Optical measurement system, motor vehicle body assembly, use of said optical measurement system and method for monitoring the evolution of a deformation gradient of a roof

Abstract

Optical measurement system, motor vehicle body assembly, use of said optical measurement system, and method for monitoring the evolution of a deformation gradient of a roof. The invention relates to an optical measurement system (1) adapted for fixing in a motor vehicle body structure. According to the invention, said system comprises: - a thermal housing (3), - a stereovision system (15) acquiring pairs of digital images of a roof, - a mounting bracket (25) for said stereovision system to said thermal housing, - a light source (23) illuminating said roof, - a means for powering said stereovision system, - a software means for controlling a phase of acquisition of synchronous digital image pairs. The invention also relates to a body assembly, a use of said measurement system, and a method for monitoring the evolution of a deformation gradient of a roof. Figure 1

Description

Title of the invention: Optical measurement system, motor vehicle body assembly, use of said optical measurement system and method for monitoring the evolution of a deformation gradient of a roof. Technical field

[0001] The invention relates to the field of motor vehicles and more particularly to an optical measurement system adapted for mounting in a body structure of a motor vehicle body assembly, and to a motor vehicle body assembly comprising such an optical measurement system. The invention also relates to a use of said optical measurement system and to a method for monitoring the evolution of a deformation gradient of a roof section of said body assembly. Previous technique

[0002] A motor vehicle body structure comprises a set of elements made of steel and forming the framework of the motor vehicle.

[0003] The roof, generally made of aluminum, is assembled to the body structure of the motor vehicle in order to cover the passenger compartment of the motor vehicle.

[0004] After assembly of the roof and body structure of the motor vehicle, the body assembly thus formed is immersed in a bath in order to apply an anti-corrosion coating by a cataphoresis process.

[0005] After application of the anti-corrosion coating on the body assembly, the body assembly undergoes a curing phase during which the coating covering the body assembly will polymerize in a curing tunnel.

[0006] To do this, the curing tunnel is brought to a temperature between approximately 180°C and approximately 220°C and the entire case is placed in the curing tunnel for approximately 1 hour 30 minutes.

[0007] In the context of controlling welded assemblies, it is necessary to ensure that the pavilion and the body structure remain properly welded despite the passage of the body assembly through the curing tunnel under the aforementioned temperature and duration conditions.

[0008] To do this, when the car body assembly is removed from the curing tunnel after thermal loading, a method for measuring the shape deviations between the car body assembly and a theoretical numerical model of the car body assembly is applied to the car body assembly.

[0009] This process is, for example, implemented using a geometry control system, such as a multi-articulated arm equipped with a laser sheet sensor, or a three-dimensional measuring machine, used to quantify the shape deviations present on the roof of the body assembly related to the differential expansion of aluminum compared to steel.

[0010] Given that this measurement method is implemented after the body assembly has left the curing tunnel, it does not allow monitoring of the evolution of the geometry of the pavilion during the curing phase of the body assembly in the curing tunnel.

[0011] Also, given the high temperature prevailing in the curing tunnel and the duration of the curing phase, implementing the measurement method inside the curing tunnel using a geometry control system during the curing phase is not feasible, as the geometry control system is not designed to operate in environments where the temperature exceeds the maximum operating temperature of the electronic devices used, for example, 50°C. Description of the invention

[0012] The present invention aims to overcome the aforementioned drawbacks, and to this end relates to an optical measurement system adapted to be fixed in a body structure of a motor vehicle body assembly, remarkable in that it comprises: - a thermal enclosure, comprising an external casing designed to maintain an internal temperature between approximately 40°C and approximately 55°C for at least 1 hour 30 minutes when said optical measurement system is placed in an oven tunnel where the temperature is between approximately 180°C and approximately 220°C, - a stereovision system designed to acquire pairs of digital images of a pavilion of said enclosure assembly when said optical measurement system is fixed in said enclosure structure of said enclosure assembly, - a mounting bracket for said stereovision system for said thermal enclosure, - a suitable light source to illuminate said canopy of said enclosure assembly when said optical measurement system is fixed in said enclosure structure of said enclosure assembly, - a power supply providing energy to said stereovision system, - a software means suitable for controlling a phase of acquisition of pairs of synchronous digital images.

[0013] Thus, the optical measurement system according to the invention makes it possible to operate in a curing tunnel heated to a temperature between approximately 180°C and approximately 220°C, for a period of between approximately 1h30 and approximately 2h, and this without lighting associated with the drying tunnel.

[0014] In this way, it is possible to follow the evolution of a deformation gradient of the roof of the motor vehicle body assembly throughout the curing phase of the body assembly, unlike the prior art where such an evolution can only be followed after the body assembly has come out of the curing tunnel.

[0015] According to optional features of the optical measurement system according to the invention: - said external casing of said thermal box is made of microporous material insulation; - said thermal box includes a lid with a porthole having an external wall of glass treated against thermal shock; - said stereovision system comprises two cameras and said optical measurement system comprises two articulated platforms relative to said mounting support, each supporting one of said cameras of said stereovision system; - said light source is a cold light source.

[0016] The invention also relates to a motor vehicle body assembly comprising a body structure and a roof assembled to said body structure, notable in that it comprises at least one optical measurement system according to the invention.

[0017] In one embodiment, the case assembly includes a mounting support fixed to said case structure and a complementary mounting interface adapted to clamp said at least one optical measuring system relative to said case structure.

[0018] The invention also relates to the use of an optical measurement system according to the invention to acquire a pair of digital images of a roof of a motor vehicle body assembly, said body assembly being placed in a curing tunnel for a predetermined period, for example for at least 1h30, and at a predetermined temperature, for example between about 180°C and about 220°C.

[0019] The invention also relates to a method for monitoring the evolution of a deformation gradient of a roof section of a motor vehicle body assembly, said body assembly being placed in a curing tunnel for a predetermined period, for example for at least 1 hour 30 minutes, and at a predetermined temperature, for example between approximately 180°C and approximately 220°C, said monitoring method being notable in that it comprises an acquisition phase image processing implemented by a software means of an optical measurement system according to the invention.

[0020] In an embodiment of the tracking method according to the invention, said method comprises: - a processing phase aimed at characterizing, on the basis of the images acquired during said image acquisition phase, the deformation fields of said pavilion and at quantifying the evolution of said deformation fields, - a comparison phase aimed at comparing said quantified deformation fields to theoretical deformation fields from a numerical simulation model. Brief description of the drawings

[0021] Other features, purposes and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference should be made to the accompanying drawings in which:

[0022] [Fig-1] shows an optical measurement system according to the invention.

[0023] [Fig.2] shows the integration of optical measurement systems into a structure of body of a motor vehicle.

[0024] [Fig.3] is a side view of a motor vehicle body assembly according to the invention. Description of the implementation methods

[0025] In the following description, elements having an identical structure or analogous functions are designated by the same reference.

[0026] Reference is made to [Fig.1] showing an optical measuring system 1 according to the invention.

[0027] The optical measurement system 1 comprises a thermal chamber 3, shown in the [Fig.1] in longitudinal section.

[0028] The thermal housing 3 comprises an external, thermally sealed casing 5, and may comprise an internal casing 7, for example metallic.

[0029] The thermal enclosure 3 comprises, at the level of its external casing 5, a set of side walls 9 and a lid 11 comprising a porthole 13 comprising an external wall of glass, for example triple glazing, treated against thermal shock.

[0030] The design of the external housing 5 is such that it allows an internal temperature inside the thermal housing 3 to be maintained between approximately 40°C and approximately 50°C, for example approximately 45°C, for at least 1h30 when the optical measuring system 1 is placed in an oven tunnel where the temperature is between approximately 180°C and approximately 220°C, for example approximately 210°C.

[0031] For this purpose, the external casing 5 may be made of microporous insulation. The fact that the external casing 5 is made of microporous insulation allows for the best possible delay in thermal equilibrium between the internal temperature and external temperature of thermal chamber 3, for a period of approximately 2 hours.

[0032] The optical measurement system 1 includes a miniaturized stereovision system 15 enabling the acquisition of stereoscopic image pairs, essential for the implementation of stereocorrelation algorithms in order to quantify the three-dimensional displacement fields, and then to characterize the deformation fields, present on the surface of the element to be measured.

[0033] The miniaturized stereovision system 15 comprises a set of cameras 17.

[0034] In the example embodiment of the optical measurement system 1 shown in the figures, two cameras 17 are fitted to the miniaturized stereovision system 15. However, the miniaturized stereovision system 15 may include more cameras 17.

[0035] The cameras used are, for example, high-quality 12.3-megapixel cameras.

[0036] The cameras are equipped with lenses 19 allowing the acquisition of pairs of synchronous images representative of a geometric state at a predetermined instant of a pavilion of a set of boxes, as will be seen in the rest of the description.

[0037] For this purpose, a lens that can be used is, for example, a wide-angle lens with a focal length of 24mm and an aperture of f / 1.4.

[0038] The miniaturized stereovision system 15 further comprises a micro-acquisition system consisting of a stereoscopic image acquisition card, a processor and a memory card.

[0039] The stereovision system 15 is further powered via a power supply such as a battery 21, the geometric characteristics of which are reduced to just what is necessary so as not to penalize the final volume of the optical measurement system 1.

[0040] The battery 21 is chosen so as to guarantee the autonomy of the optical measuring system 1 for a period of at least two hours.

[0041] Furthermore, the curing tunnel, in which the entire case assembly is placed after passing through a cataphoresis bath, is devoid of lighting.

[0042] In order to illuminate the pavilion of the body assembly at the desired time when the body assembly is in the curing tunnel, the optical measuring system 1 includes a light source 23.

[0043] In one embodiment, the light source 23 is a cold light source, which advantageously makes it possible to significantly reduce thermal radiation in the thermal box 3.

[0044] Furthermore, the optical measurement system 1 includes a mounting bracket 25 for the stereovision system 15 to the thermal housing 3.

[0045] The mounting bracket 25 is adapted to allow rigid attachment of the stereovision system 15 to the thermal housing 3 when the settings are fixed.

[0046] For this purpose, the mounting support 25 includes a mounting plate 27 fixed to the internal housing 7 of the thermal enclosure 3 by means of fixing elements 28.

[0047] In the embodiment illustrated in the figures, the mounting plate 27 of the mounting bracket 25 has an "L" shape. According to an alternative embodiment not illustrated in the figures, the mounting plate 27 of the mounting bracket 25 has a different geometric shape.

[0048] Thus, the physical retention of the elements of the stereovision system 15 in the thermal chamber 3 meets the requirements of image correlation, from one end to the other of the curing tunnel.

[0049] In the embodiment illustrated in the figures, the optical measurement system 1 comprises two platforms 29 articulated relative to the mounting support 25, each supporting one of the cameras 17 of the stereovision system 15.

[0050] The optical measuring system 1 further includes a means for locking the articulated platforms 29 in position.

[0051] The articulation of the platforms 29 supporting the cameras 17 allows for precise adjustment of the angle between the optical axis of each camera 17 and the normal to the observation point, so that the cameras 17 observe precisely the same scene. This ensures an optimal measurement volume and provides the stereovision system 15, after locking the position of the platforms 29, with a fixed triangulation basis.

[0052] Reference is made to [Fig.2] showing the integration of the optical measurement system 1 into a body structure 31 of a motor vehicle 33.

[0053] The optical measurement system 1 is intended to be carried on board the body structure 31 in order to measure the evolution of the thermal expansions of the pavilion (not yet assembled to the body structure 31 in the representation given in [Fig.2]) from one end to the other of the curing tunnel.

[0054] The fixing of the optical measuring system 1 in the case structure 31 is carried out by means of a fixing support 35 and a complementary fixing interface 37.

[0055] The mounting bracket 35 is fixed inside the case structure 31 for example by screwing.

[0056] The mounting interface 37 is adapted to clamp the optical measuring system 1 relative to the case structure 31.

[0057] Fixing the optical measurement system 1 on board the body structure 31 helps to preserve the quality of the measurements with regard to possible parasitic movements between the thermal box 3 and the body structure 31.

[0058] The integration of several optical systems 1 into the body structure 31 is necessary in order to acquire the entire pavilion. As shown in [Fig. 2], two optical measurement systems 1 are integrated on board the body structure 31.

[0059] However, more optical measurement systems 1 can nevertheless be integrated on board the body structure 31.

[0060] The optical measurement system 1 further includes a software means comprising a computer code means adapted to control a phase of digital image acquisition.

[0061] Reference is made to [Fig.3] showing the motor vehicle 33 in which three optical measuring systems 1 are integrated into the body structure 31.

[0062] The motor vehicle 33 comprises the body structure 31, for example made of steel, and a roof 39, for example made of aluminum.

[0063] The pavilion 39 is pre-assembled to the body structure 31 in order to cover the passenger compartment of the 41 of the motor vehicle 33.

[0064] The assembly of the pavilion 39 onto the body structure 31 is for example carried out by welding or by brazing.

[0065] After assembly of the pavilion 39 and the body structure 31, the body assembly 43 thus formed is immersed in a bath in order to apply an anti-corrosion coating, for example by a cataphoresis process.

[0066] After application of the anti-corrosion coating on the body assembly 43, the body assembly 43 undergoes a curing phase during which the anti-corrosion coating deposited on the body assembly 43 is polymerized in a curing tunnel (not shown).

[0067] In one particular embodiment, the curing tunnel is approximately 200 meters long and is not lit. The curing tunnel is heated to a temperature between approximately 180°C and approximately 220°C, for example 210°C, and the crate assembly 43 is placed in the curing tunnel for a period of between approximately 1.5 hours and approximately 2 hours.

[0068] The optical measuring system 1 is integrated and rigidly fixed in the case structure 31 of the case assembly 43, via the mounting bracket 35 and the complementary mounting interface 37.

[0069] Before integrating the optical measurement system 1 into the box structure 31 of the box assembly 43, a first calibration of the optical measurement system 1 can be done at this stage, i.e. before the entry of the box assembly 43 into the curing tunnel, before starting the image acquisition phase.

[0070] The box assembly 43 is then fixed onto a cradle (not shown), conventionally comprising a support for the box assembly 43 connected to a conveyor allowing the box assembly 43 to be moved along the curing tunnel.

[0071] The conveyor is, for example, configured to move the swing at a constant speed along the curing tunnel.

[0072] The swing presents the entire crate assembly 43 at the entrance to the curing tunnel.

[0073] Therefore, the method for monitoring the evolution of a deformation gradient present on Pavilion 39 of the entire crate assembly 43 is initiated.

[0074] The tracking method includes a first image acquisition phase, implemented by the software means of the optical measurement system 1 in order to trigger a succession of image acquisition steps.

[0075] The image acquisition phase aims to acquire pairs of images of the pavilion 39 at regular intervals, from the entry of the crate assembly 43 into the curing tunnel until the exit of the curing tunnel.

[0076] For example, the time interval for image acquisition can be approximately 5 seconds.

[0077] Each step in acquiring image pairs consists of illuminating the pavilion 39 for a period of between approximately 1 second and approximately 3 seconds, for example approximately 2 seconds, in order to avoid a temperature rise inside the thermal box 3 of the optical measurement system 1, and to acquire during this time an image of the pavilion 39 simultaneously with the cameras 17 of the optical measurement system 1.

[0078] The lighting is obtained by triggering the light source 23 of the optical measuring system 1.

[0079] When the image acquisition phase is complete, i.e. when the entire crate assembly 43 comes out of the curing tunnel, a second calibration can be done to ensure the relevance of the measurements taken.

[0080] When the image acquisition phase is completed, i.e. when the box assembly 43 comes out of the curing tunnel, the method of monitoring the evolution of the deformation gradient present on the pavilion 39 of the box assembly 43 includes a second phase of processing the acquired image data.

[0081] This processing phase consists of transferring the acquired images to a computer, characterizing the displacement fields of the pavilion 39 of the body assembly 43 using dedicated software, and then quantifying the evolution of the deformation fields throughout the curing phase.

[0082] The method for monitoring the evolution of the deformation gradient includes a third phase aimed at comparing the previously quantified deformation fields with theoretical deformation fields from a numerical simulation model.

[0083] On this basis, the numerical simulation model can be optimized so that it can predict appearance defects.

[0084] Also, local reinforcement solutions, for example the addition of ribs, can be proposed.

[0085] Thus, thanks to the present invention, it is possible to quantify and follow the evolution of the geometric variations, linked to the phenomena of differential expansion, which the pavilion 39 of the body assembly 43 undergoes during the curing phase.

[0086] The optical measurement system 1 according to the invention very advantageously allows operation in a curing tunnel brought to a temperature between approximately 180°C and approximately 220°C, for a period of between approximately 1h30 and approximately 2h, and this without lighting associated with the curing tunnel.

[0087] As will be understood, the present invention is not limited to the embodiments of this optical measurement system, this motor vehicle body assembly, the use of this optical measurement system and this method of monitoring the evolution of a deformation gradient of a roof, described above solely as illustrative examples, but on the contrary it encompasses all variants involving the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

Claims

Demands

1. A motor vehicle (33) body assembly (43) comprising a body structure (31) and a roof (39) assembled to said body structure (31), comprising at least one optical measurement system (1) adapted to be fixed in the body structure (31) of said motor vehicle (33) body assembly (43), characterized in that it comprises: - a thermal enclosure (3), comprising an external housing (5) designed to maintain an internal temperature of between approximately 40°C and approximately 55°C for at least 1h30 when said optical measurement system (1) is placed in a drying tunnel where the temperature is between approximately 180°C and approximately 220°C, - a stereovision system (15) designed to acquire pairs of digital images of a roof (39) of said body assembly (43) when said optical measurement system (1) is fixed in said body structure (31) of said body assembly (43),- a mounting bracket (25) for said stereovision system (15) on said thermal enclosure (3), - a light source (23) suitable for illuminating said pavilion (39) of said enclosure assembly (43) when said optical measurement system (1) is fixed in said enclosure structure (31) of said enclosure assembly (43), - a power supply means providing energy to said stereovision system (15), - a software means suitable for controlling a phase of acquisition of synchronous digital image pairs.

2. Motor vehicle (33) body assembly (43) according to claim 1, characterized in that said external casing (5) of said thermal box (3) is made of microporous material insulation.

3. Motor vehicle (33) body assembly (43) according to any one of claims 1 or 2, characterized in that said thermal box (3) comprises a lid (11) comprising a window (13) comprising an external wall of glass treated against thermal shock.

4. Motor vehicle (33) body assembly (43) according to any one of claims 1 to 3, wherein said system of stereovision (15) comprises two cameras (17), characterized in that the optical measurement system (1) comprises two platforms (29) articulated relative to said mounting support (25) each supporting one of said cameras (17) of said stereovision system (15).

5. Motor vehicle (33) body assembly (43) according to claim 4, characterized in that the optical measuring system (1) comprises a mounting support (35) fixed to said body structure (31) and a complementary mounting interface (37) adapted to clamp said at least one optical measuring system (1) relative to said body structure (31).

6. Use of an optical measurement system (1) of a motor vehicle (33) body assembly (43) according to any one of claims 1 to 5 to acquire a pair of digital images of a roof (39) of the motor vehicle (33) body assembly (43), said body assembly (43) being placed in a curing tunnel for a predetermined period, for example for at least 1h30, and at a predetermined temperature, for example between about 180°C and about 220°C.

7. A method for monitoring the evolution of a deformation gradient of a roof (39) of a body assembly (43) of a motor vehicle (33), said body assembly (43) being placed in a curing tunnel for a predetermined period, for example for at least 1 hour 30 minutes, and at a predetermined temperature, for example between approximately 180°C and approximately 220°C, said monitoring method being characterized in that it comprises an image acquisition phase implemented by software means of an optical measurement system (1) of a body assembly (43) of a motor vehicle (33) according to any one of claims 1 Q

8. 1 d J. A monitoring method according to claim 7, characterized in that it comprises: - a processing phase aimed at characterizing, on the basis of the images acquired during said image acquisition phase, the deformation fields of said pavilion (39) and at quantifying the evolution of said deformation fields, - a comparison phase aimed at comparing said quantified deformation fields to theoretical deformation fields from a numerical simulation model.

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