum value ratio), and dV maxr is the maximum value of the right wheel acceleration, and dV maxl is the maximum value of the left wheel acceleration. T maxd = T maxr - T maxl ·····(1) T 2ad = T 2ar - T 2al ·····(2) TΔ1 = T maxd - T 2ad ·····(3) T mind = T minr - T minl ·····(4) T 2id = T 2ir - T 2il ·····(5) TΔ2 = T mind - T 2id ·····(6) dV rate = dV maxr / rVmaxl ...(7)

[0030] Computer 4 determines that the detected unevenness is a specific step if the predetermined conditions are met (S6: Yes), specifically if all of the following equations (8) to (10) are true, or if all of the following equations (11) to (13) are true (S7). th2 is a threshold for the maximum time difference or minimum time difference, T th3 This is a threshold for the maximum or minimum time difference. th1 This is the lower limit of the maximum difference, DV th2 This is the upper limit of the maximum difference. Each threshold is set in advance based on experimental results, etc. If the predetermined conditions are not met (S6: No), the computer 4 determines that the detected irregularities are not specific steps (S8). Figure 3 is a graph focusing on the maximum value and the second maximum value, and Figure 4 is a graph focusing on the minimum value and the second minimum value. |T maxd | <T th2 ...(8) |TΔ1| <T th3 ...(9) DV th1 <dV rate <DV th2 ...(10) |T mind | <T th2 ...(11) |TΔ2| <T th3 ...(12) DV th1 <dV rate <DV th2 ...(13)

[0031] (Effects of this embodiment) According to this embodiment, whether or not a detected road surface irregularity is a specific step is determined based on information related to the maximum values ​​of the left and right wheel accelerations during the same predetermined period (a certain period) for both the left and right wheels. In this embodiment, the information related to the maximum value is the magnitude of the maximum value and the time when the wheel acceleration reached its maximum value. When a vehicle passes over a specific step, such as a bridge joint, the left and right wheels are likely to fluctuate simultaneously and by the same magnitude. In other words, the computer can determine whether or not a road surface irregularity is a specific step by referring to the information related to the maximum value within the predetermined period. According to this embodiment, it is possible to classify irregularities into specific steps and those that are not, making it easier for the user to determine whether or not road surface repair is necessary.

[0032] Computer 4 can accurately determine unevenness by using the maximum value difference (a concept including the maximum value ratio) and the maximum value time difference. Furthermore, Computer 4 can determine unevenness with even greater accuracy by using the minimum value time difference, the maximum value time difference, or the minimum value time difference. Experiments have shown that in determining specific steps such as joints and road surface roughness such as potholes, not only information related to the maximum value but also the minimum value time difference, maximum value time difference, and minimum value time difference described above function as determination elements. By using a combination of these determination elements, the accuracy of unevenness determination can be improved. Based on the shape characteristics of specific steps that extend intersecting the road, information related to the minimum value, information related to the second maximum value, and information related to the second minimum value can also be used as determination elements, similar to the theory that information related to the maximum value functions as a determination element. In addition, Computer 4 may be configured to change each threshold used in various determinations according to the vehicle speed. This allows for more accurate determinations that are in line with the vehicle's condition. For example, if there are multiple extreme values ​​of the same value in a single peak or valley, the computer 4 may be set to consider the one occurring at the earliest point in time as the extreme value of that peak or valley. [Explanation of symbols]

[0033] 1...Road surface condition detection device, 2...Left wheel speed sensor, 3...Right wheel speed sensor, 4...Computer, 91...Left wheel, 92...Right wheel.

Claims

1. A left wheel speed sensor is provided for the left wheel and detects the wheel speed of the left wheel, A right wheel speed sensor is provided for the right wheel, which is positioned opposite the left wheel in the left-right direction, and detects the wheel speed of the right wheel. A computer that receives the detected value from the left wheel speed sensor and the detected value from the right wheel speed sensor, Equipped with, The aforementioned computer, Based on the detected value of the left wheel speed sensor, the left wheel acceleration, which is the wheel acceleration of the left wheel, is calculated, and based on the detected value of the right wheel speed sensor, the right wheel acceleration, which is the wheel acceleration of the right wheel, is calculated. When road surface irregularities are detected based on the left wheel acceleration and the right wheel acceleration, the system is configured to determine whether the detected road surface irregularities are specific steps that are not subject to road surface repair, based on information related to the maximum value of the left wheel acceleration and information related to the maximum value of the right wheel acceleration during a predetermined period triggered by the detection of road surface irregularities. The aforementioned computer, The difference between the maximum value of the left wheel acceleration and the maximum value of the right wheel acceleration during the predetermined period is calculated. The maximum time difference, which is the time difference between the point in time when the left wheel acceleration reaches its maximum value and the point in time when the right wheel acceleration reaches its maximum value within the predetermined period, is calculated. Based on the aforementioned maximum difference and the aforementioned maximum time difference, it is determined whether or not the unevenness of the road surface is the aforementioned specific step. Road surface condition detection device.

2. If the second largest value among the maximum values ​​of wheel acceleration within the predetermined period is defined as the second maximum value, The aforementioned computer further, Based on the time difference between the point in time when the left wheel acceleration reaches the second maximum value and the point in time when the right wheel acceleration reaches the second maximum value within the predetermined period, it is determined whether or not the unevenness of the road surface is the specific step. The road surface condition detection device according to claim 1.

3. The aforementioned computer further, Based on the minimum time difference, which is the time difference between the time when the left wheel acceleration reaches its minimum value and the time when the right wheel acceleration reaches its minimum value within the predetermined period, it is determined whether or not the unevenness of the road surface is the specified step. A road surface condition detection device according to claim 1 or 2.

4. A left wheel speed sensor is provided for the left wheel and detects the wheel speed of the left wheel, A right wheel speed sensor is provided for the right wheel, which is positioned opposite the left wheel in the left-right direction, and detects the wheel speed of the right wheel. A computer that receives the detected value from the left wheel speed sensor and the detected value from the right wheel speed sensor, Equipped with, The aforementioned computer, Based on the detected value of the left wheel speed sensor, the left wheel acceleration, which is the wheel acceleration of the left wheel, is calculated, and based on the detected value of the right wheel speed sensor, the right wheel acceleration, which is the wheel acceleration of the right wheel, is calculated. When road surface irregularities are detected based on the left wheel acceleration and the right wheel acceleration, the system is configured to determine whether the detected road surface irregularities are specific steps that are not subject to road surface repair, based on information related to the maximum value of the left wheel acceleration and information related to the maximum value of the right wheel acceleration during a predetermined period triggered by the detection of road surface irregularities. The aforementioned computer further, Based on the minimum time difference, which is the time difference between the time when the left wheel acceleration reaches its minimum value and the time when the right wheel acceleration reaches its minimum value within the predetermined period, it is determined whether or not the unevenness of the road surface is the specified step. Road surface condition detection device.

5. If the second smallest value among the minimum values ​​of wheel acceleration within the predetermined period is defined as the second minimum value, The aforementioned computer further, Based on the minimum time difference, which is the time difference between the time when the left wheel acceleration reaches the second minimum value and the time when the right wheel acceleration reaches the second minimum value within the predetermined period, it is determined whether or not the unevenness of the road surface is the specific step. The road surface condition detection device according to claim 4.

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