Device and method for automatic detection of crankshaft balance block center distance based on visual measurement

Abstract

The present invention provides an automatic detection device and method for the center distance of a crankshaft balance block based on visual measurement. The detection device includes a crankshaft transfer robot and a visual detection unit; the crankshaft transfer robot includes a multi-axis robotic arm and a gripping mechanism, the gripping mechanism includes a mounting connection plate, and a first clamping assembly and a second clamping assembly distributed at 180 degrees; the visual detection unit includes 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, an industrial camera, a telecentric lens, an electrical control cabinet, and a human-computer interaction terminal. The present invention uses a crankshaft transfer robot to automatically load and unload the crankshaft, and uses a visual detection unit to automatically and quickly detect the center distance of the crankshaft balance block using image detection technology. The detection has high accuracy, high efficiency, and good consistency, thereby ensuring the quality of the crankshaft product.

Description

Technical Field

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

[0002] The crankshaft is the core component of the engine, converting the linear reciprocating motion of the pistons into rotational motion and outputting this power in a unified manner. To balance the centrifugal force and torque of rotation, counterweights (also called balancing weights) are installed on the crankshaft. The number, size, and placement of the counterweights are determined based on 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 balancing weights is incorrect during the manufacturing process, the crankshaft may become unbalanced, causing increased engine vibration, increased component wear, and shortened engine life. This can lead to vehicle instability, reduced driving safety, and increased driving risks. Therefore, to ensure proper engine operation and vehicle performance, the center distance of the crankshaft balancing weights must meet design requirements and remain correct.

[0003] Currently, the center distance of crankshaft balance blocks in automotive crankshaft parts processing workshops is often inspected manually using pallets. This is not only time-consuming and labor-intensive, but also has a large margin of error, making product consistency uncertain and extremely tiring for workers when inspecting large quantities of crankshafts. Some factories currently use Zeiss CMMs for inspection, but this is not only expensive, time-consuming, and inefficient. Summary of the Invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the purpose 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] To achieve the above-mentioned purpose, the present invention solves the technical problem by adopting a technical solution: 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 robotic arm and a gripping mechanism, wherein the gripping mechanism comprises a mounting plate, a first gripping assembly, and a second gripping assembly. The mounting plate is mounted on the end of the multi-axis robotic arm, and the first gripping assembly and the second gripping assembly are mounted on either side of the mounting plate, respectively. The first gripping assembly and the second gripping assembly each comprise two gripping mechanisms disposed on the left and right sides.

[0007] The visual inspection unit includes 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 includes a bottom plate, two V-grooved plates arranged on the left and right, a positioning pin mechanism and a pressure sensor. The V-grooved plate is used to support the crankshaft workpiece to be tested, and the positioning pin mechanism includes a positioning pin and a jacking drive mechanism. The positioning pin is used to position the crankshaft workpiece to be tested. The sensor is used to detect whether the crankshaft to be tested is placed on the jig; the reciprocating displacement drive mechanism is used to drive the jig to move and displace between the loading and unloading station and the detection station, and the in-position sensor is used to detect whether the jig 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, fast efficiency and good consistency, ensuring the quality of the crankshaft product.

[0009] Furthermore, a guide groove is provided 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 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 includes 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 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, respectively determining 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 places it on the fixture at the loading and unloading station. When the pressure sensor detects pressure, the lifting 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-position sensor detects the in-position 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 its 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 cameras 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 together 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) on the same horizontal line, and connect 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 ), the reference measurement line is constructed by the formula, which 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: Calculate the vertical distance from the constructed reference measurement line to the edge of the shadow image of each balance block, and determine 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 measurement points on each side of the balance block and calculate the vertical distance dij from each measurement point on the balance block to the reference measurement line using the formula, where i is the balance block number of the measurement point, starting from 1, and j is the number of two different balance block measurement points, starting from 1. The formula is as follows:

[0040]

[0041] S443: 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 for the balancing block center distance test. If the vertical distance is within the error range, the crankshaft workpiece to be tested is considered qualified and a workpiece normal signal is generated. If the vertical distance is not within the error range, the crankshaft workpiece to be tested is considered unqualified 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] In step S6, the crankshaft transfer robot grabs the current crankshaft workpiece that has been inspected, then rotates 180° to place 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, and 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 based on pixel point differences;

[0049] S143, establishing a rectangular coordinate system with the upper left corner of the standard workpiece outline drawing, and randomly selecting a coordinate point in the standard workpiece outline drawing, while the coordinate point is on the test workpiece, and calibrating the coordinate point as a feature point Di, where i is the number of the feature point, i = 1, 2, ..., n, where 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 the feature values ​​of the feature points corresponding to the starting point;

[0051] S145: Similarly, select the next feature point as the starting point, and obtain the feature values ​​of all feature points according to the above operation;

[0052] S146, constructing a first characteristic matrix of the standard workpiece contour image based on 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 further 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 a crankshaft workpiece of the same model as the crankshaft workpiece to be inspected, and obtaining the abnormal inspection rate YL of the crankshaft workpiece of the same model as the crankshaft workpiece to be inspected by dividing the number of abnormal inspections by the number of inspections;

[0060] S402, obtaining an error value of a crankshaft workpiece of the same model as the crankshaft workpiece to be detected each time an abnormality is detected, and summing up the error values ​​of each abnormality detection to obtain an average value 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 crankshaft workpiece of the same model 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: Compare the detection force value with a detection force threshold value to determine whether 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, and determine that the detection force of the first detection level is greater than the detection force of the second detection level, and the detection force of the second detection level is greater than the detection force of the third detection level;

[0064] S405 , obtaining a detection force of a 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 force of the crankshaft workpiece to be inspected is obtained based on the historical inspection data, and an adaptive inspection standard is provided for the crankshaft workpiece, thereby realizing efficient and accurate inspection of the center distance of the automobile crankshaft balance block, and greatly improving 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0067] Figure 1 It is a structural schematic diagram of an embodiment 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 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 embodiment of the detection method of the present invention.

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

[0073] Figure 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 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 robotic arm; 12-grasping mechanism; 121-mounting 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-Base plate; 242-V-groove plate; 243-Locking pin mechanism; 25-Backlight source; 26-Calibration plate; 27-Reciprocating transposition drive mechanism; 28-In-position 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 clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall 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. 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 robotic arm 11 and a gripping mechanism 12. The gripping mechanism 12 includes a mounting plate 121, a first gripping assembly, and a second gripping assembly. The mounting plate 121 is mounted on the end of the multi-axis robotic arm 11. The first gripping assembly and the second gripping assembly are respectively mounted on either side of the mounting plate 121. The first gripping assembly and the second gripping assembly each include two gripping mechanisms 122 disposed 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. The main platform 22 is provided with a loading and unloading station and a detection station. 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-grooved plates 242 arranged on the left and right, a positioning pin mechanism 243 and a pressure sensor. The V-grooved 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 jig; the reciprocating displacement drive mechanism 27 is used to drive the jig 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 jig 24 has 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, ensuring the quality of the crankshaft product.

[0086] In other embodiments of the present invention, the main platform 22 is provided with a guide groove, 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 left first connecting rod 1225 is hinged to the right end of the linkage block 1231, the other end of the left first connecting rod 1225 is hinged to one end of the left second connecting rod 1226, the other end of the right first connecting rod 1228 is hinged to one end of the right second connecting rod 1229, the middle part of the left second connecting rod 1229 is hinged to the left end of the hexagonal bracket 1222, the middle part of the right second connecting rod 1229 is hinged to the right end of the hexagonal bracket 1222, the other end of the left second connecting rod 1229 is hinged to the left clamping jaw 1223, the other end of the right second connecting rod 1229 is hinged to the right clamping jaw 1224, one end of the left third connecting rod 1227 is hinged to the hexagonal bracket 1222, the other end of the left third connecting rod 1227 is hinged to the left clamping jaw 1223, and the other end of the right third connecting rod 1230 is hinged to the right clamping jaw 1224. The above technical solution has the beneficial effect of enabling stable gripping 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 crankshaft balance blocks 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 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, respectively determining 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, and 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 based on pixel point differences;

[0098] S143, establishing a rectangular coordinate system with the upper left corner of the standard workpiece outline drawing, and randomly selecting a coordinate point in the standard workpiece outline drawing, while the coordinate point is on the test workpiece, and calibrating the coordinate point as a feature point Di, where i is the number of the feature point, i = 1, 2, ..., n, where 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 the feature values ​​of the feature points corresponding to the starting point;

[0100] S145: Similarly, select the next feature point as the starting point, and obtain the feature values ​​of all feature points according to the above operation;

[0101] S146, constructing a first characteristic matrix of the standard workpiece contour image based on 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 places it on the fixture at the loading and unloading station. When the pressure sensor detects pressure, the lifting 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-position sensor detects the in-position 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 its 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 noted that the historical inspection data is the number of inspections of the same model of crankshaft workpiece 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 a crankshaft workpiece of the same model as the crankshaft workpiece to be inspected, and obtaining the abnormal inspection rate YL of the crankshaft workpiece of the same model as the crankshaft workpiece to be inspected by dividing the number of abnormal inspections by the number of inspections;

[0114] S402, obtaining an error value of a crankshaft workpiece of the same model as the crankshaft workpiece to be detected each time an abnormality is detected, and summing up the error values ​​of each abnormality detection to obtain an average value 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 crankshaft workpiece of the same model 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 force value is greater than or equal to 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 first detection level; wherein the first detection force threshold is less than the second detection force threshold, the detection force of the first detection level is greater than the detection force of the second detection level, and the detection force of the second detection level is greater than the detection force of the third detection level;

[0121] S405, obtaining the detection force of a crankshaft workpiece of the same model as the crankshaft workpiece to be detected based on 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 Figure 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) on the same horizontal line, and connect 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 ), the reference measurement line is constructed by the formula, which 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: Calculate the vertical distance from the constructed reference measurement line to the edge of the shadow image of each balance block, and determine 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 measurement points on each side of the balance block and calculate the vertical distance dij from each measurement point on the balance block to the reference measurement line using the formula, where i is the balance block number of the measurement point, starting from 1, and j is the number of two different balance block measurement points, starting from 1. The formula is as follows:

[0141]

[0142] S443: 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 for the balancing block center distance test. If the vertical distance is within the error range, the crankshaft workpiece to be tested is considered qualified and a workpiece normal signal is generated. If the vertical distance is not within the error range, the crankshaft workpiece to be tested is considered unqualified 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] In step S6, the crankshaft transfer robot grabs the current crankshaft workpiece that has been inspected, then rotates 180° to place 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. Their purpose is to enable ordinary technicians in this field to understand the content of the present invention and implement it. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. The automatic detection device for the center distance of crankshaft balance blocks based on visual measurement is characterized by: include: A crankshaft transfer robot, comprising a multi-axis robotic arm and a gripping mechanism, wherein the gripping mechanism comprises a mounting plate, a first gripping assembly, and a second gripping assembly. The mounting plate is mounted on the end of the multi-axis robotic arm, and the first gripping assembly and the second gripping assembly are mounted on either side of the mounting plate, respectively. The first gripping assembly and the second gripping assembly each comprise two gripping mechanisms disposed on the left and right sides. The visual inspection unit includes 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 includes a bottom plate, two V-grooved plates arranged on the left and right, a positioning pin mechanism and a pressure sensor. The V-grooved plate is used to support the crankshaft workpiece to be tested, and the positioning pin mechanism includes a positioning pin and a jacking drive mechanism. The positioning pin is used to position the crankshaft workpiece to be tested. 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 has 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, the three industrial cameras are installed on the reinforcement bracket, and 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; 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 map within the depth of field of each camera. The predetermined internal and external parameters of the industrial camera are called, and the coordinate system of each industrial camera is rigidly transformed and converted into a common world coordinate system and spliced ​​to form an overall crankshaft balance block shadow map. The reference measurement line of the shadow map is constructed, and the vertical distance from the constructed reference measurement line to the edge of the shadow map of each balance block is calculated. It is determined whether the vertical distance is within the error range, thereby determining whether a normal workpiece signal or an abnormal workpiece signal is generated.

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. 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 jaw, the other end of the right second connecting rod is hinged to the right clamping jaw, 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 jaw, and the other end of the right third connecting rod is hinged to the right clamping jaw.

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, turn on the backlight source, and shoot the straight line generated by the transparent calibration plate under the backlight source by adjusting the camera exposure; S12, calling a camera calibration algorithm to calibrate the intrinsic 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, respectively determining 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 places it on the fixture at the loading and unloading station. When the pressure sensor detects pressure, the lifting 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-position sensor detects the in-position 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 its 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 cameras 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 together 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 (x12, y12) and (x11, y12) on the same horizontal line to obtain two line segments, and calculate the center point of the line segment (X 01 , Y 01 ) and (X 02 , Y 02 ); S434: Obtain the position coordinates of the two sets of center points (X 01 , Y 01 ) and (X 02 , Y 02 ), the benchmark measurement line is constructed by the formula, the formula is as follows: ； That is the equation: ； S44: calculating the vertical distance from the constructed reference measurement line to the edge of the shadow image of each balance block, and determining whether the vertical distance falls within the error range, thereby determining whether a normal workpiece signal or an abnormal workpiece signal is generated; Step S44 specifically includes: S441,A=Y 02 -Y 01 (B=X 01 -X 02 ;C=X 02 Y 01 -Y 02 X 01 4 Therefore, the equation: ； Evolves to: Ax+By+C=0; S442: Select two measurement points on each side of the balance block and calculate the vertical distance dij from each measurement point on the balance block to the reference measurement line using the formula, where i is the balance block number of the measurement point, starting from 1, and j is the number of two different balance block measurement points, starting from 1. The formula is as follows: ； In step S443, the vertical distances from each side of the balancing block to the reference measurement line are obtained, and the average value thereof is taken as the final vertical distance for the balancing block center distance test. If the vertical distances fall within the error range, the crankshaft workpiece to be tested is determined to be qualified, and a workpiece normal signal is generated. If the vertical distances do not fall within the error range, the crankshaft workpiece to be tested is determined to be unqualified, and a workpiece abnormal signal is generated. Step S5: The reciprocating drive mechanism drives the fixture to move to the loading and unloading station; In step S6, the crankshaft transfer robot grabs the current crankshaft workpiece that has been inspected, then rotates 180° to place 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