Vehicle overall dimension measuring method

Abstract

The invention relates to the technical field of vehicle detection, and particularly discloses a vehicle overall dimension measurement method. The method comprises the following steps: 1, respectively installing a left laser radar and a right laser radar on two sides of a detection area where a vehicle runs, 2, unifying point cloud data sets collected by the left laser radar and the right laser radar to the same coordinate, and denoising the point cloud data according to a set threshold range to obtain a left point cloud data set L and a right point cloud data set R; 3, subtracting the X coordinate of the R from the X coordinate of the L to obtain the width of the vehicle; obtaining a Z coordinate value from the data set R or L to obtain the height of the vehicle; 4, detecting the time T1 and T2 of the vehicle entering and exiting the detection area through the left laser radar and the right laser radar; the photoelectric switch array measures the average speed V of the vehicle, and the vehicle length is obtained through calculation according to a formula; and 5, measuring the wheelbase of the vehicle through the photoelectric switch array. The objective of the invention is to solve the problems that three laser radars are adopted to measure the overall dimension of a vehicle, the required vehicle site is large, and the equipment cost is high.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle detection, and in particular to a method for measuring the outer dimensions of a vehicle. Background Art

[0002] Since the production and use of vehicles are difficult to be standardized and controlled, illegal splicing and assembly of vehicles often occur, resulting in vehicles that are too long, too wide, and too high. Over-limit is the main factor causing vehicle overload transportation, which can easily lead to traffic accidents and damage road facilities. At present, most vehicle management offices and motor vehicle inspection agencies in my country use manual measurement methods when inspecting the outer dimensions of vehicles, and sometimes they can only rely on visual inspection based on experience. This method not only has large errors and low efficiency, but also has high labor intensity and a high rate of missed inspections, and it is even impossible to perform dynamic inspections on vehicles in operation.

[0003] With the issuance of national standards, it is stipulated that automobile inspection stations need to use automatic measuring instruments for vehicle outline dimensions to accurately detect the outline dimensions of non-operating motor vehicles, and require that the measurement error of the outline dimensions of trucks should not exceed ±3% or ±150mm to ensure the accuracy and consistency of the measurement results. Various manufacturers have developed automatic measuring instruments for vehicle outline dimensions with laser radar as the core. These high-precision instruments are usually equipped with three laser radar devices, which work together to accurately measure the length, width and height of the vehicle. Among them, the laser radars on the left and right sides are responsible for measuring the width and height of the vehicle, while the front laser radar is specifically used to measure the length of the vehicle. As a measuring device, laser radar is relatively expensive; although the use of three laser radars meets the detection accuracy requirements, the price is relatively high, and three laser radars also require large venues to arrange measurement sites. Summary of the invention

[0004] In view of the shortcomings of the prior art, the technical problem solved by the present invention is to provide a vehicle outline dimension measurement method to solve the problem that the prior art vehicle outline dimension measurement uses three laser radars for measurement, which requires a large vehicle site and has high equipment costs.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is: a vehicle outline dimension measurement method, comprising the following steps; S100: The left and right laser radars are installed on both sides of the detection area where the vehicle is traveling; S200: Unify the point cloud data sets collected by the left and right lidars to the same coordinates, and then denoise the point cloud data according to the set threshold range to obtain the left point cloud data set L and right point cloud dataset R ; S300: By dividing the data set R The X coordinate in LSubtract the X coordinate from the data set to get the vehicle width; R or L Get the Z coordinate value and get the vehicle height; S400: The time T1 when the vehicle enters the detection area and the time T2 when the vehicle leaves the detection area are detected by the left and right laser radars; the photoelectric switch arrays are deployed at both ends of the detection area to measure the average speed V of the vehicle, and the length of the vehicle is determined by the formula Calculate and obtain the vehicle length; S500: There are two groups of photoelectric switches, which are arranged in the vertical direction of the vehicle's travel direction, and measure the two front wheels or the two rear wheels at the same time. There are n photoelectric switches in one group of photoelectric switches, and the distance between adjacent photoelectric switches is fixed to s. The time for the front and rear wheels of the vehicle to pass through n photoelectric switches in sequence is recorded as ~ , the average speed calculation formula is:

[0006] The average time required for a vehicle to travel one wheelbase is calculated as follows;

[0007] The calculation formula of wheelbase is: .

[0008] The beneficial effects of this solution are: by adopting the detection scheme of this solution, two laser radars are used in conjunction with photoelectric switches to detect the width, height and length of the vehicle; at the same time, the photoelectric switch is used to detect the wheelbase of the vehicle and accurately measure the outer dimensions of the truck. Compared with the traditional solution of using three laser radars, this method can not only effectively reduce the required measurement site area, but also significantly reduce the purchase and maintenance costs of the detection equipment. In addition, through the calculation of this solution, the error of the measured vehicle outer dimensions can be controlled within ±2%, which fully meets the outer dimension measurement requirements of existing trucks, and the measurement accuracy is higher. Whether it is a large truck or a small truck, this method can be used to quickly and accurately measure the outer dimensions.

[0009] Further, in step S200, the width value W is calculated by using the improved K frame calculation method, and the left radar is calculated by each K 1 frame is grouped, N 1= n / K 1 indicates the number of left lidar point cloud data groups, K 1 value is preset; similarly, the right radar is set to K 2 frames are grouped, N 2= m / K2 represents the number of right lidar point cloud data groups. K 2 The value is preset; the calculation model is as follows;

[0010] xij express L Middle i Frame No. j Point cloud data x Coordinate value, Θ represents a certain operation, xlt express XL Θ t The result value obtained after the Θ operation in the set of point cloud data frames, XL Θ represents all N 1 set of result values; xks yes R Middle k Frame No. s Point cloud data x Coordinate value, Λ represents a certain operation, xrt express XR Λ s The result value obtained after the Λ operation of the set of point cloud data frames, XR Λ represents all N A set of 2 result values; Γ represents a certain operation; Θ and Λ use any one of the operations of min, max and mean, min and max represent the minimum and maximum values ​​respectively, and mean represents the average value.

[0011] Considering that the left and right lidar acquisitions are often not synchronized, random errors will be introduced if single-frame subtraction is used. By adopting the improved K-frame calculation method of this scheme, the vehicle width measurement error can be effectively reduced, thereby overcoming the random errors caused by asynchronous acquisition.

[0012] Further, the specific calculation method of Γ is:

[0013] or .

[0014] This method of calculation has low requirements on the vehicle's driving trajectory. Even if the vehicle tilts slightly when passing through the detection area, the calculated error is low, so the actual width of the vehicle can be effectively measured.

[0015] Further, in step S400, it is determined whether the vehicle enters or leaves the detection area through the following steps: S401: merging the point cloud data obtained by the left and right laser radars into the same coordinate system; S402: Find the minimum X coordinate value in the merged point cloud data and record it as x min, the maximum value of the X coordinate is recorded as x max; then the width of the object in the detection area at the left and right laser radar scanning planes is recorded as wt , wt = x max - x min. when wt Greater than threshold w 0, that is wt > w 0, the vehicle is judged to have entered the detection area; if wt from wt > w 0 becomes wt < w 0, it is judged that the vehicle has left the detection area. By detecting the width changes of the two radars at the same coordinate, the vehicle entering the detection area can be sensed in time, so as to accurately record the time for measurement.

[0016] Furthermore, in step S500, a group of photoelectric switches is provided with 4. By providing 4 photoelectric switches, the general wheelbase measurement accuracy requirements can be basically met, and the detection cost can be reduced.

[0017] Furthermore, the distance S between two adjacent photoelectric switches in step S500 ranges from 8 to 15 cm. By setting a suitable photoelectric switch spacing, the actual vehicle wheelbase can be effectively measured to avoid the wheels blocking multiple photoelectric switches at the same time when the distance is too close, and the front and rear wheels of the vehicle passing through a group of photoelectric switches at the same time when the distance is too far. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a vehicle not entering the laser radar detection area; Figure 2 This is a schematic diagram of a vehicle entering the laser radar detection area; Figure 3 This is a schematic diagram of the photoelectric switch group layout; Figure 4 Schematic diagram of the process of the bottom of the vehicle passing through the photoelectric switch. DETAILED DESCRIPTION

[0019] The following is further described in detail through specific implementation methods: Example 1 This is as attached Figures 1 - 4 As shown: A method for measuring the outer dimensions of a vehicle, comprising the following steps; S100: The left and right laser radars are installed on both sides of the detection area where the vehicle is traveling; S200: Unify the point cloud data sets collected by the left and right lidars to the same coordinates, and then denoise the point cloud data according to the set threshold range. The threshold range is set as the height range value, and the point cloud data near the ground or significantly higher than the top of the car can be initially removed to obtain the left point cloud data set. L and right point cloud dataset R ; S300: By dividing the data set R The X coordinate in L Subtract the X coordinate from the data set to get the vehicle width; R or L Get the Z coordinate value and get the vehicle height; S400: The time T1 when the vehicle enters the detection area and the time T2 when the vehicle leaves the detection area are detected by the left and right laser radars; the photoelectric switch arrays are deployed at both ends of the detection area to measure the average speed V of the vehicle, and the length of the vehicle is determined by the formula Calculate and obtain the vehicle length; Determine whether a vehicle enters or leaves the detection area through the following steps; S401: merging the point cloud data obtained by the left and right laser radars into the same coordinate system; S402: Find the minimum X coordinate value in the merged point cloud data and record it as x min, the maximum value of the X coordinate is recorded as x max; then the width of the object in the detection area at the left and right laser radar scanning planes is recorded as wt , wt = x max - x min. when wt Greater than threshold w 0, that is wt > w 0, the vehicle is judged to have entered the detection area; if wt from wt > w 0 becomes wt < w 0, it is judged that the vehicle leaves the detection area.

[0020] S500: Two groups of photoelectric switches are arranged, and the two groups of photoelectric switches are arranged in a direction perpendicular to the direction of vehicle travel, respectively measuring two front wheels or two rear wheels at the same time. Four photoelectric switches are arranged in one group of photoelectric switches, and the distance between adjacent photoelectric switches is fixed to s. In this embodiment, the value of s is 10 cm. The time for the front wheels and rear wheels of the vehicle to pass through the four photoelectric switches in sequence is recorded as ~ , the average speed calculation formula is:

[0021] The average time required for a vehicle to travel one wheelbase is calculated as follows;

[0022] The calculation formula of wheelbase is: .

[0023] In step S200, the width value W is calculated by using the improved K frame calculation method, and the left radar is K 1 frame is grouped, N 1= n / K 1 indicates the number of left lidar point cloud data groups, K 1 value is preset; similarly, the right radar is set to K 2 frames are grouped, N 2= m / K 2 represents the number of right lidar point cloud data groups. K 2 The value is preset; the calculation model is as follows;

[0024] xij express L Middle i Frame No. j Point cloud data x Coordinate value, Θ represents a certain operation, xlt express XL Θ t The result value obtained after the Θ operation in the set of point cloud data frames, XL Θ represents all N 1 set of result values; xks yes R Middle k Frame No. s Point cloud data x Coordinate value, Λ represents a certain operation, xrt express XR Λ s The result value obtained after the Λ operation of the set of point cloud data frames, XR Λ represents all N A set of 2 result values; Γ represents a certain operation; Θ and Λ use any one of the operations of min, max and mean, min and max represent the minimum and maximum values ​​respectively, and mean represents the average value.

[0025] Considering that the left and right lidar acquisitions are often not synchronized, random errors will be introduced if single-frame subtraction is used. By adopting the improved K-frame calculation method of this scheme, the vehicle width measurement error can be effectively reduced, thereby overcoming the random errors caused by asynchronous acquisition.

[0026] The specific calculation method of Γ is

[0027] or .

[0028] This method of calculation has low requirements on the vehicle's driving trajectory. Even if the vehicle tilts slightly when passing through the detection area, the calculated error is low, so the actual width of the vehicle can be effectively measured.

[0029] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for measuring vehicle external dimensions, Features: The steps include: S100: The left and right laser radars are installed on both sides of the detection area where the vehicle is traveling; S200: Unify the point cloud data sets collected by the left and right lidars to the same coordinates, and then denoise the point cloud data according to the set threshold range to obtain the left point cloud data set L and right point cloud dataset R ; S300: By dividing the data set R The X coordinate in L Subtract the X coordinate from the data set to get the vehicle width; R or L Get the Z coordinate value and get the vehicle height; S400: The time T1 when the vehicle enters the detection area and the time T2 when the vehicle leaves the detection area are detected by the left and right laser radars; the photoelectric switch arrays are deployed at both ends of the detection area to measure the average speed V of the vehicle, and the length of the vehicle is determined by the formula Calculate and obtain; S500: There are two groups of photoelectric switches, which are arranged in the vertical direction of the vehicle's travel direction, and measure the two front wheels or the two rear wheels at the same time. There are n photoelectric switches in one group of photoelectric switches, and the distance between adjacent photoelectric switches is fixed to s. The time for the front and rear wheels of the vehicle to pass through n photoelectric switches in sequence is recorded as ~ , the average speed calculation formula is; The average time required for a vehicle to travel one wheelbase is calculated as follows; The calculation formula of wheelbase is: .

2. A vehicle external dimension measuring method according to claim 1, Features: In step S200, the width value W is calculated by using the improved K frame calculation method, and the left radar is divided into K 1 frame is grouped, N 1= n / K 1 indicates the number of left lidar point cloud data groups, K 1 value is preset; similarly, the right radar is set to K 2 frames are grouped, N 2= m / K 2 represents the number of right lidar point cloud data groups. K 2 The value is preset; the calculation model is as follows; xij express L Middle i Frame No. j Point cloud data x Coordinate value, Θ represents a certain operation, xlt express XL Θ t The result value obtained after the Θ operation in the set of point cloud data frames, XL Θ represents all N 1 set of result values; xks yes R Middle k Frame No. s Point cloud data x Coordinate value, Λ represents a certain operation, xrt express XR Λ s The result value obtained after the Λ operation of the set of point cloud data frames, XR Λ represents all N A set of 2 result values; Γ represents a certain operation; Θ and Λ use any one of the operations of min, max and mean, min and max represent the minimum and maximum values ​​respectively, and mean represents the average value.

3. A vehicle external dimension measuring method according to claim 2, Features: The specific calculation method of Γ is: or 。 4. A vehicle external dimension measurement method according to claim 1, Features: In step S400, the following steps are performed to determine whether a vehicle enters or leaves the detection area: S401: merging the point cloud data obtained by the left and right laser radars into the same coordinate system; S402: Find the minimum X coordinate value in the merged point cloud data and record it as x min, the maximum value of the X coordinate is recorded as x max; then the width of the object in the detection area at the left and right laser radar scanning planes is recorded as wt , wt = x max - x min. when wt Greater than threshold w 0, that is wt > w 0, the vehicle is judged to have entered the detection area; if wt from wt > w 0 becomes wt < w 0, it is judged that the vehicle leaves the detection area.

5. A vehicle external dimension measurement method according to claim 1, Features: In step S500, a group of photoelectric switches is provided with four.

6. A vehicle external dimension measurement method according to claim 1, Features: In step S500, the distance S between two adjacent photoelectric switches ranges from 8 to 15 cm.

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