Obstacle avoidance method for three-coordinate measurement of helicopter structural component

Abstract

The invention provides an obstacle avoidance method for three-coordinate measurement of a helicopter structural member, and the method comprises the steps: 1, carrying out the classification of the interference conditions of the three-coordinate measurement of the helicopter structural member according to the interference detection conditions in the three-coordinate measurement process of the helicopter structural member; the types of the interference conditions comprise a first type of interference, a second type of interference, a third type of interference, a fourth type of interference and a fifth type of interference; 2, recognizing the three-coordinate measurement interference of the helicopter structural member according to the interference point type, the preorder point type and the subsequent point type; 3, according to the type of the interference condition, obstacle avoidance is carried out on three-coordinate measurement of the helicopter structural part; and step 4, checking the interference obstacle avoidance effect of the helicopter structural member three-coordinate measurement.

Description

Technical Field

[0001] The present application relates to the field of helicopter structural component measurement, and in particular to an obstacle avoidance method for three-coordinate measurement of helicopter structural components. Background Art

[0002] The types of helicopter structural parts are becoming more and more complex, and three-dimensional coordinate measurement is an important means of quality inspection for such parts. The preparation of collision-free three-dimensional coordinate measurement programs is an important technical link in the quality inspection of such parts. However, the existing interference inspection algorithm is difficult to cover all situations, and it is impossible to effectively monitor the overtravel problem of machine tools, and it is also impossible to perform interference inspection on non-test parts such as fixtures. Summary of the invention

[0003] The present application provides an obstacle avoidance method for three-coordinate measurement of helicopter structural parts, which can solve the technical problem of being unable to effectively monitor the overtravel problem of machine tools.

[0004] Technical solution: This application provides an obstacle avoidance method for three-coordinate measurement of helicopter structural parts, the method comprising:

[0005] Step 1: According to the interference inspection during the three-coordinate measurement of helicopter structural parts, the interference conditions of the three-coordinate measurement of helicopter structural parts are classified; the types of interference conditions include the first type of interference, the second type of interference, the third type of interference, the fourth type of interference and the fifth type of interference;

[0006] Step 2: Identify the interference of three-dimensional measurement of helicopter structural parts according to the interference point type, the preceding point type and the succeeding point type;

[0007] Step 3: According to the type of interference, perform obstacle avoidance for the three-dimensional coordinate measurement of the helicopter structure;

[0008] Step 4: Check the interference and obstacle avoidance effect of the three-coordinate measurement of the helicopter structure.

[0009] Specifically, the first type of interference is the interference that occurs when the probe moves into the measurement feature or into the measurement point;

[0010] The second type of interference is the interference generated during the switching of the safety plane;

[0011] The third type of interference is the interference caused by the absence of a safety plane during measurement;

[0012] The fourth type of interference is the interference generated when the probe switches the swing angle;

[0013] The fifth type of interference is the interference that occurs when the third and fourth types of interference are combined and intertwined.

[0014] Specifically, step 3 includes:

[0015] Step 31: If the type of interference situation is the first type of interference, the first type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure;

[0016] Step 32: Obtain interference path point data according to the interference check result;

[0017] Step 33: Obtain the corresponding measurement feature information and change the measurement point planning positioning parameters, and update the feature positioning point and position point;

[0018] Step 34: Perform interference check on the feature measurement path. If interference exists, change the probe number and perform interference check again. Select the probe that does not interfere.

[0019] Step 35: Generate a new path and save it.

[0020] Specifically, step 3 includes:

[0021] Step 31: If the type of interference situation is the second type of interference, the second type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure;

[0022] Step 32: According to the interference check result, obtain the interference path point and the previous path point data;

[0023] Step 33: Obtain the safety plane data where the interference path point is located;

[0024] Step 34: Project the previous path point to the safety plane where the interference point is located to generate the obstacle avoidance point C1;

[0025] Step 35: Determine whether the swing angles of the preceding point and the interference point are the same. If they are different, extend a probe distance along the measurement direction to generate the obstacle avoidance point C2. The ball probe measurement direction is regarded as the normal direction of the safety plane, and the special probe measurement direction is regarded as the swing angle direction corresponding to the probe number here.

[0026] Step 36: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

[0027] Specifically, step 3 includes:

[0028] Step 31: If the type of interference situation is the third type of interference, the third type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure;

[0029] Step 32: According to the interference check result, obtain the interference path point (EP) and the previous path point (LP) data;

[0030] Step 33: Calculate the angle between the measurement directions of the two path points, and match the corresponding obstacle avoidance method according to the angle range;

[0031] Step 34: Determine the probe type. If it is a ball probe, end the optimization. If it is a special probe, use the special probe simplified model to check the interference of the new path. If there is no interference, the obstacle avoidance ends. If there is interference, the interference type of the new path is determined to be the first type of interference, and the special probe first type of interference obstacle avoidance method is used to continue obstacle avoidance.

[0032] Specifically, if the angle between the two measuring directions is less than 90°, step 33 specifically includes:

[0033] Step 33-1-1: Construct the preceding plane and the interference plane according to the coordinates of the preceding point and the interference point and the measurement direction. Assume that the coordinates of the preceding point are (x1, y1, z1), and the measurement direction vector, i.e., the normal vector of the surface, is (A1, B1, C1). Then, the equation of the preceding plane is A1(x-x1)+B1(y-y1)+C1(z-z1)-0. The construction of the interference plane is similar, and the equation is A2(x-x2)+B2(y-y2)+C2(z-z2)=0.

[0034] Step 33-1-2: Project the previous point onto the interference plane to generate the obstacle avoidance point C. The projection method is as follows: First, calculate the intersection line I1 of the previous plane and the interference plane, and its equation is

[0035]

[0036] Then, the projection I1 of the line LP-EP connecting the previous point and the interference point on the interference plane is obtained. The intersection of I1 and I is the obstacle avoidance point C.

[0037] Step 33-1-3: Insert the obstacle avoidance point C between the previous point and the interference point, and measure the path LP-C-EP;

[0038] Step 33-1-4: Check the interference of the path LP-C-EP. If there is no interference, the obstacle avoidance is completed and the next step is entered. Otherwise, the next step is entered.

[0039] Step 33-1-5: The previous interference point is translated in the opposite direction of the measurement direction for a certain distance to generate points D1 and E1;

[0040] Step 33-1-6: Reconstruct the preceding plane and the interference plane based on D1 and E1, the construction method is the same as step 1);

[0041] Step 33-1-7: Project the previous point along the normal direction of the interference plane to the interference plane to generate E2, and project the interference point along the normal direction of the previous plane to the interference plane to generate D2. The projection method is the same as 2);

[0042] Step 33-1-8: Generate the path LP-D1-D2-EP and the path LP-E2-E1-EP;

[0043] Step 33-1-9: Determine the interference between the two paths. The determination method is detailed below. In this step, the interference check uses a simplified model with a ball probe;

[0044] Step 33-1-10: If both paths interfere, repeat steps 33-1-5 to 33-1-9. Otherwise, select the shortest non-interfering path.

[0045] Step 33-1-11: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

[0046] Specifically, if the angle between the two measuring directions is greater than 90°, step 33 specifically includes:

[0047] Step 33-2-1: Raise the previous point and the interference point to a certain height along the positive direction of the Z axis and the positive direction of the X axis respectively, and generate quasi-obstacle avoidance points A1, B1 and A2, B2;

[0048] Step 33-2-2: Determine the interference between the paths LP-A1-B1-EP and LP-A2-EP-B2 respectively. The determination method is detailed below. In this step, the interference check uses a simplified model with a ball probe.

[0049] Step 33-2-3: If the two paths do not interfere, select the shorter path as the obstacle avoidance path; if only one path interferes, select the non-interfering path as the obstacle avoidance path; if both paths interfere, increase the obstacle avoidance height, update the quasi-obstacle avoidance points A1, B1, A2, B2, and repeat the above process until the obstacle avoidance path is generated;

[0050] Step 33-2-4: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

[0051] Specifically, if the type of interference situation is the fourth type of interference, step 3 specifically includes:

[0052] Step 31: According to the interference check result, obtain the data coordinates (x1, y1, z1) and (x2, y2, z2) of the previous path point and the interference path point;

[0053] Step 32: along the angular direction of the interference point (EP) A and the measurement direction, according to the above method, generate quasi-obstacle avoidance points A and B at the previous point (LP), and save the coordinates of point B;

[0054] Step 33: Calculate the position C of the probe after switching the swing angle. For Rational DMIS three-dimensional coordinate measuring machine, the machine tool coordinate system follows the right-hand rule. The positive direction of the probe angle A is raised along the positive direction of the Y axis, that is, it rotates counterclockwise around the X axis, and the positive direction of the angle B is counterclockwise around the Z axis. The process of solving the position point C is to perform a rotation transformation on the current probe coordinates around the rotation center.

[0055] Step 34: Determine the interference of the path LP-BC-EP, and do not include the interference check in the special probe BC segment;

[0056] Step 35: If all segments do not interfere, save the coordinates of the quasi-obstacle avoidance point B; if the path LP-B interferes, translate the previous point along the measurement direction, and repeat Step 2-5 until the path does not interfere; if the path BC or C-EP interferes, translate the quasi-obstacle avoidance point B along the measurement direction of the interference point, and repeat Step 3-5 until the path does not interfere;

[0057] Step 36: Insert the quasi-obstacle avoidance point B between the previous point and the interference point, generate a new measurement path and save it.

[0058] Specifically, step 33 includes:

[0059] Step 331: Obtain the three normal directions of the machine tool coordinate system, calculate the rotation center position according to the probe parameters and the AB angle data of the previous point, and construct the probe coordinate system with the rotation center as the origin and the three normal directions of the machine tool coordinate system;

[0060] Step 332: convert point B to the probe coordinate system through coordinate system transformation to obtain point B1;

[0061] Step 333: Restore the probe coordinates to the state of A=0, B=0, and obtain point B2 (0, 0, -D), where xyz is the coordinate value of point B1;

[0062] Step 334: Calculate the coordinates of point C′. The coordinate measuring machine probe first rotates angle A and then angle B. The calculation method is as follows:

[0063]

[0064] Substituting point B2 into the above two equations, we get Where a and b are the AB swing angle values ​​of the interference point respectively. If it is a special probe, it is the AB swing angle value corresponding to the probe used at the interference point;

[0065] Step 335: Convert point C′ to the measurement coordinate system through coordinate system transformation to obtain point C.

[0066] Specifically, if the type of interference situation is the fifth type of interference, step 3 specifically includes:

[0067] Step 31: According to the interference check result, obtain the interference path point (EP) and the previous path point (LP) data;

[0068] Step 32: Perform interference check on the path LP-EP to determine whether there is third-type interference. If so, call the third-type problem obstacle avoidance algorithm and insert the obstacle avoidance point into the measurement path to generate a new path.

[0069] Step 33: If the obstacle avoidance algorithm for the third type of problem has been called, the last obstacle avoidance point data is extracted, otherwise the previous point data is extracted and marked as point TestPoint;

[0070] Step 34: According to the method above, calculate the probe coordinate C after the swing angle changes based on TestPoint, and detect the path TestPoint-C-EP. The special probe detects the two paths TestPoint-C and C-EP. If there is interference, call the fourth type of obstacle avoidance algorithm, insert the obstacle avoidance point into the measurement path, and generate a new path.

[0071] Step 35: Save the optimized path.

[0072] In summary, the present invention provides an obstacle avoidance method for three-coordinate measurement of helicopter structural parts. By fully studying the collision scenarios of helicopter structural parts measurement, the interference situations of three-coordinate measurement of helicopter structural parts are classified, and an obstacle avoidance method is proposed for each interference situation. This can realize the generation of collision-free measurement paths in typical three-coordinate measurement scenarios of helicopter structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 The first type of interference schematic diagram provided by this application;

[0074] Figure 2 A schematic diagram of the second type of interference provided for this application;

[0075] Figure 3 A schematic diagram of the third type of interference provided for this application;

[0076] Figure 4 A schematic diagram of the fourth type of interference provided for this application;

[0077] Figure 5 Schematic diagram of the first type of interference obstacle avoidance process of the special probe provided in this application;

[0078] Figure 6 A schematic diagram of the second type of interference obstacle avoidance process provided for this application;

[0079] Figure 7 A schematic diagram of an example of the second type of interference obstacle avoidance test provided in this application;

[0080] Figure 8 A schematic diagram of the third type of interference obstacle avoidance process provided for this application;

[0081] Fig. 9 A schematic diagram of a solution to the third type of interference situation provided in this application;

[0082] Fig.10A schematic diagram of the obstacle avoidance process for the third type of interference provided by this application;

[0083] Fig.11 Schematic diagram of the solution to the third type of interference situation 2 provided in this application;

[0084] Fig.12 A schematic diagram of the obstacle avoidance process for the third type of interference situation 2 provided in this application;

[0085] Fig.13 A schematic diagram of an example of the third type of interference obstacle avoidance test provided in this application;

[0086] Fig.14 A schematic diagram of the fourth type of interference obstacle avoidance process provided for this application;

[0087] Fig.15 Schematic diagram of the fourth type of interference obstacle avoidance method provided by this application;

[0088] Fig.16 A schematic diagram of the fifth type of interference obstacle avoidance process provided for this application;

[0089] Fig.17 Schematic diagram of the fourth and fifth types of interference obstacle avoidance test examples provided in this application;

[0090] Fig.18 A schematic diagram of the measurement path interference judgment process provided for this application;

[0091] Fig.19 The scanning body provided by the present application is moved by the probe. DETAILED DESCRIPTION

[0092] Based on a thorough study of the collision scenarios of helicopter structural parts measurement, the present invention proposes five types of obstacle avoidance models to solve the obstacle avoidance problem of helicopter structural parts measurement in most cases.

[0093] The present invention provides an obstacle avoidance method for three-coordinate measurement of helicopter structural parts, comprising:

[0094] Step 1: Classify the interference conditions of helicopter structural parts in three-coordinate measurement according to the interference inspection conditions during the three-coordinate measurement of helicopter structural parts;

[0095] Specifically, the types of interference situations include first-type interference, second-type interference, third-type interference, fourth-type interference, and fifth-type interference;

[0096] (1) The first type of interference occurs when the probe moves into the measurement feature or into the measurement point.

[0097] like Figure 1As shown in the figure, the first type of interference occurs when the probe enters the measurement feature or enters the measurement point. It is usually caused by unreasonable measurement parameter settings, such as positioning parameters that are too small, or the probe length is not enough to meet the measurement point range. Therefore, you only need to adjust the measurement parameters or replace the probe.

[0098] For ball probes, according to the inspection characteristics of each part cluster, the measurement parameters of each part cluster at each processing stage are collected into the inspection rule library to reduce the occurrence of such interference problems. For special probes, the first type of interference is mostly caused by the existence of multiple reachable probes but unreasonable selection. If interference still exists after changing the measurement parameters once, the probe number needs to be changed.

[0099] (2) The second type of interference is the interference generated during the switching of safety planes.

[0100] like Figure 2 As shown in the figure, the second type of interference occurs during the switching of safety planes. If there are multiple safety planes during measurement, after the measurement feature of the previous safety plane is completed, it is necessary to move to the next safety plane, and interference may occur during this process. Path point A is the last safety point of safety plane one, and path point B is the first safety point of safety plane two. When the probe is completed in measuring safety plane one, it will move from path point A to path point B, and interference will occur at this time.

[0101] The present invention uses the projection point insertion method to generate obstacle avoidance points. For the ball probe, if the swing angles of points AB are consistent, path point A is projected onto safety plane 2 to generate obstacle avoidance point C1, and the probe will move along A-C1-B to avoid collision; if the swing angles of AB are inconsistent, it is necessary to use C1 as the origin and extend a probe length outward along the normal of safety plane 2 to generate obstacle avoidance point C2, and the probe moves along A-C1-C2-B. For special probes, if the probe numbers used for path point A and path point B are inconsistent, it is necessary to use C1 as the origin and extend a probe length outward along the probe direction at B to generate obstacle avoidance point C2, and the special probe moves along A-C1-C2-B.

[0102] (3) The third type of interference is the interference caused by the absence of a safety plane during measurement.

[0103] like Figure 3 As shown in the figure, when there is no safety plane in a certain measurement, the third type of interference may occur when switching the measurement features. Path point A is the last positioning point of measuring feature one, and path point A1 is the corresponding position point; path point B is the first positioning point of measuring feature two, and path point B1 is the corresponding position point. When switching from feature one to feature two, the probe moves along A-A1-B1-B, and interference occurs between A1-B1. Therefore, it is necessary to insert an obstacle avoidance point between A1-B1 to avoid collision. The third type of interference optimization method is detailed below.

[0104] (4) The fourth type of interference is the interference generated when the probe switches its swing angle.

[0105] like Figure 4 As shown in the figure, the fourth type of interference occurs when the probe switches the swing angle. The three-dimensional coordinate measuring machine follows the principle of swing angle first and then movement. If the swing angles of path point A and path point C are different, when the probe moves from A to C, the swing angle is switched at path point A first, and the probe position changes from A to B, that is, the probe moves along ABC, and the interference occurs between AB. In the traditional three-dimensional coordinate programming mode, the fourth type of interference is difficult to effectively avoid in the path planning stage, and it is not easy to find in the simulation stage. It is often exposed in the test stage. Therefore, experienced inspectors will preset a path point away from the test piece before switching the swing angle to reduce the probability of the fourth type of interference, but it increases the measurement time.

[0106] (5) The fifth type of interference is the interference that occurs when the third and fourth types of interference are combined and intertwined.

[0107] In the actual measurement process, the fourth type of interference often occurs at the same time as the third type of interference, or after avoiding the fourth type of interference, the third type of interference occurs at the same position. The present invention refers to this interference situation where the third and fourth types of interference are intertwined as the fifth type of interference. If this type of interference problem is only based on measurement simulation for interference inspection and obstacle avoidance plan formulation, multiple simulations are required and unnecessary obstacle avoidance costs are easily increased. The fourth type of interference optimization method will be supplemented and this type of interference optimization method will be further explained later.

[0108] Step 2: Identify the interference of three-dimensional measurement of helicopter structural parts according to the interference point type, the preceding point type and the succeeding point type;

[0109] The present invention simulates the three-dimensional coordinate measurement process based on the simulation engine of Vericut, and uses its report interface to obtain the VERICUT simulation report, obtain interference data, identify the interference point data, the types of preceding points and succeeding points, and make interference type judgment according to the following table.

[0110] Among them, the preceding point type is the point numbered before the current point position of a measurement path arranged in sequence from a sequence of points; the succeeding point type is the point numbered after the current point position of a measurement path arranged in sequence from a sequence of points.

[0111] Table 1 Criteria for judging interference types in three-dimensional coordinate measurement of helicopter structural parts

[0112]

[0113]

[0114] Step 3: According to the type of interference, avoid obstacles in the three-dimensional measurement of helicopter structural parts.

[0115] Step 4: Check the interference and obstacle avoidance effect of the three-coordinate measurement of the helicopter structure.

[0116] Specifically, step 4 includes:

[0117] Step 41: Get the current part pointer.

[0118] More specifically, the path interface of the current feature is established through the TTRS pointer of the current feature; the path of the current object in the CATIA feature tree is obtained through the path interface, and the part interface to which the current object belongs is obtained based on the path.

[0119] Step 42: Get the geometric feature set of the current part.

[0120] More specifically, the entity feature interface of the current part is retrieved from the part interface; the entity feature interface is traversed to obtain all geometric features under the current part.

[0121] Step 43: Topology analysis and acquisition of surface topology units.

[0122] More specifically, the current geometric feature set is traversed to create each geometric feature management interface; the geometric feature management interface set is traversed to obtain the topological structure of each feature; all topological structures are traversed to perform topological analysis to obtain the surface unit.

[0123] Step 44: Interference check.

[0124] More specifically, a geometric container of the path to be detected is created and parameterized with the topological unit; the parameterized surfaces of all the paths to be detected are traversed and intersected with the topological units in sequence. If there is an intersection, it is judged as interference, otherwise there is no interference.

[0125] Embodiment 1

[0126] This embodiment of the application takes the interference situation of the first type as an example to explain step 3 in detail. Step 3 specifically includes:

[0127] Step 31: If the type of interference situation is the first type of interference, the first type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure;

[0128] Among them, the first type of interference obstacle avoidance method, based on the above discussion of the first type of interference problem, it can be seen that the existence of the inspection rule library greatly reduces the probability of the first type of interference of the ball probe. The path planning mode of the present invention is based on the feature unit, and the adjustment of the first type of interference of the ball probe is extremely convenient. Therefore, the present invention only designs the first type of interference obstacle avoidance algorithm for special probes. The process is as follows Figure 5As shown, the steps are as follows.

[0129] Step 32: Obtain interference path point data according to the interference check result;

[0130] Step 33: Obtain the corresponding measurement feature information and change the measurement point planning positioning parameters, and update the feature positioning point and position point;

[0131] Step 34: Perform interference check on the feature measurement path. If interference exists, change the probe number and perform interference check again. Select the probe that does not interfere.

[0132] Step 35: Generate a new path and save it.

[0133] Embodiment 2

[0134] This embodiment of the application takes the interference situation of the second type as an example to explain step 3 in detail. Figure 6 As shown, step 3 specifically includes:

[0135] Step 31: If the type of interference situation is the second type of interference, the second type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure.

[0136] Step 32: According to the interference check result, obtain the interference path point and the previous path point data;

[0137] Step 33: Obtain the safety plane data where the interference path point is located;

[0138] Step 34: Project the previous path point to the safety plane where the interference point is located to generate the obstacle avoidance point C1;

[0139] Step 35: Determine whether the swing angles of the preceding point and the interference point are the same. If they are different, extend a probe distance along the measurement direction to generate the obstacle avoidance point C2. The ball probe measurement direction is regarded as the normal direction of the safety plane, and the special probe measurement direction is regarded as the swing angle direction corresponding to the probe number here.

[0140] Step 36: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

[0141] It should be noted that the second type of interference obstacle avoidance method was tested on a small aluminum alloy structural model, and the results are as follows: Figure 7 As shown in the figure, the obstacle avoidance path pointed by the arrow is an interference-free path, which verifies the feasibility of the method.

[0142] Embodiment 3

[0143] This embodiment of the application takes the interference situation of the third type as an example to explain step 3 in detail. Figure 8 As shown, step 3 specifically includes:

[0144] Step 31: If the type of interference situation is the third type of interference, the third type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure;

[0145] Step 32: According to the interference check result, obtain the interference path point (EP) and the previous path point (LP) data;

[0146] Step 33: Calculate the angle between the measurement directions of the two path points, and match the corresponding obstacle avoidance method according to the angle range;

[0147] Specifically, step 33 includes: if the angle between the two-point measurement directions is less than 90°, executing step 33-1-1; if the angle between the two-point measurement directions is greater than 90°, executing step 33-2-1;

[0148] It should be noted that if the angle between the measurement directions of two points is less than 90°, the feature adjacency is divided into "convex adjacency" and "concave adjacency", such as Fig. 9 As shown in Figure 2, the obstacle avoidance process is as follows: Fig.10 shown.

[0149] Step 33-1-1: Construct the preceding plane and the interference plane according to the coordinates of the preceding point and the interference point and the measurement direction. Assume that the coordinates of the preceding point are (x1, y1, z1), and the measurement direction vector, i.e., the normal vector of the surface is (A1, B1, C1). Then the equation of the preceding plane is A1(x-x1)+B1(y-y1)+C1(z-z1)=0. The construction of the interference plane is similar, and the equation is A2(x-x2)+B2(y-y2)+C2(z-z2)=0.

[0150] Step 33-1-2: Project the previous point onto the interference plane to generate the obstacle avoidance point C. The projection method is as follows: First, calculate the intersection line I1 of the previous plane and the interference plane, and its equation is

[0151]

[0152] Then, the projection I1 of the line LP-EP connecting the previous point and the interference point on the interference plane is obtained. The intersection of I1 and I is the obstacle avoidance point C.

[0153] Step 33-1-3: Insert the obstacle avoidance point C between the previous point and the interference point, and measure the path LP-C-EP;

[0154] Step 33-1-4: Check the interference of the path LP-C-EP. If there is no interference, the obstacle avoidance is completed and the next step is entered. Otherwise, the next step is entered.

[0155] Step 33-1-5: The previous interference point is translated in the opposite direction of the measurement direction for a certain distance to generate points D1 and E1;

[0156] Step 33-1-6: Reconstruct the preceding plane and the interference plane based on D1 and E1, the construction method is the same as step 1);

[0157] Step 33-1-7: Project the previous point along the normal direction of the interference plane to the interference plane to generate E2, and project the interference point along the normal direction of the previous plane to the interference plane to generate D2. The projection method is the same as 2);

[0158] Step 33-1-8: Generate the path LP-D1-D2-EP and the path LP-E2-E1-EP;

[0159] Step 33-1-9: Determine the interference between the two paths. The determination method is detailed below. In this step, the interference check uses a simplified model with a ball probe;

[0160] Step 33-1-10: If both paths interfere, repeat steps 33-1-5 to 33-1-9. Otherwise, select the shortest non-interfering path.

[0161] Step 33-1-11: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

[0162] It should be noted that if the angle between the two measurement directions is greater than 90°, the obstacle avoidance method is as follows: Fig.11 As shown. Thanks to the characteristics of Rational DMIS three-dimensional coordinate measuring machine, the first and second normal directions of the measurement coordinate system, namely the positive direction of the Z axis and the positive direction of the X axis, always point away from the test piece. Therefore, the second two directions can be used as obstacle avoidance directions to guide the generation of obstacle avoidance points. Fig.12 shown.

[0163] Step 33-2-1: Raise the previous point and the interference point to a certain height along the positive direction of the Z axis and the positive direction of the X axis respectively, and generate quasi-obstacle avoidance points A1, B1 and A2, B2;

[0164] Step 33-2-2: Determine the interference between the paths LP-A1-B1-EP and LP-A2-EP-B2 respectively. The determination method is detailed below. In this step, the interference check uses a simplified model with a ball probe.

[0165] Step 33-2-3: If the two paths do not interfere, select the shorter path as the obstacle avoidance path; if only one path interferes, select the non-interfering path as the obstacle avoidance path; if both paths interfere, increase the obstacle avoidance height, update the quasi-obstacle avoidance points A1, B1, A2, B2, and repeat the above process until the obstacle avoidance path is generated;

[0166] Step 33-2-4: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

[0167] Step 34: Determine the probe type. If it is a ball probe, the optimization ends. If it is a special probe, the special probe simplified model needs to be used to check the interference of the new path. If there is no interference, the obstacle avoidance ends. If there is interference, the interference type of the new path is determined to be the first type of interference, and the first type of interference obstacle avoidance method of the special probe can be used to continue the obstacle avoidance.

[0168] The algorithm was tested on a small aluminum alloy structural model. The results are as follows Fig.13 As shown in the figure, the path pointed by the arrow is an interference-free path, which verifies the feasibility of the method.

[0169] Embodiment 4

[0170] In the embodiment of the present application, the fourth type of interference is taken as an example to explain step 3 in detail.

[0171] From the analysis of the fourth type of interference problem, it can be seen that the swing angle switching of the ball probe follows the principle of changing angle A first and then angle B. Therefore, before switching the swing angle, the path point A is raised along the direction of angle A of the path point C.

[0172] H1 gets point A. If the probe direction is inconsistent with the swing angle direction at C after changing the A angle, then H2 is raised along the C measurement direction at A′ to get the path point A1; otherwise, A is A1. The calculation method of the raised distance is as follows:

[0173]

[0174]

[0175] Where l is the distance from the probe to its rotation center, α and β are the differences between the angles A and B at points A and C, respectively. The ball probe moves along A-A1-B1-C to avoid collision. When the swing angle of the special probe changes, the probe posture does not change, but the moving center is changed to the center of the probe with the corresponding number. Therefore, there is no path A1-B1, but it moves along A-A1 and then moves along B1-C.

[0176] like Fig.14 As shown, step 3 specifically includes:

[0177] Step 31: If the type of interference situation is the fourth type of interference, then according to the interference check result, the data coordinates (x1, y1, z1) and (x2, y2, z2) of the preceding path point and the interference path point are obtained;

[0178] Step 32: Along the angular direction of the interference point (EP) A and the measurement direction, according to the above method, generate quasi-obstacle avoidance points A and B at the previous point (LP), and save the coordinates of point B, such as Fig.15As shown in the figure, the specific algorithm is as follows: Since the ball probe swing angle switching follows the principle of changing angle A first and then angle B, before switching the swing angle, the previous point is raised by H1 along the angle A direction of the interference point to obtain point A. If the probe direction is inconsistent with the swing angle direction at point C after changing angle A, then H1 is raised along the measurement direction of C at point A to obtain path point B; otherwise, A is B. The lifting distance calculation method is as follows:

[0179] H1=(1-cosα)×l

[0180] H2=(1-cosβ)×l

[0181] Where l is the distance from the probe to its rotation center, and α.β are the angle differences between the previous point and the interference point A and B respectively. The ball probe moves along LP-BC-EP to avoid collision. When the swing angle of the special probe changes, the probe posture does not change, but the moving center is changed to the center of the probe with the corresponding number. Therefore, there is no path BC, but it moves along LP-B and then moves along C-EP;

[0182] Step 33: Calculate the position C of the probe after switching the swing angle. For Rational DMIS three-dimensional coordinate measuring machine, the machine tool coordinate system follows the right-hand rule. The positive direction of the probe angle A is raised along the positive direction of the Y axis, that is, it rotates counterclockwise around the X axis, and the positive direction of the angle B is counterclockwise around the Z axis. The process of solving the position point C is to perform a rotation transformation on the current probe coordinates around the rotation center.

[0183] Specifically, step 33 includes:

[0184] Step 331: Obtain the three normal directions of the machine tool coordinate system, calculate the rotation center position according to the probe parameters and the AB angle data of the previous point, and construct the probe coordinate system with the rotation center as the origin and the three normal directions of the machine tool coordinate system;

[0185] Step 332: convert point B to the probe coordinate system through coordinate system transformation to obtain point B1;

[0186] Step 333: Restore the probe coordinates to the state of A=0, B=0, and obtain point B2 (0, 0, -D), where xyz is the coordinate value of point B1;

[0187] Step 334: Calculate the coordinates of point C′. The coordinate measuring machine probe first rotates angle A and then angle B. The calculation method is as follows:

[0188]

[0189] Substituting point B2 into the above two equations, we can get the point Where a and b are the AB swing angle values ​​of the interference point respectively. If it is a special probe, it is the AB swing angle value corresponding to the probe used at the interference point;

[0190] Step 335: Convert point C′ to the measurement coordinate system through coordinate system transformation to obtain point C.

[0191] Step 34: Determine the interference of the path LP-BC-EP. The determination method is detailed below. The special probe BC segment is not included in the interference check.

[0192] Step 35: If all segments do not interfere, save the coordinates of the quasi-obstacle avoidance point B; if the path LP-B interferes, translate the previous point along the measurement direction, and repeat Step 2-5 until the path does not interfere; if the path BC or C-EP interferes, translate the quasi-obstacle avoidance point B along the measurement direction of the interference point, and repeat Step 3-5 until the path does not interfere;

[0193] Step 36: Insert the quasi-obstacle avoidance point B between the previous point and the interference point, generate a new measurement path and save it.

[0194] Embodiment 5

[0195] In the embodiment of the present application, the fifth type of interference is taken as an example to explain step 3 in detail.

[0196] It should be noted that, based on the discussion of the fifth type of interference obstacle avoidance method, the present invention designs an obstacle avoidance algorithm for the fifth type of interference problem. The above-mentioned fourth type of interference problem obstacle avoidance algorithm covers the interference check during the probe switching swing angle process. Therefore, after the fourth type of interference obstacle avoidance is implemented using this method, the third type of interference will not occur at the same position. Therefore, the fifth type of interference problem obstacle avoidance method is essentially a call to the third and fourth types of interference problem obstacle avoidance methods.

[0197] like Fig.16 As shown, step 3 specifically includes:

[0198] Step 31: If the type of interference situation is the fifth type of interference, then according to the interference check result, obtain the interference path point (EP) and the previous path point (LP) data;

[0199] Step 32: Perform interference check on the path LP-EP to determine whether there is third-type interference. If so, call the third-type problem obstacle avoidance algorithm and insert the obstacle avoidance point into the measurement path to generate a new path.

[0200] Step 33: If the obstacle avoidance algorithm for the third type of problem has been called, the last obstacle avoidance point data is extracted, otherwise the previous point data is extracted and marked as point TestPoint;

[0201] Step 34: According to the method above, calculate the probe coordinate C after the swing angle changes based on TestPoint, and detect the path TestPoint-C-EP. The special probe detects the two paths TestPoint-C and C-EP. If there is interference, call the fourth type of obstacle avoidance algorithm, insert the obstacle avoidance point into the measurement path, and generate a new path.

[0202] Step 35: Save the optimized path.

[0203] The algorithm was tested on a small aluminum alloy structural model, and the fourth and fifth types of interference obstacle avoidance algorithms were tested at the same time. The results are as follows Fig.17 As shown in the figure, the obstacle avoidance path pointed by the arrow is an interference-free path, which verifies the feasibility of the method.

[0204] Normally, the probe of a CMM is closer to the part to be measured than the spindle of a machine tool. If a collision occurs during the measurement process, the probe will collide with the part to be measured first. In the above interference judgment process, the path to be measured is actually divided into several detection units. Each detection unit is composed of two path points and the path between them. During the movement, the posture of the probe does not change. Therefore, the parameterized surface of the path to be measured can be obtained as follows: Fig.19 The scanning volume shown is generated. The probe scanning volume can be regarded as several four-pole columns, which are adjusted according to the swing angle.

[0205] In summary, the present invention provides an obstacle avoidance method for three-coordinate measurement of helicopter structural parts. By fully studying the collision scenarios of helicopter structural parts measurement, the interference situations of three-coordinate measurement of helicopter structural parts are classified, and an obstacle avoidance method is proposed for each interference situation. This can realize the generation of collision-free measurement paths in typical three-coordinate measurement scenarios of helicopter structural parts.

Claims

1. An obstacle avoidance method for three-coordinate measurement of helicopter structural parts, characterized in that: Methods include: Step 1: According to the interference inspection during the three-coordinate measurement of helicopter structural parts, the interference conditions of the three-coordinate measurement of helicopter structural parts are classified; the types of interference conditions include the first type of interference, the second type of interference, the third type of interference, the fourth type of interference and the fifth type of interference; Step 2: Identify the interference of three-dimensional measurement of helicopter structural parts according to the interference point type, the preceding point type and the succeeding point type; Step 3: According to the type of interference, perform obstacle avoidance for the three-dimensional coordinate measurement of the helicopter structure; Step 4: Check the interference and obstacle avoidance effect of the three-coordinate measurement of the helicopter structure.

2. The obstacle avoidance method according to claim 1, characterized in that: The first type of interference is the interference that occurs when the probe moves into the measurement feature or into the measurement point; The second type of interference is the interference generated during the switching of the safety plane; The third type of interference is the interference caused by the absence of a safety plane during measurement; The fourth type of interference is the interference generated when the probe switches the swing angle; The fifth type of interference is the interference that occurs when the third and fourth types of interference are combined and intertwined.

3. The obstacle avoidance method according to claim 1, characterized in that: Step 3 specifically includes: Step 31: If the type of interference situation is the first type of interference, the first type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure; Step 32: Obtain interference path point data according to the interference check result; Step 33: Obtain the corresponding measurement feature information and change the measurement point planning positioning parameters, and update the feature positioning point and position point; Step 34: Perform interference check on the feature measurement path. If interference exists, change the probe number and perform interference check again. Select the probe that does not interfere. Step 35: Generate a new path and save it.

4. The obstacle avoidance method according to claim 1, characterized in that: Step 3 specifically includes: Step 31: If the type of interference situation is the second type of interference, the second type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure; Step 32: According to the interference check result, obtain the interference path point and the previous path point data; Step 33: Obtain the safety plane data where the interference path point is located; Step 34: Project the previous path point to the safety plane where the interference point is located to generate the obstacle avoidance point C1; Step 35: Determine whether the swing angles of the preceding point and the interference point are the same. If they are different, extend a probe distance along the measurement direction to generate the obstacle avoidance point C2. The ball probe measurement direction is regarded as the normal direction of the safety plane, and the special probe measurement direction is regarded as the swing angle direction corresponding to the probe number here. Step 36: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

5. The obstacle avoidance method according to claim 1, characterized in that: Step 3 specifically includes: Step 31: If the type of interference situation is the third type of interference, the third type of interference obstacle avoidance method is used to avoid obstacles in the three-coordinate measurement of the helicopter structure; Step 32: According to the interference check result, obtain the interference path point (EP) and the previous path point (LP) data; Step 33: Calculate the angle between the measurement directions of the two path points, and match the corresponding obstacle avoidance method according to the angle range; Step 34: Determine the probe type. If it is a ball probe, end the optimization. If it is a special probe, use the special probe simplified model to check the interference of the new path. If there is no interference, the obstacle avoidance ends. If there is interference, the interference type of the new path is determined to be the first type of interference, and the special probe first type of interference obstacle avoidance method is used to continue obstacle avoidance.

6. The obstacle avoidance method according to claim 5, characterized in that: If the angle between the two measuring directions is less than 90°, step 33 specifically includes: Step 33-1-1: Construct the preceding plane and the interference plane according to the coordinates of the preceding point and the interference point and the measurement direction. Assume that the coordinates of the preceding point are (x1, y1, x1), and the measurement direction vector, i.e., the normal vector of the surface, is (A1, B1, C1). Then the equation of the preceding plane is A1(x-x1)+B1(y-y1)+c1(z-z1)=0. The construction of the interference plane is similar, and the equation is A2(x-x2)+B2(y-y2)+C2(z-z2)=0. Step 33-1-2: Project the previous point onto the interference plane to generate the obstacle avoidance point C. The projection method is as follows: First, calculate the intersection line l1 of the previous plane and the interference plane, and its equation is Then, the projection of the line LP-EP connecting the preceding point and the interference point on the interference plane is obtained The intersection of l1 and l is the obstacle avoidance point C; Step 33-1-3: Insert the obstacle avoidance point C between the previous point and the interference point, and measure the path LP-C-EP; Step 33-1-4: Check the interference of the path LP-C-EP. If there is no interference, the obstacle avoidance is completed and the next step is entered. Otherwise, the next step is entered. Step 33-1-5: The previous interference point is translated in the opposite direction of the measurement direction for a certain distance to generate points D1 and E1; Step 33-1-6: Reconstruct the preceding plane and the interference plane based on D1 and E1, the construction method is the same as step 1); Step 33-1-7: Project the previous point along the normal direction of the interference plane to the interference plane to generate E2, and project the interference point along the normal direction of the previous plane to the interference plane to generate D2. The projection method is the same as 2); Step 33-1-8: Generate the path LP-D1-D2-EP and the path LP-E2-E1-EP; Step 33-1-9: Determine the interference between the two paths. The determination method is detailed below. In this step, the interference check uses a simplified model with a ball probe; Step 33-1-10: If both paths interfere, repeat steps 33-1-5 to 33-1-9. Otherwise, select the shortest non-interfering path. Step 33-1-11: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

7. The obstacle avoidance method according to claim 5, characterized in that: If the angle between the two measuring directions is greater than 90°, step 33 specifically includes: Step 33-2-1: Raise the previous point and the interference point to a certain height along the positive direction of the Z axis and the positive direction of the X axis respectively, and generate quasi-obstacle avoidance points A1, B1 and A2, B2; Step 33-2-2: Determine the interference between the paths LP-A1-B1-EP and LP-A2-EP-B2 respectively. The determination method is detailed below. In this step, the interference check uses a simplified model with a ball probe. Step 33-2-3: If the two paths do not interfere, select the shorter path as the obstacle avoidance path; if only one path interferes, select the non-interfering path as the obstacle avoidance path; if both paths interfere, increase the obstacle avoidance height, update the quasi-obstacle avoidance points A1, B1, A2, B2, and repeat the above process until the obstacle avoidance path is generated; Step 33-2-4: Insert the obstacle avoidance waypoints into the original measurement path, generate a new path and save it.

8. The obstacle avoidance method according to claim 1, characterized in that: If the type of interference situation is the fourth type of interference, step 3 specifically includes: Step 31: According to the interference check result, obtain the data coordinates (x1, y1, z1) and (x2, y2, z2) of the previous path point and the interference path point; Step 32: along the angular direction of the interference point (EP) A and the measurement direction, according to the above method, generate quasi-obstacle avoidance points A and B at the previous point (LP), and save the coordinates of point B; Step 33: Calculate the position C of the probe after switching the swing angle. For Rational DMIS three-dimensional coordinate measuring machine, the machine tool coordinate system follows the right-hand rule. The positive direction of the probe angle A is raised along the positive direction of the Y axis, that is, it rotates counterclockwise around the X axis, and the positive direction of the angle B is counterclockwise around the Z axis. The process of solving the position point C is to perform a rotation transformation on the current probe coordinates around the rotation center. Step 34: Determine the interference of the path LP-BC-EP, and do not include the interference check in the special probe BC segment; Step 35: If all segments do not interfere, save the coordinates of the quasi-obstacle avoidance point B; if the path LP-B interferes, translate the previous point along the measurement direction, and repeat Step 2-5 until the path does not interfere; if the path BC or C-EP interferes, translate the quasi-obstacle avoidance point B along the measurement direction of the interference point, and repeat Step 3-5 until the path does not interfere: Step 36: Insert the quasi-obstacle avoidance point B between the previous point and the interference point, generate a new measurement path and save it.

9. The obstacle avoidance method according to claim 8, characterized in that: Step 33 includes: Step 331: Obtain the three normal directions of the machine tool coordinate system, calculate the rotation center position according to the probe parameters and the AB angle data of the previous point, and construct the probe coordinate system with the rotation center as the origin and the three normal directions of the machine tool coordinate system; Step 332: convert point B to the probe coordinate system through coordinate system transformation to obtain point B1; Step 333: Restore the probe coordinates to the state of A=0, B=0, and obtain point B2 (0, 0, -D), where xyz is the coordinate value of point B1; Step 334: Calculate the coordinates of point C. The coordinate measuring machine probe first rotates angle A and then angle B. The calculation method is as follows: Substituting point B2 into the above two equations, we get point C (-Dsinasinb, Dsinaxusb, -Decxsa), where a and b are the swing angle values ​​of the interference point AB respectively. If it is a special probe, it is the swing angle value of AB corresponding to the probe used at the interference point; Step 335: Convert point C to the measurement coordinate system through coordinate system transformation to obtain point C.

10. The obstacle avoidance method according to claim 1, characterized in that: If the type of interference situation is the fifth type of interference, step 3 specifically includes: Step 31: According to the interference check result, obtain the interference path point (EP) and the previous path point (LP) data; Step 32: Perform interference check on the path LP-EP to determine whether there is third-type interference. If so, call the third-type problem obstacle avoidance algorithm and insert the obstacle avoidance point into the measurement path to generate a new path. Step 33: If the obstacle avoidance algorithm for the third type of problem has been called, the last obstacle avoidance point data is extracted, otherwise the previous point data is extracted and marked as point TestPoint; Step 34: According to the method above, calculate the probe coordinate C after the swing angle changes based on TestPoint, and detect the path TestPoint-C-EP. The special probe detects the two paths TestPoint-C and C-EP. If there is interference, call the fourth type of obstacle avoidance algorithm, insert the obstacle avoidance point into the measurement path, and generate a new path. Step 35: Save the optimized path.

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