Low-stress assembling and bonding device and method for outer-steel inner-carbon mixed material B column assembly

Abstract

The invention relates to the machining and manufacturing technology of automobile parts, in particular to a low-stress assembling and bonding device and method for an outer-steel inner-carbon mixed material B column assembly. According to the method, a refined gluing regulation and control mechanism matched with the complex structure of the B column with the steel outside and the carbon inside is constructed, the glue amount requirements of different areas are met by dynamically adjusting the flow, the thermal expansion difference of materials is buffered through the reasonable glue layer thickness, the glue coating shape is planned according to a preset track, and the curved surface characteristics are attached; overlapping spraying is adopted to improve the area coverage rate of a key area, and constant-temperature heating is combined to improve the fluidity of glue. The method can be extended to vehicle body components such as columns A and doorsill beams, an innovative technical path is provided for efficient and reliable manufacturing of multi-material vehicle bodies, and the application scene is expanded. By means of the device, automatic low-stress assembling and bonding of the B column assembly made of the'outer steel and inner carbon 'mixed materials are achieved, and the stress concentration phenomenon caused by uneven temperature and unbalanced pressure field is reduced.

Description

Technical Field

[0001] The present invention relates to a processing and manufacturing technology for automobile parts, in particular to a low-stress assembly and bonding device and method for a B-pillar assembly made of a "steel outside and carbon inside" mixed material. Background Art

[0002] Driven by the need for energy conservation and emission reduction, lightweighting and safety design have become prominent trends in the automotive industry. Currently, multi-material hybrid designs for vehicle body structures have become the optimal compromise between lightweighting, safety, and cost. Carbon fiber composites, due to their outstanding properties such as high specific strength and excellent corrosion resistance, have seen their application in key load-bearing components in recent years. However, their high price has limited their widespread adoption. While high-strength steel offers excellent strength and impact resistance, its high density makes it difficult to meet vehicle lightweighting goals. For example, the B-pillar in a vehicle presents a significant conflict between side impact safety and lightweighting. Consequently, a B-pillar assembly combining a high-strength steel outer panel and a carbon fiber composite inner panel has been designed. This "steel outer, carbon inner" hybrid B-pillar structure has become the mainstream solution. High-strength steel is used for the outer panel to ensure collision energy absorption and reduce costs, while carbon fiber composite is used for the inner panel to significantly reduce weight and preserve passenger space.

[0003] However, just like multi-material vehicle bodies, the reliable joining of dissimilar materials, such as metal-carbon fiber composites, currently presents significant technical challenges. On the one hand, the two types of materials exhibit significant differences in physical properties such as thermal expansion coefficient, elastic modulus, and surface energy. Temperature cycles during the manufacturing process and service loads can easily lead to interfacial stress concentration, which can trigger failure modes such as crack initiation and interlaminar delamination. On the other hand, traditional mechanical joining methods (such as punching, riveting, and bolting) can disrupt the fiber continuity of the composite material, creating stress concentration sources that significantly reduce load-bearing capacity and fatigue life. Therefore, bonding, as a joining technology that can avoid damage to the composite material itself, has become a core solution for replacing some mechanical joining methods in the processing and manufacturing of hybrid material B-pillars.

[0004] Existing bonding technologies face numerous bottlenecks in the assembly and bonding of hybrid B-pillars: (a) insufficient residual stress control during assembly, with uneven temperature and pressure distribution during the curing phase easily leading to excessive residual stress at the interface; (b) insufficient positioning precision control, with the complex curved surface structure of the B-pillar easily causing adhesive thickness fluctuations, affecting joint consistency and internal stress; and (c) a low degree of process systematization, lacking integrated solutions for dynamic glue spray volume adjustment, glue fluidity matching, and multi-operating stress adaptation, making it difficult to meet the stringent efficiency, reliability, and stability requirements of large-scale production. These issues can lead to a reduction in the crash safety performance and durability of high-safety structural components such as the B-pillar, directly threatening driving safety.

[0005] Chinese published invention patents CN202211490849.2 and CN202211449318.9 mention low-stress bonding methods. Both patents employ steps such as designing the adhesive layer thickness, verifying the assembly gap, applying the adhesive, and curing it to release the metal expansion stress into the adhesive layer to prevent cracking of fragile materials. Chinese published invention patent CN202211490849.2, applied to a quartz ceramic radome, uses removable rigid limiters to control a uniform adhesive layer, suitable for simple structures and high machining precision. Chinese published invention patent CN202211449318.9, applied to a zinc sulfide window, uses non-removable flexible limiters to control a gradient adhesive layer, suitable for complex structures, poor machining precision, and gradient gaps. Both patents use limiters to control the adhesive layer thickness to achieve low-stress bonding, making the bonding process cumbersome and labor-intensive. Summary of the Invention

[0006] In response to the problems pointed out in the background technology, the purpose of the present invention is to propose a low-stress assembly and bonding device and method for a "steel outside and carbon inside" hybrid material B-pillar assembly. By integrating key technologies such as high-precision panel positioning, automated glue coating control, and multi-process parameter collaborative curing, high-strength, low-stress assembly and bonding of the interface between metal and carbon fiber composite materials can be achieved, providing a new technical path for the efficient and reliable processing and manufacturing of multi-material body structures.

[0007] To achieve the above object, the present invention adopts the following technical solutions: The present invention first provides a low-stress assembly method for a "steel outer, carbon inner" hybrid material B-pillar assembly, comprising the following steps: Step S1, establishing a thermodynamic model of the automobile B-pillar assembly and calculating the effective thickness of the adhesive layer in different regions based on the structural properties and thermal expansion coefficients of the B-pillar's high-strength steel outer panel, carbon fiber inner panel, and adhesive; Step S2: importing a three-dimensional structural model of the B-pillar assembly into the control platform of the low-stress assembly and bonding device; the low-stress assembly and bonding device further comprises an upper adsorption platform, a lower adsorption platform, and a robotic arm system; the end of the robotic arm body of the robotic arm system is equipped with a vacuum clamp and a glue spraying mechanism; the lower surface of the upper adsorption platform is uniformly provided with liftable adsorption heads A, and the upper surface of the lower adsorption platform is uniformly provided with liftable adsorption heads B; based on the three-dimensional structural model of the B-pillar assembly, the control platform sets the placement area and posture of the outer panel on the lower adsorption platform, the placement area and posture of the inner panel on the upper adsorption platform, the starting position and motion trajectory of the robotic arm system for gripping the outer panel, the starting position and motion trajectory of the robotic arm system for gripping the inner panel, and the glue spraying trajectory of the robotic arm system; Step S3, pre-treating the outer plate and the inner plate separately; Step S4: The robotic arm system grasps the outer panel using the vacuum gripper at the end of the robotic arm body and places the outer panel in the preset placement area of ​​the lower adsorption platform. Multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform adsorb and secure the outer panel so that the outer panel conforms to the preset posture. Step S5: The robotic arm system runs a glue spraying track, and glue is sprayed on the outer panel through the glue spraying mechanism carried by the end of the robotic arm body; the glue is heated to 40-50°C through a constant temperature pipe before entering the nozzle, which is conducive to achieving low-stress assembly; Step S6: After the glue is sprayed on the outer panel, the robotic arm system uses the vacuum clamp mounted on the end of the robotic arm body to grasp the inner panel and place the inner panel in the preset placement area of ​​the upper adsorption platform. The multiple adsorption heads A in the preset placement area of ​​the lower adsorption platform adsorb and fix the inner panel so that the inner panel conforms to the preset posture. Step S7, bonding; the control platform controls the upper adsorption platform to move downward so that the inner plate reaches a predetermined position above the outer plate, completing the bonding; Step S8: placing the bonded B-pillar assembly in a constant temperature box for curing; Step S9: After curing, remove burrs and flash on the B-pillar assembly.

[0008] The step S3 is specifically as follows: sandblasting the contact surfaces of the outer plate and the inner plate to clean and remove impurities.

[0009] In step S4, after the outer panel is placed in the preset placement area of ​​the lower adsorption platform and the multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform adsorb and fix the outer panel, an infrared camera is used to monitor the position and posture of the outer panel. The infrared camera captures the relative position relationship between the four corner endpoints of the inner panel and the four corner endpoints of the set placement area, and generates posture data by continuously scanning the characteristic contour of the outer panel, and feeds back the position offset and angular error of the outer panel in three-dimensional space to the control platform in real time; if there is a position offset or angular error of the outer panel, the control platform controls the multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform according to the deviation signal to start fine-tuning action, so that the posture of the outer panel conforms to the set posture.

[0010] In step S5, AB structural adhesive for aviation is used, and the ratio of component A to component B of the AB structural adhesive is 3:7. The glue is stirred evenly before heating and bubbles are removed. When spraying the glue, the target glue layer thickness is controlled at 0.2-1.0 mm, and the glue coverage rate meets 95%.

[0011] In step S6, when the inner panel is placed in the preset placement area of ​​the upper adsorption platform, after the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform adsorb and fix the inner panel, an infrared camera is used to monitor the position and posture of the inner panel. The infrared camera captures the relative position relationship between the four corner endpoints of the inner panel and the four corner endpoints of the set placement area, and generates posture data by continuously scanning the characteristic contour of the inner panel, and feeds back the position offset and angular error of the inner panel in three-dimensional space to the control platform in real time; if there is a position offset or angular error of the inner panel, the control platform controls the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform according to the deviation signal to start fine-tuning action, so that the posture of the outer panel conforms to the set posture.

[0012] In step S7, when the control platform controls the upper adsorption platform to move downward so that the inner panel reaches the predetermined position above the outer panel, an infrared camera is used to monitor the distance between the lower surface of the inner panel and the upper surface of the outer panel in real time, and the monitoring information is transmitted to the control platform. The control platform controls the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform to move downward synchronously based on the monitoring information and the preset adhesive layer thickness, so that the distance between the lower surface of the inner panel and the upper surface of the outer panel meets the preset adhesive layer thickness, thereby completing the bonding.

[0013] The step S8 is specifically as follows: S8.1. Place the bonded B-pillar assembly in a constant temperature oven and heat it from room temperature (20±5°C) to 40-60°C at a rate of 5°C / min. Perform initial curing within the 40-60°C temperature range to form a preliminary positioning adhesive layer. The ambient humidity for initial curing is 40%-50% RH, maintaining a uniform humidity across the adhesive layer. S8.2. After initial curing, raise the temperature to the target curing temperature of 120°C at a rate of 5°C / min and maintain the curing humidity at 40% to 50% RH. Allow the air in the constant temperature chamber to circulate evenly and continue curing for 2 hours under constant temperature and humidity conditions. S8.3. Cool down to room temperature at a rate of 1.5°C / min and remove the B-pillar assembly from the thermostat.

[0014] The present invention also provides a low-stress assembly and bonding device using the above-mentioned assembly method, comprising a base, a column, an upper adsorption platform, a lower adsorption platform, a robotic arm system, and a control platform, characterized in that: the lower adsorption platform is mounted on the base, the column is fixedly connected to the base and is located on one side of the base, a first vertical guide rail is provided on the column, the first vertical guide rail is connected to a first lifting mechanism, the upper adsorption platform is connected to the first lifting mechanism, and the upper adsorption platform is driven by the first lifting mechanism to move along the first vertical guide rail; The lower surface of the upper adsorption platform is uniformly distributed with adsorption heads A that can be raised and lowered, and the upper surface of the lower adsorption platform is uniformly distributed with adsorption heads B that can be raised and lowered. The lower surface of the upper adsorption platform is located directly above the upper surface of the lower adsorption platform. Each adsorption head A and adsorption head B are connected to the control platform, and the control platform controls the raising and lowering of each adsorption head A and adsorption head B. A second vertical guide rail is further provided on one side of the column, and a second lifting mechanism is connected to the second vertical guide rail. An infrared camera is installed on the second lifting mechanism, and the infrared camera is driven by the second lifting mechanism to move along the second vertical guide rail; The infrared camera and the second lifting mechanism are respectively connected to the control platform. The infrared camera transmits the collected image signal to the control platform, and the control platform controls the second lifting mechanism to move along the second vertical guide rail. The first lifting mechanism is connected to the control platform, and the control platform controls the first lifting mechanism to move up and down along the first vertical guide rail; The robotic arm system is installed on one side of the base, and the robotic arm system is connected to the control platform, and the control platform controls the operation of the robotic arm system; The upper adsorption platform includes a two-dimensional mobile platform and a substrate. The fixed part of the two-dimensional mobile platform is connected to the first lifting mechanism. The substrate is fixed on the moving part of the two-dimensional mobile platform, and the substrate is located below the two-dimensional mobile platform. The adsorption heads A are evenly distributed on the lower surface of the substrate.

[0015] The adsorption head A includes a micro linear motor A and a suction cup A. The base of the micro linear motor A is fixedly connected to the lower surface of the upper adsorption platform. The screw of the micro linear motor A faces downward, and the suction cup A is arranged at the lower end of the screw of the micro linear motor A. The suction cup A is connected to an external vacuum system through a pipeline, and the external vacuum system provides negative pressure for the suction cup A. The micro linear motor A is connected to the control platform. The adsorption head B includes a micro linear motor B and a suction cup B. The base of the micro linear motor B is fixedly connected to the upper surface of the lower adsorption platform. The screw of the micro linear motor B faces upward, and the suction cup B is arranged at the upper end of the screw of the micro linear motor B. The suction cup B is connected to an external vacuum system through a pipeline, and the external vacuum system provides negative pressure for the suction cup B. The micro linear motor B is connected to the control platform. The adsorption head A is equipped with a displacement sensor A, which is used to monitor the moving distance of the screw rod of the micro linear motor A; the adsorption head B is equipped with a displacement sensor B, which is used to monitor the moving distance of the screw rod of the micro linear motor B; the displacement sensor A and the displacement sensor B are respectively connected to the control platform.

[0016] The robotic arm system includes a vacuum fixture connected to the end of the robotic arm body, a vacuum system, a high-precision nozzle and a constant temperature tube. The vacuum fixture is connected to the vacuum system through a pipeline, and the vacuum system provides negative pressure for the vacuum fixture; the inlet of the high-precision nozzle is connected to the outlet of the constant temperature tube, and the inlet of the constant temperature tube is connected to the external glue supply system, and the external glue supply system inputs constant temperature glue to the high-precision nozzle through the constant temperature tube.

[0017] Beneficial effects of the present invention: The present invention achieves the coordinated optimization of five core parameters in the glue coating process: flow rate, thickness, shape, area, and temperature, and constructs a refined glue coating control mechanism adapted to the complex structure of the "outer steel, inner carbon" B-pillar. The flow rate is dynamically adjusted to adapt to the glue quantity requirements of different areas, and the thermal expansion differences of the buffer materials are buffered with a reasonable glue layer thickness. The glue coating shape is planned according to a preset trajectory to fit the surface features. Overlapping spraying is used to increase the area coverage of key areas, and constant temperature heating is combined to improve the fluidity of the glue. This process can be extended to body components such as A-pillars and door sills, providing an innovative technical path for the efficient and reliable manufacturing of multi-material bodies and expanding application scenarios.

[0018] 2. The present invention integrates a dual monitoring system of an infrared camera and a displacement sensor to capture gap data and screw displacement feedback in real time. This device can accurately control the thickness and pressure distribution of the adhesive layer during the assembly process, achieving uniform distribution and precise thickness control of the adhesive layer, and reducing stress concentration caused by uneven temperature and unbalanced pressure fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly according to the present invention.

[0020] Figure 2 This is a schematic diagram of the overall structure of the low-stress assembly bonding device of the present invention.

[0021] Figure 3 It is a side view schematic diagram of the low stress assembly bonding device of the present invention.

[0022] Figure 4 Schematic diagram of adsorption head A.

[0023] Figure 5 Schematic diagram of the tool carried at the end of the robotic arm body of the robotic arm system.

[0024] Figure 6 Schematic diagram of the structure of the outer panel of the B-pillar assembly in the present invention.

[0025] Figure 7 It is a schematic diagram of the overall structure of the B-pillar assembly in the present invention.

[0026] Figure 8Schematic diagram of a constant temperature box used in one embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings of this specification. It should be noted that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] To facilitate understanding of the present invention, the "steel outside, carbon inside" hybrid material B-pillar assembly is first described as follows: The overall structure of the "steel outside and carbon inside" hybrid material B-pillar assembly is as follows Figure 7 As shown, the "steel outside, carbon inside" hybrid material B-pillar assembly consists of an outer panel and an inner panel. To meet the dual requirements of side impact resistance and lightweighting, the outer panel is made of high-strength steel and designed as a variable thickness structure. The thickness parameters are optimized according to the force gradient distribution in different areas of the B-pillar. The thickness is enhanced in the key impact load-bearing area to improve structural rigidity. The thickness is moderately reduced in non-critical areas to achieve the goal of weight reduction and ensure structural protection performance in side impact, in line with the lightweight design concept of the entire vehicle. Figure 6 The five areas marked 5.1-5.5 represent five areas with different thickness differences on the inner surface of the outer plate based on the outer surface of the outer plate. The thickness in area 5.2 and area 5.4 is the smallest, and the thickness in area 5.1, area 5.3, and area 5.5 is relatively thick. The inner panel (not shown separately) is molded from carbon fiber composite materials, utilizing their high specific strength and high specific stiffness to further reduce the overall mass. At the same time, the fiber layup is optimized to enhance the coordinated force-bearing capacity with the outer panel, forming a "steel-carbon" composite reinforced structural system.

[0029] Aviation-grade AB-type structural adhesive is used as the bonding agent for the inner plate and the outer tube. Aviation-grade AB-type structural adhesive has excellent interface bonding strength, temperature resistance and fatigue resistance, and can meet the reliability requirements of the mixed material in long-term service. The main agent and curing agent are accurately mixed according to the preset ratio. The stirring process adopts a combination of low-speed stirring and directional shearing to ensure that the two components are fully integrated and evenly dispersed. The bubbles introduced during the mixing process are removed through vacuum degassing treatment to prevent the bubbles from forming stress concentration points after curing, providing a homogeneous and stable bonding medium for subsequent low-stress bonding assembly.

[0030] like Figure 1 As shown, the present invention first provides a low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly, comprising the following steps: Step S1: Establishing a thermodynamic model of the automobile B-pillar assembly and calculating the effective thickness of the adhesive layer in different regions based on the structural properties and thermal expansion coefficients of the B-pillar high-strength steel outer panel, carbon fiber inner panel, and adhesive; Step S1 is specifically as follows: First, based on the "steel outside, carbon inside" structural characteristics of the B-pillar assembly, the key performance parameters of the high-strength steel variable thickness outer panel, the carbon fiber inner panel, and the selected AB structural adhesive are integrated, with a focus on the structural properties (such as elastic modulus and Poisson's ratio) and thermal expansion behavior differences of each material. Because the thermal expansion properties of metals and composite materials differ significantly, interfacial stresses are easily induced under temperature cycling conditions. This characteristic serves as a core input variable for the simulation analysis. Secondly, based on the aforementioned material properties, a multi-physics thermodynamic model was constructed encompassing the adhesive, high-strength steel outer plate, and carbon fiber composite inner plate. The model focused on simulating temperature changes, interfacial stress transfer under assembly loads, and the mechanical response characteristics of the adhesive layer at different thickness parameters. Secondly, through simulation analysis, we focused on exploring the stress distribution characteristics of different areas of the B-pillar (such as straight sections, corners, and rib junctions) to clarify the differences in the stress state of the adhesive layer during load-bearing. For areas with high stress concentration, stress buffering is achieved through reasonable adhesive layer thickness design. For low stress areas, the adhesive layer thickness is optimized to reduce material consumption while ensuring connection strength. Finally, the simulation process iterates multiple parameters to simulate the interfacial stress level, bond strength reserve, and deformation coordination under different adhesive layer thicknesses, ultimately determining the effective thickness range for each region. This effective thickness simultaneously meets two core requirements: 1) sufficient structural strength to transmit loads and ensure the reliability of the inner and outer panel connections; 2) a reasonable thickness gradient design mitigates the additional stress caused by thermal expansion differences, preventing cracking or delamination of the adhesive layer due to excessive local stress. Step S2: importing a three-dimensional structural model of the B-pillar assembly into the control platform of the low-stress assembly and bonding device; the low-stress assembly and bonding device further comprises an upper adsorption platform, a lower adsorption platform, and a robotic arm system; the end of the robotic arm body of the robotic arm system is equipped with a vacuum clamp and a glue spraying mechanism; the lower surface of the upper adsorption platform is uniformly provided with liftable adsorption heads A, and the upper surface of the lower adsorption platform is uniformly provided with liftable adsorption heads B; based on the three-dimensional structural model of the B-pillar assembly, the control platform sets the placement area and posture of the outer panel on the lower adsorption platform, the placement area and posture of the inner panel on the upper adsorption platform, the starting position and motion trajectory of the robotic arm system for gripping the outer panel, the starting position and motion trajectory of the robotic arm system for gripping the inner panel, and the glue spraying trajectory of the robotic arm system; The control platform of the present invention is based on existing technology and can be an industrial computer equipped with graphics processing software and CAM software systems. The control platform software system includes a modeling module. The three-dimensional structural model of the B-pillar assembly is imported through the modeling module of the control platform software system. The software system automatically analyzes the geometric characteristics of the outer steel and inner carbon hybrid structure. Based on the results of the previous simulation analysis, the software system delineates the boundaries of the key bonding area in the model and clarifies the bonding range of the interfaces between different materials. The control platform's input module allows for the configuration of low-stress assembly constraints for the CAM software system. These constraints include key parameters such as the adhesive layer thickness fluctuation threshold and the assembly pressure range, ensuring that subsequent operations meet stress control requirements. For the robotic arm system, the control platform's input module and the CAM software system can also be used to preset the gripping reference positions for the inner and outer panels. These positions should avoid weak material areas and stress-sensitive locations to reduce the risk of structural deformation during gripping. Specifically, in the glue spraying trajectory planning phase, the CAM software system of the control platform generates the robot arm's operating path based on the geometric shape of the bonding area, and presets the motion parameters for the glue spraying mechanism carried by the robot arm, including key elements such as the spatial coordinates of the glue spraying starting and ending points, the path operation sequence, and the curvature radius at the turning point. The glue spraying trajectory planning takes the continuity and uniformity of the glue layer as the core goal, and optimizes the path direction to avoid sharp bends or sudden changes, ensuring a smooth transition of the glue head's motion state and providing accurate path guidance for subsequent low-stress glue spraying operations. The glue spraying trajectory parameters also include nozzle flow rate, glue spraying thickness, glue spraying area shape, glue spraying area area, and glue temperature. Step S3: Pre-treat the outer plate and inner plate separately. This mainly involves systematically and finely treating the contact surfaces of the two materials, improving the adhesive interface adhesion by optimizing the surface state, and achieving reliable bonding between the high-strength steel outer plate and the carbon fiber inner plate. For the surface of the high-strength steel outer plate, a dry sandblasting process is used for pre-treatment. High-speed abrasive particles are used to uniformly impact the metal surface, effectively removing impurities such as oxide layers, rust, and rolling residues. At the same time, a uniformly distributed micro-rough structure is formed on the surface, enhancing the mechanical interlocking effect between the adhesive and the metal interface. For the contact surface of the carbon fiber inner plate, appropriate sandblasting parameters are used to avoid fiber damage, focusing on removing contaminants such as surface release agents and epoxy resin floating layers, and improving the adhesive's wetting properties through moderate roughening. Immediately after sandblasting, a multi-stage cleaning process is carried out, using high-pressure clean air to blow away sand debris attached to the surface, followed by targeted wiping with a special solvent to thoroughly remove residual grease, organic pollutants and dust particles. During the cleaning process, avoid using corrosive media to prevent damage to the carbon fiber matrix structure. After cleaning, the contact surface is dried to ensure that there is no moisture remaining on the surface to avoid bubble defects caused by water vapor evaporation during the subsequent bonding process. Through the above surface treatment process, the physical adsorption capacity and chemical activity of the contact surface are improved, creating favorable conditions for the uniform spreading and sufficient infiltration of the adhesive. Step S4: The robotic arm system grasps the outer panel using the vacuum gripper at the end of the robotic arm body and places the outer panel in the preset placement area of ​​the lower adsorption platform. Multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform adsorb and secure the outer panel so that the outer panel conforms to the preset posture. In step S4, the contact end of the vacuum clamp is equipped with an insulating, heat-resistant, lightweight cushioning material to prevent local deformation of the outer panel during the clamping process. The robotic arm operates smoothly along a preset path to lift the outer panel onto the clamping device. The multiple adsorption heads B on the upper surface of the lower adsorption platform are designed as an adaptive support point array based on the curved surface features of the outer panel to ensure uniform adhesion between the outer panel and the support surface. In one embodiment of the present invention, the adsorption heads B on the upper surface of the lower adsorption platform are distributed in a 12×42 array. Each adsorption head B is equipped with a suction cup B and a linear motor B. The layout of the suction cups B corresponds to the main load-bearing area of ​​the outer panel. After the high-strength steel outer plate is in place, the vacuum adsorption system is activated. The atmospheric pressure difference causes the suction cup B of the adsorption head B to form a tight fit with the outer plate surface, and the negative pressure is used to achieve initial fixation. To monitor the position status of the outer plate in real time, the upper adsorption platform is equipped with a displacement sensor component. Each adsorption head B is equipped with a displacement sensor B. By monitoring the longitudinal displacement of the upper adsorption platform and each adsorption head B, the position change of the high-strength steel outer plate in three-dimensional space is obtained. During monitoring, the system selects characteristic points such as the four corner endpoints of the outer plate edge and key holes as the detection reference, and forms position information data by collecting and recording the three-dimensional coordinate data of each characteristic point. When the outer panel is placed in the preset placement area of ​​the lower adsorption platform and the multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform adsorb and fix the outer panel, an infrared camera is used to monitor the position and posture of the outer panel. The infrared camera captures the relative position relationship between the four corner endpoints of the inner panel and the four corner endpoints of the preset placement area, and generates posture data by continuously scanning the characteristic contour of the outer panel, and feeds back the position offset and angular error of the outer panel in three-dimensional space to the control platform in real time; if there is a position offset or angular error of the outer panel, the control platform controls the multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform according to the deviation signal to start fine-tuning action, so that the posture of the outer panel conforms to the set posture; Specifically, the measured coordinate data is compared and analyzed with the reference coordinates of the four corner endpoints of the set placement area to verify whether the overall flatness of the outer plate and the positional deviation of key feature points are within the allowable range. At the same time, the vacuum adsorption pressure is tested to maintain pressure, and the pressure change trend is observed to confirm the sealing reliability. Through the dual confirmation of position accuracy verification and adsorption stability testing, it is finally determined that the high-strength steel outer plate has been accurately and firmly positioned and fixed, providing reliable benchmark conditions for subsequent assembly processes. If the monitoring data indicates positional offset or angular error in the outer plate, the system automatically triggers the correction mechanism. To address displacement deviations, the lower adsorption platform remains stationary, and the linear position of the high-strength steel outer plate is changed through the axial extension and contraction of the adsorption head B. The rotational posture of the outer plate is fine-tuned by controlling the differential motion of the adsorption heads B distributed in a 12×42 array, ensuring the consistency of the overall flatness of the outer plate with the preset posture and achieving angular offset of the high-strength steel outer plate. During the correction process, the adjustment amount is synchronously monitored and the correction effect is fed back in real time, forming a closed-loop control of "detection-adjustment-feedback". After adjustment is complete, the outer panel's posture should be inspected again to confirm that both positional offset and angular error are within the allowable tolerance range, ultimately stabilizing the alignment accuracy between the outer panel and the four corner endpoints of the designated placement area within ±0.5mm. This process, through the coordinated use of mechanized inspection and correction, eliminates potential assembly deviations that may exist during the initial fixing phase of the outer panel, ensuring precise alignment during subsequent inner panel assembly and avoiding interfacial stress concentration or assembly misalignment caused by posture errors. This lays the key foundation for low-stress assembly of the hybrid material B-pillar. Step S5: The robotic arm system runs a glue spraying track, and glue is sprayed on the outer panel through the glue spraying mechanism carried by the end of the robotic arm body; the glue is heated to 40-50°C through a constant temperature pipe before entering the nozzle, which is conducive to achieving low-stress assembly; More specifically, the glue spraying mechanism adopts a closed-loop control mode, dynamically adjusting key process parameters according to the structural characteristics of the B-pillar: the glue flow rate is set within an adaptive range to meet the glue supply required for bonding strength while avoiding glue accumulation or overflow due to excessive flow; the nozzle moves along a preset trajectory, and the linear speed is flexibly adjusted according to regional characteristics. Higher speeds are used in flat and regular areas to improve operating efficiency and ensure uniform spreading of the glue layer; in the transition section of the B-pillar curved surface and local turning points, the spraying speed is automatically reduced, slowing down the glue application rate, allowing the glue to fully infiltrate and level the complex contour surface, improving the problem of uneven glue layer thickness caused by curvature changes, and improving the uniformity of glue adhesion; the glue layer thickness control aims at low stress buffering. Through multi-objective coordinated adjustment of glue coating shape, area, temperature, thickness and flow rate, the target glue layer thickness is kept within a reasonable range, ensuring sufficient bonding area and strength, and providing a buffer space for material thermal expansion differences; For complex contour areas such as B-pillar edges and corners, a multiple-layer overlapping spraying process is used to increase glue coverage through layered superposition, ensuring no missed coating or glue shortages in key stress-bearing areas, thus ensuring the integrity of the interface connection. The glue is preheated in a constant temperature pipeline before entering the nozzle. This moderate heating improves the glue's fluidity and wetting ability, reduces spraying defects caused by viscosity fluctuations, and creates conditions for uniform stress release during the subsequent curing process. Through the coordinated control of these multiple parameters, a low-stress spraying effect with uniform glue layer and complete coverage is ultimately achieved, thus achieving reliable bonding between metal and composite materials. Step S6: After the glue is sprayed on the outer panel, the robotic arm system uses the vacuum clamp mounted on the end of the robotic arm body to grasp the inner panel and place the inner panel in the preset placement area of ​​the upper adsorption platform. The multiple adsorption heads A in the preset placement area of ​​the lower adsorption platform adsorb and fix the inner panel so that the inner panel conforms to the preset posture. Step S7, bonding; the control platform controls the upper adsorption platform to move downward so that the inner plate reaches a predetermined position above the outer plate, completing the bonding; Step S8: placing the bonded B-pillar assembly in a constant temperature box for curing; Step S9: After curing, remove burrs and flash on the B-pillar assembly.

[0031] In step S6, when the inner panel is placed in the preset placement area of ​​the upper adsorption platform, after the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform adsorb and fix the inner panel, an infrared camera is used to monitor the position and posture of the inner panel. The infrared camera captures the relative position relationship between the four corner endpoints of the inner panel and the four corner endpoints of the set placement area, and generates posture data by continuously scanning the characteristic contour of the inner panel, and feeds back the position offset and angular error of the inner panel in three-dimensional space to the control platform in real time; if there is a position offset or angular error in the inner panel, the control platform controls the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform according to the deviation signal to start fine-tuning action, so that the posture of the outer panel conforms to the set posture; the specific fine-tuning method can refer to step S4 and will not be repeated here.

[0032] In step S7, after the control platform controls the upper adsorption platform to move downward so that the inner panel reaches a predetermined position above the outer panel, an infrared camera is used to monitor the distance between the lower surface of the inner panel and the upper surface of the outer panel in real time, and the monitoring information is transmitted to the control platform. Based on the monitoring information and the preset adhesive layer thickness, the control platform controls the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform to move downward synchronously so that the distance between the lower surface of the inner panel and the upper surface of the outer panel meets the preset adhesive layer thickness, thereby completing the bonding. Step S7 is specifically as follows: S7.1. The control platform controls the upper adsorption platform to move downward, moving the lower surface of the upper adsorption platform, which holds the inner panel, to the assembly area 300 mm above the outer panel. Simultaneously, activate the dual-position infrared camera shooting mode, with the left camera capturing images of the gap along the X-axis and the right camera capturing images of the gap along the Y-axis. S7.2. The control platform extracts the edge contour features of the inner and outer panels and constructs a three-dimensional coordinate mapping model by identifying positioning markers (such as 8mm / 10mm diameter bolt holes, positioning slots, and other key connection points). The coordinate accuracy is ±0.005mm. The control platform automatically calculates the horizontal deviation of the X and Y axes and the height difference of the Z axis (measurement accuracy is ±0.01mm). The control platform has a built-in deviation threshold judgment mechanism. When the X-axis deviation is greater than ±0.3mm, the Y-axis deviation is greater than ±0.2mm, or the Z-axis height difference is greater than ±0.5mm, the control platform immediately triggers a horizontal fine-tuning command, driving the two-dimensional mobile platform of the upper adsorption platform to perform position compensation, so that the outer and inner panels are initially aligned and qualified. S7.3. After the initial alignment is qualified, the control platform sends a vertical movement command to the upper adsorption platform based on the preset adhesive layer thickness. The control platform activates the first lifting mechanism of the upper adsorption platform, driving the upper plane to move vertically downward at a speed of 5 mm / s. During this process, the distance between the inner and outer panel surfaces is monitored in real time. When the remaining distance is 0.5 mm, the first lifting mechanism automatically switches to low speed mode (1 mm / s) and stops after reaching the preset coarse adjustment position, completing the coarse adjustment of the adhesive layer thickness. S7.4. Start the adsorption heads A arrayed on the lower surface of the upper adsorption platform. The linear motor A configured for adsorption heads A has a lead of 2 mm and a repeatability of ±0.003 mm, allowing for precise control of the adhesive layer thickness. An infrared camera focuses on the gap between the inner and outer panels, capturing real-time images of the preformed gap. This, combined with the displacement sensor A mounted at the end of the lead screw, forms a dual thickness monitoring mechanism. S7.5. During the extension and retraction of each suction head A, the control platform's software system compares the measured thickness with the target value every 10ms. When the infrared camera detects that the gap uniformity is ≤±0.01mm and the displacement sensor A indicates that the suction head A has reached the preset distance (error ≤0.005mm), the control platform issues a stop command, and the linear motor immediately powers off and brakes. The longitudinal displacement control error is ≤0.002mm, completing the precise control of the adhesive layer thickness. S7.6. After the adhesive layer thickness is determined, the control platform shall simultaneously strengthen the fixing mechanism, including: ① The vacuum cup B of each suction head B on the lower suction platform reaches a vacuum degree of -0.08MPa within 3 seconds, and a single suction cup generates an 80N suction force, ensuring that the outer panel is absolutely still. ② The suction cup A of each suction head A on the upper suction platform maintains a vacuum degree of -0.06MPa, continuously and stably adsorbing the inner panel. Simultaneously, 12mm diameter locating pins are synchronously inserted into the locating holes at the four corners of the B-pillar from both the top and the bottom, forming a composite fixing structure that combines vacuum adsorption and mechanical positioning. After fixing, the system is left stationary for 5 seconds, and displacement sensors A and B are used to confirm that there is no relative displacement change.

[0033] The step S8 is specifically as follows: S8.1. Place the bonded B-pillar assembly in a constant temperature oven and heat it from room temperature (20±5°C) to 40-60°C at a rate of 5°C / min. Perform initial curing within the 40-60°C temperature range to form a preliminary positioning adhesive layer. The ambient humidity for initial curing is 40%-50% RH, maintaining a uniform humidity across the adhesive layer. S8.2. After initial curing, raise the temperature to the target curing temperature of 120°C at a rate of 5°C / min and maintain the curing humidity at 40% to 50% RH. Allow the air in the constant temperature chamber to circulate evenly and continue curing for 2 hours under constant temperature and humidity conditions. S8.3. Cool down to room temperature at a rate of 1.5°C / min and remove the B-pillar assembly from the thermostat.

[0034] Specifically, step S8 implements process monitoring according to aviation-grade quality requirements: ① Record temperature, humidity, and airflow velocity near the adhesive layer every 20 minutes, creating an encrypted log. ② During the final 30 minutes of curing, infrared spectroscopy is enabled, with the sensor focused on the 3-5μm range, collecting spectral data every 8 minutes. The degree of cure is determined by analysis: a peak disappearance rate ≥ 98% is considered acceptable; a peak disappearance rate of 95% to 98% is considered acceptable, extending the cure time by 15 minutes; and a peak disappearance rate of 30 minutes is considered acceptable, with any deviations recorded.

[0035] Step S8 also generates a quality pre-assessment report 5 minutes before the end of curing, covering 12 indicators such as reaction completeness and temperature and humidity stability. The report uses data visualization to display the entire process curve and mark abnormal points. The original test data is retained for ≥90 days to meet quality traceability requirements.

[0036] In step S8.3, the temperature is lowered from 120°C to room temperature of 20°C at a rate of 1.5°C / min, wherein the following processes exist: ① 120-80°C stage: adopt circulating air cooling and natural heat dissipation, fan speed 800r / min, air flow speed 0.4m / s; ② below 80°C stage: turn off the fan and rely on natural heat dissipation from the box wall to ensure that the cooling curve has no drastic fluctuations.

[0037] Dynamic monitoring is implemented during the cooling process in step 8.3: In one embodiment of the present invention, four temperature sensors record data every 10 seconds, strictly controlling temperature deviations within ±1.5°C. The system compares the measured curve with the preset curve in real time. If deviations exceed the limit, compensation is provided by adjusting the opening of the heat dissipation holes or activating auxiliary devices. The humidity control system maintains 40% to 50% relative humidity and keeps the temperature below 50°C, minimizing microcracks in the adhesive layer caused by humidity fluctuations.

[0038] The thermostat used in step S8 is an intelligent thermostat. When the temperature stabilizes at 20°C, the thermostat emits an audible and visual prompt. After 10 minutes, the temperature difference between the inside and outside of the thermostat is allowed to equilibrate, and then the door opens at a controlled opening speed of 50 mm / s. Use a dedicated tool with a silicone non-slip pad to steadily lift the cured B-pillar assembly. Maintain a level surface during removal, ensuring a tilt angle of ≤5° to prevent deformation of the adhesive layer.

[0039] Finally, the removed B-pillar assembly is immediately placed in a constant temperature and humidity storage facility at 20±2°C and 45%±5% RH for 30 minutes to release internal stress. After this period, a specialized tool equipped with a diamond grinding head is used to remove edge burrs and adhesive flash, and a vacuum cleaner is used to remove debris. The completed B-pillar assembly is then transferred to the testing area for mechanical performance and appearance quality testing.

[0040] The present invention also provides a low-stress assembly and bonding device using the above-described assembly method, comprising a base 1, a column 2, an upper adsorption platform 3, a lower adsorption platform 4, a robotic arm system 5, and a control platform 6. The lower adsorption platform 4 is mounted on the base 1, the column 2 is fixedly connected to the base 1 and is located on one side of the base 1, the column 2 is provided with a first vertical guide rail 7, the first vertical guide rail 7 is connected to a first lifting mechanism 8, the upper adsorption platform 3 is connected to the first lifting mechanism 8, and the first lifting mechanism 8 drives the upper adsorption platform 3 to move along the first vertical guide rail 7; The lower surface of the upper adsorption platform 3 is uniformly distributed with liftable adsorption heads A9, and the upper surface of the lower adsorption platform 4 is uniformly distributed with liftable adsorption heads B10. The lower surface of the upper adsorption platform 3 is located directly above the upper surface of the lower adsorption platform 4. Each adsorption head A9 and adsorption head B10 is connected to the control platform 6, and the control platform 6 controls the lifting of each adsorption head A9 and adsorption head B10. A second vertical guide rail 11 is further provided on one side of the column 2. A second lifting mechanism 12 is connected to the second vertical guide rail 11. An infrared camera 13 is installed on the second lifting mechanism 12. The infrared camera 13 is driven by the second lifting mechanism 12 to move along the second vertical guide rail. The infrared camera 13 and the second lifting mechanism 12 are respectively connected to the control platform 6. The infrared camera 13 transmits the collected image signal to the control platform 6, and the control platform 6 controls the second lifting mechanism 12 to move along the second vertical guide rail 11. The first lifting mechanism 8 is connected to the control platform 6, and the control platform 6 controls the first lifting mechanism 8 to move up and down along the first vertical guide rail 7; The robotic arm system 5 is installed on one side of the base 1 and is connected to a control platform 6, which controls the operation of the robotic arm system 5; The upper adsorption platform 3 includes a two-dimensional mobile platform 31 and a substrate 32. The fixed part of the two-dimensional mobile platform 31 is connected to the first lifting mechanism 8. The substrate 32 is fixed on the moving part of the two-dimensional mobile platform 31, and the substrate 32 is located below the two-dimensional mobile platform 31. The adsorption heads A9 are evenly distributed on the lower surface of the substrate 32.

[0041] In the above structure, the first vertical guide rail 7 and the first lifting mechanism 8 are both existing technologies, so the specific structure is no longer shown in the figure. In one embodiment of the present invention, the first vertical guide rail 7 uses a rack and a slide rail, and the first lifting mechanism 8 includes a gear and a support driven by a servo motor. The support is slidably connected to the slide rail, and the gear is installed on the support. The gear is engaged with the rack, and the gear is driven to rotate by the servo motor. The gear is engaged with the rack, and the rotation of the gear is converted into linear motion through the rotation of the gear. The gear drives the support to move along the slide rail. Similarly, the two-dimensional mobile platform 31 is also existing technology, and its specific structure is no longer shown in the figure; the second vertical guide rail 12, the infrared camera 13, and the second lifting mechanism 12 are also existing technology, and their specific structure is no longer shown in the figure; The adsorption head A9 includes a micro linear motor A91 and a suction cup A92. The base of the micro linear motor A91 is fixedly connected to the lower surface of the upper adsorption platform 3. The screw of the micro linear motor A91 faces downward, and the suction cup A92 is arranged at the lower end of the screw of the micro linear motor A91. The suction cup A92 is connected to an external vacuum system through a pipeline, and the external vacuum system provides negative pressure for the suction cup A92. The micro linear motor A91 is connected to the control platform 6. The adsorption head B10 includes a micro linear motor B and a suction cup B. The base of the micro linear motor B is fixedly connected to the upper surface of the lower adsorption platform, the screw of the micro linear motor B faces upward, and the suction cup B is arranged at the upper end of the screw of the micro linear motor B. The suction cup B is connected to an external vacuum system through a pipeline, and the external vacuum system provides negative pressure for the suction cup B. The micro linear motor B is connected to the control platform. The micro linear motor A91 and the micro linear motor B are prior art, and their specific structures are not shown in the figure. The adsorption head A9 is equipped with a displacement sensor A93, which is used to monitor the movement distance of the screw rod of the micro linear motor A91; the adsorption head B10 is equipped with a displacement sensor B, which is used to monitor the movement distance of the screw rod of the micro linear motor B; the displacement sensor A93 and the displacement sensor B are respectively connected to the control platform 6.

[0042] The robotic arm system 5 includes a vacuum clamp 52, a vacuum system 53, a high-precision nozzle 54 and a constant temperature tube 55 connected to the end of the robotic arm body 51. The vacuum clamp 52 is connected to the vacuum system 53 through a pipeline, and the vacuum system 53 provides negative pressure for the vacuum clamp 52; the inlet of the high-precision nozzle 54 is connected to the outlet of the constant temperature tube 55, and the inlet of the constant temperature tube 55 is connected to the external glue supply system, and the external glue supply system inputs constant temperature glue to the high-precision nozzle 54 through the constant temperature tube 55.

[0043] The parts not described in detail in this invention are prior art.

Claims

1. A low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly, characterized by: The following steps are involved: Step S1: Establishing a thermodynamic model of the automobile B-pillar assembly and calculating the effective thickness of the adhesive layer in different regions based on the structural properties and thermal expansion coefficients of the B-pillar high-strength steel outer panel, carbon fiber inner panel, and adhesive; Step S2: importing a three-dimensional structural model of the B-pillar assembly into the control platform of the low-stress assembly and bonding device; the low-stress assembly and bonding device further comprises an upper adsorption platform, a lower adsorption platform, and a robotic arm system; the end of the robotic arm body of the robotic arm system is equipped with a vacuum clamp and a glue spraying mechanism; the lower surface of the upper adsorption platform is uniformly provided with liftable adsorption heads A, and the upper surface of the lower adsorption platform is uniformly provided with liftable adsorption heads B; based on the three-dimensional structural model of the B-pillar assembly, the control platform sets the placement area and posture of the outer panel on the lower adsorption platform, the placement area and posture of the inner panel on the upper adsorption platform, the starting position and motion trajectory of the robotic arm system for gripping the outer panel, the starting position and motion trajectory of the robotic arm system for gripping the inner panel, and the glue spraying trajectory of the robotic arm system; Step S3, pre-treating the outer plate and the inner plate separately; Step S4: The robotic arm system grasps the outer panel using the vacuum gripper at the end of the robotic arm body and places the outer panel in the preset placement area of ​​the lower adsorption platform. Multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform adsorb and secure the outer panel so that the outer panel conforms to the preset posture. Step S5: The robotic arm system runs a glue spraying track, and glue is sprayed on the outer panel through the glue spraying mechanism carried by the end of the robotic arm body; the glue is heated to 40-50°C through a constant temperature pipe before entering the nozzle, which is conducive to achieving low-stress assembly; Step S6: After the glue is sprayed on the outer panel, the robotic arm system uses the vacuum clamp mounted on the end of the robotic arm body to grasp the inner panel and place the inner panel in the preset placement area of ​​the upper adsorption platform. The multiple adsorption heads A in the preset placement area of ​​the lower adsorption platform adsorb and fix the inner panel so that the inner panel conforms to the preset posture. Step S7, bonding; the control platform controls the upper adsorption platform to move downward so that the inner plate reaches a predetermined position above the outer plate, completing the bonding; Step S8: placing the bonded B-pillar assembly in a constant temperature box for curing; Step S9: After curing, remove burrs and flash on the B-pillar assembly.

2. The low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly according to claim 1, characterized by: The step S3 is specifically as follows: sandblasting the contact surfaces of the outer plate and the inner plate to clean and remove impurities.

3. The low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly according to claim 1, characterized by: In step S4, after the outer panel is placed in the preset placement area of ​​the lower adsorption platform and the multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform adsorb and fix the outer panel, an infrared camera is used to monitor the position and posture of the outer panel. The infrared camera captures the relative position relationship between the four corner endpoints of the inner panel and the four corner endpoints of the set placement area, and generates posture data by continuously scanning the characteristic contour of the outer panel, and feeds back the position offset and angular error of the outer panel in three-dimensional space to the control platform in real time; if there is a position offset or angular error of the outer panel, the control platform controls the multiple adsorption heads B in the preset placement area of ​​the lower adsorption platform according to the deviation signal to start fine-tuning action, so that the posture of the outer panel conforms to the set posture.

4. The low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly according to claim 1, characterized by: In step S5, AB structural adhesive for aviation is used, and the ratio of component A to component B of the AB structural adhesive is 3:

7. The glue is stirred evenly before heating and bubbles are removed. When spraying the glue, the target glue layer thickness is controlled at 0.2-1.0 mm, and the glue coverage rate meets 95%.

5. The low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly according to claim 1, characterized by: In step S6, when the inner panel is placed in the preset placement area of ​​the upper adsorption platform, after the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform adsorb and fix the inner panel, an infrared camera is used to monitor the position and posture of the inner panel. The infrared camera captures the relative position relationship between the four corner endpoints of the inner panel and the four corner endpoints of the set placement area, and generates posture data by continuously scanning the characteristic contour of the inner panel, and feeds back the position offset and angular error of the inner panel in three-dimensional space to the control platform in real time; if there is a position offset or angular error of the inner panel, the control platform controls the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform according to the deviation signal to start fine-tuning action, so that the posture of the outer panel conforms to the set posture.

6. The low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly according to claim 1, characterized by: In step S7, when the control platform controls the upper adsorption platform to move downward so that the inner panel reaches the predetermined position above the outer panel, an infrared camera is used to monitor the distance between the lower surface of the inner panel and the upper surface of the outer panel in real time, and the monitoring information is transmitted to the control platform. The control platform controls the multiple adsorption heads A in the preset placement area of ​​the upper adsorption platform to move downward synchronously based on the monitoring information and the preset adhesive layer thickness, so that the distance between the lower surface of the inner panel and the upper surface of the outer panel meets the preset adhesive layer thickness, thereby completing the bonding.

7. The low-stress assembly method for a "steel outside, carbon inside" hybrid material B-pillar assembly according to claim 1, characterized by: The step S8 is specifically as follows: S8.

1. Place the bonded B-pillar assembly in a constant temperature oven and heat it from room temperature (20±5°C) to 40-60°C at a rate of 5°C / min. Perform initial curing within the 40-60°C temperature range to form a preliminary positioning adhesive layer. The ambient humidity for initial curing is 40%-50% RH, maintaining a uniform humidity across the adhesive layer. S8.

2. After initial curing, raise the temperature to the target curing temperature of 120°C at a rate of 5°C / min and maintain the curing humidity at 40% to 50% RH. Allow the air in the constant temperature chamber to circulate evenly and continue curing for 2 hours under constant temperature and humidity conditions. S8.

3. Cool down to room temperature at a rate of 1.5°C / min and remove the B-pillar assembly from the thermostat.

8. A low-stress assembly bonding device using the assembly method according to any one of claims 1 to 7, comprising a base, a column, an upper adsorption platform, a lower adsorption platform, a robotic arm system, and a control platform, wherein: The lower adsorption platform is installed on the base, the column is fixedly connected to the base and is located on one side of the base, the column is provided with a first vertical guide rail, the first vertical guide rail is connected to the first lifting mechanism, the upper adsorption platform is connected to the first lifting mechanism, and the first lifting mechanism drives the upper adsorption platform to move along the first vertical guide rail; The lower surface of the upper adsorption platform is uniformly distributed with adsorption heads A that can be raised and lowered, and the upper surface of the lower adsorption platform is uniformly distributed with adsorption heads B that can be raised and lowered. The lower surface of the upper adsorption platform is located directly above the upper surface of the lower adsorption platform. Each adsorption head A and adsorption head B are connected to the control platform, and the control platform controls the raising and lowering of each adsorption head A and adsorption head B. A second vertical guide rail is further provided on one side of the column, and a second lifting mechanism is connected to the second vertical guide rail. An infrared camera is installed on the second lifting mechanism, and the infrared camera is driven by the second lifting mechanism to move along the second vertical guide rail; The infrared camera and the second lifting mechanism are respectively connected to the control platform. The infrared camera transmits the collected image signal to the control platform, and the control platform controls the second lifting mechanism to move along the second vertical guide rail. The first lifting mechanism is connected to the control platform, and the control platform controls the first lifting mechanism to move up and down along the first vertical guide rail; The robotic arm system is installed on one side of the base, and the robotic arm system is connected to the control platform, and the control platform controls the operation of the robotic arm system; The upper adsorption platform includes a two-dimensional mobile platform and a substrate. The fixed part of the two-dimensional mobile platform is connected to the first lifting mechanism. The substrate is fixed on the moving part of the two-dimensional mobile platform, and the substrate is located below the two-dimensional mobile platform. The adsorption heads A are evenly distributed on the lower surface of the substrate.

9. The low-stress assembly bonding device according to claim 8, wherein: The adsorption head A includes a micro linear motor A and a suction cup A. The base of the micro linear motor A is fixedly connected to the lower surface of the upper adsorption platform. The screw of the micro linear motor A faces downward, and the suction cup A is arranged at the lower end of the screw of the micro linear motor A. The suction cup A is connected to an external vacuum system through a pipeline, and the external vacuum system provides negative pressure for the suction cup A. The micro linear motor A is connected to the control platform. The adsorption head B includes a micro linear motor B and a suction cup B. The base of the micro linear motor B is fixedly connected to the upper surface of the lower adsorption platform. The screw of the micro linear motor B faces upward, and the suction cup B is arranged at the upper end of the screw of the micro linear motor B. The suction cup B is connected to an external vacuum system through a pipeline, and the external vacuum system provides negative pressure for the suction cup B. The micro linear motor B is connected to the control platform. The adsorption head A is equipped with a displacement sensor A, which is used to monitor the moving distance of the screw rod of the micro linear motor A; the adsorption head B is equipped with a displacement sensor B, which is used to monitor the moving distance of the screw rod of the micro linear motor B; the displacement sensor A and the displacement sensor B are respectively connected to the control platform.

10. The low-stress assembly bonding device according to claim 8, wherein: The robotic arm system includes a vacuum fixture connected to the end of the robotic arm body, a vacuum system, a high-precision nozzle and a constant temperature tube. The vacuum fixture is connected to the vacuum system through a pipeline, and the vacuum system provides negative pressure for the vacuum fixture; the inlet of the high-precision nozzle is connected to the outlet of the constant temperature tube, and the inlet of the constant temperature tube is connected to the external glue supply system, and the external glue supply system inputs constant temperature glue to the high-precision nozzle through the constant temperature tube.

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