WO2005111433A1

WO2005111433A1 - Method for fault localisation and diagnosis in a fluidic installation

Info

Publication number: WO2005111433A1
Application number: PCT/EP2004/004050
Authority: WO
Inventors: Jan Bredau; Jens Engelhardt
Original assignee: Festo Ag & Co
Priority date: 2004-04-16
Filing date: 2004-04-16
Publication date: 2005-11-24
Also published as: EP1747380A1; CN1973136A; ATE515638T1; CN1973136B; EP1747380B1; DK1747380T3

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

FESTO AG & Co, 73734 Esslingen Process for fault isolation and diagnosis in a fluidic system

description

The invention relates to a method for error limitation and diagnosis in a fluidic system, in particular in a pneumatic system, wherein the fluid consumption of at least one area of the system is recorded and, depending on the operating cycle, is compared with a corresponding stored reference consumption.

Such a method is known from DE 19628221 C2, which, however, serves to determine the operating positions of working devices of a pneumatic system, sensors, in particular position sensors, being dispensed with. Especially in the case of larger systems in which processes overlap, the position of one or in a specific work facility cannot be determined with certainty. If a malfunction or a leak occurs in one of the work facilities, it is no longer possible to make any clear statements and statements, and certainly not a particular work facility or component of the system that is no longer working properly can be determined.

It is an object of the present invention to provide a method of the type mentioned at the beginning for error limitation and diagnosis, by means of which the system and / or subsystem of the system is identified with simple means in which an error occurs, for example a malfunction or a leak.

This object is achieved according to the invention by a method with the features of claim 1.

The advantages of the method according to the invention for error limitation and diagnosis are, in particular, that only an additional volume flow sensor system is required in terms of hardware in the supply line of the system in order to measure the fluid consumption. In addition, the position, limit switch and actuator control signals, which are present anyway, are used in order to assign events determined during the fluid consumption measurement to specific systems or subsystems and thereby to be able to detect an error. Malfunctions in the respective system and / or subsystem as well as leaks can be identified and assigned to the respective system or subsystem. An error can thus be limited to a specific system within the plant or even to a specific subsystem. This is done very quickly while the system control sequence program is running.

Advantageous further developments and improvements of the method specified in claim 1 are possible through the measures listed in the subclaims.

The recorded fluid consumption and the stored reference consumption are expediently present as curve profiles, which are generated in particular by summing or integrating flow values. A particularly good error detection is achieved by forming difference values or difference curve profiles between fluid consumption and reference consumption, since these deviations can be identified particularly easily. To determine the faulty systems and / or subsystems at the time of the consumption deviation or the end of a constant consumption deviation, a time comparison is advantageously carried out with the sequence program of the system control. This makes it easy to use the sequence program to determine which system or subsystem was or is currently active. Alternatively or additionally, it can also be checked which control signals for systems or subsystems and / or sensor feedback occurred immediately before this point in time and to which systems or subsystems they were assigned. This also allows the faulty system or subsystem to be determined exactly.

Advantageously, the travel and / or positioning times of the systems and / or subsystems can also be checked using stored reference values before or during the fluid consumption diagnosis. If there are any deviations from the stored travel and / or positioning times, the faulty system can be inferred and - if this is done before the consumption diagnosis - the fluid consumption diagnosis itself can also be omitted if the faulty system or subsystem could already be determined by the preliminary process.

In the case of large fluidic systems in particular, it can also prove to be advantageous if the fluid consumption in several areas of the fluidic system is recorded and diagnosed by means of several flow measuring devices. This increases the diagnostic certainty and also the uniqueness of the error detection, especially if several systems are moving at the same time. For example, safety-relevant areas of the system can be monitored additionally or separately in this way.

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 recorded and can be used for the parameter-dependent correction of the fluid consumption.

Embodiments of the invention are shown in the drawing and explained in more detail in the following description. Show it:

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

2 shows a portion of the diagnostic level for difference formation,

3 shows a more extensive pneumatic system which is divided into three sections and with a flow meter being assigned to each section,

4 to 6 air consumption diagrams for explaining various diagnostic results.

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

The pneumatic system consists of five subsystems 10-14, each of which can be actuators such as valves, cylinders, linear drives and the like, as well as combinations thereof. These subsystems 10-14 are fed by a pressure source 15, a flow meter 17 for measuring the flow rate in a common feed line 16. ses or the volume flow is arranged. The air consumption is obtained by summing or integrating the measured values for the flow or volume flow or mass flow. The subsystems 11, 12 on the one hand and the subsystems 13, 14 on the other hand each form a system with a common supply line.

An electronic control device 18 is used to specify the sequence process of the system and is electrically connected to the subsystems 10-14. Preserve subsystems 10-14

Control signals from the electronic control device 18 and send sensor signals back to it. Such sensor signals are, for example, position signals, limit switch signals, pressure signals and the like.

The flow meter 17 is connected to an electronic diagnostic device 19, to which the signals of a temperature sensor 20 and a pressure sensor 21 for measuring the temperature and the pressure in the feed line 16 are additionally fed. Furthermore, the diagnostic device 19 has access to the flow chart of the electronic control device 18. The diagnostic results are fed to a display 22, whereby these diagnostic results can of course also be saved, printed out or transmitted to a central office via lines or wirelessly.

The diagnostic device 19 can of course also be integrated in the electronic control device 18, which can contain, for example, a microcontroller for executing the drain program and possibly for diagnosis.

According to FIG. 2, the diagnostic device 19 shown only partially there contains an execution memory 23 in which the pneumatic air consumption during the execution of the sequence program of the pneumatic system is stored in the form of a reference air consumption curve. As already explained, this reference curve can be formed, for example, by adding or integrating reference flow values during the sequence program. For example, it can be saved in a learning mode. In a downstream subtraction stage 24, to which the sensor signals of the flow meter 17 are also fed, a difference curve profile ΔL is formed as the difference between the air consumption curve L formed from the measured values and the reference curve L _ref . The difference curve profile ΔL and the air consumption curve L and the reference air consumption curve L _ref can then be shown on the display 22, as will be explained in more detail in connection with FIGS. 4 to 6.

FIG. 3 shows an expanded version of the exemplary embodiment according to FIG. 1. In addition to the subsystems 10-14, the pressure source 15 supplies further 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. The three partial areas of the system can thus be diagnosed independently of one another by means of the three flow meters 17, 33, 34. 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 provided in accordance with FIG. 1. A common control device and a common diagnostic device 19 can be provided as two separate units or as a single integrated unit. The procedure for fault isolation and diagnosis will now be explained below using the pneumatic system described.

4 shows the case that the reference air consumption curve L _ref coincides with the measured air consumption curve L by the time t1, that is to say the difference or the difference curve profile remains at the zero value. An error occurs at time t1, for example due to the delayed movement of the actuator in one of the subsystems 10-14, which could be caused, for example, by briefly jamming an axis. This shifts and extends the entire cycle by the time? T of the delayed movement, the air consumption at the end of the cycle matching that of the reference air consumption curve L _ref . This indicates that no leakage has occurred. Exactly the time t1 from which the deviation has occurred can be detected from the difference curve profile. According to FIG. 1, the sequence program is supplied to the diagnostic device 19 by the electronic control device 18. 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 this subsystem. The assignment of the respectively active subsystems according to the sequence program to the air consumption curve or to the reference air consumption curve can take place graphically on the display 22 or can be determined by a comparison program in the diagnosis device 19. The subsystem active at the time of the deviation can then also be displayed graphically.

FIG. 5 shows the case that during the entire sequence program, that is to say during the entire cycle of the system, the difference ΔL down to a small range between t2 and t3 increases continuously, 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 shows the case of a leak in an actuator of a subsystem. This is partly pressurized during the cycle and partly pressureless. In the depressurized state, there is consequently an air consumption difference of 0 or an air consumption difference that no longer increases during this time interval. A comparison with the sequence program now determines which actuator was depressurized during this time interval and pressurized during the rest of the time. The leakage can thus be limited to this actuator.

In the diagram shown in FIG. 6, an air consumption difference to the reference air consumption curve L _ref occurs in a time interval from time t4 and again in a time interval from 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 time t4 and t5. As a result, these are recognized as faulty, which can also be the same actuator or the same subsystem that comes into action twice during the sequence program. After the first deviation from time t4, a new reference value for air consumption is formed, which results from the old reference value (0) and the new offset in air consumption. In the following cycle, the measured air consumption is checked for deviations using the new reference value. This means that if the same subsystem or another subsystem fails again, the error can be determined again. The barriers for a permissible change in air consumption can be fixed or can be kept variable in accordance with the current air consumption values. On the one hand, it is possible to cycle in the area of a small air consumption begin to choose very narrow bounds to get a very high sensitivity, and on the other hand, in the area of high air consumption at the end of the cycle, choose rough bounds 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 measurement values or air consumption values are subjected to a temperature correction and a pressure correction, the corresponding measurement variables being 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 any compensation is dispensed with, in particular even if the pressure and temperature influences to be expected are not very great.

Since only an additional flow meter is required for the method according to the invention with regard to the hardware, already installed systems can also be retrofitted in a simple manner. The diagnostic method according to the invention can then be implemented by adding software.

Claims

Expectations

1. A method for error limitation and diagnosis in a fluidic system, wherein the fluid consumption (L) of at least one area of the system is recorded and compared with the operating cycle depending on a corresponding stored reference consumption (L _ref ), at the time of a consumption deviation (ΔL) or in the event of a constant consumption deviation at the time of a termination of the consumption deviation, it is determined in which system and / or subsystem (10-14, 25-32) of the system a process affecting fluid consumption has taken place at that time, and wherein this system and / or subsystem (10-14, 25-32), which means that it is recognized as faulty.

2. The method according to claim 1, characterized in that the detected fluid consumption (L) and the stored reference consumption (L _ref ) are present as curves which are generated in particular by summing or integrating flow values.

3. The method according to claim 1 or 2, characterized in that the difference values (ΔL) or difference curves between fluid consumption (L) and reference consumption (L _ref ) are formed.

4. The method according to any one of the preceding claims, characterized in that for the detection of the defective systems and / or subsystems (10-14, 25-32) for

When the consumption deviation (ΔL) or the end of a constant consumption deviation, a time comparison is carried out with the sequence program of the system control (18).

5. The method according to any one of the preceding claims, characterized in that the control signals for systems or subsystems and / or sensor feedback is checked to determine the faulty systems and / or subsystems at the time of the consumption deviation or the end of a constant consumption deviation occurred immediately before this point in time and to which systems and / or subsystems they were assigned.

6. The method according to any one of the preceding claims, characterized in that the travel and / or positioning times of the systems and / or subsystems are additionally checked before or during the consumption diagnosis on the basis of stored reference values.

7. The method according to claim 6, characterized in that the consumption diagnosis is omitted if errors occur in the travel and / or positioning times.

8. The method according to any one of the preceding claims, characterized in that the fluid consumption of several areas of the fluidic system by means of several flow measuring devices (17, 33, 34) is detected and diagnosed.

9. The method according to any one of the preceding claims, characterized in that the temperature and / or the pressure of the fluid is additionally detected.

10. The method according to claim 9, characterized in that the measured fluid consumption (L) is corrected as a function of the temperature and / or the pressure.