CN105241380A - Visual detection method for zigzag screw thread - Google Patents

Visual detection method for zigzag screw thread Download PDF

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Publication number
CN105241380A
CN105241380A CN201510646229.7A CN201510646229A CN105241380A CN 105241380 A CN105241380 A CN 105241380A CN 201510646229 A CN201510646229 A CN 201510646229A CN 105241380 A CN105241380 A CN 105241380A
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China
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straight line
thread
point
detected
work piece
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CN201510646229.7A
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Chinese (zh)
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张俊峰
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Guangzhou Supersonic Automation Technology Co Ltd
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Guangzhou Supersonic Automation Technology Co Ltd
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Priority to CN201510646229.7A priority Critical patent/CN105241380A/en
Publication of CN105241380A publication Critical patent/CN105241380A/en
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Abstract

The invention relates to a visual detection method for a zigzag screw thread. The method includes the following steps: setting a template contour characteristic for a standard screw thread workpiece; setting a contour characteristic for a to-be-detected screw thread workpiece; and determining whether the similarity of the template contour characteristic of the standard screw thread workpiece and the contour characteristic of the to-be-detected screw thread workpiece reaches a preset value and meets the target number, identifying that the to-be-detected screw thread workpiece is qualified and further detecting whether all parameters of the to-be-detected screw thread workpiece accord with standards if the similarity reaches the preset value and meets the target number, otherwise, identifying that the to-be-detected screw thread workpiece is unqualified and discarding the screw thread workpiece. Multi-layer detection is performed by means of the characteristics of a trapezoid screw thread, and through comparison between a real workpiece and a standard workpiece, the method can guarantee high precision detection, and is high in efficiency and high in reliability.

Description

Saw-tooth thread visible detection method
Technical field
The present invention relates to thread measurement technical field, particularly relate to saw-tooth thread visible detection method.
Background technology
Along with the fast development of industrial technology, the automaticity of mechanical hook-up is more and more higher, also requires more and more higher to the workpiece accuracy in the manufacturing in this process.
The main method that traditional thread quality detects is ring thread gage or feeler gauge, measures, with gear tooth vernier calliper measurement, three-needle measuring method, crosspointer mensuration with screw-thread micrometer, there is the determination that measuring speed is slow, measuring accuracy is low in this measuring method, be unfavorable for the Aulomatizeted Detect speed that streamline is provided, can not meet the requirement that modern industry double thread workpiece quality measures the aspect such as efficiency and precision.
Summary of the invention
For above-mentioned technical matters, the object of the present invention is to provide saw-tooth thread visible detection method, it is high that it detects the whorl work piece precision obtained.
For achieving the above object, the present invention adopts following technical scheme:
Saw-tooth thread visible detection method, comprises the steps:
Step one: template contours feature is set up to standard thread workpiece;
Step 2: contour feature is set up to whorl work piece to be detected;
Step 3: whether the similarity of the contour feature of the template contours characteristic sum workpiece to be detected of criterion workpiece reaches preset value and meet target number, if, then assert that whorl work piece to be detected is tentatively qualified, perform step 4, otherwise, assert that whorl work piece to be detected is defective, abandon this whorl work piece to be detected;
Step 4: the thread contour feature setting up whorl work piece both sides to be detected, the center line L between the thread obtaining whorl work piece both sides to be detected according to the thread contour feature of these both sides, this thread contour feature has multiple thread;
Step 5: with center line L for reference axis sets up two-dimensional direct angle coordinate system to obtain all coordinate points set (X1 of the thread contour feature of whorl work piece both sides to be detected, Y1), obtain all coordinate points set (X1, Y1) the maximum value Ymax of Y1 and all coordinate points set (X1 in, Y1) the minimal value Ymin of Y1 in, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set A of all coordinate points in maximum value Ymax preset range, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set B of all coordinate points in maximum value Ymin preset range, set A and maximum value Ymax are fitted to straight line M1, set B and minimal value Ymin are fitted to straight line M2, and ask for Major Diam d, diameter of thread d1 and pitch diameter of thread d2 according to straight line M1 and straight line M2,
Step 6: obtain straight line L3 and straight line L4 according to center line L, and ask for pitch p with the intersection point of thread contour feature respectively according to straight line L3, straight line L4, described straight line L3 and straight line L4 is parallel to center line L respectively, center line L is between straight line L3 and straight line L4, and the distance of straight line L3 and straight line L4 and center line L is the half of the pitch diameter of thread;
Step 7: obtain valley point m1, the valley point m2 of any thread both sides, peak point m3, the peak point m4 of this thread and straight line T1, the first square area is generated to fit to straight line L5 according to valley point m1 and peak point m3, the second square area is generated to fit to straight line L6 according to valley point m2 and peak point m3, judge whether the angle α 1 between straight line L5 and straight line T1 and the angle α 2 between straight line L6 and straight line T1 meets preset range respectively, if, then this whorl work piece to be detected is qualified, otherwise, defective; Wherein, described peak point m3 is an end points near valley point m1 on straight line M1, described peak point m4 is an end points near valley point m2 on straight line M1, valley point m1 is the end points near straight line M1 side on straight line M2, valley point m2 is the end points near straight line M1 opposite side on straight line M2, and described straight line T1 is vertical with the straight line M2 at valley point m2 place.
Preferably, described step one comprises following sub-step:
Step 1.1: the gray scale picture obtaining standard thread workpiece, and a region of search is chosen on gray scale picture;
Step 1.2: contrast the contrast between neighbor in region of search, forms template contours feature when contrast is greater than the first preset value;
Step 1.3: the first angular range change preset template contours feature, obtains a series of module profile feature;
Step 1.4: the template contours feature of preserving series.
Preferred further, described first preset value is 40, and described the first default angular range is ± 0.5 °.
Preferably, described step 2 comprises following sub-step:
Step 2.1: the gray scale picture obtaining whorl work piece to be detected, and a region of search is chosen on gray scale picture;
Step 2.2: contrast the contrast between neighbor in region of search, forms contour feature when contrast is greater than the second preset value;
Step 2.3: the second angular range change preset contour feature, obtains a series of contour feature;
Step 2.4: the contour feature preserving series.
Preferred further, described second preset value is 20, and described the second default angular range is ± 0.5 °.
Preferably, preset value described in step 3 is 75%, and target number is 1.
Preferably, step 4.1: the thread contour feature setting up whorl work piece both sides to be detected, this thread has multiple thread;
Step 4.2: the thread contour feature processing whorl work piece to be detected wherein side, to form closed contour D1, processes the thread contour feature of whorl work piece opposite side to be detected to form closed contour D2;
Step 4.3: to be in line L1 according to least square fitting closed contour D1, to be in line L2 according to least square fitting closed contour D2 simultaneously;
Step 4.4: the center line L between the thread obtaining whorl work piece both sides to be detected according to straight line L1 and straight line L2, wherein, the distance of straight line L1 to center line L equals the distance of straight line L2 to center line L.
Preferred further, step 5 comprises following sub-step:
Step 5.1: with center line L for reference axis sets up two-dimensional direct angle coordinate system to obtain all coordinate points set (X1, Y1) of the thread contour feature of whorl work piece both sides to be detected;
Step 5.2: scan all coordinate points set (X1, Y1) this all coordinate points set (X1 is obtained, Y1) the maximum value Ymax of Y1 and all coordinate points set (X1 in, Y1) the minimal value Ymin of Y1 in, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set A of all coordinate points in maximum value Ymax preset range, and the Y1 obtained in all coordinate points set in (X1, Y1) is greater than or less than the set B of all coordinate points in minimal value Ymin preset range;
Step 5.3: set A and maximum value Ymax are fitted to straight line M1, fits to straight line M2 by set B and minimal value Ymin, and the distance K1 calculated between straight line M1 and center line L and the distance K2 between straight line M2 and center line L;
Step 5.4: try to achieve Major Diam d according to formula d=2*K1, tries to achieve diameter of thread d1 according to formula d1=2*K2, tries to achieve pitch diameter of thread d2 according to formula d2=(d+d1)/2.
Preferred further, step 6 comprises following sub-step:
Step 6.1: obtain straight line L3 and straight line L4 according to center line L, described straight line L3 and straight line L4 is parallel to center line L respectively, and center line L is between straight line L3 and straight line L4, and the distance of straight line L3 and straight line L4 and center line L is the half of pitch diameter of thread d2;
Step 6.2: described straight line L3 and straight line L4 forms multiple intersection point with the thread contour feature of center line L both sides respectively, select three of the arbitrary neighborhood of any side intersection points to be designated as intersection point a, intersection point b and intersection point c, the distance of described intersection point a to intersection point c is pitch p.
Preferred further, step 7 comprises following sub-step:
Step 7.1: choose any one thread, obtain the valley point m1 of these thread both sides, valley point m2, peak point m3, the peak point m4 of this thread and straight line T1, wherein, described peak point m3 is an end points near valley point m1 on straight line M1, described peak point m4 is an end points near valley point m2 on straight line M1, valley point m1 is the end points near straight line M1 side on straight line M2, valley point m2 is the end points near straight line M1 opposite side on straight line M2, and described straight line T1 is vertical with the straight line M2 at valley point m2 place;
Step 7.2: ask for the mid point h1 between valley point m1 and peak point m3 according to valley point m1 and peak point m3, asks for the mid point h2 between valley point m2 and peak point m4 according to valley point m2 and peak point m4;
Step 7.3: point centered by mid point h1, with the half of valley point m1 to peak point m3 distance for radius generates the first square area, point centered by mid point h2 simultaneously, with the half of valley point m2 to peak point m4 distance for radius generates the second square area;
Step 7.4: set up the first profile in the first square area and fit to straight line L5, sets up the second profile in the second square area and fits to straight line L6;
Step 7.5: judge whether the angle α 1 between straight line L5 and straight line T1 and the angle α 2 between straight line L6 and straight line T1 meets preset range respectively, and if so, then this whorl work piece to be detected is qualified, otherwise, defective.
Compared to existing technology, beneficial effect of the present invention is:
1, without the need to survey instrument size manually, avoid the systematic error that manual operation and surveying instrument self bring, achieve Aulomatizeted Detect;
2, the feature in conjunction with saw-tooth thread carries out multilayer detection, is compared by entity workpiece and standard workpiece, and have high precision test and ensure, measuring method efficiency is high, reliability is strong.
Accompanying drawing explanation
Fig. 1 is the screwed tooth structure schematic diagram of saw-tooth thread of the present invention;
Fig. 2 is the workflow diagram of saw-tooth thread visible detection method of the present invention.
Embodiment
Below, by reference to the accompanying drawings and embodiment, the present invention is described further:
As shown in Figure 1, the major parameter of saw-tooth thread has the thread shape of saw-tooth thread: Major Diam d, diameter of thread d1, pitch diameter of thread d2, pitch p, thread form angle α 1 and thread form angle α 2.The saw-tooth thread visible detection method that the present embodiment provides detects layer by layer based on to above-mentioned parameter, satisfactory, proves that this acme thread is qualified workpiece, if there is any one parameter defective, this saw-tooth thread workpiece is substandard product.
See Fig. 2, it is as follows that the present embodiment comprises step:
Step s1: template contours feature is set up to standard thread workpiece;
Step s2: contour feature is set up to whorl work piece to be detected;
Step s3: whether the similarity of the contour feature of the template contours characteristic sum workpiece to be detected of criterion workpiece reaches preset value and meet target number, if, then assert that whorl work piece to be detected is tentatively qualified, perform step s4, otherwise, assert that whorl work piece to be detected is defective, abandon this whorl work piece to be detected; The effect of target number weighs whorl work piece whether to mate qualified necessary condition, target number is the contour feature number that will find, can be 1, the preset value of both similarities is 75%, namely when the similarity of the contour feature of the template contours characteristic sum workpiece to be detected of standard workpiece reaches 75% and target number meets 1, it is qualified to be, if defective, then select other whorl work pieces to restart to measure, only have and detect qualified product in this step and just perform next step;
Step s4: the thread contour feature setting up whorl work piece both sides to be detected, the center line L between the thread obtaining whorl work piece both sides to be detected according to the thread contour feature of these both sides, this thread contour feature has multiple thread;
Step s5: with center line L for reference axis sets up two-dimensional direct angle coordinate system to obtain all coordinate points set (X1 of the thread contour feature of whorl work piece both sides to be detected, Y1), obtain all coordinate points set (X1, Y1) the maximum value Ymax of Y1 and all coordinate points set (X1 in, Y1) the minimal value Ymin of Y1 in, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set A of all coordinate points in maximum value Ymax preset range, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set B of all coordinate points in maximum value Ymin preset range, set A and maximum value Ymax are fitted to straight line M1, set B and minimal value Ymin are fitted to straight line M2, and ask for Major Diam d, diameter of thread d1 and pitch diameter of thread d2 according to straight line M1 and straight line M2,
Step s6: obtain straight line L3 and straight line L4 according to center line L, and ask for pitch p with the intersection point of thread contour feature respectively according to straight line L3, straight line L4, described straight line L3 and straight line L4 is parallel to center line L respectively, center line L is between straight line L3 and straight line L4, and the distance of straight line L3 and straight line L4 and center line L is the half of the pitch diameter of thread;
Step s7: obtain valley point m1, the valley point m2 of any thread both sides, peak point m3, the peak point m4 of this thread and straight line T1, the first square area is generated to fit to straight line L5 according to valley point m1 and peak point m3, the second square area is generated to fit to straight line L6 according to valley point m2 and peak point m3, judge whether the angle α 1 between straight line L5 and straight line T1 and the angle α 2 between straight line L6 and straight line T1 meets preset range respectively, if, then this whorl work piece to be detected is qualified, otherwise, defective; Wherein, described peak point m3 is an end points near valley point m1 on straight line M1, described peak point m4 is an end points near valley point m2 on straight line M1, valley point m1 is the end points near straight line M1 side on straight line M2, valley point m2 is the end points near straight line M1 opposite side on straight line M2, and described straight line T1 is vertical with the straight line M2 at valley point m2 place.
Wherein, the process of establishing of step s1 and step s2 is similar, in step s1, comprises sub-step as follows:
S1.1: the gray scale picture obtaining standard thread workpiece, and a region of search is chosen on gray scale picture; Obtain the gray scale picture of standard thread workpiece by acquisitions of taking pictures, the gray scale picture of the picture of tentatively taking pictures not necessarily black and white, but subsequent treatment for convenience, gained picture processing of taking pictures the most at last is gray scale picture;
S1.2: contrast the contrast between neighbor in region of search, forms template contours feature when contrast is greater than the first preset value; Way of contrast in this step adopts halcon algorithm to carry out contrast level parameter process, when contrast is greater than the first preset value, then forms point, multiple point is connected to form template contours feature; The first preset value about contrast can regulate setting voluntarily according to display screen matrix other actual conditions not equal, and this first preset value in the present embodiment is preferably 40;
S1.3: the first angular range change preset template contours feature, obtains a series of module profile feature; This angular range preset is ± 0.5 °; Obtain a series of contour feature to the angle change that template contours feature is preset, namely in the certain limit of certain angle value, a series of module profile feature is exactly a lot of profiles, as circle, straight line, circular arc etc.;
S1.4: the template contours feature of preserving series.
It is as follows that s2 step comprises sub-step:
S2.1: the gray scale picture obtaining whorl work piece to be detected, and a region of search is chosen on gray scale picture;
S2.2: contrast the contrast between neighbor in region of search, forms contour feature when contrast is greater than the second preset value; Equally, way of contrast adopts halcon algorithm to carry out contrast level parameter process, and this second preset value is preferably 20;
S2.3: the second angular range change preset contour feature, obtains a series of contour feature; This second angular range preset is ± 0.5 °
S2.4: the contour feature preserving series.
Step s1 to step s3 treats detector tube screw thread to carry out rough detection, and step s4 to step s7 is that the various parameters by treating detector tube screw thread detect, to judge whether to meet standard.
It is as follows that step s4 comprises step:
S4.1: the thread contour feature setting up whorl work piece both sides to be detected, this thread contour feature has multiple thread;
S4.2: the thread contour feature processing whorl work piece to be detected wherein side, to form closed contour D1, processes the thread contour feature of whorl work piece opposite side to be detected to form closed contour D2; Processing mode can adopt halcon algorithm to carry out contrast level parameter process equally and form contour feature point, connects these contour feature points and forms closed contour;
S4.3: to be in line L1 according to least square fitting closed contour D1, to be in line L2 according to least square fitting closed contour D2 simultaneously; The working method of least square method is prior art;
S4.4: the center line L between the thread obtaining whorl work piece both sides to be detected according to straight line L1 and straight line L2, wherein, the distance of straight line L1 to center line L equals the distance of straight line L2 to center line L.
Step s5 comprises following sub-step:
S5.1: with center line L for reference axis sets up two-dimensional direct angle coordinate system to obtain all coordinate points set (X1, Y1) of the thread contour feature of whorl work piece both sides to be detected; In this step, with center line L for namely reference axis is that setting up a set of straight line perpendicular to center line L is Y-axis at two-dimensional direct angle coordinate system center line L for X-axis, form rectangular coordinate system;
S5.2: scan all coordinate points set (X1, Y1) this all coordinate points set (X1 is obtained, Y1) the maximum value Ymax of Y1 and all coordinate points set (X1 in, Y1) the minimal value Ymin of Y1 in, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set A of all coordinate points in maximum value Ymax preset range, and the Y1 obtained in all coordinate points set in (X1, Y1) is greater than or less than the set B of all coordinate points in minimal value Ymin preset range, according to zigzag shape facility, with reference to Fig. 1, each thread has upper and lower two straight lines (line segment), suppose to start from left to right to scan all coordinate points set (X1, Y1), be in the state increased progressively in the process of the left end of the line of that above scanning always, maximum value Ymax is reached after reaching this point, continue scanning, on this line, the Y1 value of all coordinates is equal to maximum value Ymax or close size, described preset range is minimum scope, if scope is too large, these points connect then can not form straight line, after scanning the low order end of this line, start to successively decrease, set A be then on this line high order end to all coordinate points of low order end, set B in like manner, by foregoing description, set B be below on that line high order end to all coordinate points of low order end,
S5.3: set A and maximum value Ymax are fitted to straight line M1, fits to straight line M2 by set B and minimal value Ymin, and the distance K1 calculated between straight line M1 and center line L and the distance K2 between straight line M2 and center line L;
S5.4: try to achieve Major Diam d according to formula d=2*K1, tries to achieve diameter of thread d1 according to formula d1=2*K2, tries to achieve pitch diameter of thread d2 according to formula d2=(d+d1)/2.In this step, because there are a lot of threads, each thread all has above-mentioned parameter, in order to better ensure accuracy of detection, between all Major Diam d, compare between diameter of thread d1, between pitch diameter of thread d2, see tried to achieve parameter whether in error range, if have indivedual compared with other parameters difference too large, illustrate that this workpiece is defective, such as, in all Major Diam d, the value of one of them Major Diam d much larger than the value of other Major Diams d, then judges that this screw thread to be detected is defective;
Step s6 comprises following sub-step:
S6.1: obtain straight line L3 and straight line L4 according to center line L, described straight line L3 and straight line L4 is parallel to center line L respectively, and center line L is between straight line L3 and straight line L4, and the distance of straight line L3 and straight line L4 and center line L is the half of pitch diameter of thread d2;
S6.2: described straight line L3 and straight line L4 forms multiple intersection point with the thread contour feature of center line L both sides respectively, select three of the arbitrary neighborhood of any side intersection points to be designated as intersection point a, intersection point b and intersection point c, the distance of described intersection point a to intersection point c is pitch p.
Step s7 comprises following sub-step:
S7.1: choose any one thread, obtain the valley point m1 of these thread both sides, valley point m2, peak point m3, the peak point m4 of this thread and straight line T1, wherein, described peak point m3 is an end points near valley point m1 on straight line M1, described peak point m4 is an end points near valley point m2 on straight line M1, valley point m1 is the end points near straight line M1 side on straight line M2, valley point m2 is the end points near straight line M1 opposite side on straight line M2, and described straight line T1 is vertical with the straight line M2 at valley point m2 place; In this step, the position of valley point m1, valley point m2, peak point m3, peak point m4 and straight line T1 can refer to Fig. 1;
S7.2: ask for the mid point h1 between valley point m1 and peak point m3 according to valley point m1 and peak point m3, asks for the mid point h2 between valley point m2 and peak point m4 according to valley point m2 and peak point m4;
S7.3: point centered by mid point h1, with the half of valley point m1 to peak point m3 distance for radius generates the first square area, point centered by mid point h2 simultaneously, with the half of valley point m2 to peak point m4 distance for radius generates the second square area;
S7.4: set up the first profile in the first square area and fit to straight line L5, sets up the second profile in the second square area and fits to straight line L6;
S7.5: judge whether the angle α 1 between straight line L5 and straight line T1 and the angle α 2 between straight line L6 and straight line T1 meets preset range respectively, and if so, then this whorl work piece to be detected is qualified, otherwise, defective.Namely angle α 1 is thread form angle α 1, namely angle α 2 is thread form angle α 2, saw-tooth thread has two thread form angle, looks like equally with step s5.5, and each thread has two thread form angle, contrast all angle α 1, when having indivedual angle α 1 and other angles α 1 to have notable difference, illustrating that this whorl work piece to be detected is defective, is namely when the quite close also no significant difference of all angle α 1, also tackle than all angle α 2, only have two thread form angle all to meet preset range just qualified.
To one skilled in the art, according to technical scheme described above and design, other various corresponding change and deformation can be made, and all these change and deformation all should belong within the protection domain of the claims in the present invention.

Claims (10)

1. saw-tooth thread visible detection method, is characterized in that, comprises the steps:
Step one: template contours feature is set up to standard thread workpiece;
Step 2: contour feature is set up to whorl work piece to be detected;
Step 3: whether the similarity of the contour feature of the template contours characteristic sum workpiece to be detected of criterion workpiece reaches preset value and meet target number, if, then assert that whorl work piece to be detected is tentatively qualified, perform step 4, otherwise, assert that whorl work piece to be detected is defective, abandon this whorl work piece to be detected;
Step 4: the thread contour feature setting up whorl work piece both sides to be detected, the center line L between the thread obtaining whorl work piece both sides to be detected according to the thread contour feature of these both sides, this thread contour feature has multiple thread;
Step 5: with center line L for reference axis sets up two-dimensional direct angle coordinate system to obtain all coordinate points set (X1 of the thread contour feature of whorl work piece both sides to be detected, Y1), obtain all coordinate points set (X1, Y1) the maximum value Ymax of Y1 and all coordinate points set (X1 in, Y1) the minimal value Ymin of Y1 in, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set A of all coordinate points in maximum value Ymax preset range, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set B of all coordinate points in maximum value Ymin preset range, set A and maximum value Ymax are fitted to straight line M1, set B and minimal value Ymin are fitted to straight line M2, and ask for Major Diam d, diameter of thread d1 and pitch diameter of thread d2 according to straight line M1 and straight line M2,
Step 6: obtain straight line L3 and straight line L4 according to center line L, and ask for pitch p with the intersection point of thread contour feature respectively according to straight line L3, straight line L4, described straight line L3 and straight line L4 is parallel to center line L respectively, center line L is between straight line L3 and straight line L4, and the distance of straight line L3 and straight line L4 and center line L is the half of the pitch diameter of thread;
Step 7: obtain valley point m1, the valley point m2 of any thread both sides, peak point m3, the peak point m4 of this thread and straight line T1, the first square area is generated to fit to straight line L5 according to valley point m1 and peak point m3, the second square area is generated to fit to straight line L6 according to valley point m2 and peak point m3, judge whether the angle α 1 between straight line L5 and straight line T1 and the angle α 2 between straight line L6 and straight line T1 meets preset range respectively, if, then this whorl work piece to be detected is qualified, otherwise, defective; Wherein, described peak point m3 is an end points near valley point m1 on straight line M1, described peak point m4 is an end points near valley point m2 on straight line M1, valley point m1 is the end points near straight line M1 side on straight line M2, valley point m2 is the end points near straight line M1 opposite side on straight line M2, and described straight line T1 is vertical with the straight line M2 at valley point m2 place.
2. saw-tooth thread visible detection method as claimed in claim 1, it is characterized in that, described step one comprises following sub-step:
Step 1.1: the gray scale picture obtaining standard thread workpiece, and a region of search is chosen on gray scale picture;
Step 1.2: contrast the contrast between neighbor in region of search, forms template contours feature when contrast is greater than the first preset value;
Step 1.3: the first angular range change preset template contours feature, obtains a series of module profile feature;
Step 1.4: the template contours feature of preserving series.
3. saw-tooth thread visible detection method as claimed in claim 2, it is characterized in that, described first preset value is 40, and described the first default angular range is ± 0.5 °.
4. saw-tooth thread visible detection method as claimed in claim 1, it is characterized in that, described step 2 comprises following sub-step:
Step 2.1: the gray scale picture obtaining whorl work piece to be detected, and a region of search is chosen on gray scale picture;
Step 2.2: contrast the contrast between neighbor in region of search, forms contour feature when contrast is greater than the second preset value;
Step 2.3: the second angular range change preset contour feature, obtains a series of contour feature;
Step 2.4: the contour feature preserving series.
5. saw-tooth thread visible detection method as claimed in claim 4, it is characterized in that, described second preset value is 20, and described the second default angular range is ± 0.5 °.
6. buttless thread visible detection method as claimed in claim 1, it is characterized in that, preset value described in step 3 is 75%, and target number is 1.
7. saw-tooth thread visible detection method as claimed in claim 1, it is characterized in that, step 4 comprises following sub-step:
Step 4.1: the thread contour feature setting up whorl work piece both sides to be detected, this thread has multiple thread;
Step 4.2: the thread contour feature processing whorl work piece to be detected wherein side, to form closed contour D1, processes the thread contour feature of whorl work piece opposite side to be detected to form closed contour D2;
Step 4.3: to be in line L1 according to least square fitting closed contour D1, to be in line L2 according to least square fitting closed contour D2 simultaneously;
Step 4.4: the center line L between the thread obtaining whorl work piece both sides to be detected according to straight line L1 and straight line L2, wherein, the distance of straight line L1 to center line L equals the distance of straight line L2 to center line L.
8. saw-tooth thread visible detection method as claimed in claim 7, it is characterized in that, step 5 comprises following sub-step:
Step 5.1: with center line L for reference axis sets up two-dimensional direct angle coordinate system to obtain all coordinate points set (X1, Y1) of the thread contour feature of whorl work piece both sides to be detected;
Step 5.2: scan all coordinate points set (X1, Y1) this all coordinate points set (X1 is obtained, Y1) the maximum value Ymax of Y1 and all coordinate points set (X1 in, Y1) the minimal value Ymin of Y1 in, and obtain (X1 in all coordinate points set, Y1) Y1 in is greater than or less than the set A of all coordinate points in maximum value Ymax preset range, and the Y1 obtained in all coordinate points set in (X1, Y1) is greater than or less than the set B of all coordinate points in minimal value Ymin preset range;
Step 5.3: set A and maximum value Ymax are fitted to straight line M1, fits to straight line M2 by set B and minimal value Ymin, and the distance K1 calculated between straight line M1 and center line L and the distance K2 between straight line M2 and center line L;
Step 5.4: try to achieve Major Diam d according to formula d=2*K1, tries to achieve diameter of thread d1 according to formula d1=2*K2, tries to achieve pitch diameter of thread d2 according to formula d2=(d+d1)/2.
9. saw-tooth thread visible detection method as claimed in claim 8, it is characterized in that, step 6 comprises following sub-step:
Step 6.1: obtain straight line L3 and straight line L4 according to center line L, described straight line L3 and straight line L4 is parallel to center line L respectively, and center line L is between straight line L3 and straight line L4, and the distance of straight line L3 and straight line L4 and center line L is the half of pitch diameter of thread d2;
Step 6.2: described straight line L3 and straight line L4 forms multiple intersection point with the thread contour feature of center line L both sides respectively, select three of the arbitrary neighborhood of any side intersection points to be designated as intersection point a, intersection point b and intersection point c, the distance of described intersection point a to intersection point c is pitch p.
10. saw-tooth thread visible detection method as claimed in claim 9, it is characterized in that, step 7 comprises following sub-step:
Step 7.1: choose any one thread, obtain the valley point m1 of these thread both sides, valley point m2, peak point m3, the peak point m4 of this thread and straight line T1, wherein, described peak point m3 is an end points near valley point m1 on straight line M1, described peak point m4 is an end points near valley point m2 on straight line M1, valley point m1 is the end points near straight line M1 side on straight line M2, valley point m2 is the end points near straight line M1 opposite side on straight line M2, and described straight line T1 is vertical with the straight line M2 at valley point m2 place;
Step 7.2: ask for the mid point h1 between valley point m1 and peak point m3 according to valley point m1 and peak point m3, asks for the mid point h2 between valley point m2 and peak point m4 according to valley point m2 and peak point m4;
Step 7.3: point centered by mid point h1, with the half of valley point m1 to peak point m3 distance for radius generates the first square area, point centered by mid point h2 simultaneously, with the half of valley point m2 to peak point m4 distance for radius generates the second square area;
Step 7.4: set up the first profile in the first square area and fit to straight line L5, sets up the second profile in the second square area and fits to straight line L6;
Step 7.5: judge whether the angle α 1 between straight line L5 and straight line T1 and the angle α 2 between straight line L6 and straight line T1 meets preset range respectively, and if so, then this whorl work piece to be detected is qualified, otherwise, defective.
CN201510646229.7A 2015-09-30 2015-09-30 Visual detection method for zigzag screw thread Pending CN105241380A (en)

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