EP1747380B1 - Method for fault localisation and diagnosis in a fluidic installation - Google Patents

Abstract

The invention relates to a method for fault localisation and diagnosis in a fluidic installation. According to said method, the fluid consumption in at least one region of the installation is recorded, and compared with a corresponding stored reference consumption according to the operating cycle. Respectively at the time of a variation in consumption or at the end of a continuous variation in consumption, the system and/or subsystem (10-14) of the installation, in which a process influencing the fluid consumption has taken place at this point, is determined, and said system and/or subsystem (10-14) can thus be identified as faulty.

Description

The invention relates to a method for limiting errors and diagnosis on a fluidic system, in particular on a pneumatic system, having the features of the preamble of claim 1.

From the DE 100 52 664 A For example, such a method for fault isolation and diagnosis at a fluidic system is known in which the fluid consumption is compared with a reference air consumption curve. Especially with complex systems, which consist of a large number of individual components, there is a risk that faulty components are not reliably detected.

From the US-A-5,893,047 A similar method is known in which it is checked which control signals for systems or subsystems and / or sensor messages occurred immediately before the time of an error message and which systems and / or subsystems they were assigned. Although this improves the detection of defective components, it is difficult to distinguish between leakage errors and other sources of error.

From the DE 19628221 C2 a method is known, however, which serves for the determination of operating positions of working facilities of a pneumatic system, wherein sensors, in particular position sensors, is dispensed with. Especially with larger plants, where operations overlap, can not be sure of the position of one or in closed to a specific work organization. If a malfunction or a leak occurs at one of the working facilities, then no clear statements and findings are possible any more, and certainly not a particular work equipment or component of the system can be determined, which no longer works properly.

The object of the present invention is to provide a method of the type mentioned above for fault isolation and diagnosis, through which the system and / or subsystem of the system can be easily detected by simple means in which an error occurs, so for example a malfunction or a leak.

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

The advantages of the method according to the invention for fault isolation and diagnosis are, in particular, that in terms of hardware, only an additional volume flow sensor system in the supply line of the system is required in order to measure the fluid consumption. Incidentally, the already existing position, limit switch and Aktorsteuersignale be used to allocate events detected in the fluid consumption measurement certain systems or subsystems and thereby detect a fault. Both malfunctions in the respective system and / or subsystem as well as leaks can be detected and assigned to the respective system or subsystem. An error can be limited to a specific system within the plant or even to a specific subsystem. This is done very quickly during the sequence program of the system control.

To determine the error-prone systems and / or subsystems at the time of consumption deviation or termination of a constant consumption deviation, a temporal comparison is advantageously carried out with the sequence program of the system control. This can easily be determined by the sequence program, which system or subsystem was or is active at the specified time. In addition, it checks which control signals for systems or subsystems and / or sensor feedback occurred immediately before this time and to which systems or subsystems they were assigned. As a result, the faulty system or subsystem can be determined more accurately.

In an advantageous manner, the travel and / or positioning times of the systems and / or subsystems are additionally checked based on stored reference values before or during the fluid consumption diagnosis. If deviations from the stored traversing and / or positioning times are detected, then it can be concluded that the faulty system and - if this is done before the consumption diagnosis - the fluid consumption diagnosis itself can also be omitted if the faulty system or subsystem already could be determined by the preliminary proceedings.

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

The detected fluid consumption and the stored reference consumption are expediently present as curves, which are generated in particular by summation or integration of flow values. A particularly good error detection is achieved in that difference values or difference curves between fluid consumption and reference consumption are formed, since these deviations can be detected particularly easily.

Particularly in the case of large fluidic systems, it can also prove advantageous if the fluid consumption is detected and diagnosed in several areas of the fluidic system by means of a plurality of flowmeter devices. This increases the diagnostic reliability and also the uniqueness of the error detection, in particular if several systems are moving at the same time. For example, more security-relevant Areas of the system can be monitored in this way additionally or separately.

Since the flow or volume flow and thus also the fluid consumption depends not least on the pressure and the temperature, these parameters or at least one of these parameters are expediently detected and can be used for parameter-dependent correction of the fluid consumption.

Fig. 1

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

Fig. 2

einen Teilbereich der Diagnosestufe zur Differenz- bildung,

Fig. 3

eine umfangreichere pneumatische Anlage, die in drei Teilbereiche aufgeteilt ist und wobei jedem Teilbereich ein Durchflussmesser zugeordnet ist,

Fig. 4 bis 6

Luftverbrauchsdiagramme zur Erläuterung verschiede- ner Diagnoseergebnisse.

Embodiments of the invention are illustrated in the drawings 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 subsection of the diagnostic step for difference formation,

Fig. 3

a more extensive pneumatic system, which is divided into three sections and wherein each section is assigned a flow meter,

4 to 6

Air consumption diagrams to explain different diagnostic results.

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, which may each be actuators, such as valves, cylinders, linear actuators, and the like, as well as combinations thereof. 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 volume flow is arranged. By summing or integrating the measured values for the flow or volume flow or mass flow, the air consumption is obtained. 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 flow of the system and is electrically connected to the subsystems 10-14. 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 and the like.

The flowmeter 17 is connected to an electronic diagnostic device 19, which in addition the signals of a temperature sensor 20 and a pressure sensor 21 for measuring the temperature and the pressure in the supply line 16 are supplied. Furthermore, the diagnostic device 19 has access to the sequence program of the electronic control device 18. The diagnostic results are supplied to a display 22, these diagnostic results can of course also be stored, printed or transmitted to a control center via lines or wirelessly.

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.

According to Fig. 2 includes there only partially shown diagnostic device 19 a drain memory 23, in which the pneumatic Air consumption during execution of the sequence program of the pneumatic system is stored in the form of a reference air consumption curve. As already stated, this reference curve can be formed, for example, by addition or integration of reference flow values during the sequence program. It can be stored, for example, in a learning mode. In a downstream subtraction stage 24, to which the sensor signals of the flow meter 17 are also supplied, a difference curve ΔL is formed as the difference between the air consumption curve L formed from the measured values and the reference curve L _ref . On the display 22 then the difference curve .DELTA.L and the air consumption curve L and the reference air consumption curve L _{ref can be} reproduced, as in connection with the 4 to 6 will be explained in more detail.

Fig. 3 represents an expanded version of the embodiment according to Fig. 1 In addition to the subsystems 10-14, the pressure source 15 supplies additional subsystems 25-32 here. The additional subsystems 25-32 are divided into two groups, each of which is supplied with compressed air via its own flow meter 33, 34. By means of the three flow meters 17, 33, 34 can thus be diagnosed independently of each other, the three sections of the system. The electronic control device 18, the diagnostic device 19 and corresponding temperature sensors and pressure sensors are not shown for the sake of simplicity, but are of course also corresponding Fig. 1 intended. In this case, a common control device and a common diagnostic device 19 may be provided as two separate units or as a single integrated unit.

The procedure for fault isolation and diagnosis will now be explained below with reference to the described pneumatic system.

In Fig. 4 In the case illustrated, the reference air consumption curve L _ref agrees with the measured air consumption curve L until the time t1, that is, the difference or the difference curve remains at the zero value. At time t1, an error occurs, for example, due to the delayed movement of the actuator in one of the subsystems 10-14, which could be caused, for example, by a momentary jamming of an axle. As a result, the entire cycle shifts and extends by the time? T of the delayed movement, the air consumption at the end of the cycle coinciding with that of the reference air consumption curve L _ref . This indicates that, incidentally, no leakage has occurred. From the difference curve, exactly the time t1 can be detected, from which the deviation has occurred. The diagnostic device 19 is according to Fig. 1 supplied by the electronic control device 18, the sequence program. From this it can be seen which actuator or which subsystem was active at time t1. The error can thus be limited to this actuator or these subsystems. The allocation of the respective active subsystems according to the sequence of operation for the air consumption curve or the reference air consumption curve can be graphically on the display 22 or determined by a comparison program in the diagnostic device 19. The subsystem active at the time of the deviation can then also be displayed graphically.

In Fig. 5 the case is shown that during the entire sequence program, ie during the entire cycle of the system, the difference .DELTA.L to a small range between t2 and t3 is constantly increasing, so that at the end of the cycle the total air consumption L is significantly greater than the reference air consumption L _ref . The curve represents the case of a leak at an actuator of a subsystem. This is partly pressurized during the cycle and partly depressurized. In the depressurized state, consequently, there is an air consumption difference of 0 or an air consumption difference no longer increasing during this time interval. By comparison with the sequence program is now determined which actuator was pressureless during this time interval and during the remaining time pressurized. The leakage can thus be limited to this actuator.

At the in Fig. 6 shown diagram occurs in a time interval from the time t4 on an air consumption difference to the reference air consumption curve L _ref on and again in a time interval from the time t5. Again, it must be determined by comparison with the sequence program, which actuator or which subsystem were active in these two time intervals from the time t4 and t5. These are thereby identified as being defective, which may also be the same actor or subsystem that occurs twice during the sequence program. After the first deviation from time t4, a new reference value for the air consumption is calculated, which results from the old reference value (0) and the new offset in the air consumption. In the following cycle, the measured air consumption is checked for deviations with the new reference value. Thus, in the event of a renewed error of the same subsystem or of another subsystem, the error can be determined again. The limits for a permissible air consumption change can be fixed or kept variable according to the current air consumption values. So it is possible on the one hand, in the range of a small air consumption at the beginning of the cycle To choose very narrow barriers to get a very high sensitivity, and on the other hand in the area of high air consumption at the end of the cycle to set rough barriers to be robust against fluctuation and measurement errors.

In order to avoid deviations from the reference air consumption curve L _ref due to temperature influences and pressure influences, the flow measured values or air consumption values are subjected to a temperature correction and a pressure correction, wherein the corresponding measured variables are made available by the temperature sensor 20 and the pressure sensor 21. In a simpler embodiment, only a temperature compensation or only a pressure compensation can be provided, or it is dispensed with any compensation, especially if the expected pressure and temperature influences are not very large.

Since the method according to the invention requires only an additional flow meter with respect to the hardware, already installed systems can be easily retrofitted. The diagnostic method according to the invention can then be realized by software supplementation.

Claims (7)

1. Method for fault localisation and diagnosis on a fluidic system, wherein the fluid consumption (L) of at least one region of the system is detected and compared in an operating cycle-dependent manner to a corresponding stored reference consumption (L_ref), wherein, in order to detect the faulty system(s) and/or subsystem(s) (10-14, 25-32), a time comparison is carried out at the time of a consumption deviation (ΔL) or at the end of a continuous consumption deviation with a reference air consumption curve which is stored in a sequence memory (23) and which includes the pneumatic air consumption during the execution of the sequence programme of the system control (18) of the pneumatic system, characterised in that a check is performed to determine which control signals for systems or subsystems and/or which feedbacks have occurred immediately before this point in time and to which systems and/or subsystems they were assigned, in order to recognise this or these as faulty, and in that, in addition, before or during the consumption diagnosis the traversing and/or positioning times of the systems and/or subsystems are checked against stored reference values.
2. Method according to claim 1, characterised in that the consumption diagnosis is omitted if there are any faults in the traversing and/or positioning times.
3. Method according to claim 2, characterised in that the temperature and/or the pressure of the fluid is/are detected in addition.
4. Method according to claim 3, characterised in that the measured air consumption (L) is corrected in dependence on temperature and/or pressure.
5. Method according to any of the preceding claims, characterised in that the detected air consumption (L) and the stored reference consumption (L_ref) are present as curve traces which are in particular generated by the summation or integration of flow values.
6. Method according to any of the preceding claims, characterised in that the differential values (ΔL) or differential curve traces are formed between fluid consumption (L) and reference consumption (L_ref).
7. Method according to any of the preceding claims, characterised in that the fluid consumption of several regions of the fluidic system is detected and diagnosed by means of several flow measurement devices (17, 33, 34).

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