WO2013068115A1

WO2013068115A1 - Method for operating a vacuum gripping device, vacuum control device and manipulator

Info

Publication number: WO2013068115A1
Application number: PCT/EP2012/004642
Authority: WO
Inventors: Dietmar Wagner
Original assignee: Festo Ag & Co. Kg
Priority date: 2011-11-10
Filing date: 2012-11-08
Publication date: 2013-05-16
Also published as: CN104204542B; DE102011118173B4; DE102011118173A1; CN104204542A; KR102000314B1; KR20140101348A

Abstract

The invention relates to a method for operating a vacuum gripping device (1) which comprises a vacuum gripper (4), a processing device (32), a sensor device (33) for providing a fluid-related and/or vacuum-related sensor signal, and a fluid control valve (24; 45, 46) which can be actuated by the processing device (32) in order to provide a vacuum to the vacuum gripper (4), wherein the processing device (32) is configured for processing the sensor signal and for actuating the fluid control valve (24; 45, 46), having the following steps: outputting of a control signal to the fluid control valve (24; 45, 46), determining of a change speed for the sensor signal which is output by the sensor device (33), and provision of a status signal to an external communications system (15) which is configured for communication with a machine controller (13), in order to bring about a change in a movement state of the vacuum gripper (4) by way of the status signal when the determined change speed corresponds to a predefinable minimum value or lies in a predefinable value interval.

Description

Method for operating a vacuum gripping device,

Vacuum control device and manipulator

The invention relates to a method for operating a vacuum gripping device, the vacuum gripper, a processing device, a sensor device for providing a fluid and / or vacuum-related sensor signal and a controllable by the processing fluid control valve to provide a fluid flow, preferably a vacuum, in particular a vacuum and an overpressure, to the vacuum gripper, wherein the processing device is designed for processing the sensor signal and for controlling the fluid control valve. Furthermore, the invention relates to a vacuum control device and a manipulator.

From DE 10 2007 061 820 Al a vacuum generating device is known, which has an ejector device which is connected to a suction channel connected to a suction pad. To the suction channel, a pressure detection device is connected, which communicates with a control electronics. The device allows the implementation of a method in which the evacuation time and / or the ventilation time of the suction channel is detected and compared with at least one reference time value in order to generate an electrical diagnostic signal as a function of the comparison result. DE 10 2007 058 114 A1 discloses a vacuum generating device and a method suitable for its operation. An ejector device is connected at its inlet to an air supply duct, which can optionally be shut off or released by an electronic control device to selectively switch off or on the ejector device. When the ejector device is switched on, a negative pressure is generated in a suction channel. The ejector device is operated so that the negative pressure between an upper switching value and a lower switching value oscillates. By comparison with a reference time value, the operating time of the ejector device is determined in order to generate a diagnostic signal that indicates the presence of leakage.

The object of the invention is to provide a method for operating a vacuum gripper and a vacuum control device and a manipulator, which allow faster handling of workpieces compared to the prior art

This object is achieved according to a first aspect of the invention for a method of the type mentioned above with the features of claim 1. Here are the following

Providing a control signal from the processing device to the fluid control valve at a drive time, determining a rate of change for the sensor signal output by the sensor device in correlation to a fluid and / or vacuum related physical value, and providing a status signal to an external communication system suitable for one Communication with a machine control is designed to cause by the status signal, a change of a movement state of the vacuum gripper, if the determined change rate speed corresponds to a predefinable minimum value or is within a predefinable value interval.

By taking into account the rate of change for the sensor signal, the change of a physical

Value represents, in particular a pressure value at the vacuum gripper, a reliable prediction is already possible in an early stage of the gripping process, whether the gripping operation will succeed. Typically, upon successful gripping of a workpiece with the vacuum gripper, movement of the vacuum gripper and the workpiece received thereon is provided, for example, to relocate the workpiece from a first location to a second location. In the method according to the invention, the status signal, which informs the machine control that a movement of the vacuum gripper can now take place, can already take place upon determination of a match of the rate of change with the predefinable minimum value or the predefinable value interval and thus at an early point in time during the gripping process. Between the output of the status signal and the actual start of the movement of the vacuum gripper, there is a period of time, which is also referred to as dead time, determined in particular by data transmission times between processing device, machine control and associated actuator, a processing time of the status signal in the machine control and a mechanical inertia of the actuator can. In the method according to the invention, the dead time inherently present for the completion of the gripping operation is used, since it can be predicted at an early date with high certainty, whether the gripping process is completed successfully or not and only in predicted success, the status signal is output. Thus, the time span from the activation time for the fluid control shortened valve until the actual movement of the vacuum gripper.

Advantageous developments of the invention are specified in the subclaims.

In a development of the invention, it is provided that an idling pressure value is determined by the processing device at a point in time at which the vacuum gripper does not bear against a workpiece. In this way, it can be checked whether the fluid control valve which is provided for providing a vacuum to the vacuum gripper is working correctly and / or there is possibly a malfunction in the fluidic lines between fluid control valve and vacuum gripper and / or directly on the vacuum gripper. This can be determined, for example, by comparing the idling pressure value with a predefinable idling pressure limit value stored in the processing device. If the idle pressure limit value is exceeded, in particular after a predefined waiting time has elapsed after a corresponding activation of the fluid control valve, an initiation of the gripping operation by the processing device can be prevented by way of example. This error can occur if due to inadequacy of the

Vacuum gripper device, for example, by contamination or damage of suction cups on the vacuum gripper and / or contamination or damage of suction lines to the vacuum gripper and / or contamination of suction filters within a given period of time, the required pressure reduction on the vacuum gripper, for example, starting from an ambient pressure is not achieved. In this case, it is therefore unlikely that a vacuum on the vacuum gripper will set when the vacuum gripper contacts the workpiece, which will allow reliable gripping of the workpiece suitable is. Accordingly, then no status signal is output, which would lead to a movement of the vacuum gripper.

It is expedient for the processing device to determine a minimum pressure value during a vacuum gripping process which occurs when the vacuum gripper bears against the workpiece. The minimum pressure value, which corresponds in particular to the lowest pressure which arises during the gripping process in the vacuum gripper, depends in particular on the state of the vacuum gripper, on the nature of the workpiece to be gripped, on the function of the fluid control valve and the condition of the fluid lines , in particular between fluid control valve and vacuum gripper. The minimum pressure value is compared with a predefinable minimum pressure limit value stored in the processing device. If the minimum pressure limit value is not undershot during the gripping process, ie no minimum pressure value is set which is smaller than the predefinable minimum pressure limit value, it must be assumed that the required gripping force between the vacuum gripper and the workpiece does not reach the intended level. Accordingly, it can be provided for this case, to slow down the movement of the vacuum gripper and / or bring the workpiece as quickly as possible in a non-critical position, in particular stop, and / or issue an error message from the processing device to the machine control to prevent another gripping operation or to inform a user of the vacuum gripper device.

It is advantageous if the minimum value or the value interval for the rate of change of the sensor signal is adjusted as a function of the idling pressure value and / or the minimum pressure value. As a result, in particular Within a predeterminable interval, the gripping operation negatively influencing factors such as the wear of the vacuum gripper and / or the fluid valve and / or the gripping process favoring factors such as taking place by wear, at least temporarily advantageous geometric adaptation of the vacuum gripper to the workpiece to be gripped in the prediction of the Success of the grasping process. As a result, the behavior of the processing device can be continuously adapted to changes in the gripper system, which essentially consists of the fluid valve, the vacuum gripper and the workpiece.

In a further embodiment of the invention, it is provided that an output of a warning message from the processing device takes place when the idle pressure value above a predetermined idle limit value and / or the minimum pressure value above a predetermined minimum pressure limit. As a result, gripping operations are to be avoided in which it is foreseeable that the desired gripping success will not occur.

Preferably, the status signal is provided by the processing device only if the rate of change for the sensor signal longer than a predeterminable minimum time interval with the predetermined minimum value or the predetermined value interval coincides and / or if within a predetermined period of time from the output of the control signal from the processing device to the Fluid control valve was reached at the time of actuation a minimum value for the sensor signal. This avoids that a positive assessment of the gripping process takes place even if the predetermined rate of change is brief, which could lead to the provision of the status signal for the initiation of the movement on the vacuum gripper. He- According to the invention, it is provided to provide a status signal only when a predefinable value for the rate of change is reached or exceeded within a predefinable time interval. The time interval is preferably a wandering time window which is opened when the predetermined minimum value is reached for the first time and either closed again if the rate of change falls below the predetermined minimum value again or if the predetermined time interval is reached for providing the status message. Additionally or alternatively, it may be provided that, in addition to considering the rate of change, reaching a minimum value for the sensor signal within a predeterminable time interval is also considered in order to make it possible to reliably predict the success of the gripping process.

The object of the invention is achieved according to a second aspect with the features of claim 7. In this case, a vacuum control device is provided with a fluid connection for a fluid supply, with a fluid outlet for the provision of a fluid and / or a vacuum to a consumer, with a processing device that is capable of processing at least one fluid and / or vacuum-related sensor signal and for providing is formed by control signals and with a controllable by the control signals fluid control valve which is connected to the fluid port or to the fluid port and the fluid outlet, and / or with a vacuum control valve which is connected to the fluid port and the fluid outlet, to provide a temporary To allow fluid and / or vacuum at the fluid outlet. According to the invention, the processing device is designed for ascertaining a rate of change for the sensor signal output by the sensor device in correlation to a fluid and / or vacuum-related physical value and for providing a status signal to an external communication system which serves for communication with a machine control. if, in accordance with the determined rate of change with a predefinable minimum value or a predefinable value interval, a change in a movement state of the vacuum gripper can be predetermined on the basis of the status signal. With such a processing device, which is contained in a vacuum control device, an optimization of gripping and / or depositing operations for a workpiece is made possible, which is to be gripped by a vacuum gripper, which is supplied with a provided by the vacuum control device vacuum and possibly overpressure. The vacuum control device, based on the rate of change for the sensor signal already at an early stage and well before reaching the desired minimum pressure in the vacuum gripper in cooperation with a machine control an optimized motion control for a controllable by the machine control manipulator, which carries and moves the vacuum gripper achieve.

It is advantageous if the vacuum gripper is associated with a sensor device designed in particular as a pressure sensor and designed for providing the vacuum-related sensor signal to the processing device. Thus, a determination of the vacuum on site takes place directly on the vacuum gripper, whereby a high accuracy of the determined measured value for the at least one characteristic of the vacuum to be generated is ensured. It is expedient if the processing device is associated with a pressure sensor for determining a fluid pressure at the fluid port and that the processing device is designed for a change of the control signal to the vacuum control valve on the basis of the determined fluid pressure. By integrating the pressure sensor into the vacuum control device, a particularly compact construction can be achieved, since connection means for an external pressure sensor, for example, sockets for signal cables, can be dispensed with. In addition, no elaborate preparation of the output signals of the pressure sensor is required, but the output signals of the pressure sensor are forwarded to the processing device on a short path. Particularly preferably, the pressure sensor is electrically connected directly to a printed circuit board on which the processing device is formed.

In an advantageous development of the invention, provision is made for a vacuum generator, in particular an ejector, to be fluidly connected between the fluid connection and the fluid outlet. As a result, the required vacuum can be generated directly in the vacuum control device. It is particularly advantageous if an optional provision of a vacuum and an overpressure at the fluid outlet can be achieved solely by switching over the vacuum control valve. In this case, the vacuum control valve provides the compressed air provided at the fluid connection to the vacuum generator, in particular the ejector, in a first switching position, so that a vacuum is provided at the fluid outlet. In a second switching position, the fluid connection is blocked by the vacuum control valve. In a third switching position, an immediate forwarding of the compressed air provided at the fluid connection to the fluid outlet takes place, so that an overpressurization of the vacuum gripper connected there can take place.

Alternatively, it can be provided that a second fluid connection is provided on the vacuum control device, which is designed to provide a second fluid to the fluid control valve and / or the vacuum control valve and that the fluid control valve and / or the vacuum control valve for selectively releasing a communicating connection is formed between the first or the second fluid port and the fluid outlet and for blocking the connection to the fluid outlet. Such a configuration of the fluid control valve and / or the vacuum control valve is advantageous when both compressed air and vacuum are provided to the vacuum control device. Thus, the fluid control valve and / or the vacuum control valve are responsible for switching between the provided vacuum, the provided compressed air and possibly a blocking of the fluid outlet.

According to a third aspect of the invention, the object is solved by the features of claim 12. Here, a manipulator with a movable manipulator arm and a vacuum gripper attached thereto for gripping, moving and settling of workpieces is provided, wherein the vacuum gripper fluidly communicating with a vacuum control device according to the invention, as well as with a machine control, which is responsible for a control of the manipulator arm and for communication with the Vacuum control device is formed via an external communication system. Furthermore, it is provided that the machine control is set up in such a way that a change of a movement state of the

Manipulator takes place in response to a status signal of the vacuum control device. Advantageous embodiments of the invention are illustrated in the drawing. Hereby shows:

FIG. 1 shows a schematic representation of a vacuum gripping device,

Figure 2 is a modular fluid control device for

Controlling the vacuum gripping device shown in FIG. 1,

3 shows a pneumatic circuit diagram of a first embodiment of a vacuum control device, FIG.

Figure 4 is a pneumatic circuit diagram of a second embodiment of a vacuum control device and

Figure 5 is a timing diagram for the operation of a

Vacuum gripping device.

1 shows a vacuum gripping device 1 is shown schematically, as it can be used for example for maneuvering plate-shaped objects 2. The vacuum gripper 1 comprises by way of example a plurality of vacuum grippers 4 mounted on a common dimensionally stable frame 3 and flexible at least in regions. The frame 3 is presently attached to two linear actuators 5 aligned parallel to one another, which are electrical or fluidic adjusting means, in particular pneumatic cylinders can. Each of the vacuum grippers 4 is fluidly communicating with a supply line 6, which is designed for providing a fluid flow from a limited by the vacuum gripper 4 and the associated workpiece 2, not shown cavity or a fluid stream in this cavity. The vacuum grippers 4 can For example, first be placed on the surface of the workpiece 2, to then effect in a subsequent step, an evacuation of the cavity via the supply line, whereby a holding force between vacuum gripper 4 and workpiece 2 builds. With sufficient sealing effect between the vacuum gripper 4 and the workpiece 2 and sufficient negative pressure of the cavity can thereby the workpiece 2 raised by means of the linear actuator 5

and / or lowered. In an exemplary embodiment of the linear actuator 5 as a pneumatic cylinder

Pressure lines 7, 8 provided over the compressed air to the linear actuators 5 can be passed to effect the desired lifting or lowering operation.

In a subsequent step, the cavities of the respective vacuum grippers 4 are vented or possibly subjected to overpressure in order to bring about a rapid reduction of the holding forces and to be able to deposit the workpiece 2 quickly.

The supply line 6 is like the pressure lines 7 and 8 connected to a fluid control device 9, which is composed of a plurality of modules 10, 11, 12 shown in more detail in the figure 2. Preferably, these modules 10, 11, 12 arranged in juxtaposition and communicate with each other electrically and fluidly in communicating connection. By way of example, the fluid control device 9 comprises a vacuum module 10 and two compressed air modules 11 and a control module 12. The vacuum grippers 4 are connected to the vacuum module 10 via the supply line 6. The two linear actuators 5 are connected via the pressure lines 7, 8 with the compressed air modules 11 responsible for the lifting or lowering movement. The control module 12 is provided for the coordination of the functions of the other modules 10, 11, for this purpose, for example, a parallel interconnection of the modules 10, 11 with the control module 12 or an internal communication system between the modules 10, 11 and the control module 12 may be provided. In addition, the control module 12 also serves to implement control commands that are provided by a machine controller 13 via a communication system 15 to the control module 12.

From Figure 2, the modular structure of a preferred embodiment of a fluid control device 12 can be seen. The control module 12 comprises an external communication interface 16, an internal communication interface 17 and two external fluid ports 18, 19 and two internal fluid ports 20, 21. At the two external fluid ports 18, 19, for example, compressed air and vacuum can be connected, the internal Fluid connections 20, 21 then serve as examples for forwarding the compressed air and the vacuum to the modules 10, 11. The external communication - cut parts 16 is used to connect an external communication system 15, the exemplary transmission of control commands and sensor data between the machine control 13 and the control module 12 according to the Profibus protocol provides. The internal communication interface 17 is provided for forwarding control commands from the control module 12 to the modules 10, 11 and for providing sensor and / or status signals of the modules 10, 11 to the control module 12 and can, for example, for a data transmission to the I / O Link protocol be formed. Alternatively, the internal communication interface 17 on the control module 12 and corresponding communication interfaces 17 on the modules 10, 11 as a parallel bus system, as an I / O link or as parallel wiring, in particular multipole formed.

The illustrated in Figure 3 first embodiment of a designed as a vacuum control unit 22 vacuum module 10 includes a fluid port 23, a control valve 24, a Ejector 25, an exhaust air muffler 28, a suction port 29 arranged on the ejector 28, a fluid line 30, a fluid outlet 31, a processing device 32 and a sensor device designed as a pressure sensor 33. The fluid port 23 is configured to supply compressed air to the vacuum controller 22 and is disposed on a side wall of the vacuum module 10 so that it can communicate with a corresponding internal fluid port 20 of an adjacently located module 10, 11, 12. The fluid connection 23 is connected to a control valve 24, which is designed for an optional forwarding of the provided compressed air to the ejector 25 or directly to the fluid outlet 31. The control valve 24 is designed as an example as 3/3 way valve and can be controlled electromagnetically. For this purpose, arranged in the vacuum control device 22 processing device 32 is provided, which communicates via the internal communication interface 17 with the control module 12 in electrically communicating connection. The control valve 24 may be provided in a first, shown in Figure 3 switching position for a compressed air supply to the ejector 23, so that at the suction port 29 and thus at the fluid outlet 31, a negative pressure is applied, with which the vacuum gripper 4 shown in FIG Workpiece 2 can be firmly sucked. In a second switching position of the control valve 24, a pressurization of the vacuum gripper 4 is provided for a quick placement of the workpiece 2. In a third switching position of the control valve 24, the connections between the

Fluid port 23 and the fluid outlet 31 blocked. The processing device 32 is electrically connected to the pressure sensor 33, which in turn communicates fluidly with the fluid line 30 leading to the fluid outlet 31. With the help of the pressure sensor 33 can actually Fluid pressure applied to the fluid outlet 31 are determined in order to be able to carry out an advantageous activation of the control valve 24. In one embodiment, not shown, the processing device is designed as a structurally separate component of the vacuum control device or is integrated in the control module.

In the illustrated in Figure 4 second embodiment of a designed as a vacuum control unit 42 vacuum module 10, the same designations as in the vacuum control unit 22 are used for functionally identical components. The vacuum control unit 42 also includes a processing device 32, a pressure sensor 33 and a fluid outlet 31. Contrary to the vacuum control unit 22, two fluid ports 43, 44 are provided in the vacuum control unit 42, which a Druckluftbzw. Vacuum supply into the vacuum control unit 42 serve. Each of the two fluid connections 43, 44 is assigned a control valve 45, 46 which is designed as a 2/2-way valve, wherein each of the control valves 45, 46 is electrically coupled to the processing device 32. The processing device 32 can control the control valves 45, 46 in such a way that optionally the one provided at the fluid connection 43

Compressed air or provided at the fluid port 44 negative pressure to the fluid outlet 31 is provided. Ergän ^¬ Zend can be provided that both control valves 45, 46 are switched by the processing device 32 in the respective blocking position, so that no fluid flow between the fluid ports 43, 44 and the fluid outlet 31 is present.

From the timing diagram for the operation of a vacuum gripping device 1 shown in FIG. 5, it can be seen how an advantageous control of the vacuum control device 42 shown in FIG. 4 can be carried out. The time t is plotted on the abscissa axis of the graph, the pressure p is plotted on the ordinate axis.

At a time tO both control valves 45, 46 are switched to the blocking position, so that neither a vacuum nor an overpressure abut the fluid outlet 31. Accordingly, the pressure measured by the pressure sensor 33 is equal to the ambient pressure pO.

At time t 1, which is also referred to as the first activation time and can be regarded as the start of a drive cycle extending between time t 1 and t 0, a control signal is output by the processing device 32 to the control valve 46 in order to effect a vacuum application of the fluid outlet 31. The control signal is symbolized as a black bar in the line B of Figure 5, which begins at time tl. Due to electrical and / or mechanical and / or fluidic inertia occurs a time delay between the output of the control signal by the processing means 32 and an actual change in the pressure at the fluid outlet, so that the effective time, for example, a specifiable pressure change Δρΐ has actually occurred , present in the present case at time t2. This time difference t2-tl is determined by the processing device 32 by evaluating the electrical sensor signal of the pressure sensor 33 and stored as a delay time tdl.

From the time t2 to the time t3, at which the vacuum gripper 4 is placed on the plate-shaped workpiece, an idle pressure value can be determined, in particular by means of a pressure sensor 14 arranged on the vacuum gripper 4. The idle pressure value sets as soon as the control valve 46 has been switched to the passage position and the fluidic inertia between the control valve 46 and vacuum gripper 4 are overcome and before the vacuum gripper 4 comes to rest on the plate-shaped workpiece 2, in particular from the time t2. The idle pressure value provides information as to whether the control valve 46 and / or the supply lines 6 and / or the vacuum gripper 4 arranged between the control valve 46 and the vacuum gripper 4 are possibly defective or blocked as such. The idle pressure value is compared to an idle pressure limit stored in the processing device 32. A continuation of the gripping operation is only provided if the idling pressure value falls below the idling pressure limit value, that is, a pressure reduction in the vacuum gripper has taken place below the idling pressure limit value. Otherwise, the

Gripping process by the processing device 32 and the machine controller coupled thereto 13 aborted and optionally output an error signal. Alternatively it can be provided that only an error signal is output in order to leave the user the decision as to whether the gripping operation should be continued or not.

At a time t3, the vacuum gripper 4 comes into contact with the workpiece 2, so that a rapid build-up of a vacuum in the space defined by the vacuum gripper 4 and the workpiece 2 and thus also a build-up of a holding force between vacuum gripper 4 and workpiece 2.

From the time t3, the processing device 32 continuously determines the change in the pressure that has occurred, ie the time derivative of the pressure or rate of pressure change. By way of example, it is possible to provide, after the lapse of a period of time within which the rate of pressure change has reliably exceeded a specifiable level, a status signal which is shown by way of example in line D of FIG. 5 is outputted by the processing device 32. This is the case by way of example at time t4. In addition, it can be checked whether, at a predeterminable time or after the passage of a predeterminable time interval, exemplarily the time interval between t3 and t4, a prescribable pressure level has been reached in addition to the observance or exceeding of a predefinable limit value for the rate of pressure change, in order thereby to predict a successful Confirm the course of the gripping process. For this purpose, a corresponding limit value can be stored in the processing device 32. If the pressure change rate and optionally the desired pressure level correspond to a default value, the processing device 32 can output the status signal.

The status signal can, for example, be forwarded via the internal communication system to the control module 12 and from there via the external communication system 15 to the machine controller 13. Based on this status signal can be triggered in the machine control 13, for example, the control of the linear divider 5. Between the output of a corresponding drive signal by the machine controller 13 and an actual movement of the linear actuator 5 is also a time difference in which a further pressure drop has taken place on the vacuum gripper, thereby increasing the holding forces. Due to the intended consideration of the rate of pressure change and optionally a pressure level required after a predeterminable period of time, it is possible to output the status signal at a point in time when sufficient holding forces are still not present between the vacuum grippers 4 and the workpiece 2, since this leads to an actual acceleration of the workpiece 2 the holding forces have reached a sufficient level.

In contrast, reaching a predefinable pressure level as a trigger for a similar status signal requires a longer waiting time, since in contrast to the rate of pressure change can only be made at a much later date a reliable statement about whether the workpiece 2 is held securely by the vacuum grippers 4. The point in time at which a pressure-based status signal could be output is denoted by t5 in FIG. Obviously, the analysis of the speed of pressure change provides a time advantage for the lifting of the workpiece 2, so that a corresponding vacuum gripping device 1 can be operated more efficiently.

For a diagnosis of the vacuum gripping device 1 may further be provided to determine the minimum pressure value to detect any damage to the vacuum gripper 4 or other disturbances on the vacuum gripper 1. Preferably, the minimum pressure value is determined as soon as the rate of pressure change has fallen below a predeterminable value during the build-up process for the vacuum, that is to say during the lowering of the pressure in the vacuum gripper 4, in particular vanishing. By way of example, the minimum pressure value in the gripping process shown in FIG. 5 reaches a minimum pressure limit shortly before t6. The minimum pressure limit is stored as an example in the processing device. If the minimum pressure value is above the minimum pressure limit value, the faultless operation of the vacuum gripper device 1 is assumed. If the minimum pressure value does not fall below the minimum pressure limit value, a malfunction of the vacuum gripper device 1 must be assumed. By way of example, it can be provided that the vacuum gripping device 1 after that gripping cycle, in which for the first time no undershooting of the minimum pressure limit value can be detected by the minimum pressure value, an error signal is output and no further gripping operation starts.

Additionally or alternatively, it can be provided to use the delay time tdl determined at the beginning of the negative pressure application of the fluid outlet for a safe and rapid depositing of the workpiece 2. When placing the workpiece 2, the problem is that a movement of the vacuum gripper 4 should take place only when the workpiece 2 is stored reliably. To ensure this, it is known from the prior art, after aeration or pressurization of the vacuum gripper 4 to provide a waiting time within which no movement of the vacuum gripper 4 takes place. This waiting time must be selected to take into account all the electrical, mechanical and fluidic inertias that may occur between the processing device 32, the control valve 45, 46, the fluid outlet 31 and the vacuum grippers 4. In order to shorten this waiting time, the delay time tdl, which occurs when vacuum is applied to the vacuum gripper 4, is taken into account by the processing device 32 during ventilation or pressurization of the vacuum gripper 4, which takes place, for example, at a time t6 by the processing device 32 in synchronism with a deactivation of the vacuum was determined by the processing device 32. With this delay time, which is visible in FIG. 5 as the time difference between the time t6 and the beginning of the pressure rise in the vacuum grippers at the time t7, the processing device 32 has information available on the basis of which the time t8, at which a substantial, In particular, complete, degradation of the vacuum on the vacuum grippers 4 is done, more precisely can be determined. Thus, the time from the aeration or pressurization of the vacuum gripper 4 to a relative movement between the vacuum grippers 4 and the workpiece 2 can be shortened.

Additionally or alternatively, the processing device 32 can also monitor the pressure signal of the pressure sensor 33 in order to provide a status signal to the machine controller 13 when a predeterminable minimum pressure, in particular the ambient pressure, is reached, by means of which a movement of the linear divider 5 can be initiated. Advantageously, during the ventilation or pressurization of the vacuum gripper 4, a delay time td2 can be determined, which is the time difference between the switching time t6 for the control valve 45, in this case for pressurizing the vacuum gripper 4, and reaching a predefinable minimum pressure, for example at the time t8 , 4 results on the vacuum grippers. This delay time td2 can also be taken into account by the processing device 32 in order to output the status signal to the machine control 13 at the earliest possible time, without the risk of the vacuum grippers 4 being lifted off the workpiece 2 at a time, to which still a significant holding force is present.

Claims

claims

A method of operating a vacuum gripper (1) comprising a vacuum gripper (4), a processing device

(32), a sensor device (33) for providing a fluid and / or vacuum-related sensor signal and a controllable by the processing device (32) fluid control valve

(24, 45, 46) for providing a vacuum to the vacuum gripper (4), wherein the processing means (32) is adapted to process the sensor signal and to drive the fluid control valve (24, 45, 46), comprising the steps of: outputting a Control signal from the processing means (32) to the fluid control valve (24; 45,46) at a drive timing (tl; t6), determining a rate of change for the sensor device (33) correlated to a fluid and / or vacuum related physical value Sensor signal and providing a status signal to an external communication system

(15) which is designed for communication with a machine controller (13) in order to effect a change of a movement state of the vacuum gripper (4) by the status signal if the determined rate of change corresponds to a predefinable minimum value or lies within a predefinable value interval.

2. The method according to claim 1, characterized in that of the processing device (32) an idle pressure value is determined at a time at which the vacuum gripper (4) is not applied to a workpiece (2).

3. The method according to claim 1 or 2, characterized in that the processing device (32) during a vacuum gripping process, a minimum-pressure value is determined, which is established when the vacuum gripper (4) on the workpiece (2).

4. The method according to claim 2 or 3, characterized in that the minimum value or the value interval for the rate of change of the sensor signal in dependence on the idle pressure value and / or the minimum pressure value is adjusted.

5. The method of claim 2, 3 or 4, characterized in that an output of a warning message from the processing device (32) takes place when the idle pressure value above a predetermined idle limit and / or the minimum pressure value above a predetermined minimum - Pressure limit lie.

6. The method according to any one of the preceding claims, characterized in that the status signal is provided by the processing means (32) only if the rate of change for the sensor signal longer than a predeterminable minimum time interval with the predetermined minimum value or the predetermined value interval coincides and / or if a minimum value for the sensor signal has been reached within a predefinable period of time from the output of the control signal from the processing device (32) to the fluid control valve (24; 45, 46) at the activation time (t1; t6).

7. A vacuum control device having a fluid connection (18, 19, 23, 43, 44) for a fluid supply, having a fluid outlet (31) for providing a fluid and / or a vacuum to a consumer, having a processing device (32) which is used for Processing with at least one fluid and / or vacuum-related sensor signal and for providing control signals, as well as with a controllable by the control signals fluid control valve (24, 45, 46) with the fluid port (18, 19, 23, 43, 44) or is connected to the fluid port (18, 19; 23; 43, 44) and the fluid outlet (31), and / or to a vacuum control valve (46) connected to the fluid port (44) and the fluid outlet (31) a temporary supply of fluid

and / or vacuum at the fluid outlet (31), characterized in that the processing means (32) is adapted to determine a rate of change of the sensor device (14; 33) correlated to a fluid and / or vacuum related physical value Sensor signal and for providing a status signal to an external communication system (15), which is used for communication with a machine controller (13) is formed, that in accordance with the determined rate of change with a predetermined minimum value or a predetermined value interval based on the status signal, a change a movement state of the vacuum gripper (4) can be predetermined.

8. A vacuum control device according to claim 7, characterized in that the vacuum gripper (4), in particular designed as a pressure sensor, sensor device (14) is associated, which is designed for providing the vacuum-related sensor signal to the processing device (32).

9. A vacuum control device according to claim 7 or 8, characterized in that the processing means (32) is associated with a pressure sensor (33) for detecting a fluid pressure at the fluid port (31) and that the processing means (32) for a change of the control signal to the fluid control valve (24, 45) and / or the vacuum control valve (46) is formed on the basis of the determined fluid pressure.

10. A vacuum control device according to claim 7, 8 or 9, characterized in that between the fluid connection (23) and the fluid outlet (31) a vacuum generator (25), in particular an ejector, is fluidly looped.

11. A vacuum control device according to one of claims 7 to 10, characterized in that a second fluid connection (43) is provided, which is designed for providing a second fluid to the fluid control valve (45) and / or the vacuum control valve (46) and that Fluid control valve (45) and / or the vacuum control valve (46) for an optional release of a communicating connection between the first or the second fluid port (43, 44) and the fluid outlet (31) and for blocking the connection to the fluid outlet (31) are formed ,

12. Manipulator with a movable manipulator arm (3, 5) and a vacuum gripper (4) attached thereto for gripping, moving and depositing workpieces (2), the vacuum gripper (4) communicating fluidically with a vacuum control device (22; of claims 7 to 11 is connected, and with a machine controller (13) for driving the manipulator (3, 5) and for a Kom ^¬ munication with the vacuum control means; is formed over an external communication system (15) (22 42) , characterized in that the machine control (13) is in such a way is directed that a change of a movement state of the manipulator arm (3, 5) in response to a status signal of the vacuum control device (22; 42) takes place.