CN114562952A - Tire pattern depth measuring method, and all-round pattern depth measuring method and system - Google Patents
Tire pattern depth measuring method, and all-round pattern depth measuring method and system Download PDFInfo
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- CN114562952A CN114562952A CN202210256876.7A CN202210256876A CN114562952A CN 114562952 A CN114562952 A CN 114562952A CN 202210256876 A CN202210256876 A CN 202210256876A CN 114562952 A CN114562952 A CN 114562952A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/22—Measuring arrangements characterised by the use of optical techniques for measuring depth
Abstract
The invention relates to tire pattern depth measurement, in particular to a tire pattern depth measurement method, a full-circle pattern depth measurement method and a system. A method for measuring a pattern depth of a tire, comprising the steps of: measuring a distance L1 from the outer surface of the tread to the transmitting unit and a distance L2 from the bottom surface of the pattern to the transmitting unit by using the fixedly arranged transmitting unit and the fixedly arranged receiving unit by adopting a trigonometry method; the method comprises the steps of obtaining an image of the tire by using a fixedly arranged camera, and identifying a circle center coordinate O of the tire side by using a machine vision unit. The invention has the beneficial effects that: the measuring method has higher measuring precision and can measure tires with different sizes.
Description
Technical Field
The invention relates to tire pattern depth measurement, in particular to a tire pattern depth measurement method, a full-circle pattern depth measurement method and a system.
Background
The main function of the automobile tyre pattern is to increase the friction between the tread and the road surface and to drain away the accumulated water so as to prevent the wheel from slipping. Excessive wear of tire patterns can lead to increase of braking distance and decrease of grip force, and further influence of driving safety. Therefore, the requirement that the tire pattern depth of the in-use vehicle is not lower than the limit value is one of important guarantee conditions for safe driving of the automobile.
According to the regulations of GB 38900-2020 Motor vehicle safety technology inspection items and methods, the pattern depth on the tire crown of passenger vehicle and trailer is more than or equal to 1.6mm, and the pattern depth on the tire crown of motorcycle is more than or equal to 0.8 mm; the crown pattern depth of other motor vehicle steering wheels is more than or equal to 3.2mm, and the tire tread wear mark is visible.
Currently, the common tire pattern depth measurement methods are mainly divided into manual measurement and through measurement. Wherein, the manual measurement is that the detector uses a hand-held depth gauge (mechanical or digital display) or a hand-held pattern depth meter to measure. Through measurement, namely the measuring equipment is placed on the ground or buried underground, the vehicle to be measured slowly drives over the measuring equipment, and the pattern depth of the contact position of the surface of the tire of the vehicle and the measuring equipment can be measured.
In the two current measuring modes, manual measurement not only consumes manpower, but also causes difference of measuring results due to different measuring habits (reading estimation of a depth gauge, measuring strength and the like) of different measuring personnel; the pass-type measurement can only measure the pattern depth value of the contact position of the tire and the equipment, and the data is incomplete and cannot represent the pattern depth of the whole circumference of the tire.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a tire pattern depth measuring method, a full-circle pattern depth measuring method and a system.
The invention is realized by the following technical scheme:
a method for measuring a pattern depth of a tire, comprising the steps of:
measuring a distance L1 from the outer surface of the tread to the transmitting unit and a distance L2 from the bottom surface of the pattern to the transmitting unit by using the fixedly arranged transmitting unit and the fixedly arranged receiving unit by adopting a trigonometry method;
obtaining an image of the tire by using a fixedly arranged camera, and identifying a circle center coordinate O of the sidewall by using a machine vision unit;
because the emitting unit and the camera are fixedly arranged, the coordinates and the angle of the emitting light of the emitting unit are known, a linear equation of the emitting light can be obtained, and the intersection point coordinate A of the emitting light and the outer surface of the tread and the intersection point coordinate B of the emitting light and the bottom surface of the pattern can be obtained from the linear equation according to L1 and L2;
then, the true value of the pattern depth L3 can be obtained by two methods:
the first method comprises the following steps: calculating the OA distance and the OB distance by using the coordinates, wherein the difference between the OA distance and the OB distance is calculated to be a true value L3 of the pattern depth;
the second method is as follows: the cosine value cos alpha of the included angle OAB is obtained by utilizing the coordinates of O, A, B, and the product of the cos alpha and the difference between L1 and L2 is the true value L3 of the pattern depth.
According to the above technical solution, preferably, the emitting unit is a line laser emitter.
A method for measuring the depth of a full-circle pattern of a tire adopts the measuring method and measures the full-circle data of the pattern depth in a mode of rotating the tire.
A system for measuring the profile depth of a tire, comprising:
the braking table is used for supporting and limiting the tire;
the first module comprises a transmitting unit and a receiving unit, wherein the transmitting unit is used for transmitting laser to the tire tread, and the receiving unit is used for receiving the laser reflected by the tire tread;
the second module comprises a camera unit and an illumination unit, the camera unit is used for shooting images of the tire side, and the illumination unit is used for supplementing light for the images;
the control unit is used for collecting data output by the first module and the second module and obtaining a real value of the pattern depth according to the measuring mode.
According to the above solution, preferably, the braking station is provided with a pair of parallel rollers.
According to the technical scheme, preferably, a shell is arranged outside the first module, the shell is provided with a window, and the side surface of the window is provided with an air knife.
The invention has the beneficial effects that: the measuring method has higher measuring precision and can measure tires with different sizes;
the system is matched with the brake table for use, the tire pattern depth is detected at the same time of brake detection, the two steps are combined into a whole, the measurement flow is simplified, the mounting structure separated from the brake table is completed, the brake table body is not required to be involved in field construction and later maintenance, and the operability and maintainability are improved;
through the design of matching with the braking table body, the depth of the full-circle pattern of the tire can be measured, which is superior to the situation that the depth of a single section position can only be measured by manual measurement and a pass-through mode;
through the design of self-cleaning function, the test error caused by dirt is reduced in the measuring process, and too frequent manual maintenance is reduced.
Drawings
Fig. 1 shows a schematic diagram of the triangulation principle of an embodiment of the invention.
Fig. 2 shows a schematic view of the profile depth measurement error of an embodiment of the present invention.
Fig. 3 shows a schematic diagram of a first calculation method according to an embodiment of the present invention.
Fig. 4 shows a schematic diagram of a second calculation method of the embodiment of the invention.
Fig. 5 shows a schematic structural diagram of a measurement system according to an embodiment of the present invention.
Fig. 6 shows a first module structure diagram of an embodiment of the invention.
In the figure: 1. the system comprises a first module, 2, a brake table, 3, tires, 4, an air knife, 5, a light supplement lamp, 6, an industrial camera, 7, a control box, 8, a line laser and 9, the industrial camera.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and preferred embodiments.
As shown in the figure, the invention
The first embodiment is as follows:
the transmitting unit adopts a line laser, the receiving unit adopts an industrial camera, and the distance L1 from the outer surface of the tread to the transmitting unit and the distance L2 from the bottom surface of the pattern to the transmitting unit are measured by a trigonometry method.
The trigonometry is as follows:
because the transmitting unit and the receiving unit are fixedly arranged, the length s of a reference line between the transmitting unit and the receiving unit, the focal length f of the industrial camera and the included angle beta between the laser head and the reference line are all known constants.
As shown in fig. 1, the line laser irradiates the object to be measured and reflects the object to the imaging plane of the industrial camera as a point P. The triangle formed by the line laser, the industrial camera and the measured object is similar to the triangle formed by the industrial camera, the point P and the auxiliary point P'. From a similar triangle we can derive: f/x = q/s, i.e. q = fs/x, where x is the separation of P and P'. X can be obtained by summing X1 and X2, wherein X1= f/tan β, and X2 can be read from the distance between the imaging point P and the perpendicular projection point of the industrial camera on the imaging platform. The distance between the line laser and the measured object d = q/sin β = fs/(f/tan β + x2) sin β. The distance L1 from the outer surface of the tread to the transmitting unit and the distance L2 from the bottom surface of the pattern to the transmitting unit can be measured by the above trigonometry.
As shown in fig. 2, since the transmitting unit is fixedly provided and the size (radius or diameter) of the tire is different or the relative position between the tire and the transmitting unit is different for each measurement, the difference between L1 and L2 is not an actual pattern depth and the pattern depth needs to be corrected.
First, an image of the tire sidewall is taken by a camera. Then, recognizing the center coordinate O of the sidewall image by using a machine vision unit, wherein the specific method comprises the following steps:
1. and (3) carrying out image binarization: according to the fact that the materials of the hub and the tire are often greatly different, the gray value of the hub is large, the gray value of the tire is small, and the hub is separated by adopting a self-adaptive threshold value binarization method due to the fact that the materials of the hub are changed.
2. And (3) carrying out contour searching on the binarized picture: the contour is the edge of each connected domain in each image, and because the hub has various patterns, the contour found in the step has a plurality of small contours inside the hub besides the contour of the largest circle of the hub.
3. And (3) screening the profile of the hub from the profiles obtained in the step (2) based on two conditions of the maximum profile area of the hub and one circle, and performing least square fitting on points on the profile to preliminarily obtain a hub fitting circle and a circle center coordinate.
4. And performing sub-pixel extraction on each previously obtained point on the circumference, more accurately obtaining the points on the circumference, and performing least square fitting on the basis of the sub-pixel points to obtain a hub fitting circle and a circle center coordinate.
5. And (5) repeating the step (4), wherein the iteration termination condition is that the coordinate variation of the circle center is less than 0.1 pixel.
Because the emitting unit and the camera are fixedly arranged, the coordinates and the angle of the emitting light of the emitting unit are known, a linear equation of the emitting light can be obtained, and the intersection point coordinate A of the emitting light and the outer surface of the tread and the intersection point coordinate B of the emitting light and the bottom surface of the pattern can be obtained from the linear equation according to L1 and L2;
from the above known quantities, the true value of the pattern depth L3 can be calculated in the following two ways:
as shown in fig. 3, the first method is: calculating the OA distance and the OB distance by using the coordinates, wherein the difference between the OA distance and the OB is calculated to be a true value L3 of the pattern depth;
as shown in fig. 4, the second method is: the cosine value cos alpha of the included angle OAB is obtained by utilizing the coordinates of O, A, B, and the product of the cos alpha and the difference between L1 and L2 is the true value L3 of the pattern depth.
According to the above embodiment, preferably, the data of the full circumference of the pattern depth is measured by rotating the tire.
Example two:
a system for measuring the profile depth of a tire, comprising:
and the braking platform is used for supporting and limiting the tire. The braking platform is the current vehicle detection device, and the braking platform is equipped with a pair of parallel cylinder, can drive the tire rotation, realizes the measurement of full week decorative pattern depth.
The first module is used for completing the triangulation measurement step of the first embodiment. The first module is installed at the front side of the braking table, so that L1 and L2 can be measured conveniently. The first module includes a transmitting unit and a receiving unit. The emitting unit is used for emitting laser to the tire tread, and the emitting unit can adopt a line laser emitter. The receiving unit is used for receiving the laser reflected by the tire surface and consists of an industrial camera, a lens and an optical filter. The first module is externally provided with a shell, the shell is provided with a window, the window is positioned at the transmitting unit and the receiving unit, and the window is provided with hardened glass. The side of the window is provided with an air knife which can clean the glass of the window. In addition, two first modules can be arranged on one brake platform and used for measuring left and right tires of the same vehicle.
And the second module is used for finishing the recognition of the center coordinates O of the sidewall image by the machine vision unit. The second module is installed in the braking platform outside, is convenient for discern the side wall centre of a circle coordinate. The second module includes a camera unit for capturing an image of the sidewall and an illumination unit. The lighting unit is used for supplementing light for the image, and an LED light supplementing lamp can be adopted.
And the control unit is used for collecting the data output by the first module and the second module and obtaining the true value of the pattern depth according to the measuring mode of the first embodiment.
The working principle of the embodiment is as follows:
1. the method comprises the following steps of mounting a first module on a brake table, wherein the mounting direction is that one side of an industrial camera is close to the brake table, mounting a second module on the side of the vehicle running direction, the specific mounting distance is determined by the angle of view of the industrial camera in the second module, and the required view field can shoot the diameter of the whole tire;
2. carrying out integral measurement calibration on the first module and the second module;
3. the vehicle to be tested runs on the roller of the brake platform, and the air bag is controlled to enable the lifting beam to fall down (no measurement is carried out in the lifting process);
4. the roller starts to rotate;
4. the tire pattern depth measuring system receives an external signal for starting measurement, and controls the first module and the second module to simultaneously start working through the industrial personal computer;
5. the linear laser in the first module irradiates the surface of a tire to be measured and the bottom of a groove to form a stripe with a surface profile height difference, the stripe is imaged on a target surface of an industrial camera through an optical filter and a lens, wherein the optical filter can reduce the interference of external stray light on the photographing effect of the industrial camera, an air knife synchronously works to clean the surface of a window of the module, the influence of dirt on the surface of glass on measurement is prevented, and the distance from the surface of the tire to the bottom of the groove, which is measured along the linear laser propagation direction under the incident angle, can be obtained through calculation;
6. an industrial camera in the second module shoots the whole appearance of the tire from the side, the circle center coordinate is determined by extracting diameter information, and the included angle between the incident ray at the incident point and the radial direction can be obtained by calculation;
7. the actual depth of the tire pattern at the measurement position at the photographing time can be obtained through angle correction processing;
8. the depth value of each position of the whole circumference of the tire can be measured due to the continuous rotation of the roller.
The invention has the beneficial effects that: the measuring method has higher measuring precision and can measure tires with different sizes;
the system is matched with the brake table for use, the tire pattern depth is detected at the same time of brake detection, the two steps are combined into a whole, the measurement flow is simplified, the mounting structure separated from the brake table is completed, the brake table body is not required to be involved in field construction and later maintenance, and the operability and maintainability are improved;
through the design of matching with the braking table body, the depth of the full-circle pattern of the tire can be measured, which is superior to the situation that the depth of a single section position can only be measured by manual measurement and a pass-through mode;
through the design of self-cleaning function, the test error caused by dirt is reduced in the measuring process, and too frequent manual maintenance is reduced.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (6)
1. A method for measuring a pattern depth of a tire, comprising the steps of:
measuring a distance L1 from the outer surface of the tread to the transmitting unit and a distance L2 from the bottom surface of the pattern to the transmitting unit by using the fixedly arranged transmitting unit and the fixedly arranged receiving unit by adopting a trigonometry method;
obtaining an image of the tire by using a fixedly arranged camera, and identifying a circle center coordinate O of the sidewall by using a machine vision unit;
obtaining a linear equation of the emitted light through the relative positions of the emitting unit and the camera, and obtaining an intersection point coordinate A of the emitted light and the outer surface of the tread and an intersection point coordinate B of the emitted light and the bottom surface of the pattern according to the linear equations L1 and L2;
the actual value of the pattern depth L3 can be obtained by two methods:
the first method comprises the following steps: calculating the OA distance and the OB distance by using the coordinates, and calculating the difference between the OA distance and the OB distance as a true value L3 of the pattern depth;
the second method is as follows: the cosine value cos alpha of the angle OAB is obtained by using the coordinates of O, A, B, and the product of the cos alpha and the difference between L1 and L2 is the true value L3 of the pattern depth.
2. A method of measuring a profile depth of a tire according to claim 1, wherein: the transmitting unit is a line laser transmitter.
3. A method for measuring a circumferential pattern depth of a tire, using the measuring method according to any one of claims 1 to 2, characterized in that: the full-circle data of the pattern depth is measured by rotating the tire.
4. A system for measuring a profile depth of a tire, comprising:
the braking table is used for supporting and limiting the tire;
the first module comprises a transmitting unit and a receiving unit, the transmitting unit is used for transmitting laser to the tire tread, the receiving unit is used for receiving the laser reflected by the tire tread, and the receiving unit transmits data to the control unit;
the second module comprises a camera unit and an illumination unit, the camera unit is used for shooting images of the tire side, the illumination unit is used for supplementing light for the images, and the camera unit transmits the images to the control unit;
the control unit is used for collecting data output by the first module and the second module and obtaining a real value of the pattern depth according to the measuring mode of any one of claims 1 to 3.
5. A system for measuring the profile depth of a tyre as claimed in claim 4, wherein: the brake table is provided with a pair of parallel rollers.
6. A system for measuring the profile depth of a tyre as claimed in claim 4, wherein: a shell is arranged outside the first module, a window is arranged on the shell, and an air knife is arranged on the side face of the window.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210256876.7A CN114562952A (en) | 2022-03-16 | 2022-03-16 | Tire pattern depth measuring method, and all-round pattern depth measuring method and system |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210256876.7A CN114562952A (en) | 2022-03-16 | 2022-03-16 | Tire pattern depth measuring method, and all-round pattern depth measuring method and system |
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| Publication Number | Publication Date |
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| CN114562952A true CN114562952A (en) | 2022-05-31 |
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| CN202210256876.7A Pending CN114562952A (en) | 2022-03-16 | 2022-03-16 | Tire pattern depth measuring method, and all-round pattern depth measuring method and system |
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- 2022-03-16 CN CN202210256876.7A patent/CN114562952A/en active Pending
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