EP2047118B1 - Method for fault localization and diagnosis in a fluidic installation - Google Patents

Abstract

In a method for error containment and diagnosis in a fluid power system the fluid volumetric flow of the overall system or at least a part thereof or a quantity dependent thereon is detected as a measurement quantity respectively during an operating cycle and is compared with stored references. In each case at the point in time of a deviation or change in the deviation from the reference the method finds at which component or at which components (10 through 14) in the system an event has occurred influencing the fluid consumption in order to then to recognize same as subject to error. In the case of such a deviation or change therein and the simultaneous occurrence of several activities influencing fluid consumption by several components (10 through 14) a process of exclusion is performed, in which during the following activities involving at least one of such components (10 through 14) a check is made to see whether a deviation or a change in the deviation has occurred, and in each of such further examination steps the components involved are excluded from such further examination, if no deviation or change in the deviation takes place.

Description

The invention relates to a method for defect limitation and diagnosis on a fluidic system according to the preamble of claim 1. Such a method is known DE 10 2005 016 786 known.

At another, from the WO 2005/111433 A1 known methods, the air consumption curve is evaluated for error localization. In the event of deviations from a reference, it is concluded from the time of the deviation on the faulty subsystem (for example valve actuator unit) or the faulty component. Such errors, which can occur in fluidic systems, have their causes, for example, in the wear of the components, in improper mounting, loose fittings, porous hoses, process disturbances and the like, resulting in the movements of the fluidic drives outer, and other leaks of various kinds. For diagnostic errors due to the change of certain boundary conditions, such as pressure and temperature avoid, this document mentions the possible correction of air consumption with pressure and temperature. In particular, in large fluidic systems, in which a plurality of subsystems are sometimes active simultaneously, can not be determined with the known method, which of these components is faulty.

An object of the present invention is thus to improve the method of the type mentioned so that even with simultaneously active components and subsystems, an error, in particular a leak, can be unambiguously associated with a particular component or a particular subsystem.

This object is achieved by a method having the features of claim 1.

By virtue of the method according to the invention, the leakage location can be delimited stepwise in an advantageous manner, so that the fault location can be determined in a simple manner even with a large number of simultaneously active components or subsystems. This is all the more a special advantage, as a strictly sequential sequence in fluidic systems, especially in large fluidic systems, is relatively rare. Another advantage is that only the Aktorstellsignale and a volume flow sensor for determining the leakage location are required, that is, limit switches to actuators are not mandatory. The more different the axis movements are and the more different cycles occur with simultaneously moving subsystems or components or combinations thereof, the more advantageously the method according to the invention can be used. Not only is it trying to find the leak-causing subsystems or components, but also it Also definitely excluded subsystems, components or actuator chambers are excluded.

The stored references are fluid consumption reference curves formed from integrated volume flow values or conductance reference curves formed from integrated conductivity values (Q / P), which are compared with corresponding measured-value curves.

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

An even greater diagnostic accuracy and accuracy in finding leakage locations is achieved by parameter-dependent compensation of the volume flow values or conductance variables, the compensation being temperature dependent and / or fluid dependent and / or humidity dependent and / or dependent on the particle content of the fluid and / or time or event dependent for different Operating conditions takes place.

Expediently, a plurality of parameter-dependent or parameter-dependent compensated fluid consumption reference curves or conductance reference curves are stored in a selection matrix and can be selected or specified for the respective cycle, for example, by checking them successively for correlation with the respective work cycle.

The reference curves are expediently detected in a learning mode, in particular also during the later operation of the fluidic system.

To rule out that detected deviations from the measurement curve and the reference curve are based on a time error, a curve comparison with respect to possible temporal displacements is preferably carried out before the diagnosis of leakage, with a tolerance value exceeding time shift is switched to other stored reference curves for their verification or an error message and / or a stop of another leakage diagnosis is triggered.

In the case of the leakage diagnosis according to the invention, differential values or a difference curve between the measured variable curve and the reference curve are formed for particularly advantageous evaluation. This difference curve is expediently filtered in a frequency-dependent manner by means of an integrator, which in particular has a phase shift of -90 ° in order to filter out interference signals and interference peaks. A filtered compensation curve is then formed by calculating the slope of the integral of the difference values or the difference curve, which then enables a particularly simple, purposeful evaluation.

Figur 1

eine pneumatische Anlage, in deren Zuführung ein Durchflussmesser geschaltet ist,

Figur 2

ein Leitwertdiagramm zur Erläuterung des Auftretens einer zeitlichen Verschiebung zwischen Messkurve und Referenzkurve und

Figur 3

Leitwertdiagramme zur Erläuterung der Diagnose auf Leckage.

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

FIG. 1

a pneumatic system, in the supply of which a flow meter is connected,

FIG. 2

a Leitwertdiagramm to explain the occurrence of a time shift between the trace and reference curve and

FIG. 3

Conductivity diagrams to explain the diagnosis of leakage.

In FIG. 1 a pneumatic system is shown schematically, which could in principle also be another fluidic system, such as a hydraulic system, act.

The pneumatic system consists of five subsystems 10-14 or components, which may each be actuators, such as valves, cylinders, linear actuators and the like, as well as combinations of the same. These subsystems 10-14 are fed by a pressure source 15, wherein in a common supply line 16, a flow meter 17 for measuring the flow or the flow rate is arranged. The subsystems 11, 12, on the one hand, and the subsystems 13, 14, on the other hand, in turn each form a system with a common supply line.

An electronic control device 18 is used to specify the process of the system and is electrically connected to the subsystems 10-14 via corresponding control lines. The subsystems 10-14 receive control signals from the electronic control device 18 and send sensor signals back to them. Such sensor signals are for example position signals, limit switch signals, pressure signals, temperature signals and the like, which are not absolutely necessary in the simplest case.

The flowmeter 17 is connected to an electronic diagnostic device 19, in addition to the signals of a temperature sensor 20 and a pressure sensor 21 for measuring the temperature T and the pressure P in the supply line 16, ie the temperature and the pressure of the fluid supplied. Furthermore, a fluid sensor 23 for detecting the kind the fluid used and a moisture and / or particle sensor 24 for detecting the moisture content and the particle content of the fluid connected to the diagnostic device 19. This has in addition access to the sequence program of the electronic control device 18. The diagnostic results are supplied to a display 22, these diagnostic results of course also stored, printed, visually and / or audibly displayed or a central office via lines or wirelessly can be transmitted.

The sensors 20, 21 and 23 and 24 may also be omitted in a simplest embodiment, although at least one temperature sensor 20 and one pressure sensor 21 may be expediently provided.

Of course, the diagnostic device 19 can also be integrated in the electronic control device 18, which may contain, for example, a microcontroller for carrying out the sequence program and optionally for diagnosis.

In a very large number of subsystems or components, these can be divided into several groups, each group has its own flow meter 17 to independently diagnose the subregions of the system associated with the groups, as described in the prior art mentioned above.

The procedure for fault isolation and diagnosis will now be described below with reference to the described pneumatic system and in the Figures 2 and 3 illustrated Leitwertdiagramme explained.

The diagnosis can be made in the simplest case by comparing stored and selected fluid consumption reference curves be carried out with corresponding measured value curves, wherein the fluid consumption reference curves are formed from integrated or totalized volumetric flow values. Better results are achieved by using diagnostic control values, where the diagnostic control value is a characteristic variable of a fluidic system or of a fluidic system that consists of a variety of subsystems. The conductance characterizes the behavior of the entire system over a defined cycle. Conductance reference curves are formed in the simplest case of integrated conductivity values Q / P, where Q is the respective volume flow value and P is the measured working pressure. These conductance reference curves are compared with corresponding measured value curves, ie with measured value curves formed from integrated conductance variables. The Leitwertgrößen or Leitwertkurven and Leitwert-reference curves can be compensated and refined by other measurement parameters, for example by the measured operating temperature T, the moisture content and / or the particle content of the fluid, the type of fluid and of each time or event-dependent operating conditions. Such operating states are, for example, the warm-up, the operation after a long standstill, the reclosure when retrofitting or the operation after predetermined time intervals, so for example after a one-hour or ten-hour or several hours of operation. The following discussion of fault isolation and diagnosis is based on conductance, and fluid consumption values could be used accordingly.

To generate the reference curves, a repeating cycle of the entire process must be selected. Non-cyclic processes can be subdivided into subcycles, to which the diagnostic procedure is then applied. Different operating conditions in a process can be considered by taking and storing a set of reference curves in a selection matrix. This also applies to the influence of different parameters.

For evaluation, the respective measured curve must now be synchronized with the selected or selected reference curve, that is, without leakage, the two curves are congruent, with leakage they run synchronously in time, but show deviations in the amplitude. The two curves to be compared must therefore first be checked for correlation, that is, it must be checked whether temporal shifts have occurred, for example due to changes in processes within a cycle. If temporal shifts have been detected over a defined tolerance, the further evaluation of leaks is stopped and a message regarding changes in the times of subsystems is generated. A time error is detected when the value of the air consumption at the end of the cycle is within a tolerance range, but the cycle time is different, as in FIG. 2 is shown. There, the two curves run synchronously until the time ta, and from this point on a time difference Δt occurs between the curve Km and the reference curve Kref, which remains constant until the end of the cycle at the point in time tb. If a time error increases more and more as the cycle progresses, an attempt can be made to correlate by choosing another reference curve. Only when all stored reference curves have been checked and no correlation could be achieved, is there a faulty time shift, and a subsequent leak diagnosis is omitted. A corresponding message can then be displayed, saved or forwarded.

If no time error is detected, the difference between the nominal value or measured value and the reference value, that is, between the measured quantity curve Km and the reference curve Kref, takes place in the next step FIG. 3 , above, is shown. The formed difference curve, which in FIG. 3 , shown below, defines at each instant the summed distance of the measured quantity curve from the reference curve. The time points of leaks show the staircase increases in the difference. In the following evaluations, these increases in the difference are assigned to the leak-causing subsystems or components or actuator chambers.

In order to remove also unwanted fluctuations, glitches and the like, the calculated difference or difference curve can be filtered. In conventional filters, the change in the phase position and the amplitude is frequency-dependent. In order to achieve a frequency-independent filtering, an integrator is used, which has a fixed phase shift of -90 °. Thus, no different phase shift is to be considered in the later evaluation of the signals. The amplitude response can be adjusted by changing the sampling time so that there is a constant attenuation of the amplitude in the desired frequency range, while other frequencies are filtered.

For evaluation, a compensation function of the integral of the calculated difference is subsequently formed. The choice of the corresponding compensation function can be made according to the Gaussian least squares principle. It must be determined which curve best suits the calculated measurement points of the difference. In the following, a compensation straight line is selected as the simplest possibility of a compensation function. Of course, other compensation functions are possible. Any occurring leakage leads to a change in the slope and the center distance of the regression line to the abscissa. When determining the slope from the integral of the difference, a representation is obtained which corresponds to that in FIG. 3 shown difference curve, but is phase-shifted by minus 90 °. When calculating the center distance from the integral of the difference, there is also a representation that corresponds to the in FIG. 3 corresponds to the difference curve shown, but is phase-shifted by minus 90 ° and mirrored on the abscissa. The advantage of calculating the regression line is that leaks, ie changes in the slope always have the same effect in terms of time. Leaks at a later point in a cycle affect the center distance significantly more than leaks at the beginning of a cycle. In the later temporal range of references, higher, accumulated errors occur at the current value. Actual leaks therefore change the center distance much more clearly at a later point in the cycle than any deviations from the reference, for example due to aging of the system. The evaluation described below therefore takes into account both changes in the pitch, as well as changes in the axial distance.

• Zum Zeitpunkt t0 tritt eine Leckage auf. Zu diesem Zeitpunkt ist die Kammer A des Subsystems 10, die Kammer B des Subsystems 11 und die Kammer A des Subsystems 12 belüftet. Diese drei Kammern kommen somit als Ursache für die Leckage in Betracht. Gleichzeitig ist die Kammer B des Subsystems 10, die Kammer A des Subsystems 11 und die Kammer B des Subsystems 12 inaktiv, also nicht belüftet, sodass diese Aktuatorkammern von der weiteren Betrachtung ausgeschlossen werden.
• Zum Zeitpunkt t1 tritt eine weitere Leckage auf. Zu diesem Zeitpunkt ist die Kammer A des Subsystems 10, die Kammer B des Subsystems 13 und die Kammer A des Subsystems 12 belüftet. Dies bedeutet, dass die Kammer B des Subsystems 11 für die weitere Betrachtung ausgeschlossen ist und nur noch die Kammern A der Subsysteme 10 und 12 für die Leckage in Betracht kommen.
• Zum Zeitpunkt t2 ist die Kammer A des Subsystems 10, die Kammer B des Subsystems 14 und die Kammer A des Subsystems 11 belüftet. Die Kammer A des Subsystems 11 wurde bereits für die weitere Betrachtung ausgeschlossen. Die Kammer A des Subsystems 12 wird nun ebenfalls als Ursache für die Leckage ausgeschlossen, sodass abschließend festgestellt werden kann, dass die Kammer A des Subsystems 10 für die Leckage verantwortlich ist.

In the case of the exclusion principle according to the invention, it is possible in the course of the error analysis to exclude certain areas from the error consideration, so that the number of subsystems and components or actuator chambers which come into consideration for a leakage is increasingly reduced. This makes use of the fact that in machine operations, the same groups of subsystems never move at the same time, ie are active, or the same actuator chambers are never under pressure at the same time. Thus one limits the candidate actuator chambers more and more, and the statement leakage is becoming more and more defined. For example, actuator chambers are always excluded from further consideration for leakage if they are vented at a time and at the same time no leakage occurs. The following is a diagnostic cycle based on FIG. 3 exemplified:

• At time t0, leakage occurs. At this time, the chamber A of the subsystem 10, the chamber B of the subsystem 11 and the chamber A of the subsystem 12 are vented. These three chambers are thus considered as the cause of the leakage. At the same time, the chamber B of the subsystem 10, the chamber A of the subsystem 11 and the chamber B of the subsystem 12 are inactive, ie not ventilated, so that these actuator chambers are excluded from further consideration.
• At time t1, another leakage occurs. At this time, the chamber A of the subsystem 10, the chamber B of the subsystem 13 and the chamber A of the subsystem 12 is vented. This means that the chamber B of the subsystem 11 is excluded for further consideration and only the chambers A of the subsystems 10 and 12 for the leakage come into consideration.
• At time t2, chamber A of subsystem 10, chamber B of subsystem 14 and chamber A of subsystem 11 are vented. The chamber A of the subsystem 11 has already been excluded for further consideration. The chamber A of the subsystem 12 is now also excluded as the cause of the leak, so that it can be finally concluded that the chamber A of the subsystem 10 is responsible for the leakage.

It is often possible to detect the causative system even with a single increase of ΔK, that is to say with a single occurrence of a leak. For example, in a modification of the previously described example, leakage would occur only at time t0, to which chamber A of subsystem 10, chamber B of subsystem 11, and chamber A of subsystem 12 are vented, and subsequently at a later time Chamber B of subsystem 11 and chamber A of subsystem 12 vented while chamber A of subsystem 10 is not involved, and then leakage does not occur, then chamber B of subsystem 11 and chamber A of subsystem 12 may be causative Components are excluded, and it can then finally the chamber A of the subsystem 10 are recognized as causing leakage.

A particularly suitable type of evaluation, in particular in the case of a very large number of subsystems or components, is that each chamber of an actuator, that is, for example, two chambers in a working cylinder, are each assigned two counters. Furthermore, each chamber is assigned a timer. The timer is used to exclude additional actuator chambers or components from the consideration of a leak. If a chamber or a component is under pressure and no leakage occurs within a preselected time value of the timer, then this chamber is also treated as not involved in the leakage and excluded for further leak detection. The electrical components, ie counters and timers, are located, for example, in the diagnostic device 19. When starting an operating cycle, the timers are now started, and when a leak occurs, they are each reset to the value zero and there until the end kept the leakage. Now, if the chamber in question during the reset state of the timer or at least during a part of the reset state under pressure, this chamber comes as responsible for the leakage into consideration, and it is checked whether the slope and the center distance of the straight line or other Compensation function has increased by a predeterminable value or by a predefinable percentage (based, for example, on the respective maximum value of or one of the preceding cycles). In this case, the counter responsible for the grade and / or the counter associated with the offset will be incremented by the value 1. The more different the axis movements are for a plurality of simultaneously moving subsystems or components, and the more different cycles occur, the more accurate this method becomes. For each leak in which the corresponding component or chamber of a component is under pressure, the associated counters are incremented by a further counter value, depending on the increase in the slope and / or the center distance. The counts of both counters of a chamber or component are added together at the end of the cycle. The chamber with the highest total count at the end of an operating cycle is most likely to be responsible for the leakage. The chamber or component with the second highest total count is involved in the leakage with the second highest probability. This is important if several leaks occur in the system. If more than a defined percentage of chambers, eg more than 50%, have been detected as causing the leakage, this is defined as system leakage. This method involves a graded evaluation with the goal, even if not clear Detection of the leak site at least give the maintenance personnel hints.

To increase the accuracy of the analysis, several cycles can be considered. The sum of the multiple analyzes then gives more accurate information about the chamber or component causing the leakage or the chambers or components causing the leakage.

In a simpler version, a single timer may be provided for all chambers or components, each reset to zero during the occurrence of a leak and held there during the occurrence of the leakage. During this period, it is then checked which chambers or which components are active, that is to say are pressurized.

In a simpler embodiment of the method, for example, only the center distance or only the slope or its change can be evaluated. Per chamber or per component or per subsystem then only one counter is required. A further simplification of the method can still be done by completely dispensing with the determination of the axial spacing or the pitch and only increasing the counter of a chamber or a component by the value 1, if this chamber or component at least during a sub-period of a leakage interval was ventilated.

Claims (14)

1. Method for fault localisation and diagnosis in a fluidic system, wherein the fluidic volume flow of the overall system or at least a section thereof or a variable dependent thereon as measured variable is in each case recorded during an operating cycle and compared with stored references, and wherein in each case at the time of a variance or change in variance from the reference it is established at which component or components of the system an occurrence influencing the fluid consumption has taken place, so that this or these may then be identified as defective, wherein in the case of such a variance or change in variance and simultaneous occurrence of activities of several components (10-14) influencing fluid consumption a process of elimination is carried out in which, for consecutive activities involving at least one of these components (10-14), in each case in further checking steps an examination is made as to whether a variance or change in variance occurs, wherein in each of these further checking steps the components concerned are in each case excluded from further checking as not defective, if no variance or change in variance occurs, and wherein the stored references are fluid consumption reference curves formed from integrated volume flow values (Q) or guide value reference curves formed from integrated guide value factors (Q/P), wherein P is the measured operating pressure, and which are compared with corresponding measured variable curves, characterised in that in each case in further checking steps, in the event of further occurrence of variance or change in variance, the components which are not actively involved at this point in time are excluded, as non-defective, from further checking.
2. Method according to claim 1, characterised in that the volume flow values (Q) or guide value factors (Q/P) are compensated for on the basis of parameters, in particular dependent on temperature and/or fluid and/or humidity and/or the particle content of the fluid and/or on time or event for different states of operation.
3. Method according to claim 2, characterised in that several parameter-dependent fluid consumption reference curves or guide value reference curves are stored in a selection matrix.
4. Method according to claim 3, characterised in that the reference curves are acquired in a learning mode, in particular also in subsequent operation of the fluidic system.
5. Method according to any of the preceding claims characterised in that, before diagnosis for leakage, a comparison of curves is made for possible shifts in time wherein, in the event of a time shift exceeding a tolerance value, a switch is made to other stored reference curves for checking, or an error message and/or a stop triggers a further leakage diagnosis.
6. Method according to any of the preceding claims characterised in that, for leakage diagnosis, differential values or a differential curve (ΔK) is formed between the measured variable curve (Km) and the reference curve (Kref).
7. Method according to claim 6, characterised in that the differential curve (ΔK) is filtered depending on frequency and using an integrator, having in particular a phase shift of -90°.
8. Method according to claim 6 or 7, characterised in that a balancing function of the integral of the calculated differential values or the differential curve is formed, which best coincides with the calculated measuring points of the difference.
9. Method according to claim 8, characterised in that the balancing function is calculated according to the Gaussian principle of the least squares.
10. Method according to any of the preceding claims, characterised in that during the period of a variance or change in variance, a timer is set at a presettable value and a comparison is made to determine which component or components were active during at least a partial interval of this period.
11. Method according to claim 10, characterised in that each component (10-14) or each chamber of a component is assigned at least one counter, the reading of which is increased in each case by one counter value, if the component (10-14) or chamber is under pressure during at least a partial interval of the presence of the set value of the timer.
12. Method according to claim 11, characterised in that each component or each chamber of a component is assigned a gradient counter, the counter reading of which is then increased in each case only if the gradient of the balancing function increases at least by a presettable value or percentage during the presence of the set value of the timer.
13. Method according to claim 11 or 12, characterised in that each component or each chamber of a component is assigned an axial distance counter, the counter reading of which is then increased in each case only if the axial distance of the balancing function increases at least by a presettable value or percentage during the presence of the set value of the timer.
14. Method according to claim 12 and 13 characterised in that, at the end of an operating cycle, for each component or each chamber of a component, the counter readings of the gradient counter and the axial distance counter are added, wherein the highest overall counter reading or readings are judged to have the highest probability of leakage for the component or chamber of a component concerned.

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