APPROVAL AND TESTING PROCEDURES FOR CABLE ASSEMBLY

Description

Technical area

[0001] The invention relates to a cable assembly system and a testing method for cable assembly on a system. State of the art

[0002] In automated cable assembly, where at least one connector is automatically attached to a cable, the current characteristics of a pre-assembled cable are tested using a cable tester in the final process steps in the prior art. These current characteristics include continuity, short circuit, and / or insulation. In the prior art, the length of a cable is only determined randomly in a manual process step that includes, among other things, opening a cable coil and measuring the cable length. Testing of a cable pre-assembled at one end is also only performed using a current test, including a short circuit and insulation test. However, high-frequency characteristics such as reflection, impedance, and / or propagation time cannot be tested using a prior art cable tester.

[0003] Publication KR 20 200 065 167 A relates to a device for measuring the length of a cable wound on a reel, in particular a heavy cable drum. A TDR (Time Domain Reflectometry) length sensor is attached to an inner open end of the cable within the drum and measures the remaining length of the cable on the reel.

[0004] The publication US 2005 052 190 A1 concerns a digital TDR system. The publication describes how to determine the length of a cable that is still wound on a reel. The accuracy of the TDR system is increased by performing multiple measurements and determining an average value.

[0005] US 2013 162 262 A1 relates to a system for testing a wiring harness. The system includes one or more TDR engines and allows for sequentially applying a TDR stimulus to the branches of the wiring harness and collecting the resulting TDR waveforms. The waveforms are analyzed to determine whether the wiring harness meets quality standards. Specifically, a harness jig is used to couple the wiring harness to the system. For coupling, an operator presses each clip or carrier of the wiring harness into a holder in the harness jig.

[0006] The publication WO 2014 204 484 A1 concerns the determination of the length of a cable wound on a reel. Measurements in the ultrasonic range are used to determine the length.

[0007] US 4,285,118 A relates to a device for assembling electrical connectors on a multi-core flexible flat cable and, in particular, to a device for simultaneously testing the cable and the connector for opens and short circuits while the cable is being terminated with the connector.

[0008] The devices and systems described in the prior art have the disadvantage that they are not suitable for integration into an automated process flow. In particular, the connection between the cable to be tested and the measuring device is either not described or is performed manually. Furthermore, the systems described are not suitable for measuring short cables, i.e., those with lengths in the lower centimeter range. Finally, in the prior art, the cables are only measured single-ended, i.e., against ground, so multi-core cables cannot be measured. Description of the invention

[0009] It is therefore an object of the present invention to overcome the above-mentioned disadvantages and to provide a device and a method which enable automated high-frequency testing of cables, in particular pre-assembled cables in a manufacturing plant.

[0010] The above-mentioned object is achieved by a system according to claim 1 and a testing method according to claim 7. Further advantageous embodiments of the invention can be found in the dependent claims, the description, and the drawings.

[0011] According to the invention, the above-mentioned object is achieved by a system for cable assembly comprising a cable carrier which is configured to transport and hold at least one cable, a TDR measuring device which is configured to carry out high-frequency measurements, and a contacting device which is movable relative to the cable and the TDR measuring device and which is connected to the TDR measuring device via a high-frequency connection, wherein the contacting device can contact the cable in a high-frequency-compatible manner.

[0012] The cable assembly system features an integrated testing system. Automated cable assembly with end-of-line testing of the assembled cable is possible. In particular, manual testing, which would involve opening a cable coil and laying and measuring the cable on a laying board, is eliminated. Furthermore, TDR measurements can be used to detect breaks in the cable. The overall testing process is faster and more reliable.

[0013] The TDR measuring device preferably has at least two channels, and the at least two channels can be operated in single-mode or differential mode. In single-mode, two lines can be measured simultaneously. This shortens the overall test time. In differential mode, several wires of a line can be measured against each other, allowing multi-wire lines to be tested.

[0014] The TDR measurement device is preferably based on the "sequential equivalent-time sampling" method and has step generators, wherein the step generators have a rise time of less than 100 ps, ​​more preferably less than 70 ps, ​​most preferably less than 65 ps, and a measurement bandwidth of more than 5 GHz, more preferably more than 8 GHz, and most preferably more than 10 GHz. In particular, the TDR measurement device has no dead times. These parameters allow very short signal propagation times to be measured, which in turn allows very short cable lengths to be measured. Since cables with lengths of less than 30 cm (equivalent to approximately 1 foot) are also assembled during cable assembly, measuring short cables is advantageous. In addition, a very high spatial (lengthwise) resolution is achieved.The high resolution enables precise length measurements and the precise detection of interruptions or mechanical faults, such as a ground clamp connected to the cable. The measurement speed for a cable with a maximum length of 16 m is less than 4 seconds.

[0015] The cable can preferably be wound into a coil and, more preferably, can be pre-assembled on one or both sides. A cable is preferably wound into a coil to save space and be easier to handle. In an automated process, it is advantageous if the cable can remain permanently wound as a coil, since opening the coil takes time and an unrolled cable is cumbersome to handle. During cable assembly, a cable is pre-assembled on one or both sides, i.e. it is permanently connected to a connection element such as a plug or socket. In contrast to a non-assembled cable, particular attention must be paid to the geometry of the connection element during cable contacting to ensure a reliable connection.

[0016] A high-frequency-compatible connection preferably comprises the same impedance between the TDR measuring device, the contact to the cable, and the cable. Same impedance also means approximately the same impedance, so that measurement signals (reflection signals) suitable for reliable measurements can be received. Impedance is particularly crucial for high-frequency signals. If the impedance differences are too large, a transmitted measurement signal is attenuated too much at the transitions from one medium to another, resulting in received measurement signals that are too weak for reliable evaluation.

[0017] The contacting device comprises a spring-loaded contact pin. When the cable is pressed against the contact pin, the spring tension creates a permanent contact force between the contact pin and the cable, the first cable end, or the connecting element. This ensures reliable contact between the contact pin and the cable. If the connection were only loose, unintentional movement in the system could cause a gap between the cable and the contacting device. This gap would result in a significant impedance difference, which would negatively impact the high-frequency measurements.

[0018] The TDR measurement device preferably includes a high-frequency multiplexer. This allows multiple lines to be measured simultaneously, thus accelerating the overall testing process.

[0019] The system also features a PC for controlling measurements and processing measured data from the TDR measuring device, and a PLC for controlling the automatic feeding of cables to the contacting device. In automated cable assembly, manual steps should be reduced to a minimum or, ideally, eliminated. By using a PC and a PLC, manual steps can be eliminated. The automated process is faster and often more reliable.

[0020] The above-mentioned object is further achieved in particular by a testing method for cable assembly on a system which comprises at least one line carrier, a contacting device and a TDR measuring device which is connected to the contacting device via a high-frequency connection, the method comprising the following steps: positioning a line relative to the contacting device by means of the line carrier, aligning the contacting device on the line so that the contacting device can be brought into contact with the line, testing the line by means of the TDR measuring device, and after testing, moving the contacting device in a direction away from the line so that the line can be moved freely by means of the line carrier.

[0021] All process steps are carried out automatically and ensure reliable cable testing. In particular, the movement of the contacting device creates a reliable, high-frequency-compatible connection between the cable and the TDR measuring device. The cable carrier only needs to position the cable to be tested in a test area, while the contacting is carried out and monitored by the contacting device. By inserting the cable into the contacting device, preferably in a form-fitting connection, additional positioning steps are eliminated. After the cable has been tested, the contacting device releases the cable so that the cable carrier can, for example, continue its original movement along a second direction transverse to the contacting device. The few and often one-dimensional movements are advantageous for an automated process.

[0022] Preferably, the step of aligning the contacting device with the line comprises pressing the contacting device against the line. Pressing the contacting device, and in particular the contact pin, against the line provides a simple, reliable, and detachable connection between the line and the contacting device. This allows a connection to be quickly established and then released again after the measurement has been completed.

[0023] Preferably, the step of checking comprises determining the line length and / or an interruption of the line.

[0024] Preferably, the testing step includes determining DC characteristics. In addition to high-frequency measurements, DC characteristics can also be tested. This provides a comprehensive test of a line, which increases the overall quality of all lines.

[0025] The testing procedure also includes the following steps: transporting the cable to a subsequent process step and providing a subsequent cable using the cable carrier on the contacting device. These process steps create a closed, automated testing process.

[0026] Preferably, the test method further includes the initial step: calibrating the test method using a measurement on a cable of a defined length. This initial step means that the calibration is performed once before a series of cable tests are performed. Calibration can be performed, for example, at the start of commissioning a system, at the start of a new assembly line, at the start of a shift at a system, or at other appropriate / necessary times. Calibration increases the reliability of the measurements.

[0027] The following description of exemplary embodiments is made with reference to the accompanying figures. In the figures: Fig. 1 is a schematic representation of an embodiment of a part of a cable assembly system; Fig. 2 is a diagrammatic representation of an embodiment of a TDR measurement; and Fig. 3 is a schematic representation of an embodiment of a circuit with respect to impedance.

[0028] In the following, embodiments are described in detail with reference to the figures.

[0029] Fig. 1shows an embodiment of a system 1 for cable or line assembly. The system 1 comprises several modules that are configured to assemble a line 40 with at least one connector. The modules can, for example, comprise a crimping module for contacts and / or a joining module for connectors. The forwarding and processing between and at the modules is automated for a fast process flow. At the end of the cable assembly, the fully assembled line 40 is to be tested. With the Fig. 1 In Appendix 1 shown, testing is integrated into the automated process.

[0030] For a test process, a cable carrier 30, which has received a pre-assembled cable 40, is introduced into the test area 50. The cable 40 can be pre-assembled, but does not have to be. In the illustrated embodiment, the cable carrier 30 grips the cable 40 to securely hold and transport it. In other embodiments, other types of holding are possible. The movement of the cable carrier 30 can be realized by a robot arm or some type of conveyor belt. The test area 50 is preferably marked by a positioning aid 52. In the illustrated embodiment, the positioning aid 52 is a panel with an opening. The opening can, for example, be circular and adapted to the maximum outer radius of the first cable end 41. In other embodiments, the positioning aid 52 can merely comprise a marking that identifies the test area 50.The line carrier 30 positions the line 40, in particular a first end 41 of the line 40, in the test area 50. In a preferred embodiment, the line carrier 30 moves the line 40 along a second direction Y.

[0031] The first end 41 of the cable 40 is preferably pre-assembled, i.e., provided with a connector. The connector is preferably a high-frequency-compatible connector. The cable 40 can be wound into a coil for space-saving transport. The second end 42 of the cable 40 can be pre-assembled or not. In principle, the cable length can be any desired length. In particular, the cable length is in the range from 2.5 cm to 16 m. For automated cable assembly, the cables 40 are preferably single-wire antenna cables with an impedance of 50 Ω or 2 / 4-wire data cables that are twisted and shielded and have a differential impedance of 100 Ω.

[0032] The contacting of the cable 40 to be tested is performed by means of a contacting device 20. The contacting device 20 contacts the cable 40 in a high-frequency manner, which is important for performing TDR measurements. The contacting device 20 has a contacting pin 22 for measurements, which is spring-mounted by a spring element 24. The contacting pin 22 is preferably made of metal to transmit high-frequency signals. An optional insertion aid 28 can facilitate the insertion of a cable 40 into the contacting device 20. Fig. 1The insertion aid 28 is formed by at least two tapered side surfaces. Other shapes are possible. The contacting device 20 is connected to a TDR measuring device 10 via a high-frequency connection 12. Direct current and alternating current signals, including in the high-frequency range, can be transmitted via the high-frequency connection 12. Preferably, the high-frequency connection 12 is connected to the contacting device 20 via a component 26. In particular, the component 26 comprises a 50 Ω impedance plug connection.

[0033] The contacting device 20 is movable relative to the line 40 and the TDR measuring device 10. For a line test, the contacting device 20 is aligned with the first end 41 of the line 40. The contacting device 20 moves, preferably along a first direction X, in the direction of the line 40 or the first line end 41, which is arranged in the test area 50. In particular, the contacting device 20, with integrated centering and fixed stop, moves in the direction of the line 40 until the line 40 moves the spring-mounted contacting pin 22 and compresses the spring element 24. The spring element 24 is only partially compressed, so that it exerts a compressive force on the contacting pin 22 in the direction of the line 40. In particular, the spring element 24 has a working stroke that lies approximately in the rear third of the maximum design.In an alternative embodiment, another element that exhibits a restoring force when compressed can be used. The spring action ensures that the contact pin 22 is permanently in contact with the first end 41 of the line 40, ensuring a high-frequency connection. The electrical signals can be provided by the component 26 via the spring element 24 or a separate connection on the contact pin 22.

[0034] In one embodiment, a good contact can be achieved, for example, when the contact pin is shifted by a certain distance. The distance shift can be detected and trigger a measurement process on the TDR measuring device. In particular, an end position of the contact can be detected by a sensor, and a TDR measurement can be started.

[0035] In order to provide a high signal amplitude on line 40 and obtain a clearly defined signal for evaluation, the connection between the TDR measuring device 10 and line 40 must be configured for high-frequency use. For a high-frequency connection, the impedance, i.e., the characteristic impedance, of the TDR measuring device 10, the contact to lines 12, 20, and line 40 must have the same impedance (see Fig. 3 In the described example, an impedance of 50 Ω is used for single-wire cables due to external specifications. An impedance of 50 Ω is standard for measuring instruments and test objects such as antenna cables. In a coaxial cable, the geometry between the inner and outer conductors and the dielectric determines the characteristic impedance, i.e., the impedance.

[0036] The line 40 is tested using a TDR measuring device 10. For the integration of a TDR measuring device 10 into a production system, a differential TDR measuring device with two channels, suitable for a manufacturing environment, was selected. Standard TDR measuring devices are usually very large and designed more for laboratory use. The selected TDR measuring device 10 is based on the so-called "Sequential Equivalent Time Sampling" method and thus achieves virtual sampling intervals of up to 10 ps. With these sampling intervals, lines 40, especially those with a dielectric of 1.7, can be resolved with a spacing of approximately 1.15 mm. The TDR measuring device 10 in the described embodiment has (step) generators and sampling modules. The step generators have a rise time of less than 65 ps, and the sampling bandwidth is greater than 10 GHz.In particular, the TDR measuring device 10 has no dead time, ie even very short lines 40 with a length greater than 25 mm can be measured or used in advance for calibration.

[0037] The two channels of the TDR measuring device 10 can be operated in single-ended mode or in differential mode. Differential mode makes it possible to measure or test multi-wire cables against each other. Depending on the measurement mode, the number of measurement points or the length of the cable 40, the generator frequency, and the resolution, a measurement requires a certain amount of time, a so-called sweep time. In one embodiment, a measurement of two cables 40 with 8,192 data points takes approximately 0.5 s. In another embodiment, a measurement in single-ended mode for a 16 m long cable 40 requires approximately 2.5 s. Using a high-frequency multiplexer, operation with 4 or 8 channels is also possible, so that multiple cables 40 can be tested simultaneously.

[0038] In Fig. 2an embodiment of a TDR measurement is shown. The measurement points are shown on the horizontal axis, and the signal amplitudes on the vertical axis. A line length is determined via the propagation velocity and the propagation time by means of the initial reflection (steeply negative amplitude) of a line 40 between the contact pin 22 and the first end 41 of the line 40, i.e. in particular at the radio-frequency connector (see position P1) and the total reflection (steeply rising positive amplitude) at the second end 42 of the line 40, in particular an open, non-terminated line 40 (see position P2). Each measurement point corresponds to a specific resolution of the length of the line 40 with a sampling rate of 10 ps. To increase accuracy, the system can be calibrated in advance with a measurement of a defined length.An interruption of line 40 results in a significant deviation from the reflection diagram shown and in the line 40 not being of the minimum length.

[0039] With the described system 1 or the described test method, both direct current properties, such as continuity and / or short circuit, and high-frequency properties, such as reflection, impedance and / or propagation time, can be determined and automatically checked at the end of the automated assembly of a cable 40.

[0040] In the described embodiment, a PC controls the measurement and processes the data from the TDR measuring device 10. The automatic feed is controlled by a PLC. After the test, the contacting device 20 is returned to its initial position, and the cable 40 is transported further for a subsequent process step, for example, removal. The same or a different cable carrier 30 positions and holds a subsequent cable 40, and the described process starts again. LIST OF REFERENCE SYMBOLS

[0041] 1Appendix 10TDR measuring device 12High-frequency connection 20Contacting device 22Contacting pin 24Spring element 26Component 28Insertion aid 30Cable carrier 40Cable 41First end 42Second end 50Test area 52Positioning aid P1First position P2Second position XFirst direction YSecond direction

Claims

1. System (1) for automated cable assembly, comprising: a) a plurality of modules, which are configured to pre-assemble a line (40) with at least one plug; b) a line carrier (30), which is configured to transport and hold at least one line (40); wherein c) forwarding and processing between and to the modules take place in an automated manner; d) a TDR measuring device (10), which is configured to perform radio-frequency measurements; and e) a contacting device (20), which can be moved in relation to the line (40) and the TDR measuring device (10) and is connected to the TDR measuring device (10) via a radio-frequency connection (12), wherein the contacting device (20) can contact the line (40) with radio-frequency capability; f) a PC for controlling measurements and for processing measured data from the TDR measuring device (10), and a PLC for controlling the automatic supply of lines (40) to the contacting device (20); wherein g) the line carrier (30) performs a movement along a second direction (Y) transversely to the contacting device (20) and positions the line (40) in a test area (50); h) the contacting device (20), for contacting the line (40), performs a movement along a first direction (X), in the direction of the line (40) which is arranged in the test area (50); and i) the contacting device (20) comprises a spring-loaded contacting pin (22).

2. System according to Claim 1, in which the TDR measuring device (10) has at least two channels, and the at least two channels can be operated with single-ended operation or in differential mode.

3. System according to Claim 1 or 2, in which the TDR measuring device (10) is based on the "sequential equivalent-time sampling" method and has step generators, wherein the step generators have a rise time of less than 100 ps, preferably less than 70 ps, most preferably less than 65 ps, and a measurement bandwidth of more than 5 GHz, more preferably more than 8 GHz, and most preferably more than 10 GHz.

4. System according to any of Claims 1-3, in which the line (40) can be wound up to form a coil, and preferably can be pre-assembled on one or two sides.

5. System according to any of Claims 1-4, in which a connection with radio-frequency capability comprises an equal impedance of the TDR measuring device (10), the contacting means to the line (12, 20) and the line (40).

6. System according to any of Claims 1-5, in which the TDR measuring device (10) comprises a radio-frequency multiplexer.

7. Test method for automated cable assembly in a system (1) according to any of Claims 1-6 which comprises at least a plurality of modules for assembly of a line (40), a line carrier (30), a contacting device (20), a TDR measuring device (10), which is connected to the contacting device (20) via a radio-frequency connection (12), a PC and a PLC, wherein the method comprises the following steps: a) automated processing of the line (40) on the modules; b) automated forwarding of the line (40) between the modules along a second direction (Y) perpendicularly to the contacting device (20); c) positioning the line (40) in a test area (50) in relation to the contacting device (20) by means of the line carrier (30) and in a manner controlled by the PLC; d) aligning the contacting device (20) with the line (40) along a first direction (X), in the direction of the line (40) which is arranged in the test area (50), so that the contacting device (20) can be brought into contact with the line (40); e) testing the line (40) by means of the TDR measuring device (10) and in a manner controlled by the PC; f) after testing, moving the contacting device (20) along the first direction (X), in the direction away from the line (40), so that the line (40) can be moved freely by means of the line carrier (30); g) further transporting the line (40) to a subsequent process step; and h) providing a following line (40) to the contacting device (20) by means of the same or another line carrier (30).

8. Test method according to Claim 7, in which the step of aligning the contacting device (20) with the line (40) comprises pressing the contacting device (20) against the line (40).

9. Test method according to Claim 7 or 8, in which the testing step comprises determining the line length and / or an interruption in the line (40).

10. Test method according to any of Claims 7-9, in which the testing step comprises determining DC properties.

11. Test method according to any of Claims 7-10, further comprising the initial step: calibrating the test method by means of a measurement on a line (40) of defined length.