SYSTEM FOR ASSESSING THE CONDITION OF A TIRE SURFACE

Description

[0001] The invention relates to the field of visual tire inspection. More precisely, the invention concerns a system for assessing the condition of a tire by acquiring a visual image of it. Tires intended for use on vehicles are generally black due to the use of carbon to reinforce the elastomeric compounds from which they are made.

[0002] Therefore, interpreting images acquired using sensors sensitive to light reflection on the tire surface proves particularly challenging. Light effects caused by the tire's texture, grease stains, various blemishes, differences in black tones, or localized discoloration can easily be confused when indiscriminately analyzing the raw image provided by a camera.

[0003] Therefore, the ability to correctly detect surface defects such as stains, scratches, material deficiencies or excess material, or the presence or absence of raised or recessed objects, depends heavily on the lighting applied to the surface, which will result in highlighting the different defects more or less effectively, particularly depending on the distance and angle of incidence of the lighting.

[0004] Several solutions have been proposed to enable the accurate detection of these defects. For example, commercially available acquisition systems based on the principle of stereophotometry enhance the visibility of surface structures. Stereophotometry, as a reminder, is a technique that involves taking N photographs of the same surface under N different lighting conditions.

[0005] The use of such a technique is, for example, described in document EP 2 078 955 B1. Document FR 3 011 079 A1 also describes an optical system for checking the quality of tires.

[0006] However, it was observed that implementing this solution required the use of several sensors whose size made integration difficult. Yet, the goal is generally to install these systems directly at the end of tire production lines, which imposes a number of constraints in terms of space. Furthermore, stereophotometry requires knowledge of the position of the lights, and therefore a relatively precise relative positioning of the lights and tires, otherwise the acquisition and analysis could be distorted.

[0007] The object of the invention is therefore to remedy all of these disadvantages by proposing a complete system for evaluating the surface of a tire allowing good quality detection while representing an acceptable compromise in terms of size.

[0008] Thus, the present invention relates to a system for evaluating the surface area of ​​a tire comprising: an entry zone for the tire into the system, a capture zone, and an exit zone, separate from the entry zone; means for moving and holding a tire in position; means for illuminating the tire, allowing illumination of a sidewall of the tire and the top of a tire in the capture zone; means for acquiring a visual image of the tire in the capture zone; means for processing the acquired image. at least one acquisition means being installed on a movable axis relative to the tire installed in the capture zone, and means for spacing the tire ridges comprising rollers movable in translation on two vertical axes, the two vertical axes being movable in translation on a horizontal axis.

[0009] Having a separate tire entry zone from the exit zone allows a new tire to enter the system while the previously evaluated tire is being exited. This saves cycle time and simplifies logistical management around the system.

[0010] The presence of a movable axis carrying an acquisition means allows the system to be adapted to any tire size, since the acquisition means can be positioned differently depending on the tire width.

[0011] In an advantageous embodiment, the invention relates to a system that also allows visual inspection of the inside of the tire using the same or similar means. Thus, a system, which will be detailed with reference to the figures, will demonstrate a complete inspection of the tire.

[0012] In an example embodiment, the means for setting in motion and holding in position a tire include one or more of the following: means of centering, means of rotation, means of locking the pneumatic, means of linear movement between the entry and exit zone, via the capture zone.

[0013] The means of linear motion make it possible to make the device pass-through, which means that it is easily integrated into a tire conveying line, for example in a tire production plant.

[0014] Centering devices ensure that the image captures the entire tire. Advantageously, these centering devices can be electrically operated, for example using centering rollers.

[0015] The system also includes means for spreading the tire bead. It has been observed that, for certain sized tires, such as heavy-duty tires, the bead can hinder the insertion of data acquisition devices. Therefore, it is useful to provide means for spreading these bead ridges before inserting the data acquisition and / or lighting devices. These spreading means allow the bead ridges to remain in the "open" position throughout the acquisition period and are released before the tire is removed.

[0016] In a preferred embodiment, the acquisition means comprise one or more line-of-sight cameras, and the lighting means are arranged outside the acquisition field of the camera(s). It is specified here that a line-of-sight camera is a camera whose sensor takes the form of a line of pixels.

[0017] A more specific example will be described later with the help of figures.

[0018] In a preferred embodiment, a system according to the invention further includes means for moving the acquisition means. These means allow the cameras to be lowered to the level of the pneumatic tube installed in the capture zone, and then raised again to allow the pneumatic tube to be evacuated. The details of these various operations will be described later with the aid of a timing diagram.

[0019] Preferably, the system also includes a half-mirror, installed to reflect the image of a portion of the tire. This allows two differently oriented areas of the tire to be captured by the same linear camera. Such a device reduces space requirements and therefore costs.

[0020] In an advantageous embodiment, the lighting means comprise individual light sources covered with a diffusing material.

[0021] This type of material improves lighting uniformity and reduces potential glare on the tire surface. Indeed, uniform lighting is particularly important in linear data acquisition systems.

[0022] In an advantageous embodiment, the means for lighting a sidewall of the tire comprise individual light sources arranged along a curve corresponding approximately to the curvature of a sidewall of the tire.

[0023] Individual devices include, for example, light-emitting diodes.

[0024] In one embodiment, the means for processing the acquired image include artificial intelligence means.

[0025] Preferably, artificial intelligence adapted to multimodal, multi-resolution processing will be used. This means that the same processing can be applied to images taken using different modalities, and which therefore do not necessarily have the same resolution, without any problems. This allows for the acquisition of the complete tire image in a single cycle, without taking into account interference between the different sensors. Furthermore, the use of artificial intelligence eliminates the stereo reconstruction step that was previously required, thus saving cycle time.

[0026] In one embodiment, a system according to the invention includes means for positioning acquisition and / or lighting means.

[0027] The invention also relates to a method for evaluating the surface area of ​​a tire using a system according to the invention, the method comprising a step of entering the tire into the evaluation system, a step of rotating the tire in the capture zone of the system, a step of acquiring visual images of the top and sidewalls of the tire, a step of acquiring a visual image of the tire, during a complete rotation of a tire, a step of exiting the tire from the evaluation system, in which the step of acquiring a visual image of the tire is carried out during a rotation of one turn of the tire, and in that the step of exiting the tire is concomitant with a step of entering another tire into the system.

[0028] Such a process saves cycle time, since part of a cycle is carried out at the same time as, or even before, the end of the previous cycle.

[0029] In an advantageous embodiment, the process includes a step of illuminating the sidewalls and crown of the tire. This illuminating step will be described in detail later with the aid of figures.

[0030] In an advantageous embodiment, a process according to the invention further includes a step of separating the beads, prior to the acquisition step.

[0031] In an advantageous embodiment, a method according to the invention further includes a step for processing the acquired image. This processing can take place in parallel with the other steps of the method, since it does not require the presence of the pneumatic system in the evaluation system.

[0032] The processing includes a preliminary image preparation step.

[0033] Therefore, if the image is acquired using stereophotometry, it is useful to include a stereo reconstruction step to account for the differences between the images. However, this step is unnecessary if the processing methods employ artificial intelligence, as described previously.

[0034] The preliminary image preparation stage may also include sub-image segmentation, which allows processing to begin as early as possible and thus reduces cycle time. This stage may also include a registration step.

[0035] The processing then includes a step to evaluate the surface condition. This step can use various known image analysis methods, such as deep learning or traditional image processing techniques (filtering, segmentation, etc.).

[0036] Other examples of implementation will be described, without limitation, using figures, including: [Fig 1 ] There figure 1 represents a schematic diagram of stereophotometry, [ Fig 2 ] there figure 2 shows an example of a machine corresponding to a system according to the invention, [ Fig 3 ] there figure 3 shows another example of a machine, particularly suited to large tires, [ Fig 4 ] There figure 4 shows more precisely the position of the different cameras used to film the tire, [ Fig 5 ] There figure 5 shows the different areas of the tire that need to be illuminated and acquired, [ Fig 6 ] There figure 6 shows a chronogram of the major steps of a process according to the invention.

[0037] There figure 1 Figure 1 shows a surface 1 to be studied. This surface 1 is illuminated by different light sources 2a, 2b, 2c, and 2d. It should be noted that the different light sources are not intended to be switched on simultaneously, but rather alternately, according to a predefined lighting cycle. Indeed, as previously stated, the principle of stereophotometry is to take multiple images, also called photographs, of surface 1 under different lighting conditions, depending on the light source(s) switched on during the image capture. To this end, the system of the figure 1 also includes a 3D shooting system.

[0038] There figure 2 This shows a complete view of a machine implemented in a system according to the invention. This machine includes means for rotating a tire 10. This machine also includes means for linear movement of the tire from the inlet zone 21 (not visible in the figure) to the outlet zone 22. These means include, for example, a discharge conveyor 23.

[0039] The machine also includes centering devices in the form of 20 vertical rollers that clamp the tire and then drive it. The movement of the two pairs is synchronized by a belt. As the tire enters the machine, its diameter is approximately measured by the infeed rangefinder, and the rollers are sent to this clamping position plus an offset to achieve a tighter fit. As this dimension is approached, the rollers slow down to switch to a set torque, providing flexibility in both centering and drive.

[0040] There figure 3 shows another example of a machine, designed to accommodate a pneumatic device for an acquisition phase.

[0041] This figure 3 allows us to illustrate another example of the realization of the means of setting the tire in motion, and also to describe means of spacing the beads for a large tire.

[0042] The various lighting and acquisition methods are not shown in this figure and will not be described. However, the description of these methods, carried out in view of the figure 2 , also applies to a machine such as the one shown in figure 3 .

[0043] In this example, the means for rotating a tire include vertical rollers 36, only one of which is shown in the figure, which drive the tire. This rotation is facilitated by the presence of horizontal rollers 31, located under the tire when it is in position.

[0044] This example also shows four discharge conveyors 30. Unlike the previous figure, which showed only one conveyor, here we have four separate conveyors. Indeed, in order to use the machine for large tires, it is useful to provide means 32 for spacing the beads, which must be inserted into the center of the tire.

[0045] It is therefore necessary to clear the central space, which requires positioning the discharge conveyors on the sides. Several conveyors should be used to ensure that discharge is parallel to the machine's exit direction. Furthermore, having two conveyors on each side, with a gap between them, allows for the removal of entire sections of the tire, thus enabling the collection of the lower portion.

[0046] A detailed view of these means 32 is shown in the bubble on the figure 3 These means include rollers 33 that move in translation on two vertical axes 34. These vertical axes are, in turn, movable in translation on a horizontal axis.

[0047] When the pneumatics are not in the machine, the vertical axes are in the center and the pins are in the lower position, as shown in the figure. When the pneumatics are in position, the gap between the beads is measured. If the measurement is less than a predetermined value, the rollers move up to the lowest point of the upper bead (the bead furthest from the table), and the vertical axes move apart to apply pressure to the bead, thus widening it to the desired opening. If the measurement is greater than this same predetermined value, the rollers move up to the lowest point of the upper bead, and slight pressure is applied simply to ensure the beads remain flat during rotation.

[0048] The acquisition step is then carried out, and the spacing means then return to their initial position, to allow the evaluation of the tire.

[0049] We will now describe using the figures 4 And 5 the different areas of the tire and the cameras that can be used to perform the different acquisitions.

[0050] A tire can be separated into different zones: external areas, such as the sidewalls 60, shoulders 61, and tread 62, also called the top, internal areas such as the inner sides 63 and inner crown 64.

[0051] To acquire these different areas, both two-dimensional and three-dimensional cameras, also called sensors, are used, which are shown in figure 4 .

[0052] Two-dimensional sensors are used both indoors and outdoors: 2D_EXT_T sensor for acquiring tread 62, 2D_EXT_S sensor for acquiring shoulders 61, 2D_EXT_B sensors for acquiring sidewalls 60.

[0053] The sensor enabling the acquisition of the inner ring is not visible on the figure 4 .

[0054] The sensors enabling the acquisition of internal sides are not referenced.

[0055] Three-dimensional sensors are used only for the external surfaces of the tire, and are marked 3D on the figure 4 Some cameras are advantageously equipped with lighting systems. These lighting systems take the form of L-shaped light bars, each bar being composed of a line of individual light sources, and being oriented so that the lighting is as uniform as possible on the line acquired by a line camera.

[0056] In one example, a camera carries three or four light bars, which light up in turn according to a predetermined cycle. Thus, the camera can create three or four different images at once, which allows the application of a stereophotometry principle, already described.

[0057] In one example, the 2D-EXT-Ba and 2D-EXT-Sa cameras located below the tire are in a fixed position, and the tire automatically adjusts itself to the correct position relative to these cameras. Conversely, the 2D-EXT-Bb and 2D-EXT-Sb cameras located above the tire are mounted on a movable axis, allowing them to descend to a suitable acquisition position depending on the tire's width.

[0058] Furthermore, in one embodiment, the positioning of the internal cameras, enabling the acquisition of the inner sides and the inner rim, can be performed automatically when a tire enters the capture zone. To this end, a system according to the invention includes a rangefinder for determining the position of a significant point on the tire, for example, the innermost radial point of the tire, namely the end of the bead intended to be in contact with a rim seat during tire mounting.

[0059] Determining this point allows for the positioning of the various interior cameras in height and radius. In one example, the camera intended for acquiring the inner rim is positioned at mid-height relative to this significant point, starting from the zero ordinate corresponding to the table on which the tire is positioned in the capture zone.

[0060] We will now describe, using the chronogram of the figure 6 , the different stages of a process according to the invention, enabling the objectives of the invention to be achieved, namely the realization of a complete visual inspection in the shortest possible cycle time.

[0061] The first step E1 consists of the entry of a tire into a system according to the invention. As shown in the timing diagram, this step E1 can be simultaneous with a step E0 corresponding to the exit, or evacuation, of the previous tire.

[0062] Following this step E1, a step E2 consists of blocking the tire in a centered manner.

[0063] The E3 stage of rotating the tire starts at the same time as the centering stage, and will last until the end of the acquisition cycle.

[0064] We then arrive at macro-step E4, which involves positioning the various sensors. This macro-step comprises several sub-steps for each sensor. We will describe here the successive sub-steps corresponding to one sensor: a sub-step E41 of descent of the sensor at high speed, a sub-step E42 of descent of the sensor at low speed.

[0065] These two sub-steps allow us to achieve the compromise inherent in the present invention, namely the speed / quality compromise. Thus, we begin by rapidly lowering the sensor to near the area where it is to be located, then we switch to a slow speed to precisely adjust the position.

[0066] A sub-step E43 of adjusting the diameter of the sensor, that is to say no longer a vertical movement as in sub-steps E41 and E42, but an axial movement to adapt to the diameter of the tire to be evaluated.

[0067] These three sub-steps are the same for all indoor sensors.

[0068] On the other hand, external sensors, which are easier to position, can be lowered at a constant speed.

[0069] Furthermore, as previously mentioned, some sensors do not move, since they are in a fixed position in the evaluation system.

[0070] We then move on to the E5 acquisition stage itself, also called control.

[0071] Next, there is step E6, which corresponds to the reassembly of the various sensors. In parallel with this step E6 is step E7, which releases the centering devices.

[0072] The tire exit step is not described at the end of the chronogram because it was described at the beginning, under reference E0.

Claims

1. System for evaluating the surface of a tyre (10), comprising: - a region (21) for entry of the tyre into the system, a capture region, and an exit region (22), distinct from the entry point, - means for moving (23) and for holding a tyre in position, - means for illuminating the tyre allowing the illumination of a sidewall of the tyre and of the crown of a tyre in the capture region, - means for acquiring a visual image of the tyre in the capture region, - means for processing the acquired image, at least one acquisition means being installed on a shaft that is movable with respect to the tyre installed in the capture region, and - means for spreading the beads of the tyre, characterized in that said means for spreading the beads of the tyre comprise rollers that are movable in translation on two vertical shafts, the two vertical shafts are movable in translation on a horizontal shaft.

2. Evaluation system according to Claim 1, wherein the means for moving (23) and holding a tyre in position comprise one or more means from among: - means for centring the tyre (20), - rotating means, - means for locking the tyre, - means for linear movement between the entry and exit regions, via the capture region.

3. Evaluation system according to one of the preceding claims, wherein the acquisition means comprise one or more linear cameras, and wherein the illuminating means are arranged outside of the field of acquisition of the one or more cameras.

4. Evaluation system according to one of the preceding claims, wherein the illuminating means comprise individual light sources covered with a diffusing material.

5. Evaluation system according to one of the preceding claims, wherein the means for illuminating a sidewall of the tyre comprise several lines of individual light sources.

6. System according to one of the preceding claims, wherein the means for processing the acquired image comprise artificial intelligence means.

7. System according to one of the preceding claims, comprising means for positioning the acquisition and / or illuminating means.

8. System according to one of the preceding claims, comprising a half-mirror, installed so as to reflect the image of part of the tyre.

9. Method for evaluating the surface of a tyre using a system according to one of the preceding claims, the method comprising - a step of entering the tyre into the evaluation system, - a step of acquiring a visual image of the tyre, - a step of exiting the tyre from the evaluation system, in which the step of acquiring a visual image of the tyre is performed while the tyre is rotated by one revolution, and in that the step of exiting the tyre is concomitant with a step of entering another tyre into the system.