DE102024111816A1 - Method for operating a pneumatic system and pneumatic system for industrial automation - Google Patents

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 element (27) of the at least one pneumatic actuator 14 over a travel stroke from one end position (30) to a second end position (31) and/or from the second end position (31) to the first end position (30), the method comprises the following steps:
- continuous measurement of 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 ( _h1 ) of the travel stroke (H) of the actuator element (27) and a second position measuring unit (38b) assigned to a second partial stroke ( _h2 ) 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 measurement is taken between the partial strokes ( _h1 , _h2 ).
- 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).

Description

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

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

One example of an application area is wafer manufacturing, where a large number of pneumatic actuators are typically used to move various types of control elements, such as spool valves that 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.

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.

The object 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 in particular for semiconductor, especially wafer, production.

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 described in the dependent claims.

• - Messen einer Position des Aktorglieds mittels einer Positionsmesseinrichtung, die eine einem ersten Teilhub des Verfahrhubs des Aktorglieds zugeordnete ersten Positionsmesseinheit und eine einem zweiten Teilhub des Verfahrhubs zugeordnete zweite Positionsmesseinheit umfasst, wobei je nach Position des Aktorglieds entweder mit der ersten oder der zweiten Positionsmesseinheit gemessen und zwischen den Teilhüben keine Positionsmessung stattfindet,
• - Bereitstellen der gemessenen Position als Ist-Positionssignale an die Regelungseinrichtung,
• - Durchführung einer Positionsregelung auf Basis des mit der Positionsmesseinrichtung erfassen Ist-Positionssignals.

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:

• - Measuring the position of the actuator element by means of 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,
• - Implementation of position control based on the actual position signal recorded by the position measuring device.

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, which comprises 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.

A key aspect of the invention is that the position measurement by means of the position measuring units of the position measuring device is not performed continuously over the entire travel stroke of the actuator element, but discontinuously at selected points along the travel stroke, specifically within certain partial strokes. Between the partial strokes, there is therefore a stroke section free of position measurement. Compared to conventional pneumatic systems, in which measurement is performed continuously over the entire travel stroke and thus requires a measuring arrangement that covers the entire travel stroke (for example, a scale extending over the entire travel stroke, which can be optically scanned), the position measuring units according to the invention are simpler, for example, shorter, and therefore more cost-effective.

In a further development of the invention, the position measuring units are each configured as continuous These position measuring units are designed for continuous position measurement across their respective partial strokes. Therefore, the position measuring units are not designed as position switches that can only detect a single discrete position, such as the end position, but rather allow for continuous position measurement across the partial strokes.

It is particularly preferred that, during the movement of the actuator element from the first end position to the second end position, the position of the actuator element is first continuously measured over the first partial stroke using the first position measuring unit. Subsequently, no position measurement is performed over a certain stroke distance, and then the position of the actuator element is continuously measured over the second partial stroke using the second position measuring unit. During the return movement of the actuator element from the second end position to the first end position, the position measurements can be performed in reverse order.

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

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 outer housing. Advantageously, the position measuring units are thus separately formed components of the position measuring device.

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.

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 in the form of a trajectory or path curve, for example. 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 pressure control to the position control within the partial strokes, which is expediently active over the entire travel stroke. Alternatively, position control without subordinate pressure control would also be possible; for example, pressure values could be estimated.

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 position control is switched to position monitoring.

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 region of the end positions. Alternatively, however, it is also conceivable that the partial strokes in which measurements are taken do not correspond to the end positions, or, as a logical 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.

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.

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

• 1 eine schematische Darstellung eines bevorzugten Ausführungsbeispiels des erfindungsgemäßen pneumatischen Systems mit dem das erfindungsgemäße Verfahren durchführbar ist,
• 2 ein Blockdiagramm des erfindungsgemäßen Verfahrens zum Betrieb eines pneumatischen Systems für die Industrieautomation,
• 3 eine schematische Darstellung einer Wafer-Bearbeitungsanlage, die mehrere pneumatische Systeme gemäß 1 aufweist und
• 4 eine schematische Darstellung eines Teils des pneumatischen Systems von 1, wobei eine Ausführungsform eines Schieberventils gezeigt ist, das sich in einer deaktivierten Stellung (links) und in einer aktivierten Stellung (rechts) befindet.

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

• 1 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,
• 2 a block diagram of the inventive method for operating a pneumatic system for industrial automation,
• 3 a schematic representation of a wafer processing plant which incorporates several pneumatic systems according to 1 exhibits and
• 4 a schematic representation of part of the pneumatic system of 1 , wherein an embodiment of a slide valve is shown which is in a deactivated position (left) and in an activated position (right).

The 1 Figure 1 shows a preferred embodiment of the pneumatic system 11 according to the invention, which is shown and described here as an example for use in a wafer processing system 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 system 12 is therefore purely exemplary.

As particularly in 1 As shown, the pneumatic system has a control device 13 to which at least one pneumatic actuator 14 is assigned.

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

The construction of such a wafer processing system 12 is described in the 3 Shown purely schematically and as an example.

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.

In distribution room 15, which is located in the 3 In a top view shown and having 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.

Between the distribution room 15 and the adjacent processing rooms 16 are passageways, each equipped with slide valves 20, such as those found, for example, in the 1 and 4 are shown, are assigned.

As particularly in 1 As shown, 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 to seal the machining chamber 16 from the environment. The pressure in the machining chamber 16 is typically below atmospheric pressure.

As further in 1 As shown, 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 processing chamber 16, so that the processing 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 is aligned with the processing chamber opening 21.

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

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

The pneumatic actuator 25 is shown in the figures, especially in the 1 and 4 Illustrated by example in the form of a double-acting pneumatic cylinder.

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.

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 sliding element, is attached.

The valve element 33, i.e. the slide element in the example shown, 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.

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.

How in particular the synthesis of 4 As shown, 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 activated state, in which the valve element 33 is in a closed position 36, in which the opening 23 is fluid-tightly closed.

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.

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 _h1 , _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 _h1, 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 actual position signals to the control device 13.

In the example shown, the partial strokes _h1 , _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 two 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 _h1 , _h2 , within which a position measurement takes place, are not necessarily located in the region of the end positions 30, 31; it is 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 of the travel stroke.

The determination of the partial _{strokes h1} , _h2 , 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.

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.

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.

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.

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.

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.

One of the main tasks of the control unit 13, whose control scheme is in 2 example The purpose of this device, as shown in the diagram, 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 stirring up particles and allowing them to reach the wafer surface. The control device 13 can comprise a position control device 13a and a pressure control device 13b.

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.

The communication system underlying the signal connection can 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, IO Link, whereby a power supply can also be enabled via the signal connection.

• Zunächst befindet sich der pneumatische Aktor 14, also der doppelt wirkende Pneumatikzylinder in seinem deaktivierten Zustand. Das Ventilglied 33 befindet sich in der Bereitschaftsposition 35, das heißt die Öffnung 23 in die Bearbeitungskammer 16 ist offen. Das Aktorglied 27, also der Kolben befindet sich in seiner ersten Endlage 30, bei der es sich im gezeigten Beispielsfall um die untere Endlage 30 handelt.

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 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.

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

Advantageously, a trajectory or path curve is specified for the control device 13, or the control device 13 is used based on position reference values (x _ref , 2 ) calculates a trajectory that specifies how the actuator element 27 should move between the first end position 30 and the second end position 31.

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.

After the actuator 27 starts moving, actual position values are continuously measured in the area of the first partial stroke _h1 by means of the first position measuring unit 38a and transmitted to the control unit 13 in the form of actual position signals. Simultaneously, a subordinate pressure control takes place; that is, the actual pressures in the pressure chambers 29a and 29b are measured and also transmitted to the control unit 13 in the form of actual pressure signals.

If the actual position deviates from the target position, adjustments are made to minimize the deviation. This means 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.

In the example shown, the comparison of the actual position with the target position is initially only carried out within the first partial stroke h ₁ , 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.

The position control within the first partial stroke _h1 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 a hard stop.

A characteristic feature of the described control system is that no position control takes place between the two partial strokes _h1 , _h2 ; that is, after leaving the first partial stroke _h1 , no position control takes place initially, but position control is carried out with the still active pressure control.

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 _h2, 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 to prevent the valve element 33 from impacting the closed position 36 abruptly.

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 _h2 is traversed, then the distance during which no position control takes place, and then the movement into the first partial stroke _h1 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.

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

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 known as L-Motion, in which the vertical stroke is initially performed, for example, with the [missing information]. 1 The movement is carried out by the double-acting pneumatic cylinder shown, and subsequently the horizontal stroke is achieved 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.

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

Finally, another alternative is a motion control 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.

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

Claims (13)

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 of: - measuring a position of the actuator element (27) by means of a position measuring device (37), which includes a first position measuring unit (38a) assigned to a first partial stroke ( _h1 ) of the travel stroke (H) of the actuator element (27) and a second position measuring unit (38b) assigned to a second partial stroke ( _h2 ) of the travel stroke (H), wherein, depending on the position of the actuator element (27), either the first or the second position measuring unit is used. (38a, 38b) is measured and no position measurement takes place between the partial strokes (h ₁ , h ₂ ), - providing the measured position as an actual position signal to the control device (13), - carrying out a position control based on the actual position signal recorded by the position measuring device (37). Procedure according to Claim 1 , characterized in that , during the movement of the actuator element (27) from the first end position (30) to the second end position (31), the position of the actuator element (27) is first continuously measured over the first partial stroke (h ₁ ) 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 (h ₂ ) with the second position measuring unit (38b), wherein, 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. Procedure according to Claim 1 or 2 , characterized in that the actual pressure is measured in a pressure chamber (29a, 29b) of the actuator element (27) and the actual pressure is provided as an actual pressure signal to the control device (13). Method according to one of the preceding claims, characterized in that the first and/or the second partial stroke (h ₁ , h ₂ ) are assigned to one of the end positions (30, 31) of the actuator element (27). Method according to one of the preceding claims, characterized in that position control is carried out in the partial strokes (h ₁ , h ₂ ) and between the partial strokes, where no position measurement takes place, the position control is switched to position monitoring. Method according to one of the preceding claims, characterized in that one of the partial strokes (h ₁ , h ₂ ) is assigned to one of the end positions (30, 31) and the other partial stroke (h ₁ , h ₂ ) is not located at one of the end positions, for example, is located in the middle between the end positions (30, 31). 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). Method according to one of the preceding claims, characterized in that the pneumatic actuator (25) is a single- or double-acting pneumatic cylinder. 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 ( _h1 ) of the travel stroke (H) of the actuator element (27) and a second position measuring unit (38b) assigned to a second partial stroke ( _h2 ) of the travel stroke (H), wherein, depending on the position of the actuator element (27), a position measurement can be carried out with either the first or the second position measuring unit (38a, 38b) and between the partial strokes (h2) ₁ , h ₂ ) a lifting distance that is free of measurement with respect to a position measurement. Pneumatic system according to Claim 9 , characterized in that the position measuring units (38a, 38b) are each designed as continuous position measuring units (38a, 38b) for continuous position measurement over the respective assigned partial strokes (h ₁ , h ₂ ). Pneumatic system according to Claim 10 , characterized in that the position measuring units (38a, 38b) are each designed as continuous position measuring sensors. Pneumatic system according to one of the Claims 9 until 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. 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).