A sign board shielding detection method and system based on laser ranging

Abstract

The application provides a kind of signboard shielding detection method and system based on laser ranging, comprising: the measurement data of laser ranging module on traffic signboard is obtained in first time interval regularly;Judge whether there is the measurement data of the object in front and whether the measurement data is within the preset threshold range, if yes, the position and elevation information of the laser ranging module are obtained;According to the position, the elevation information and the measurement data, it is judged whether the traffic signboard is shielded.The application can realize accurate positioning, timing monitoring, intelligent analysis, early warning scheduling, real-time self-checking of traffic signboard tree shielding intelligent detection, promote the construction and development of smart city traffic system, reduce labor cost, improve road facility maintenance efficiency, and has important significance for traffic management and traffic safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road traffic safety, in particular to a signboard shielding detection method and system based on laser ranging. BACKGROUND

[0002] For road traffic safety, the trees or other plants planted on both sides of the road and the isolation belt, the billboards, pipelines and the like set up should maintain a necessary distance from the traffic facilities, and should not shield the street lamps, traffic signal lights, traffic signs, and should not hinder the safety sight distance and should not affect the traffic. And the traffic signboard is a very important part of the road traffic system, which provides necessary traffic information for the driver, and plays an important role in the smooth progress of traffic flow and the effective development of traffic management. Most of the traffic signboards are set on the road side, and since the street trees grow over time, the height and volume increase, which leads to shielding the traffic signboard, and often needs manual inspection and pruning. But the growth of trees is difficult to predict, and the existing detection method of the shielded traffic signboard still stays in the stage of manual inspection. This needs to consume a lot of manpower, and the efficiency is low, and the situation of the traffic signboard being shielded by the obstacle may not be able to be handled in time.

[0003] At the same time, most cities in China do not fully consider the influence of the dynamic growth of street trees on traffic signboards when planning roads, and there is a phenomenon of incoordination between the setting position and method of traffic signboards and the planting, growth, management, detection and pruning of street trees, which easily causes the situation of street trees shielding signboards, affects the driver's judgment of important road information, and thus causes a series of traffic accidents. At present, the research on this problem is mostly problem analysis, which generally solves the problem of street trees shielding traffic signboards from reasonable pruning, and lacks in-depth research on how to intelligently and automatically detect street trees shielding traffic signboards and subsequent self-detection, automatic adjustment and the like. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a signboard shielding detection method and system based on laser ranging, which effectively realizes intelligent detection of street trees shielding traffic signboards.

[0005] In order to solve the above technical problems, the technical scheme adopted by the present application is:

[0006] A signboard shielding detection method based on laser ranging, comprising the steps of:

[0007] S1, acquiring the measurement data of the laser ranging module on the traffic signboard at a first time interval;

[0008] S2, judging whether there is measurement data of the front object and whether the measurement data is within a preset threshold range, if yes, entering step S3;

[0009] S3, acquiring position and elevation information of the laser ranging module;

[0010] S4, judging whether the traffic sign is shielded according to the position, the elevation information and the measurement data.

[0011] To solve the above technical problems, another technical solution adopted by the present application is:

[0012] A sign shielding detection system based on laser ranging, comprising a laser ranging module, a single-chip microcomputer module, a Beidou positioning module and a self-checking module;

[0013] The laser ranging module is installed on a traffic sign and performs laser ranging at a first time interval to obtain measurement data;

[0014] The single-chip microcomputer module acquires the measurement data and judges whether there is measurement data of a front object and whether the measurement data is within a preset threshold range, and if so, sends the measurement data to the self-checking module;

[0015] The Beidou positioning module is used to acquire position and elevation information of the laser ranging module when the measurement data exceeds the preset threshold, and send the information to the self-checking module;

[0016] The self-checking module judges whether the traffic sign is shielded according to the position, the elevation information and the measurement data.

[0017] The present application has the advantages that a sign shielding detection method and system based on laser ranging are provided, the data obtained by laser ranging is processed, the position and elevation information of the laser ranging module are combined to judge whether the traffic sign is shielded, the efficiency and accuracy are greatly improved, the position information of the sign shielded by a street tree or the information of a system failure can be transmitted to the back-end terminal of the road maintenance personnel in time to inform the relevant personnel to complete the accurate and timely street tree pruning and system maintenance, improve the road facility maintenance efficiency, and overall realize the intelligent detection of traffic sign tree shielding with accurate positioning, regular monitoring, intelligent analysis, early warning scheduling and real-time self-checking, which can reduce traffic delay, improve traffic operation efficiency and reduce traffic accidents, promote the construction and development of smart city traffic system, reduce labor cost, improve road facility maintenance efficiency, and have important significance for traffic management and traffic safety. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A flowchart of a sign shielding detection method based on laser ranging according to an embodiment of the present application;

[0019] Figure 2A schematic diagram of a traffic signboard of the laser ranging traffic signboard according to the embodiment of the present application;

[0020] Figure 3 A system architecture diagram of a signboard occlusion detection system based on laser ranging according to the embodiment of the present application. DETAILED DESCRIPTION

[0021] To make the technical content of the present application, the purposes and effects achieved clear, the following will be described in detail in conjunction with the embodiments and the accompanying drawings.

[0022] Please refer to Figure 1 A signboard occlusion detection method based on laser ranging, comprising the steps of:

[0023] S1, obtaining the measurement data of the laser ranging module on the traffic signboard at a first time interval;

[0024] S2, judging whether there is measurement data of the front object and whether the measurement data is within a preset threshold range, if yes, entering step S3;

[0025] S3, obtaining the position and elevation information of the laser ranging module;

[0026] S4, judging whether the traffic signboard is occluded according to the position, the elevation information and the measurement data.

[0027] From the above description, the beneficial effects of the present application are that a signboard occlusion detection method based on laser ranging is provided, through the processing of the data obtained by laser ranging, combined with the position and elevation information of the laser ranging module, whether the traffic signboard is occluded is judged, which greatly improves the efficiency and accuracy, and the position information of the signboard occluded by the street trees or the information of the system failure can be transmitted to the background terminal of the road maintenance personnel in time to inform the relevant personnel to complete the accurate and timely street tree pruning and system maintenance, improve the road facility maintenance efficiency, and overall realize the intelligent detection of traffic signboard tree occlusion with precise positioning, timing monitoring, intelligent analysis, early warning scheduling and real-time self-checking, which can reduce traffic delay, improve traffic operation efficiency and reduce traffic accidents, and can promote the construction and development of smart city traffic system, reduce labor cost, improve road facility maintenance efficiency, and has important significance for traffic management and traffic safety.

[0028] Further, the step S1 further comprises calculating the preset threshold, and the calculation process is as follows:

[0029] The distance of the vehicle driving in the period from when the driver cannot see the sign content to when he can see and start reading the sign content when discovering the traffic signboard is obtained in advance, which is recorded as the discovery distance S a :

[0030] S a = V0t1 (1);

[0031] wherein V0 is the vehicle speed at the beginning of the discovery, and t1 is the time of discovering the traffic sign;

[0032] the distance of the vehicle running from the beginning of reading the sign content to the end of understanding and preparing to start action is obtained, and is recorded as the reading distance S b :

[0033] S b = V0t2 (2);

[0034] wherein t2 is the time of reading the sign content;

[0035] the distance of the vehicle running from the beginning of decision to the end of decision is obtained, and is recorded as the decision distance S c :

[0036] S c = V0t3 (3);

[0037] wherein t3 is the decision time;

[0038] the distance of the vehicle running from the end of decision to the beginning of operation of the vehicle is obtained, and is recorded as the reaction distance S d :

[0039] S d = V0t4 (4);

[0040] wherein t4 is the time of operation reaction;

[0041] the distance of the vehicle running from the beginning of operation to the end of operation is obtained, and is recorded as the action distance S e :

[0042]

[0043] wherein n is the number of lanes, V1 is the design speed, and Q is the traffic volume of the second level of service under the design speed;

[0044] the distance of the traffic sign disappearing from the view of the driver is recorded as the visual disappearance distance S f :

[0045]

[0046] wherein H is the lateral distance from the line of sight of the driver to the traffic sign, H0 is the height of the traffic sign, H 车 is the height of the vehicle, and a is the horizontal angle between the disappearing point of the traffic sign and the roadside traffic sign;

[0047] Assuming that the driving distance of the driver without deceleration during the time from finding the traffic sign to completing the reaction is S1:

[0048]

[0049] Let L1 be the data measured by the laser ranging module when the minimum angle with the ground is 0-30°, recorded as the first distance, L2 be the data measured by the laser ranging module when the medium angle with the ground is 31-60°, recorded as the second distance, and L3 be the data measured by the laser ranging module when the maximum angle with the ground is 61-90°, recorded as the third distance.

[0050] The measured data of the laser ranging module satisfies the following formula (8):

[0051]

[0052] When there is no car and no obstacle on the road, let H1=H0, and the measured data of the laser ranging module satisfies the following formula (9):

[0053]

[0054] When there is a large truck or a large obstacle on the road, let H2=H0-H, and the measured data of the laser ranging module satisfies the following formula (10):

[0055]

[0056] The range of the preset threshold is obtained as follows:

[0057]

[0058] wherein, L 长 , L 中 and L 短 are L1, L2 and L3 within the range of the preset threshold.

[0059] Further, the step S2 is specifically:

[0060] If at least one of the first distance L1, the second distance L2 and the third distance L3 measured by the laser ranging module falls within the range of the preset threshold, it is preliminarily judged that the traffic sign is blocked, and step S3 is entered.

[0061] From the above description, in order to determine the shielding condition of the street tree to the traffic sign, before the distance data measured by the laser ranging module is used for conditional judgment, the range of the preset threshold value can be determined in advance by setting and measuring the distance and speed of the driver during driving, so as to serve as the basis for judging whether the actual distance measured by the laser ranging module in real time falls within the range of the preset threshold value, thereby ensuring the accuracy of the judgment of whether the traffic sign is shielded.

[0062] Further, the step S4 specifically includes:

[0063] S41, receiving the preliminary judgment result, controlling the laser ranging module to perform continuous laser ranging for a first preset number of times at a second time interval, obtaining the first distance L1, the second distance L2 and the third distance L3 for the first preset number of times, and the second time interval is less than the first time interval;

[0064] S42, judging the number of times that the actual distance for the first preset number of times does not fall within the preset threshold value, if the number of times is less than a second preset number of times, the secondary judgment is that the traffic sign is not shielded, and the secondary judgment result and the measurement data are sent to the background terminal;

[0065] Otherwise, the secondary judgment is that the traffic sign is shielded, and the reason for the traffic sign being shielded is judged according to the position, the elevation information and the measurement data, and the secondary judgment result, the reason and the measurement data are sent to the background terminal;

[0066] The reason includes street tree shielding, device angle deviation, device falling off and device failure.

[0067] From the above description, the actual distance measured at the first time interval falling within the range of the preset threshold value is taken as the preliminary judgment result of whether the traffic sign is shielded, in order to avoid the traffic sign being shielded under accidental circumstances (such as a bird flying in front of the traffic sign and being measured by the laser ranging module, etc.), therefore, continuous multiple laser ranging at the second time interval is performed by the self-checking module, so as to further determine whether the traffic sign is truly shielded by the number of times that the continuous multiple ranging results do not fall within the range of the preset threshold value, thereby ensuring the accuracy of the shielding detection; meanwhile, after it is determined that the traffic sign is shielded, the reason for the traffic sign being shielded needs to be further judged according to the position, the elevation information of the laser ranging module and multiple measurement data measured under shielding, whether the traffic sign is shielded by the street tree or the laser ranging module itself is caused by device angle deviation, device falling off or failure, which further ensures the accuracy of the shielding detection, and is also convenient for the subsequent background terminal to give corresponding alarm prompt according to the shielding reason.

[0068] Further, the step S4 further includes the step:

[0069] S51, the background terminal receives the secondary determination result, if the secondary determination result is that the traffic sign is blocked, according to the reason for the blocked traffic sign, the relevant personnel are warned and maintained;

[0070] S52, when the reason is that the traffic sign is blocked by a street tree, according to the current season and the number of times that the actual distance measured in the continuous laser ranging falls within the preset threshold, the size of the first time interval is adjusted and the relevant personnel are notified to prune the street tree.

[0071] From the above description, in order to save the power consumption of the laser ranging module and improve its service life, the first time interval of the laser ranging module for timing ranging is adjusted according to the different growth conditions of street trees in different seasons and the reasons for the street trees blocking the traffic signs obtained by judgment, and the period for notifying the relevant maintenance personnel to prune the street trees is adjusted, which greatly improves the efficiency of road facility maintenance.

[0072] Please refer to Figure 2 and Figure 3 , a sign blocking detection system based on laser ranging, comprising a laser ranging module, a single-chip microcomputer module, a Beidou positioning module and a self-checking module;

[0073] The laser ranging module is installed on the traffic sign and performs laser ranging at a first time interval to obtain measurement data;

[0074] The single-chip microcomputer module acquires the measurement data and judges whether there is measurement data of the object in front and whether the measurement data is within a preset threshold range, if so, the measurement data is sent to the self-checking module;

[0075] The Beidou positioning module is used to acquire the position and elevation information of the laser ranging module when the measurement data exceeds the preset threshold, and send it to the self-checking module;

[0076] The self-checking module judges whether the traffic sign is blocked according to the position, the elevation information and the measurement data.

[0077] From the above description, the beneficial effects of the present application are that: based on the same technical concept, cooperate with the above-mentioned one kind of signboard shielding detection method based on laser ranging, provide a signboard shielding detection system based on laser ranging, through the processing of the data obtained by laser ranging, combined with the position and elevation information of the laser ranging module, judge whether the traffic signboard is shielded, greatly improve the efficiency and accuracy, can timely transmit the position information of the signboard shielded by the street tree or the information of the system failure to the background terminal of the road maintenance personnel, to inform the relevant personnel to complete the accurate and timely street tree pruning and system maintenance, improve the road facility maintenance efficiency, realize the intelligent detection of traffic signboard tree shielding of accurate positioning, timing monitoring, intelligent analysis, early warning scheduling, real-time self-checking, can reduce traffic delay, improve traffic operation efficiency and reduce traffic accidents, and can promote the construction and development of smart city traffic system, reduce labor cost, improve road facility maintenance efficiency, which has important significance for traffic management and traffic safety.

[0078] Further, the laser ranging module is also used to calculate the preset threshold, and the calculation process is as follows:

[0079] Pre-acquire the distance of the vehicle running in the time period from the driver discovering the traffic signboard to being able to see and start reading the signboard content, recorded as discovery distance S a :

[0080] S a =V0t1 (1);

[0081] Wherein, V0 is the speed at the beginning of discovery, t1 is the time of discovering the traffic signboard;

[0082] Acquire the distance of the vehicle running in the time period from the driver starting to read the signboard content to understanding the end and preparing to start action, recorded as reading distance S b :

[0083] S b =V0t2 (2);

[0084] Wherein, t2 is the time of reading the signboard content;

[0085] Acquire the distance of the vehicle running in the time period from the driver starting to read the signboard content to understanding the end and preparing to start action, recorded as reading distance S c :

[0086] S c =V0t3 (3);

[0087] Wherein, t3 is the decision time;

[0088] The distance of the vehicle running from the end of the decision of the driver to the start of the operation of the vehicle is recorded as the reaction distance S d :

[0089] S d = V0t4 (4);

[0090] Wherein, t4 is the time of operation reaction;

[0091] The distance of the vehicle running from the start of the operation to the operation medium of the driver is recorded as the action distance S e :

[0092]

[0093] Wherein, n is the number of lanes, V1 is the design speed, and Q is the traffic volume of the second level of service under the design speed;

[0094] The distance from the traffic sign to the message in the driver's field of view is recorded as the visual disappearance distance S f :

[0095]

[0096] Wherein, H is the lateral distance from the driver's line of sight to the traffic sign, H0 is the height of the traffic sign, H 车 is the height of the vehicle, and a is the horizontal angle between the traffic sign disappearance point and the roadside traffic sign;

[0097] The distance of the driver running without deceleration from discovering the traffic sign to completing the reaction is recorded as S1:

[0098]

[0099] Let L1 be the data measured by the laser ranging module when the minimum angle with the ground is recorded as the first distance, the minimum angle is in the range of 0-30°, L2 is the data measured by the laser ranging module when the medium angle with the ground is recorded as the second distance, the medium angle is in the range of 31-60°, and L3 is the data measured by the laser ranging module when the maximum angle with the ground is recorded as the third distance, the maximum angle is in the range of 61-90°;

[0100] Then the measurement data measured by the laser ranging module satisfies the following formula (8):

[0101]

[0102] When there is no car and no obstacle on the road, let H1 = H0, then the measurement data measured by the laser ranging module satisfies the following formula (9):

[0103]

[0104] When there is a large truck or a large obstacle on the road surface, let H2=H0-H, and the measurement data measured by the laser ranging module satisfies the following formula (10):

[0105]

[0106] The range of the preset threshold is obtained as follows formula (11):

[0107]

[0108] Wherein, L 长 , L 中 and L 短 are L1, L2 and L3 within the range of the preset threshold.

[0109] Further, the single-chip microcomputer module judges whether the measurement data exceeds the preset threshold, specifically:

[0110] If at least one of the first distance L1, the second distance L2 and the third distance L3 measured by the laser ranging module falls within the range of the preset threshold, it is preliminarily judged that the traffic sign is blocked, and the preliminary judgment result is sent to the self-checking module.

[0111] From the above description, in order to judge the blocking condition of the street tree to the traffic sign, before using the distance data measured by the laser ranging module to make conditional judgment, the range of the preset threshold can be determined in advance by setting and measuring the distance and speed of the driver during driving, so as to serve as the basis for subsequent judgment of whether the actual distance measured by the laser ranging module falls within the range of the preset threshold, and further to ensure the accuracy of the judgment of whether the traffic sign is blocked.

[0112] Further, it further includes a background terminal, and the self-checking module is specifically used for:

[0113] Receiving the preliminary judgment result, controlling the laser ranging module to perform continuous laser ranging for a first preset number of times at a second time interval to obtain the first distance L1, the second distance L2 and the third distance L3 for the first preset number of times, and the second time interval is less than the first time interval;

[0114] Judging the number of times that the actual distance for the first preset number of times does not fall within the range of the preset threshold, if the number of times is less than a second preset number of times, it is judged again that the traffic sign is not blocked, and the second judgment result and the measurement data are sent to the background terminal;

[0115] Otherwise, the secondary judgment is that the traffic sign is blocked, and the reason for the blocking of the traffic sign is judged according to the position, the elevation information and the measurement data, and the secondary judgment result, the reason and the measurement data are sent to the background terminal;

[0116] The reason includes tree blocking, device angle deviation, device falling off and device failure.

[0117] As can be seen from the above description, the actual distance measured at the first time interval falling within the range of the preset threshold is taken as the preliminary judgment result of the traffic sign being blocked, in order to avoid the traffic sign being blocked in accidental situations (such as a bird flying in front of the traffic sign and being measured by the laser ranging module, etc.), so that continuous multiple laser ranging at a second time interval is performed through the self-checking module, so as to further determine whether the traffic sign is truly blocked by the number of times of the multiple ranging results not falling within the range of the preset threshold, so as to ensure the accuracy of the blocking detection; meanwhile, after it is determined that the traffic sign is blocked, the reason for the blocking of the traffic sign is further judged according to the position, the elevation information and the multiple measurement data measured under the blocking, whether the traffic sign is blocked by a tree or the laser ranging module itself is caused by device angle deviation, device falling off or failure, so as to further ensure the accuracy of the blocking detection, and also facilitate the background terminal to give corresponding alarm and maintenance notification according to the blocking reason.

[0118] Further, the background terminal is specifically used for:

[0119] receiving the secondary judgment result, and if the secondary judgment result is that the traffic sign is blocked, giving alarm and maintenance notification to relevant personnel according to the reason for the blocking.

[0120] When the reason is tree blocking, the size of the first time interval is adjusted and relevant personnel are notified to trim the trees according to the current season and the number of times of the actual distance measured in the continuous laser ranging falling within the preset threshold.

[0121] As can be seen from the above description, in order to save the power consumption of the laser ranging module and improve its service life, the first time interval of the laser ranging module for regular ranging is adjusted and the period of notifying relevant maintenance personnel to trim the trees is adjusted according to the different growth conditions of the trees in different seasons and the reason of the trees blocking the traffic sign, so as to greatly improve the road facility maintenance efficiency.

[0122] The present application provides a kind of sign blocking detection method and system based on laser ranging, mainly applied to the scene of the blocking detection of road traffic sign, specific description is made as follows in combination with specific embodiment:

[0123] Please refer toFigure 1 Embodiment one of the present application is:

[0124] A signboard shielding detection method based on laser ranging, as shown in Figure 1 The steps include:

[0125] S1, the measurement data of the laser ranging module on the traffic signboard is obtained at a first time interval.

[0126] S2, it is judged whether there is measurement data of the front object and whether the measurement data is within the preset threshold range, if yes, step S3 is entered.

[0127] S3, the position and elevation information of the laser ranging module is obtained.

[0128] S4, it is judged whether the traffic signboard is shielded according to the position, elevation information and measurement data.

[0129] That is, in this embodiment, by processing the data obtained by laser ranging, combined with the position and elevation information of the laser ranging module, it is judged whether the traffic signboard is shielded, which greatly improves the efficiency and accuracy, and the position information of the signboard shielded by the street tree or the information of the system failure can be transmitted to the background terminal of the road maintenance personnel in time to inform the relevant personnel to complete the accurate and timely street tree pruning and system maintenance, improve the road facility maintenance efficiency, and overall realize the intelligent detection of traffic signboard tree shielding with accurate positioning, timely monitoring, intelligent analysis, early warning scheduling and real-time self-checking, which can reduce traffic delay, improve traffic operation efficiency and reduce traffic accidents, and can promote the construction and development of smart city traffic system, reduce labor cost, improve road facility maintenance efficiency, and has important significance for traffic management and traffic safety.

[0130] Embodiment two of the present application is:

[0131] A signboard shielding detection method based on laser ranging, on the basis of the above embodiment one, in this embodiment, in order to judge the shielding condition of the traffic signboard by the street tree, before the distance data measured by the laser ranging module is used for conditional judgment, the distance and speed of the vehicle during the driving of the driver can be measured and set in advance to determine the range of the preset threshold, which is used as the basis for judging whether the actual distance measured by the laser ranging module in real time falls within the preset threshold range, and further ensures the accuracy of the judgment of whether the traffic signboard is shielded. That is, before step S1, the preset threshold is calculated, and the calculation process is as follows:

[0132] The distance of the vehicle during the time from when the driver cannot see the sign content to when he can see and start reading the sign content when he finds the traffic signboard is obtained in advance, which is recorded as the discovery distance S a :

[0133] S a = V0t1 (1) ;

[0134] Wherein, V0 is the vehicle speed at the beginning of the discovery, t1 is the time of discovering the traffic sign, in this embodiment, t1 can be preset as 0.4s.

[0135] Then the distance of the vehicle running in the time from the driver starting reading the sign content to the end of understanding and preparing to start action is obtained, recorded as reading distance S b :

[0136] S b = V0t2 (2) ;

[0137] Wherein, t2 is the time of reading the sign content, in this embodiment, t2 can be preset as 1.0-2.0s.

[0138] Then the distance of the vehicle running in the time from the driver starting decision to the end of decision is obtained, recorded as decision distance S c :

[0139] S c = V0t3 (3) ;

[0140] Wherein, t3 is the decision time, in this embodiment, t3 can be preset as 2.0-2.5s.

[0141] Then the distance of the vehicle running in the time from the end of decision to the start of operating the vehicle is obtained, recorded as reaction distance S d :

[0142] S d = V0t4 (4) ;

[0143] Wherein, t4 is the time of operating reaction, in this embodiment, t4 can be preset as 1.2-2.5s.

[0144] Then the distance of the vehicle running in the time from the start of operation to the end of operation is obtained, recorded as action distance S e :

[0145]

[0146] Wherein, n is the number of lanes, V1 is the design speed, Q is the traffic volume under the design speed of the second level of service. The end point of operation is generally the exit ramp, intersection or dangerous point, etc., and the driver must complete the action such as changing lanes, changing direction, deceleration or parking within the distance.

[0147] When the driver is less than a certain distance from the traffic sign, the sign will disappear from the driver's field of view, the driver can no longer watch the information on the sign, and the distance at which the traffic sign disappears from the driver's field of view is the visual disappearance distance S f :

[0148]

[0149] wherein H is the lateral distance from the driver's line of sight to the traffic sign, H0 is the height of the traffic sign, H 车 is the height of the vehicle, and a is the horizontal angle between the vanishing point of the traffic sign and the roadside traffic sign, which is generally 15°.

[0150] In this embodiment, in urban roads, V0=60km / h 16.67m / s, H0=5.2m, H 车 =2m, and a=30° are taken, and t1-t4 are all taken as the maximum values in the respective limited ranges for safety considerations.

[0151] Then, according to the above formula (6), the following can be obtained:

[0152] H=H0-H 车 =4.0m;

[0153] S f =7.0m;

[0154] wherein t 总 =t1+t2+t3+t4=7.4s.

[0155] Suppose that the driving distance of the driver during the time from discovering the traffic sign to completing the reaction without deceleration is S1:

[0156]

[0157] Then, according to the above formula (7), the following can be obtained:

[0158] S1=16.67×7.4123.36m≈123m;

[0159] S=S1+S f =130m.

[0160] Let L1 be the data measured by the laser ranging module when the smallest angle with the ground is obtained, which is recorded as a first distance, wherein the smallest angle ranges from 0 to 30°, L2 be the data measured by the laser ranging module when the medium angle with the ground is obtained, which is recorded as a second distance, wherein the medium angle ranges from 31 to 60°, and L3 be the data measured by the laser ranging module when the largest angle with the ground is obtained, which is recorded as a third distance, wherein the largest angle ranges from 61 to 90°.

[0161] The measurement data measured by the laser ranging module satisfies the following formula (8) :

[0162]

[0163] The actual distance measured by the laser ranging module can be calculated by substituting the specific values above into formula (8) :

[0164]

[0165]

[0166]

[0167] When there is no car and no obstacle on the road surface, let H1 = H0, the measurement data measured by the laser ranging module satisfies the following formula (9) :

[0168]

[0169] Since H1 = H0 = 5.2m, according to the above formula (9), it can be calculated that:

[0170]

[0171]

[0172]

[0173] When there is a large truck or a large obstacle on the road surface, let H2 = H0-H, the measurement data measured by the laser ranging module satisfies the following formula (10) :

[0174]

[0175] Since H1 = H0-H = 1.2m, according to the above formula (9), it can be calculated that:

[0176]

[0177]

[0178]

[0179] The range of the preset threshold is as follows formula (11) :

[0180]

[0181] Where, L 长 , L 中 and L 短These are L1, L2, and L3, respectively, within the preset threshold range.

[0182] Right now:

[0183] 130.006m <L 长 <130.105m;

[0184] 68.512 <L 中 <68.698m;

[0185] 7.113 <L 短 <8.729m.

[0186] Due to errors and other factors, L1 is taken as 120.000–140.000m, L2 as 65.000–75.000m, and L3 as 6.000–9.500m, that is:

[0187] 120.000m≤L1≤140.000m;

[0188] 65.000m≤L2≤75.000m;

[0189] 6.000m≤L3≤9.500m.

[0190] The preset threshold range is now determined. Then, the actual distance data measured by formula (8) is used to determine whether it falls within the preset threshold range. Specifically, step S2 is as follows:

[0191] If at least one of the first distance L1, the second distance L2, and the third distance L3 actually measured by the laser ranging module falls within the range of a preset threshold, it is preliminarily determined that the traffic sign is obstructed, and the process proceeds to step S3, where the measurement data and judgment results, along with the position and elevation information of the laser ranging module, are transmitted to a self-testing module for further determination of the obstruction. In this embodiment, the determination of whether the actual measured distance falls within a preset threshold range can be achieved by a microcontroller that communicates and controls the laser ranging module. The microcontroller's built-in program receives the distance data measured and transmitted by the laser ranging module, compares the distance data with the preset threshold range, and makes a preliminary judgment on whether the distance data meets the condition that the traffic sign is not obscured. At the same time, the position and elevation information of the laser ranging module can be obtained by the Beidou positioning module. The Beidou positioning module communicates with the laser ranging module, and after obtaining the position and elevation information of the laser ranging module, it transmits it together with the distance data measured by the laser ranging module and the preliminary judgment result of the microcontroller's built-in program to a self-testing module. The self-testing module then enters the subsequent secondary judgment process to ensure the accuracy of the traffic sign obstruction detection.

[0192] The execution process of the self-test module in step S4 is as follows:

[0193] S41, the self-checking module receives the preliminary judgment result, controls the laser ranging module to perform continuous laser ranging for a first preset number of times at a second time interval, obtains a first preset number of first distances L1, second distances L2, and third distances L3, and the second time interval is less than the first time interval.

[0194] S42, if the number of times that the actual distance falls outside the preset threshold value is less than a second preset number of times, the second judgment is that the traffic sign is not blocked, and the second judgment result and the measurement data are sent to the background terminal;

[0195] otherwise, the second judgment is that the traffic sign is blocked, and the reason for the traffic sign being blocked is determined according to the position, elevation information, and measurement data, and the second judgment result, the reason, and the measurement data are sent to the background terminal;

[0196] The reasons include tree blocking, device angle deviation, device falling, and device failure.

[0197] In this embodiment, for example, the self-checking module starts continuous laser ranging for ten times, each time with an interval of 30 seconds (i.e., the second time interval). If the data of x times or more times in the ten detections are within the preset range, it is determined that the traffic sign is not blocked, and the data and the judgment result are transmitted to the background terminal. If y times or more times are outside the range, it is determined that the traffic sign is blocked, and then the self-checking module further analyzes the reason for the traffic sign being blocked in combination with the position and elevation information of the laser ranging module, and then transmits the data, the judgment result, and the reason to the background terminal.

[0198] That is, the actual distance measured at the first time interval falling within the range of the preset threshold value is used as the preliminary judgment result of whether the traffic sign is blocked. In order to avoid the traffic sign being blocked under accidental circumstances (such as a bird flying in front of the traffic sign and being measured by the laser ranging module), the self-checking module performs continuous laser ranging at the second time interval to further determine whether the traffic sign is truly blocked by the number of times that the actual distance falls outside the preset threshold value in the continuous ranging results, thereby ensuring the accuracy of the blocking detection. Meanwhile, after it is determined that the traffic sign is blocked, the position, elevation information, and multiple measurement data measured under blocking are further used to determine whether the traffic sign is blocked by a tree or the laser ranging module itself is deviated in angle, falls, or fails, thereby further ensuring the accuracy of the blocking detection and facilitating the background terminal to give corresponding alarm prompts according to the blocking reason.

[0199] When the second judgment is performed, the background terminal needs to solve the corresponding problem according to the second judgment result, that is, after step S4, the following steps are further included:

[0200] S51, the background terminal receives the secondary judgment result, if the secondary judgment result is that the traffic sign is blocked, then according to the reason of being blocked, the relevant personnel is warned and the maintenance notice is sent.

[0201] S52, when the reason is that the street tree is blocked, according to the current season and the number of times that the actual distance measured in the continuous laser ranging falls within the preset threshold, the size of the first time interval is adjusted and the relevant personnel is notified to trim the street tree.

[0202] That is, in order to save the power consumption of the laser ranging module and improve its service life, according to the different growth conditions of street trees in different seasons and the reasons for blocking traffic signs obtained by judgment, the first time interval of the laser ranging module is adjusted, and the period of notifying the relevant maintenance personnel to trim the street trees is adjusted, which greatly improves the efficiency of road facility maintenance.

[0203] In this embodiment, it is worth noting that the laser ranging module can be powered by a built-in solar cell to realize ranging work, and in order to reduce power consumption, a timer is set in the single-chip microcomputer program to set the ranging frequency of the laser ranging module. The ranging frequency can be set according to the growth conditions of street trees in different seasons, that is, the size of the first time interval can be set in two different programs of spring and summer, autumn and winter, for example, three days for a cycle in spring and summer, and six days for a cycle in autumn and winter. After combining the blocking frequency data of the judgment result received by the background terminal that the street tree growth causes the traffic sign to be blocked, the blocking data can be analyzed to adjust the size of the first time interval, that is, to adjust the cycle of the laser ranging module for ranging. For example, if the feedback result of ten times of starting ranging is that the number of times of blocking is greater than 3 times, then the cycle of two days for a cycle in spring and summer is modified, the cycle of four days for a cycle in autumn and winter is modified, and the cycle of trimming the street trees by the maintenance personnel is also modified, so as to maximize the avoidance of the situation that the traffic sign is blocked. The frequency can also be set and modified by the relevant personnel through the background terminal.

[0204] In addition, it is worth noting that the self-checking module can also be combined with the position and elevation information in the Beidou positioning module before each start of the entire ranging system, through the built-in program of the single-chip microcomputer, combined with the elevation detected at the initial system startup, to perform self-checking, analyze the position, elevation information, power and data fluctuation range in the laser ranging process, and judge the conditions in the database, if the elevation error exceeds 10 cm, the result is that the laser ranging module falls off; if the battery current is lower than 20%, it is judged that the laser ranging module is insufficient in power; if the laser ranging data is not within the preset threshold range for y times or more, it is judged that the laser ranging module is blocked, the device angle is offset or faulty, etc. After judging the specific result, the result is transmitted to the background terminal together with the position and elevation information of the Beidou positioning module, and relevant department personnel are notified to handle.

[0205] Please refer to Figure 2 and 3 Embodiment three of the present application is:

[0206] A signboard blocking detection system based on laser ranging, as shown in Figure 3 , comprising a laser ranging module (i.e. laser range finder), a single-chip microcomputer module, a Beidou positioning module and a self-checking module (i.e. self-checking module).

[0207] Among them, the laser ranging module is installed on the traffic sign as Figure 2 shown and performs laser ranging at a first time interval to obtain measurement data.

[0208] The single-chip microcomputer module obtains the measurement data and judges whether the measurement data exceeds the preset threshold, and if so, sends the measurement data to the self-checking module; at the same time, the Beidou positioning module is used to obtain the position and elevation information of the laser ranging module when the measurement data exceeds the preset threshold, and is also transmitted to the single-chip microcomputer module, and the single-chip microcomputer module uniformly sends the position and elevation information and the measurement data and its judgment result to the self-checking module.

[0209] The self-checking module judges whether the traffic sign is blocked according to the position, elevation information and measurement data.

[0210] That is, in the present embodiment, in combination with one of the above-mentioned embodiment one or embodiment two, a sign shielding detection system based on laser ranging is provided, by processing the data obtained by laser ranging, combining the position and elevation information of the laser ranging module, judging whether the traffic sign is shielded, greatly improving the efficiency and accuracy, and timely transmitting the position information of the sign shielded by the street tree or the information of the system failure to the background terminal of the road maintenance personnel, to inform the relevant personnel to complete the precise and timely street tree pruning and system maintenance, improve the road facility maintenance efficiency, and realize the intelligent detection of traffic sign tree shielding with precise positioning, timing monitoring, intelligent analysis, early warning scheduling and real-time self-checking, which can reduce traffic delay, improve traffic operation efficiency and reduce traffic accidents, and can promote the construction and development of smart city traffic system, reduce labor cost, improve road facility maintenance efficiency, and has important significance for traffic management and traffic safety.

[0211] As shown in Figure 3 , the fourth embodiment of the present application is:

[0212] A sign shielding detection system based on laser ranging, on the basis of the above-mentioned embodiment three, in this embodiment, in order to judge the shielding condition of traffic sign by street trees, before the distance data measured by the laser ranging module is used for conditional judgment, the range of the preset threshold value can be determined in advance by setting and measuring the distance and speed of the driver during driving, as the basis for subsequent judgment whether the actual distance measured by the laser ranging module falls within the range of the preset threshold value, and thus the accuracy of the judgment of whether the traffic sign is shielded is ensured. That is, the laser ranging module is also used to calculate the preset threshold value, and the calculation process is as follows:

[0213] The distance of the vehicle during the period from when the driver cannot see the sign content to when he can see and start reading the sign content when he finds the traffic sign is recorded as the discovery distance S a :

[0214] S a = V0t1 (1);

[0215] Wherein, V0 is the speed at the beginning of discovery, t1 is the time of discovering the traffic sign, in this embodiment, t1 can be preset as 0.4s.

[0216] Then the distance of the vehicle during the period from when the driver starts reading the sign content to when he understands the end and prepares to start action is recorded as the reading distance S b :

[0217] S b = V0t2 (2);

[0218] Wherein, t2 is the time of reading the content of the sign, in this embodiment, t2 can be preset as 1.0-2.0s.

[0219] Then the distance of the vehicle driven by the driver from the beginning of the decision to the end of the decision is obtained, denoted as the decision distance S c :

[0220] S c = V0t3 (3) ;

[0221] Wherein, t3 is the decision time, in this embodiment, t3 can be preset as 2.0-2.5s.

[0222] Then the distance of the vehicle driven by the driver from the end of the decision to the beginning of the operation on the vehicle is obtained, denoted as the reaction distance S d :

[0223] S d = V0t4 (4) ;

[0224] Wherein, t4 is the time of operation reaction, in this embodiment, t4 can be preset as 1.2-2.5s.

[0225] Then the distance of the vehicle driven by the driver from the beginning of the operation to the end of the operation is obtained, denoted as the action distance S e :

[0226]

[0227] Wherein, n is the number of lanes, V1 is the design speed, and Q is the traffic volume of the second level of service under the design speed. The end point of the operation is generally an exit ramp, an intersection or a dangerous point, and the driver must complete the action such as lane changing, direction changing, speed reducing or parking within the distance.

[0228] When the driver is less than a certain distance from the traffic sign, the sign disappears from the driver's field of view, and the driver can no longer watch the information on the sign, then the distance of the traffic sign disappearing from the driver's field of view is denoted as the visual disappearance distance S f :

[0229]

[0230] Wherein, H is the lateral distance from the driver's line of sight to the traffic sign, H0 is the height of the traffic sign, H 车 is the height of the vehicle, and a is the horizontal angle between the disappearance point of the traffic sign and the roadside traffic sign, generally 15°.

[0231] In this embodiment, in urban roads, V0=60km / h16.67m / s, H0=5.2m, H 车= 2m, a = 30°, for safety, t1~t4 are all taken as the maximum value in the range defined.

[0232] Then according to the above formula (6) calculation can be obtained:

[0233] H = H0-H 车 = 4.0m;

[0234] S f = 7.0m;

[0235] Where t 总 = t1+t2+t3+t4 = 7.4s.

[0236] Assuming the driver from the discovery of traffic signs to the reaction to complete this period of time within the middle of the driving distance S1:

[0237]

[0238] Then according to the above formula (7) calculation can be obtained:

[0239] S1 = 16.67 x 7.4123.36m ≈ 123m;

[0240] S = S1+S f = 130m.

[0241] Let L1 is the minimum angle with the ground when the laser ranging module measured data, recorded as the first distance, wherein the minimum angle range is 0~30°, L2 is with the ground when the laser ranging module measured data of medium angle, recorded as the second distance, wherein the medium angle range is 31~60°, L3 is with the ground when the laser ranging module measured data of maximum angle, recorded as the third distance, wherein the maximum angle range is 61~90°;

[0242] Then the laser ranging module measured data satisfy the following formula (8):

[0243]

[0244] Then according to the above specific value into formula (8) can be calculated by the laser ranging module measured actual distance:

[0245]

[0246]

[0247]

[0248] When the road surface is free of vehicles and obstacles, let H1 = H0, then the measurement data measured by the laser ranging module satisfies the following formula (9):

[0249]

[0250] Since H1 = H0 = 5.2m, according to the above formula (9), it can be calculated that:

[0251]

[0252]

[0253]

[0254] When the road surface has a large truck or a large obstacle, let H2 = H0-H, then the measurement data measured by the laser ranging module satisfies the following formula (10):

[0255]

[0256] Since H1 = H0-H = 1.2m, according to the above formula (9), it can be calculated that:

[0257]

[0258]

[0259]

[0260] The range of the preset threshold is as follows formula (11):

[0261]

[0262] Wherein, L 长 , L 中 and L 短 are L1, L2 and L3 in the preset threshold range.

[0263] That is:

[0264] 130.006m < L 长 < 130.105m;

[0265] 68.512 < L 中 < 68.698m;

[0266] 7.113 < L 短 < 8.729m.

[0267] Due to the error and other factors, L1 is 120.000-140.000m, L2 is 65.000-75.000m, and L3 is 6.000-9.500m, that is:

[0268] 120.000m≤L1≤140.000m;

[0269] 65.000m≤L2≤75.000m;

[0270] 6.000m≤L3≤9.500m.

[0271] The preset threshold range is determined, and then the actual distance data measured by formula (8) is judged whether it falls within the preset threshold range, that is, the process of the single-chip module judging whether the measurement data exceeds the preset threshold is specifically:

[0272] If at least one of the first distance L1, the second distance L2 and the third distance L3 measured by the laser ranging module falls within the preset threshold range, it is preliminarily judged that the traffic sign is blocked, and the preliminary judgment result and the measurement data are transmitted to the self-checking module together with the position and the elevation information of the laser ranging module obtained by the Beidou positioning module for further judgment of the blocking object. In the embodiment, whether the actual measurement distance falls within the preset threshold range can be realized by the built-in program of the single-chip pre-programmed, and the single-chip built-in program receives the distance data measured and transmitted by the laser ranging module, compares the distance data with the preset threshold range set in advance, and preliminarily judges whether the distance data meets the condition that the traffic sign is not blocked.

[0273] In the embodiment, the background terminal is also included, and the self-checking module is specifically used for:

[0274] Receiving the preliminary judgment result, controlling the laser ranging module to perform continuous laser ranging for the first preset number of times at a second time interval to obtain the first distance L1, the second distance L2 and the third distance L3 for the first preset number of times, and the second time interval is less than the first time interval.

[0275] Judging the number of times that the actual distance for the first preset number of times does not fall within the preset threshold, if the number of times is less than a second preset number of times, the secondary judgment is that the traffic sign is not blocked, and the secondary judgment result and the measurement data are sent to the background terminal;

[0276] Otherwise, the secondary judgment is that the traffic sign is blocked, and the reason for the traffic sign being blocked is judged according to the position, the elevation information and the measurement data, and the secondary judgment result, the reason and the measurement data are sent to the background terminal;

[0277] The reasons include tree blocking, device angle deviation, device falling off and device failure.

[0278] In the embodiment, for example, the self-checking module initiates continuous ten times of laser ranging, wherein each ranging interval is 30s (i.e. the second time interval), if the data of x times or more than x times in the ten times of detection are in the preset range, it is judged that the traffic signboard is not blocked, and the data and the judgment result are transmitted to the background terminal; if y times or more than y times are not in the range, it is judged that the traffic signboard is blocked, and then the self-checking module further analyzes the reason why the traffic signboard is blocked in combination with the position and the elevation information of the laser ranging module, and then the data, the judgment result and the reason are transmitted to the background terminal.

[0279] That is, the actual distance measured by the first time interval falling within the range of the preset threshold value is taken as the preliminary judgment result of whether the traffic signboard is blocked, in order to avoid the traffic signboard being blocked under accidental circumstances (such as a bird flying in front of the traffic signboard and being measured by the laser ranging module, etc.), therefore, the self-checking module is used to perform continuous multiple laser ranging in the second time interval, so as to further determine whether the traffic signboard is truly blocked by the number of times of the multiple ranging results falling out of the range of the preset threshold value, so as to ensure the accuracy of the blocking detection; meanwhile, after it is determined that the traffic signboard is blocked, the reason why the traffic signboard is blocked needs to be further judged according to the position, the elevation information of the laser ranging module and the multiple measurement data measured under the blocking, whether the traffic signboard is blocked by the street tree or the device angle of the laser ranging module is deviated, the device is fallen off or caused by the fault, which further ensures the accuracy of the blocking detection, and is convenient for the background terminal to give corresponding alarm and maintenance notice according to the blocking reason.

[0280] Meanwhile, the background terminal is specifically used for:

[0281] receiving the secondary judgment result, if the secondary judgment result is that the traffic signboard is blocked, sending alarm and maintenance notice to relevant personnel according to the reason why the traffic signboard is blocked.

[0282] When the reason is that the traffic signboard is blocked by the street tree, the size of the first time interval is adjusted and the period of notifying the relevant personnel to trim the street tree according to the current season and the number of times of the actual distance falling within the range of the preset threshold value in the continuous laser ranging.

[0283] That is, in order to save the power consumption of the laser ranging module and improve the service life thereof, the first time interval of the laser ranging module for regular ranging and the period of notifying the relevant maintenance personnel to trim the street tree are adjusted according to the different growth conditions of the street tree in different seasons and the reason why the traffic signboard is blocked by the street tree, which greatly improves the efficiency of road facility maintenance.

[0284] In the embodiment, it is worth noting that, for example, Figure 3As shown, the laser ranging module can be powered by a built-in solar cell to realize ranging work, and in order to reduce the loss of power, a timer is set in the single-chip microcomputer built-in program to set the ranging frequency of the laser ranging module. The ranging frequency can be set in combination with the different seasonal conditions of the street trees, that is, the size of the first time interval can be set in two different programs of spring and summer, autumn and winter. For example, three days are set as a cycle in spring and summer, and six days are set as a cycle in autumn and winter. After combining the shielding times data of the traffic signboards shielded due to the growth of the street trees received by the background terminal, the shielding data can be analyzed to adjust the size of the first time interval, that is, to adjust the cycle of the laser ranging module for timing ranging. For example, if the feedback result of the number of times of shielding is greater than 3 times in 10 times of starting ranging, then the cycle of two days in spring and summer is modified, the cycle of four days in autumn and winter is modified, and the cycle of the maintenance personnel for pruning the street trees is also modified to maximize the avoidance of the shielding of the traffic signboards. The frequency can also be set and modified by the relevant personnel through the background terminal.

[0285] In addition, it is worth noting that in the present embodiment, an intelligent detection module is also provided, which can detect the battery power of the laser ranging module before each start of the entire ranging system, and combine the position and elevation information in the Beidou positioning module through the self-checking module. Through the single-chip microcomputer built-in program, the elevation detected at the initial system start is combined for self-checking, the position, elevation information, power and fluctuation range of data in the laser ranging process are analyzed, the conditions in the database are compared for judgment, if the elevation error exceeds 10 cm, the judgment result is that the laser ranging module is detached; if the battery current is lower than 20%, it is judged that the power of the laser ranging module is insufficient; if y times or more than y times of laser ranging data are not within the preset threshold range, it is judged that the laser ranging module is shielded, the device angle is deviated or fails, etc. After the specific result is judged, the result is transmitted to the background terminal together with the position and elevation information of the Beidou positioning module, and the relevant department personnel are notified to handle.

[0286] In summary, the signboard shielding detection method and system based on laser ranging provided by the present application have the following beneficial effects:

[0287] (1) Compared with the traditional manual on-site inspection and pruning, the efficiency and accuracy are greatly improved, the time and maintenance cost of road maintenance personnel are reduced, the traffic accident rate is reduced to a certain extent, and the traffic operation efficiency is improved.

[0288] (2) Intelligent detection can be realized to detect whether the traffic signboard is shielded, and multiple traffic signboards can be detected at the same time, and the data can be processed. The instrument has low cost, long service life, saves cost, saves manpower, and has high efficiency.

[0289] (3) The system power supply is solved by using solar cells, renewable energy utilization is realized, no external line is needed, battery replacement is not needed in general cases except battery damage, cost and material are saved, and installation is fast and convenient.

[0290] (4) The problem that a person cannot see traffic signs due to the obstruction of trees during travel is solved, and the problem that the relevant traffic department personnel waste human resources by manually checking the obstruction of the signs is solved.

[0291] (5) The Beidou positioning system accurately positions the obstructed sign and sends information to the background server in real time to ensure that the obstructed sign can be accurately positioned.

[0292] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent transformation or direct or indirect application in the related technical field using the content of the present application specification and drawings is also included in the patent protection scope of the present application.

Claims

1. A sign occlusion detection method based on laser ranging, characterized by, The method comprises the steps of: S1, obtaining the measurement data of the laser ranging module on the traffic sign at a first time interval; S2, determining whether there is measurement data of the front object and whether the measurement data is within a preset threshold range, if so, entering step S3; S3, obtaining the position and elevation information of the laser ranging module; S4, determining whether the traffic sign is blocked according to the position, the elevation information and the measurement data; L1 is the data measured by the laser ranging module when the minimum angle with the ground, recorded as the first distance, the minimum angle range is 0~30°, L2 is the data measured by the laser ranging module when the medium angle with the ground, recorded as the second distance, the medium angle range is 31~60°, L3 is the data measured by the laser ranging module when the maximum angle with the ground, recorded as the third distance, the maximum angle range is 61~90°; The step S2 is specifically: If at least one of the first distance L1, the second distance L2 and the third distance L3 measured by the laser ranging module falls within the range of the preset threshold, it is preliminarily determined that the traffic sign is blocked, and step S3 is entered; The step S4 is specifically: S41, receiving the result of the preliminary determination, controlling the laser ranging module to perform continuous laser ranging for a first preset number of times at a second time interval, obtaining the first distance L1, the second distance L2 and the third distance L3 for the first preset number of times, the second time interval is less than the first time interval; S42, determining the number of times that the actual distance for the first preset number of times does not fall within the preset threshold, if the number of times is less than a second preset number of times, it is determined that the traffic sign is not blocked, and the secondary determination result and the measurement data are sent to the background terminal; Otherwise, it is determined that the traffic sign is blocked, and the reason for the traffic sign being blocked is determined according to the position, the elevation information and the measurement data, and the secondary determination result, the reason and the measurement data are sent to the background terminal; The reason includes tree blocking, device angle deviation, device falling and device failure.

2. The sign occlusion detection method based on laser ranging according to claim 1, wherein, The step S1 further comprises calculating the preset threshold, and the calculation process is as follows: The distance of the vehicle running from the time when the driver cannot see the content of the traffic sign to the time when the driver can see and start reading the content of the traffic sign is acquired in advance, and is recorded as a discovery distance S a : （1）； Wherein, V0 is the vehicle speed at the beginning of discovery, t1 is the time of discovering the traffic sign; acquiring a distance traveled by the vehicle during a time period from when the driver starts reading the sign content to when the driver finishes understanding and prepares to start action, denoted as reading distance S b : （2）； Wherein, t2 is the time of reading the sign content; acquiring a distance of vehicle travel by the driver from the beginning of the decision to the end of the decision, denoted as decision distance S c : （3）； Wherein, t3 is the decision time; acquiring a distance traveled by the vehicle from when the driver ends the decision to when the driver starts to operate the vehicle, denoted as a reaction distance S d : （4）； Wherein, t4 is the time of operation reaction; The distance of the vehicle running from the beginning of operation to the operation interval is obtained, recorded as the action distance Se: （5）； Wherein, n is the number of lanes, V1 is the design speed, Q is the traffic volume under the design speed of the second level of service; The distance from the driver's visual field to the message of the traffic sign is the visual disappearance distance S f : （6）； Wherein, H is the lateral distance from the driver's line of sight to the traffic sign, H0 is the height of the traffic sign, H vehicle is the vehicle height, and a is the horizontal angle between the traffic sign vanishing point and the roadside traffic sign; Assuming that the driving distance without deceleration during the time from discovering the traffic sign to completing the reaction is S1: （7）； The measurement data measured by the laser ranging module satisfies formula (8) as follows: （8）； When the road surface is free of vehicles and obstacles, let H1=H0, and the measurement data measured by the laser ranging module satisfies formula (9) as follows: （9）； When the road surface has large trucks or large obstacles, let H2=H0-H, and the measurement data measured by the laser ranging module satisfies formula (10) as follows: （10）； The range of the preset threshold is obtained as formula (11) as follows: （11）； Wherein, Llong, Lmedium and Lshort are L1, L2 and L3 within the range of the preset threshold. 3.The sign occlusion detection method based on laser ranging according to claim 1, wherein, The step S4 further includes steps of: S51, the background terminal receives the secondary judgment result, and if the secondary judgment result is that the traffic sign is blocked, an alarm and maintenance notice are sent to relevant personnel according to the reason for being blocked; S52, when the reason is that the traffic sign is blocked by a street tree, the size of the first time interval and the period of notifying relevant personnel to trim the street tree are adjusted according to the current season and the number of times that the actual distance measured in continuous laser ranging falls within the range of the preset threshold.

4. A sign occlusion detection system based on laser ranging, characterized in that, The system comprises a laser ranging module, a single-chip microcomputer module, a Beidou positioning module and a self-checking module; The laser ranging module is installed on the traffic sign and performs laser ranging at a first time interval to obtain measurement data; The single-chip microcomputer module acquires the measurement data and judges whether the measurement data of the front object exists and whether the measurement data is within a preset threshold range, and if so, the measurement data is sent to the self-checking module; The Beidou positioning module is used to acquire the position and elevation information of the laser ranging module when the measurement data exceeds the preset threshold, and send the information to the self-checking module; The self-checking module judges whether the traffic sign is blocked according to the position, the elevation information and the measurement data; L1 is the data measured by the laser ranging module when the smallest angle with the ground, recorded as the first distance, the range of the smallest angle is 0-30°, L2 is the data measured by the laser ranging module when the medium angle with the ground, recorded as the second distance, the range of the medium angle is 31-60°, and L3 is the data measured by the laser ranging module when the largest angle with the ground, recorded as the third distance, the range of the largest angle is 61-90°. The single-chip microcomputer module judges whether the measurement data exceeds the preset threshold, specifically: If at least one of the first distance L1, the second distance L2 and the third distance L3 actually measured by the laser ranging module falls within the range of the preset threshold, it is preliminarily judged that the traffic sign is blocked, and the preliminary judgment result is sent to the self-checking module; The system further comprises a background terminal, and the self-checking module is specifically used for: Receiving the preliminary judgment result, controlling the laser ranging module to perform continuous laser ranging for a first preset number of times at a second time interval, obtaining the first distance L1, the second distance L2 and the third distance L3 for the first preset number of times, and the second time interval is smaller than the first time interval; If the number of times is less than the second preset number of times, it is determined that the traffic sign is not blocked, and the second determination result and the measurement data are sent to the background terminal; Otherwise, it is determined that the traffic sign is blocked, and a reason for the traffic sign being blocked is determined according to the position, the height information and the measurement data, and the second determination result, the reason and the measurement data are sent to the background terminal; The reason includes tree blocking, device angle deviation, device falling and device failure.

5. The sign obscuration detection system based on laser ranging of claim 4, wherein, The laser ranging module is further configured to calculate the preset threshold value, and the calculation process is as follows: The distance of the vehicle running from the time when the driver cannot see the content of the traffic sign to the time when the driver can see and start reading the content of the traffic sign is pre-acquired as a discovery distance S a : （1）； Wherein, V0 is the vehicle speed at the beginning of discovery, and t1 is the time of discovering the traffic sign; acquiring a distance traveled by the vehicle during a time period from when the driver starts reading the sign content to when the driver finishes understanding and prepares to start action, denoted as reading distance S b : （2）； Wherein, t2 is the time of reading the sign content; acquiring a distance of vehicle travel by the driver from the beginning of the decision to the end of the decision, denoted as decision distance S c : （3）； Wherein, t3 is the decision time; acquiring a distance traveled by the vehicle from when the driver ends the decision to when the driver starts to operate the vehicle, denoted as a reaction distance S d : （4）； Wherein, t4 is the time of operation reaction; acquiring a distance traveled by the vehicle from the start of the operation by the driver to the operation of the inter-vehicle medium, denoted as action distance S e : （5）； Wherein, n is the number of lanes, V1 is the design speed, and Q is the traffic volume of the second level of service under the design speed; The distance from the driver's visual field to the message of the traffic sign is the visual disappearance distance S f : （6）； Wherein, H is the lateral distance from the driver's line of sight to the traffic sign, H0 is the height of the traffic sign, Hcar is the vehicle height, and a is the horizontal angle between the traffic sign vanishing point and the roadside traffic sign; Assuming that the driving distance of the driver from discovering the traffic sign to completing the reaction without deceleration in the middle is S1: （7）； The measurement data measured by the laser ranging module satisfies the following formula (8): （8）； When there is no car and no obstacle on the road surface, let H1=H0, then the measurement data measured by the laser ranging module satisfies the following formula (9): （9）； When there is a large truck or a large obstacle on the road surface, let H2=H0-H, then the measurement data measured by the laser ranging module satisfies the following formula (10): （10）； The range of the preset threshold value is obtained as follows: （11）； Wherein, Llong, Lmedium and Lshort are L1, L2 and L3 in the range of the preset threshold value.

6. The sign obscuration detection system based on laser ranging of claim 4, wherein, The background terminal is specifically configured to: Receive the second determination result, and if the second determination result is that the traffic sign is blocked, send an alarm and maintenance notice to relevant personnel according to the reason for being blocked; When the reason is tree blocking, adjust the size of the first time interval and notify relevant personnel to trim the trees according to the current season and the number of times that the actual distance measured in continuous laser ranging falls within the preset threshold value.

Images