CN102825365B - Automatic tracking system and method of welding line based on capacitive transducer - Google Patents
Automatic tracking system and method of welding line based on capacitive transducer Download PDFInfo
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- CN102825365B CN102825365B CN201210335472.3A CN201210335472A CN102825365B CN 102825365 B CN102825365 B CN 102825365B CN 201210335472 A CN201210335472 A CN 201210335472A CN 102825365 B CN102825365 B CN 102825365B
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Abstract
The invention discloses an automatic tracking system and an automatic tracking method of a welding line based on a capacitive transducer. The technical points of the automatic tracking system are as follows: the automatic tracking system comprises a welding gun arranged on a cross slide frame; the cross slide frame is fixedly connected to a wheeled robot car; the cross slide frame is connected with a stepper motor; the stepper motor is connected with a control system; the control system is connected with a lower computer liquid crystal screen control panel; a mechanical arm is fixedly connected with the welding gun; the capacitive transducer is fixedly connected with an extension end of the mechanical arm; a certain distance is kept between a measuring head of the capacitive transducer and a welded work-piece, and the measuring head and the welded work-piece are regarded as two pole plates of the capacitive transducer; the capacitive transducer is connected to a capacitive transducer conversion circuit, and the capacitive transducer conversion circuit is connected to the control system through a capacitive voltage conversion circuit, a full-wave rectifier circuit and a gain filter circuit orderly. The automatic tracking system is low in cost, good in instantaneity, high in sensitivity and accuracy, and good in stability.
Description
Technical field
The invention belongs to welding autocontrol technical field, be specifically related to a kind of seam tracking system based on capacitance type sensor and method.
Background technology
Capacitance type sensor is a kind of tested mechanical quantity, as displacement, pressure etc. are converted to the sensor of electric capacitance change.Its non-sensitive part is exactly the capacitor with variable element.Since the end of the seventies, along with the development of integrated circuit technique, occur and the capacitance type sensor that miniature measuring instrument is packaged together.This novel sensor can make the impact of distribution capacity greatly reduce, and the shortcoming making it intrinsic is overcome.Capacitance type sensor is that a kind of purposes is extremely wide, has very much the sensor of development potentiality.
The change-over circuit of the capacitance type sensor of existing report mainly contains:
(1) bridge circuit: by an arm of capacitance sensor incoming transport electric bridge or two alternate arms, another two-arm can be resistance or electric capacity or inductance, also can be two secondary coils of transformer.During measurement, measured change causes sensor capacitance change to cause electric bridge unbalance, and bridge output voltage changes.
(2) difference pulse adjusts stretch circuit: be differential pulse width modulation circuit again, utilizing makes the width of circuit output pulse change with capacitance sensor volume change to the discharge and recharge of sensor capacitance, just can be obtained the direct current signal of corresponding measured change by low pass filter.
(3) FM circuit: sensor capacitance is accessed in oscillator LC resonant tank, as the part in loop, the change of capacitance is converted to the change of circuit oscillation frequency, thus measured change can be obtained by measuring frequency.
(4) transporting discharging type measuring circuit: accessed by sensor capacitance in amplifier, as the feedback element of amplifier, then inputs constant AC signal at amplifier input, so output signal voltage controls by feedback capacity.Because this connection output signal and sensor capacitance are inverse relations, be particularly suitable for type polar distance variable capacitance sensor.
To the research of capacitance type sensor at weld joint tracking, mainly concentrate on and extract the technical of deviation signal.For the application technology of capacitance type sensor in weld joint tracking, not yet find the research carrying out this respect at present.
Summary of the invention
First object of the present invention is to provide that a kind of cost is low, real-time good, sensitivity and accuracy is high, the seam tracking system based on capacitance type sensor of good stability.
First object of the present invention realizes by the following technical solutions: should based on the seam tracking system of capacitance type sensor, and comprise the welding gun be installed on cross balladeur train, cross balladeur train is fixed on wheeled robot dolly; Described cross balladeur train is connected with stepper motor, and stepper motor is connected with control system, and control system is connected with slave computer liquid crystal display control panel; Described welding gun is fixed with a mechanical arm, the external part of mechanical arm is fixed with a capacitance type sensor, maintains a certain distance and be regarded as two pole plates of capacitance sensor between the gauge head of capacitance type sensor and welded piece; Described capacitance type sensor is connected on capacitance type sensor change-over circuit, and capacitance type sensor change-over circuit is connected in described control system by capacitance-voltage conversion circuit, full-wave rectifying circuit, Gain filter circuit successively.
More particularly, described capacitance type sensor change-over circuit adopts difference pulse to adjust stretch circuit.
Or described capacitance type sensor change-over circuit adopts transporting discharging type measuring circuit.Wherein, capacitance type sensor adopts complete equivalent potential screen circuits mask distribution capacity.
Described capacitance type sensor adopts differential polar distance formula capacitance sensor; Described differential polar distance formula capacitance sensor has three pole plates, and wherein two maintain static, and only have middle plate to produce mobile, welded piece is regarded as middle Mobile pole plate.
The gauge head of described capacitance type sensor adopts ring plate.
The second object of the present invention is the automatic seam tracking method providing the above-mentioned seam tracking system based on capacitance type sensor, the method is, wheeled robot dolly controls welding gun and presses operative orientation advance, welding gun presents certain position orientation relation with the movement of wheeled robot dolly and workpiece to be welded, also certain change in location is presented between the capacitance type sensor gauge head be connected by mechanical arm and welding gun and workpiece, the change that reaction is amassed for spacing between capacitance type sensor gauge head and workpiece or effective right opposite, thus cause the change of capacitance type sensor voltage; Capacitance type sensor collects weld seam transverse direction and vertical deviation signal by the change of its voltage, after capacitance type sensor change-over circuit, capacitance-voltage conversion circuit, full-wave rectifying circuit, Gain filter processing of circuit signal, be sent to control system microcomputer and carry out digital filtering and software process, according to real-time the adjusting cross balladeur train and wheeled robot dolly of operation result control system, thus realize welding gun deviation adjusting, carry out weld joint tracking, complete automatic welding.
Described capacitance type sensor change-over circuit adopts difference pulse to adjust stretch circuit or transporting discharging type measuring circuit to measure capacitance sensor voltage signal and extract.
Described capacitance type sensor adopts differential polar distance formula capacitance sensor, in butt welded seam tracing process, the change of the spacing of transducer probe assembly and welded piece is measured, thus nonlinear error reduction, improve sensitivity, eliminate temperature and the drift caused by other interference; Described differential polar distance formula capacitance sensor has three pole plates, and wherein two maintain static, and only have middle plate to produce mobile, welded piece is regarded as middle Mobile pole plate.
The gauge head of described capacitance type sensor adopts ring plate, is used for improving sensor electrical capacitance and sensitivity.
The principle of the invention is, the formula according to electric capacity: C=ε S/d
Wherein, ε is dielectric dielectric constant between two-plate, and S is the effective area of two-plate, and d is the distance between two-plate.
When two other condition is constant, electric capacity is large and reduce with the change of polar plate spacing, the increase long-pending with effective right opposite and increasing, and changes with the change of dielectric constant.Utilize this characteristic of electric capacity, we can be an electric capacity between the gauge head of illusion capacitance type sensor and processing work.When distance, effective area or intermediate dielectric change between the two, electric capacity changes immediately.Utilize some auxiliary circuits, the position relationship between capacitance type sensor gauge head and workpiece can be obtained.
Capacitance type sensor for soldering joint automatic tracking, is had that real-time is good, control accuracy is high, low cost and other advantages by the present invention, solves current soldering joint automatic tracking complex structure, control accuracy is low, real-time is bad series of problems.The present invention is proved by actual welding engineer testing, and tracking effect is good, and stable and reliable operation is practical.
Accompanying drawing explanation
Fig. 1 is the system principle structural representation of the embodiment of the present invention.
Fig. 2 is the position orientation relation schematic diagram between capacitance type sensor gauge head and welded piece, wherein, and schematic diagram when figure (a) is welding gun centering, schematic diagram when figure (b) is welding gun left avertence, schematic diagram when figure (c) is welding gun right avertence.
Fig. 3 is that difference pulse adjusts stretch circuit figure.
Fig. 4 is that difference pulse adjusts each point voltage oscillogram in stretch circuit, and wherein, figure (a) works as C
1=C
xtime oscillogram, figure (b) work as C
1≠ C
x, and C
x>C
1time oscillogram.
Fig. 5 is the signal processing circuit model calling block diagram that difference pulse adjusts stretch circuit.
Fig. 6 is the perspective view of capacitance type sensor ring plate.
Fig. 7 is differential polar distance formula capacitance sensor measuring method schematic diagram.
Fig. 8 is transporting discharging type measuring circuit figure.
Fig. 9 is the electrical block diagram that transporting discharging type measuring circuit figure adopts complete equal potential screening technique.
Detailed description of the invention
Below in conjunction with drawings and Examples, the present invention is described in further detail.
See Fig. 1, in the embodiment of the present invention, welding gun 1 is installed on cross balladeur train 2, and cross balladeur train 2 is fixed on wheeled robot dolly 3; As can be seen from Fig. 1, cross balladeur train 2 is connected with stepper motor and by driving stepper motor, welding gun 1 is also horizontally slipped with cross balladeur train 2.Be also shown in from Fig. 1, stepper motor is connected with control system and controls it by control system and operates, and control system is also connected with slave computer liquid crystal display control panel, provides a personal-machine interactive operation interface thus.Welding gun 1 is fixed with mechanical arm 4, the external part of mechanical arm 4 is fixed with capacitance type sensor, maintains a certain distance between the gauge head 5 of capacitance type sensor and welded piece 6; Capacitance type sensor is connected to difference pulse and adjusts on stretch circuit, and difference pulse adjusts stretch circuit to be connected in control system by capacitance-voltage conversion circuit, full-wave rectifying circuit, Gain filter circuit successively.
Composition graphs 2 is the position orientation relation schematic diagrames between capacitance type sensor gauge head and welded piece.From the principle of the invention, capacitance type sensor is connected with welding gun by mechanical arm, presents certain position and posture with welded piece, when welding gun moves left and right relative to welded piece, show as the change of d between capacitance sensor gauge head and workpiece, thus change electric capacity C
tvalue.
See Fig. 3, be the circuit diagram that the present embodiment difference pulse adjusts stretch circuit, for recording electric capacity C
tchange, utilize difference pulse adjust stretch circuit measure.The extraction utilizing difference pulse to adjust stretch circuit to carry out capacitance sensor signal, it comprises comparator A
1, A
2, flip and flop generator and basic electric capacity C
1(immobilizing), sensor capacitance C
x(measurement electric capacity) and diode D
1, D
2, resistance R
7, R
8the charging and discharging circuit etc. of composition.R is begun through when Q end jumps to high level from zero
7to sensor C
xduring charging, its voltage equation is:
Wherein, U
efor the high potential of trigger; U
rfor the given voltage of comparator; τ
1for time constant.U
emake C
xbe charged to U
rtime T
1for:
In like manner can obtain electric capacity C
1charging interval T
2for:
Simultaneous can obtain:
Work as R
7=R
8during=R:
As can be seen from the above equation, C
1known, then output voltage U
aBwith measured capacitance C
xbetween have certain corresponding relation.Work as C
1=C
xtime, on circuit, each point waveform voltage signal is as shown in Fig. 4 (a), and the average voltage of A, B point-to-point transmission equals zero.Work as C
1≠ C
x, and C
x>C
1time, timeconstantτ
1=R
7c
x> τ
2=R
8c
1.Due to the change of discharge and recharge time constant, in circuit, each point voltage waveform produces corresponding change.Circuit each point voltage waveform is as shown in Fig. 4 (b).
Because capacitance type sensor is measured inconvenient, and welding process is comparatively complicated, the present embodiment devises adjusts stretch circuit by above-mentioned difference pulse, also have capacitance-voltage conversion circuit, the whole wave circuit of full stream and adopt the signal processing circuit of three amplifier high cmrr amplifying circuits and a joint Active RC low pass active filter circuit composition, the signal effect after process is fairly obvious.It is above-mentioned signal processing circuit model calling block diagram shown in Fig. 5.And output voltage is after the signal transacting of convert of capacitor to voltage, full-wave rectification and Gain filter links, obtain the signal that can be input to control system.
In actual applications, considering that the initial capacitance value formed after two parallel plate electrodes are deployed in same plane is less, is the sensitivity improving sensor, has to add the initial capacitance value of large sensor.This realizes by strengthening polar plate area usually, which increases the physical dimension of system.If ensure sensitivity by reducing sensor plate spacing, for range again by directly limiting.Therefore, also particular design is carried out to the shape of sensor plate, as shown in Figure 6, it is the loop sensor pole plate that the present invention adopts, utilize the surface texture of circuit software for drawing Protel to capacitive battery capacity sensor gauge head and pole plate to draw, utilize the transducer probe assembly perspective view that virtual printing program print is drawn, generate software ArtCAM by numerical control G code and generate the G code that can be used for engraving machine digital control processing, utilize and cover copper thickness and be divided into 0.8 ~ 3.2mm(containing Cu) copper-clad plate carry out the engraving of transducer probe assembly.Correlation experience shows, under equal area, the electrode structure of complicated shape is compared with simple monolithic electric capacity, and the sensor electrical capacitance of complicated shape electrode and sensitivity are all larger.
In addition, because polar distance formula capacitance sensor characteristic is nonlinear, the change that we can adopt the structure of differential polar distance formula capacitance sensor to carry out the spacing of transducer probe assembly and welded piece in butt welded seam tracing process is measured.See Fig. 7, it is differential polar distance formula capacitance sensor measuring method schematic diagram.As can be seen from Fig. 7, it has three pole plates, and wherein two maintain static, and only have middle plate to produce movement, welded piece can be considered middle Mobile pole plate.When middle Mobile pole plate is in equilbrium position, i.e. d
1+ d
2=d
0, then C
1+ C
2=C
0if Mobile pole plate moves right Δ d, then d
1=d
0-Δ d, d
2=d
0+ Δ d.After metering system makes differential type into by polar distance formula, not only nonlinearity erron reduces greatly, and sensitivity also improves one times.Have employed differential amplify technology, the drift caused by temperature and other interference can be eliminated.
Experimentally, adopt differential Capacitive Displacement Sensor structure, utilize difference pulse to adjust stretch circuit to measure.Measure the change of output voltage when capacitance sensor moving plate often moves a certain distance Δ d, as shown in table 1.
Table 1 displacement measurement test data
And based on theory, measure capacitance type sensor and can also utilize transporting discharging type measuring circuit, as shown in Figure 8.Obtained by circuit theory:
Output voltage U
0linear with sensor plate gap d, solve from principle the nonlinear problem using single Varied clearance formula capacitance sensor output characteristics; U
0with driving source voltage U
i, reference capacitance C
0and other parameter ε, the S of sensor are relevant, the fluctuation of these parameters will make output produce error.
Sensor measured capacitance only has a few pF usually, and the distribution capacity read of cable core and screen layer generally has tens even hundreds of pF, is difficult to measure measured capacitance.For solving the adverse effect of distribution capacity, sensor adopts complete equal potential screening technique, as shown in Figure 9.Wherein, A
1for the multiplication factor of preamplifier; A
2for the multiplication factor of driving amplifier; A
3for the multiplication factor of main amplifier.
According to derivation, can obtain additional capacitor is
If A
1a
3=10000, C
in=300pf, then △ C is very little, can meet required precision completely.
The automatic seam tracking method that the present invention is based on the seam tracking system of above-mentioned capacitance type sensor is: capacitance type sensor is arranged on welding gun by mechanical arm, and welding gun is arranged in the tracking executing agency that is made up of cross balladeur train, wheeled robot dolly.Welding gun presents certain position orientation relation with the movement of wheeled robot dolly and workpiece, the capacitance type sensor gauge head connected by mechanical arm also presents certain change in location between welded piece, the change that reaction is amassed for spacing or effective right opposite, thus affect the change of capacitance voltage, process sending into control system after the voltage obtained after filtering circuit filtering amplification, real-time cross balladeur train and wheeled robot dolly are adjusted of control system, thus carry out soldering joint automatic tracking.Present system pad is deviation signal collection point, and side weld edge fit is followed the tracks of, and real-time is very good.
Claims (4)
1. based on a seam tracking system for capacitance type sensor, comprise the welding gun be installed on cross balladeur train, cross balladeur train is fixed on wheeled robot dolly; Described cross balladeur train is connected with stepper motor, and stepper motor is connected with control system, and control system is connected with slave computer liquid crystal display control panel; Described welding gun is fixed with a mechanical arm, the external part of mechanical arm is fixed with a capacitance type sensor, maintains a certain distance and be regarded as two pole plates of capacitance sensor between the gauge head of capacitance type sensor and welded piece; Described capacitance type sensor is connected on capacitance type sensor change-over circuit, and capacitance type sensor change-over circuit is connected in described control system by capacitance-voltage conversion circuit, full-wave rectifying circuit, Gain filter circuit successively; Described capacitance type sensor change-over circuit adopts difference pulse to adjust stretch circuit or transporting discharging type measuring circuit; It is characterized in that: described capacitance type sensor adopts differential polar distance formula capacitance sensor; Described differential polar distance formula capacitance sensor has three pole plates, and wherein two maintain static, and only have middle plate to produce mobile, welded piece is regarded as middle Mobile pole plate.
2. the seam tracking system based on capacitance type sensor according to claim 1, is characterized in that: the gauge head of described capacitance type sensor adopts ring plate.
3. the automatic seam tracking method based on the seam tracking system of capacitance type sensor as claimed in claim 1, wheeled robot dolly controls welding gun and presses operative orientation advance, welding gun presents certain position orientation relation with the movement of wheeled robot dolly and workpiece to be welded, also certain change in location is presented between the capacitance type sensor gauge head be connected by mechanical arm and welding gun and workpiece, the change that reaction is amassed for spacing between capacitance type sensor gauge head and workpiece or effective right opposite, thus cause the change of capacitance type sensor voltage; Capacitance type sensor collects weld seam transverse direction and vertical deviation signal by the change of its voltage, after capacitance type sensor change-over circuit, capacitance-voltage conversion circuit, full-wave rectifying circuit, Gain filter processing of circuit signal, be sent to control system microcomputer and carry out digital filtering and software process, according to real-time the adjusting cross balladeur train and wheeled robot dolly of operation result control system, thus realize welding gun deviation adjusting, carry out weld joint tracking, complete automatic welding; Described capacitance type sensor change-over circuit adopts difference pulse to adjust stretch circuit or transporting discharging type measuring circuit to measure capacitance sensor voltage signal and extract; It is characterized in that: described capacitance type sensor adopts differential polar distance formula capacitance sensor, in butt welded seam tracing process, the change of the spacing of transducer probe assembly and welded piece is measured, thus nonlinear error reduction, improve sensitivity, eliminate temperature and the drift caused by other interference; Described differential polar distance formula capacitance sensor has three pole plates, and wherein two maintain static, and only have middle plate to produce mobile, welded piece is regarded as middle Mobile pole plate.
4. the automatic seam tracking method of the seam tracking system based on capacitance type sensor according to claim 3, is characterized in that: the gauge head of described capacitance type sensor adopts ring plate, is used for improving sensor electrical capacitance and sensitivity.
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|---|---|---|---|
| CN201210335472.3A CN102825365B (en) | 2012-09-12 | 2012-09-12 | Automatic tracking system and method of welding line based on capacitive transducer |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210335472.3A CN102825365B (en) | 2012-09-12 | 2012-09-12 | Automatic tracking system and method of welding line based on capacitive transducer |
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| CN102825365A CN102825365A (en) | 2012-12-19 |
| CN102825365B true CN102825365B (en) | 2015-03-25 |
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| CN103551709B (en) * | 2013-11-16 | 2015-04-22 | 沈阳工业大学 | Welding joint forming detection device and method for A-TIG welding |
| CN104181907B (en) * | 2014-08-18 | 2016-09-28 | 如冈自动化控制技术(上海)有限公司 | The numerical control tracker on non contact metal gap and surface and tracking |
| CN104959706B (en) * | 2015-07-10 | 2018-02-23 | 湘潭大学 | The welding seam tracking method of plate sheet welding swing type edge effect capacitance sensor |
| CN105127632A (en) * | 2015-08-07 | 2015-12-09 | 中国石油天然气集团公司 | Method and device for controlling welding gun |
| CN107848055A (en) * | 2016-02-15 | 2018-03-27 | 叶成源 | Welding system and its welding method based on manipulator and measuring arm |
| CN105798426B (en) * | 2016-04-07 | 2018-02-02 | 湘潭大学 | A kind of condenser type narrow gap weld seam tracking transducer |
| CN105665981B (en) * | 2016-04-19 | 2017-11-07 | 湘潭大学 | A kind of rotated edge electric capacity weld seam tracking sensor |
| CN106247920B (en) * | 2016-07-07 | 2019-02-12 | 中国计量大学 | A kind of surface strain detection device based on the sandwich interdigital capacitor of elastic substrates |
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| CN107478145B (en) * | 2017-09-05 | 2019-05-21 | 湘潭大学 | A kind of tip formula multi-pole capacitance sensor of welding gun pose detection |
| CN109570859A (en) * | 2019-01-09 | 2019-04-05 | 湘潭大学 | Welding gun pose identifying system based on electric inductance array sensor |
| CN109719369B (en) * | 2019-02-26 | 2021-01-05 | 湘潭大学 | Welding seam tracking method for multi-pole capacitance sensing magnetic control real-time deviation correction |
| CN110031026B (en) * | 2019-04-17 | 2021-07-02 | 安菲腾(常州)光电科技有限公司 | Capacitance position sensor detection circuit |
| CN113787247B (en) * | 2021-09-24 | 2022-11-11 | 潍坊新松机器人自动化有限公司 | Welding tracking device and tracking method thereof |
| CN117102701B (en) * | 2023-10-24 | 2024-03-26 | 上海方菱计算机软件有限公司 | Compensation control method and device for groove cutting height, electronic equipment and storage medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2829851A1 (en) * | 1978-07-07 | 1980-01-24 | Precitec Gmbh | ARRANGEMENT FOR MEASURING THE DISTANCE BETWEEN A METAL WORKPIECE AND A MACHINING TOOL |
| DE3664277D1 (en) * | 1985-02-08 | 1989-08-17 | Elektroniktechnologie Get | Measuring arrangement using a capacitive electrode and machine tool with integrated electrode |
| EP0303563A3 (en) * | 1987-06-11 | 1990-03-28 | C.A. Weidmüller GmbH & Co. | Sensor device with a compensation arrangement |
| JP3944718B2 (en) * | 2002-06-28 | 2007-07-18 | 澁谷工業株式会社 | Article processing equipment |
| CN100593767C (en) * | 2006-06-30 | 2010-03-10 | 深圳市大族激光科技股份有限公司 | Control method of capacity transducer |
| CN102615390B (en) * | 2012-04-28 | 2013-12-25 | 湘潭大学 | Swing arc-based multi-layer and multi-channel weld tracking system and identification method thereof |
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