EP1812718B1 - Diagnosis device for at least one pneumatic valve actuator arrangement - Google Patents

Abstract

A diagnostic device for at least one pneumatic valve actuator arrangement, comprises a pressure sensor, a volumetric flow sensor, a control means for producing control signals for the valve actuator arrangement and position sensors for detecting the position of at least one moving actuator member. The diagnostic device also includes a first diagnostic module for leak detection, a second diagnostic module for the detection of a choking effect in pneumatic supply and venting lines and at least one third diagnostic module for the detection of load and friction changes in the case of the moving actuator member and/or of valve switching faults, switching means being provided for deactivating the at least one third diagnostic module in the case of the detection of a fault by the first and/or second diagnostic module. Using this diagnostic device it is possible to detect, owing to cooperation of the diagnostic modules, faults and trouble conditions in an extremely systematic fashion both qualitatively and quantitatively.

Description

The invention relates to a diagnostic device for at least one pneumatic valve-actuator assembly, comprising a pressure sensor, a volumetric flow sensor, a control device for generating control signals for the valve-actuator assembly and position sensors for detecting the position of at least one movable actuator member.

Such diagnostic devices are for example from the DE 19628221 C2 or the DE 10052664 A1 known and serve in particular for process monitoring. In the known devices stored reference curves for the pressure, for example, on an actuator, and / or for the volume flow of the Pneumatikmediüms with currently measured pressure curves and flow curves are compared, with transgressions of predetermined tolerances lead to diagnostic messages. The known devices are only suitable for determining the fault location, that is to say which valve or which actuator or which valve-actuator arrangement has a malfunction. However, the exact nature of the malfunction can not be determined in the known devices. Furthermore, a diagnostic device according to the preamble of claim 1 is made US 2004/39488 A1 known. An object of the present invention is to provide a diagnostic device for such valve-actuator attachments create, by which the type of error occurred can be detected and reported.

This object is achieved by a diagnostic device with the features of claim 1.

The advantages of the diagnostic device according to the invention are, in particular, that errors that occur can be determined precisely while avoiding complex mathematical models and with relatively low required sensor technology. The generated diagnostic messages provide clear information about the type and location of the fault in the valve-actuator assembly. Through the interaction of different diagnostic modules and in particular by the order of execution of clear error statements can be made and error detection can be avoided.

The measures listed in the dependent claims advantageous refinements and improvements of the claim 1 diagnostic device are possible.

Advantageously, the third diagnostic module is used to detect load and friction changes in a movable actuator member, wherein a fourth diagnostic module for detecting valve switching errors is provided, which is deactivated in an error detection by the third diagnostic module. This is to distinguish these two types of errors safely.

The first diagnostic module is designed for monitoring the pressure medium of the pressure sensor in a closed, pressurized chamber of the actuator while preferably detected by position sensors pause phases. These can thereby be advantageously used for diagnosis. For this purpose, the first diagnostic module has means for determining the pressure gradient and / or the leakage volume flow and / or the Strömungsleitwertes for the leakage point and comparison means for comparison with reference values, the exceeding of which generates a leakage message. From this even quantitative data can be determined. Taking into account the fact that in an internal leak (for example, defective piston seal) the leakage path is getting smaller, while it remains almost constant over an external leak over the measuring time, can also be distinguished by appropriate evaluation internal and external leakage.

The recognition of a throttling in the valve-actuator arrangement is advantageously carried out by the second diagnosis module, which in each case has the flow conductance during movement phases of the movable actuator member detected by the position sensors. The second diagnostic module thus operates alternately to the first diagnostic module, which operates in the pause phases.

The second diagnostic module expediently has means for calculating the mean value of the flow conductance during the movement of the actuator member, wherein comparison means for checking this mean value are provided for deviations from at least one reference value which generate a message about an irregular throttling from a predefinable limit value deviation. Since the temperature not insignificantly influences the flow conductance, switching means are provided which deactivate the second diagnostic module when a predeterminable limit temperature or extreme temperature changes are exceeded.

The third diagnostic module serving to detect load and friction changes in the movable actuator member is preferably designed to monitor one of the following pressure values for deviations from predefinable standard pressure values: maximum pressure between actuation signal and corresponding start of the movement phase from one end position, mean pressure during the movement phase when filling an actuator chamber, mean pressure during the movement phase when this actuator chamber is emptied. If all these pressure values are recorded, a large number of possible errors with regard to load and friction changes can be distinguished. Only the signal of the pressure sensor and position sensors for motion detection is needed.

A preferred type of evaluation is performed by means for calculating the equivalent force values and for determining and evaluating difference values with respect to corresponding standard values.

The fourth diagnostic module used for the detection of valve switching errors only comes into operation if all other diagnostic modules do not generate diagnostic messages. Only then can safely be closed valve switch error. For this purpose, the time of the pressure increase from a corresponding valve switching signal to a predeterminable percentage value of its pressure end value and / or the time of the pressure reduction from a corresponding valve switching signal to a predefinable reduced percentage value of its pressure end value is advantageously monitored. For this purpose, the fourth diagnostic module has means for detecting the pressure end value in the filled actuator chamber and standstill of the actuator.

In a preferred embodiment, the fourth diagnostic module has means for time recording the pressure rise and / or pressure reduction times and for determining the difference value Standard times that generate a diagnostic message when the specified difference values are exceeded.

A further improvement and completion of the diagnosis can still be achieved by a permanently operating fifth diagnostic module, which is designed for monitoring the air consumption and / or the pressure level and / or positioning times and cycle times, wherein switching means for deactivating the at least one third diagnostic module in an error detection serve through the fifth diagnostic module. As a result, faults can be detected as faults that can not be unambiguously assigned to the faults in the other modules and, regardless of the type of fault, detect corresponding faults in the air consumption, in the pressure level or in the positioning times and cycle times.

The fifth diagnostic module expediently has comparison means for comparison with corresponding reference values, for detecting deviations from the reference values and for checking the deviations to exceed predefinable limit values, which lead to a diagnostic message.

• Figur 1 eine als Pneumatikzylinder und Steuerventil für diesen ausgebildete Ventil-Aktuator-Anordung, die mit einer Diagnosevorrichtung als Ausführungsbeispiel der Erfindung verbunden ist, und
• Figur 2 eine detailliertere Darstellung und Unterteilung der Diagnosevorrichtung in Diagnosemodule.

An embodiment is shown in the drawing and explained in more detail in the following description. Show it:

• FIG. 1 a designed as a pneumatic cylinder and control valve for this valve-actuator assembly, which is connected to a diagnostic device as an embodiment of the invention, and
• FIG. 2 a more detailed representation and subdivision of the diagnostic device in diagnostic modules.

In the FIG. 1 illustrated valve actuator assembly consists of a schematically illustrated pneumatic cylinder 10 in which a provided with a piston rod 11 piston 12 is slidably and pneumatically driven. This pneumatic cylinder 10 represents a possible embodiment of an actuator, although other types of actuators, such as different types of linear drives, actuators, rotary drives and the like, are possible.

For actuating the piston 12 is a valve 13, which may be formed for example as a 5/2 or 5/3 switching valve. This valve 13 is connected to a pressure supply line 14 for supplying a working pressure p. Via lines 15, the piston 12 can be acted upon depending on the valve position on one side or the other with the pressure so that it can move controlled in the two directions of movement. Instead of a switching valve can in principle also be provided a proportional valve, wherein the respective valve can also be integrated in or on the pneumatic cylinder.

In the two lines 15 between the valve 13 on the one hand and the two end portions of the pneumatic cylinder 10 on the other hand throttle check valves 16 are connected in the usual way. In the piston rod side of the piston 12 with pressure acting line 15, a volume flow sensor 17 and a pressure sensor 18 for detecting the pneumatic pressure in the piston rod side cylinder chamber 19 are still arranged. In principle, the volume flow sensor 17 and the pressure sensor 18 may also be connected to the opposite cylinder chamber 20.

An electronic control device 21 serves to control the valve 13 and thus the movement and position of the piston 12 in the pneumatic cylinder 10. This electronic control device 21 is provided with a diagnostic electronics 22, wherein the diagnostic electronics 22 integrated in the electronic control device 21 or can be äusgebildet as a separate device. The pressure sensor 18 and the volume flow sensor 17 and position sensors 23, 24 for detecting the end position or end positions of the piston 12 are connected to inputs of the diagnostic electronics 22. The control signals of the electronic control device 21 for the valve 13 are also supplied to the diagnostic electronics 22, in the illustrated integrated form by internal supply.

Errors, malfunctions or defects detected by means of the diagnostic electronics 22 can be displayed and / or registered. For this purpose, the diagnostic electronics 22 or the electronic control device 21 may have a corresponding fault memory. Furthermore, the diagnostic electronics 22 on the output side connected to a display 25 and a printer 26 to display or print diagnostic messages can. These serving as display devices for diagnostic message devices can of course be replaced by other and simpler devices, such as an LED error display, through which the various types of errors can be displayed.

In FIG. 2 the diagnostic device is shown schematically with regard to the diagnostic procedure and the diagnostic functions. What is essential is the interaction of the individual diagnostic modules M1 to M5 or the sequence of their processing in order to make clear error statements. Essential here is the targeted evaluation of the diagnostic information from the individual diagnostic modules M1 to M5 for a pneumatic subsystem, which in the exemplary embodiment according to FIG. 1 is realized by a valve-actuator arrangement 10, 13 is. The diagnostic modules M1 to M5 monitor the valve-actuator arrangement for frequently occurring qualitative and quantitative errors.

The diagnostic modules according to FIG. 2 are basically only activated if the operating pressure p does not deviate from a reference pressure by more than specified tolerances. In a first step, the diagnostic modules M1 and M2 are started to check the subsystem for leaks or restrictions in the working line. These two modules are permanently active with the above restriction because they always provide clear statements. If there are no leaks or throttling, the M3 module is activated to monitor changed loads or friction. If this module does not provide any deviations from specified reference standards, the module M4 can be activated for the detection of valve faults. If an error occurs in this chain, the following module is always deactivated. This is schematically represented by switches 27, 28. This sequence ensures that the diagnostic modules always make clear error statements.

The diagnostic module M5 works constantly. This module M5 monitors the cycle and travel times, the pressure and the air consumption for deviations. Irrespective of the type of fault, faults in the subsystem are detected that are noticeable in the travel times or the pressure or the volume flow. Thus, errors are also detected as faults which can not be unambiguously assigned to the faults in the diagnostic modules M1 to M4. The NOR operation 29 causes the diagnosis modules M3 and M4 to be activated only if the diagnosis modules M1, M2 and M5 do not report any errors or disturbances. As already stated, the diagnostic module M4 has the additional condition that the diagnostic module M3 does not detect any errors or malfunctions.

During the first diagnostic module M1 serving to detect a leakage, the side under the pressure p1 is shut off during pause phases in which the piston 12 is in one of its two end positions. In the illustrated embodiment, this is the cylinder chamber 19, since it is connected to the pressure sensor 18. During this measuring time, which corresponds to the length of the pause phase, the pressure gradient Δp / Δt is determined. The pressure difference is then determined from the difference between the initial value and the final value. The calculated leakage current changes over time as the pressurized cylinder chamber 19 deflates. The leakage current Q _I results in: $$Q_t=\frac{V*\mathrm{\Delta }p/\mathrm{<malignmark>\; </malignmark>}}{{\mathrm{p}}_{\mathrm{N}}}$$

Where V is the chamber volume and PN is the reference pressure, both of which are constants. In order to obtain a comparison value about the size of the leakage point, the conductance C is calculated. The C value is proportional to the opening area of the leakage point and is calculated as follows: $$C=\frac{Q_l}{p}$$

The conductance C is constantly updated as the pressure gradient during the entire measurement process, so is a function of time C = C (t). If no leakage occurs, the conductance C assumes values close to zero. Due to measurement noise, however, a value> 0 is assumed as the conductance reference C _ref . The measured C value exceeds the reference conductance in case of leakage and is then approximately constant. In order to have a meaningful comparison value, the C values determined during the measuring process become a maximum value C _max determined. This is then compared with the reference master.

The pause phases or measuring time are detected by limit switch signals and by knowledge of the sequence of execution. If the supply pressure p drops below a predeterminable minimum value, for example 2 bar, then the formula for calculating the conductance is no longer valid and the measuring process is aborted.

To detect different leakages, the size of the master value reference can be adjusted individually. An additional evaluation allows the distinction between an internal leakage at the piston, for example in case of leaking or defective piston seal, and an external leakage, for example, by leaking or defective piston rod seal or defective hoses or lines. In the event of internal leakage, venting takes place in the other cylinder chamber. As a result, the pressure drop is relatively large at the beginning, and with increasing pressure increase in the filling chamber, the leakage current and the C value is getting smaller, until the volume flow and C value go to zero at pressure balance. This is a clear indication of internal leakage. An additional indication of an internal leakage is that when the piston seal and shut-off chamber overflow, a movement of the actuator is possible, if it is an actuator with different effective surfaces, as is the case for example with the differential cylinder. When overflowing takes place a pressure equalization between the two actuator chambers. Due to the different piston surfaces results in a force effect, through which the actuator moves from the end position. By means of the limit switch signal of the position sensor 24 or 23 this is detectable.

In the event of external leakage, venting to the outside takes place. With complete emptying of the cylinder chamber can be closed definitely on external leakage. Here, the C value is almost constant over the measuring time, and the criterion for the height of the leakage is the C value at the end of the measurement. If the measurement time is insufficiently long enough, complete emptying will not be achieved and it will no longer be possible to distinguish clearly between external and internal leakage. For most applications, however, an external leakage can be inferred when the pressure drops steadily over the measuring time. The measuring time should therefore be as long as possible, that is, the break times should be effectively utilized.

If the quantitative size of the leakage flow is of interest, the reference pressure p _n must be determined according to the following equation: $${\mathrm{p}}_{\mathrm{n}}\mathrm{=}\mathrm{\kappa }\mathrm{*}{\mathrm{\rho }}_{\mathrm{N}}\mathrm{*}\mathrm{T}\mathrm{*}\mathrm{R}$$

ρ _N is the standard density, whereby ρ _N = 1.293 kg / m ³ , depending on the selected normalization of the volume flow. T is the reference temperature, and the operating temperature can be used for estimation. The deaeration process is assumed to be isothermal, therefore κ = 1.0. R is 287 J / (kg K) for dry air and R = 288 J / (kg • K) for air at 65% relative humidity. This results in a reference pressure for normal conditions, which corresponds to the standard pressure of Pn of 1.0135 bar. This value can be used in the first equation, from which the leakage current can be calculated with the help of the other parameters.

The detection of an increasing or decreasing throttling (eg throttle adjustments or blockages or kinked hoses) is based on the use of the pressure signal p1 and the volume flow q in the relevant working line. The sensor is doing according to FIG. 1 arranged on the piston rod side, that is connected to the cylinder chamber 19. The diagnostic module M2 determines whether there is a restriction in the entire line starting from the valve 13 to the connection to the cylinder chamber 19. Causes of an increasing or decreasing throttling are, for example, an open or closed outlet throttle, a kinked hose, blockages in the hose, icing, throttling in the connecting line of the pneumatic cylinder 10, not completely opening valve.

p_u ist dabei der Umgebungsdruck, gegen den entlüftet wird. Die Gleichung beschreibt dabei die Verhältnisse bei unterkritischen Betriebsbedingungen, bei denen gilt pu_/p1 > b. Der Kennwert b kann für die Diagnose als Konstante b = 0,528 frei gewählt werden. T_N ist die Normtemperatur und T_B ist die Temperatur in der Druckkammer, welche näherungsweise der Betriebstemperatur gleichgesetzt werden kann. Wenn keine extremen Temperaturveränderungen vorliegen, so wird die Temperatur für die Diagnose nicht berücksichtigt. Bei großen Änderungen der Temperatur wird das Diagnosemodul M2 deaktiviert.First, a conductance C is determined as the diagnosis value from the pressure p1 and the volume flow q. This C-value is a measure of the area flowed through and is compared with a reference value for fault diagnosis. For calculating the conductance C, the extension and / or the retraction direction of the actuator can be used. Sufficient is a movement phase. Preferably, the movement direction X according to FIG. 1 used, in which a vent from the cylinder chamber 19 takes place. The conductance C for this extension direction is calculated according to the following equation: $$q=C*p1\sqrt{\frac{T_N}{T_B}}*\sqrt{1-{\left[\frac{p_n/p_1-b}{1-\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="imgf0001.png"\; state="\{\{state\}\}">b</figure-callout>}}\right]}^2}$$

p _u is the ambient pressure against which is vented. The equation describes the conditions for subcritical operating conditions in which pu _/ p1> b. The characteristic value b can be free for the diagnosis as a constant b = 0.528 to get voted. T _N is the standard temperature and T _B is the temperature in the pressure chamber, which can be approximately equated to the operating temperature. If there are no extreme temperature changes, the temperature is not taken into account for the diagnosis. If the temperature changes significantly, the diagnostic module M2 is deactivated.

For supercritical operating conditions (p _u / p1 <= b) the following equation applies: $$q=C*p1\sqrt{\frac{T_N}{T_B}}$$

The calculated conductance C is constantly updated throughout the measurement process, ie is a function of time C = C (t). With a constant flow area, however, the dynamically calculated conductance is almost constant. In the case of venting or filling start, however, pressure peaks and thus also short peaks in the conductance can occur. During the measuring process, an average value is calculated from the calculated conductance C and compared with a reference conductance. The difference between the measured value and the reference master value is compared with a maximum permissible tolerance value, the exceeding of which results in a diagnostic message indicating that the throttling is too great or too small. The conductance is determined during the movement of the piston 21, for which purpose the two limit switch signals of the position sensors 23, 24 are used.

The diagnostic module M3 is used to detect load and friction changes on the actuator, ie on the pneumatic cylinder 10 or on the attached mechanism. As already stated, this module is activated only if it has been previously ensured that no restrictions or leaks have occurred Thus, the diagnostic modules M1 and M2 have found no errors, which also applies to the diagnostic module M5, which will be described. For this diagnosis, only the pressure sensor 18 is needed. For the calculation, the pressure build-up phase (filling of the cylinder chamber 19) and the movement phases (extension and retraction) can be used. These phases are described below.

During the pressure build-up phase (phase 1) is the piston 21. This phase is defined from the switching signal on the valve 13, to the time at which the piston-12 moves from its end position. Phase 2 is the travel phase in which the cylinder chamber 19 is filled. Phase 3 is the travel phase in the opposite direction, ie in the direction X, in which the cylinder chamber 19 is emptied again.

In phase 1, the occurring maximum pressure is determined. With the known piston effective area, the equivalent force F _{max is} calculated. It is assumed that the second cylinder chamber 20 is vented at standstill of the piston or there prevails a constant pressure. From the measured pressure during the travel time in phase 2, a mean pressure is calculated, from which in turn an average equivalent force Fmed1 is calculated. The same applies to phase 3, in which an average equivalent force Fmed2 is again calculated. To calculate the mean pressure values, these are summed up and divided by the number of measured values. To obtain meaningful values, it is recommended to record the characteristic values over several cycles, the intermediate storage and subsequent generation of mean values.

1. a) Überschreitet einer der Differenzwerte signifikant den vorgegebenen Toleranzwert, so liegt ein Fehler in den Reibungs- oder Lastverhältnissen vor.
2. b) Sind alle drei Differenzwerte positiv und überschreiten einen vorgegebenen Toleranzwert, so liegt eine ziehende Last vor, also eine gegen die jeweilige Kraftrichtung gerichtete Last.
3. c) Sind alle drei Differenzwerte negativ und überschreiten einen vorgegebenen Toleranzwert, so liegt eine drückende Last vor, also eine Last, die in Kraftrichtung wirkt.
4. d) Übersteigt ΔF_max seine zulässige Toleranzgrenze, bleiben die übrigen Werte jedoch innerhalb ihrer Toleranzgrenzen, so liegt eine Haftreibungserhöhuag vor.
5. e) Steigt der Differenzwert ΔF_medi und sinkt der Wert ΔF_med2 über die jeweilige Toleranzgrenze, so hat sich die Gleitreibung erhöht.

For all measured force values stored reference values are present, which occur with proper function. From these and the measured force values are now each difference values ΔFmax, ΔF _med1 and Δf _med2 . During the evaluation, it is now checked whether these difference values are outside specified tolerance limits. From the combinations of the results obtained, various diagnostic statements can be made:

1. a) If one of the difference values significantly exceeds the specified tolerance value, then there is an error in the friction or load conditions.
2. b) If all three difference values are positive and exceed a predetermined tolerance value, then there is a pulling load, ie a load directed against the respective force direction.
3. c) If all three difference values are negative and exceed a predetermined tolerance value, there is an oppressive load, ie a load acting in the direction of force.
4. d) If ΔF _max exceeds its permissible tolerance limit, however, the remaining values remain within their tolerance limits, so there is an increase in static friction.
5. e) If the difference value ΔF _{medi increases} and the value ΔF med2 _falls above the respective tolerance _limit , the sliding friction has increased.

Other combinations allow additional statements. The respective combinations can also be refined actuator-specific. The results can be stored and displayed on the display 25 or via the printer 26.

The reference values can be entered manually or can be determined automatically. It should be noted that these reference values are recorded in the "good" condition of the cylinder (or another actuator or a system) or during retraction.

The diagnostic module 4, which is used to detect valve switching errors, is only activated if the other diagnostic modules do not report faults, faults or faults. If all these diagnostic modules M1 to M3 and M5 have shown no error and yet changes occur in the pressure build-up, this is due to a delayed or accelerated opening behavior of the valve 13. For detection, only the pressure sensor 18 in the respective working line is required. It is, as described in the diagnostic module 3, the pressure build-up phase used to measure the time of pressure rise. Then a diagnostic characteristic is formed, which characterizes the switching time. From the comparison of this switching time with a reference switching time can then be concluded that the correct or incorrect switching of the valve 13. A measuring phase 1 begins when switching on the valve 13, ie with its switch-on signal, and ends with the movement start of the piston from its end position. In addition, the pressure reduction or deaeration phase is used as measurement phase 2. Thus, the time for switching back the valve can be evaluated. The measuring phase 2 begins when switching on or switching the valve 13, while the piston is in its end position.

In the measuring phase 1 representing a pressure build-up phase, the time is measured until the pressure has risen to a predetermined percentage value of its end value or maximum value. The same applies to the trained as pressure reduction phase measurement phase 2, in which the time is measured until the pressure on a predetermined percentage of its maximum value has fallen. The measured time values are compared with reference time values and again the formed difference values are checked for exceeding given tolerance values.

For diagnosis, the end value or maximum pressure value of the filled chamber at standstill is required. This value can be measured and saved once, but can also be updated with each measurement.

The diagnostic module 5 works permanently. It requires the limit switch signals of the position sensors 23, 24 and the signals of the pressure sensor 18 and the volume flow sensor 17. In this module, the cycle and travel times, the pressure and the air consumption are formed and monitored for deviations. Irrespective of the type of error, this diagnostic module therefore detects faults in the monitored subsystem that are noticeable in the travel times or the positioning times or the pressure or consumption. Thus, errors can also be detected as failures that are not clearly attributable to the errors. are ordenable, which can be detected by the other modules. The respective measured values, ie positioning time, travel time, air consumption, maximum pressure value and average pressure value, are compared with corresponding reference values. From this, differential values are formed and checked for under- or exceeding of permissible tolerance values. In individual cases, this error micro detection can then be specified by the more exact error determination of the diagnostic modules M1 to M4.

The diagnostic modules M1 to M3 represent the most important diagnostic modules. For simpler versions, the diagnostic module M4 and / or M5 can also be dispensed with. It is included of course also possible to add additional diagnostic modules.

The diagnostic modules can in principle be designed as separate diagnostic circuits, but they are preferably designed as functional groups of a diagnostic program that runs either in the diagnostic electronics 22 or in the electronic control device 21 or a central control electronics.

Claims (17)

1. Diagnostic device for at least one valve and actuator assembly, with a pressure sensor (18), with a volumetric flow rate sensor (17), with a control unit (21) for the generation of control signals for the valve and actuator assembly and with position sensors (23, 24) for the detection of the position of at least one movable actuator element (12), with a first diagnostic module (M1) for leakage detection, with a second diagnostic module (M2) for the detection of a restriction in pneumatic supply or discharge lines and with at least one third diagnostic module (M3, M4) for the detection of load and friction changes at the movable actuator element (12) and/or of valve switching faults, characterised in that switching means (29, 27) are provided for the deactivation of the at least one third diagnostic module on detection of a fault by the first diagnostic module (M1) and/or the second diagnostic module (M2).
2. Diagnostic device according to claim 1, characterised in that the third diagnostic module (M3) is designed for the detection of load and friction changes at the movable actuator element (12), and in that a fourth diagnostic module (M4) is provided for the detection of valve switching faults, which is deactivated on detection of a fault by third diagnostic module (M3).
3. Diagnostic device according to any of the preceding claims, characterised in that the first diagnostic module (M1) is designed for monitoring the pressure (p1) by means of the pressure sensor (18) in a closed, pressurised chamber (19) of the actuator (10) during pause phases which are preferably detected by position sensors (23, 24).
4. Diagnostic device according to claim 3, characterised in that the first diagnostic module (M1) is provided with means for determining the pressure gradient (Δp/Δt) and/or the leakage flow (Q1) and/or the flow conductance (C) value of the leakage point, and with comparison means for comparing these to reference values which, if exceeded by presettable tolerance values, generate a leakage message.
5. Diagnostic device according to claim 3 or 4, characterised in that the first diagnostic module (M1) is provided with evaluation means for distinguishing between an internal or an external leakage.
6. Diagnostic device according to any of the preceding claims, characterised in that the second diagnostic module (M2) is designed for monitoring the flow conductance (C) value during movement phases of the movable actuator element (12) detected by the position sensors (23, 24).
7. Diagnostic device according to claim 6, characterised in that the second diagnostic module (M2) is provided with means for calculating the average value of the flow conductance (C) value during the movement of the actuator element (12), and in that comparison means are provided for checking this average value for deviations from at least one reference value, which generate an irregular restriction message from a presettable tolerance error.
8. Diagnostic device according to any of the preceding claims, characterised in that switching means are provided for deactivating the second diagnostic module (M2) if a presettable limit temperature is exceeded.
9. Diagnostic device according to any of the preceding claims, characterised in that the third diagnostic module (M3) is designed for monitoring at least one of the following pressure values for deviations from presettable standard pressure values:

   Maximum pressure between actuating signal and corresponding start of the movement phase from an end position, median pressure during the movement phase when charging an actuator chamber (19), median pressure during the movement phase when discharging the said actuator chamber (19).
10. Diagnostic device according to claim 9, characterised in that means are provided for calculating the equivalent force values (F_max, F_med1 and F_{med 2}) and for determining and evaluating differential values (ΔF_max, ΔF_med1 and AF_{med 2}) from corresponding standard values, wherein an appropriate diagnostic message is generated if presettable tolerance values are exceeded.
11. Diagnostic device according to any of the preceding claims, characterised in that the fourth diagnostic module (M4) is designed for monitoring the time of the pressure increase from an appropriate valve switching signal (V) to a presettable percentage of its final pressure value and/or the time of the pressure drop from an appropriate valve switching signal (V) to a presettable percentage of its final pressure value.
12. Diagnostic device according to claim 11, characterised in that the fourth diagnostic module (M4) is provided with means for detecting the final pressure value when the actuator chamber (19) is charged and when the actuator element (12) is stationary.
13. Diagnostic device according to claim 11 or 12, characterised in that the fourth diagnostic module (M4) is provided with means for detecting the pressure increase and/or pressure drop times and for determining differential values from reference times, which generate a corresponding diagnostic message if presettable tolerance values are exceeded.
14. Diagnostic device according to any of the preceding claims, characterised in that a fifth diagnostic module (M5) is provided for monitoring the air consumption and/or the pressure level and/or the positioning and cycle times, wherein switching means (27, 29) are provided for deactivating the at least one third diagnostic module (M3, M4) on detection of a fault by the fifth diagnostic module (M5).
15. Diagnostic device according to claim 14, characterised in that the fifth diagnostic module (M5) is provided with comparison means for comparison to appropriate reference values, for detecting deviations from the reference values and for checking the deviations for exceeding presettable tolerance values, which generate a corresponding diagnostic message.
16. Diagnostic device according to claim 14 or 15, characterised in that means are provided for detecting the air consumption between a valve control signal (V) initiating a movement and the arrival at an end position, wherein the air consumption preferably is the integral of the volumetric flow rate signal over positioning time.
17. Diagnostic device according to any of claims 14 to 16, characterised in that means are provided for detecting the maximum pressure value and/or the median pressure value during a movement phase of the actuator element (12).

Images