Device for performing a job operation

Abstract

The invention relates to a device for performing a work operation, in particular a welding device, comprising: at least one actuator for performing a work operation; the magnetic field source is fixed on the actuator; at least one magnetic field sensor for detecting the position of the actuator, the magnetic field sensor being designed to detect a first magnetic field strength in a first direction and a second magnetic field strength in a second direction perpendicular to the first direction; and a control and evaluation unit, which is connected to the magnetic field sensor and which is designed to identify whether the magnetic field detected by the magnetic field sensor is a magnetic field produced essentially by the magnetic field source on the basis of a comparison metric that associates the detected first magnetic field strength with the detected second magnetic field strength; and determining the position of the actuator if a positive conclusion is made on the basis of the detected first magnetic field strength and / or the detected second magnetic field strength, and issuing a control command on the basis of the determined position of the actuator.

Description

Technical Field

[0001] Magnetic sensors, such as magnetic limit switches, are used in a variety of applications to determine the position of actuators within an application, especially their final position. These applications typically involve pneumatic cylinders, grippers, or similar actuators whose final position is detected by magnetic limit switches. The limit switches are based on the detection of the magnetic field generated by a sensor magnet within the actuator. Background Technology

[0002] However, in practice, problems may arise because magnetic interference fields, typically of a spatial static origin, can interfere with magnetic limit switches and cause them to malfunction. For example, in welding applications, the high-intensity current generated during welding can produce a strong magnetic field, which acts as a magnetic interference field. Failures caused by magnetic interference fields are undesirable because they affect the accurate measurement of actuator position and jeopardize the reliability of the system.

[0003] Existing methods for solving this problem are often expensive and lead to increased complexity, or fail to prevent unwanted failures to a satisfactory degree. Summary of the Invention

[0004] The object of the present invention is to provide an improved apparatus and a corresponding method for performing work operations.

[0005] This objective is achieved by means and methods according to embodiments of the present invention.

[0006] A first aspect of the invention relates to an apparatus for performing a work operation, particularly a welding apparatus, the apparatus comprising:

[0007] At least one actuator that performs a job operation;

[0008] A magnetic field source fixed to the actuator;

[0009] At least one magnetic field sensor for detecting the position of the actuator, wherein the magnetic field sensor is designed to detect a first magnetic field strength in a first direction and a second magnetic field strength in a second direction perpendicular to the first direction;

[0010] A control and evaluation unit, connected to the magnetic field sensor, is designed to identify whether the magnetic field detected by the magnetic field sensor is inherently generated by a magnetic field source based on a comparison metric (Vergleichsmetrik) that correlates a detected first magnetic field strength with a detected second magnetic field strength; and

[0011] If a positive conclusion is reached based on the detected first magnetic field strength and / or the detected second magnetic field strength, the position of the actuator is determined, and a control command is issued based on the determined position of the actuator.

[0012] This invention is based on the fundamental concept that the magnetic field generated by a magnetic field source fixed to an actuator possesses specific characteristics distinct from other interfering magnetic fields. Specifically, the magnetic field source moves with the movement of the actuator relative to the magnetic field sensor, resulting in different changes in the strength of the first and second magnetic fields. According to this invention, other stationary magnetic field generators, such as welding devices, can be distinguished from the magnetic field source fixed to the actuator.

[0013] For example, the magnetic field source can be a permanent magnet, the magnetic properties of which are known. However, the magnetic field source can also be an electromagnet, especially an electromagnet with a preset pulse pattern. The magnetic field of the magnetic field source can also be identified and / or verified accordingly through the pulse pattern.

[0014] Therefore, it can be checked whether the magnetic field data detected by the magnetic field sensor (i.e., the detected first magnetic field strength and the detected second magnetic field strength) actually originates from the magnetic field source fixed to the actuator and is not generated by interfering magnetic fields. Only when this condition is met will the actuator's position be determined based on the sensor data of the magnetic field sensor, or the determined actuator position be confirmed as valid and thus consistent with the actual position of the actuator. In particular, in the case of a negative conclusion, i.e., when the control and evaluation unit determines that the magnetic field detected by the magnetic field sensor is not generated by the magnetic field source, the control and evaluation unit will not issue any control commands. Therefore, device malfunctions (e.g., actuator stoppage due to incorrect actuator position determination) can be avoided.

[0015] In various applications, interfering magnetic fields arise or are generated during the execution of a work operation. For example, in welding equipment, this can be a magnetic field caused by the high current during welding. In this case, the actuator could be, for example, a welding clamp that is movable relative to the workpiece and has, for example, a preset movement pattern or a preset movement radius. Other applications, such as magnetic lifting devices or linear motor systems, also generate such interfering magnetic fields, which may be mistakenly perceived by a magnetic field sensor as a magnetic field generated by the magnetic field source to be detected.

[0016] The source of the interfering magnetic field can be fixed, especially relative to the magnetic field sensor. This means, for example, that the aforementioned welding or lifting device is permanently fixed in place. For instance, it could be a stationary welding device to which the workpiece to be processed is fed via an actuator. Alternatively, the source of the interfering magnetic field can also be fixed only during operation (i.e., during the period when the interfering magnetic field is generated). For example, the source of the interfering magnetic field could be a welding clamp fixed to the actuator that does not move during welding (e.g., remains in close contact with the workpiece).

[0017] A magnetic field sensor detects a first magnetic field strength in a first direction and a second magnetic field strength in a second direction perpendicular to the first direction. The detected magnetic field strength can be magnetic flux density. Based on the detected first and second magnetic field strengths, the magnetic field sensor can determine the position of a magnetic field source fixed to an actuator, thereby determining the position of the actuator. In particular, the position of the magnetic field source or actuator relative to the magnetic field sensor can be determined. Since the position of the magnetic field sensor (especially inside the device) is known, the absolute position of the magnetic field source in space can be inferred using a known mathematical model. In particular, the detected first and second magnetic field strengths can be assigned to positions in space, for example, using an assignment table. Detecting the position of the magnetic field source using a magnetic field sensor is a known technique in the prior art and will not be described further here.

[0018] To prevent false detections, a comparison metric is determined that correlates the detected first magnetic field strength with the detected second magnetic field strength. The magnetic field generated by the magnetic field source will result in a corresponding characteristic value for the comparison metric. The same applies to interfering magnetic fields. The range of these corresponding characteristic values ​​is, for example, known, so the comparison metric can indicate whether the detected magnetic field is actually generated by the magnetic field source. From the comparison metric, in particular, it can be inferred whether the detected actuator position is the actual position of the actuator.

[0019] The advantage of this invention is that, in order to identify whether a magnetic field detected by a magnetic field sensor is generated by a magnetic field source, no additional components are required besides the magnetic field sensor itself; the determination is based solely on the detected data. Therefore, the determination can be made in a simple manner without the additional cost of corresponding hardware. Another advantage of this data-based approach is that no additional space is required for corresponding components; therefore, the device, especially the sensor, can be designed to be particularly compact.

[0020] Other embodiments of the present invention can be found in the specification and drawings.

[0021] According to the first embodiment, the control and evaluation unit is designed to determine, based on a comparison metric, whether the detected magnetic field has a spatially static origin or a spatially variable origin. If the magnetic field is determined to be a spatially variable origin, the magnetic field detected by the magnetic field sensor is identified as a magnetic field generated by a magnetic field source. Therefore, the fact that the magnetic field source is fixed to the actuator allows its spatial position to change. The magnetic field source (whose spatial position can change, for example, due to actuator movement) results in a magnetic field vector having variable angles and variable magnitudes. In contrast, interfering magnetic fields are typically spatially static magnetic fields, emanating from a fixed point in space and changing primarily only with time. Therefore, both spatially static and spatially variable magnetic fields can cause the magnetic field sensor to detect changing magnetic field data or magnetic field strength during detection. Unlike magnetic field sources with a spatially static origin, for magnetic field sources with a spatially variable origin, the spatial direction of the magnetic field vector changes during detection. This difference can be reflected in the comparison metric, and thus, this difference can be detected by the control and evaluation unit based on the comparison metric.

[0022] According to one embodiment, the control and evaluation unit is designed to determine, based on a comparative metric, whether the detected magnetic field originates from a time-static magnetic field or a time-variable magnetic field, and if it is determined that the detected magnetic field originates from a time-static magnetic field, then the magnetic field detected by the magnetic field sensor is identified as a magnetic field generated by a magnetic field source. As mentioned above, the magnetic field strength detected by the magnetic field sensor may change during detection, regardless of whether it is a spatially static magnetic field source or a spatially variable magnetic field source. If the detected magnetic field strength originates from a time-variable magnetic field with a spatially static origin, then for the first and second detected magnetic field strengths, the changes in the detected magnetic field strength during detection are similar, especially proportional, because the changes in the detected magnetic field strength during detection have the same cause, such as an increase in current during welding. Conversely, when the magnetic field source has a time-static magnetic field but its spatial location changes, the change in the spatial location of the magnetic field source has different effects on the first detected magnetic field strength in the first direction and the second detected magnetic field strength in the second direction during detection. This is especially because the change in the spatial location of the magnetic field source has a greater effect on the first detected magnetic field strength than on the second detected magnetic field strength.

[0023] According to one embodiment, the control and evaluation unit is designed to determine whether the actuator has reached its final position based on sensor data from a magnetic field sensor. For example, the final position of the actuator may be preset. When the actuator reaches its final position, i.e., when the magnetic field source reaches its final position, the magnetic field sensor detects a first magnetic field strength in a first direction and a second magnetic field strength in a second direction associated with that final position. The first and second magnetic field strengths associated with the final position may, for example, be known. Therefore, based on the comparison between the detected first and second magnetic field strengths and the first and second magnetic field strengths associated with the final position, it can be determined whether the actuator has reached its final position. In particular, the actuator position determination can be limited to the determination of the actuator's final position; that is, the magnetic field sensor is only used to determine whether the actuator has reached its final position. In this case, it is particularly easy to determine whether the magnetic field detected by the magnetic field sensor is generated by the magnetic field source, because the magnetic field generated by the magnetic field source is subject to corresponding limitations. Therefore, distinguishing between the magnetic field generated by the magnetic field source and the magnetic field generated by interfering magnetic fields becomes simple.

[0024] According to one embodiment, the control and evaluation unit is designed to standardize the detected first magnetic field strength and the detected second magnetic field strength based on the same preset standardization rule, wherein a comparison metric correlates the standardized detected first magnetic field strength with the standardized detected second magnetic field strength. As mentioned above, the magnetic field strength is generated in a spatial static magnetic field source; however, the spatial static magnetic field source can have a time-variable magnetic field strength that is proportional to the first and second magnetic field strengths. This is not the case in the case of a spatially variable magnetic field source. Utilizing this understanding, a corresponding standardization rule can be determined, by which the detected first and second magnetic field strengths are standardized to compensate for the proportionality effect of the first and second magnetic field strengths. For a time-variable magnetic field with a spatial static origin, applying this standardization rule results in the standardized detected magnetic field strengths (i.e., the standardized detected first magnetic field strength and the standardized detected second magnetic field strength) being substantially the same during detection. In other words, the standardized magnetic field distributions of the detected first and second magnetic field strengths are completely consistent. Conversely, applying the same normalization rules to the detected magnetic field strength emitted by a time-static magnetic field with a spatially variable origin does not result in identical detected magnetic field strengths; that is, the corresponding normalized magnetic field distributions are not identical. The variation in detected magnetic field strength in this case is caused by variations in the position of the magnetic field source, and these variations are typically disproportionate in the first and second directions. Therefore, in particular, based on the difference between the normalized first and second detected magnetic field strengths, it can be determined whether the magnetic field detected by the magnetic field sensor is generated by a magnetic field source.

[0025] The standardization of the first and second detected magnetic field strengths can be performed, for example, by multiplying the corresponding detected magnetic field strengths by a corresponding standardization coefficient calculated based on a preset standardization rule. In particular, standardization has the effect of compensating for the absolute magnitude of the corresponding detected magnetic field strength and / or the proportional change in the corresponding detected magnetic field strength over time.

[0026] Standardization coefficients can be calculated, for example, as follows:

[0027]

[0028] The maximum or minimum value corresponds to the maximum or minimum value of the corresponding magnetic field strength detected during the detection period, and the starting or ending value corresponds to the first or last value of the corresponding magnetic field strength detected during the detection period. Therefore, the normalization factor used for the relevant magnetic field strength (i.e., the first magnetic field strength or the second magnetic field strength) is calculated based on the detected value of the relevant magnetic field strength. Subsequently, the calculated normalization factor for the corresponding magnetic field strength can be multiplied by the detected value of the corresponding magnetic field strength to obtain the corresponding normalized magnetic field strength.

[0029] For the above-mentioned normalization coefficients, the normalized values ​​of the detected first magnetic field strength and the detected second magnetic field strength are in the range of 0 to 2. However, the present invention is not limited to the above-mentioned normalization coefficients. In fact, any suitable normalization coefficient can be used. Other examples of corresponding normalization coefficients are as follows:

[0030]

[0031]

[0032] The normalization factor for each detected magnetic intensity value is calculated separately. In other words, the normalization factor (i) for the magnetic intensity at time point i (i.e., for the magnetic intensity (i)) is multiplied by the corresponding magnetic intensity (i) to obtain the corresponding normalized magnetic field intensity.

[0033] The standardized coefficients mentioned above are merely examples, and the invention is not limited thereto. In particular, any suitable standardization rule can be used.

[0034] According to one embodiment, the comparison metric is based on the difference between the larger of the standardized first and second magnetic field strengths of the detected magnetic field and the smaller of the standardized first and second magnetic field strengths of the detected magnetic field. As described above, based on the difference between the standardized first and second magnetic field strengths of the detected magnetic field, it can be determined whether the magnetic field detected by the magnetic field sensor is generated by a magnetic field source. To improve the reliability and validity of this determination, in particular, the comparison metric can be determined based on the maximum difference between two corresponding magnetic field strengths. For example, the comparison metric for time point i during the detection period can be determined based on the following equation:

[0035]

[0036] Here, X(i) and Y(i) represent the detected first magnetic field strength in the first direction at time i and the detected second magnetic field strength in the second direction at time i. To ultimately evaluate whether the magnetic field detected by the magnetic field sensor is generated by a magnetic field source, the maximum value of a calculated comparison metric for i=0 to i=n can be used, where n corresponds to the time point of the last detected value. Therefore, the maximum calculated comparison metric is used for the final evaluation because it corresponds to the maximum difference between the standardized detected first magnetic field strength and the standardized detected second magnetic field strength. In particular, based on this maximum difference, it can be determined whether standardization can compensate for the proportional change of magnetic field strength over time in both directions, thereby determining whether the corresponding magnetic field originates from a static spatial magnetic field source, or whether the changes in the first and second magnetic field strengths during detection are disproportionate, thereby determining whether the corresponding magnetic field originates from a variable spatial magnetic field source.

[0037] According to one embodiment, the device includes multiple magnetic field sensors, particularly two. For example, the device may include: a first magnetic field sensor that detects a first magnetic field strength in a first direction; and a second magnetic field sensor that detects a second magnetic field strength in a second direction perpendicular to the first direction. Specifically, the first and second magnetic field sensors are positioned at different locations. Therefore, the first and second magnetic field strengths are detected by different magnetic field sensors. Alternatively, both the first and second magnetic field sensors can detect the magnetic field strength in the first direction and the second direction perpendicular to the first direction. The advantage of this configuration is that it provides additional information that allows for a better assessment of magnetic field activity.

[0038] It is also conceivable that the welding device includes multiple actuators, each with a fixed magnetic field source to detect the position of each actuator.

[0039] According to one embodiment, the comparison metric is based on the difference between a first magnetic field strength detected by a first magnetic field sensor in a first direction and a first magnetic field strength detected by a second magnetic field sensor in the first direction, or based on the difference between a second magnetic field strength detected by a first magnetic field sensor in a second direction and a second magnetic field strength detected by a second magnetic field sensor in a second direction. In particular, the corresponding difference may include the difference between the maximum values ​​of the corresponding magnetic field strengths detected during detection. For example, the comparison metric may be determined based on the following equation:

[0040]

[0041] Wherein, X1 includes the magnetic intensity in a first direction detected by the first magnetic field sensor during detection, X2 includes the magnetic intensity in the first direction detected by the second magnetic field sensor during detection, Y1 includes the magnetic intensity in a second direction detected by the first magnetic field sensor during detection, and Y2 includes the magnetic intensity in a second direction detected by the second magnetic field sensor during detection. In other words, the difference between functions X1 and X2 and the difference between functions Y1 and Y2 are formed, and the maximum value of the corresponding difference function is determined. Then, the smaller of the two calculated maximum values ​​is used as a comparison metric.

[0042] According to one embodiment, the comparison metric is based on the difference between two of the following: a detected magnetic field strength normalized by a first magnetic field sensor in a first direction, a detected magnetic field strength normalized by the first magnetic field sensor in a second direction, a detected magnetic field strength normalized by a second magnetic field sensor in the first direction, and a detected magnetic field strength normalized by the second magnetic field sensor in the second direction. The two magnetic field strengths used to form the difference are based on the normalized detected magnetic field strength that has the largest difference between a minimum and a maximum value among the normalized detected magnetic field strengths during detection, where the minimum value is a determined minimum value of the corresponding magnetic field strength during detection, and the maximum value is a determined maximum value of the corresponding magnetic field strength during detection. In particular, the corresponding difference may include the difference between the maximum values ​​of the corresponding magnetic field strengths detected during detection. In other words, two magnetic field strengths are used to form a difference that has the largest deviation between the detected minimum and the detected maximum value during detection. The comparison metric can be calculated, for example, as follows:

[0043]

[0044] Z1 and Z2 correspond to the standardized magnetic field strength of the detection that has the maximum difference between the minimum and maximum values ​​during the detection period. The minimum value is a determined minimum value of the corresponding magnetic field strength during the detection period, and the maximum value is a determined maximum value of the corresponding magnetic field strength during the detection period.

[0045] Another aspect of the present invention relates to a method for performing a work operation, particularly a welding process, the method comprising:

[0046] The position of at least one actuator is detected by at least one magnetic field sensor, on which a magnetic field source is fixed. The at least one magnetic field sensor detects a first magnetic field strength in a first direction and a second magnetic field strength in a second direction perpendicular to the first direction.

[0047] A control and evaluation unit, connected to the magnetic field sensor, identifies whether a magnetic field detected by the magnetic field sensor is generated by a magnetic field source based on a comparison metric. This comparison metric correlates the detected first magnetic field strength with the detected second magnetic field strength.

[0048] If a positive conclusion is reached based on the detected first magnetic field strength and / or the detected second magnetic field strength, the position of the actuator is determined, and a control command is issued based on the determined position of the actuator.

[0049] Accordingly, embodiments of the apparatus according to the invention are applicable to the method, particularly in terms of advantages and embodiments.

[0050] It should be noted that any combination of the above embodiments is possible, unless otherwise explicitly excluded. Attached Figure Description

[0051] In the following description, the invention will be illustrated by way of example only, with reference to the accompanying drawings.

[0052] Figure 1 This is a schematic diagram of the welding equipment;

[0053] Figure 2 This is a schematic diagram of another welding device;

[0054] Figure 3 The magnetic field strength detected by a first magnetic field sensor and a second magnetic field sensor in a first direction and a second direction perpendicular to the first direction is shown for welding processes with different sensor and welding clamp position configurations.

[0055] Figure 4 It shows Figure 3 The normalized magnetic field strength shown is the magnetic field strength of the field.

[0056] Figure 5 The magnetic field strength, detected by a first magnetic field sensor and a second magnetic field sensor in a first direction and a second direction perpendicular to the first direction, is shown for actuator movement with different sensor and welding clamp position configurations.

[0057] Figure 6 It shows Figure 5 The normalized magnetic field strength shown; and

[0058] Figure 7 The magnetic field strength detected by the first and second magnetic field sensors in the X direction and the Y direction perpendicular to the X direction at different locations of the sensor magnet is shown.

[0059] List of reference numerals

[0060] 12 welding devices,

[0061] 14 Welding clamps,

[0062] 16-sensor magnet,

[0063] 18 magnetic field sensors,

[0064] 20 control and evaluation units,

[0065] 22 electrode arms

[0066] 24 electrodes

[0067] 26 x 1 components,

[0068] 28 x 2 components,

[0069] 30 Y1 component,

[0070] 32 Y2 component,

[0071] 34 First total,

[0072] 36 Second sum,

[0073] 38. First angle,

[0074] 40 Second angle,

[0075] 51 Welding Machine

[0076] 52. Workpiece bracket,

[0077] 53. Workpiece. Detailed Implementation

[0078] Figure 1A schematic diagram of a welding apparatus 12 for performing a welding process is shown. The welding apparatus 12 includes: an actuator, here a welding clamp 14, designed to perform a work operation, i.e., the welding process; and a permanent magnet fixed to the welding clamp 14, which serves as a sensor magnet 16. Furthermore, the welding apparatus 12 also includes: at least one magnetic field sensor 18 for detecting the position of the welding clamp 14; and a control and evaluation unit 20. The magnetic field sensor 18 is designed to detect a first magnetic field strength in a first direction and a second magnetic field strength in a second direction perpendicular to the first direction. The control and evaluation unit 20 is connected to the magnetic field sensor 18 and is designed to identify, based on a comparison metric, whether the magnetic field detected by the magnetic field sensor 18 is essentially generated by the sensor magnet 16, the comparison metric correlating the detected first magnetic field strength with the detected second magnetic field strength. If a positive conclusion is reached based on the detected first magnetic field strength and / or the detected second magnetic field strength, the position of the welding clamp 14 is determined, and control commands are issued based on the determined position of the welding clamp 14.

[0079] The welding apparatus 12 can be used, for example, in industrial spot welding processes to join two metal parts together by pressure and current. For example, the welding apparatus 12 is used in automotive manufacturing, steel structures, and other industrial manufacturing processes. The welding clamp 14 includes two electrode arms 22, each electrode arm 22 having an electrode 24 at its end. The electrode arms 22 are used to join two metal parts (not in...) Figure 1 The electrodes (as shown in the image) are pressed together and welding current is introduced into the workpiece at the contact point. Electrodes 24 at the ends of electrode arms 22 are made of a highly conductive material (e.g., a copper alloy) to effectively conduct current while resisting heat generated during welding. The applied current heats the metal at the contact point, causing localized melting and forming a strong welded joint. A sensor magnet 16 is fixed to one of the electrode arms 22, thus allowing the position or orientation of the welding clamp 14 to be determined based on the position of the respective electrode arm 22. In particular, the welding clamp can have, for example,... Figure 1 The closed position is shown, and the open position is not shown. For the open (final) position of the welding clamp 14, for example, corresponding target magnetic field data (Soll-Magnetfelddaten) can be stored for the first magnetic field strength and the second magnetic field strength. When the actual magnetic field data (Ist-Magnetfelddaten) detected by the magnetic field sensor 18 matches the stored target magnetic field data, the control and evaluation unit 20 can determine that the welding clamp 14 is in the open position. This also applies to the closed position and / or intermediate position of the welding clamp 14.

[0080] However, when determining the position of the welding clamp 14, a problem arises because the magnetic field generated by the high current during welding can act as a distracting magnetic field in determining the position of the welding clamp 14. This distracting magnetic field is also detected by the magnetic field sensor 18, so it is necessary to distinguish between the distracting magnetic field and the magnetic field generated by the sensor magnet 16 to prevent the control and evaluation unit 20 from incorrectly determining the position of the welding clamp 14 due to the detected distracting magnetic field. To prevent incorrect determination of the position of the welding clamp 14, a comparison metric is determined that correlates the detected first magnetic field strength with the detected second magnetic field strength, and identifies, based on this comparison metric, whether the magnetic field detected by the magnetic field sensor 18 is essentially generated by the sensor magnet 16. Only in the case of an affirmative conclusion will the position of the welding clamp 14 be determined based on the detected first magnetic field strength and / or the detected second magnetic field strength.

[0081] The distinction between interfering magnetic fields and the magnetic field generated by the sensor magnet 16 is made possible by the fact that the sensor magnet 16 is fixed to the electrode arm 22 of the welding clamp 14, and therefore, the spatial position of the sensor magnet 16 can be changed by moving the electrode arm 22. For example, the spatial position of the sensor magnet 16 can be changed due to the movement of the electrode arm 22, thereby resulting in a magnetic field vector with variable angle and variable magnitude. In contrast, the interfering magnetic field generated by the welding current is a magnetic field with a spatially static origin, emanating from a fixed point in space and changing only over time. Both magnetic fields with spatially static and spatially variable origins can cause the magnetic field sensor to detect changing magnetic field data or magnetic field strength during detection. Unlike magnetic fields with spatially static origins, for magnetic fields with spatially variable origins, the spatial direction of the magnetic field vector changes during detection.

[0082] This difference can be determined based on the detected magnetic field data. If the detected magnetic field strength comes from a time-variable magnetic field with a spatial static origin, then for the first and second detected magnetic field strengths, the changes in the detected magnetic field strength during the detection period are proportional because the changes in the detected magnetic field strength during the detection period have the same cause, namely, the aforementioned increase or decrease in current during the welding process. Therefore, the first and second detected magnetic field strengths are standardized based on the same preset standardization rule, and a comparison metric is used to determine the standardized first and second detected magnetic field strengths. As mentioned earlier, the magnetic field strength is generated in a spatial static magnetic field source; however, a spatial static magnetic field source can have a time-variable magnetic field strength that is proportional to the first and second magnetic field strengths. This is not the case in the case of a spatially variable magnetic field source. Utilizing this understanding, a corresponding standardization rule can be determined to standardize the first and second detected magnetic field strengths to compensate for the proportional effect on the first and second magnetic field strengths. For a time-variable magnetic field with a spatially static origin, applying this normalization rule results in the normalized detected magnetic field strength (i.e., the normalized first detected magnetic field strength and the normalized second detected magnetic field strength) being substantially the same during detection. In other words, the normalized magnetic field distributions for the first and second detected magnetic field strengths are completely consistent. Conversely, applying the same normalization rule to the detected magnetic field strength emitted by the sensor magnet (i.e., a time-static magnetic field with a spatially variable origin) does not result in completely identical detected magnetic field strengths; that is, the corresponding normalized magnetic field distributions are not identical. The variation in the detected magnetic field strength in this case is caused by the variation in the position of the sensor magnet 16, and the variation in the position of the sensor magnet 16 is generally disproportionate in the first direction and the second direction. Thus, in particular, based on the difference between the normalized first detected magnetic field strength and the normalized second detected magnetic field strength, it can be determined whether the magnetic field detected by the magnetic field sensor is a magnetic field generated by the sensor magnet 16.

[0083] In particular, the standardization of the first and second magnetic field strengths is performed by multiplying the corresponding detected magnetic field strengths by the corresponding standardization coefficients calculated based on preset standardization rules.

[0084] For example, Figure 4 and Figure 6 The normalized magnetic field distribution shown in the figure is multiplied by the following normalization factor:

[0085]

[0086] Wherein, the maximum or minimum value corresponds to the maximum or minimum value of the corresponding magnetic field strength detected during the detection period, and the starting or ending value corresponds to the first or last value of the corresponding magnetic field strength detected during the detection period. Further, Figure 4 and Figure 5 The distribution of the comparison metrics shown is as follows:

[0087]

[0088] Wherein, X1(i) or Y1(i) represents the first magnetic field strength detected by the first magnetic field sensor in the first direction and the second magnetic field strength detected in the second direction at time point i, and X2(i) or Y2(i) represents the first magnetic field strength detected by the second magnetic field sensor in the first direction and the second magnetic field strength detected in the second direction at time point i.

[0089] Figure 2 This is a schematic diagram of another welding device. (And...) Figure 1 The difference is, Figure 2 The actuator and welding machine 51 are designed as separate units. Figure 2 In this embodiment, the actuator is a workpiece carrier 52, such as a robotic arm, used to fix and move the workpiece 53. After the workpiece carrier 52 moves the workpiece 53 to a preset position, the welding machine 51, as a separate device, performs welding on the workpiece 53, specifically at the fixed position. Therefore, welding is always performed in the same position. Determining whether the magnetic field detected by the magnetic field sensor 18 is the magnetic field generated by the sensor magnet 16 can be done in the manner described above. In particular, according to this embodiment, it can be determined more simply because the workpiece carrier 52 and the welding machine 51 are designed separately; therefore, the magnetic field generated by welding is completely separate from the magnetic field generated by the sensor magnet 16.

[0090] Figure 3 The diagram illustrates the magnetic field strength detected by a first magnetic field sensor and a second magnetic field sensor in a first direction and a second direction perpendicular to the first direction for welding processes with different sensor and welding clamp position configurations. In this case, the welding apparatus 12 includes two magnetic field sensors 18. The top row shows the magnetic field strength detected at the start of the welding process, and the bottom row shows the magnetic field strength detected at the end of the welding process. Two figures in the same column, or two figures overlapping vertically, belong to the same sensor and welding clamp position configuration.

[0091] Figure 4 The above-mentioned standardized coefficients are shown. Figure 3 The normalized magnetic field strength is shown, along with the distribution of a comparative metric determined based on the normalized magnetic field strength. (As shown in...) Figure 4 It can be recognized that the value of the standardized magnetic field strength is between 0 and 2. Furthermore, throughout the detection period, the values ​​of the comparative metric, especially the maximum value, are essentially close to 0.

[0092] Figure 5 The diagram illustrates the magnetic field strength detected by a first magnetic field sensor and a second magnetic field sensor in a first direction and a second direction perpendicular to the first direction, for movement of welding clamps with different sensor and welding clamp position configurations and different magnetization intensities of sensor magnets. Correspondingly, the diagram shows the magnetic field strength detected by the first magnetic field sensor and the second magnetic field sensor in the first and second directions, respectively, for a specific sensor and welding clamp position configuration and a specific sensor magnetization intensity, during either the activation (i.e., closing) or deactivation (i.e., opening) process of the welding clamp.

[0093] Figure 6 The above-mentioned standardized coefficients are shown. Figure 5 The normalized magnetic field strength is shown, along with the distribution of a comparative metric determined based on the normalized magnetic field strength. (As shown in...) Figure 6 It can be recognized that, with Figure 4 Similar to the standardized magnetic field distribution, the standardized magnetic field strength values ​​range from 0 to 2. Furthermore, for most of the detection period, the values ​​of the comparison metrics (especially the maximum values) are significantly different from 0.

[0094] from Figure 4 and Figure 6 As can be seen, the maximum value of the comparison metric used for the interfering magnetic field generated by the welding process is significantly smaller than the maximum value of the comparison metric used for the magnetic field generated by the sensor magnet 16. Therefore, by setting an appropriate threshold for the maximum value of the comparison metric used for the detected magnetic field, it is easy to determine whether the detected magnetic field is an interfering magnetic field generated by the welding process or a magnetic field generated by the sensor magnet 16. For example, if the threshold is exceeded, it can be determined that the detected magnetic field is a magnetic field generated by the sensor magnet 16, and if the threshold is exceeded, it can be determined that the detected magnetic field is an interfering magnetic field generated by the welding process.

[0095] Figure 7The diagram shows the corresponding sums 34 and 36 for different positions and magnetic intensities of the sensor magnet 16, and the corresponding angles 38 and 40 between the respective magnetic field sensors 18 and the sensor magnet 16. The magnetic field intensities detected in the X direction by the first and second magnetic field sensors are also referred to hereinafter as X1 components 26 and X2 components 28, and the magnetic field intensities detected in the Y direction by the first and second magnetic field sensors are also referred to hereinafter as Y1 components 30 and Y2 components 32. When the welding clamp moves or the sensor magnet moves in the direction of the sensor axis (i.e., through the imaginary line of the two magnetic field sensors 18), the normalized magnetic field distribution does not coincide due to the changing angles and the opposite magnetic field distributions of the mutually perpendicular field components. The Y1 component 30 of the magnetic field, i.e., the magnetic intensity detected by the first magnetic field sensor in the second direction, has its maximum value at the null junction, thus having the point of minimum slope at the null junction. At the zero-crossing point, the X1 component 26 has the maximum slope, and the X1 component 26 represents the magnetic intensity detected by the first magnetic field sensor in the first direction. Similarly, the situation is similar for the poles of the X2 component 28, which represents the magnetic intensity detected by the second magnetic field sensor in the first direction. At the pole location of the X2 component 28, the Y2 component 32 includes a region with the highest slope, and the Y2 component 32 represents the magnetic intensity detected by the second magnetic field sensor in the second direction. These opposing slope regions are clearly shown in the diagram of the normalized magnetic field distribution, where significant deviations exist between the various magnetic field distributions. Figure 7 The diagram also shows a first sum 34 of the magnetic field strength detected by the first magnetic field sensor and a second sum 36 of the magnetic field strength detected by the second magnetic field sensor, the first sum 34 and the second sum 36 being determined based on their respective first and second magnetic field strengths. Furthermore, a first angle 38 between the first magnetic field sensor and the sensor magnet 16 and a second angle 40 between the second magnetic field sensor and the sensor magnet 16 are also shown.

Claims

1. An apparatus for performing a work operation, the apparatus comprising: At least one actuator performs the job operation; A magnetic field source fixed to the actuator; At least one magnetic field sensor (18) is used to detect the position of the actuator, wherein the magnetic field sensor (18) is designed to detect a first magnetic field strength in a first direction and a second magnetic field strength in a second direction perpendicular to the first direction; and A control and evaluation unit (20) is connected to the magnetic field sensor (18), and the control and evaluation unit (20) is designed to identify whether the magnetic field detected by the magnetic field sensor (18) is essentially generated by the magnetic field source based on a comparison metric that correlates a detected first magnetic field strength with a detected second magnetic field strength. If a positive conclusion is reached based on the detected first magnetic field strength and / or the detected second magnetic field strength, the position of the actuator is determined, and a control command is issued based on the determined position of the actuator.

2. The apparatus according to claim 1, characterized in that, The device is a welding device (12).

3. The apparatus according to claim 1, characterized in that, The control and evaluation unit (20) is designed to determine, based on the comparison metric, whether the detected magnetic field is a magnetic field with a static spatial origin or a magnetic field with a variable spatial origin, and if the magnetic field is determined to be a magnetic field with the variable spatial origin, to identify the magnetic field detected by the magnetic field sensor (18) as a magnetic field generated by the magnetic field source.

4. The apparatus according to any one of claims 1 to 3, characterized in that, The control and evaluation unit (20) is designed to determine, based on the comparison metric, whether the detected magnetic field originates from a time-static magnetic field or a time-variable magnetic field, and If it is determined that the detected magnetic field is emitted from the time static magnetic field, then the magnetic field detected by the magnetic field sensor (18) is identified as a magnetic field generated by the magnetic field source.

5. The apparatus according to claim 1, characterized in that, The control and evaluation unit (20) is designed to determine whether the actuator has reached its final position based on sensor data from the magnetic field sensor (18).

6. The apparatus according to claim 1, characterized in that, The control and evaluation unit (20) is designed to standardize the first magnetic field strength and the second magnetic field strength of the detection based on the same preset standardization rules, wherein the comparison metric associates the standardized first magnetic field strength of the detection with the standardized second magnetic field strength of the detection.

7. The apparatus according to claim 6, characterized in that, The comparison metric is based on the difference between the larger of the standardized first magnetic field strength and the standardized second magnetic field strength of the detector and the smaller of the standardized first magnetic field strength and the standardized second magnetic field strength of the detector.

8. The apparatus according to claim 1, characterized in that, The device includes a plurality of magnetic field sensors (18), including two magnetic field sensors (18).

9. The apparatus according to claim 1, characterized in that, The device includes two of the magnetic field sensors (18).

10. The apparatus according to claim 8, characterized in that, The comparison metric is based on the difference between a first magnetic field strength detected by a first magnetic field sensor in the first direction and a first magnetic field strength detected by a second magnetic field sensor in the first direction, or based on the difference between a second magnetic field strength detected by a first magnetic field sensor in the second direction and a second magnetic field strength detected by a second magnetic field sensor in the second direction.

11. The apparatus according to claim 8, characterized in that, The comparison metric is based on the difference between two of the following choices: The magnetic field strength detected by the first magnetic field sensor in the first direction, the magnetic field strength detected by the first magnetic field sensor in the second direction, the magnetic field strength detected by the second magnetic field sensor in the first direction, and the magnetic field strength detected by the second magnetic field sensor in the second direction, are all normalized. The two magnetic field strengths used to form the difference are selected based on the standardized magnetic field strength of the detection that has the largest difference between the minimum and maximum values ​​among the standardized magnetic field strengths during the detection period. Wherein, the minimum value is a determined minimum value of the corresponding magnetic field strength during the detection period, and the maximum value is a determined maximum value of the corresponding magnetic field strength during the detection period.

12. A method for performing a job operation, the method comprising: The position of at least one actuator is detected by at least one magnetic field sensor (18), on which a magnetic field source is fixed. The at least one magnetic field sensor (18) detects a first magnetic field strength in a first direction and a second magnetic field strength in a second direction perpendicular to the first direction. The control and evaluation unit (20) identifies whether the magnetic field detected by the magnetic field sensor (18) is generated by the magnetic field source based on a comparison metric. The control and evaluation unit (20) is connected to the magnetic field sensor (18). The comparison metric correlates the detected first magnetic field strength with the detected second magnetic field strength. as well as If a positive conclusion is reached based on the detected first magnetic field strength and / or the detected second magnetic field strength, the position of the actuator is determined, and a control command is issued based on the determined position of the actuator.

13. The method according to claim 12, characterized in that, The operation described is the welding process.

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