A fitting part repair allowance determination method based on assembly reference constraint

Abstract

The application discloses a kind of based on assembly reference constraint's fitting piece repair allowance determination method, it is related to the technical field of digital repair of aircraft assembly, the method obtains the point cloud of real measurement of spare part and reference part, respectively extract hinge axis and lock point position;With hinge axis coincidence as constraint, minimum lock point in position error is registered, and assembly pose is obtained;Along with fitting edge discrete sampling and establish the local frame of clearance direction and step difference direction;By reference piece measured boundary, obtain target boundary by the clearance and step difference bias of theory, the deviation of spare part measured boundary relative to target boundary is projected along clearance and step difference direction, and repair allowance field is obtained;When clearance allowance is negative, re-optimization is carried out in adjustable quantity to eliminate negative allowance, and it is judged to be out of tolerance alarm if it cannot be eliminated. The method realizes the measured determination of repair amount, the decoupling measurement of allowance under the constraint of real assembly reference and the pre-judgment of material shortage before processing.

Description

Technical Field

[0001] This invention belongs to the field of digital repair technology for aircraft assembly, specifically relating to a method for determining the repair allowance of mating parts based on assembly datum constraints. Background Technology

[0002] Aircraft assembly involves numerous mating parts, such as doors and frames, covers and frames, moving surfaces and fixed surfaces. One part must be fitted into or fitted to the area enclosed by another part. After assembly, the mating parts must meet the design requirements for surface gaps and step differences. Due to factors such as composite material molding shrinkage, sheet metal springback, manufacturing errors, and clamping deformation, the actual surface profile of the mating parts after manufacturing and clamping deviates from the theoretical model. Direct assembly often cannot simultaneously meet the gap and step difference requirements. Therefore, it is necessary to adjust the mating edges of one part, removing excess material to ensure the mating parts meet the design requirements.

[0003] In related technologies, the main methods for fitting mating parts are as follows: First, determining the fitting amount based on a theoretical model. Using the theoretical model as the machining target, the allowance relative to the theoretical position of the mating edge is used as the removal amount. This method replaces the actual surface with the theoretical model, but the actual surface has deviated from the theoretical position, leading to both over-cutting and under-cutting. Second, relying on the fitter's experience for trial fitting. The fitter repeatedly measures the clearance and step difference of the mating parts using feeler gauges and surface gauges, and files the mating edges based on experience, gradually approximating the fit while adjusting. This method relies on manual experience, resulting in low efficiency, inconsistency, and difficulty in guaranteeing fitting quality. Third, a digital fitting method based on measured point clouds. This method involves three-dimensional scanning of the mating part and the area to be installed, reconstructing the surface, establishing a correspondence between the boundary of the mating part and the area to be installed, and calculating the machining allowance. Although this method replaces the theoretical model with measured point clouds, the correspondence either uses non-rigid mapping that allows surface deformation or overall geometric fitting, neither of which is uniquely determined by the actual assembly datum of the mating part. The fourth method is the registration method with uniform allowance as a constraint. The registration and allowance are calculated with the goal of making the allowance between the mating parts and the area to be installed uniform. However, the assembly posture obtained by this method is not the actual position of the mating parts determined by assembly references such as hinges and locking points. The allowance calculated accordingly cannot reflect the repair and fitting requirements under actual assembly conditions.

[0004] However, the above methods share the following shortcomings: First, none of them constrain the assembly posture of the mating parts using the actual assembly datum of the mating parts, i.e., positioning elements such as hinges and locking points. The determined posture is derived from theoretical models, non-rigid mappings, or uniform allowance constraints, which are not the actual positioning state determined by the assembly datum during actual assembly. Therefore, the repair amount determined accordingly does not match the repair requirements under actual assembly conditions. Second, all methods treat the mating edge allowance as a single distance quantity, failing to distinguish the gap and step difference of the outer surface face seam as two independent components in the seam width direction and normal direction for separate measurement. However, the gap and step difference are two independent assembly indicators that must meet their respective design requirements. Third, none of them make a prior judgment and handling of situations where there is insufficient material in a certain part of the mating part, i.e., removing the material cannot meet the design requirements, before processing. Often, it is only after repair that it is discovered that the part cannot be repaired.

[0005] To address this, the present invention proposes a method for determining the fitment allowance of mating parts based on assembly datum constraints. By using the coincidence of hinge axes as a constraint and minimizing the locking point positioning error as the objective, the actual assembly posture of the mating parts, determined by the assembly datum, is determined. A local frame is established along the mating edge in the clearance direction and the step difference direction to decouple the allowance into two directional components for separate measurement. By determining the negative allowance and re-optimizing the posture, the pre-processing judgment and handling of material shortage and deviation are achieved. This effectively solves the problems of the lack of assembly datum constraints leading to discrepancies between the fitment posture and the actual assembly state, the inability to separately meet two independent assembly indicators due to the mixing of clearance and step difference as a single allowance, and the inability to pre-judge material shortages before processing. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a method for determining the fitting allowance of mating parts based on assembly datum constraints. The method for determining the fitting allowance of mating parts based on assembly datum constraints realizes the determination of the fitting amount under the real assembly datum constraints determined by the coincidence of hinge axes and the minimum positioning error of locking points. At the same time, it realizes the decoupled measurement of gap and step difference, as well as the pre-processing judgment and handling of material shortage and deviation.

[0007] To solve the above problems, the present invention adopts the following technical solution: A method for determining the repair allowance of mating parts based on assembly datum constraints, wherein the mating parts include the part to be repaired and a datum part, comprising the following steps: S1, Obtain the measured data of the part to be repaired and the measured data of the reference part; S2, extract assembly datum elements from the measured data of the part to be repaired and the reference part respectively, wherein the assembly datum elements include at least the position of the hinge axis and the locking point mating structure; S3, taking the rigid body transformation of the part to be repaired relative to the reference part as the variable, taking the coincidence of the hinge axis of the part to be repaired and the hinge axis of the reference part as the constraint, and taking the minimum positioning error of the locking point fit structure as the objective, solve the assembly pose of the part to be repaired relative to the reference part. S4, under the assembly posture, determine the actual measured mating edge of the part to be repaired and the corresponding actual measured boundary of the reference part, set a number of sampling points along the mating edge, and establish a local reference system at each sampling point to distinguish between the gap direction and the step direction; S5. Based on the measured boundary of the reference component, construct the target boundary according to the theoretical gap and theoretical step difference required by the design. Project the deviation of the measured boundary of the part to be repaired relative to the target boundary at each sampling point along the gap direction and the step difference direction respectively to obtain the repair allowance field distributed along the mating edge. S6, determine whether there is a negative allowance in the repair allowance field that represents insufficient material. If not, output the repair allowance field. If it exists, adjust the assembly posture within the adjustable range between the part to be repaired and the reference part to eliminate the negative allowance, and redetermine the repair allowance field according to the adjusted assembly posture. If the negative allowance still exists after adjustment, determine that it is out of tolerance and output an alarm signal.

[0008] Furthermore, in step S2, the hinge axis of the component to be repaired and the hinge axis of the reference component are respectively obtained by fitting the measured point cloud of their respective hinge seat cylindrical surfaces according to the minimum sum of the squares of the vertical distances from each measured point to the axis.

[0009] Furthermore, in step S2, the assembly reference element also includes a mating surface; in step S3, the constraints that do not interfere with the normal direction at the mating surface are included in the registration in the form of inequality constraints or penalty functions.

[0010] Furthermore, in step S3, the positioning error of the locking point fit structure aims to minimize the sum of the squares of the distances between the center of each locking point fit structure and the center of the corresponding locking pin; the constraint of the coincidence of the hinge axis eliminates the degree of freedom in the hinge direction, and the remaining degree of freedom is determined by the positioning error term of the locking point fit structure.

[0011] Further, in step S4, the local reference system is composed of the tangent of the mating edge at the sampling point, the outward normal of the mating surface, and the direction obtained by the cross product of the two; wherein, the outward normal of the mating surface is the step difference direction, and the direction obtained by the cross product is the gap direction.

[0012] Furthermore, in step S4, when setting sampling points along the mating edge, the sampling interval is adaptively determined according to the curvature of the mating edge, and the sampling interval is reduced where the curvature is large.

[0013] Furthermore, in step S5, the deviation of the measured boundary of the part to be repaired relative to the target boundary is projected onto the gap direction to obtain the gap margin component, and projected onto the step difference direction to obtain the step difference margin component. The repair margin field is composed of the gap margin component and the step difference margin component of each sampling point.

[0014] Further, in step S5, the target boundary is obtained by offsetting the measured boundary of the reference part along the gap direction according to the theoretical gap and along the step difference direction according to the theoretical step difference; the theoretical gap and / or the theoretical step difference is a design function that varies along the mating edge.

[0015] Further, in step S6, adjusting the assembly pose within the adjustable range to eliminate the negative margin specifically involves: solving for a pose increment within the adjustable range such that the gap margin component of each sampling point after adjustment is not less than zero; if there is no pose increment within the adjustable range that makes the gap margin component of each sampling point not less than zero, then it is determined to be out of tolerance. The adjustable range is given by the adjustable range of the hinge and locking point mating structure. Adjusting the assembly pose within the adjustable range is a redistribution of the fitting margin along the mating edge, which is different from pose adjustment aimed at making the gap uniform.

[0016] Furthermore, the part to be repaired is an aircraft door, the reference part is the door frame opening on the fuselage that mates with the door; the hinge axis is the axis of the hinge structure between the door and the fuselage, the locking point mating structure is the locking structure between the door and the door frame opening; and the mating edge is the edge line of the seam between the door and the door frame opening.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention obtains measured data of the parts to be repaired and the reference parts, and constructs target boundaries based on the measured boundaries of the reference parts. It transforms the repair and processing target from a theoretical numerical model to one directly determined by the actual surfaces of both mating parts. Compared with the existing repair and processing methods that use theoretical numerical models as processing targets, it fundamentally eliminates the problem of over-cutting and under-cutting caused by the deviation of the actual surfaces from the theoretical numerical model. The determined repair and processing amount is consistent with the actual repair and processing requirements at the assembly site.

[0018] This invention extracts the hinge axis and locking point mating structure positions of the part to be repaired and the reference part. It solves the assembly pose by using the coincidence of the hinge axis as a constraint and minimizing the positioning error of the locking point mating structure as the objective. The constraint of the coincidence of the hinge axis eliminates the degree of freedom in the hinge direction, so that the part to be repaired is constrained to the actual assembly state determined by the assembly reference such as the hinge and locking point. This is different from the registration method that takes geometric optimization or uniform allowance as the alignment objective. The gap and step difference calculated in this way are the objective distribution under the actual assembly conditions, and the repair amount determined by it is real and effective.

[0019] This invention uses a negative gap margin component as the criterion for material shortage and over-tolerance during the margin field calculation stage, pre-determining that the material removal at this location is irreparable before processing. Within the assembly adjustment range, it uses the redistribution of the fitting margin along the mating edge as a means, and solves the pose increment within the adjustable range to ensure that the gap margin component at each sampling point is not less than zero, thereby eliminating negative margin. This differs from pose adjustment aimed at uniform gap, avoiding the problem of existing methods only discovering irreparability after fitting. If the negative margin still cannot be eliminated within the adjustable range, an over-tolerance alarm is output, realizing the pre-determination and handling of material shortage and over-tolerance before processing.

[0020] This invention transforms the measurement and fitting quantity determination that relies on manual experience into quantitative calculation based on measured point clouds. The fitting quantity is output along the mating edge as decoupled gap allowance components and step difference allowance components, providing a definite and repeatable quantitative input for the digital fitting and fitting of mating parts, thus eliminating the dependence on trial and error based on fitter experience in existing methods. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method for determining the fitting allowance of mating parts based on assembly datum constraints according to the present invention; Figure 2 This is an exemplary schematic diagram of the mating parts and assembly datum provided in an embodiment of the method for determining the fitting allowance of mating parts based on assembly datum constraints of the present invention; Figure 3 This is an exemplary geometric diagram of assembly datum element extraction and constraint registration provided in an embodiment of the method for determining fitting allowance of mating parts based on assembly datum constraints of the present invention; Figure 4 This is an exemplary comparison diagram of registration and alignment targets provided in the embodiment of the method for determining the fitting allowance of mating parts based on assembly datum constraints of the present invention; wherein (a) is the free best fit with geometric optimality as the objective, and (b) is the assembly datum constraint registration of the present invention; Figure 5 This is an exemplary schematic diagram of discrete sampling of mating edges provided in an embodiment of the method for determining the fitting allowance of mating parts based on assembly datum constraints of the present invention; Figure 6This is an exemplary cross-sectional diagram of the fitting allowance definition provided in an embodiment of the method for determining fitting allowance of mating parts based on assembly datum constraints of the present invention; Figure 7 This is an exemplary schematic diagram of the fit allowance distribution along the mating edge provided in an embodiment of the method for determining the fit allowance of mating parts based on assembly datum constraints of the present invention. Figure 8 This is an exemplary schematic diagram of pose re-optimization provided in an embodiment of the method for determining the fitting allowance of mating parts based on assembly datum constraints of the present invention; wherein (a) is the state with material shortage before adjustment, and (b) is the state with non-negative allowance for the entire field after adjustment.

[0022] In the diagram: 1-Part to be repaired; 2-Base component; 3-Hinge; 4-Locking point; 5-Matching edge; 6-Matching surface. Detailed Implementation

[0023] The technical solutions of the invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort are within the scope of the invention.

[0024] In the description of this invention, it should be noted that the terms "above" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience and simplification of 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. Therefore, they should not be construed as limitations on this invention.

[0025] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] like Figure 2As shown, the processing objects of this invention include: a part to be repaired 1, a reference part 2, a hinge 3, a locking point 4, a mating edge 5, and a contact surface 6. In this embodiment, the part to be repaired 1 is a cabin door of a certain type of aircraft, and the reference part 2 is the door frame opening on the fuselage that mates with the cabin door. The cabin door is hinged to the fuselage by two hinges 3 on one side, and locked to the door frame by four locking points 4 on the other side and around the perimeter. The mating edge 5 is the closed edge line of the door and the door frame opening, with a perimeter L≈3200mm. The contact surface 6 is the receiving surface of the inner side of the cabin door overlapping the door frame. After the cabin door and the door frame are assembled, the mating parts must meet the design requirements of the outer surface seam gap g0=2.0mm, gap tolerance ±0.5mm, and the step difference requirement of the outer surface flush h0=0, step difference tolerance ±0.8mm. The cabin door is manufactured with a repair allowance reserved according to the theoretical numerical model, that is, each part of its mating edge has a positive removal amount relative to the theoretical position. The workpiece coordinate system and the surface models of each part have been calibrated. The calibration method will not be described in detail here, as it does not constitute a limitation of this invention.

[0028] like Figure 1 As shown, this invention discloses a method for determining the repair allowance of mating parts based on assembly datum constraints. The mating parts include the part to be repaired 1 and the datum part 2, and include the following steps: S1, Data Acquisition: Obtain the measured data of the part to be repaired 1 and the reference part 2; In this step, a structured light scanner is used to perform a 3D scan of the hatch and door frame opening, with a point spacing of approximately 0.15mm. The scanning range covers the area containing the mating edge 5, hinge 3, locking point 4, and mating surface 6, obtaining the measured point cloud of the part to be repaired and the measured point cloud of the reference part. The reference part 2 remains in its measured state and is not involved in the repair, serving as a fixed reference for subsequent registration and allowance calculation.

[0029] S2, Assembly datum feature extraction: The assembly datum elements are extracted from the measured data of the part to be repaired 1 and the reference part 2 respectively. The assembly datum elements include at least the position of the hinge axis and the locking point mating structure.

[0030] like Figure 3 As shown, in this step, the hinge axis of the reference side is extracted from the measured point cloud of reference component 2. The center of each locking point 4 mating structure And the mating surface 6; extract the corresponding hinge axis of the part to be repaired from the measured point cloud of the part to be repaired 1. With Lock Center ,in , The sequence number of the lock point. This represents the total number of lock points. In this embodiment... .

[0031] The hinge axis is obtained by fitting the measured point cloud of the hinge seat's cylindrical surface. Taking the fitting of the hinge axis on the reference side as an example, let the measured point cloud of the hinge seat be denoted as... The axis starts from a point on it. With unit direction vector This means that the minimum fit is achieved by using the following formula to minimize the sum of the squares of the perpendicular distances from the point to the axis: ; in, This represents the variable values ​​that minimize the objective function on the right, i.e., finding the axis parameter that minimizes the sum of the squared perpendicular distances from each measured point to the axis. and ; The Euclidean norm (magnitude) of a vector. That is, a vector The modulus represents the point. The perpendicular distance to the fitted axis; The first point cloud of the hinge seat One point; , Let be a point on the fitted axis and the unit direction vector, respectively. The values ​​within the square brackets are... In the projection along the axis, the whole term is the perpendicular component from that point to the axis. By fitting the hinge seat point clouds of the component to be repaired (part 1) and the reference part (part 2), the hinge axis of the component to be repaired is obtained. hinge axis with reference side In this embodiment, the number of point clouds on the cylindrical surface of the hinge seat is no less than 200 points, and the fitting accuracy is better than 0.05mm.

[0032] Lock point 4 is the center of the mating structure The center of the lock pin is obtained by fitting the center of the measured point cloud of each lock hole mating surface of the door frame. Fitting the measured point cloud of each door lock pin. The mating surface 6 is obtained by fitting the plane of the measured point cloud of the overlapping area and is used to provide additional constraints.

[0033] S3, inter-part registration with assembly datum constraints: Using the rigid body transformation T of the part to be repaired 1 relative to the reference part 2 as the variable, the coincidence of the hinge axis of the part to be repaired 1 with the hinge axis of the reference part 2 as the constraint, and minimizing the positioning error of the locking point 4 mating structure as the objective, the assembly pose of the part to be repaired 1 relative to the reference part 2 is solved. .

[0034] like Figure 3 and Figure 4As shown, in this step, the assembly pose is solved using the following formula: ; in, The transformation of the rigid body to be determined includes rotation R and translation t; , The first Each lock pin center and lock point center; Indicates to From 1 to Summation, that is, summing the position errors of all locking points; st (subject to) represents the constraint condition, followed by the equality or inequality constraints that the optimization problem must satisfy; constraint This indicates that after the transformation, the hinge axis on the side to be repaired coincides with the hinge axis on the reference side.

[0035] In rigid body transformation Under the influence of point The transformed position is .constraint The degrees of freedom in the hinge direction during rigid body transformation were eliminated, and the remaining degrees of freedom are determined by the positioning error term of locking point 4. In this embodiment, the root mean square of the positioning error of locking point 4 under the assembly pose is approximately 0.3 mm.

[0036] It should be noted that this step differs from the free best fit, which aims to minimize the overall geometric deviation of the mating parts. The latter is solved using the following formula: ; in, The optimal rigid body transformation under the best fit of free; These are the corresponding point pairs to be registered; like Figure 4 As shown in (a), the free best fit makes the gaps at all mating edges tend to be uniform, but the obtained pose is not the actual assembly state of the hatch determined by hinge 3 and locking point 4. Therefore, the allowance calculated based on this cannot reflect the actual repair requirements. Figure 4 As shown in (b), the assembly datum constraint registration of the present invention results in the hatch fitting to the hinge side with unevenly distributed gaps at various points. This uneven distribution is precisely the objective gap of the mating edges in the actual assembly state, and the allowance determined accordingly is consistent with the actual repair requirements. This method changes the alignment target of registration from geometric optimization to assembly datum positioning, which is the premise for determining the repair allowance in the present invention.

[0037] As a preferred implementation, when the assembly reference element in step S2 also includes the mating surface 6, the constraint that the normal direction of the mating surface 6 does not interfere can be included in the above registration model in the form of inequality constraints or penalty functions to further ensure the mating quality of the overlap area between the hatch and the door frame. In specific implementation, a penalty term for the normal interference of the mating surface 6 can be added to the objective function, or the normal gap at each point of the mating surface 6 can be directly limited to not less than zero by inequality constraints. Those skilled in the art can choose an appropriate constraint processing method according to actual engineering needs.

[0038] S4, combined with edge processing: In assembly position Next, determine the actual measured boundary between the actual measured mating edge 5 of the part to be repaired 1 and the corresponding actual measured boundary of the reference part 2, set several sampling points along the mating edge 5, and establish a local reference system at each sampling point to distinguish the gap direction and the step direction.

[0039] like Figure 5 As shown, in this step, The arc length parameter along the mating edge is used in the assembly pose. Below, the actual measured mating edge of the part to be repaired 1 is extracted. The corresponding measured boundary of reference component 2, where For arc length The measured mating edge of the part to be repaired (parameter 1) is used as the parameter. The distance is calculated along the arc length using the basic step size. Discretize the sample and refine it in areas of high curvature. The sampling step size is determined by the following formula: ; in, For the first Each sampling interval; Based on the step size, this embodiment takes ; The curvature encryption feature length is given by the radius of curvature. The sampling interval is halved, and the radius of curvature is much larger. The sampling interval tends to the basic step size, and in this embodiment, it is taken as... ; To match the arc length parameter of side 5 Curvature at that point; curvature The larger the radius of curvature, the more... The smaller the sampling interval The smaller the value, the more accurate the sampling encryption is for areas with high curvature.

[0040] The total number of sampling points is estimated using the following formula: ; in, This represents the number of sampling points; To match the perimeter of the side; To round up; In this embodiment Basic step size For closed mating edges, the number of sampling points increased by curvature encryption is approximately After curvature adaptive encryption, the actual number of sampling points is about 430, with denser sampling at locations with greater curvature, such as the four corners of the hatch.

[0041] At each sampling point At this point, establish the tangential direction according to the following formula. Step direction and the direction of the gap The constructed orthogonal local frame: ; in, To coordinate with the side exist Tangential vector at the location; To coordinate with side 5 at the sampling point The unit tangent at the location; Take the outward normal of the mating surface, i.e., the step difference direction; Depend on and The cross product yields a direction pointing in the gap width direction, i.e., the gap direction. The three form a right-handed orthogonal system.

[0042] This configuration allows the gaps and step differences at each point on the mating edge 5 to be decoupled and measured along their respective directions.

[0043] S5, Calculation of residual field: Based on the measured boundary of reference part 2, the target boundary is constructed according to the theoretical gap and theoretical step difference required by the design. The deviation of the measured boundary of the part to be repaired 1 relative to the target boundary is projected at each sampling point along the gap direction and the step difference direction, respectively, to obtain the repair allowance field distributed along the mating edge 5.

[0044] like Figure 6 and Figure 7 As shown, in this step, the target boundary is determined by the following formula: ; in, The target boundary is the final target contour that the mating edge 5 of the part to be repaired should be fitted to. The measured boundary of reference component 2; , These represent the theoretical clearance and theoretical step difference required by the design, respectively, and are allowed to be design functions that vary along the mating edge 5. In this embodiment, we take... , ; , These are the gap direction and step difference direction at the corresponding sampling points, respectively, where the gap direction n(s) points from the part to be repaired 1 to the reference part 2.

[0045] like Figure 6 As shown, the target boundary is the final position to which the door mating edge 5 should be repaired. That is, the measured boundary of the reference part 2 is first offset along the step difference direction m by the theoretical step difference h0, and then offset along the clearance direction n in the opposite direction (i.e. towards the side of the part to be repaired 1) by the theoretical clearance. The resulting target profile ensures that the distance between the target boundary and the measured boundary of reference piece 2 is exactly the theoretical gap. .

[0046] At each sampling point, the measured boundary point of the component to be repaired 1 is recorded as follows: The target boundary corresponding point is The gap margin component and the step difference margin component are calculated using the following formula: ; in, For the first The gap margin component of each sampling point This indicates that the measured boundary of the part to be repaired 1 exceeds the target boundary, and there is still material that needs to be removed to the target boundary; For the first The step difference residual components at each sampling point.

[0047] The gap margin components and step difference margin components of all sampling points are arranged along the fitting edge 5, forming a fitting margin field: ; in, The fit allowance distribution along the fit edge, i.e., the allowance field; , These are the clearance allowance and the step allowance along the arc length, respectively. The distribution of .

[0048] like Figure 7 As shown, the clearance margin in this embodiment A value between 0.6 and 1.6 mm is considered positive, indicating that material can be removed to the target boundary; step allowance. It is within ±0.2mm. This setting allows the amount to be removed at each point on the mating edge 5 to be directly calculated from the measured surface and assembly position, without relying on manual trial and error.

[0049] S6, Negative Margin Processing and Output: Determine whether there is a negative allowance in the repair allowance field that indicates insufficient material. If not, output the repair allowance field. If it exists, adjust the assembly posture within the adjustable range between the part to be repaired 1 and the reference part 2 to eliminate the negative allowance, and redetermine the repair allowance field based on the adjusted assembly posture. If there is still a negative allowance after adjustment, it is determined to be out of tolerance and an alarm signal is output.

[0050] like Figure 7 and Figure 8 As shown, the condition for determining the validity of the remaining amount in this step is: ; in, This indicates taking the gap margin component among all sampling points. The minimum value of the minimum value is not less than zero, which means that the full field margin is valid, that is, the gap margin component of each sampling point of the matching edge 5 is not less than zero.

[0051] In this embodiment, a sampling point with a negative clearance margin component appears in a certain corner section of the hatch. The minimum value of the clearance margin component among all sampling points is... ;like Figure 8 As shown in (a), the measured edge of the hatch has been recessed into the target boundary. There is insufficient material and it cannot be repaired by removing material. If the gap is repaired according to the current assembly position, it will exceed the tolerance.

[0052] To address this situation, the adjustable amount of the hinge 3 and locking point 4 is adjusted. The assembly pose is further optimized internally, and a pose increment is calculated. This ensures that the gap margin component at each sampling point is not less than zero after further optimization. ; in, This is the pose increment applied to the assembly pose; Indicates the assembly pose Based on the composite application of pose increment ; Indicates the first The gap margin component of each sampling point in the corresponding pose; Symbols indicating universal quantifiers; This indicates that for all sampling points All of these inequalities must hold true; The modulus of the pose increment is measured by the maximum displacement caused by the pose increment at each sampling point on the mating edge, and has the same dimension of length as the adjustable amount Δ. As an adjustable constraint, its limit is given by the adjustable range of the fit structure between hinge 3 and locking point 4. In this embodiment, it is taken as... .

[0053] Adjustable range The adjustable range of hinge 3 and locking point 4 is determined by the following: In this embodiment, hinge 3 has an installation adjustment margin of ±0.5mm along the flight direction, and locking point 4 has a normal adjustment margin of ±0.5mm. Considering all given... =1.0mm. In practical engineering, The specific value depends on structural factors such as the mounting hole allowance of the hinge 3 and locking point 4 mating structure and the adjustable range of the shim. Those skilled in the art can determine it based on the structural design parameters of the specific mating parts.

[0054] The optimized assembly pose is as follows: ; in, This is the optimized assembly pose.

[0055] like Figure 8 As shown in (b), after pose re-optimization, the hatch shifts approximately 0.4 mm towards the side with insufficient material, and the clearance margin at the corner sampling point increases from negative to positive. Meanwhile, the gap margin of the sampling points on the opposite side decreases accordingly and the gap increases. That is, the margin at the material shortage point is obtained by adjusting the position and posture of the material on the opposite side. After optimization, the hatch is more skewed and the gaps are more uneven than before optimization, but the margin of the whole field is not less than zero.

[0056] It should be noted that the pose re-optimization in this step differs in nature from the assembly datum constraint registration in step S3: the assembly pose in step S3 is uniquely determined by the hard constraint of the coincidence of the hinge 3 axis and the positioning error target of the locking point 4, and must not be changed to make the gap uniform; the pose re-optimization in this step only occurs when there is negative margin, and only in adjustable amounts. The internal adjustment is only applied to eliminate single-point material shortage by applying a small positional increment. Its essence is the redistribution of the fitting allowance along the mating edge, which is different from the positional adjustment aimed at making the gap uniform.

[0057] If in adjustable There is no pose increment within the constraint that makes all clearance margin components not less than zero; that is, it is impossible to find a pose increment that satisfies the constraint. And make the gap margin component of all sampling points of If the material shortage cannot be eliminated through repair and position adjustment, an out-of-tolerance alarm will be output.

[0058] In this embodiment, after pose re-optimization, the overall margin of the door mating edge is non-negative, and the output shows the fitting margin distribution along the mating edge. This serves as the basis for generating subsequent repair and fitting trajectories. The entire process is completed under a single measurement and registration. The gaps and step adjustments at each point on the mating edge 5 are uniquely determined by the measured surface under the constraints of the assembly datum. The assembly relationship between the mating surface and hinges 3 and locking points 4 is guaranteed by geometric constraints, and material shortages and deviations are detected before processing. This approach frees the determination of the repair amount of mating parts from dependence on theoretical models and fitter experience, providing quantitative input for the digital fitting and repair of thin-walled mating parts.

[0059] This invention provides a method for determining the fitment allowance of mating parts based on assembly datum constraints. This method can be widely applied to aerospace assembly scenarios such as aircraft doors and frames, covers and frames, and moving and fixed surfaces. It can also be extended to other mechanical assembly fields requiring fitment. Any method that determines the fitment allowance based on the measured point cloud of the mating parts and constrained by the assembly datum falls within the scope of this invention.

[0060] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for determining the repair allowance of mating parts based on assembly datum constraints, wherein the mating parts include the part to be repaired and a datum part, characterized in that, Includes the following steps: S1, Obtain the measured data of the part to be repaired and the measured data of the reference part; S2, extract assembly datum elements from the measured data of the part to be repaired and the reference part respectively, wherein the assembly datum elements include at least the position of the hinge axis and the locking point mating structure; S3, taking the rigid body transformation of the part to be repaired relative to the reference part as the variable, taking the coincidence of the hinge axis of the part to be repaired and the hinge axis of the reference part as the constraint, and taking the minimum positioning error of the locking point fit structure as the objective, solve the assembly pose of the part to be repaired relative to the reference part. S4, under the assembly posture, determine the actual measured mating edge of the part to be repaired and the corresponding actual measured boundary of the reference part, set a number of sampling points along the mating edge, and establish a local reference system at each sampling point to distinguish between the gap direction and the step direction; S5. Based on the measured boundary of the reference component, construct the target boundary according to the theoretical gap and theoretical step difference required by the design. Project the deviation of the measured boundary of the part to be repaired relative to the target boundary at each sampling point along the gap direction and the step difference direction respectively to obtain the repair allowance field distributed along the mating edge. S6, determine whether there is a negative allowance in the repair allowance field that indicates insufficient material. If not, output the repair allowance field. If it exists, adjust the assembly posture within the adjustable range between the part to be repaired and the reference part to eliminate the negative allowance, and redetermine the repair allowance field according to the adjusted assembly posture. If the negative allowance still exists after adjustment, determine that it is out of tolerance and output an alarm signal.

2. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S2, the hinge axis of the part to be repaired and the hinge axis of the reference part are respectively obtained by the measured point cloud of their respective hinge seat cylindrical surface, and the minimum sum of the squares of the vertical distances from each measured point to the axis is fitted.

3. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S2, the assembly reference element further includes a mating surface; in step S3, the constraints that do not interfere with the normal direction at the mating surface are included in the registration in the form of inequality constraints or penalty functions.

4. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S3, the positioning error of the locking point fit structure aims to minimize the sum of the squares of the distances between the center of each locking point fit structure and the center of the corresponding locking pin; the constraint of the coincidence of the hinge axis eliminates the degree of freedom in the hinge direction, and the remaining degree of freedom is determined by the positioning error term of the locking point fit structure.

5. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S4, the local reference system is composed of the tangent of the mating edge at the sampling point, the outward normal of the mating surface, and the direction obtained by the cross product of the two; wherein, the outward normal of the mating surface is the step difference direction, and the direction obtained by the cross product is the gap direction.

6. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S4, when setting sampling points along the mating edge, the sampling interval is adaptively determined according to the curvature of the mating edge, and the sampling interval decreases where the curvature is large.

7. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S5, the deviation of the measured boundary of the part to be repaired relative to the target boundary is projected onto the gap direction to obtain the gap margin component, and projected onto the step difference direction to obtain the step difference margin component. The repair margin field is composed of the gap margin component and the step difference margin component of each sampling point.

8. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S5, the target boundary is obtained by offsetting the measured boundary of the reference component along the gap direction according to the theoretical gap and along the step direction according to the theoretical step difference; the theoretical gap and / or the theoretical step difference is a design function that varies along the mating edge.

9. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, In step S6, adjusting the assembly pose within the adjustable range to eliminate the negative margin specifically involves: calculating a pose increment within the adjustable range such that the gap margin component of each sampling point after adjustment is not less than zero; if there is no pose increment within the adjustable range that makes the gap margin component of each sampling point not less than zero, then it is determined to be out of tolerance; the adjustable range is given by the adjustable range of the hinge and locking point mating structure; adjusting the assembly pose within the adjustable range is a redistribution of the fitting margin along the mating edge, which is different from pose adjustment aimed at making the gap uniform.

10. The method for determining the fitting allowance of mating parts based on assembly datum constraints according to claim 1, characterized in that, The part to be repaired is an aircraft door; the reference part is the door frame opening on the fuselage that mates with the door; the hinge axis is the axis of the hinge structure between the door and the fuselage; the locking point mating structure is the locking structure between the door and the door frame opening; and the mating edge is the edge line of the seam between the door and the door frame opening.

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