Automatic leak detection method using a robotic sniffer leak detector

Abstract

A method for more reliably and quickly detecting a leak in a fluid carrier of a heat exchange device is provided. [Solution] The present invention is characterized by comprising the steps of: b) moving a probe tip 25 of a probe 22 guided by a robot 32 to a test location 20 under investigation; b) recording a measurement signal from the collected gas using a gas detector 24; c) detecting a first measurement value of the measurement signal at a first measurement time point; d) detecting the first measurement time point and assigning the first measurement time point to the first measurement value; e) detecting and assigning a first measurement position of the probe corresponding to the first measurement time point; f) repeating steps a) to e) for a second measurement time point; and g) associating the measurement values ​​with each measurement position of the probe 22 so that it is possible to use the measurement values ​​to determine at which measurement position an extreme value suggesting a possible leak in the specimen was detected.

Description

[Technical field]

[0001] The present invention relates to a leak detector used to detect a leak in a test object. [Background technology]

[0002] A leak detector is described, for example, in DE 10 2005 022 156 A1 (Inficon). The leak detector comprises a probe, the sniffer tip of which is placed in a predetermined test area of ​​a test object. The test object is filled with a test gas, for example helium. If the test gas leaks, it is sucked from the sniffer tip into a base unit and supplied to a test gas detector, which may be configured, for example, as a mass spectrometer.

[0003] When using a leak detector, a test object, such as an air conditioning system or a refrigeration unit of a refrigerator, is filled with a test gas, and a sniffer probe is used to detect whether the test gas leaks from the test object. During quality inspection of industrial products, a sniffer tip is placed in a specific test area of ​​the test object where a leak may exist. The probe is then moved manually to the test area. In this method, it is difficult to confirm whether the sniffer tip has been moved to all target test areas of the test object. An operator may inadvertently overlook some test areas or skip other test areas that the operator may consider to be unimportant according to his / her own subjective evaluation.

[0004] US Patent No. 4,945,305 (Ascension) describes a positioning system with a transmitter generating a pulsed DC magnetic field and a receiver located on the object. This method is extremely useful for determining the current position and comparing it with a desired position for feedback. There is no interference from non-magnetic objects in the line of sight between the transmitter and the receiver. As the location of the test object is static, residual interference from large magnetizable materials such as compressor blocks or refrigeration machines can be removed by calibration. This method has been found to be extremely useful in the implementation of the present disclosure.

[0005] WO2009 / 016160A1 (Patent Document 3) describes a leak detector comprising a base unit connected to a probe via a tube section. A sniffer tip is positioned in a test zone or area of ​​a test specimen. If a test gas leaks from the test specimen, this is detected by a test gas detector in the base unit. A positioning system is provided which comprises a transmitter, a receiver provided in the probe, and a power feed evaluation section. This allows monitoring and confirmation of the presence or absence of a sniffer probe in each test area.

[0006] In the field of automation, it is known to obtain digital data of a physical object using a 3D sensor to obtain a point cloud in a three-dimensional virtual space, the point cloud being a point cloud that represents each surface point of the outer surface of the physical object. Robots used in the automation industry, for example in the automated manufacturing of products such as cars, are controlled by software algorithms that use the obtained digital data. Typically, this is done to sense the entire perimeter or outer surface of a physical object to locate, grasp, move or reposition the physical object, or, for example in the vehicle manufacturing industry, to paint the outer surface of the physical object with a spray painting robot arm. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] DE 102005022156 [Patent Document 2] U.S. Pat. No. 4,945,305 [Patent Document 3] International Publication No. 2009 / 016160 Summary of the Invention [Problem to be solved by the invention]

[0008] In heat exchange devices such as refrigerators, air conditioning systems, and heat pumps, leak detection by the sniffer method is performed as part of the quality inspection of the heat exchange device. An operator must visually identify the target test area, such as a liquid transport pipe in a heat exchanger, and manually move the probe to each test area one after another. This type of sniffer-based leak detection for heat exchange devices is not only time-consuming, but also prone to human errors such as skipping a test area or not getting the sniffer probe close enough to the test area.

[0009] The invention is based on the object of detecting leaks in a fluid carrier of a heat exchanger device more reliably and more quickly. [Means for solving the problem]

[0010] The method according to the invention is defined by the features of independent claim 1.

[0011] That is, a probe tip of a robot-guided probe is moved by the robot to the location under investigation (step a). After reaching the location, gas or air is sucked in through the probe tip and fed to a gas detector, and a measurement signal of the sucked in gas is recorded by the gas detector (step b). One or more first measured values ​​of the measurement signal are obtained at one or more first time points (step c). Typically, the probe tip sucks in gas or ambient air as it approaches the location under investigation, but is not activated when it reaches the location under investigation. Furthermore, the first measurement time points are obtained and assigned to the first measured value (step d). Finally, a first measured position of the probe corresponding to the first measurement time point is also obtained (step e). This results in position data indicative of the position of a component of the probe (e.g. the probe tip) indicative of the position that the component was in at the first measurement time point. Thereby, for each signal value I of a gas measurement, a time t of the measurement and a location or position in space (x, y, z) are assigned as I(t, x, y, z). If necessary, in addition to or instead of the Cartesian spatial coordinates, spatial angular coordinates (r, Φ, θ) in the form of two spatial angles Φ, θ and an axial distance r may be acquired along the probe. These steps are repeated for one or more subsequent second measurement times (step f). According to the invention, the measured values ​​are associated with the respective measurement positions (step g) in such a way that it is possible to evaluate, with the aid of the measured values, at which measurement positions extreme values ​​of the measurement signal are detected that may indicate a possible leak of the analyte. In this way, a fully automatic leak detection is performed using a robot, without a human user having to carry out the evaluation and / or manipulation and / or leak detection and / or each of these steps.

[0012] Between the execution of step e) and the execution of step f), the probe tip may be moved by the robot to another test location and the measurement of the other test location may be repeated. Alternatively or in addition, the probe tip may be moved from the robot to another test location and then steps b) to g) may be repeated. Preferably, the measurement position of the probe tip is detected, for example, using a 3D sensor. The 3D sensor may be an imaging system including at least one optical camera and preferably also at least one illumination device.

[0013] During recording of the measurement signals, the probe may be moved by the robot such that the probe successively assumes different measurement positions during measurement. The measurements may be obtained as a function of the measurement position of the probe and / or the speed of movement of the probe. Preferably, the evaluation of the measurement signals is performed as a function of the measurement position of the probe tip.

[0014] Advantageously, two or more measurements are performed at the same said measuring location and the obtained measurements are compared with each other.

[0015] The evaluation of the measurement signal may be performed taking into account the speed of movement of the probe during measurement.

[0016] As the probe is moved to the test location and before a measurement is taken, the probe signal may be zeroed by using the gas detector to obtain a measurement signal at a location known to be free of tracer gas and / or at a constant background concentration.

[0017] Alternatively, signal nulling may be performed on the path of the probe tip to the test site at a distance far enough away from the test site that the background signal can be determined (zeroed).

[0018] The leak detection system may be calibrated by moving the probe to a location where a known, predetermined leak amount occurs (eg, a test leak).

[0019] The probe may be moved to a measurement location where a leak was detected or suspected during a previous measurement, to perform a control measurement at that measurement location.

[0020] Preferably, those measurement locations where leaks have been suspected from previous measurements are marked.

[0021] The rate at which the gas flow is captured by the probe may be adjusted based on the rate at which the probe moves.

[0022] The gas leak detector may be, for example, a sniffer-type leak detector comprising a sniffer probe having a sniffer tip into which gas is drawn. In a variant, the gas leak detector may comprise a test gas probe, the detector tip including a gas detector for the test gas.

[0023] An exemplary embodiment of the present invention will now be described in detail with reference to the drawings. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram showing a leak detection system and a subject in the form of a heat exchange device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] In the illustrated embodiment, the gas leak detector is in the form of a sniffer-type leak detector, the probe of which is a sniffer probe, through whose sniffer tip the gas to be analysed is drawn.

[0026] FIG. 1 depicts a heat exchanger 12 in the form of a refrigerator. The term "heat exchanger" as used in this disclosure refers to systems or devices that include a heat exchanger, such as refrigerators, air conditioners, heat pumps, etc. The heat exchanger has a plurality of fluid carriers 16, 18 in the form of piping that is welded or soldered to the back side of the refrigerator during manufacturing, on its rear underside 14. As part of a fully automated quality control, a specific test area 20 must be identified and leak detection must be performed in the test area 20. The test area 20 may be an area of ​​the heat exchanger where piping is attached, welded or soldered to each other, where piping terminates, where piping is connected to another piping, or where piping meets or crosses. In the embodiment depicted in FIG. 1, a first fluid carrier 16 is disposed vertically, and one end of a second fluid carrier 18 is connected to the first fluid carrier 16. In FIG. 1, the connection region between the pipes 16 and 18 is taken as a test region 20, which is indicated by a dashed circle.

[0027] The present invention resides in the background of automatically moving a sniffer probe 22 of a sniffer leak detector 24 to a test area 20, with a sniffer probe 25 of the sniffer probe 22 positioned close enough to the test area 20 to pick up gas leaking from a leak in one of the pipes 16, 18. As is conventional, the sniffer probe 22 is connected to the gas leak detector 24 via a connecting tube or capillary 26. The objective is to correlate the movement of the sniffer probe with the associated signal response of the measurement signal.

[0028] The sniffer probe 22 is attached to the distal end 28 of a robotic arm 30 of a robot 32 .

[0029] A 3D sensor 34 in the form of an imaging system 36, including two optical cameras 38, 40 and an illumination device 42 in the form of LED lights, acquires digital image data from the rear underside 14 of the heat exchange device 12. The illumination device 42 illuminates the heat exchange device 12, in particular the rear underside 14 of the heat exchange device 12, in a manner known per se. The cameras 38, 40 capture the reflected light and the imaging system 36 generate digital image data from which a point cloud 44 in a three-dimensional virtual space 48 is obtained. As a variant, it is also possible to deduce the position of the measurement probe from a known position of the robot arm. The robot arm is guided to a known measurement position. If the size and orientation of the measurement probe relative to the robot arm are known, the position of the measurement probe can be determined.

[0030] In the present invention, the acquisition of measured values ​​of the measurement signal of the gas flow sucked through the sniffer tip 25, the detection of the measurement time points for each measured value, and the allocation of the measurement time points to the measured values ​​are performed using the gas detector 24. Furthermore, the position of the sniffer tip 25, i.e., the relative position of the sniffer tip 25 with respect to the specimen 12 or the measurement point 20, is imaged by the cameras 38, 40 of the 3D sensor 34, so that each measurement position of the sniffer tip is detected at each measurement time point.

[0031] During the evaluation of the measured values, the measured values ​​are compared with the respective measurement positions, so that from the respective measurement positions and from the amplitudes of the measured values ​​it is possible to draw conclusions about possible leak locations.

[0032] A delay in the signal response due to the gas transit time through the sniffer line 26 is a typical example of a cause for the need for signal correction. After the test gas cloud is sucked into the sniffer tip 25, the gas travels through the line 26 to the main body of the gas detector 24. This transit time, also called dead time, can be several seconds. That is, at the time of the signal response of the gas detector 24 caused by a leaking gas cloud sucked in at any measurement point, the sniffer probe 22 may have already been moved to the next measurement point by the robot arm 30. This time delay must be taken into account when properly allocating the measurement signals to the measurement points.

[0033] The gas flow time must be measured in advance. This can be done, for example, during the calibration of the system. For this purpose, the robot arm 30 positions the tip 25 of the sniffer probe 22 in front of the test leak. In the process, the delay time from the approach of the test leak to the signal response is measured. This delay time is then taken into account when reading the signal response of the gas detector 24 and allocating the leak location to the test object.

Claims

1. A method for automatic leak detection using a robotic gas leak detector (56), comprising: a) moving a probe tip (25) of a probe (22) guided by a robot (32) to a test site (20) to be investigated by the robot (32); b) recording a measurement signal from the gas sampled at the probe tip (25) using a gas detector (24); c) detecting one or more first measured values ​​of said measurement signal at one or more first measurement time points; d) detecting the first measurement time and assigning the first measurement time to the first measured value; e) detecting and allocating a first measurement position of said probe (22) corresponding to said first measurement time point; f) repeating steps a) to e) for one or more subsequent second measurement time points; g) correlating said measurements with the respective measurement locations of said probe (22) in such a way that it is possible to evaluate, by means of said measurements, at which measurement locations extreme values ​​of the measurement signal were detected which may indicate a possible leak of the analyte; A leak detection method comprising:

2. 2. The leak detection method of claim 1, wherein the robot (32) moves the probe tip (25) to another test site (20) after step e) is performed and before step f) is performed.

3. 2. The leak detection method according to claim 1, wherein steps b) to g) are repeated after the robot (32) moves the probe tip (25) to another test location (20).

4. 2. The method for leak detection according to claim 1, characterized in that in step e) the measurement position of the probe (22) is detected by means of a 3D sensor.

5. 2. The method of claim 1, wherein in step e) the measured position of the probe (22) is estimated from a known position of an arm (30) of the robot (32) that holds the probe.

6. 2. The method for leak detection according to claim 1, characterized in that, when acquiring the measurement signal, the probe (22) is moved by the robot (32) so that the probe (22) successively assumes different measurement positions.

7. 2. A method for leak detection according to claim 1, characterized in that the measurements are obtained as a function of the measurement position of the probe (22) and / or the movement speed of the probe (22).

8. 2. A method for leak detection according to claim 1, characterized in that the evaluation of the measurement signal is performed as a function of the measurement position of the probe tip (25).

9. 2. A method for leak detection according to claim 1, characterized in that two or more measurements are made at the same measurement location and the obtained measurements are compared with each other.

10. 2. A method for detecting leaks according to claim 1, characterized in that the evaluation of the measurement signal is performed taking into account the movement speed of the probe (22) during the measurement.

11. 2. The method for leak detection according to claim 1, characterized in that during step a) and before step b), a calibration of the probe (22) by zero adjustment is performed by acquiring a measurement signal with the gas detector (24) and storing it as a background signal.

12. 2. The method for detecting a leak according to claim 1, further comprising the steps of: moving the probe (22) to a measurement position where a leak has been determined to exist, and performing a control measurement at the measurement position.

13. 2. The leak detection method according to claim 1, further comprising marking a measurement position where a leak is assumed to exist based on previous measurements.

14. 2. The method of claim 1, wherein the amount of gas flow sucked in by the probe is adjusted according to the moving speed of the probe.

15. 2. The method of claim 1, wherein said gas leak detector is a sniffer type leak detector, said probe is a sniffer probe, and said probe tip is a sniffer tip.

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