Crankshaft balance block center distance automatic detection device and method based on visual measurement

Abstract

The invention provides a device and a method for automatically detecting the center distance of a crankshaft balance block based on vision measurement. The detection device comprises a crankshaft transfer robot and a visual detection unit. The crankshaft transferring robot comprises a multi-axis mechanical arm and a grabbing mechanism, and the grabbing mechanism comprises a mounting connecting plate, a first clamping jaw assembly and a second clamping jaw assembly, wherein the first clamping jaw assembly and the second clamping jaw assembly are distributed in a 180-degree mode; the visual detection unit comprises a box body, a main body platform, a sliding table, a jig, a backlight source, a calibration plate, a reciprocating transposition driving mechanism, an in-place sensor, a reinforcing bracket, an industrial camera, a telecentric lens, an electric control cabinet and a man-machine interaction terminal. The crankshaft is automatically fed and discharged through the crankshaft transfer robot, the center distance of the crankshaft balance block is automatically and rapidly detected through the visual detection unit and the image detection technology, the detection precision is high, the efficiency is high, the consistency is good, and the crankshaft product quality is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of crankshaft detection of a core component of an automobile engine, and in particular to a device and method for automatically detecting the center distance of a crankshaft balancing block based on visual measurement. Background Art

[0002] The crankshaft is the core component of the engine. Its function is to convert the linear reciprocating motion of the piston into rotational motion and output the power in a unified manner. In order to balance the rotational centrifugal force and its torque, a counterweight (also called a counterweight) is installed on the crankshaft. The number, size and placement of the counterweight should be considered according to factors such as the number of cylinders in the engine, the cylinder arrangement and the shape of the crankshaft. If the center distance of the balance block is incorrect during the manufacturing process, it may cause the crankshaft to be unbalanced, causing the engine vibration to increase, increasing the wear of parts, shortening the engine life, and then causing the stability of the vehicle, reducing driving safety and increasing driving risks. Therefore, in order to ensure the normal operation of the engine and the performance of the vehicle, the center distance of the crankshaft balance block must meet the design requirements and remain correct.

[0003] At present, the method of testing the center distance of crankshaft balance blocks in the processing workshop of automobile crankshaft parts is mostly done manually using a cardboard, which is not only time-consuming and labor-intensive, but also has a large error range and cannot guarantee the consistency of the product. When testing a large number of crankshafts, the workers are extremely tired. Some factories currently use Zeiss three-coordinate devices for testing, which is not only expensive, but also takes too long and is very inefficient. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the object of the present invention is to provide a device and method for automatically detecting the center distance of crankshaft balance blocks based on visual measurement.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is: an automatic detection device for the center distance of crankshaft balance blocks based on visual measurement, comprising:

[0006] A crankshaft transfer robot, comprising a multi-axis mechanical arm and a gripping mechanism, wherein the gripping mechanism comprises a mounting connection plate, a first gripping jaw assembly and a second gripping jaw assembly, wherein the mounting connection plate is mounted at the end of the multi-axis mechanical arm, the first gripping jaw assembly and the second gripping jaw assembly are respectively mounted on both sides of the mounting connection plate, and the first gripping jaw assembly and the second gripping jaw assembly both comprise two gripping jaw mechanisms arranged on the left and right sides;

[0007] The visual inspection unit comprises a box, a main platform, a slide, a fixture, a backlight source, a calibration plate, a reciprocating transposition drive mechanism, an in-position sensor, a reinforcement bracket, three industrial cameras, a telecentric lens, an electrical control cabinet and a human-computer interaction terminal. The main platform is installed in the box, and a loading and unloading station and a detection station are provided on the main platform. The slide is installed between the loading and unloading station and the detection station on the main platform; the fixture can be installed on the slide in a translational manner, and the fixture comprises a bottom plate, two V-groove plates arranged on the left and right, a positioning pin mechanism and a pressure sensor, the V-groove plate is used to support the crankshaft workpiece to be tested, the positioning pin mechanism comprises a positioning pin and a jacking drive mechanism, the positioning pin is used to position the crankshaft workpiece to be tested, and the pressure sensor The sensor is used to detect whether the crankshaft to be tested is placed on the fixture; the reciprocating transposition drive mechanism is used to drive the fixture to move and transpose between the loading and unloading station and the detection station, and the in-position sensor is used to detect whether the fixture is moved to the loading and unloading station or the detection station; the backlight source and the calibration plate are installed at the detection station position of the main platform, the backlight source is located below the calibration plate, the reinforcement bracket is installed on the box, and the three industrial cameras are installed on the reinforcement bracket. The three industrial cameras are respectively located directly above the left end balance block, the right end balance block and the middle balance block group of the crankshaft to be tested, and the telecentric lens is connected to the industrial camera; the electrical control cabinet is located below the main platform, and the human-computer interaction terminal is located on the side of the box.

[0008] By adopting the technical solution of the present invention, the crankshaft is automatically loaded and unloaded by a crankshaft transfer robot, and the center distance of the crankshaft balance block is automatically and quickly detected by the visual detection unit through image detection technology. The detection has high accuracy, high efficiency and good consistency, thereby ensuring the quality of the crankshaft product.

[0009] Furthermore, a guide groove is arranged on the table top of the main platform, and the slide is installed in the guide groove.

[0010] By adopting the above preferred solution, the stability of the slide table is improved, the displacement accuracy of the fixture is ensured, and the accuracy of image detection is improved.

[0011] Furthermore, the clamping mechanism includes a linear drive cylinder, a hexagonal bracket, a left clamping jaw, a right clamping jaw, a left first connecting rod, a left second connecting rod, a left third connecting rod, a right first connecting rod, a right second connecting rod, a right third connecting rod and a linkage block. The cylinder seat of the linear drive cylinder is fixedly mounted on the mounting connecting plate, the hexagonal bracket is connected to the cylinder seat of the linear drive cylinder, the middle part of the linkage block is connected to the telescopic rod of the linear drive cylinder, one end of the left first connecting rod is hinged to the left end of the linkage block, and one end of the right first connecting rod is hinged to the right end of the linkage block. The other end of the left first connecting rod is hinged to one end of the left second connecting rod, the other end of the right first connecting rod is hinged to one end of the right second connecting rod, the middle part of the left second connecting rod is hinged to the left end of the hexagonal bracket, the middle part of the right second connecting rod is hinged to the right end of the hexagonal bracket, the other end of the left second connecting rod is hinged to the left clamping claw, the other end of the right second connecting rod is hinged to the right clamping claw, one end of the left third connecting rod is hinged to the hexagonal bracket, the other end of the left third connecting rod is hinged to the left clamping claw, and the other end of the right third connecting rod is hinged to the right clamping claw.

[0012] By adopting the above preferred solution, stable grasping of the crankshaft workpiece can be achieved.

[0013] The method for automatically detecting the center distance of a crankshaft balance block based on visual measurement comprises the following steps: step S1, calibrating the internal and external parameters of three industrial cameras;

[0014] Step S1 specifically includes:

[0015] S11, turning on the backlight source, and photographing the straight line generated by the transparent calibration plate under the backlight source by adjusting the exposure of the camera;

[0016] S12, calling a camera calibration algorithm to calibrate the intrinsic parameters and extrinsic parameters of the camera, wherein the intrinsic parameters include but are not limited to focal length, principal point coordinates, and distortion coefficients, and the extrinsic parameters include but are not limited to rotation matrix and translation vector, to respectively determine the internal imaging characteristics of the camera and the position and posture of the camera in the world coordinate system;

[0017] S13, turn off the backlight source;

[0018] Step S2, the crankshaft transfer robot grabs the current crankshaft workpiece and puts it on the fixture at the loading and unloading station. When the pressure sensor detects pressure, the jacking drive mechanism drives the positioning pin to position and fix the current crankshaft workpiece; the crankshaft transfer robot returns to grab the next crankshaft workpiece;

[0019] Step S3, the reciprocating drive mechanism drives the fixture to move to the inspection station;

[0020] Step S4, after the in-place sensor detects the in-place signal of the fixture at the detection station, the backlight source is turned on, and the industrial camera takes a picture of the current crankshaft workpiece and determines the size;

[0021] Step S4 specifically includes:

[0022] S41, after the in-position sensor detects the in-position signal of the fixture at the detection station, the backlight source is turned on, and the crankshaft balance block is started to be photographed to obtain a shadow image of the balance block within the depth of field of each camera;

[0023] S42, calling the internal and external parameters of the industrial camera determined in step S1, performing a rigid body transformation on the coordinate system of each industrial camera, converting it into a common world coordinate system and splicing them to form an overall crankshaft balancing block shadow map;

[0024] S43, construction of the reference measurement line for the shadow map;

[0025] Step S43 specifically includes:

[0026] S431, finding the intermediate balancing block group from the overall crankshaft balancing block shadow diagram;

[0027] S432, select four different points (x11, x11), (x12, y11), (x12, y12), (x11, y12) on both sides of the middle balancing block group, where (x11, x11) and (x12, y11) are on a horizontal line, and (x12, y12) and (x11, y12) are on a horizontal line;

[0028] S433, respectively connect the two points (x11, x11) and (x12, y11), and the two points (x12, y12) and (x11, y12) on the same horizontal line to obtain two line segments, and calculate the center point (X 01 , Y 01 ) and (X 02 , Y 02 );

[0029] S434: Obtain the position coordinates (X 01 , Y 01 ) and (X 02 , Y 02 ), and construct the reference measurement line through the formula, the formula is as follows:

[0030]

[0031] That is the equation:

[0032] (y 02 -y 01 )x+(x 01 -x02 )y+x 02 y 01 -y 02 x 01 =0;

[0033] S44: calculating the vertical distance from the constructed reference measurement line to the edge of each balancing block shadow image, and determining whether the vertical distance is within the error range, thereby determining whether a normal workpiece signal or an abnormal workpiece signal is generated;

[0034] Step S44 specifically includes:

[0035] S441, Agreement: A = Y 02 -Y 01 ; B = X 01 -X 02 ; C = X 02 Y 01 -Y 02 X 01 ;

[0036] Therefore, the equation:

[0037] (y 02 -y 01 )x+(x 01 -x 02 )y+x 02 y 01 -y 02 x 01 =0;

[0038] Evolves to: Ax+By+C=0;

[0039] S442, select two measuring points on each side of the balance block, and calculate the vertical distance dij from each measuring point on the balance block to the reference measuring line by using the formula, where i is the balance block number of the measuring point, starting from number 1, and j is two different points of the balance block of the measuring point, starting from number 1. The specific formula is as follows:

[0040]

[0041] S443, respectively obtain the vertical distance from each side of the balancing block to the reference measurement line, and take the average value as the final vertical distance of the balancing block center distance detection. If the vertical distance is within the error range, the crankshaft workpiece to be detected is determined to be a qualified part, and a workpiece normal signal is generated. If the vertical distance is not within the error range, the crankshaft workpiece to be detected is determined to be an unqualified part, and a workpiece abnormal signal is generated;

[0042] Step S5, the reciprocating drive mechanism drives the fixture to move to the loading and unloading station;

[0043] Step S6, the crankshaft transfer robot grabs the current crankshaft workpiece that has been inspected, then rotates 180°, places the next crankshaft workpiece on the fixture, and then rotates 180° again and moves to the set position to place the current crankshaft workpiece that has been inspected.

[0044] Furthermore, in step S1, a shooting performance analysis step is also included:

[0045] S14, placing a test workpiece at the inspection station, turning on the backlight source, photographing the test workpiece with an industrial camera to obtain a real-time shadow image, and analyzing the photographing performance of the industrial camera based on the real-time shadow image; wherein the test workpiece is a qualified workpiece without any error;

[0046] Step S14 specifically includes:

[0047] S141, inputting a standard image of the test workpiece taken at the same viewing angle;

[0048] S142, extracting a real-time workpiece contour image of the test workpiece in the real-time image and a standard workpiece contour image of the test workpiece in the standard image according to the pixel point difference;

[0049] S143, establishing a rectangular coordinate system with the upper left corner of the standard workpiece outline drawing, and selecting any coordinate point in the standard workpiece outline drawing, while the coordinate point is on the test workpiece, and the coordinate point is calibrated as a feature point Di, i is the number of the feature point, i=1, 2, ..., n, n is a positive integer;

[0050] S144, selecting a feature point as the starting point, calculating the interval distances between the starting point and all other feature points, and using the interval distances as feature values ​​of the feature points corresponding to the starting point;

[0051] S145, similarly, selecting the next feature point as the starting point, and obtaining the feature values ​​of all feature points according to the above operation;

[0052] S146, constructing a first characteristic matrix of the standard workpiece contour map according to the characteristic values ​​of all characteristic points;

[0053] S147, similarly, according to steps S143 to S146, a second characteristic matrix of the real-time workpiece contour image is constructed;

[0054] S148, comparing the first characteristic matrix with the second characteristic matrix;

[0055] If any eigenvalue in the first characteristic matrix is ​​different from the eigenvalue at the corresponding position in the second characteristic matrix, a device abnormality signal is generated;

[0056] If all eigenvalues ​​in the first characteristic matrix are the same as the eigenvalues ​​at corresponding positions in the second characteristic matrix, a normal device signal is generated.

[0057] Furthermore, in step S4, before step S41, step S40 is also included, inputting corresponding historical detection data according to the model of the crankshaft workpiece to be detected, and obtaining the detection force of the crankshaft workpiece to be detected based on the historical detection data;

[0058] Step S40 specifically includes:

[0059] S401, obtaining the number of inspections and the number of abnormal inspections of the same type of crankshaft workpiece as the crankshaft workpiece to be inspected, and obtaining the abnormal inspection rate YL of the same type of crankshaft workpiece as the crankshaft workpiece to be inspected by dividing the number of abnormal inspections by the number of inspections;

[0060] S402, obtaining the error value of a crankshaft workpiece of the same model as the crankshaft workpiece to be detected each time when an abnormality is detected, and adding and averaging the error values ​​each time when an abnormality is detected to obtain a detection error value JW of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected;

[0061] S403, the detection abnormality rate and the detection error value are substituted into the calculation formula to calculate the detection force value JL of the same type of crankshaft workpiece as the crankshaft workpiece to be detected. The calculation formula is as follows:

[0062] JL=YL×a1+JW×a2; where a1 and a2 are weight coefficients with fixed values, and a1>a2;

[0063] S404, comparing the detection strength value with the detection strength threshold, determining that the detection level of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected is the third detection level, the second detection level, or the first detection level, the detection strength of the first detection level is greater than the detection strength of the second detection level, and the detection strength of the second detection level is greater than the detection strength of the third detection level;

[0064] S405, obtaining the detection force of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected according to the detection level, and the detection force of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected is the detection force of the crankshaft workpiece to be detected.

[0065] By adopting the above-mentioned preferred scheme, the historical inspection data corresponding to the crankshaft workpiece to be inspected is input according to the model, and the inspection strength of the crankshaft workpiece to be inspected is obtained based on the historical inspection data, so as to provide an adaptive inspection standard for the crankshaft workpiece, realize efficient and accurate inspection of the center distance of the automobile crankshaft balance block, and greatly improve the inspection efficiency of the crankshaft workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0067] Figure 1 It is a schematic structural diagram of an implementation manner of the detection device of the present invention.

[0068] Figure 2 It is a schematic diagram of the local structure of the main platform in the visual inspection unit.

[0069] Figure 3 It is a structural schematic diagram of the grasping mechanism in the crankshaft transfer robot.

[0070] Figure 4 It is a structural diagram of the clamping mechanism.

[0071] Figure 5 It is a flow chart of an implementation method of the detection method of the present invention.

[0072] Figure 6 It is a structural diagram of the crankshaft workpiece.

[0073] Fig. 7A This is a shadow image of the balance block at the left end of the crankshaft taken by an industrial camera.

[0074] Figure 7B This is a shadow image of the crankshaft intermediate balance block group taken by an industrial camera.

[0075] Figure 7C This is a shadow image of the balance block at the right end of the crankshaft taken by an industrial camera.

[0076] Figure 8 It is a shadow diagram of the entire crankshaft balance block after splicing.

[0077] The numbers and letters in the figure represent the names of the corresponding parts:

[0078] 10-crankshaft transfer robot; 11-multi-axis robot arm; 12-grasping mechanism; 121-installation connecting plate; 122-gripping mechanism; 1221-linear drive cylinder; 1222-hexagonal bracket; 1223-left gripper; 1224-right gripper; 1225-left first connecting rod; 1226-left second connecting rod; 1227

[0079] -left third link; 1228-right first link; 1229-right second link; 1230-right third link; 1231-linkage block; 20-visual inspection unit; 21-box; 22-main platform; 23-slide; 24-jig; 241-bottom plate; 242-V-groove plate; 243-locating pin mechanism; 25-backlight source; 26-calibration plate; 27-reciprocating transposition drive mechanism; 28-in-place sensor; 29-reinforcement bracket; 31-industrial camera; 32-telecentric lens; 33-human-computer interaction terminal; 40-crankshaft workpiece; 41-left end balance block; 42-middle balance block group; 43-right end balance block. DETAILED DESCRIPTION

[0080] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0081] like Figure 1-3 As shown, one embodiment of the present invention is: an automatic detection device for the center distance of crankshaft balance blocks based on visual measurement, such as Figure 6 As shown, the crankshaft workpiece 40 to be inspected includes a left-end balancing block 41, a right-end balancing block 43 and an intermediate balancing block group 42, and the intermediate balancing block group 42 includes two axially symmetrical balancing blocks arranged adjacent to each other;

[0082] The detection device includes:

[0083] The crankshaft transfer robot 10 includes a multi-axis robot arm 11 and a gripping mechanism 12. The gripping mechanism 12 includes a mounting connection plate 121, a first gripping jaw assembly, and a second gripping jaw assembly. The mounting connection plate 121 is mounted on the end of the multi-axis robot arm 11. The first gripping jaw assembly and the second gripping jaw assembly are respectively mounted on both sides of the mounting connection plate 121. The first gripping jaw assembly and the second gripping jaw assembly both include two gripping jaw mechanisms 122 arranged on the left and right sides.

[0084] The visual inspection unit 20 includes a box 21, a main platform 22, a slide 23, a fixture 24, a backlight source 25, a calibration plate 26, a reciprocating transposition drive mechanism 27, an in-position sensor 28, a reinforcement bracket 29, three industrial cameras 31, a telecentric lens 32, an electrical control cabinet and a human-computer interaction terminal 33. The main platform 22 is installed on the box 21, and a loading and unloading station and a detection station are provided on the main platform 22. The slide 23 is installed between the loading and unloading station and the detection station of the main platform 22; the fixture 24 can be installed on the slide 23 in a translational manner. The fixture 24 includes a bottom plate 241, two V-groove plates 242 arranged on the left and right, a positioning pin mechanism 243 and a pressure sensor. The V-groove plate 242 is used to support the crankshaft workpiece 40 to be tested. The positioning pin mechanism 243 includes a positioning pin and a jacking drive mechanism. The positioning pin is used to The crankshaft workpiece 40 is positioned, and the pressure sensor is used to detect whether the crankshaft to be tested is placed on the fixture; the reciprocating displacement drive mechanism 27 is used to drive the fixture 24 to move and displace between the loading and unloading station and the detection station, and the in-position sensor 28 is used to detect whether the fixture 24 is moved to the loading and unloading station or the detection station; the backlight source 25 and the calibration plate 26 are installed at the detection station position of the main platform 22, the backlight source 25 is located below the calibration plate 26, the reinforcement bracket 29 is installed on the box 21, and three industrial cameras 31 are installed on the reinforcement bracket 29. The three industrial cameras 31 are respectively located directly above the left end balance block, the right end balance block and the middle balance block group of the crankshaft to be tested, and the telecentric lens 32 is connected to the industrial camera 31; the electrical control cabinet is located below the main platform 22, and the human-computer interaction terminal 33 is located on the side of the box 21.

[0085] The beneficial effects of adopting the above technical solution are: the crankshaft is automatically loaded and unloaded by the crankshaft transfer robot, and the center distance of the crankshaft balance block is automatically and quickly detected by the visual inspection unit through image detection technology, with high detection accuracy, fast efficiency and good consistency, thus ensuring the quality of the crankshaft product.

[0086] In some other embodiments of the present invention, a guide groove is provided on the table surface of the main platform 22, and the slide 23 is installed in the guide groove. The beneficial effects of adopting the above technical solution are: improving the stability of the slide, ensuring the displacement accuracy of the fixture, and improving the accuracy of image detection.

[0087] like Figure 4As shown, in some other embodiments of the present invention, the clamping mechanism 122 includes a linear drive cylinder 1221, a hexagonal bracket 1222, a left clamping jaw 1223, a right clamping jaw 1224, a left first connecting rod 1225, a left second connecting rod 1226, a left third connecting rod 1227, a right first connecting rod 1228, a right second connecting rod 1229, a right third connecting rod 1230 and a linkage block 1231, the cylinder seat of the linear drive cylinder 1221 is fixedly mounted on the mounting connecting plate 121, the hexagonal bracket 1222 is connected to the cylinder seat of the linear drive cylinder 1221, the middle part of the linkage block 1231 is connected to the telescopic rod of the linear drive cylinder 1221, one end of the left first connecting rod 1225 is hinged to the left end of the linkage block 1231, and one end of the right first connecting rod 1228 is hinged to the left end of the linkage block 1231. The right end of the linkage block 1231 is hinged, the other end of the left first link 1225 is hinged to one end of the left second link 1226, the other end of the right first link 1228 is hinged to one end of the right second link 1229, the middle of the left second link 1229 is hinged to the left end of the hexagonal bracket 1222, the middle of the right second link 1229 is hinged to the right end of the hexagonal bracket 1222, the other end of the left second link 1229 is hinged to the left clamping claw 1223, the other end of the right second link 1229 is hinged to the right clamping claw 1224, one end of the left third link 1227 is hinged to the hexagonal bracket 1222, the other end of the left third link 1227 is hinged to the left clamping claw 1223, and the other end of the right third link 1230 is hinged to the right clamping claw 1224. The beneficial effect of adopting the above technical solution is that it can achieve stable grasping of the crankshaft workpiece.

[0088] like Figure 5 As shown, in one embodiment of the present invention, a method for automatically detecting the center distance of a crankshaft balance block based on visual measurement is as follows:

[0089] Step S1, calibrating the internal and external parameters of three industrial cameras;

[0090] In an embodiment of the present invention, step S1 specifically includes:

[0091] S11, turning on the backlight source, and photographing the straight line generated by the transparent calibration plate under the backlight source by adjusting the exposure of the camera;

[0092] S12, calling a camera calibration algorithm to calibrate the intrinsic parameters and extrinsic parameters of the camera, wherein the intrinsic parameters include but are not limited to focal length, principal point coordinates, and distortion coefficients, and the extrinsic parameters include but are not limited to rotation matrix and translation vector, to respectively determine the internal imaging characteristics of the camera and the position and posture of the camera in the world coordinate system;

[0093] S13, turn off the backlight source;

[0094] S14, placing a test workpiece at the inspection station, turning on the backlight source, photographing the test workpiece with an industrial camera to obtain a real-time shadow image, and analyzing the photographing performance of the industrial camera based on the real-time shadow image; wherein the test workpiece is a qualified workpiece without any error;

[0095] In an embodiment of the present invention, step S14 specifically includes:

[0096] S141, inputting a standard image of the test workpiece taken at the same viewing angle;

[0097] S142, extracting a real-time workpiece contour image of the test workpiece in the real-time image and a standard workpiece contour image of the test workpiece in the standard image according to the pixel point difference;

[0098] S143, establishing a rectangular coordinate system with the upper left corner of the standard workpiece outline drawing, and selecting any coordinate point in the standard workpiece outline drawing, while the coordinate point is on the test workpiece, and the coordinate point is calibrated as a feature point Di, i is the number of the feature point, i=1, 2, ..., n, n is a positive integer;

[0099] S144, selecting a feature point as the starting point, calculating the interval distances between the starting point and all other feature points, and using the interval distances as feature values ​​of the feature points corresponding to the starting point;

[0100] S145, similarly, selecting the next feature point as the starting point, and obtaining the feature values ​​of all feature points according to the above operation;

[0101] S146, constructing a first characteristic matrix of the standard workpiece contour map according to the characteristic values ​​of all characteristic points;

[0102] S147, similarly, according to steps S143 to S146, a second characteristic matrix of the real-time workpiece contour image is constructed;

[0103] S148, comparing the first characteristic matrix with the second characteristic matrix;

[0104] If any eigenvalue in the first characteristic matrix is ​​different from the eigenvalue at the corresponding position in the second characteristic matrix, a device abnormality signal is generated;

[0105] If all eigenvalues ​​in the first characteristic matrix are the same as the eigenvalues ​​at corresponding positions in the second characteristic matrix, a normal device signal is generated.

[0106] Step S2, the crankshaft transfer robot grabs the current crankshaft workpiece and puts it on the fixture at the loading and unloading station. When the pressure sensor detects pressure, the jacking drive mechanism drives the positioning pin to position and fix the current crankshaft workpiece; the crankshaft transfer robot returns to grab the next crankshaft workpiece;

[0107] Step S3, the reciprocating drive mechanism drives the fixture to move to the inspection station;

[0108] Step S4, after the in-place sensor detects the in-place signal of the fixture at the detection station, the backlight source is turned on, and the industrial camera takes a picture of the current crankshaft workpiece and determines the size;

[0109] Step S4 specifically includes:

[0110] S40, inputting corresponding historical detection data according to the model of the crankshaft workpiece to be detected, and obtaining the detection force of the crankshaft workpiece to be detected based on the historical detection data;

[0111] It should be specifically stated that the historical inspection data is the number of inspections of the crankshaft workpiece of the same model as the crankshaft workpiece to be inspected, the number of inspection anomalies, and the error value at each inspection anomaly;

[0112] In an embodiment of the present invention, step S40 specifically includes:

[0113] S401, obtaining the number of inspections and the number of abnormal inspections of the same type of crankshaft workpiece as the crankshaft workpiece to be inspected, and obtaining the abnormal inspection rate YL of the same type of crankshaft workpiece as the crankshaft workpiece to be inspected by dividing the number of abnormal inspections by the number of inspections;

[0114] S402, obtaining the error value of a crankshaft workpiece of the same model as the crankshaft workpiece to be detected each time when an abnormality is detected, and adding and averaging the error values ​​each time when an abnormality is detected to obtain a detection error value JW of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected;

[0115] S403, the detection abnormality rate and the detection error value are substituted into the calculation formula to calculate the detection force value JL of the same type of crankshaft workpiece as the crankshaft workpiece to be detected. The calculation formula is as follows:

[0116] JL=YL×a1+JW×a2; where a1 and a2 are weight coefficients with fixed values, and a1>a2;

[0117] S404, comparing the detection force value with the detection force threshold to determine the detection level of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected;

[0118] If the detection force value is less than the first detection force threshold, the detection level of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected is the third detection level;

[0119] If the detection force value is greater than or equal to the first detection force threshold and less than the second detection force threshold, the detection level of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected is the second detection level;

[0120] If the detection strength value is greater than or equal to the second detection strength threshold, the detection level of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected is the first detection level; wherein the first detection strength threshold is less than the second detection strength threshold, the detection strength of the first detection level is greater than the detection strength of the second detection level, and the detection strength of the second detection level is greater than the detection strength of the third detection level;

[0121] S405, obtaining the detection force of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected according to the detection level, and the detection force of the crankshaft workpiece of the same model as the crankshaft workpiece to be detected is the detection force of the crankshaft workpiece to be detected;

[0122] In specific implementation, the detection intensity can be distinguished by the number of shots of the industrial camera. For example, the number of shots of the crankshaft workpiece to be inspected corresponding to the first detection level is 5 times, the number of shots of the crankshaft workpiece to be inspected corresponding to the second detection level is 3 times, and the number of shots of the crankshaft workpiece to be inspected corresponding to the second detection level is 1 time.

[0123] S41, after the in-position sensor detects the in-position signal of the fixture at the detection station, the backlight source is turned on, and the crankshaft balance block is photographed to obtain the balance block shadow image within the depth of field of each camera (such as Fig. 7A , Figure 7B , Figure 7C shown);

[0124] S42, calling the internal and external parameters of the industrial camera determined in step S1, performing a rigid body transformation on the coordinate system of each industrial camera, converting it into a common world coordinate system and splicing it to form an overall crankshaft balance block shadow map (such as Figure 8 shown);

[0125] S43, construction of the reference measurement line for the shadow map;

[0126] Step S43 specifically includes:

[0127] S431, finding the intermediate balancing block group from the overall crankshaft balancing block shadow diagram;

[0128] S432, select four different points (x11, x11), (x12, y11), (x12, y12), (x11, y12) on both sides of the middle balancing block group, where (x11, x11) and (x12, y11) are on a horizontal line, and (x12, y12) and (x11, y12) are on a horizontal line;

[0129] S433, respectively connect the two points (x11, x11) and (x12, y11), and the two points (x12, y12) and (x11, y12) on the same horizontal line to obtain two line segments, and calculate the center point (X 01, Y 01 ) and (X 02 , Y 02 );

[0130] S434: Obtain the position coordinates (X 01 , Y 01 ) and (X 02 , Y 02 ), and construct the reference measurement line through the formula, the formula is as follows:

[0131]

[0132] That is the equation:

[0133] (y 02 -y 01 )x+(x 01 -x 02 )y+x 02 y 01 -y 02 x 01 =0;

[0134] S44: calculating the vertical distance from the constructed reference measurement line to the edge of each balancing block shadow image, and determining whether the vertical distance is within the error range, thereby determining whether a normal workpiece signal or an abnormal workpiece signal is generated;

[0135] Step S44 specifically includes:

[0136] S441, Agreement: A = Y 02 -Y 01 ; B = X 01 -X 02 ; C = X 02 Y 01 -Y 02 X 01 ;

[0137] Therefore, the equation:

[0138] (y 02 -y 01 )x+(x 01 -x 02 )y+x 02 y 01 -y 02 x 01 =0;

[0139] Evolves to: Ax+By+C=0;

[0140] S442, select two measuring points on each side of the balance block, and calculate the vertical distance dij from each measuring point on the balance block to the reference measuring line by using the formula, where i is the balance block number of the measuring point, starting from number 1, and j is two different points of the balance block of the measuring point, starting from number 1. The specific formula is as follows:

[0141]

[0142] S443, respectively obtain the vertical distance from each side of the balancing block to the reference measurement line, and take the average value as the final vertical distance of the balancing block center distance detection. If the vertical distance is within the error range, the crankshaft workpiece to be detected is determined to be a qualified part, and a workpiece normal signal is generated. If the vertical distance is not within the error range, the crankshaft workpiece to be detected is determined to be an unqualified part, and a workpiece abnormal signal is generated;

[0143] Step S5, the reciprocating drive mechanism drives the fixture to move to the loading and unloading station;

[0144] Step S6, the crankshaft transfer robot grabs the current crankshaft workpiece that has been inspected, then rotates 180°, places the next crankshaft workpiece on the fixture, and then rotates 180° again and moves to the set position to place the current crankshaft workpiece that has been inspected.

[0145] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. The automatic detection device for the center distance of crankshaft balance block based on visual measurement is characterized in that: include: A crankshaft transfer robot, comprising a multi-axis mechanical arm and a gripping mechanism, wherein the gripping mechanism comprises a mounting connection plate, a first gripping jaw assembly and a second gripping jaw assembly, wherein the mounting connection plate is mounted at the end of the multi-axis mechanical arm, the first gripping jaw assembly and the second gripping jaw assembly are respectively mounted on both sides of the mounting connection plate, and the first gripping jaw assembly and the second gripping jaw assembly both comprise two gripping jaw mechanisms arranged on the left and right sides; The visual inspection unit comprises a box, a main platform, a slide, a fixture, a backlight source, a calibration plate, a reciprocating transposition drive mechanism, an in-position sensor, a reinforcement bracket, three industrial cameras, a telecentric lens, an electrical control cabinet and a human-computer interaction terminal. The main platform is installed in the box, and a loading and unloading station and a detection station are provided on the main platform. The slide is installed between the loading and unloading station and the detection station on the main platform; the fixture can be installed on the slide in a translational manner, and the fixture comprises a bottom plate, two V-groove plates arranged on the left and right, a positioning pin mechanism and a pressure sensor, the V-groove plate is used to support the crankshaft workpiece to be tested, the positioning pin mechanism comprises a positioning pin and a jacking drive mechanism, the positioning pin is used to position the crankshaft workpiece to be tested, and the pressure sensor The sensor is used to detect whether the crankshaft to be tested is placed on the fixture; the reciprocating transposition drive mechanism is used to drive the fixture to move and transpose between the loading and unloading station and the detection station, and the in-position sensor is used to detect whether the fixture is moved to the loading and unloading station or the detection station; the backlight source and the calibration plate are installed at the detection station position of the main platform, the backlight source is located below the calibration plate, the reinforcement bracket is installed on the box, and the three industrial cameras are installed on the reinforcement bracket. The three industrial cameras are respectively located directly above the left end balance block, the right end balance block and the middle balance block group of the crankshaft to be tested, and the telecentric lens is connected to the industrial camera; the electrical control cabinet is located below the main platform, and the human-computer interaction terminal is located on the side of the box.

2. The automatic detection device for crankshaft balance block center distance based on visual measurement according to claim 1 is characterized in that: The clamping mechanism includes a linear drive cylinder, a hexagonal bracket, a left clamping jaw, a right clamping jaw, a left first connecting rod, a left second connecting rod, a left third connecting rod, a right first connecting rod, a right second connecting rod, a right third connecting rod and a linkage block. The cylinder seat of the linear drive cylinder is fixedly mounted on the mounting connecting plate, the hexagonal bracket is connected to the cylinder seat of the linear drive cylinder, the middle part of the linkage block is connected to the telescopic rod of the linear drive cylinder, one end of the left first connecting rod is hinged to the left end of the linkage block, one end of the right first connecting rod is hinged to the right end of the linkage block, and the left The other end of the first connecting rod is hinged to one end of the left second connecting rod, the other end of the right first connecting rod is hinged to one end of the right second connecting rod, the middle part of the left second connecting rod is hinged to the left end of the hexagonal bracket, the middle part of the right second connecting rod is hinged to the right end of the hexagonal bracket, the other end of the left second connecting rod is hinged to the left clamping claw, the other end of the right second connecting rod is hinged to the right clamping claw, one end of the left third connecting rod is hinged to the hexagonal bracket, the other end of the left third connecting rod is hinged to the left clamping claw, and the other end of the right third connecting rod is hinged to the right clamping claw.

3. The automatic detection method of crankshaft balance block center distance based on visual measurement is characterized in that: The automatic detection device for the center distance of crankshaft balance blocks based on visual measurement as claimed in claim 1 comprises the following steps: Step S1, calibrating the internal and external parameters of three industrial cameras; Step S1 specifically includes: S11, turning on the backlight source, and photographing the straight line generated by the transparent calibration plate under the backlight source by adjusting the exposure of the camera; S12, calling a camera calibration algorithm to calibrate the intrinsic parameters and extrinsic parameters of the camera, wherein the intrinsic parameters include but are not limited to focal length, principal point coordinates, and distortion coefficients, and the extrinsic parameters include but are not limited to rotation matrix and translation vector, to respectively determine the internal imaging characteristics of the camera and the position and posture of the camera in the world coordinate system; S13, turn off the backlight source; Step S2, the crankshaft transfer robot grabs the current crankshaft workpiece and puts it on the fixture at the loading and unloading station. When the pressure sensor detects pressure, the jacking drive mechanism drives the positioning pin to position and fix the current crankshaft workpiece; the crankshaft transfer robot returns to grab the next crankshaft workpiece; Step S3, the reciprocating drive mechanism drives the fixture to move to the inspection station; Step S4, after the in-place sensor detects the in-place signal of the fixture at the detection station, the backlight source is turned on, and the industrial camera takes a picture of the current crankshaft workpiece and determines the size; Step S4 specifically includes: S41, after the in-position sensor detects the in-position signal of the fixture at the detection station, the backlight source is turned on, and the crankshaft balance block is started to be photographed to obtain a shadow image of the balance block within the depth of field of each camera; S42, calling the internal and external parameters of the industrial camera determined in step S1, performing a rigid body transformation on the coordinate system of each industrial camera, converting it into a common world coordinate system and splicing them to form an overall crankshaft balancing block shadow map; S43, construction of the reference measurement line for the shadow map; Step S43 specifically includes: S431, finding the intermediate balancing block group from the overall crankshaft balancing block shadow diagram; S432, select four different points (x11, x11), (x12, y11), (x12, y12), (x11, y12) on both sides of the middle balancing block group, where (x11, x11) and (x12, y11) are on a horizontal line, and (x12, y12) and (x11, y12) are on a horizontal line; S433, respectively connect the two points (x11, x11) and (x12, y11), and the two points (x12, y12) and (x11, y12) on the same horizontal line to obtain two line segments, and calculate the center point (X 01 , Y 01 ) and (X 02 , Y 02 ); S434: Obtain the position coordinates (X 01 , Y 01 ) and (X 02 , Y 02 ), and construct the reference measurement line through the formula, the formula is as follows: That is the equation: (and 02 -and 01 )x+(x 01 -x 02 )y+x 02 and 01 -and 02 x 01 =0; S44: calculating the vertical distance from the constructed reference measurement line to the edge of each balancing block shadow image, and determining whether the vertical distance is within the error range, thereby determining whether a normal workpiece signal or an abnormal workpiece signal is generated; Step S44 specifically includes: S441,Right:A:Y 02 -Y 01 ;B=X 01 -X 02 ;C=X 02 Y 01 -Y 02 X 01 4 Therefore, the equation: (and 02 -and 01 )x+(x 01 -x 02 )y+x 02 and 01 -and 02 x 01 =0; Evolves to: Ax+By+C=0; S442, select two measuring points on each side of the balance block, and calculate the vertical distance dij from each measuring point on the balance block to the reference measuring line by using the formula, where i is the balance block number of the measuring point, starting from number 1, and j is two different points of the balance block of the measuring point, starting from number 1. The specific formula is as follows: S443, respectively obtain the vertical distance from each side of the balancing block to the reference measurement line, and take the average value as the final vertical distance of the balancing block center distance detection. If the vertical distance is within the error range, the crankshaft workpiece to be detected is determined to be a qualified part, and a workpiece normal signal is generated. If the vertical distance is not within the error range, the crankshaft workpiece to be detected is determined to be an unqualified part, and a workpiece abnormal signal is generated; Step S5, the reciprocating transposition drive mechanism drives the fixture to move to the loading and unloading station; Step S6, the crankshaft transfer robot grabs the current crankshaft workpiece that has been inspected, then rotates 180°, places the next crankshaft workpiece on the fixture, and then rotates 180° again and moves to the set position to place the current crankshaft workpiece that has been inspected.

Images