Method for operating a pneumatic system and pneumatic system for industrial automation

Abstract

In a method for operating a pneumatic system (11) for industrial automation, which has at least one pneumatic actuator (14) and a control device (13) for controlling a movement of an actuator member (27) of the at least one pneumatic actuator (14) over a travel stroke from an end position (30) into a second end position (31) and / or from the second end position (31) into the first end position (30), the method comprises the following steps: - continuously measuring a position of the actuator member (27) by means of a position-measuring device (37) which comprises a first position-measuring unit (38a) associated with a first partial stroke (h1) of the travel stroke (H) of the actuator member (27) and a second position-measuring unit (38b) associated with a second partial stroke (h2) of the travel stroke (H), wherein, depending on the position of the actuator member (27), a measurement is taken either with the first or the second position-measuring unit (38a, 38b) and no measurement is taken between the partial strokes (h1, h2), - providing the measured position as an actual position signal to the control device (13), - controlling the position on the basis of the actual position signal detected by the position-measuring device (37).

Description

[0001] Method for operating a pneumatic system and pneumatic system for industrial automation

[0002] The invention relates to a method for operating a pneumatic system for industrial automation and a pneumatic system for industrial automation.

[0003] Methods for operating a pneumatic system for industrial automation, as well as pneumatic systems for industrial automation, are used in many areas.

[0004] One example of an application area is wafer manufacturing, where a variety of pneumatic actuators are typically used to move different types of control elements, such as spool valves, which open or close a gate to a processing chamber for wafer processing. Overall, wafer manufacturing places high demands on the operation of pneumatic systems, including minimizing vibrations during the operation of the spool valves. Furthermore, the sensors used to operate the pneumatic system must be simple and reliable.

[0005] However, such pneumatic systems are not only suitable for wafer production but also for industrial automation in general. Depending on the application, different requirements arise for the pneumatic system.

[0006] The purpose of the invention is to provide a method for operating a pneumatic system and a pneumatic system that is improved compared to conventional methods or systems, in order to meet the requirements of semiconductor, especially wafer, production.

[0007] The foregoing problem is solved by a method for operating a pneumatic system for industrial automation with the features of independent claim 1 and by a pneumatic system for industrial automation with the features of independent claim 9. Further developments of the invention are presented in the dependent claims.

[0008] The method for operating a pneumatic system for industrial automation includes at least one pneumatic actuator and a control device for controlling a movement of an actuator element of the at least one pneumatic actuator over a travel stroke from a first end position to a second end position and / or from the second end position to the first end position, wherein the method comprises the following steps:

[0009] - Measuring the position of the actuator element using a position measuring device comprising a first position measuring unit assigned to a first partial stroke of the actuator element's travel stroke and a second position measuring unit assigned to a second partial stroke of the travel stroke, wherein, depending on the position of the actuator element, either the first or the second position measuring unit is used for measurement and no position measurement takes place between the partial strokes, providing the measured position as actual position signals to the control device.

[0010] - Implementation of position control based on the position signal recorded by the position measuring device.

[0011] The pneumatic system according to the invention, in particular for carrying out the method with the features of claim 1, comprises at least one pneumatic actuator, with an actuator element, a control device for controlling a movement of the actuator element over a travel stroke from a first end position to a second end position and / or from the second end position to the first end position, and with a position measuring device comprising a first position measuring unit assigned to a first partial stroke of the travel stroke of the actuator element and a second position measuring unit assigned to a second partial stroke of the travel stroke, wherein, depending on the position of the actuator element, a position measurement can be carried out with either the first or the second position measuring unit, and a measurement-free stroke section lies between the partial strokes with respect to a position measurement.

[0012] A key aspect of the invention is that position measurement using the position measuring units of the positioning device is not continuous over the entire travel stroke of the actuator, but discontinuous at selected points along the travel stroke, specifically within certain partial strokes. Between these partial strokes, there is therefore a stroke section free of position measurement. Compared to conventional pneumatic systems, which primarily measure continuously over the entire travel stroke and thus require a measuring arrangement that covers the entire travel stroke (for example, a scale extending over the entire travel stroke, perhaps optically scanned), the position measuring units according to the invention are simpler, for example, shorter, and therefore more cost-effective.

[0013] In a further development of the invention, the position measuring units are each designed as continuous position measuring units for continuous position measurement across the respective assigned partial strokes. The position measuring units are therefore not designed as position switches that can only detect a discrete position, such as the end position, but rather position measurement can be performed continuously across the partial strokes.

[0014] Particularly preferred is the following procedure for moving the actuator from the first end position to the second end position: first, the position of the actuator is continuously measured over the first partial stroke using the first position measuring unit; then, no position measurement is performed over a certain stroke distance; and finally, the position of the actuator is continuously measured over the second partial stroke using the second position measuring unit. During the return movement of the actuator from the second end position to the first end position, the position measurements can be performed in reverse order.

[0015] The position measuring units can, for example, be designed as continuous position measuring sensors.

[0016] In a particularly preferred embodiment, the first position measuring unit has a first outer housing, while the second position measuring unit has a second outer housing formed separately from the first. Advantageously, the position measuring units are thus components of the position measuring device formed separately from one another. In a further development of the invention, a pressure measuring unit, in particular in the form of a pressure sensor, is provided, via which the actual pressure in at least one pressure chamber of the pneumatic actuator can be measured and transmitted to the control device in the form of an actual pressure signal.

[0017] It is possible for the control system to be given target position values ​​of the actuator within the partial strokes, or for the control system to calculate target position values ​​from reference values. The target position values ​​can be, for example, in the form of a trajectory or path curve. The target positions of the actuator can then be compared with the actual positions measured by the position measuring units within the partial strokes. It is possible to subordinate a pressure control to the position control within the partial strokes, which is expediently active over the entire travel stroke. Alternatively, however, position control without subordinate pressure control would also be possible; for example, pressure values ​​could be estimated.

[0018] In a particularly preferred manner, position control is therefore carried out in the partial strokes, while between the partial strokes, where no position measurement takes place, the system switches from position control to position monitoring.

[0019] In a further development of the invention, the first and / or the second partial stroke are assigned to one of the end positions of the actuator element. For example, it is possible that the first partial stroke is assigned to the first end position and the second partial stroke to the second end position of the actuator element. In this case, the position measuring units can measure the position in the area of ​​the end positions. Alternatively, it is also conceivable that the partial strokes in which measurements are taken do not correspond to the end positions, or, as a more obvious alternative, that one of the partial strokes is assigned to one of the end positions, while the other partial stroke is not assigned to either end position, for example, lying approximately in the middle of the travel stroke.

[0020] In a further development of the invention, the pneumatic system has a slide valve, wherein the slide valve has a valve element that is connected to the actuator element of the pneumatic actuator and is moved along with the movement of the actuator element, and wherein the slide valve has an opening for the passage of a wafer, which can be opened or closed by the valve element.

[0021] In a particularly preferred manner, the pneumatic actuator is a single- or double-acting pneumatic cylinder.

[0022] A preferred embodiment of the invention is shown in the drawing and is explained in more detail below. The drawing shows:

[0023] Figure 1 shows a schematic representation of a preferred embodiment of the pneumatic system according to the invention with which the method according to the invention can be carried out.

[0024] Figure 2 shows a block diagram of the inventive method for operating a pneumatic system for industrial automation,

[0025] Figure 3 shows a schematic representation of a wafer processing plant which has several pneumatic systems according to Figure 1, and Figure 4 shows a schematic representation of part of the pneumatic system of Figure 1, wherein an embodiment of a slide valve is shown which is in a deactivated position (left) and in an activated position (right).

[0026] Figure 1 shows a preferred embodiment of the inventive pneumatic system 11, which is shown and described here as an example for use in a wafer processing machine 12. Of course, it is also possible to use the pneumatic system 11 in other areas of industrial automation. Its use in a wafer processing machine 12 is therefore purely exemplary.

[0027] As shown in particular in Figure 1, the pneumatic system has a control device 13 to which at least one pneumatic actuator 14 is assigned.

[0028] As shown in particular in Figure 3, the pneumatic system 11 can be used in a wafer processing machine 12. In this case, several pneumatic actuators 14 are assigned to the control unit 13.

[0029] The construction of such a wafer processing plant 12 is shown in Figure 3 in a purely schematic and exemplary manner.

[0030] The wafer processing plant 12 has a distribution room 15 and several processing rooms 16 grouped around the distribution room, in each of which different processing processes take place on the wafers to be processed there.

[0031] In the distribution room 15, which is shown in top view in Figure 3 and has a horizontal plane formed by the x-axis direction 17 and the y-axis direction 18 of a Cartesian coordinate system spanned by three coordinates x, y, z, there is usually a handling unit, for example in the form of a robot, which places wafers to be processed into the adjacent associated processing rooms 16 and ejects processed wafers from the processing rooms 16 after processing.

[0032] Between the distribution room 15 and the adjacent processing rooms 16 there are passageways, each of which is assigned a slide valve 20, as shown, for example, in Figures 1 and 4.

[0033] As shown particularly in Figure 1, the machining chamber 16 has an exemplary rectangular shape and extends in a vertical direction, which can also be referred to as the z-axis direction 19, in a transverse direction perpendicular to the vertical direction, which can also be referred to as the x-axis direction 17, and in a horizontal direction, which can also be referred to as the y-axis direction 18. The machining chamber 16 has a machining chamber opening 21, which can be closed by means of the slide valve 20 in order to seal the machining chamber 16 from the environment. The pressure in the machining chamber 16 is typically below atmospheric pressure.

[0034] As further shown in Figure 1, the slide valve 20 has a valve housing 22 in which at least one opening 23 is formed for the passage of the wafer. Optionally, the valve housing 22 can also be integrally connected to the housing of the machining chamber 16, so that the machining chamber opening 21 corresponds to the opening 23. In the example shown, however, the valve housing 22 is an add-on component, and the opening 23 of the valve housing 22 of the slide valve 20 aligns with the machining chamber opening 21.

[0035] If necessary, the valve housing 22 may have a further opening 24, in particular assigned to the distribution chamber 15, which opens with the first opening 23.

[0036] An essential element of the slide valve 20 is a pneumatic actuator 25, which could therefore also be referred to as a valve drive.

[0037] The pneumatic actuator 25 is shown in the figures, in particular in figures 1 and 4, by way of example in the form of a double-acting pneumatic cylinder.

[0038] In the example shown, the pneumatic actuator 25 has a cylinder housing 26 in which an actuator element 27 in the form of a piston is movably guided.

[0039] The actuator element 27 divides the interior 28 of the cylinder housing into two pressure chambers 29a, 29b, which can alternatively also be referred to as working chambers. Pressure fluid in the form of compressed air can be selectively supplied to or discharged from the pressure chambers 29a, 29b in order to move the actuator element 27 from a first end position 30 to a second end position 31 and vice versa, from the second end position 31 to the first end position 30. The actuator element 27, in the form of a piston, is connected to a piston rod 32 extending from the cylinder housing 26, at the free end of which a valve element 33, in the form of a slide valve, is attached.

[0040] The valve element 33, i.e., in the example shown, the slide element, is assigned to the first opening 23, which can be selectively opened or closed by the valve element, the opening and closing movement being effected by the movement of the actuator element as a result of the pressurization of one or the other pressure chamber 29a, 29b.

[0041] To ensure the tightest possible closure of the first opening 23, the valve element 33 has a circumferential, in particular rubber-elastic, sealing element 34 on its side facing the opening 23.

[0042] As shown in particular by the overview in Figure 4, the slide valve 20 can be operated between a deactivated state, in which the valve element 33 is in a ready position 35, in which the opening 23 is open, and an active state, in which the valve element 33 is in a closed position 36, in which the opening 23 is fluid-tightly closed.

[0043] The pneumatic system 11 also has a position measuring device 37 for measuring the position of the actuator element 27 during its movement, i.e., for example, the position of the piston in the cylinder housing.

[0044] As already mentioned, the actuator 27 is movable between the first and second end positions 30, 31, thus covering a travel stroke H. The special feature here is that the position of the actuator 27 is not measured continuously over the entire travel stroke, but only over two partial strokes hi, h2. For this purpose, the position measuring device 37 has a first position measuring unit 38a, which measures the position of the actuator 27 within the first partial stroke hi, and a second position measuring unit 38b, which measures the position of the actuator 27 within the second partial stroke h2. The position measuring units 38a, 38b are each expediently designed as position sensors and are capable of transmitting Ist position signals to the control device 13.

[0045] In the example shown, the partial strokes hi, h2, within which a position measurement takes place, are located in the region of the end positions 30, 31 of the actuator element 27. Accordingly, the position measuring units 38a, 38b are arranged in the region of the end positions 30, 31 of the actuator element 27, for example, attached there to the outer wall of the cylinder housing 26. It should be noted again that the partial strokes hi, h12, within which a position measurement takes place, are not necessarily located in the region of the end positions 30, 31; it is also quite possible that one of the partial strokes is located in the region of the end positions 30, 31 and another partial stroke is located, for example, in the middle region of the travel stroke.

[0046] The determination of the partial strokes hi, I12, within which measurements are taken, depends significantly on the type and design of the slide valve 20. The operating principle of the slide valve 20 shown here as an example is based on a purely linear movement of the valve element 33 between the ready position 35 and the closed position 36, which means that the slide valve 20 can also be referred to as an "I-motion slide valve" in this case.

[0047] Alternatively, in embodiments not shown, the slide valve can also be configured such that the valve element 33 performs both a vertical and a horizontal movement between the ready position and the closed position. In these types of slide valves, the partial strokes can also be arranged differently from the end positions 30, 31. The pneumatic system 11 further comprises a pressure measuring device 39 for measuring an actual pressure in at least one pressure chamber 29a, 29b of the pneumatic actuator and transmitting the actual pressure in the form of an actual pressure signal to the control device 13. In the example shown, the pressure measuring device 39 comprises two pressure measuring units 40a, 40b, which are preferably designed as pressure sensors.

[0048] It is possible that the pressure sensors are each assigned to pressure chambers 29a and 29b, for example, installed in the respective pressure chambers 29a and 29b. However, it is preferred that the pressure measuring device 37 is on board a control valve assembly (not shown), which in turn comprises several control valves for the fluidic control of the associated pneumatic actuators 25.

[0049] Advantageously, the control valves are each designed as proportional valves that exhibit the required control accuracy. Piezoelectric valves, in particular, are especially suitable as proportional valves. Typically, at least one piezoelectric element is used as the valve element.

[0050] Particularly preferably, the control valve assembly is designed as a valve manifold or valve battery, with a one-piece or multi-piece base plate that acts as a fluid distributor and has on its upper side a plurality of mounting positions for control valves, in particular disc-shaped ones, or other functional units, for example safety modules, silencers or the like.

[0051] The control valve assembly, in particular in the form of a valve manifold or valve bank, can include a part of the control device 13 in the form of a pressure regulator 13b. The pressure regulator 13b can, for example, have several pressure sensors arranged in associated channels, for example on a printed circuit board.

[0052] One of the main tasks of the control device 13, whose control scheme is shown by way of example in Figure 2, is to prevent a hard stop when the valve element moves into the closed position 36. This prevents vibrations from occurring during movement into the closed position, which could adversely affect wafer production, for example by causing particles to be stirred up and land on the wafer surface. The control device 13 can comprise a position control device 13a and a pressure control device 13b.

[0053] The control valve assembly, in particular a valve manifold or valve bank, can have a common controller for the position control device and the pressure control device. However, the controller can also be separate from the control valve assembly and connected to it via a signal interface.

[0054] The communication system underlying the signal connection may preferably be a communication system from the group OPC UA (Open Platform Communication Unified Architecture), OPC UA over TSN (Time-sensitive Networking), bus communication system, 10 Link, whereby a power supply can also be enabled via the signal connection.

[0055] The procedure for operating the pneumatic system 11 could proceed as follows: Initially, the pneumatic actuator 14, i.e., the double-acting pneumatic cylinder, is in its deactivated state. The valve element 33 is in the ready position 35, meaning that the opening 23 into the machining chamber 16 is open. The actuator element 27, i.e., the piston, is in its first end position 30, which in the example shown is the lower end position 30.

[0056] After loading the processing chamber 16, it is necessary to seal the opening 23 with the valve element in a fluid-tight manner.

[0057] Advantageously, a trajectory or path curve is specified for the control device 13, or a trajectory is calculated in the control device 13 on the basis of position reference values ​​(xref, Fig.2) which specifies how the actuator element 27 should move between the first end position 30 and the second end position 31.

[0058] The specified target positions of the actuator element 27 are converted into pressure signals and accordingly the two pressure chambers 29a, 29b are pressurized with compressed air, whereby of course for the movement from the first end position 30 to the second end position a higher pressure must prevail in the first pressure chamber 29 than in the second chamber 29b.

[0059] After the actuator 27 starts moving, actual position values ​​are continuously measured in the area of ​​the first partial stroke hi by means of the first position measuring unit 38a, which are transmitted to the control unit 13 in the form of actual position signals. Simultaneously, a subordinate pressure control takes place, i.e., the actual pressures in the pressure chambers 29a, 29b are measured and also transmitted to the control unit 13 in the form of actual pressure signals.

[0060] If the actual position deviates from the target position, adjustments are made to minimize the deviation. This means that the pressure in pressure chambers 29a and 29b is changed. Simultaneously, the subordinate pressure control system also determines the deviation of the actual pressure from the target pressure and compensates accordingly.

[0061] In the example shown, the comparison of the actual position with the target position is initially only carried out within the first partial stroke hi, i.e. in the area of ​​the first end position, whereby measurements are taken continuously and the actual-target comparisons are carried out within very small time intervals.

[0062] The position control within the first partial stroke hi ensures that the actuator 27 moves out of the first end position 30 and moves towards the second end position 31 based on the predefined trajectory. It is advantageous to move the actuator 27 relatively quickly towards the second end position 31, while braking in good time before reaching the second end position to prevent hard stops.

[0063] A characteristic feature of the described regulation is that no position control takes place between the two partial strokes hi, h2; that is, after leaving the first partial stroke hi f, no position control takes place initially, however, position control is carried out with the still active pressure control.

[0064] When the actuator 27, or rather the piston, reaches the second partial stroke h2 in the region of the second end position 31, the actual position is again continuously measured using the second position measuring unit 38b. Within the second partial stroke h2f, position control with subordinate pressure control then takes place. As mentioned, when the actuator 27 moves into the second end position 31, it is necessary to reduce the speed so that a hard stop of the valve 33 in the closed position 36 is avoided.

[0065] During the return movement of the actuator element 27 from the second end position 31 to the first end position 30, the position and pressure control can take place in reverse order; that is, first the second partial stroke I12 is traversed, then the distance during which no position control takes place, and then the movement into the first partial stroke hi in the region of the first end position 30 occurs. Here, too, control can be implemented such that the movement into the first end position 30 occurs at a lower speed in order to prevent a hard stop even in the first end position 30, i.e., when the valve element 33 moves into the ready position 35.

[0066] Alternative variants of pneumatic systems, not shown here, could be designed as follows.

[0067] It is possible for the valve element to perform a combined vertical and horizontal stroke. This can be achieved, for example, by a motion control system designated as L-Motion, in which the vertical stroke is first performed, for example, with the double-acting pneumatic cylinder shown in Figure 1, and then the horizontal stroke is performed with another pneumatic actuator, for example, also in the form of a double-acting pneumatic cylinder. Advantageously, the second pneumatic actuator is mounted on the piston rod of the first pneumatic actuator and is thus moved along with the piston rod. The valve element is advantageously attached to the piston rod of the second pneumatic actuator and is pressed horizontally against the opening by the extension of the piston rod.

[0068] Another alternative is a motion guide system called J-Motion. This alternative pneumatic system again uses two pneumatic actuators, with the second pneumatic actuator advantageously positioned stationary next to the first pneumatic actuator, which is itself pivotally mounted about a pivot axis. The pivoting movement of the first pneumatic actuator is effected by the extension of the piston rod of the second pneumatic actuator.

[0069] Finally, another alternative is a motion guide system known as Cam-Motion. This variant uses only a single pneumatic actuator, which is positively guided by a cam guide. This can be achieved, for example, by first performing the vertical stroke and then triggering the horizontal stroke via the cam guide, pivoting the pneumatic actuator, along with the valve element, towards the opening and closing it.

[0070] In all three variants not shown, it is possible to perform partial stroke measurements according to the inventive procedure using suitable displacement measuring sensors; in the L- and J-Motion systems, this is even possible for both pneumatic actuators.

Claims

Claims 1. Method for operating a pneumatic system (11) for industrial automation, comprising at least one pneumatic actuator (14) and a control device (13) for controlling a movement of an actuator element (27) of the at least one pneumatic actuator (14) over a travel stroke from a first end position (30) to a second end position (31) and / or from the second end position (31) to the first end position (30), comprising the steps: - Measuring the position of the actuator element (27) by means of a position measuring device (37) comprising a first position measuring unit (38a) assigned to a first partial stroke (hi) of the travel stroke (H) of the actuator element (27) and a second position measuring unit (38b) assigned to a second partial stroke (I12) of the travel stroke (H), wherein, depending on the position of the actuator element (27), either the first or the second position measuring unit (38a, 38b) is used and no position measurement takes place between the partial strokes (hi, I12), - Providing the measured position as an actual position signal to the control device (13) , - Implementation of position control based on the actual position signal recorded by the position measuring device (37).

2. Method according to claim 1, characterized in that during the movement of the actuator element (27) from the first end position (30) into the second end position (31) the position of the actuator element (27) is first continuously measured over the first partial stroke (hi) with the first position measuring unit (38a), then no measurement is taken over a certain stroke distance and then the position of the actuator element (27) is continuously measured over the second partial stroke (I12) with the second position measuring unit (38b), whereby during the return movement of the actuator element (27) from the second end position (31) to the first end position (30) the position measurements are carried out in reverse order.

3. Method according to claim 1 or 2, characterized in that the actual pressure in a pressure chamber (29a, 29b) of the actuator element (27) is measured and the actual pressure is provided as an actual pressure signal to the control device (13).

4. Method according to one of the preceding claims, characterized in that the first and / or the second partial stroke (hi, I12) are assigned to one of the end positions (30, 31) of the actuator element (27).

5. Method according to one of the preceding claims, characterized in that position control is carried out in the partial strokes (hi, I12) and between the partial strokes, where no position measurement takes place, the position control is switched to position control.

6. Method according to one of the preceding claims, characterized in that one of the partial strokes (hi, I12) is assigned to one of the end positions (30, 31) and the other partial stroke (hi, I12) is not located at one of the end positions, for example, is located in the middle between the end positions (30, 31).

7. Method according to one of the preceding claims, characterized in that the pneumatic system (11) has a slide valve (20), wherein the slide valve (20) has a valve element (33) which is connected to the actuator element (27) of the pneumatic actuator (14) and is moved along with the movement of the actuator element (27), and wherein the slide valve (20) has an opening (23) for the passage of a wafer, which can be opened or closed by the valve element (33).

8. Method according to one of the preceding claims, characterized in that the pneumatic actuator (25) is a single- or double-acting pneumatic cylinder.

9. Pneumatic system for industrial automation, comprising: at least one pneumatic actuator (14) with an actuator element (27), a control device (13) for controlling a movement of the actuator element (27) over a travel stroke (H) from a first end position (30) to a second end position (31) and / or from the second end position (31) to the first end position (30), and with a position measuring device (37) comprising a first position measuring unit (38a) assigned to a first partial stroke (hi) of the travel stroke (H) of the actuator element (27) and a second position measuring unit (38b) assigned to a second partial stroke (I12) of the travel stroke (H), wherein, depending on the position of the actuator element (27), a position measurement can be carried out either with the first or the second position measuring unit (38a, 38b) and between the Partial strokes (hi, I12) a stroke length that is free of measurement with respect to a position measurement lies .

10. Pneumatic system according to claim 9, characterized in that the position measuring units (38a, 38b) each designed as continuous position measuring units (38a, 38b) for continuous position measurement over the respective assigned partial strokes (hi, I12) .

11. Pneumatic system according to claim 10, characterized in that the position measuring units (38a, 38b) are each designed as continuous position measuring sensors.

12. Pneumatic system according to one of claims 9 to 11, characterized in that the first position measuring unit (38a) has a first outer housing and the second position measuring unit (38b) has a second outer housing formed separately from the first outer housing.

13. Pneumatic system, characterized by a pressure measuring device (39) , for measuring an actual pressure in at least one pressure chamber (29a, 29b) of the pneumatic actuator (25) and transmitting the actual pressure in the form of an actual pressure signal to the control device (13) .

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