Wear detection on surface suction grippers

Abstract

Method for wear detection of structures (16) arranged on surface suction grippers (10) having a structure height (36), characterized by that the surface suction gripper (10) is pressed against a surface (22, 28, 31), - so that the compressed structure (16) assumes a predefinable structure height (36), and that a force signal is generated that represents the force acting between the surface (22, 28, 31) and the surface suction gripper (10, 100), and / or - so that a predefinable force acts between the surface (22, 28, 31) and the surface suction gripper (10), and that a distance signal is generated that represents the structure height (36) of the compressed structure (16), and / or - that after the structure (16) is detached from the surface (22, 28, 31) a recovery of the structure (16) is determined, and that a deformation signal is generated that represents the recovery of the structure (16), and that a wear signal is generated depending on the force signal, the distance signal and / or the deformation signal, which represents the wear state of the structure (16).

Description

[0001] The invention relates to a method for detecting wear of structures having a structural height, particularly technical foams and / or suction cups, arranged on surface suction grippers. The invention further relates to a surface suction gripper for picking up and handling objects, comprising a base module in which a vacuum chamber capable of being pressurized is provided, and a control unit for controlling the surface suction gripper. The base module has suction openings on a suction side, to which an elastically compressible structure is assigned, with a contact surface for the object to be picked up and a structural height extending perpendicular to the contact surface. During operation, the structure assumes a neutral state when no object is in contact with the contact surface and a compressed state when one or more objects are in contact with the contact surface.

[0002] These types of surface suction grippers are used in particular for gripping and lifting objects with irregular and complex surfaces, especially flat materials with good stability, such as boards or panels, or smaller objects like cans, cups, bowls, or the like. The surface suction gripper has a flexible structure, in particular a coating, which is usually applied to the top surface of the objects to be gripped. A structure made of foam or sealing foam has proven advantageous, as it conforms well to the sometimes uneven surface.

[0003] From DE 10 2006 050 970 A1, surface suction grippers are known in which the structure is in the form of a foam covering with a top layer which has suction openings whose flow cross-section is exactly adapted to the objects to be gripped.

[0004] Similar surface suction grippers with a foam-like structure are known from DE 10 2013 201 249 B4.

[0005] To ensure the safe gripping and lifting of objects, it is essential that the surface suction gripper, and in particular its structure, is in a suitable operating condition. This prevents, for example, gripped objects from being damaged by contact with the structure or by an unforeseen drop. Wear of the structure depends, among other things, on its aging and the number of load cycles. Currently, the structure is inspected manually or in the laboratory. Manual inspection includes, among other things, a visual examination of the structure's condition and its recovery behavior after the operator presses an object or finger into it.During laboratory testing, the compression set, upsetting hardness, indentation hardness, air permeability, and absolute height of the disassembled structure are recorded under reproducible conditions to examine the wear condition. However, in both cases, the operation of the surface suction gripper must be stopped, resulting in significant downtime. Furthermore, manual inspection does not provide reliable results, and laboratory tests represent a disproportionately high cost.

[0006] DE 10 2006 005 872 B3 discloses a suction gripper which has means for indicating the wear condition. Furthermore, DE 10 2005 047 385 A1 describes the detection of a wear limit of a suction gripper.

[0007] The present invention is therefore based on the objective of providing a method for wear detection of the structure of a surface suction gripper, in which reproducible results are achieved and the downtime of the surface suction gripper is reduced due to the wear detection.

[0008] This problem is solved by a method with the features of claim 1. Accordingly, the surface suction gripper is pressed against a surface such that the compressed structure assumes a predefinable structural height. The structural height can essentially be considered the distance between the suction side and the surface of the gripped object. The surface can also be a test surface of a test rig. A force signal is generated that represents the force acting between the surface and the surface suction gripper. Alternatively or additionally, the surface suction gripper is pressed against a surface such that a predetermined or predefinable force acts between the surface and the surface suction gripper. A distance signal is generated that represents the structural height of the structure in its compressed state.Here too, the structure height essentially corresponds to the distance between the suction side and the surface of the gripped object. Alternatively or additionally, the surface suction gripper is first pressed against a surface, and after the structure detaches from the surface, its recovery is measured. This recovery occurs as the structure transitions from the compressed state to the neutral state. A deformation signal is generated, representing the recovery of the structure. This signal can, among other things, depict the recovery as a function of time. Following the generation of the force signal, the distance signal, and / or the deformation signal, a wear signal is generated based on these signals, representing the wear state of the structure.In contrast to wear detection using force and distance signals, wear detection using deformation signals can be applied without additional delay. Generating the force and distance signal, however, introduces a delay due to adjustments to the structure height or suction force.

[0009] It can be assumed that wear of the structure leads to a change in its properties and a change in the gripping parameters. It is conceivable that the structure becomes stiffer with increasing wear, that it returns to its neutral state more slowly after a period of loading, that some plastic deformation remains in the structure, and that the structure exhibits altered fluid permeability. Consequently, the wear state of the structure can be determined by ascertaining these properties and / or their changes.

[0010] To generate the force signal, the principles for determining the compressive stress-deformation properties of polymeric materials according to DIN EN ISO 3386-1 / -2 can be used, whereby, among other things, the compression hardness and indentation hardness are determined. To determine the compression hardness, a square test specimen (parallelpiped) is compressed between two pressure plates, and the force required to compress this test specimen to a specific amount of its original height, e.g., 40%, is measured. The test specimens typically have dimensions of 100 × 100 × 50 mm. 3The test specimen is compressed using pressure plates larger than the specimen itself. This value is then related to the tested area, yielding the compression hardness or compressive strength of the material according to the formula σ = F / A in kPa. For a constant area, the force in N can also be used. In contrast to compression hardness, indentation hardness is determined using pressure plates smaller than the specimen, so only a portion of the specimen is compressed. The specimen can be compressed by, for example, 25%, 40%, or 65%, with the resulting indentation hardness or compression resistance expressed in N or kPa.

[0011] Accordingly, the aforementioned principles can also be applied to generate the distance signal, where the force is set as constant and the distance is set as the quantity to be measured.

[0012] To generate the deformation signal, the compression set of elastomers or foams can be determined according to DIN ISO 815, DIN EN ISO 1856, and DIN 53 517. A test specimen with a known initial height L0 is compressed by, for example, 25% to height L1 and held at a defined temperature for a defined time. The ambient temperature and the medium used for the compression test, e.g., air, oils, and other fluids, depend on the material being tested, its intended application, and the test setup. An example test setup might include the following parameters: 24 hours at 70°C in air. 30 minutes after unloading, the height, in this case height L2, is measured again at room temperature, and the permanent deformation is determined from this measurement. The compression set is calculated as a percentage using the following formula: Compression Set = (L0 - L2) / (L0 - L1) × 100%.A DVR of 0% means that the test specimen has fully regained its original thickness, a DVR of 100% means that the specimen was completely deformed during the test and shows no recovery or re-deformation.

[0013] It is advantageous if the structure exhibits a compression resistance and / or a crush resistance in the range between 1 kPa and 10 kPa, particularly in the range between 1 kPa and 5 kPa, wherein the force and / or distance signal can represent the compression and / or crush resistance. For determining the signals, ambient temperatures between 15°C and 90°C, adjustable structural heights in the compressed state between 0.1 and 0.9 of the structure height in the neutral state, and adjustable forces between 1 N and 1 kN are conceivable. It is further advantageous if the compression set of the structure, after a holding time of 3 s, a height L1 to L0 ratio of 0.9, and a reset time of 1 s, exhibits a compression set between 0% and 10%, particularly between 0% and 2%.To determine the signals, ambient temperatures between 15°C and 90°C, a holding time between 1 s and 60 min, a reset time between 1 s and 60 min, and an L1 to L0 ratio between 0.1 and 0.9 are conceivable. The deformation signal can represent the compression set of the structure.

[0014] The described method enables force-, displacement-, and / or time-dependent wear detection during the main and / or auxiliary phases of the handling process performed with the surface suction gripper. The method involves generating a wear signal based on a force signal, a distance signal, and / or a deformation signal, depending on the operating conditions and environmental influences. It is also conceivable that two of the three signals, or all three signals, are generated alternately to obtain even more reliable results regarding the wear condition. Furthermore, it is conceivable that, depending on the structure, the object, or the environmental conditions, one of the three signals may produce significantly more reliable results regarding the wear condition, so that only this single signal is generated for wear detection in that specific structure.Furthermore, it proves advantageous if multiple signals can be generated, ensuring sufficient redundancy in wear detection.

[0015] It is advantageous to generate the wear signal by comparing the force signal, the distance signal, and / or the deformation signal with an operating range. The operating range represents properties and parameters of the structure that ensure the safe handling of objects. The operating range can include absolute values, whereby structures with different output parameters are evaluated based on the same or individual absolute values. Alternatively, the operating range can include relative values, whereby the operating range is determined depending on the output parameters of the structure, so that a trend line of the wear condition is still possible, especially when absolute limits are unknown. It is conceivable that the output parameters correspond to the force signal, the distance signal, and / or the deformation signal.The initial parameters can be determined at the start of use or to avoid run-in effects after a break-in period of a few load cycles. An operating range with relative values ​​can, in particular, lie between 70% and 110%.

[0016] The wear signal can assume two values, among others: suitable for operation and unsuitable for operation. If the force signal, the distance signal, and / or the deformation signal are within the operating range, the wear signal assumes a value representing a suitable wear condition. In this case, the structure can continue to be used on the surface suction gripper for handling objects.

[0017] If the force signal, the distance signal, and / or the deformation signal are already outside the operating range, the wear signal assumes a value that represents an unsuitable wear condition. In this case, the structure is no longer suitable for use.

[0018] Consequently, a signal is generated that recommends or triggers the replacement of the structure when an unsuitable wear condition occurs. A signal can also be generated that recommends or triggers the replacement of the structure at a future time based on a wear prediction. With multiple signal generations at different times, a wear profile can be determined, enabling a prediction of the time at which an unsuitable wear condition occurs. In this process, the force signal, the distance signal, and / or the deformation signal would continuously approach the limit of the operating range. The closer the signals approach the limit of the operating range, the closer the time at which the unsuitable wear condition occurs. This can be approximated using differential equations, Fourier analysis, etc.Measurements are taken to generate a trend line indicating the wear condition. The intersection of this trend line and the operating range allows for the estimation of the structure's expected service life. For example, a force signal can be generated, representing the force acting on the structure or its compression / indentation hardness. For a given structure, the operating range can be defined as a compression resistance, in conjunction with the compressed area, between 2 kPa and 4 kPa. The force signal is generated at constant intervals, yielding the following values ​​in the specified order: 3.3 kPa, 3.0 kPa, 2.7 kPa, 2.4 kPa, 2.1 kPa. Consequently, it can be assumed that the structure will be outside the operating range at the next measurement interval. Therefore, the structure can be replaced before the next measurement interval.

[0019] This allows for a response to both the steadily increasing wear resulting from normal operation of the surface suction gripper and wear caused by unforeseen events. It is particularly advantageous if both the generation of the wear signal and the replacement of the structure are automated. This ensures that the structure is not operated in an unsuitable wear condition and that it is not replaced prematurely. Alternatively, the force signal, distance signal, deformation signal, wear signal, signal progression, signal trend line, and / or the operating range of the structure can be visualized, enabling an operator to manually assess the wear condition and, based on this assessment, replace the structure as needed.

[0020] The problem underlying the invention is also solved by a method with the features of claim 3. Accordingly, a fluid is conveyed between a contact surface of the structure and a suction side of the surface suction gripper to generate a suction force. The suction force acts on the object to be gripped via the contact surface. Furthermore, a volume flow signal is generated, which represents the permeability of the structure with respect to the conveyed fluid. Depending on the volume flow signal, a wear signal is generated, which represents the wear state of the structure. The corresponding descriptions for wear detection using force, distance, and deformation signals apply here. It is conceivable that wear detection using force, distance, and deformation signals could be supplemented by wear detection using a volume flow signal.

[0021] The method using a volume flow signal enables wear detection during both the main and auxiliary phases of the handling process performed with the surface suction gripper. The method involves generating the volume flow signal depending on the operating conditions and environmental influences. A key advantage is that wear detection can occur without contact with a surface, for example, when approaching and retracting from the object or during handling.

[0022] It is advantageous to compare the volumetric flow rate signal with an operating range to generate the wear signal. The operating range represents properties and parameters of the structure that ensure the safe handling of objects.

[0023] The wear signal can, analogous to the above, assume two values: suitable for operation and unsuitable for operation. If the volume flow signal is within the operating range, the wear signal assumes a value representing a suitable wear condition. In this case, the structure can continue to be used on the surface suction gripper for handling objects. Furthermore, a wear profile can be determined from one or more measurements, which allows for a prediction of the point in time at which a wear condition unsuitable for operation will occur. In this case, the force signal, the distance signal, and / or the deformation signal would steadily approach the limit of the operating range. The closer the signals approach the limit of the operating range, the closer the point in time at which the unsuitable wear condition occurs.

[0024] If the volume flow signal is outside the operating range, the wear signal assumes a value that represents an unsuitable wear condition. In this case, the structure is no longer suitable for use.

[0025] Consequently, a signal is generated that recommends or triggers the replacement of the structure when it reaches an unsuitable wear condition. A signal can also be generated that recommends or triggers the replacement of the structure at a future time based on predicted wear. Therefore, the system can react to both the steadily increasing wear from normal operation of the surface suction gripper and to wear caused by an unforeseen event. It is particularly advantageous if both the generation of the wear signal and the replacement of the structure are automated. This ensures that the structure is not operated in an unsuitable wear condition and that it is not replaced prematurely.

[0026] Furthermore, it is advantageous if the operating range is determined based on the material, nature, and shape of the structure, the material, nature, and weight of the object to be gripped, as well as environmental influences such as ambient temperature, humidity, and pressure. Additionally, the operating range can be determined based on the required safety level. For example, in environments without human intervention, the structure can be used for a longer period up to its absolute wear limit, whereas in environments with human intervention, the structure should be operated with greater safety up to its absolute wear limit. Furthermore, the operating range can also be determined by the gripping situation, particularly the handling method and / or the speed of movement.Consequently, different operating ranges can exist for different structures, different objects to be gripped, different gripping situations, and different combinations thereof. It is also conceivable that the operating range is adjusted during operation by artificial intelligence or manual intervention to optimize the structure's service life. It is conceivable that the operating range is specified as a range between 30% and 120% of the original fluid permeability, particularly between 70% and 100% of the original fluid permeability, where the original fluid permeability can correspond to the state at the time of initial use.

[0027] The problem underlying the invention is also solved by a surface suction gripper with the features of claim 6. Consequently, a force sensor is provided for detecting the force acting between an object resting on the contact surface and the surface suction gripper, and / or a distance sensor is provided for detecting the structure height. Furthermore, the control unit is configured such that when the surface suction gripper is pressed against a surface, the structure assumes a predefinable structure height in the compressed state, and the force sensor generates a force signal representing the force acting between the surface and the surface suction gripper.Alternatively or additionally, the control unit is configured such that when the suction gripper is pressed against a surface, a predefinable force acts between the surface and the suction gripper, and the distance sensor generates a distance signal representing the structure's height in the compressed state. Alternatively or additionally, the control unit is configured such that if the suction gripper is first pressed against a surface and subsequently, after detaching from the surface, the structure returns to its neutral state, the distance sensor generates a deformation signal representing this return to its original state. Furthermore, the control unit is configured to generate a wear signal, dependent on the force signal, the distance signal, and / or the deformation signal, which represents the structure's wear condition.

[0028] An advantageous embodiment provides that the surface suction gripper is pressed against the surface of the object to be gripped. This allows for wear detection on the surface suction gripper without the need for additional peripherals in the area of ​​the gripper, such as a test surface.

[0029] Furthermore, it is advantageous if the force sensor and / or the distance sensor is arranged on the base module and / or on the structure of the surface suction gripper. This allows the surface suction gripper with wear detection function to be used flexibly, independent of the environment and other peripherals.

[0030] Furthermore, it is advantageous if a sensor element is arranged on the structure and the distance sensor on the base module. The distance sensor and the sensor element work together to measure the structure height. It is conceivable that the distance sensor is fixed to the base module and the sensor element moves with the structure. Consequently, the structure height and / or the change in structure height can be determined from the displacement of the sensor element.

[0031] Another advantageous embodiment provides a data storage device that contains a database of operating ranges for the structure. The database can provide multiple operating ranges depending on the material, properties, and shape of the structure; the material, properties, and weight of the object to be gripped; and environmental influences such as ambient temperature, humidity, and pressure. Furthermore, the database can include operating ranges with absolute and / or relative reference values. Consequently, different operating ranges can exist for different structures, different objects to be gripped, and different combinations thereof. The control unit can be configured to determine the structure attached to the suction gripper and the object to be gripped, and then select the appropriate operating range.It is also conceivable that the database can be accessed by artificial intelligence or through manual intervention, allowing the operating ranges to be optimized during operation. Furthermore, the control unit is configured to compare the force signal, the distance signal, and / or the deformation signal with the operating ranges. The control unit also generates a wear signal, which can assume at least two values: suitable for operation, unsuitable for operation. The control unit generates a wear signal that assumes a value representing a suitable wear state when the force signal, the distance signal, and / or the deformation signal are within the operating range. In this case, the structure can continue to be used on the surface suction gripper for handling objects.Furthermore, a wear profile can be determined from one or more measurements, enabling a prediction of the point in time at which an unsuitable wear condition will occur. The force signal, distance signal, and / or deformation signal would then steadily approach the limit of the operating range. The closer the signals get to the limit of the operating range, the closer the point at which the unsuitable wear condition will occur. The control unit generates a wear signal that assumes a value representing an unsuitable wear condition when the force signal, distance signal, and / or deformation signal is outside the operating range. In this case, the structure is no longer suitable for use.Furthermore, it is conceivable that, for reliable determination of the wear condition, several signals at different times—from the force signal, the distance signal, and / or the deformation signal—are compared with the operating range. It is also conceivable that, for reliable determination of the wear condition, several signals of different types are compared with the operating range, in particular a combination of the force signal and the distance signal.

[0032] The problem underlying the invention is also solved by a gripper testing system with the features of claim 11. The gripper testing system includes, among other things, a described surface suction gripper and a test stand. It is advantageous if the force sensor and / or the distance sensor is arranged on the test stand. This arrangement enables the retrofitting of an existing surface suction gripper by means of wear detection of the structure. For this purpose, a test stand is arranged in the area of ​​an existing surface suction gripper, whereby the signal generation can take place in the test stand. It is conceivable that the control unit is also arranged in the test stand and compares the generated signals with a database to determine the wear state of the structure arranged on the surface suction gripper. For this purpose, the control of the surface suction gripper is also necessary, since it must move to predetermined coordinates or coordinates determined by the control unit.The surface suction gripper can also be controlled by the control unit provided on the test bench.

[0033] Advantageously, the surface in contact with the structure is formed by the test surface of the test stand or by the surface of an object to be gripped, with the object being positioned on the test stand. Consequently, when the wear condition is measured by the test stand, the object is located between the surface suction gripper and the test stand. It is conceivable that the test stand is located within the storage area of ​​the objects to be gripped, so that no additional surface is required for wear detection using the test stand. In this case, the existing storage area would be enhanced by the test stand.

[0034] Furthermore, it is conceivable that a display for visualizing the force signal, the distance signal, the deformation signal, the wear signal, the signal profiles, the signal trend line and / or the operating range of the structure, particularly on the surface suction gripper, is provided, so that an employee can also manually assess the wear condition and, on this basis, change the structure.

[0035] The problem underlying the invention is also solved by a surface suction gripper with the features of claim 13. The surface suction gripper conveys a fluid between the contact surface of the structure and the suction side of the gripper to generate the suction force. Furthermore, a volumetric flow sensor is provided to record the volumetric flow rate of the fluid. The volumetric flow sensor generates a volumetric flow rate signal that represents the fluid permeability of the structure. The volumetric flow rate sensor can also be designed as a (negative) pressure sensor, whereby, in conjunction with a known vacuum generator and its known characteristic curve according to q = f(pU), the volumetric flow rate can be determined by measuring the (negative) pressure. The control unit is configured such that it generates a wear signal as a function of the volumetric flow rate signal, which represents the wear state of the structure.To measure the wear condition using a volume flow sensor on the surface suction gripper, it is not necessary to press the structure against a surface before, during, or after the measurement. Consequently, wear detection can be performed at any time and without preparation.

[0036] Another advantageous embodiment provides a data storage device that contains a database of operating ranges for the structure. The database can provide multiple operating ranges depending on the material, properties, and shape of the structure; the material, properties, and weight of the object to be gripped; and environmental influences such as ambient temperature, humidity, and pressure. Consequently, different operating ranges can exist for different structures, different objects to be gripped, and different combinations thereof. It is also conceivable that the database can be accessed by artificial intelligence or manually, allowing the operating ranges to be optimized during operation. Furthermore, the control unit is configured to compare the volumetric flow signal with the operating ranges.Furthermore, the control unit generates a wear signal that can assume at least two values: suitable for operation, unsuitable for operation. The control unit generates a wear signal that assumes a value representing a suitable wear condition when the force signal, the distance signal, and / or the deformation signal are within the operating range. In this case, the structure can continue to be used on the surface suction gripper for handling objects. Additionally, a wear profile can be determined from one or more measurements, which allows for a prediction of the point in time at which a wear condition unsuitable for operation will occur. In this case, the volume flow signal would steadily approach the limit of the operating range. The closer the signals approach the limit of the operating range, the closer the point in time at which the wear condition unsuitable for operation will occur.The control unit generates a wear signal, which assumes a value representing an unsuitable wear condition when the volume flow signal is outside the operating range. In this case, the structure is no longer suitable for use. Furthermore, it is conceivable that, for reliable determination of the wear condition, several signals could be compared at different times between the volume flow signal and the operating range.

[0037] Further details and advantageous embodiments of the invention can be found in the following description, which describes and explains various exemplary embodiments in more detail.

[0038] They show: Fig. 1A a surface suction gripper known from the prior art when approaching an object to be gripped (foam recovery time); Fig. 1B a surface suction gripper according to Fig. 1A during suction and pressing of the object (foam loading time); Fig. 1C a surface suction gripper according to Fig. 1A when lifting and handling the object (foam loading time); Fig. 1D a surface suction gripper according to Fig. 1A when placing the object (foam exposure time); Fig. 1E a surface suction gripper according to Fig. 1A when loosening / blowing off the object (foam exposure time); Fig. 1F a surface suction gripper according to Fig. 1A when lifting from the object (foam recovery time); Fig. 2A a gripping test system according to the invention with a test stand for wear detection and a surface suction gripper according to Fig. 1A when approaching the test surface; Fig. 2B a gripping test system according to Fig. 2A with a surface suction gripper according to Fig. 1A during suction and pressing against the test surface; Fig. 2C a gripping test system according to Fig. 2A with a surface suction gripper according to Fig. 1A after loosening / blowing off and lifting from the test surface; Fig. 3A a gripping test system according to the invention with a test stand for wear detection and a surface suction gripper according to Fig. 1A when approaching an object to be grasped that is arranged on the test surface; Fig. 3B a gripping test system according to Fig. 3A with a surface suction gripper according to Fig. 1A during suction and pressing against the object; Fig. 3C a gripping test system according to Fig. 3A with a surface suction gripper according to Fig. 1A after loosening / blowing off and lifting from the object; Fig. 4A a surface suction gripper according to the invention with wear detection by means of a force sensor and distance sensor on the base module when approaching a floor surface; Fig. 4B a surface suction gripper according to Fig. 4A during suction and pressing against a floor surface; Fig. 4C a surface suction gripper according to Fig. 4A after loosening / blowing off and lifting from the ground surface; Fig. 5A a surface suction gripper according to the invention with wear detection by means of a force sensor and distance sensor on the base module when approaching an object to be gripped arranged on a floor surface; Fig. 5B a surface suction gripper according to Fig. 5A when suctioning and pressing against an object surface; Fig. 5C a surface suction gripper according to Fig. 5A after loosening / blowing off and lifting from the object surface; Fig. 6A a gripping test system according to the invention with a surface suction gripper according to the invention with wear detection by means of a force sensor and distance sensor on the base module and on the test stand when approaching a test surface; Fig. 6B Gripping test system according to Fig. 2A and surface suction gripper according to Fig. 6A during suction and pressing against the test surface; Fig. 6C Gripping test system according to Fig. 2A and surface suction gripper according to Fig. 6A after loosening / blowing off and lifting from the test surface; Fig. 7A a surface suction gripper according to the invention with wear detection by means of a volume flow sensor when approaching a floor surface; Fig. 7B a surface suction gripper according to Fig. 7A during suction and pressing against a floor surface; and Fig. 7C a surface suction gripper according to Fig. 7A after loosening / blowing off and lifting from the ground surface.

[0039] In the Fig. Figures 1A to 1F show a surface suction gripper 100 known from the prior art for gripping objects 12. The surface suction gripper 100 comprises a base module 14 and an elastically compressible structure 16, wherein the base module 14 provides a vacuum chamber that can be pressurized with negative pressure and the base module 14 has suction openings (not shown) on a suction side 18. The structure 16 is arranged on the suction side 18 and has a contact surface 20 for contacting the object 12 to be suctioned. The object 12 has a surface 22 which comes into contact with the contact surface 20 of the structure 16 during handling.

[0040] The handling cycle of the surface suction gripper 100 is described below. Fig. 1A to 1F described. In Fig. 1A The surface suction gripper 100 is positioned and approached in the area of ​​the object 12 to be gripped. The structure 16 is in its foam recovery phase, as it is neither loaded nor compressed. Fig. Figure 1B shows how the surface suction gripper 100 comes into contact with the object surface 22 with its contact area 20. The structure 16 is compressed due to the object 12 and a suction force emanating from the surface suction gripper 100. The surface suction gripper 100 provides a sufficiently high suction force so that the object 12 is compressed according to Fig. 1C can be lifted and transported. Once the object 12 is at the intended destination, it is lifted by the surface suction gripper 100 according to Fig. 1D stored. To release the force-fit connection between the surface suction gripper 100 and the object 12, the vacuum generator can be switched off, whereby the connection is vented by the unavoidable leakage and the vacuum is destroyed. Alternatively, the object 12 is actively blown off, as in Fig. As can be seen in Figure 1E. A blowing force acting against the suction force is generated by the surface suction gripper 100. From the moment the gripper approaches the object 12 until the object 12 is released or actively blown off, the structure 16 is compressed (foam loading time). Subsequently, as shown in Figure 1E, the structure 16 is compressed. Fig. As can be seen in section 1F, the surface suction gripper 100 has moved away. After the object 12 has been detached or actively blown off, the structure 16 is again in the foam recovery phase and essentially returns to its original shape.

[0041] In the Fig. Figures 2A to 7C show embodiments of the surface suction grippers 10 and the gripper testing systems 24 according to the invention, as well as the method for wear detection of structures 16 arranged on the surface suction grippers 10. The components shown therein, which are known from the prior art, are identified by the corresponding reference numerals according to the Fig. labeled 1A to 1F.

[0042] In the Fig. Figures 2A to 2C show a gripper testing system 24 comprising a surface suction gripper 100 known from the prior art and a test stand 26. The test stand 26 is suitable for extending any surface suction gripper 100 by adding a wear detection function to the structure 16. The test stand 26 has a test surface 28, which can be brought into contact with the contact surface 20. Furthermore, the test stand 26 has a force sensor 30 and a distance sensor 32, wherein the force sensor 30 and the distance sensor 32 are arranged below the test surface 28. The distance sensor 32 is directed towards the contact surface 20 of the structure 16 and can therefore detect the distance between the test surface 28 and the contact surface 20. Alternatively or additionally, the distance sensor 32 can be directed towards the suction side 18 and thus detect the distance between the test surface 28 and the suction side 18.The distance sensor 32 generates a distance signal representing the distance. The force sensor 30 is arranged in the direction of the force acting between the surface suction gripper 100 and the test surface 28, and the force sensor 30 is designed to detect this force. The force sensor 30 generates a force signal representing the force.

[0043] The Fig. Sections 2A to 2C also show how a load cycle affects structure 16. Fig. Figure 2A shows that the structure 16 has a completely cuboid shape in its unloaded neutral state. The distance between the suction side 18 and the contact surface 20 can be referred to as the structure height 36. When the contact surface 20 comes into contact with a surface, the structure 16 is compressed, thus entering a state of compression and reducing its structure height 36 by up to 90%. As soon as the force exerted on the structure 16 by a surface decreases, the structure 16 deforms back to its neutral state, leaving a residual compression set in the structure 16 over time. Consequently, it can be assumed that the structure height 36 in Fig. 2A greater than the structure height 36 in Fig. 2C is.

[0044] A control unit 34 is provided on the test bench 26 for processing the signals generated by the force sensor 30 and the distance sensor 32. For wear detection, the control unit 34 controls the surface suction gripper 100 so that it moves to a predefined measuring position. Fig. In Figure 2B, the surface suction gripper 100 is in the measuring position required for testing. This position is characterized by the fact that the surface suction gripper 100, or rather its suction side 18, has a predetermined distance to the test surface 28. Consequently, the structure 16 has a defined structural height 36, which corresponds to the distance between the test surface 28 and the suction side 18. The defined structural height 36 is shown in Fig. Fig. 2B can be in the range between 0.1 and 0.9 of the original structure height 36 according to Fig. 2A. To determine the actual structure height 36, the distance sensor 32 can detect the distance between the suction side 18 and the test surface if a low tolerance is required for the defined structure height 36.

[0045] Once the suction gripper 100 has assumed the measuring position, a force is exerted by the suction gripper 100, via the structure 16, on the test surface 28, which can be detected by the force sensor 30. With increasing wear, the structure 16 may exhibit reduced deformability and higher compression resistance. In this case, the force exerted by the suction gripper 100 on the test surface 28 increases in order to compress the structure 16 and move the suction gripper 100 into the measuring position. It is also conceivable that the structure 16 loses its dimensional stability and consequently exhibits a significantly lower compression resistance as a result of wear. In this case, the acting force would be significantly lower.The control unit 34 is configured to compare the force measured by the force sensor 30 with the operating range stored in a database, which is also managed, or can be managed, by the control unit 34. The operating range comprises a range of permissible forces or compression resistances or upsetting hardnesses required for the structure 16 to move the surface suction gripper 100 into the measuring position when it is in a suitable operating condition. If the measured force is no longer within the operating range, for example, because the maximum permissible force has been exceeded or the minimum permissible force has been undershot, the control unit 34 generates a wear signal with a value representing a less suitable wear condition of the structure 16. Otherwise, the control unit 34 generates a wear signal with a value representing a suitable wear condition of the structure 16.This measuring method is based on the principles of determining the compression hardness of elastomers, whereby the force required to compress the elastomer to a specific fraction of its original height is measured. Similarly, the principles of determining indentation hardness are also applicable, wherein the object 12 has a smaller cross-section than the structure 16. It is conceivable that the forces are directly determined and compared by the control unit 34, or that the forces are related to the area of ​​the structure 16 that is compressed, thus substantially reducing the structure height 36. The operating range for an area-related compression hardness or compression resistance of the structure 16 is between 1 kPa and 7 kPa, and preferably between 2 kPa and 4 kPa.

[0046] In the Fig. Figures 3A to 3C show a gripper testing system 24, in contrast to the gripper testing system 24. Fig. 2A to 2C, an object surface 22 serves for contacting the contact surface 20. Based on the gripper testing system 24 of the Fig. Sections 3A to 3C describe wear detection when a defined force is applied to the object surface 22. To determine the wear state, the surface suction gripper 100 is moved such that a defined force is applied from the surface suction gripper 100, via the structure 16 and the object 12, to the test surface 28 of the test stand 26. The force sensor 30 detects the applied force. The control unit 34 is configured to control the surface suction gripper 100 in such a way that constant force ratios are applied. When the structure 16 is compressed at a constant force, the distance sensor 32 generates a distance signal representing the distance between the suction side 18 and the object surface 22, or the structure height 36. The control unit 34 accesses the database containing the operating range of the structure 16 in use.The control unit 34 is aware of the environmental conditions, such as temperature, humidity, and pressure, as well as the properties of the structure 16 and the object 12. Based on this information, the control unit 34 selects the corresponding operating range. If the distance signal lies within the operating range, the control unit 34 is configured to generate a wear signal with a value representing an acceptable wear condition. If the distance signal lies outside the operating range, the control unit 34 is configured to generate a wear signal with a value representing an unacceptable wear condition. Depending on the defined force, the operating range lies between 0.01 and 0.9 of the original structure height 36. The original structure height 36 can be either the structure 16 without wear or the structure height 36 before the last load cycle. Fig. 3A corresponds

[0047] The measurement method using residual deformation of the structure 16 for wear detection is applied when the distance sensor 32 is directed at the contact surface 20 of the structure 16. In this case, the distance sensor 32 detects the distance between the test surface 28 and the contact surface 20. By measuring at two points in time, a change in the structure height 36 can be detected by the distance sensor 32. For this purpose, the surface suction gripper 100 is moved to a predefined position in which the structure 16 is in a neutral state. The distance sensor 32 detects the distance to the contact surface 20 and generates a distance signal, which is stored by the control unit 34. Subsequently, the surface suction gripper 100 is pressed against the object surface 22 so that the structure 16 is deformed as described in the previous measurement. Fig. 3B 25% of the original structure height 36 as in Fig. 3A. The compression range of structure 16 can be between 0.1 and 0.9. Structure 16 is held in this compressed state for a defined period, which can be between 1 second and 60 minutes. Subsequently, the surface suction gripper 100 returns to its previous position according to Fig. 3A, in which the structure 16 assumes a neutral state by returning to its original deformation. After a defined period, in particular 1 s to 60 min, following the unloading of the structure 16, the distance sensor 32 again measures the distance between the test surface 28 and the contact surface 20. This results in a residual deformation in the structure 16, which has not yet returned to its original deformation after the defined period. The control unit 34 is configured to select the operating range corresponding to the structure and the gripping object from the database. In this case, the operating range encompasses a range for a permissible compression set. If the deformation signal lies within the operating range, a suitable wear signal is generated. If the deformation signal lies outside the operating range, a wear signal unsuitable for operation is generated.

[0048] In the Fig. Figures 4A to 4C show a surface suction gripper 10 according to the invention. In this case, wear detection is provided within the surface suction gripper 10. The force sensor 30 and the distance sensor 32 are arranged on the base module 14. The force sensor 30 is located in the direction of the force acting between the surface suction gripper 10 and the adjacent floor surface 31. The force sensor 30 is designed such that it generates a force signal representing the acting force. The distance sensor 32 is directed from the suction side 18 towards the structure 16. The distance sensor 32 interacts with a sensor element 38 arranged in the area of ​​the contact surface 20 on the structure 16 to detect the structure height 36. The control unit 34 can also be arranged in the surface suction gripper 10 to determine the wear signal as a function of the force signal, the distance signal, and / or the deformation signal. Fig. The wear detection methods described in 2A to 4C are accordingly applied to the surface suction gripper 10 in the Fig. Applicable to 4A to 4C. The arrangement of the force sensor 30 and the distance sensor 32 on the surface suction gripper 10 allows for flexible use of the surface suction gripper 10, as no additional peripherals are required for wear detection.

[0049] In the Fig. 5A to 5C is a the Fig. 4A to 4C show corresponding surface suction grippers, wherein the test procedures are carried out by pressing against an object 12.

[0050] In the Fig. Figures 6A to 6C show a redundant system with a gripper test system 24 and a surface suction gripper 10, wherein both the surface suction gripper 10 and the test stand 24 are equipped with a force sensor 30 and a distance sensor 32. Consequently, wear detection of the structure 16 can be ensured even if one of the sensors fails.

[0051] A cycle-independent method for wear detection is available with the surface suction gripper 10. Fig. Figures 7A to 7C show the surface suction gripper 10 incorporating wear detection by means of a volume flow sensor 10. The volume flow sensor 10 is located in the area of ​​the base module 14 and is configured to determine the volume flow required to generate the suction force. The volume flow sensor 10 then generates a volume flow signal representing the volume flow. The volume flow signal is directly related to the fluid permeability of the structure 16. Furthermore, a control unit 34 is provided, which generates a wear signal depending on the volume flow signal and can initiate further measures regarding the structure 16. The volume flow signal can be generated both in the unloaded neutral state according to Fig. 7A and Fig. 7C as well as in the loaded compression state according to 7B.

[0052] The illustrated embodiments enable wear detection during the main and auxiliary operating times of the surface suction gripper 100. Once several measurements have been taken for wear detection, a wear profile can be determined by the control unit 34, allowing the control unit 34 to predict the point of failure of the structure 16. Furthermore, automatic replacement of the structure 16 is enabled if the control unit generates an unsuitable wear signal and, as a result, initiates the replacement of the structure 16.

Claims

[1] Method for wear detection of structures (16) arranged on surface suction grippers (10) having a structure height (36), characterized by , that the surface suction gripper (10) is pressed against a surface (22, 28, 31), - so that the compressed structure (16) assumes a predefinable structure height (36), and that a force signal is generated that represents the force acting between the surface (22, 28, 31) and the surface suction gripper (10, 100), and / or - so that a predefinable force acts between the surface (22, 28, 31) and the surface suction gripper (10), and that a distance signal is generated that represents the structure height (36) of the compressed structure (16), and / or - that after the structure (16) is detached from the surface (22, 28, 31) a recovery of the structure (16) is determined, and that a deformation signal is generated that represents the recovery of the structure (16), and that a wear signal is generated depending on the force signal, the distance signal and / or the deformation signal, which represents the wear state of the structure (16). [2] Method according to claim 1, characterized by, that to generate the wear signal, the force signal, the distance signal and / or the deformation signal is compared with an operating range, wherein the wear signal then represents an operationally suitable wear condition if the force signal, the distance signal and / or the deformation signal is within the operating range, and / or wherein the wear signal then represents an operationally unsuitable wear condition if the force signal, the distance signal and / or the deformation signal is outside the operating range. [3] Method for wear detection of structures (16) arranged on surface suction grippers (10), wherein a fluid is conveyed between a contact surface (20) of the structure (16) for contact with an object (12) to be gripped and the surface suction gripper (10) to create a suction force, characterized by, that a volume flow signal is generated which represents the permeability of the structure (16) with respect to the conveyed fluid, and that a wear signal is generated depending on the volume flow signal which represents the wear state of the structure (16). [4] Method according to claim 3, characterized by , that to generate the wear signal the volume flow signal is compared with an operating range, wherein the wear signal then represents a wear condition suitable for operation if the volume flow signal is within the operating range, and / or wherein the wear signal then represents a wear condition unsuitable for operation if the volume flow signal is outside the operating range. [5] Method according to claim 2 or 4, characterized by, that the operating range is determined depending on the structure (16), the nature and weight of the gripping object (12) and / or depending on the environmental conditions. [6] Surface suction gripper (10) for suction and handling of objects (12) with a base module (14) in which a vacuum chamber that can be pressurized with negative pressure is provided, and with a control unit (34) for controlling the surface suction gripper (10), wherein the base module (14) has suction openings on a suction side (18), wherein the suction side (18) is associated with an elastically compressible structure (16) with a contact surface (20) for contact with the object (12) to be suctioned and with a structure height (36) extending perpendicular to the contact surface (20), wherein in operation in which no object (12) is in contact with the contact surface (20), the structure (16) assumes a neutral state, and wherein in operation in which an object (12) is in contact with the contact surface (20), the structure (16) assumes a compressed state, characterized by , that a force sensor (30) is provided to record the force acting between an object (12) resting on the support surface (20) and the surface suction gripper (10), and / or that a distance sensor (32) is provided for recording the structure height (36), and that the control unit (34) is set up in such a way, that when the surface suction gripper (10) is pressed against a surface (22, 28, 31), - the structure (16) assumes a predefinable structure height (36) in the compressed state, and that the force sensor (30) generates a force signal representing the force acting between the surface (22, 28, 31) and the surface suction gripper (10), and / or - a predefinable force acts between the surface (22, 28, 31) and the surface suction gripper (10), and that the distance sensor (32) generates a distance signal that represents the structure height (36) of the structure (16) in the compressed state, and / or - following the detachment of the structure (16) from the surface (22, 28, 31), a re-deformation of the structure (16) into the neutral state takes place, and that the distance sensor (32) generates a deformation signal that represents the re-deformation of the structure (16), and that the control unit (34) is configured to generate a wear signal depending on the force signal, the distance signal and / or the deformation signal, which represents the wear state of the structure (16). [7] Surface suction gripper (10) according to claim 6, characterized by , that the adjacent surface is formed by an object surface (22) of an object (12) to be grasped. [8] Surface suction gripper (10) according to claim 6 or 7, characterized by , that the force sensor (30) and / or the distance sensor (32) is arranged on the base module (14) and / or on the structure (16). [9] Surface suction gripper (10) according to claim 6, 7 or 8, characterized by , that a sensor element (38) is arranged on the structure (16), wherein the sensor element (38) interacts with the distance sensor (32) to measure the structure height (36). [10] Surface suction gripper (10) according to one of claims 6 to 9, characterized by, that a data storage device is provided which provides a database with operating ranges of the structure (16), and that the control unit (34) is configured to compare the force signal, the distance signal and / or the deformation signal with the operating ranges, wherein the control unit (34) generates a wear signal which then represents an operationally suitable wear condition if the force signal, the distance signal and / or the deformation signal is within the operating range, and / or wherein the control unit generates a wear signal which then represents an operationally unsuitable wear condition if the force signal, the distance signal and / or the deformation signal is outside the operating range. [11] Gripper testing system (24) with a surface suction gripper (10) according to one of claims 6 and 8 to 10 and a test stand (26), characterized by, that the force sensor (30) and / or the distance sensor (32) is arranged on the test bench (26). [12] Gripper testing system (24) according to claim 11, characterized by , that the test stand (26) has a test surface (28), and that the adjacent surface is formed by the test surface (28), or that the adjacent surface is formed by an object surface (22) of an object (12) to be gripped, which is positioned on the test surface (28). [13] Surface suction gripper (10) for suction and handling of objects (12) comprising a base module (14) in which a vacuum chamber that can be pressurized with negative pressure is provided, and a control unit (34) for controlling the surface suction gripper (10), wherein the base module (14) has suction openings on a suction side (18), wherein the suction side (18) is associated with an elastically compressible structure (16) with a contact surface (20) for contact with the object (12) to be suctioned, wherein a fluid is conveyed between the contact surface (20) and the suction side (18) to generate the suction force, characterized by , that a volume flow sensor (40) is provided to record the volume flow of the fluid, that the volume flow sensor (40) generates a volume flow signal representing the fluid permeability of the structure, and that the control unit (34) is configured to generate a wear signal depending on the volume flow signal, which represents the wear state of the structure (16). [14] Surface suction gripper (10) according to claim 13, characterized by , that a data storage device is provided which provides a database with operating ranges of the structure (16), and that the control unit (34) is configured to compare the volume flow signal with the operating ranges, wherein the control unit (34) generates a wear signal which then represents an operationally suitable wear condition if the volume flow signal is within the operating range, and / or wherein the control unit generates a wear signal which then represents an operationally unsuitable wear condition if the volume flow signal is outside the operating range.

Images