Helicopter structure three-coordinate measurement obstacle avoidance method

Abstract

The application provides an obstacle avoidance method for helicopter structural member three-coordinate measurement, which comprises the following steps: step 1: according to the interference checking condition in the helicopter structural member three-coordinate measurement process, the helicopter structural member three-coordinate measurement interference condition is classified; the interference condition type comprises 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; step 2: according to the interference point type, the previous point type and the subsequent point type, the helicopter structural member three-coordinate measurement interference is identified; step 3: according to the interference condition type, the helicopter structural member three-coordinate measurement is avoided; and step 4: the interference obstacle avoidance effect of the helicopter structural member three-coordinate measurement is checked.

Description

TECHNICAL FIELD

[0001] The application relates to the field of helicopter structural member measurement, in particular to a three-coordinate measurement obstacle avoidance method for helicopter structural members. BACKGROUND

[0002] Helicopter structural members are increasingly diverse, and three-coordinate measurement is an important means for quality detection of such parts. Preparing a three-coordinate measurement program without collision is an important technical link for quality detection of such parts. However, existing interference checking algorithms cannot cover all cases, cannot effectively monitor machine tool overtravel problems, and cannot perform interference checking on non-measured parts such as fixtures. SUMMARY

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

[0004] Technical scheme: The application provides a three-coordinate measurement obstacle avoidance method for helicopter structural members, which comprises the following steps:

[0005] Step 1: According to the interference checking situation in the three-coordinate measurement process of the helicopter structural member, the three-coordinate measurement interference of the helicopter structural member is classified; the types of interference include first-type interference, second-type interference, third-type interference, fourth-type interference and fifth-type interference;

[0006] Step 2: According to the interference point type, the previous point type and the subsequent point type, the three-coordinate measurement interference of the helicopter structural member is identified;

[0007] Step 3: According to the type of interference, the three-coordinate measurement of the helicopter structural member is avoided;

[0008] Step 4: The interference avoidance effect of the three-coordinate measurement of the helicopter structural member is checked.

[0009] Specifically, the first-type interference is interference occurring in the movement of the probe into the measured feature or into the measuring point;

[0010] The second-type interference is interference occurring in the switching of the safety plane;

[0011] The third-type interference is interference occurring when no safety plane is generated during measurement;

[0012] The fourth-type interference is interference occurring when the probe switches the swing angle;

[0013] The fifth-type interference is interference occurring when the third-type interference and the fourth-type interference are combined and interlaced.

[0014] Specifically, step 3 specifically comprises:

[0015] Step 31: If the type of the interference case is the first type of interference, a first type of interference obstacle avoidance method is used for three-coordinate measurement of the helicopter structural member to avoid obstacles;

[0016] Step 32: According to the interference checking result, interference path point data is obtained;

[0017] Step 33: Corresponding measurement feature information is obtained and the measurement point planning positioning parameter is changed, and the feature positioning point and the position point are updated;

[0018] Step 34: Interference checking is performed on the feature measurement path, if there is interference, the probe number is changed, and interference checking is performed again, and the probe without interference is selected;

[0019] Step 35: A new path is generated and saved.

[0020] Specifically, step 3 specifically includes:

[0021] Step 31: If the type of the interference case is the second type of interference, a second type of interference obstacle avoidance method is used for three-coordinate measurement of the helicopter structural member to avoid obstacles;

[0022] Step 32: According to the interference checking result, interference path point and previous path point data are obtained;

[0023] Step 33: The safe plane data where the interference path point is located is obtained;

[0024] Step 34: The previous path point is projected onto the safe plane where the interference point is located to generate an obstacle avoidance point C1;

[0025] Step 35: It is judged whether the swing angle of the previous point and the interference point is the same, if the swing angles are different, an obstacle avoidance point C2 is generated by extending a probe distance along the measurement direction, the measurement direction of the ball probe is regarded as the normal direction of the safe plane, and the measurement direction of the special probe is regarded as the swing angle direction corresponding to the probe number;

[0026] Step 36: The obstacle avoidance path point is inserted into the original measurement path to generate a new path and save it.

[0027] Specifically, step 3 specifically includes:

[0028] Step 31: If the type of the interference case is the third type of interference, a third type of interference obstacle avoidance method is used for three-coordinate measurement of the helicopter structural member to avoid obstacles;

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

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

[0031] Step 34: judging the probe type, if it is a ball probe, the optimization is ended; if it is a special probe, the new path needs to be checked for interference using a special probe simplified model, if there is no interference, the obstacle avoidance is ended; if there is interference, the new path interference type is judged as the first type of interference, and the special probe first type of interference obstacle avoidance method is used to continue the obstacle avoidance.

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

[0033] Step 33-1-1: constructing a presequence plane and an interference plane according to the coordinates of the presequence point and the interference point and the measurement direction, assuming that the coordinates of the presequence point are , the measurement direction vector is the normal vector of the plane, and the measurement direction vector is , the equation of the presequence plane is , and the equation of the interference plane is ;

[0034] Step 33-1-2: projecting the presequence point to the interference plane to generate an obstacle avoidance point C, the projection method is as follows: first, calculate the intersection line of the presequence plane and the interference plane , the equation of which is

[0035]

[0036] Then, the projection of the line LP-EP connecting the presequence point and the interference point on the interference plane is obtained , and , the intersection point of which is the obstacle avoidance point C;

[0037] Step 33-1-3: inserting the obstacle avoidance point C between the presequence point and the interference point to measure the path LP-C-EP;

[0038] Step 33-1-4: detecting 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: respectively translating the presequence point and the interference point in the opposite direction along the measurement direction by a distance to generate points D1 and E1;

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

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

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

[0043] Step 33-1-9: judging the interference of two paths, the interference checking in this step uses the simplified model of ball probe;

[0044] Step 33-1-10: if both paths interfere, repeating step 33-1-5~step 33-1-9, otherwise selecting the shortest non-interference path;

[0045] Step 33-1-11: inserting the obstacle avoidance point into the original measurement path to generate a new path and save it.

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

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

[0048] Step 33-2-2: judging the interference of paths LP-A1-B1-EP and LP-A2-EP-B2, respectively, the interference checking in this step uses the simplified model of ball probe;

[0049] Step 33-2-3: if both paths do not interfere, selecting the shorter path as the obstacle avoidance path; if only one path interferes, selecting the non-interference path as the obstacle avoidance path; if both paths interfere, increasing the obstacle avoidance height, updating the quasi-obstacle avoidance points A1, B1, A2, B2, and repeating the above process until the obstacle avoidance path is generated;

[0050] Step 33-2-4: inserting the obstacle avoidance point into the original measurement path to generate a new path and save it.

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

[0052] Step 31: obtaining the data coordinates of the previous path point and the interference path point according to the interference checking result and ;

[0053] Step 32: generating quasi-obstacle avoidance points A and B at the previous point (LP) along the direction of the interference point (EP) A and the measurement direction, and saving the coordinates of point B;

[0054] Step 33: calculating the position C of the probe after switching the swing angle, the Rational DMIS three-coordinate measuring machine, the machine tool coordinate system follows the right-hand rule, the positive direction of the A angle of the probe is lifting along the positive direction of the Y axis, that is, rotating counterclockwise around the X axis, the positive direction of the B angle is rotating counterclockwise around the Z axis, and the position point C is solved by rotating the current probe coordinates around the rotation center.

[0055] Step 34: judging the interference of the path LP-B-C-EP, and the special probe B-C segment is not added to the interference check;

[0056] Step 35: if each segment does not interfere, the coordinates of the avoidance obstacle point B are saved; if the path LP-B interferes, the previous point is translated along the measurement direction, and steps 32-35 are repeated until the path does not interfere; if the path B-C or C-EP interferes, the avoidance obstacle point B is translated along the interference point measurement direction, and steps 33-35 are repeated until the path does not interfere;

[0057] Step 36: inserting the avoidance obstacle point B between the previous point and the interference point to generate a new measurement path and save it.

[0058] Specifically, step 33 includes:

[0059] Step 331: obtaining three normal vectors of the machine tool coordinate system, calculating the position of the rotation center according to the probe parameters and the angle data of the previous point AB, and constructing a probe coordinate system with the rotation center as the origin and the three normal vectors of the machine tool coordinate system;

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

[0061] Step 333: restoring the probe coordinates to state to obtain point , where , and xyz is the coordinate value of point B1;

[0062] Step 334: calculating the coordinates of point The probe of the coordinate measuring machine is first rotated by an angle A and then rotated by an angle B, and the calculation method is as follows:

[0063]

[0064]

[0065] Substituting point B2 into the above two formulas gives point , where a and b are the values of the interference point AB swing angle, and if it is a special probe, it is the AB swing angle value corresponding to the probe used by the interference point;

[0066] Step 335: converting point to the measurement coordinate system through coordinate system transformation to obtain point C.

[0067] Specifically, if the type of interference is the fifth type of interference, step 3 specifically includes:

[0068] Step 31: obtaining the interference path point (EP) and the previous path point (LP) data according to the interference check result;

[0069] Step 32: interference checking is performed on the path LP-EP, and it is judged whether the third type of interference exists, if the third type of interference exists, a third type of problem obstacle avoidance algorithm is called, and an obstacle avoidance point is inserted into the measurement path to generate a new path;

[0070] Step 33: if the third type of problem obstacle avoidance algorithm has been called, the last obstacle avoidance point data is extracted, otherwise, the previous point data is extracted, and the previous point data is marked as a point TestPoint;

[0071] Step 34: according to the TestPoint, the probe coordinate C after the swing angle change is calculated, the path TestPoint-C-EP is detected, and the special probe detects the TestPoint-C and C-EP two paths, if the interference exists, a fourth type of obstacle avoidance algorithm is called, and an obstacle avoidance point is inserted into the measurement path to generate a new path.

[0072] Step 35: the optimized path is saved.

[0073] In summary, the application provides an obstacle avoidance method for three-coordinate measurement of a helicopter structure, which classifies the three-coordinate measurement interference of the helicopter structure on the basis of sufficient research on the helicopter structure measurement collision scene, proposes an obstacle avoidance method for each type of interference, and can realize the generation of a collision-free measurement path in a three-coordinate typical scene of the helicopter structure. BRIEF DESCRIPTION OF DRAWINGS

[0074] Figure 1 The first type of interference schematic diagram provided by the application;

[0075] Figure 2 The second type of interference schematic diagram provided by the application;

[0076] Figure 3 The third type of interference schematic diagram provided by the application;

[0077] Figure 4 The fourth type of interference schematic diagram provided by the application;

[0078] Figure 5 The first type of interference avoidance process schematic diagram of the special probe provided by the application;

[0079] Figure 6 The second type of interference avoidance process schematic diagram provided by the application;

[0080] Figure 7 The second type of interference avoidance test example schematic diagram provided by the application;

[0081] Figure 8 The third type of interference avoidance process schematic diagram provided by the application;

[0082] Figure 9The third type of interference situation provided in the present application is a solution method schematic diagram;

[0083] Figure 10 The third type of interference situation provided in the present application is an obstacle avoidance process schematic diagram;

[0084] Figure 11 The third type of interference situation provided in the present application is a solution method schematic diagram;

[0085] Figure 12 The third type of interference situation provided in the present application is an obstacle avoidance process schematic diagram;

[0086] Figure 13 The third type of interference avoidance test example provided in the present application is a schematic diagram;

[0087] Figure 14 The fourth type of interference avoidance process provided in the present application is a schematic diagram;

[0088] Figure 15 The fourth type of interference avoidance method provided in the present application is a schematic diagram;

[0089] Figure 16 The fifth type of interference avoidance process provided in the present application is a schematic diagram;

[0090] Figure 17 The fourth and fifth types of interference avoidance test examples provided in the present application are schematic diagrams;

[0091] Figure 18 The measurement path interference judgment process provided in the present application is a schematic diagram;

[0092] Figure 19 The probe moving scanning body provided in the present application. DETAILED DESCRIPTION

[0093] The present application proposes five types of obstacle avoidance models on the basis of sufficient study on the measurement collision scene of the helicopter structure, so as to solve the measurement obstacle avoidance problem of the helicopter structure under most conditions.

[0094] The present application provides an obstacle avoidance method for helicopter structure three-coordinate measurement, comprising:

[0095] Step 1: According to the interference check in the helicopter structure three-coordinate measurement process, the helicopter structure three-coordinate measurement interference situation is classified;

[0096] Specifically, the type of interference includes first type of interference, second type of interference, third type of interference, fourth type of interference and fifth type of interference;

[0097] (1) The first type of interference is the interference occurring in the movement of the probe entering the measurement feature or entering the measurement point.

[0098] As Figure 1 shown, the first type of interference occurs in the process of the probe entering the measurement feature or entering the measurement point. It is usually caused by unreasonable measurement parameters, such as too small positioning parameters, or the length of the probe is not enough to meet the range of the measurement point, so that only the measurement parameters need to be adjusted or the probe is replaced.

[0099] For a ball probe, according to the inspection characteristics of each part cluster, the measurement parameters of each part cluster at each processing stage are collected into an inspection rule library to reduce the generation of such interference. For a special probe, the first type of interference is usually caused by the existence of multiple accessible probes but unreasonable selection. If the interference still exists after changing the measurement parameters once, the probe number needs to be changed.

[0100] (2) The second type of interference is generated in the process of switching the safety plane.

[0101] As Figure 2 shown, the second type of interference occurs in the process of switching the safety plane. If there are multiple safety planes during measurement, the probe needs to be moved to the next safety plane after measuring the feature at the last safety point of the previous safety plane, and interference may occur in this process. Path point A is the last safety point of the safety plane one, and path point B is the first safety point of the safety plane two. The probe will move from path point A to path point B after measuring the feature at the safety plane one, and interference occurs at this time.

[0102] The present application generates an obstacle avoidance point by the projection insertion point method. For a ball probe, if the swing angles of points A and B are consistent, the path point A is projected to the safety plane two to generate an obstacle avoidance point C1, and the probe moves along A-C1-B to avoid collision. If the swing angles of points A and B are inconsistent, the obstacle avoidance point C2 is generated by extending outward along the normal direction of the safety plane two with C1 as the origin and a probe length, and the probe moves along A-C1-C2-B. For a special probe, if the probe numbers used by path point A and path point B are inconsistent, the obstacle avoidance point C2 is generated by extending outward along the direction of the probe at point B with C1 as the origin and a probe length, and the special probe moves along A-C1-C2-B.

[0103] (3) The third type of interference is generated when there is no safety plane during measurement.

[0104] As Figure 3 shown, the third type of interference may occur when switching the measurement feature when there is no safety plane. Path point A is the last positioning point of the measurement feature one, and path point A1 is the corresponding position point. Path point B is the first positioning point of the measurement feature two, and path point B1 is the corresponding position point. When switching from the feature one to the feature two, the probe moves along A-A1-B1-B, and the interference occurs between A1-B1. Therefore, an obstacle avoidance point needs to be inserted between A1-B1 to avoid collision, and the optimization method of the third type of interference is described below.

[0105] (4) The fourth type of interference is generated when the probe switches the swing angle.

[0106] As shown in Figure 4 , the fourth type of interference is generated when the probe switches the swing angle. The three-coordinate measuring machine follows the principle of swing angle first and then movement. If the path point A and the path point C have different swing angles, when the probe moves from A to C, the swing angle is switched at the path point A first, and the probe position changes from A to B, that is, the probe moves along A-B-C, and the interference occurs between A-B. Under the traditional three-coordinate programming mode, the fourth type of interference is difficult to effectively avoid in the path planning stage, and it is also difficult to find in the simulation stage, so it is often exposed in the test stage. Therefore, experienced inspectors will preset a path point far away from the measured object before switching the swing angle, which reduces the probability of the occurrence of the fourth type of interference, but increases the measurement time.

[0107] (5) The fifth type of interference is the interference that the third type of interference and the fourth type of interference are combined and interwoven.

[0108] In the actual measurement process, the fourth type of interference often occurs at the same time as the third type of interference, or the third type of interference occurs at the same position after avoiding the fourth type of interference. The present application refers to the interference condition that the third and fourth types of interference are combined and interwoven as the fifth type of interference. If the interference checking and the driving obstacle avoidance scheme are only relied on the measurement simulation, multiple simulations are needed and unnecessary obstacle avoidance costs are easily increased. The subsequent optimization method for the fourth type of interference will be supplemented and the optimization method for this type of interference will be further described.

[0109] Step 2: According to the type of interference point, the type of previous point and the type of subsequent point, the three-coordinate measurement interference of the helicopter structure is identified;

[0110] The present application simulates the three-coordinate measurement process based on the simulation engine of Vericut, and obtains the VERICUT simulation report by using the report interface, obtains the interference data, identifies the type of interference point data, the type of previous point and the type of subsequent point, and judges the type of interference according to the following table.

[0111] The previous point type is a point position arranged in sequence before the current point position of a measurement path by a sequence of points; and the subsequent point type is a point position arranged in sequence after the current point position of a measurement path by a sequence of points.

[0112] Table 1: Judgment criterion table of three-coordinate measurement interference type of helicopter structure

[0113]

[0114] Step 3: According to the type of interference, the three-coordinate measurement of the helicopter structure is obstacle avoidance.

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

[0116] Specifically, step 4 includes:

[0117] Step 41: obtaining a current part pointer.

[0118] More specifically, a 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 according to the path.

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

[0120] More specifically, the entity feature interface of the current part is retrieved from the part interface; all geometric features under the current part are obtained by traversing the entity feature interface.

[0121] Step 43: topological analysis and obtaining a surface topological unit.

[0122] More specifically, a geometric feature management interface of each geometric feature is created by traversing the current geometric feature set; the topological structure of each feature is obtained by traversing the geometric feature management interface set; the surface unit is obtained by topological analysis by traversing all topological structures.

[0123] Step 44: interference checking.

[0124] More specifically, a geometric container of the to-be-detected path is created, and is parameterized with the topological unit; all parameterized surfaces of the to-be-detected path are traversed, and are sequentially intersected with the topological unit; if there is an intersection, it is judged as interference, otherwise it is not interference.

[0125] Embodiment one

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

[0127] Step 31: if the type of the interference case is the first type of interference, the first type of interference avoidance method is used to avoid obstacles for the three-coordinate measurement of the helicopter structure;

[0128] The first type of interference avoidance method, based on the above discussion of the first type of interference problem, can greatly reduce the probability of the first type of interference of the ball probe. The path planning mode of the feature unit of the application is extremely convenient for the adjustment of the first type of interference of the ball probe. Therefore, the application only designs a special probe first type of interference avoidance algorithm, and the flow is as shown in Figure 5 , and the steps are as follows.

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

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

[0131] Step 34: Perform interference checking on the feature measurement path, if there is interference, change the probe number, and perform interference checking again, and select the probe without interference;

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

[0133] Example Two

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

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

[0136] Step 32: Obtain the interference path point and the previous path point data according to the interference checking result;

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

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

[0139] Step 35: Determine whether the swing angle of the previous point and the interference point is the same, if the swing angles are different, extend an obstacle avoidance point C2 along the measurement direction by a probe distance, the measurement direction of the ball probe is regarded as the normal direction of the safe plane, and the measurement direction of the special probe is regarded as the swing angle direction corresponding to the probe number;

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

[0141] It should be noted that the second type of interference obstacle avoidance method is tested on a small aluminum alloy structure model, and the result is shown in Figure 7 , the obstacle avoidance path indicated by the arrow in the figure is the non-interference path, which verifies the feasibility of the method.

[0142] Example Three

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

[0144] Step 31: if the type of the interference case is the third type of interference, then the third type of interference is used to avoid obstacles for the three-coordinate measurement of the helicopter structure;

[0145] Step 32: according to the interference checking result, interference path points (EP) and previous path points (LP) data are obtained;

[0146] Step 33: the angle between the two path point measurement directions is calculated, and the corresponding obstacle avoidance method is matched according to the angle range;

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

[0148] It should be noted that if the angle between the two point measurement directions is less than 90°, the feature adjacent case is divided into "convex adjacent" and "concave adjacent", as shown in Figure 9 , and the obstacle avoidance process is as shown in Figure 10 .

[0149] Step 33-1-1: according to the coordinates of the previous point and the interference point and the measurement direction, a previous plane and an interference plane are constructed, the coordinates of the previous point are , the measurement direction vector, that is, the normal vector of the plane, is , then the equation of the previous plane is , and the equation of the interference plane is ;

[0150] Step 33-1-2: project the previous point to the interference plane to generate an obstacle avoidance point C, the projection method is as follows: first, calculate the intersection line of the previous plane and the interference plane , the equation of which is

[0151]

[0152] Then, the projection of the line LP-EP of the previous point and the interference point on the interference plane is obtained , and The intersection of and 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: detect 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: respectively translate the previous point and the interference point along the measurement direction in the opposite direction by a distance to generate points D1 and E1;

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

[0157] Step 33-1-7: Project the pre-sequence 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 pre-sequence plane to the interference plane to generate D2, the projection method is the same as 33-1-2);

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

[0159] Step 33-1-9: Determine the interference of the two paths, and the interference check in this step uses the simplified model of the ball probe;

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

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

[0162] It should be noted that if the angle between the two point measurement directions is greater than 90°, the obstacle avoidance method is as shown in Figure 11 . Thanks to the characteristics of Rational DMIS three-coordinate measuring machine, the first and second normal directions of the measurement coordinate system, i.e. the positive direction of the Z axis and the positive direction of the X axis, always point away from the measured object, so the next two directions can be used as obstacle avoidance directions to guide the generation of obstacle avoidance points. The obstacle avoidance process is as shown in Figure 12 .

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

[0164] Step 33-2-2: Respectively determine the interference of paths LP-A1-B1-EP and LP-A2-EP-B2, and the interference check in this step uses the simplified model of the ball probe;

[0165] Step 33-2-3: If both 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 point into the original measurement path to generate a new path and save it.

[0167] Step 34: judging the probe type, if it is a ball probe, the optimization is ended. If it is a special probe, the new path needs to be checked for interference using a special probe simplified model, if there is no interference, the obstacle avoidance is ended; if there is interference, the new path interference type is judged as the first type of interference, and the obstacle avoidance is continued using the special probe first type of interference obstacle avoidance method.

[0168] The algorithm is tested on a small aluminum alloy structure model, and the results are shown in Figure 13 , the path indicated by the arrow in the figure is an interference-free path, which verifies the feasibility of the method.

[0169] Example four

[0170] The embodiment of the present application takes the fourth type of interference as an example to explain step 3 in detail.

[0171] According to the analysis of the fourth type of interference problem, the ball probe swing angle switching follows the order of changing A angle first and then changing B angle, so before switching the swing angle, the path point A is lifted along the A angle direction of the path point C to get point , if the probe direction changes after changing the A angle, which is inconsistent with the swing direction at C, then the path point A1 is lifted along the C measurement direction at to get point , and vice versa , that is, the A1 lifting distance calculation method is as follows:

[0172]

[0173]

[0174] Wherein is the distance from the probe head to its rotation center, are the A angle and B angle difference values of points A and C respectively. The ball probe moves along A-A1-B1-C to avoid collision. When the special probe swing angle changes, the probe posture does not change, but the moving center is changed to the corresponding probe head center, so there is no path A1-B1, but it moves along A-A1, and then moves along B1-C.

[0175] As shown in Figure 14 , step 3 specifically includes:

[0176] Step 31: if the type of interference is the fourth type of interference, according to the interference checking result, the data coordinates of the previous path point and the interference path point and are obtained;

[0177] Step 32: along the A angle direction and the measurement direction of the interference point (EP), the quasi-obstacle avoidance points A and B are generated at the previous point (LP) according to the method in the foregoing, and the B point coordinates are saved, as shown inFigure 15 The specific algorithm is as follows: since the ball probe swing angle switching follows the sequence of changing A angle and then changing B angle, the previous point is lifted in the A angle direction of the interference point before the switching swing angle to obtain point B , if the probe direction is inconsistent with the swing angle direction at C after changing the A angle, the previous point is lifted in the C measurement direction at to obtain point B , and vice versa , that is, B, and the lifting distance is calculated as follows:

[0178] ；

[0179] ；

[0180] wherein is the distance from the probe head to the rotation center, is the difference between the A angle and the B angle of the previous point and the interference point, respectively. The ball probe moves along LP-B-C-EP to avoid collision. When the special probe swing angle changes, the probe posture does not change, but the movement center is changed to the corresponding probe head center, so there is no path B-C, but the probe moves along LP-B and then moves along C-EP;

[0181] Step 33: calculating the position C of the probe head after the switching swing angle, the machine tool coordinate system of the Rational DMIS three-coordinate measuring machine follows the right-hand rule, the positive direction of the A angle of the probe head is lifting along the Y axis in the positive direction, that is, counterclockwise rotation around the X axis, the positive direction of the B angle is counterclockwise rotation around the Z axis, and the position point C is solved by rotating the current probe head coordinate around the rotation center;

[0182] Specifically, step 33 includes:

[0183] Step 331: obtaining three normal vectors of the machine tool coordinate system, calculating the rotation center position according to the probe head parameters and the A and B angle data of the previous point, and constructing the probe coordinate system with the rotation center as the origin and the three normal vectors of the machine tool coordinate system;

[0184] Step 332: converting point B to the probe coordinate system to obtain point B1 through coordinate system transformation;

[0185] Step 333: restoring the probe head coordinate to the state to obtain point , wherein , xyz is the coordinate value of point B1;

[0186] Step 334: calculating the coordinate of point , the probe head of the three-coordinate measuring machine is first rotated by the A angle and then rotated by the B angle, and the calculation method is as follows:

[0187] ;

[0188] ;

[0189] The point B2 is brought into the above two formulas to obtain the point , where a and b are the swing angle values of the interference point AB, and if it is a special probe, it is the swing angle value corresponding to the probe used by the interference point;

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

[0191] Step 34: judge the interference of the path LP-B-C-EP, and the judgment method is described below. The B-C segment of the special probe is not added to the interference check.

[0192] Step 35: if each segment does not interfere, save the coordinates of the obstacle avoidance point B; if the path LP-B interferes, translate the previous point in the measurement direction, and repeat steps 32-35 until the path does not interfere; if the path B-C or C-EP interferes, translate the obstacle avoidance point B along the measurement direction of the interference point, and repeat steps 33-35 until the path does not interfere.

[0193] Step 36: insert the obstacle avoidance point B between the previous point and the interference point to generate a new measurement path and save it.

[0194] Example five

[0195] The embodiment of the present application takes the fifth type of interference as an example to explain the step 3 in detail.

[0196] It should be noted that according to the discussion of the fifth type of interference obstacle avoidance method, the present application 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 of the probe switching swing angle process, so after using this method to realize the fourth type of interference obstacle avoidance, the third type of interference will not appear at the same position. Therefore, the fifth type of interference problem obstacle avoidance method is essentially a call to the third and fourth type of interference problem obstacle avoidance method.

[0197] As shown in Figure 16 , step 3 specifically includes:

[0198] Step 31: if the type of interference 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 a third type of interference, if there is, call the third type of problem obstacle avoidance algorithm, and insert the obstacle avoidance point into the measurement path to generate a new path;

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

[0201] Step 34: according to TestPoint, the coordinate C of the probe after the change of the swing angle is calculated, the path TestPoint-C-EP is detected, and the special probe detects the two paths of TestPoint-C and C-EP, if there is interference, the fourth type of avoidance algorithm is called, and the avoidance point is inserted into the measurement path to generate a new path.

[0202] Step 35: save the optimized path.

[0203] The algorithm is tested on a small aluminum alloy structure model, and the fourth and fifth types of interference avoidance algorithms are also tested, and the results are shown in Figure 17 The avoidance path indicated by the arrow in the figure is the non-interference path, which verifies the feasibility of the method.

[0204] Under normal circumstances, the probe of the three-coordinate measuring machine is closer to the measured part than the spindle of the machine tool, and if a collision occurs during measurement, the probe will collide with the measured part first. In the above interference judgment process, the measured path is essentially divided into several detection units, each detection unit is composed of two path points and the path between them, and during movement, the posture of the probe does not change. Therefore, the parametric surface of the measured path can be generated by the sweep body as shown in Figure 19 The probe sweep body can be regarded as several four-prism columns, which are adjusted according to the swing angle.

[0205] In summary, the present application provides an obstacle avoidance method for three-coordinate measurement of helicopter structural parts, which classifies the interference of three-coordinate measurement of helicopter structural parts on the basis of sufficient study of the measurement collision scene of helicopter structural parts, proposes an obstacle avoidance method for each interference condition, and can realize the generation of a collision-free measurement path in the three-coordinate typical scene of helicopter structural parts.

Claims

1. An obstacle avoidance method for coordinate measuring of helicopter structural components, characterized in that, The methods include: Step 1: Based on the interference checks during the coordinate measuring machine (CMM) measurement of helicopter structural components, classify the interference conditions of the CMM measurement of helicopter structural components; the types of interference conditions include Type I interference, Type II interference, Type III interference, Type IV interference, and Type V interference; Step 2: Identify the interference of the coordinate measuring machine on the helicopter structural components based on the type of interference point, the type of preceding point, and the type of succeeding point; Step 3: Based on the type of interference, perform obstacle avoidance in the coordinate measuring machine (CMM) of the helicopter structural components; Step 4: Check the interference obstacle avoidance effect of the coordinate measuring machine on the helicopter structural components; The first type of interference occurs during the movement of the probe into the measurement feature or into the measurement point. The second type of interference is interference that occurs during the switching of safety planes; The third type of interference is interference that occurs when there is no safe plane during measurement; The fourth type of interference is the interference that occurs when the probe switches its swing angle; The fifth type of interference is an interference that occurs through a complex interweaving of the third and fourth types of interference; Step 3 specifically includes: Step 31: If the type of interference is the third type of interference, then use the third type of interference obstacle avoidance method to perform obstacle avoidance on the coordinate measurement of the helicopter structural components; Step 32: Based on the interference check results, obtain the interference path point (EP) and preceding 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 range of the angle; Step 34: Determine the probe type. If it is a ball probe, the optimization ends. If it is a special probe, the new path needs to be checked for interference using the special probe simplified model. If there is no interference, the obstacle avoidance ends. If there is interference, the new path interference type is determined to be the first type of interference, and the obstacle avoidance method of the first type of interference using the special probe is used to continue obstacle avoidance. If the angle between the directions of the two measurements is less than 90°, then step 33 specifically includes: Step 33-1-1: Construct the preceding plane and the interference plane based on the coordinates of the preceding points and the interference points, and the measurement direction. Let the coordinates of the preceding points be... The measurement direction vector, i.e., the normal vector of the surface, is... Then the equation of the preceding plane is Similarly, the interference plane is constructed, and the equation is: ; Step 33-1-2: Project the preceding point onto the interference plane to generate the obstacle avoidance point C. The projection method is as follows: First, calculate the intersection line between the preceding plane and the interference plane. Its equation is Then, the projection of the line LP-EP connecting the preceding point and the interference point onto the interference plane is obtained. , and The intersection point is the obstacle avoidance point C; Step 33-1-3: Insert obstacle avoidance point C between the preceding point and the interference point, and measure the path LP-C-EP; Step 33-1-4: Detect the interference of the path LP-C-EP. If there is no interference, obstacle avoidance is completed and proceed to the next step; otherwise, proceed to the next step. Step 33-1-5: Shift the interference points of the preceding points a certain distance in the opposite direction of the measurement direction to generate points D1 and E1; Step 33-1-6: Reconstruct the preceding plane and interference plane based on D1 and E1, using the same method as step 33-1-1; Step 33-1-7: Project the preceding points along the normal of the interference plane onto the interference plane to generate E2; project the interference points along the normal of the preceding plane onto the interference plane to generate D2. The projection method is the same as in step 33-1-2. Step 33-1-8: Generate the paths LP-D1-D2-EP and LP-E2-E1-EP; Step 33-1-9: Determine the interference between the two paths. This 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, choose the shortest non-interfering path. Step 33-1-11: Insert obstacle avoidance waypoints into the original measurement path, generate a new path, and save it.

2. The obstacle avoidance method according to claim 1, characterized in that, Step 3 specifically includes: Step 31: If the type of interference is Type I interference, then use the Type I interference obstacle avoidance method to perform obstacle avoidance on the coordinate measurement of the helicopter structural components; Step 32: Based on the interference check results, obtain the interference path point data; Step 33: Obtain the corresponding measurement feature information and change the measurement point planning and positioning parameters to update the feature positioning point and location point; Step 34: Perform an interference check on the feature measurement path. If interference exists, change the probe number and perform the interference check again. Select the probe that does not have interference. Step 35: Generate a new path and save it.

3. The obstacle avoidance method according to claim 1, characterized in that, Step 3 specifically includes: Step 31: If the type of interference is Type II interference, then use the Type II interference obstacle avoidance method to perform obstacle avoidance on the coordinate measurement of the helicopter structural components; Step 32: Based on the interference check results, obtain the interference path points and preceding path point data; Step 33: Obtain the safety plane data where the interference path point is located; Step 34: Project the previous path points onto the safe plane where the interference point is located to generate obstacle avoidance point C1; Step 35: Determine whether the swing angles of the preceding point and the interference point are the same. If the swing angles are different, extend the probe distance along the measurement direction to generate obstacle avoidance point C2. The measurement direction of the ball probe is regarded as the normal of the safety plane, and the measurement direction of the special probe 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.

4. The obstacle avoidance method according to claim 1, characterized in that, If the angle between the directions of the two measurements is greater than 90°, then step 33 specifically includes: Step 33-2-1: Raise the preceding point and the interference point by a certain height along the positive Z-axis and the positive X-axis respectively to generate quasi-obstacle avoidance points A1, B1 and A2, B2; Step 33-2-2: Determine the interference between paths LP-A1-B1-EP and LP-A2-EP-B2 respectively. This interference check uses a simplified model with a ball probe. Step 33-2-3: If neither path interferes, 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, and B2, and repeat the above process until an 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.

5. The obstacle avoidance method according to claim 4, characterized in that, If the type of interference is Type IV interference, then step 3 specifically includes: Step 31: Based on the interferometry results, obtain the coordinates of the preceding path points and the interferometry path points. and ; Step 32: Along the direction of angle A at the interference point (EP) and the measurement direction, generate quasi-obstacle avoidance points A and B at the preceding point (LP), and save the coordinates of point B; Step 33: Calculate the position C of the probe after switching the swing angle. The Rational DMIS coordinate measuring machine follows the right-hand rule. The positive direction of the probe angle A is the upward movement along the positive Y-axis, that is, the counterclockwise rotation around the X-axis. The positive direction of the probe angle B is the counterclockwise rotation around the Z-axis. The process of solving the position point C is to perform a rotation transformation of the current probe coordinates around the rotation center. Step 34: Determine the interference situation of the path LP-BC-EP. The BC segment of the special probe is not included in the interference check. Step 35: If there is no interference between the segments, save the coordinates of the quasi-obstacle avoidance point B; if the path LP-B interferes, translate the preceding point along the measurement direction and repeat steps 32-35 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 steps 33-35 until the path does not interfere. Step 36: Insert the quasi-obstacle avoidance point B between the preceding point and the interference point to generate a new measurement path and save it.

6. The obstacle avoidance method according to claim 5, characterized in that, Step 33 includes: Step 331: Obtain the three normals of the machine tool coordinate system. Based on the probe parameters and the AB angle data of the previous point, calculate the position of the rotation center and construct the probe coordinate system with the rotation center as the origin and the three normals of the machine tool coordinate system. Step 332: Transform point B to the probe coordinate system using coordinate system transformation to obtain point B1; Step 333: Restore the probe coordinates to State, obtain point ,in, x, y, and z are the coordinates of point B1; Step 334: Calculate points The coordinates are determined by rotating the probe of a coordinate measuring machine by angle A first, then by angle B. The calculation method is as follows: ； ； Substituting point B2 into the above two equations, we get the point... , where a and b are the AB swing angle values ​​of the interference point, respectively; if it is a special probe, they are the AB swing angle values ​​corresponding to the probe used at the interference point. Step 335: Place the point By transforming the coordinate system to the measurement coordinate system, point C is obtained.

7. The obstacle avoidance method according to claim 6, characterized in that, If the type of interference is Type V interference, then step 3 specifically includes: Step 31: Based on the interference check results, obtain the interference path point (EP) and preceding path point (LP) data; Step 32: Perform an interference check on the path LP-EP to determine if there is a third type of interference. If so, call the obstacle avoidance algorithm for the third type of problem 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, extract the data of the last obstacle avoidance point; otherwise, extract the data of the preceding points and mark them as points TestPoint. Step 34: Based on TestPoint, calculate the probe coordinates C after the swing angle change, and detect the path TestPoint-C-EP. For special probes, detect the two path segments TestPoint-C and C-EP. If there is interference, call the fourth type of obstacle avoidance algorithm and insert the obstacle avoidance point into the measurement path to generate a new path. Step 35: Save the optimized path.

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