A post-tipping triggered automated fiber placement assisted compaction device and method

Abstract

The application discloses a back-tilt triggered automatic fiber placement auxiliary compaction device and method, and belongs to the technical field of automatic fiber placement of composite materials. The device is provided with an auxiliary compaction roller behind a main compaction roller along a laying direction, the auxiliary compaction roller is connected with a fiber placement head main body through a passive elastic loading assembly, and is offset in a direction away from the surface of a workpiece relative to the main compaction roller. The auxiliary compaction roller keeps a gap with the workpiece during normal laying; after the main compaction roller completely passes through a curvature transition region, the fiber placement head is back-tilted as a whole, the auxiliary compaction roller contacts the laid fiber bundle and implements secondary compaction through elastic loading. A target back-tilt angle is determined according to a calibration relation between the compaction amount of the auxiliary compaction roller and the secondary compaction force, and the posture of the fiber placement head is modified without changing the position coordinates and path movement direction parameters of a track. The application is suitable for automatic fiber placement compaction of edge and curvature change regions.

Description

Technical Field

[0001] This invention belongs to the field of automatic fiber placement molding technology for composite materials, specifically relating to an automatic fiber placement auxiliary compaction device and method triggered by backward tilting. Background Technology

[0002] Automated fiber placement is a crucial technology for automated molding of composite materials. During automated fiber placement, the placement head delivers multiple prepreg filament bundles to the area below the main pressure roller. Under the movement of the placement equipment and the pressure applied, the main pressure roller continuously presses the filament bundles onto the mold surface or the surface of the already laid-up layer. For planar areas or areas with gentle curvature changes, the main pressure roller can typically form a relatively stable contact area with the placement surface and apply continuous pressure to the filament bundles, thereby completing the placement and compaction of the filament bundles.

[0003] For C-shaped beams, L-shaped components, folded edge components, and other composite material components with sharp edges, rounded corners, or large curvature changes, the layup path typically requires passing through a curvature transition region from the first layup surface to the second layup surface. When the main pressure roller passes through this curvature transition region, the contact pattern between the main pressure roller and the workpiece surface changes with the local curvature. Due to the influence of the main pressure roller width, elastic deformation capacity, and the local curvature of the workpiece, some roller surfaces of the main pressure roller may not fully adhere to the workpiece surface, resulting in uneven force on the laid-up filaments. This can easily lead to problems such as insufficient local compaction, warping, or poor adhesion. Increasing the loading force of the main pressure roller to improve local compaction may also cause filament lateral displacement, excessive resin extrusion, or fiber disturbance, affecting the layup quality.

[0004] To improve the compaction quality of edges and areas with varying curvature, existing technologies propose setting auxiliary pressure rollers in addition to the main pressure rollers, and using the auxiliary pressure rollers to compact the laid filaments again after the main pressure rollers have completed the laying. For example, Chinese invention patent CN102700151B discloses a method and device for automatically laying prepreg yarns. After the main pressure rollers have completed the laying between adjacent surfaces, an auxiliary pressure roller is actively driven by a cylinder to compact the prepreg yarns extending to the second surface. This type of auxiliary compaction method can improve the compaction state of local areas to a certain extent, but the auxiliary pressure rollers require an independent active drive mechanism, and the extension, retraction, and loading timing of the auxiliary pressure rollers need to be controlled according to the position of the main pressure rollers and the laying process, increasing the complexity of the auxiliary compaction mechanism and its control process.

[0005] Meanwhile, for layup paths that include curvature transition regions, the timing of the auxiliary pressure roller's intervention needs to match the main pressure roller's passage through the curvature transition region. If the auxiliary pressure roller contacts the workpiece too early or has already laid the filament, the additional contact and pressure generated by the auxiliary pressure roller may affect the normal layup process when the main pressure roller passes through the curvature transition region. If the position coordinates of the original layup trajectory are changed in order to allow the auxiliary pressure roller to enter the working position, it may also change the original movement trajectory of the main pressure roller and the filament layup position. Therefore, how to enable the auxiliary pressure roller to perform secondary compaction on the area near the edge of the second layup surface after the main pressure roller has completed laying in this area without interfering with the main pressure roller passing through the curvature transition region is a problem that needs to be solved in the automatic filament laying process of complex curvature components.

[0006] Furthermore, during the secondary compaction process using the auxiliary pressure roller, variations in ply thickness, workpiece surface errors, and positioning errors of the fiber placement equipment can all cause changes in the actual contact position and pressing amount of the auxiliary pressure roller. If the auxiliary pressure roller uses rigid positioning or relies entirely on the active actuator to adjust its working position, then the position and pressing force of the auxiliary pressure roller need to be controlled accordingly. This is not conducive to simplifying the auxiliary compaction mechanism and increases the difficulty of retrofitting existing automatic fiber placement equipment with auxiliary compaction.

[0007] Therefore, it is necessary to provide an automatic filament laying auxiliary compaction device and method that, without relying on the independent active extension of the auxiliary pressure roller, allows the auxiliary pressure roller to enter the working state after the main pressure roller passes through the curvature transition area, performs delayed secondary compaction on the laid filament bundle, and can achieve the auxiliary compaction process while maintaining the original laying trajectory position and path movement direction, thereby improving the local compaction quality of edges, curvature abrupt change areas or large curvature transition areas. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an automatic yarn laying auxiliary compaction device and method with backward tilt triggering, which addresses the shortcomings of the prior art. This is to solve the problems that occur in the existing automatic yarn laying process when the main pressure roller passes through the edge, curvature change area or large curvature transition area, resulting in insufficient compaction, warping or poor bonding of the yarn bundle. The existing auxiliary compaction method relies on the independent active drive of the auxiliary pressure roller, the timing of the auxiliary pressure roller intervention is not easy to coordinate with the process of the main pressure roller passing through the curvature transition area, and the change in the original laying trajectory position may affect the normal laying of the main pressure roller and the laying position of the yarn bundle.

[0009] The present invention adopts the following technical solution: An automatic yarn-laying auxiliary compaction device triggered by tilting back includes a yarn-laying head body and a main pressure roller disposed at the lower part of the yarn-laying head body, characterized in that: The filament placement head body is provided with an auxiliary pressure roller mechanism behind the main pressure roller along the laying direction. The auxiliary pressure roller mechanism includes an auxiliary pressure roller and a passive elastic loading component. The auxiliary pressure roller is connected to the filament placement head body through the passive elastic loading component and can elastically float relative to the filament placement head body in a direction close to or away from the workpiece surface. The central axis of the auxiliary pressure roller is offset relative to the central axis of the main pressure roller in the laying direction and in a direction away from the workpiece surface. When the filament placement head body is in a normal placement posture, there is a preset gap between the auxiliary pressure roller and the workpiece surface; when the filament placement head body tilts backward along a posture axis parallel to the central axis of the main pressure roller in a direction that brings the auxiliary pressure roller close to the workpiece surface, the auxiliary pressure roller contacts the placed filament bundle and causes the passive elastic loading component to generate elastic deformation, so as to perform secondary compaction on the placed filament bundle.

[0010] Furthermore, the projection distance between the central axis of the auxiliary pressure roller and the central axis of the main pressure roller along the laying direction is 150~165mm, and the height offset along the direction away from the workpiece surface is 15~35mm. The diameters of the main pressure roller and the auxiliary pressure roller are 50~70mm respectively.

[0011] Furthermore, the auxiliary pressure roller mechanism also includes a mounting assembly, an auxiliary pressure roller support assembly, and an auxiliary pressure roller connecting shaft, wherein the auxiliary pressure roller is rotatably mounted on the auxiliary pressure roller support assembly via the auxiliary pressure roller connecting shaft; The passive elastic loading component includes a first air spring and a second air spring respectively disposed at both ends of the axial direction of the auxiliary pressure roller. One end of the first air spring and the second air spring are respectively connected to the mounting component, and the other end are respectively connected to the auxiliary pressure roller support component, and are passively compressed after the auxiliary pressure roller contacts the laid filament bundle.

[0012] Furthermore, the mounting assembly is provided with an angle adjustment structure and a locking structure. The angle adjustment structure is used to adjust the pre-installation tilt angle of the auxiliary pressure roller mechanism relative to the filament placement head body, and the locking structure is used to lock the pre-installation tilt angle. When the pre-installation tilt angle causes the filament laying head body to be in the target backward tilt working posture, the axial extension and contraction directions of the first gas spring and the second gas spring have a normal component toward the target laying surface.

[0013] Furthermore, the mounting assembly is also provided with a mechanical limiting structure, which limits the maximum compression of the first and second air springs by limiting the maximum displacement of the auxiliary pressure roller relative to the main body of the filament laying head.

[0014] Another technical solution of the present invention is a backward-tilted automatic filament placement assisted compaction method, which uses a filament placement head equipped with a main pressure roller and an auxiliary pressure roller located behind the main pressure roller along the placement direction, wherein the auxiliary pressure roller elastically floats relative to the filament placement head through a passive elastic loading component, and includes the following steps: Obtain the laying path of the component to be laid, and divide the laying path into a first laying area, a curvature transition area and a second laying area that are connected in sequence. The first laying area and the second laying area are located on the first laying surface and the second laying surface, respectively. When the main pressure roller is located in the first laying area and the curvature transition area, the conventional laying posture of the filament placement head is maintained; After the main pressure roller has completely passed through the curvature transition area and entered the second laying area, the trajectory position coordinates and path movement direction parameters of the laying path are kept unchanged, and the attitude parameters of the filament laying head are modified so that the filament laying head tilts backward around the attitude axis parallel to the central axis of the main pressure roller in the direction that brings the auxiliary pressure roller closer to the second laying surface, so that the auxiliary pressure roller contacts the filament bundle that has been laid by the main pressure roller. The passive elastic loading component is elastically deformed by the auxiliary pressure roller, thereby performing secondary compaction on the laid filament bundle; After completing the secondary compaction of the second laying surface near the edge area, the filament laying head is restored to the conventional laying posture.

[0015] Furthermore, a backward tilt transition zone and a recovery posture transition zone are set in the second laying area, so that the backward tilt angle of the filament laying head continuously increases from zero to the target backward tilt angle in the backward tilt transition zone, the target backward tilt angle is maintained in the secondary compaction zone, and after the secondary compaction is completed, the backward tilt angle continuously decreases from the target backward tilt angle to zero in the recovery posture transition zone.

[0016] Furthermore, based on the projected distance between the auxiliary pressure roller and the main pressure roller along the laying direction, the height offset along the direction away from the workpiece surface, the initial gap of the auxiliary pressure roller relative to the target laying surface, and the backward tilt angle of the filament placement head, the equivalent pressing amount of the auxiliary pressure roller relative to the target laying surface is determined.

[0017] Furthermore, the path motion direction vector is orthogonalized relative to the original attitude vector of the wire laying head, and the orthogonalized path motion direction vector is used as the attitude calculation reference. The modified filament placement head attitude vector is determined based on the orthogonalized path motion direction vector, the original attitude vector of the filament placement head, and the back tilt angle of the corresponding path point, and the modified filament placement head attitude vector is written into the placement path; The orthogonalized path motion direction vector is used as an intermediate quantity for attitude calculation and is not written back to the path motion direction parameters of the laid path.

[0018] Furthermore, a calibration relationship between the equivalent pressing amount and the secondary pressing force of the auxiliary pressure roller is established in advance. Within the effective range of the calibration relationship, the target pressing amount is determined based on the target secondary pressing force, and the target tilt angle is determined based on the target pressing amount.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: An automatic yarn-laying auxiliary compaction device with a backward-tilted triggering mechanism places an auxiliary pressure roller behind the main pressure roller, with both a rearward horizontal offset and a height offset away from the workpiece surface relative to the main pressure roller. This ensures that the auxiliary pressure roller maintains a gap with the workpiece during normal yarn laying and does not participate in the normal compaction of the main pressure roller. When secondary compaction is required, the auxiliary pressure roller approaches and contacts the laid yarn bundle by tilting the entire yarn-laying head backward. The switching of the auxiliary pressure roller's working state is achieved by the change in the yarn-laying head's own posture, eliminating the need for a separate actuator for the active extension of the auxiliary pressure roller. After contacting the yarn bundle, the auxiliary pressure roller undergoes elastic deformation due to the passive elastic loading component, generating compaction force. This allows for localized secondary compaction while retaining a certain degree of flexibility, making it more suitable for laying yarns with edges and curvature variations.

[0020] Furthermore, the projected distance, height offset, and diameter range of the auxiliary and main pressure rollers are defined. These parameters collectively determine the geometric approach of the auxiliary pressure roller to the workpiece surface when the filament placement head tilts backward, and also affect when the auxiliary pressure roller begins to contact the workpiece. By limiting the relative position and dimensions of the two pressure rollers, the auxiliary pressure roller remains in a non-working state in its normal posture, and obtains a proximity displacement that meets the requirements for secondary compaction after the filament placement head tilts backward.

[0021] Furthermore, a first air spring and a second air spring are respectively installed at both ends of the auxiliary pressure roller along its axial direction, and the auxiliary pressure roller is supported by an auxiliary pressure roller support assembly. Loading both ends separately ensures a more balanced force on the auxiliary pressure roller. After the auxiliary pressure roller contacts the yarn bundle, the two air springs are passively compressed with the displacement of the pressure roller, allowing the auxiliary pressure roller to float within a certain range. This gives the auxiliary pressure roller a certain degree of adaptability to changes in layup thickness, workpiece surface errors, and positioning errors of the yarn laying equipment, avoiding the use of a completely rigid compaction method.

[0022] Furthermore, an angle adjustment structure and a locking structure are provided to pre-adjust and fix the installation tilt angle of the auxiliary pressure roller mechanism relative to the main body of the filament placement head, so that when the filament placement head reaches the target backward tilt posture, the extension and contraction direction of the two gas springs has a normal component toward the target laying surface. The installation state of the auxiliary pressure roller mechanism is adjusted according to the specific filament placement head structure and the target working posture, so that the elastic effect generated by the gas springs can be effectively transmitted to the target laying surface, which is beneficial for the auxiliary pressure roller to stably implement secondary compaction.

[0023] Furthermore, the maximum displacement of the auxiliary pressure roller is limited by a mechanical limiting structure, while the maximum compression of the two gas springs is also limited. Mechanical boundaries are set for the floating range of the auxiliary pressure roller to prevent excessive displacement when the back tilt angle is large or local geometric errors are significant, and to prevent the gas springs from exceeding their allowable compression range, thus keeping the working position of the auxiliary pressure roller mechanism within the design limits.

[0024] An automatic filament placement assisted compaction method triggered by tilting back stipulates that the main pressure roller maintains a normal placement posture in the first placement area and the curvature transition area. Only after the main pressure roller has completely passed through the curvature transition area and entered the second placement area is the filament placement head tilted back, and the auxiliary pressure roller performs secondary compaction on the already placed filament bundle. This avoids the auxiliary pressure roller contacting the workpiece too early, which would affect the main pressure roller's passage through the curvature transition area. Simultaneously, the trajectory position coordinates and path movement direction parameters remain unchanged during the tilting process; only the filament placement head posture is adjusted. This allows for a localized secondary compaction process on top of the original placement trajectory, reducing modifications to the original placement path.

[0025] Furthermore, attitude transition zones are set at the beginning and end of the secondary compaction process, allowing the back tilt angle of the filament placement head to gradually increase and recover, rather than switching directly from zero back tilt angle to the target back tilt angle. This avoids sudden changes in the attitude of the filament placement head, allowing the auxiliary pressure rollers to gradually enter and exit the compaction state, reducing the impact of sudden attitude changes on the robot's movement and the contact process of the pressure rollers, and making the secondary compaction process more continuous.

[0026] Furthermore, the equivalent pressing amount of the auxiliary pressure roller is calculated using the projected distance, height offset, initial gap, and back tilt angle of the placement head relative to the main pressure roller. A clear geometric relationship is established between the back tilt of the placement head and the actual pressing amount of the auxiliary pressure roller, so that the attitude angle can be further used to determine the pressing degree of the auxiliary pressure roller.

[0027] Furthermore, before modifying the attitude of the filament-laying head, the path motion direction vector is orthogonalized relative to the original attitude vector, and the orthogonalization result is used only as an intermediate quantity for attitude calculation. Considering that discrete paths and numerical rounding may cause the two vectors to be not completely orthogonal, orthogonalization can obtain a more stable attitude calculation reference. At the same time, the original path motion direction parameters are not changed, only the new attitude vector is written back, keeping the original laying trajectory and path direction unchanged, and only the required back tilt attitude adjustment is completed.

[0028] Furthermore, a calibration relationship between the equivalent pressing amount of the auxiliary pressure roller and the secondary pressing force is established in advance. Based on the target secondary pressing force, the target pressing amount is first obtained, and then the target back tilt angle is determined from the target pressing amount. The pressure requirements required for auxiliary compaction are converted into executable yarn placement head posture parameters. Within the effective range of the calibration relationship, the pressing degree of the auxiliary pressure roller and the secondary pressing force are changed by adjusting the back tilt angle, so that the determination of the target back tilt angle has a clear basis.

[0029] In summary, this invention utilizes the overall backward tilt of the yarn laying head to trigger the contact of the rear auxiliary pressure roller with the yarn bundle, eliminating the need for an independent active extension mechanism for the auxiliary pressure roller, and achieving compliant secondary compaction through passive elastic loading; the main pressure roller starts auxiliary compaction after passing through the curvature transition area, which can reduce mutual interference, and at the same time, the compaction force can be adjusted while maintaining the original laying trajectory and path direction unchanged.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the overall structure of the backward-tilting triggered automatic filament placement auxiliary compaction device of the present invention installed behind the filament placement head; Figure 2 This is a schematic diagram showing the structure and main components of the auxiliary pressure roller mechanism of the present invention; Figure 3 This is a schematic diagram showing the relative positions and local coordinate relationships between the main pressure roller and the auxiliary pressure roller of the present invention; Figure 4 This is a schematic diagram of the present invention where the filament placement head maintains a conventional placement posture on the first placement surface and the auxiliary pressure roller is in a non-secondary compaction state; Figure 5 This is a schematic diagram showing that the filament layup head maintains a conventional laying posture when the main pressure roller passes through the curvature transition region of the present invention; Figure 6 This is a schematic diagram of the present invention where the main pressure roller enters the second laying surface, the yarn laying head tilts backward, and the auxiliary pressure roller performs secondary compaction in the area near the edge. Figure 7 This is a schematic diagram illustrating the process of the filament laying head tilting back and returning to its normal laying posture after the second compaction of the second laying surface near the edge area is completed.

[0033] The components are: 1. filament placement head body; 2. main pressure roller; 3. auxiliary pressure roller mechanism; 4. mounting assembly; 5. auxiliary pressure roller support assembly; 6. auxiliary pressure roller; 7. first gas spring; 8. second gas spring; 9. auxiliary pressure roller connecting shaft; 10. angle adjustment structure; 11. locking structure; 12. mechanical limiting structure; 13. filament feeding mechanism; 14. filament bundle; 15. workpiece; 16. first placement surface; 17. curvature transition area; 18. second placement surface; 19. placement direction; 20. central axis of main pressure roller; 21. central axis of auxiliary pressure roller. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0038] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0039] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0040] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0041] It should be noted that, in this invention, "layout direction" refers to the direction in which the filament placement head moves along the layout path and completes the filament layout; "rear" refers to the side located after the main pressure roller has completed one compaction, with the layout direction as the reference; and "backward tilt" refers to the filament placement head rotating around an attitude axis parallel to the central axis of the main pressure roller in a direction that brings the auxiliary pressure roller located behind the main pressure roller closer to the target layout surface.

[0042] This invention provides an automatic filament placement auxiliary compaction device and method with a backward-tilted trigger. An auxiliary pressure roller is set behind the main pressure roller along the placement direction, and the auxiliary pressure roller has a geometric offset relative to the main pressure roller, both backward and away from the workpiece surface. The auxiliary pressure roller maintains a preset gap in the normal posture of the filament placement head, and enters the contact state by tilting the entire filament placement head backward after the main pressure roller has completely passed through the curvature transition area. Thus, the existing posture freedom of the filament placement head replaces the independent active extension mechanism of the auxiliary pressure roller to complete the working state switch. After the auxiliary pressure roller contacts the filament bundle, a compliant secondary compaction force is formed by a passive elastic loading component, which can adapt to the layup thickness, workpiece error, and positioning error. At the same time, the target backward tilt angle is determined by the calibration relationship between the pressure amount of the auxiliary pressure roller and the secondary compaction force. In the path processing, the trajectory position coordinates and path movement direction parameters are kept unchanged, and only the posture of the filament placement head is modified. Thus, the edge and curvature change area are subjected to delayed secondary compaction while maintaining the original layup path as much as possible.

[0043] Example 1 Please see Figure 1 This invention discloses an automatic filament placement auxiliary compaction device triggered by a backward tilt, comprising a filament placement head body 1, a main pressure roller 2 disposed at the lower part of the filament placement head body 1, and an auxiliary pressure roller mechanism 3 disposed behind the main pressure roller 2 along the placement direction. The filament placement head body 1 is also provided with a filament feeding mechanism 13, which is used to transport the filament bundle 14 to the placement position of the main pressure roller 2. The main pressure roller 2 moves along the placement path with the filament placement head, pressing the filament bundle 14 onto the surface of the workpiece 15 or the surface of the already formed layup. The auxiliary pressure roller mechanism 3 is located on one side after the main pressure roller 2 has completed one compaction, and is used to perform a second compaction on the filament bundle 14 already placed by the main pressure roller 2 when the triggering conditions described later are met.

[0044] like Figure 1 and Figure 2 As shown, the auxiliary pressure roller mechanism 3 includes a mounting assembly 4, an auxiliary pressure roller support assembly 5, an auxiliary pressure roller 6, a first air spring 7, a second air spring 8, and an auxiliary pressure roller connecting shaft 9. The auxiliary pressure roller 6 is rotatably mounted on the auxiliary pressure roller support assembly 5 via the auxiliary pressure roller connecting shaft 9, so that the auxiliary pressure roller 6 can move with the yarn laying head and roll around the auxiliary pressure roller connecting shaft 9 after contacting the yarn bundle 14, compacting the laid yarn bundle 14.

[0045] The first gas spring 7 and the second gas spring 8 are respectively arranged at both ends of the auxiliary pressure roller 6 along its axial direction. One end of the first gas spring 7 and the second gas spring 8 are respectively connected to the mounting assembly 4, and the other end is respectively connected to the auxiliary pressure roller support assembly 5, thereby forming an elastic loading relationship between the mounting assembly 4 and the auxiliary pressure roller support assembly 5. When the auxiliary pressure roller 6 is displaced in the direction close to the mounting assembly 4 by the action of the workpiece 15 or the laid-out filament bundle 14, the first gas spring 7 and the second gas spring 8 are passively compressed with the movement of the auxiliary pressure roller support assembly 5; when the external action decreases, the first gas spring 7 and the second gas spring 8 can provide a corresponding elastic recovery action. Therefore, the auxiliary pressure roller 6 can elastically float within a limited range in the direction close to or away from the surface of the workpiece 15.

[0046] The first gas spring 7 and the second gas spring 8 constitute the passive elastic loading assembly in this embodiment. Here, "passive" means that the first gas spring 7 and the second gas spring 8 do not actively drive the auxiliary pressure roller 6 from a non-secondary compaction state to a secondary compaction state. Instead, after the auxiliary pressure roller 6 contacts the laid-up filament bundle 14 due to the overall backward tilt of the filament placement head, compression occurs as the auxiliary pressure roller 6 presses in, forming secondary compaction force. Therefore, the switching of the working state of the auxiliary pressure roller 6 and the formation of the compaction force are respectively accomplished by the change in the posture of the filament placement head and the passive elastic loading assembly.

[0047] The central axis 21 of the auxiliary pressure roller 6 is offset backward relative to the central axis 20 of the main pressure roller 2 along the laying direction, and also has a height offset in the direction away from the surface of the workpiece 15. Therefore, when the yarn placement head is in the normal laying posture, the auxiliary pressure roller 6 does not press against the workpiece 15 simultaneously with the main pressure roller 2, but maintains a preset gap with the surface of the workpiece 15, and the auxiliary pressure roller 6 is in a non-secondary compaction state. In this state, the main pressure roller 2 can complete the normal laying according to the original laying path.

[0048] When secondary pressing is required on the filament bundle 14 already laid by the main pressure roller 2, the filament placement head body 1 is tilted backward about an attitude axis parallel to the central axis 20 of the main pressure roller. Since the auxiliary pressure roller 6 has both a backward offset along the laying direction and a height offset along the direction away from the surface of the workpiece 15 relative to the main pressure roller 2, the backward tilt of the filament placement head can bring the auxiliary pressure roller 6 closer to the surface of the workpiece 15. When the geometric approach caused by the backward tilt overcomes the preset gap between the auxiliary pressure roller 6 and the target laying surface, the auxiliary pressure roller 6 contacts the filament bundle 14 already laid by the main pressure roller 2; when the filament placement head continues to reach the predetermined backward tilt posture, the auxiliary pressure roller 6 presses in, and passively compresses the first air spring 7 and the second air spring 8, thereby applying secondary pressing force to the filament bundle 14.

[0049] In one optional embodiment, the diameters of the main pressure roller 2 and the auxiliary pressure roller 6 are 50-70 mm respectively; the projected distance between the central axis 21 of the auxiliary pressure roller and the central axis 20 of the main pressure roller along the laying direction is 150-165 mm, and the height offset along the direction away from the surface of the workpiece 15 is 15-35 mm. In a specific structure, the diameters of both the main pressure roller 2 and the auxiliary pressure roller 6 are 60 mm, the projected distance is 157 mm, and the height offset is 25 mm. The above parameters can be selected according to the structural dimensions of the filament placement head and the allowable backward tilting range.

[0050] Please see Figure 2 The mounting assembly 4 is equipped with an angle adjustment structure 10 and a locking structure 11. The angle adjustment structure 10 is used to adjust the pre-installation tilt angle of the auxiliary pressure roller mechanism 3 relative to the yarn-laying head body 1. After the pre-installation tilt angle is adjusted to the set position, the locking structure 11 maintains the relative angle between the auxiliary pressure roller mechanism 3 and the yarn-laying head body 1. The pre-installation tilt angle is set so that when the yarn-laying head reaches the target backward tilting working posture, the axial extension and contraction direction of the first air spring 7 and the second air spring 8 has a normal component toward the target laying surface, so that the elastic action generated by the air spring can form a compaction force acting on the auxiliary pressure roller 6.

[0051] Mounting assembly 4 is also provided with a mechanical limiting structure 12. The mechanical limiting structure 12 limits the maximum floating displacement of the auxiliary pressure roller 6 and the auxiliary pressure roller support assembly 5 relative to the mounting assembly 4. When the auxiliary pressure roller 6 reaches the predetermined maximum displacement, its continued movement is restricted by the mechanical limiting structure 12, which correspondingly limits the maximum compression of the first gas spring 7 and the second gas spring 8, so that the floating range of the auxiliary pressure roller mechanism 3 is kept within the allowable range of the mechanism.

[0052] Please see Figure 3 To determine the relationship between the back tilt angle of the yarn layup head and the pressing degree of the auxiliary pressure roller 6, a local coordinate relationship is established in a local plane formed by the layup tangent t and the outward normal n of the workpiece surface. Here, the layup tangent t is positive with the layup direction as the positive direction, and the outward normal n of the workpiece surface is positive with the direction away from the workpiece surface as the positive direction. Let the center of the main pressure roller 2 be... The center of auxiliary pressure roller 6 is The projected distance between the auxiliary pressure roller 6 and the main pressure roller 2 along the laying direction is: The height offset along the direction away from the workpiece surface is The relative position between the center of the main pressure roller and the center of the auxiliary pressure roller is: (1) The above relative positional relationship and Figure 3 The actual arrangement of the main pressure roller 2 and the auxiliary pressure roller 6 corresponds to each other.

[0053] When the yarn-laying head tilts backward around the attitude axis parallel to the central axis 20 of the main pressure roller, along the direction that brings the auxiliary pressure roller 6 closer to the target laying surface, At that time, the auxiliary pressure roller 6 is backward biased relative to the main pressure roller 2. and height offset Together, they generate the geometric approach of the auxiliary pressure roller 6 toward the target laying surface: (2) in, This indicates that the wire placement head has rotated from its normal placement position to a backward tilt angle. At that time, the auxiliary pressure roller 6 moves geometrically closer to the target laying surface.

[0054] Let the equivalent initial gap of the auxiliary pressure roller 6 relative to the target laying surface under normal laying posture be... The equivalent pressing amount after the auxiliary pressure roller 6 contacts the already laid filament bundle 14. Represented as: (3) From equation (3), it can be seen that when At that time, the backward tilt of the yarn-laying head is insufficient for the auxiliary pressure roller 6 to overcome the initial gap, and the auxiliary pressure roller 6 does not produce secondary pressing; when When, exceeding the initial gap Part of it is converted into the equivalent pressing amount of the auxiliary pressure roller 6, and causes the passive elastic loading component to generate corresponding compression.

[0055] Before using the auxiliary compaction device, the equivalent pressing amount of the auxiliary roller 6 can be changed on a flat or representative workpiece surface, and the corresponding secondary compaction force can be measured to establish: (4) in, To enhance the secondary pressing force of auxiliary pressure roller 6, To assist the equivalent pressing amount of the pressure roller 6, This refers to the calibration function or lookup table obtained from calibration experiments. The calibration relationship can be expressed using piecewise linear interpolation, polynomial fitting, or direct table lookup, and is not limited to a specific functional form. When used to inversely calculate the target indentation based on the target secondary pressure, the equivalent indentation within the selected effective calibration interval has a monotonically corresponding relationship with the secondary pressure.

[0056] Given the target secondary pressure force, the target pressure amount is first obtained within the effective range of the calibration relationship according to equation (4). Then, within the allowable back tilt angle range of the auxiliary compaction device, the target back tilt angle is determined by the following formula. : (5) Therefore, the target secondary compaction force can be converted into the target pressing amount of the auxiliary pressure roller 6, and further converted into the target back tilt angle of the filament placement head. In practical applications, the corresponding secondary compaction force can also be measured directly at multiple back tilt angles to form a correspondence table between the back tilt angle and the secondary compaction force, and the corresponding back tilt angle can be selected according to the target secondary compaction force. The target back tilt angle is also limited by the auxiliary compaction requirements, the normal placement requirements of the main pressure roller, the load of the mechanism, and the allowable range of robot posture changes.

[0057] Example 2 This embodiment provides a backward-tilted triggered automatic filament placement and secondary compaction method. The filament placement head is equipped with a main pressure roller 2 and an auxiliary pressure roller 6 located behind the main pressure roller 2 along the placement direction. The auxiliary pressure roller 6 can elastically float relative to the filament placement head through a passive elastic loading component. The method is used when the component to be placed has sharp edges, abrupt curvature regions, or large curvature transition regions.

[0058] Please see Figures 4 to 7 Based on the geometry of the component to be laid and the laying path, the laying path is divided into a first laying area, a curvature transition area, and a second laying area that are connected sequentially. The first laying area is located on the first laying surface 16, the curvature transition area corresponds to the rounded corners or other curvature changes between the first laying surface 16 and the second laying surface 18, and the second laying area is located on the second laying surface 18. The second laying area includes a secondary compaction area near the edge and a posture recovery area after secondary compaction. A backward tilting posture transition area can be set before the secondary compaction area, and a posture recovery transition area can be set at the end of the secondary compaction area.

[0059] exist Figure 4 In the first working stage shown, the filament placement head is located on the first laying surface 16 and maintains a normal laying posture. The auxiliary pressure roller 6 maintains a preset gap with the surface of the workpiece 15, and the main pressure roller 2 performs one compaction on the filament bundle 14 along the original laying path. In this stage, no additional backward tilt is applied to the filament placement head for auxiliary compaction.

[0060] exist Figure 5 In the second working stage shown, the main pressure roller 2 enters and passes through the curvature transition region 17, the yarn layup head maintains its normal laying posture, and the auxiliary pressure roller 6 continues to be in a non-secondary compaction state, with the main pressure roller 2 independently completing the laying of the curvature transition region 17. In this way, the auxiliary pressure roller 6 will not intervene prematurely before the main pressure roller 2 has completed the curvature transition.

[0061] After the main pressure roller 2 has completely passed through the curvature transition region 17 and entered the second laying surface 18, it enters... Figure 6The third working stage is shown. At this time, while keeping the trajectory position coordinates and path movement direction parameters of the original laying path unchanged, the attitude parameters of the filament laying head are modified so that the filament laying head gradually tilts backward around the attitude axis parallel to the central axis 20 of the main pressure roller. As the backward tilt angle increases, the auxiliary pressure roller 6 moves closer to the second laying surface 18; after overcoming the preset gap, the auxiliary pressure roller 6 contacts the filament bundle 14 already laid by the main pressure roller 2, and causes the first air spring 7 and the second air spring 8 to be passively compressed, thereby performing secondary compaction on the filament bundle 14 in the area near the edge of the second laying surface 18.

[0062] After completing the secondary compaction of the area near the edge of the second paving surface 18, proceed to... Figure 7 The fourth working stage is shown. The yarn placement head gradually reduces its backward tilt angle until it returns to its normal laying posture. As the yarn placement head returns to its normal posture, the auxiliary pressure roller 6 moves away from the second laying surface 18 and exits the secondary compaction state. Throughout the entire working process, the auxiliary compaction is carried out after the main pressure roller 2 has completed the first compaction at the corresponding position, thus forming a secondary compaction process that is delayed along the laying direction.

[0063] In a preferred embodiment, the first... The discrete trajectory points are represented as follows: (6) in, For the first The trajectory coordinates of each path point; These are the parameters of the filament-laying head attitude vector; These are the parameters for the path motion direction vector.

[0064] First, normalize the attitude vector of the filament laying head and the path motion direction vector respectively: (7) (8) in, This represents the normalized original attitude vector of the filament layup head. This represents the normalized path motion direction vector.

[0065] Considering that path file discretization and numerical rounding may cause the wire-laying head attitude vector and the path motion direction vector to be not completely orthogonal, we orthogonalize the path motion direction vector relative to the original wire-laying head attitude vector, obtaining: (9) in, This is the orthogonalized path motion direction vector, used only as an intermediate quantity in calculating the modified filament-laying head attitude vector, and is not written back to the path file. .

[0066] According to the Backslope angles corresponding to each path point The modified filament-laying head attitude vector is: (10) Modified attitude vector Corresponding write At the same time, maintain as well as The orientation remains unchanged. Therefore, without altering the original placement trajectory position and path motion direction parameters, only the orientation of the filament-laying head at local path points is adjusted. The above vector processing method is a preferred approach; however, rotation matrices, quaternions, or other orientation representations supported by the robot controller can also be used while maintaining the same orientation change direction.

[0067] To avoid abrupt changes in orientation when the wire layup head transitions from the normal layup posture to the tilted posture and when it returns to the normal layup posture after secondary compaction, a tilted posture transition zone and a return posture transition zone are set in the second layup area. Let the initial path arc length of the tilted posture transition zone be... The transition length is The target lean angle is Then, a five-order smooth programming approach for entering the backsloping state is: (11) in: (12) The backslope angle obtained from equations (11) and (12) changes continuously at the start and end of the transition zone, and the first and second derivatives of the smoothing function at the start and end of the transition zone are both zero. After completing the secondary compaction of the second paving surface 18 near the edge region, the same smoothing method can be used in reverse in the attitude recovery transition zone to make the backslope angle change from the target backslope angle. Decrease continuously to zero.

[0068] The quintic smoothing function is a preferred form in this embodiment. A cubic polynomial, cosine function, spline function, or the smoothing function built into the robot controller can also be used, as long as the back tilt angle can be changed continuously.

[0069] Example 3 In one specific embodiment, automatic filament placement is performed on a C-shaped cross-section member with a 5mm radius rounded corner transition. Both the main pressure roller 2 and the auxiliary pressure roller 6 can have a diameter of 60mm. The projected distance between the auxiliary pressure roller's central axis 21 and the main pressure roller's central axis 20 along the placement direction is 157mm, and the height offset along the direction away from the workpiece surface is 25mm. This combination of dimensions falls within the aforementioned parameter range.

[0070] Before laying begins, the calibration relationship shown in equation (4) is established based on the calibration test between the pressing amount of the auxiliary pressure roller 6 and the secondary pressing force. The target pressing amount is obtained according to the target secondary pressing force to be applied. Then, the target backward tilt angle is determined by equation (5) by combining the projected distance and height offset between the auxiliary pressure roller 6 and the main pressure roller 2, as well as the initial gap between the auxiliary pressure roller 6 and the target laying surface. The pre-installation tilt angle of the auxiliary pressure roller mechanism 3 is adjusted according to the determined target backward tilt angle, and the pre-installation tilt angle is maintained by the locking structure 11. At the same time, it is ensured that the axial extension and contraction directions of the first air spring 7 and the second air spring 8 have a normal component toward the target laying surface under the target backward tilt working posture.

[0071] During actual placement, when the main pressure roller 2 is located in the curvature transition area 17 corresponding to the first placement surface 16 and the 5mm rounded corner, the placement head does not apply any additional backward tilt for auxiliary compaction, and the auxiliary pressure roller 6 remains in a non-secondary compaction state. After the main pressure roller 2 has completely passed the rounded corner and entered the second placement surface 18, the backward tilt angle of the placement head is gradually increased within the preset backward tilt posture transition distance. After overcoming the initial gap, the auxiliary pressure roller 6 contacts the yarn bundle 14 already placed by the main pressure roller 2, and the first air spring 7 and the second air spring 8 are passively compressed to form secondary compaction force. After secondary compaction is completed in the predetermined area near the edge of the second placement surface 18, the backward tilt angle is gradually reduced to zero within the recovery posture transition distance, so that the placement head returns to the normal placement posture and the auxiliary pressure roller 6 exits the secondary compaction state.

[0072] The aforementioned C-shaped cross-section component is only one specific application. This invention can also be used for L-shaped components, folded-edge components, and composite material components with sharp edges, abrupt curvature regions, or large curvature transition regions. The component form, fillet radius, pressure roller size, positional offset between the main and auxiliary pressure rollers, the elastic element form of the passive elastic loading assembly, and the attitude smoothing function can all be adjusted according to the workpiece geometry, layup thickness, material system, and equipment load-bearing capacity. The basic working relationship remains as follows: the entire filament-laying head tilts backward, causing the rear auxiliary pressure roller to move from a non-contact state to a contact state. After the auxiliary pressure roller contacts the laid filament bundle, the passive elastic loading assembly forms a secondary pressure force.

[0073] In summary, this invention provides an automatic filament placement auxiliary compaction device and method with a backward-tilting trigger. Addressing the problem of insufficient compaction in areas with edges and curvature changes during automatic filament placement, an auxiliary pressure roller capable of elastic floating is installed behind the main pressure roller. The backward and height offsets between the auxiliary and main pressure rollers maintain a gap between the auxiliary roller and the workpiece in a normal placement posture. After the main pressure roller has completely passed through the curvature transition area, the filament placement head tilts backward to bring the auxiliary roller into contact with the placed filament bundle. A passive elastic loading component then provides secondary compaction force, eliminating the need for a separate active extension mechanism for the auxiliary roller. This structure reduces interference from the auxiliary roller when the main pressure roller passes through the curvature transition area and adapts to layup thickness, workpiece errors, and positioning errors through elastic floating. Furthermore, this invention establishes a calibration relationship between the auxiliary roller's pressing amount and the secondary compaction force, allowing the target backward tilt angle to be determined based on the target compaction force. During path processing, the trajectory position coordinates and path movement direction parameters remain unchanged; only the filament placement head posture is adjusted. Therefore, localized secondary compaction can be achieved based on the existing placement path.

[0074] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A tilt-triggered automatic fiber placement auxiliary compaction device, characterized in that, It includes a yarn-laying head body (1) and a main pressure roller (2) disposed at the lower part of the yarn-laying head body (1), characterized in that: The main body (1) of the filament placement head is provided with an auxiliary pressure roller mechanism (3) behind the main pressure roller (2) along the laying direction. The auxiliary pressure roller mechanism (3) includes an auxiliary pressure roller (6) and a passive elastic loading component. The auxiliary pressure roller (6) is connected to the main body (1) of the filament placement head through the passive elastic loading component and can elastically float relative to the main body (1) in the direction of approaching or moving away from the surface of the workpiece (15). The central axis (21) of the auxiliary pressure roller (6) is offset relative to the central axis (20) of the main pressure roller (2) in the laying direction and in a direction away from the surface of the workpiece (15); When the filament laying head body (1) is in a normal laying posture, there is a preset gap between the auxiliary pressure roller (6) and the surface of the workpiece (15); when the filament laying head body (1) tilts backward along the posture axis parallel to the central axis (20) of the main pressure roller (2) in the direction that makes the auxiliary pressure roller (6) approach the surface of the workpiece (15), the auxiliary pressure roller (6) contacts the laid filament bundle (14) and causes the passive elastic loading component to generate elastic deformation, so as to perform secondary compaction on the laid filament bundle (14).

2. The automatic fiber placement auxiliary compaction device triggered by backward tilting according to claim 1, characterized in that, The projection distance between the central axis (21) of the auxiliary pressure roller (6) and the central axis (20) of the main pressure roller (2) along the laying direction is 150~165mm, and the height offset along the direction away from the surface of the workpiece (15) is 15~35mm. The diameters of the main pressure roller (2) and the auxiliary pressure roller (6) are 50~70mm respectively.

3. The automatic fiber placement auxiliary compaction device triggered by backward tilting according to claim 1, characterized in that, The auxiliary pressure roller mechanism (3) further includes a mounting assembly (4), an auxiliary pressure roller support assembly (5), and an auxiliary pressure roller connecting shaft (9). The auxiliary pressure roller (6) is rotatably mounted on the auxiliary pressure roller support assembly (5) via the auxiliary pressure roller connecting shaft (9). The passive elastic loading component includes a first air spring (7) and a second air spring (8) respectively disposed at both ends of the axial direction of the auxiliary pressure roller (6). One end of the first air spring (7) and the second air spring (8) are respectively connected to the mounting component (4), and the other end is respectively connected to the auxiliary pressure roller support component (5). The auxiliary pressure roller (6) is passively compressed after contacting the laid filament bundle (14).

4. The automatic fiber placement auxiliary compaction device triggered by backward tilting according to claim 3, characterized in that, The mounting assembly (4) is provided with an angle adjustment structure (10) and a locking structure (11). The angle adjustment structure (10) is used to adjust the pre-installation tilt angle of the auxiliary pressure roller mechanism (3) relative to the filament laying head body (1). The locking structure (11) is used to lock the pre-installation tilt angle. When the pre-installation tilt angle causes the filament laying head body (1) to be in the target backward tilt working posture, the axial extension and contraction directions of the first gas spring (7) and the second gas spring (8) have a normal component toward the target laying surface.

5. The automatic fiber placement auxiliary compaction device triggered by backward tilting according to claim 4, characterized in that, The mounting assembly (4) is also provided with a mechanical limiting structure (12), which limits the maximum compression of the first air spring (7) and the second air spring (8) by limiting the maximum displacement of the auxiliary pressure roller (6) relative to the filament laying head body (1).

6. A method for automatic fiber placement-assisted compaction triggered by backward tilting, characterized in that, Using a yarn-placement head equipped with a main pressure roller and an auxiliary pressure roller located behind the main pressure roller in the layup direction, wherein the auxiliary pressure roller elastically floats relative to the yarn-placement head via a passive elastic loading component, the method includes the following steps: Obtain the laying path of the component to be laid, and divide the laying path into a first laying area, a curvature transition area and a second laying area that are connected in sequence. The first laying area and the second laying area are located on the first laying surface and the second laying surface, respectively. When the main pressure roller is located in the first laying area and the curvature transition area, the conventional laying posture of the filament placement head is maintained; After the main pressure roller has completely passed through the curvature transition area and entered the second laying area, the trajectory position coordinates and path movement direction parameters of the laying path are kept unchanged, and the attitude parameters of the filament laying head are modified so that the filament laying head tilts backward around the attitude axis parallel to the central axis of the main pressure roller in the direction that brings the auxiliary pressure roller closer to the second laying surface, so that the auxiliary pressure roller contacts the filament bundle that has been laid by the main pressure roller. The passive elastic loading component is elastically deformed by the auxiliary pressure roller, thereby performing secondary compaction on the laid filament bundle; After completing the secondary compaction of the second laying surface near the edge area, the filament laying head is restored to the conventional laying posture.

7. The automatic fiber placement-assisted compaction method triggered by backward tilting according to claim 6, characterized in that, A backward tilt transition zone and a recovery tilt transition zone are set in the second laying area, so that the backward tilt angle of the filament laying head continuously increases from zero to the target backward tilt angle in the backward tilt transition zone, the target backward tilt angle is maintained in the secondary compaction zone, and after the secondary compaction is completed, the backward tilt angle continuously decreases from the target backward tilt angle to zero in the recovery tilt transition zone.

8. The automatic fiber placement-assisted compaction method triggered by backward tilting according to claim 6, characterized in that, The equivalent pressing amount of the auxiliary pressure roller relative to the target laying surface is determined based on the projected distance of the auxiliary pressure roller relative to the main pressure roller in the laying direction, the height offset in the direction away from the workpiece surface, the initial gap of the auxiliary pressure roller relative to the target laying surface, and the back tilt angle of the filament placement head.

9. The automatic fiber placement-assisted compaction method triggered by backward tilting according to claim 6, characterized in that, The path motion direction vector is orthogonalized relative to the original attitude vector of the wire lay-up head, and the orthogonalized path motion direction vector is used as the attitude calculation reference. The modified filament placement head attitude vector is determined based on the orthogonalized path motion direction vector, the original attitude vector of the filament placement head, and the back tilt angle of the corresponding path point, and the modified filament placement head attitude vector is written into the placement path; The orthogonalized path motion direction vector is used as an intermediate quantity for attitude calculation and is not written back to the path motion direction parameters of the laid path.

10. The automatic fiber placement-assisted compaction method triggered by backward tilting according to claim 6, characterized in that, A calibration relationship between the equivalent pressing amount and the secondary pressing force of the auxiliary pressure roller is established in advance. Within the effective range of the calibration relationship, the target pressing amount is determined according to the target secondary pressing force, and the target tilt angle is determined according to the target pressing amount.

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