Vehicle-mounted sign retroreflection coefficient detection method and system adaptive to slope road

Abstract

The invention discloses a vehicle-mounted sign retroreflection coefficient detection method and system adaptive to a slope road. When the relative distance between a to-be-detected sign board in a to-be-detected area and a detection vehicle meets a preset shooting distance, the to-be-detected sign board in the to-be-detected area is detected; obtaining road dip angle information, collected by a dip angle sensor in real time, of the detection vehicle at each moment in the driving process in the to-be-detected area; solving a road dip angle in the detection area according to the road dip angle information at each moment; the compensation angle of the detection module is calculated according to the road dip angle, the electric adjusting structure is controlled to adjust the incident angle of the detection module into the target incident angle in real time according to the compensation angle, and the compensated detection module is obtained; using the compensated detection module to photograph a to-be-detected traffic signboard to obtain a to-be-identified signboard image; performing identification processing on the to-be-identified signboard image to obtain a retroreflection brightness coefficient corresponding to the to-be-detected traffic signboard; therefore, the effectiveness and accuracy of detection can still be maintained under complex road conditions.

Description

Technical Field

[0001] The invention relates to the technical field of road detection, and in particular to a method and system for detecting the retro-reflection coefficient of a vehicle-mounted sign on an adaptive slope road. Background Art

[0002] The retroreflective coefficient of traffic signs is a key evaluation standard for measuring the safety and reading performance of traffic signs. The effective reading distance of road traffic signs is limited. Therefore, the stronger the retroreflective ability of the retroreflective material on the surface of the sign, the better it can improve the brightness of the sign, optimize sign recognition, and improve sight distance.

[0003] In general vehicle-mounted sign retroreflection coefficient detection systems, when the detection system is in some special road scenes, it is limited by external physical conditions, resulting in poor detection results. For example, in general vehicle-mounted implementations, the upper sign detection module is equipped with a light source and a camera at a fixed angle. When the detection vehicle is traveling on a steep slope (including uphill and downhill), the optical axis of the light source cannot form an intersection with the retroreflector axis of the sign, and may even deviate from the sign, resulting in the light spot area of ​​the light source being unable to effectively illuminate the sign or the camera being unable to capture the effective detection area of ​​the sign, and the conditions for effective measurement of the sign cannot be met, which may result in erroneous measurement of the sign or missed detection of the sign. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive sloping road. When a vehicle is traveling on a complex road condition with an uneven road and a large road inclination, and the detection conditions are limited, the road inclination is calculated based on a inclination sensor, and the incident angle of the light axis of the detection module is adjusted in real time during the vehicle's driving, thereby not affecting the detection accuracy of the detection module.

[0005] To achieve the above objectives, this application provides the following solutions: In a first aspect, the present application provides a method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road, which respectively initializes the inclination sensor installed on the top of the detection vehicle, the horizontal angle between the detection module and the road, and when the detection vehicle is driving on the road in the area to be detected, the method includes the following steps: S1. When the relative distance between the sign to be detected in the area to be detected and the detection vehicle meets the preset shooting distance, the road inclination information at each moment during the driving process of the detection vehicle in the area to be detected collected in real time by the inclination sensor is obtained; S2. Calculate the road inclination angle in the detection area according to the road inclination angle information at each moment; S3, calculating the compensation angle of the detection module according to the road inclination angle, and controlling the electric adjustment structure according to the compensation angle to adjust the incident angle of the detection module to the target incident angle in real time, so as to obtain a compensated detection module; S4, using the compensated detection module to take a photo of the traffic sign to be detected to obtain an image of the sign to be identified; S5. Perform image recognition processing on the traffic sign to be detected to obtain the retroreflection brightness coefficient corresponding to the traffic sign to be detected.

[0006] In some specific implementation schemes, the process of initializing the tilt sensor and detecting the horizontal angle between the module and the road is as follows: When the inspection vehicle is stationary, the installation angle of the tilt sensor installed horizontally on the inspection vehicle is adjusted to be parallel to the road, and the incident angle is adjusted to the target incident angle, which is the angle between the optical axis of the light source of the detection module on the top of the inspection vehicle and the axis of the retroreflector of the traffic sign to be inspected above the road and parallel to the road.

[0007] In some specific implementation schemes, the road inclination information includes a pitch angle measurement value, and the specific process of step S2 includes: S21, set the sampling period of the road inclination information, the n pitch angle measurement values ​​collected in each sampling period are stored in a collection data set, denoted as X (X1, ..., Xn); S22, using a first-order filter to perform a filtering process on each pitch angle measurement value in the collected data set to obtain n pre-processed data; S23. Filter the n preprocessed data again using the studentized residual, remove the outliers with excessive deviations, average the remaining data, and obtain the optimal estimated value of the road inclination. The optimal estimated value of the road inclination is used as the road inclination of the detection vehicle in the current area to be detected.

[0008] In some specific implementation schemes, the specific process of the filtering process in step S22 is: The pitch angle measurement values ​​in the collected data set are sequentially input into the first-order filter for preprocessing according to the collection time. The preprocessing process is to weight the pitch angle measurement value at the current collection time and the filter output value output after filtering by the first-order filter at the previous collection time to obtain the filter output value at the current collection time, and use the filter output value at each collection time as the preprocessing data; The calculation method of the first-order filter is: Among them, α represents the filter coefficient, Indicates the pitch angle measurement value at the current acquisition moment. Indicates the filter output value at the last acquisition moment, Indicates the filter output value at the current acquisition moment.

[0009] In some specific implementation schemes, the specific process of step S23 is: S231, calculate the average value of n preprocessed data And the residual corresponding to each preprocessed data; S232, calculating the standard deviation of n preprocessed data according to the residual of each preprocessed data; S233, calculating the studentized residual corresponding to each preprocessed data according to the standard deviation and the residual of each preprocessed data; S234, traverse n pre-processed data, and determine whether the studentized residual corresponding to each pre-processed data exceeds a preset threshold. If so, remove the pre-processed data, and if not, save it in the road inclination angle data set; S235. Calculate the average value of the data in the road inclination data set to obtain the optimal estimated value of the road inclination.

[0010] In some specific implementation schemes, the electric adjustment structure is used to drive the optical axis of the light source to move, and the specific process of step S3 is: S31, obtaining the actual angle between the light source axis of the detection module and the horizontal plane according to the sum of the compensation angle and the target incident angle; S32, inputting the actual angle and the target incident angle into the established mathematical model of the motion relationship between the travel distance of the electric adjustment structure and the road inclination angle, and calculating the moving distance a of the electric adjustment structure; S33. Determine the direction of the ramp on which the inspection vehicle is traveling according to the road inclination angle, and control the electric adjustment structure to adjust the incident angle of the light source optical axis to the target incident angle according to the ramp direction and the moving distance a.

[0011] In some specific implementation schemes, the electric adjustment structure includes a stepper motor with a lead screw, and a slider that moves with the lead screw and drives the optical axis of the light source to move. The mathematical model of the motion relationship in step S32 is: Where L is the length of the light source mounting plate whose mounting direction is parallel to the light source optical axis, ω is the actual angle, and β is the target incident angle. Indicates the minimum acute angle of the slider cross section.

[0012] In some specific implementation schemes, in step S33, the process of determining the direction of the ramp on which the detection vehicle is traveling according to the road inclination angle is as follows: When the road inclination angle is positive, the ramp direction is uphill, and when the road inclination angle is negative, the ramp direction is downhill. When the inspection vehicle is traveling uphill, the screw rod drives the slider to move forward a distance a in the direction of the inspection vehicle. When the inspection vehicle is traveling downhill, the screw rod drives the slider to move backward a distance a in the opposite direction of the inspection vehicle.

[0013] In a second aspect, the present application provides a vehicle-mounted sign retroreflection coefficient detection system for adaptive slope roads, comprising an observation module, a detection module, a tilt sensor, and an electric adjustment structure for adjusting the incident angle of the detection module, respectively connected to the control module for communication, wherein: The observation module includes a camera and a radar. The optical axes of the camera and the radar are installed on the roof of the inspection vehicle parallel to the length direction of the inspection vehicle to capture images of the area to be inspected. The detection module includes a detection camera, a light source for illumination, and a mounting bracket for fixing the detection camera and the light source, and the angle between the optical axis of the light source and the axis of the retroreflector of the traffic sign to be detected is adjusted to the target incident angle; The inclination sensor is installed horizontally on the top of the inspection vehicle to measure the road inclination information at any time when the inspection vehicle is driving on the road; The electric adjustment structure is installed on the luggage rack on the top of the inspection vehicle and is movably connected to the mounting bracket, and is used to drive the mounting bracket to move under the control of the control module so that the incident angle between the optical axis of the light source and the axis of the retroreflector of the traffic sign to be inspected remains unchanged; The control module is used to execute the vehicle-mounted sign retroreflection coefficient detection method for an adaptive slope road as described in the first aspect.

[0014] In some specific embodiments, the electric adjustment structure includes a stepper motor with a lead screw and an encoder, a lead screw guide rail is fixed on the top of the detection vehicle, a wedge-shaped slider is installed on the lead screw guide rail, the cross-section of the wedge-shaped slider is an isosceles right triangle with an acute angle of σ, and the rotation of the lead screw drives the wedge-shaped slider to move back and forth along the lead screw guide rail. The wedge-shaped slider is connected to one end of the mounting bracket through a bearing, thereby raising or lowering the incident angle of the optical axis of the light source.

[0015] The inventive concept of this application is: When a vehicle is traveling on a complex road with an uneven road and a large road inclination, it is likely that the optical axis of the light source of the detection module will not be able to form an intersection with the axis of the retroreflector of the traffic sign, or even deviate from the sign, thereby failing to effectively shoot the sign and affecting the detection of the retroreflection coefficient of the sign. Therefore, when using the vehicle-mounted retroreflection coefficient detection, it is required that when the detection vehicle is traveling on a straight road and reaches the shooting point, the angle between the optical axis of the light source of the detection module above the detection vehicle and the axis of the retroreflector of the sign must be a specific angle, which is called the incident angle β, and the incident angle needs to remain unchanged, with an absolute value of β of 4 degrees. The observation angle α (the angle between the optical axis of the light source and the optical axis of the camera) is determined by the installation angle between the light source and the camera during installation, and the observation angle is 0.2 degrees.

[0016] Therefore, in order to achieve a constant incident angle and meet the detection requirements of the detection module, when the detection vehicle is traveling on the road to be detected, the inclination sensor calculates the road inclination of the current slope of the road the detection vehicle is traveling on. If the road inclination exceeds the set threshold, the electric adjustment structure is driven to lift the upper detection module to compensate for the corresponding inclination, so that the optical axis of the light source can always intersect with the axis of the retroreflector of the signboard, and the absolute value of the incident angle β formed between them always remains at 4 degrees.

[0017] The present invention has the following beneficial effects compared with the prior art: The present invention takes into account that the road slope will often change during the driving of the inspection vehicle, resulting in inconsistent conditions for measuring the retroreflection coefficient of the sign. Based on the measurement of the road inclination by the inclination sensor, the angle between the inspection module and the axis of the retroreflective body of the sign can be adjusted in real time to ensure the consistency of the shooting conditions, reduce erroneous detection and missed detection of signs, and improve the comprehensiveness of sign detection and adaptability to different complex working conditions; the inspection vehicle can still maintain the effectiveness and accuracy of detection under complex road conditions such as uneven roads and large road inclinations.

[0018] The invention is suitable for high vehicle speed and large slope, with high measurement frequency, fast adjustment speed, good real-time performance and continuous slope. The incident angle can be adjusted in real time during the detection process without slowing down or stopping, which does not affect the detection. It is proposed to use a first-order low-pass filter and studentized residuals for data cleaning to effectively avoid measurement deviation and jump errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A structural block diagram of a vehicle-mounted sign retroreflection coefficient detection system for an adaptive slope road provided by an embodiment of the present invention; Figure 2 A flow chart of a method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road provided by an embodiment of the present invention; Figure 3 A side view of a straight road provided by an embodiment of the present invention; Figure 4 A side view of a slope road provided by an embodiment of the present invention; Figure 5 A schematic diagram of a mathematical model provided for an embodiment of the present invention; Figure 6 A schematic diagram of a mathematical model of a slider after sliding provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0022] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0023] Additionally, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness.One of ordinary skill in the art will recognize that various changes and modifications may be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0024] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0025] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0026] Example 1 like Figure 1 As shown, this embodiment provides a vehicle-mounted sign retroreflective brightness coefficient detection system, including a mileage measurement module, an observation module, a detection module, a tilt sensor, and an electric adjustment structure for adjusting the incident angle of the detection module, which are respectively connected to the control module for communication. The observation module includes a camera and a radar. The optical axes of the camera and the radar are installed on the roof of the inspection vehicle parallel to the length direction of the inspection vehicle to capture images of the area to be inspected. The detection module includes a detection camera, a light source for illumination, and a mounting bracket for fixing the detection camera and the light source. The angle between the optical axis of the light source (i.e., the optical axis of the light source) and the axis of the retroreflector of the traffic sign to be detected is adjusted to the target incident angle; the detection module in this embodiment specifically refers to an upper sign detection module for photographing traffic signs above the road area to be detected; the camera and the light source in the upper sign detection module are fixed on the mounting bracket at a determined interval and angle. In this embodiment, the angle between the optical axis of the camera and the optical axis of the light source is 0.2 degrees, and the mounting bracket is installed on an electric adjustment structure.

[0027] The inclination sensor is installed horizontally on the top of the inspection vehicle to measure the road inclination information at any time when the inspection vehicle is driving on the road; The tilt sensor is installed horizontally on the inspection vehicle. The tilt sensor includes a high-precision gyroscope, an accelerometer, and a geomagnetic field sensor. The gyroscope collects the vehicle's three-axis angular velocity, and the accelerometer collects the vehicle's three-axis acceleration. The tilt sensor can directly measure the three-axis angular velocity, three-axis acceleration, pitch angle, heading angle and other information of the inspection vehicle at any time. The integration of multiple sensors can greatly overcome the errors and uncertainties caused by a single sensor. The longitudinal detection accuracy of the tilt sensor is 0.001 degrees, that is, the pitch angle detection accuracy in the longitudinal direction of the inspection vehicle is 0.001 degrees, the return rate is 200hHZ, it can adapt to rapidly changing dynamic environments, and the longitudinal tilt detection range is plus or minus 90 degrees.

[0028] The electric adjustment structure is installed on the luggage rack on the top of the inspection vehicle and is movably connected to the mounting bracket, and is used to drive the mounting bracket to move under the control of the control module so that the incident angle between the optical axis of the light source and the axis of the retroreflector of the traffic sign to be inspected remains unchanged; The electric adjustment structure includes a stepper motor with a lead screw and an encoder. A lead screw guide rail is fixed on the top of the detection vehicle. A wedge-shaped slider is installed on the lead screw guide rail. The cross-section of the wedge-shaped slider is an isosceles right triangle with an acute angle of σ. The rotation of the lead screw drives the wedge-shaped slider to move back and forth along the lead screw guide rail. The wedge-shaped slider is connected to one end of the mounting bracket through a bearing, thereby raising or lowering the incident angle of the optical axis of the light source.

[0029] The mileage measurement module is installed on the left rear wheel hub of the inspection vehicle to measure the road mileage traveled by the inspection vehicle; The control module is used to execute the vehicle-mounted sign retroreflection coefficient detection method for an adaptive slope road as described in the first aspect.

[0030] The control module executes a method for detecting the vehicle-mounted sign retroreflection coefficient of an adaptive slope road according to the image and point cloud data of the area to be detected, the sign to be detected, the mileage of the detected vehicle road, the road inclination information and other data received from each module.

[0031] Example 2 like Figure 2 As shown, based on Example 1 Figure 1 The present embodiment provides a method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road. The method specifically comprises the following steps: Step 1: Install the tilt sensor on the inspection vehicle and adjust the installation position Initialize the inclination sensor installed on the top of the inspection vehicle, the horizontal angle between the detection module and the road respectively. When the inspection vehicle is stationary, adjust the installation angle of the inclination sensor installed horizontally on the inspection vehicle to be parallel to the road, and adjust the incident angle to the target incident angle. The incident angle is the angle between the optical axis of the light source of the detection module on the top of the inspection vehicle and the axis of the retroreflector of the traffic sign to be detected above the road and parallel to the road. Specifically, the inspection vehicle is turned off and parked on a horizontal road surface, and the inclination sensor is installed horizontally on the inspection vehicle. According to the measured installation pitch angle and installation roll angle, adjust the installation angle of the inclination sensor until the current installation pitch angle and installation roll angle are both zero. After the static adjustment is completed, drive the inspection vehicle to travel at a constant speed on a straight and horizontal road, and adjust the installation yaw angle in real time until it is zero.

[0032] The installation pitch angle refers to the angle between the tilt sensor (along the length of the vehicle) and the ground (horizontal plane). The installation roll angle refers to the angle between the tilt sensor (along the width of the vehicle) and the ground (horizontal plane). The yaw angle refers to the angle between the forward direction of the tilt sensor and the detection vehicle (along the length of the vehicle).

[0033] Step 2: When the inspection vehicle is driving on the road in the area to be inspected, the inclination sensor collects the road inclination information of the vehicle at different times in real time. When the inspection vehicle is driving on the inspection road, the inclination sensor detects the inclination θ of the current road at a high frequency and sends it to the control module continuously. When the inspection vehicle is moving at a constant speed or stationary on a horizontal road, θ is 0 degrees. However, if the road is uneven, has potholes, and the car has a certain degree of bumps and vibrations during driving, the output of the inclination sensor will fluctuate to a certain extent, and the sampled value needs to be preprocessed first. The specific steps include: S1. When the relative distance between the sign to be detected in the area to be detected and the detection vehicle meets the preset shooting distance, the road inclination information at each moment during the driving process of the detection vehicle in the area to be detected collected in real time by the inclination sensor is obtained; The relative distance between the signboard to be detected and the inspection vehicle is obtained by taking image data and point cloud data of the road area to be detected by the observation module on the top of the inspection vehicle. The image data of the road area to be detected is input into the pre-trained first deep learning detection model, and combined with the point cloud data, the relative distance between the signboard to be detected and the inspection vehicle in the road area to be detected is obtained. The first deep learning detection model adopts the target detection model based on yolov8, whose lightweight and real-time performance can ensure good detection effect and detection speed under resource-constrained conditions.

[0034] When the inspection vehicle is traveling on the road to be inspected, the radar and camera of the observation module shoot the area to be inspected at a fixed frequency. The fixed frequency can be freely set by the control module to trigger the distance or time interval. In this embodiment, a fixed time interval is used to trigger the acquisition, and the acquisition interval is 200ms. When the inspection vehicle is traveling on the road to be inspected, the control module triggers the camera and radar in the observation module at a fixed frequency to simultaneously capture the two-dimensional image data and point cloud data of the road area to be inspected.

[0035] When the relative distance between the sign to be detected in the detection area and the detection vehicle meets the preset shooting distance, the detection module is triggered to take continuous photos of the sign with and without light source illumination, and two continuous frame images are obtained for subsequent recognition. Because the photos taken need to meet the intersection of the optical axis and the reverse body axis, the following steps are performed: S2. Calculate the road inclination angle in the detection area according to the road inclination angle information at each moment; The road inclination information includes a pitch angle measurement value. The specific process of step S2 includes: S21, set the sampling period of the road inclination information, the n pitch angle measurement values ​​collected in each sampling period are stored in a collection data set, denoted as X (X1, ..., Xn); S22, using a first-order filter to perform a filtering process on each pitch angle measurement value in the collected data set to obtain n pre-processed data; The specific process of the primary filtering process in step S22 is as follows: The pitch angle measurement values ​​in the collected data set are sequentially input into the first-order filter for preprocessing according to the collection time. The preprocessing process is to weight the pitch angle measurement value at the current collection time and the filter output value output after filtering by the first-order filter at the previous collection time to obtain the filter output value at the current collection time, and use the filter output value at each collection time as the preprocessing data; The calculation method of the first-order filter is: in, Represents the filter coefficient, filter coefficient The smaller it is, the smoother the result and the better the anti-interference performance. It can effectively remove abnormal angle values ​​caused by rapid changes in inclination angle caused by road bumps and acceleration and deceleration of the detection vehicle. Indicates the pitch angle measurement value at the current acquisition moment. Indicates the filter output value at the last acquisition moment, Indicates the filter output value at the current acquisition moment.

[0036] When the inspection vehicle is traveling on the inspection road, the inclination sensor detects the inclination angle θ of the current road at a high frequency and sends it to the control module continuously. When the inspection vehicle is moving at a constant speed or stationary on a horizontal road, θ is 0 degrees. However, the road is uneven, has potholes, and the car has a certain degree of bumps and vibrations during driving. The output of the inclination sensor will fluctuate to a certain extent, and the sampled values ​​need to be preprocessed first. Therefore, this embodiment selects the pitch angle data within a certain period of time based on the pitch angle measurement value of the inclination sensor, and calculates its average value as the road inclination angle of the test area.

[0037] Set every 100ms as a sampling cycle, and n pitch angle values ​​can be obtained in one cycle. First, use a first-order filter to pre-process the data to filter high-frequency interference, and use the current sampling value and the last filtering output value for weighting to obtain the current effective filtering value. The sampling time length can be set according to specific needs.

[0038] S23. Filter the n preprocessed data again using the studentized residual, remove the outliers with excessive deviations, average the remaining data, and obtain the optimal estimated value of the road inclination. The optimal estimated value of the road inclination is used as the road inclination of the detection vehicle in the current area to be detected.

[0039] The specific process of step S23 is: S231, calculate the average value of n preprocessed data And the residual corresponding to each preprocessed data; S232, calculating the standard deviation of n preprocessed data according to the residual of each preprocessed data; S233, calculating the studentized residual corresponding to each preprocessed data according to the standard deviation and the residual of each preprocessed data; S234, traverse n pre-processed data, and determine whether the studentized residual corresponding to each pre-processed data exceeds a preset threshold. If so, remove the pre-processed data, and if not, save it in the road inclination angle data set; S235. Calculate the average value of the data in the road inclination data set to obtain the optimal estimated value of the road inclination.

[0040] Calculate the mean value and corresponding residual of the preprocessed data, and use the studentized residual to reliably detect outliers to prevent these outliers from adversely affecting the final results. Studentized residuals can capture outliers more sensitively and avoid the "dilution" of the final results by outliers. n data, calculate the average , the formula is: ,in, Represents the i-th angle value after preprocessing.

[0041] Calculate residuals , the formula is , Calculate standard deviation s , the formula is , Compute Studentized Residuals , the formula is .

[0042] If the absolute value of the studentized residual is large, it means that the observation may be an outlier. Remove the outliers with large deviations, and then calculate the average of the remaining data. The optimal estimate of the road inclination angle is obtained through the above method, and the optimal estimate is used as the inclination angle θ of the road where the detection vehicle is currently located.

[0043] S3, calculating the compensation angle of the detection module according to the road inclination angle, and controlling the electric adjustment structure according to the compensation angle to adjust the incident angle of the detection module to the target incident angle in real time, so as to obtain a compensated detection module; According to the calculated road inclination angle θ, the real-time driving motor adjusts the compensation angle of the upper detection module. The compensation angle of the upper detection module is the road inclination angle θ. The incident angle before angle compensation is β, and after adjustment, the incident angle formed by the light source optical axis and the sign retroreflector axis can still be maintained at β. The electric adjustment structure is used to drive the light source optical axis to move. The specific process of step S3 is: S31, obtaining the actual angle between the light source axis of the detection module and the horizontal plane according to the sum of the compensation angle and the target incident angle; S32, inputting the actual angle and the target incident angle into the established mathematical model of the motion relationship between the travel distance of the electric adjustment structure and the road inclination angle, and calculating the moving distance a; The electric adjustment structure includes a stepper motor with a lead screw and a slider that moves with the lead screw and drives the optical axis of the light source to move. The mathematical model of the motion relationship in step S32 is: Where L is the length of the light source mounting plate whose mounting direction is parallel to the light source optical axis, ω is the actual angle, and β is the target incident angle. Indicates the minimum acute angle of the slider cross section.

[0044] S33. Determine the direction of the ramp on which the inspection vehicle is traveling according to the road inclination angle, and control the lead screw of the stepper motor to drive the slider to move a distance a in the corresponding direction according to the ramp direction and the moving distance a, so that the incident angle of the light source optical axis is adjusted to the target incident angle.

[0045] In step S33, the process of determining the direction of the slope on which the detection vehicle is traveling according to the road inclination angle is as follows: When the road inclination angle is positive, the ramp direction is uphill, and when the road inclination angle is negative, the ramp direction is downhill. When the inspection vehicle is traveling uphill, the screw rod drives the slider to move forward a distance a in the direction of the inspection vehicle. When the inspection vehicle is traveling downhill, the screw rod drives the slider to move backward a distance a in the opposite direction of the inspection vehicle.

[0046] In this embodiment, the stepper motor is a stepper motor with a ball screw and an encoder. The slider is a wedge-shaped slider. The maximum speed of the screw can reach 100mm / s, and the repeatability is less than 0.01mm. The encoder is a 12-bit, 2000-line absolute encoder. After the road inclination angle θ is obtained, the calculation module calculates the travel of the screw corresponding to the light source compensation angle, and drives the motor to complete the compensation of the light source optical axis angle.

[0047] like Figure 5-Figure 6 As shown, a wedge-shaped slider is slidably connected to the screw guide rail, and the cross section of the wedge-shaped slider is an isosceles right triangle with an acute angle of σ. The screw rod rotates to drive the wedge-shaped slider to move forward and backward along the linear guide rail. The wedge-shaped slider is connected to one end of the light source bracket through a bearing, thereby raising or lowering the inclination angle of the light source.

[0048] Therefore, it is necessary to solve the relationship between the angle of light source lifting or lowering and the screw stroke: simplify the mathematical model of the above problem and consider the case where the angle β between the light source axis and the sign retroreflector axis is 4 degrees at the initial moment. Figure 5 As shown in the figure, when the road inclination angle is θ, the state after the motor drives the screw rod / slider to travel a distance is as follows Figure 6 .

[0049] The following relationships exist between variables: .

[0050] The relationship with the screw travel distance is Calculate the screw travel distance a Relationship with road inclination: in, Indicates the height difference generated when the slider moves; Indicates the height of the intersection of the light source mounting plate and the wedge-shaped slider from the fixed point of the light source mounting plate at the initial moment; It represents the height of the intersection of the light source mounting plate and the wedge-shaped slider from the fixed point of the light source mounting plate after the slider has traveled a distance; since the light source is fixed on the light source mounting plate, the installation direction of the light source mounting plate is parallel to the optical axis of the light source, so the angle between the light source mounting plate and the horizontal plane is the same as the angle between the light source optical axis and the horizontal plane, a represents the distance the slider has traveled along the guide rail; σ represents the minimum acute angle of the wedge-shaped slider cross section; β represents the initial incident angle; ω represents the actual angle between the light source mounting plate and the horizontal plane after angle compensation; L represents the length of the light source mounting plate. θ is a positive value when going uphill and a negative value when going downhill. The symbol is used to distinguish between the two states of uphill and downhill. Unless otherwise specified, θ in the formula in this article refers to a positive value or an absolute value.

[0051] The distance a that the lead screw needs to travel is calculated from the compensation angle. When the inspection vehicle is traveling uphill, the motor drives the lead screw to move forward a distance, reducing the inclination of the light source's optical axis relative to the horizontal plane. Figure 4 As shown in FIG. 1 , when the inspection vehicle is traveling downhill, the motor drives the lead screw to move backward by a distance a, increasing the inclination of the light source axis relative to the horizontal plane; Figure 3 As shown, when the inspection vehicle travels on a horizontal road, the motor drives the lead screw back to the initial state.

[0052] According to the "Technical Standards for Highway Engineering" and other standards, the road inclination generally does not exceed 10°.

[0053] The screw rod can travel 10 mm in 100 ms. In the present invention, L=150 mm, σ=45°. According to the above formula, it can be calculated that the angle range that can be changed in 100 ms can reach a maximum of about 4°. Before the next shooting, the angle between the light source axis and the axis of the sign retroreflector can be dynamically adjusted in real time according to the road inclination without affecting the next shooting.

[0054] S4, using the compensated detection module to take a photo of the traffic sign to be detected to obtain an image of the sign to be identified; S5. Perform image recognition processing on the traffic sign to be detected to obtain the retroreflection brightness coefficient corresponding to the traffic sign to be detected.

[0055] The focus of this application is on how to adaptively adjust the optical axis of the light source during the detection of the retroreflection coefficient of the sign so that it cannot form an intersection with the retroreflector axis of the sign, and may even deviate from the sign, failing to meet the conditions for effective measurement of the sign, which may cause erroneous measurement of the sign or lead to missed detection of the sign. The specific identification method of the retroreflection coefficient is not limited.

[0056] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0057] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0058] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0059] These computer program instructions can also be loaded onto a computer or other programmable data processing device, and a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. According to the technical essence of the present invention, within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road, characterized in that: Initialize the tilt sensor installed on the top of the inspection vehicle, the horizontal angle between the inspection module and the road respectively. When the inspection vehicle is driving on the road in the area to be inspected, the following steps are included: S1. When the relative distance between the sign to be detected in the area to be detected and the detection vehicle meets the preset shooting distance, the road inclination information at each moment during the driving process of the detection vehicle in the area to be detected collected in real time by the inclination sensor is obtained; S2. Calculate the road inclination angle in the detection area according to the road inclination angle information at each moment; S3, calculating the compensation angle of the detection module according to the road inclination angle, and controlling the electric adjustment structure according to the compensation angle to adjust the incident angle of the detection module to the target incident angle in real time, so as to obtain a compensated detection module; S4, using the compensated detection module to take a photo of the traffic sign to be detected to obtain an image of the sign to be identified; S5. Perform image recognition processing on the traffic sign to be detected to obtain the retroreflection brightness coefficient corresponding to the traffic sign to be detected.

2. The method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road according to claim 1, characterized in that: The process of initializing the tilt sensor and detecting the horizontal angle between the module and the road is as follows: When the inspection vehicle is stationary, the installation angle of the tilt sensor installed horizontally on the inspection vehicle is adjusted to be parallel to the road, and the incident angle is adjusted to the target incident angle, which is the angle between the optical axis of the light source of the detection module on the top of the inspection vehicle and the axis of the retroreflector of the traffic sign to be inspected above the road and parallel to the road.

3. The method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road according to claim 2, characterized in that: The road inclination information includes a pitch angle measurement value. The specific process of step S2 includes: S21, set the sampling period of the road inclination information, the n pitch angle measurement values ​​collected in each sampling period are stored in a collection data set, denoted as X (X1, ..., Xn); S22, using a first-order filter to perform a filtering process on each pitch angle measurement value in the collected data set to obtain n pre-processed data; S23. Filter the n preprocessed data again using the studentized residual, remove the outliers with excessive deviations, average the remaining data, and obtain the optimal estimated value of the road inclination. The optimal estimated value of the road inclination is used as the road inclination of the detection vehicle in the current area to be detected.

4. The method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road according to claim 3, characterized in that: The specific process of the primary filtering process in step S22 is as follows: The pitch angle measurement values ​​in the collected data set are sequentially input into the first-order filter for preprocessing according to the collection time. The preprocessing process is to weight the pitch angle measurement value at the current collection time and the filter output value output after filtering by the first-order filter at the previous collection time to obtain the filter output value at the current collection time, and use the filter output value at each collection time as the preprocessing data; The calculation method of the first-order filter is: Among them, α represents the filter coefficient, Indicates the pitch angle measurement value at the current acquisition moment. Indicates the filter output value at the last acquisition moment, Indicates the filter output value at the current acquisition moment.

5. The method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road according to claim 3, characterized in that: The specific process of step S23 is: S231, calculating the average value of n preprocessed data and the residual corresponding to each preprocessed data; S232, calculating the standard deviation of n preprocessed data according to the residual of each preprocessed data; S233, calculating the studentized residual corresponding to each preprocessed data according to the standard deviation and the residual of each preprocessed data; S234, traverse n pre-processed data, and determine whether the studentized residual corresponding to each pre-processed data exceeds a preset threshold. If so, remove the pre-processed data, and if not, save it in the road inclination angle data set; S235. Calculate the average value of the data in the road inclination data set to obtain an optimal estimated value of the road inclination.

6. The method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road according to claim 2, characterized in that: The electric adjustment structure is used to drive the optical axis of the light source to move. The specific process of step S3 is as follows: S31, obtaining the actual angle between the light source axis of the detection module and the horizontal plane according to the sum of the compensation angle and the target incident angle; S32, inputting the actual angle and the target incident angle into the established mathematical model of the motion relationship between the travel distance of the electric adjustment structure and the road inclination angle, and calculating the moving distance a of the electric adjustment structure; S33. Determine the direction of the ramp on which the inspection vehicle is traveling according to the road inclination angle, and control the electric adjustment structure to adjust the incident angle of the light axis of the light source to the target incident angle according to the ramp direction and the moving distance a.

7. The method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road according to claim 6, characterized in that: The electric adjustment structure includes a stepper motor with a lead screw and a slider that moves with the lead screw and drives the optical axis of the light source to move. The mathematical model of the motion relationship in step S32 is: Where L is the length of the light source mounting plate whose mounting direction is parallel to the light source optical axis, ω is the actual angle, and β is the target incident angle. Indicates the minimum acute angle of the slider cross section.

8. The method for detecting the retroreflection coefficient of a vehicle-mounted sign on an adaptive slope road according to claim 7, characterized in that: In step S33, the process of determining the direction of the slope on which the detection vehicle is traveling according to the road inclination angle is as follows: When the road inclination angle is positive, the ramp direction is uphill, and when the road inclination angle is negative, the ramp direction is downhill. When the inspection vehicle is traveling uphill, the screw rod drives the slider to move forward a distance a in the direction of the inspection vehicle. When the inspection vehicle is traveling downhill, the screw rod drives the slider to move backward a distance a in the opposite direction of the inspection vehicle.

9. A vehicle-mounted sign retroreflection coefficient detection system for adaptive slope roads, characterized in that: It includes an observation module, a detection module, a tilt sensor and an electric adjustment structure for adjusting the incident angle of the detection module, which are respectively connected to the control module for communication. The observation module includes a camera and a radar. The optical axes of the camera and the radar are installed on the roof of the inspection vehicle parallel to the length direction of the inspection vehicle to capture images of the area to be inspected. The detection module includes a detection camera, a light source for illumination, and a mounting bracket for fixing the detection camera and the light source, and the angle between the optical axis of the light source and the axis of the retroreflector of the traffic sign to be detected is adjusted to the target incident angle; The inclination sensor is installed horizontally on the top of the inspection vehicle to measure the road inclination information at any time when the inspection vehicle is driving on the road; The electric adjustment structure is installed on the luggage rack on the top of the inspection vehicle and is movably connected to the mounting bracket, and is used to drive the mounting bracket to move under the control of the control module so that the incident angle between the optical axis of the light source and the axis of the retroreflector of the traffic sign to be inspected remains unchanged; The control module is used to execute a method for detecting the retro-reflection coefficient of a vehicle-mounted sign on an adaptive slope road as described in any one of claims 1-8.

10. The vehicle-mounted sign retroreflection coefficient detection system for adaptive slope roads according to claim 9, characterized in that: The electric adjustment structure includes a stepper motor with a lead screw and an encoder. A lead screw guide rail is fixed on the top of the detection vehicle. A wedge-shaped slider is installed on the lead screw guide rail. The cross-section of the wedge-shaped slider is an isosceles right triangle with an acute angle of σ. The rotation of the lead screw drives the wedge-shaped slider to move back and forth along the lead screw guide rail. The wedge-shaped slider is connected to one end of the mounting bracket through a bearing, thereby raising or lowering the incident angle of the optical axis of the light source.

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