Patent Application
20110314258
The embodiments of the present invention, as disclosed, concern a decentralized, autonomous sequence control and an operating method.
In known programmable logic controllers (PLC), the input and output modules, respectively, are designed for rudimentary functions such as, for example, analog-digital conversion, and amplification of applied analog signals, among others.
The entire intelligence is concentrated in a central data processing unit (CPU). The data processing unit reads in the raw data of the input modules, processes the raw data, and makes prepared data available to the output modules.
Disadvantages may result from the centralization of the control in the central data processing unit, such as:
Another widespread concept of the data processing of automation is shown by the disclosure of German patent application DE 10321652 A1. As disclosed in this document, a central controller transmits functions via a communication device to one or more decentralized input/output modules, which send back their status to the superordinate control. The communication device is embodied as a field bus in most cases. The input/output modules are autonomous in that they independently perform functions specific for their tasks based on their programs. These functions can be configured or reprogrammed according to the prior art. In the cited disclosure, these modules are measuring modules such as have been available for years. In automation systems, input/output modules with autonomous functions connected via communication devices have been standard for decades in the form of thermostats or as servo amplifiers.
These modules are independent devices with their own supply connection, communication connection, input/output connections, and mounting means in a machine or system, for example, by means of rail connection according to DIN EN50022.
Disadvantages may result from the distribution of individual functions of a controller via field buses to decentralized data processing units (input and output modules, respectively), such as:
Accordingly, a purpose of this invention is to further develop a programmable logic controller for a processing plant such that strain on the central data processing unit is relieved and the computing operations previously carried out by the central data processing unit are transferred to the programmable logic controller and there, in particular, to the input/output modules.
Accordingly, the communication demand between the central superordinate data processing unit and the grouped input/output modules connected to one another via an internal bus is reduced. This therefore results in a reduced dependency or lower power requirements on the communication device between the connected grouped input/output modules and the superordinate data processing unit. The communication device can be the internal system bus, via which the input/output modules are connected, as well as a field bus.
A feature of the disclosed embodiments of the present invention is that the intelligence of a central data processing unit is shifted to intelligent input and output modules. All of the input and output modules respectively are equipped with a low cost processor such as, for example, a DSP (digital signal processor).
With an input module, for example, the DSP reads in the raw data and processes them accordingly into function blocks of programmed partial applications, which thus do not need to be further processed in the central data processing unit. In the partial applications, direct or indirect physical variables are measured, monitored, regulated, and controlled according to a programmed sequence and thus are a part of the automation of the processes of a machine or installation. The shift of the “intelligence” from the central data processing unit to intelligent input and output modules, respectively, results in the following advantages:
The decentralized sequence control takes place through the creation of a complete application in a development environment, wherein this application is divided up by the development environment into partial applications. This is initially administered in the start-up phase of the superordinate sequence control of the central data processing unit and then fed as an individual application via an internal system bus to the individual input/output modules which perform these applications independently due to the intelligence installed there.
A decentralized autonomous sequence control is thus formed in that individual input/output modules are part of a decentralized automation system and communicate only among themselves. Only an internal communication is maintained to fulfill the sequence control, so that the signals of the central, superordinate data processing unit are no longer important. Only a superordinate data exchange is maintained with this data processing unit, that is, monitoring functions or status changes are monitored and, if necessary, changed without, as in the prior art, this central data processing unit having a central sequence control that monitors each and every one of the downstream modules.
The inventive idea of now accommodating the autonomous controller in an automation system in a decentralized manner results in the advantage that now the modules have independent intelligence and, if the central data processing unit or the interface fails, an operation of the individual modules is nevertheless possible.
If, for example, a sequence control of this type is used in a wind power plant, in the prior art there typically was the disadvantage that, if the central data processing unit failed, all of the downstream modules were switched off and had to go into a safe mode. This led to an emergency stop, which applied all of the brakes of the wind turbine and thus caused a very high mechanical strain and possible damage.
This is avoided in the decentralized autonomous intelligence of the decentralized automation system in accordance with this invention because, despite the failure of the central data processing unit, this decentralized automation system can now be brought into a safe mode slowly and in a controlled manner without a sudden shutdown taking place. The availability of the entire installation is thus increased and much higher safety requirements can be met, since the failure of the central data processing unit does not lead to the failure of the downstream decentralized automation systems.
In one embodiment, based on the solution described above, the internal system bus can be realized redundantly. This can be used to increase the availability and the safety of the control system.
In a further embodiment the decentralized input and output modules respectively can be composed only of a data processing unit that has no connection to a superordinate control and “only” executes programs in a decentralized manner.
The invention, in an embodiment, can also be restricted to only the region of the PLC.
Examples of the invention are further described below by means of the subsequent detailed description of advantageous embodiments, reference being made to the accompanying drawing, wherein:
FIG. A is a block diagram of a sequence control according to the prior art;
FIG. B is a block diagram of a sequence control according to the prior art, modified compared to FIG. A;
FIGS. A and B show a sequence control according to the prior art.
Sequence program 9 executes in decentralized central data processing unit (CPU) 1, which sequence program processes input data 3a via input process image 2a and, after their processing, the data are output as output data 3b via output process image 2b. Input data 3a and output data 3b are connected to the communication bus, which can be embodied as internal system bus 4, for example. A number of external modules 6 are connected to this system bus, wherein in the exemplary embodiment shown according to the prior art, external module 6 can have its own microprocessor 7 which, for example, drives regulator 12.
Microprocessor 7, via module data bus 5, exchanges desired data, actual data, and status data with central data processing unit, CPU 1, via internal system bus 4. The connection to the sensors and actuators of the system to be regulated, for example, a drive, takes place via sensor/actuator interface 8.
A block diagram of this type is shown in more detail in FIG. B, where it is discernible that the data transmitted at the communication bus are returned as actual values via data path 10 to CPU 1, and the CPU, in turn, generates desired values that are fed into module 6 via data path 11.
It is percievable that this module, with its installed sequence control, activates motor 13, the movement of which is detected by measured-value transmitter 14.
The above-referenced representation reveals a disadvantage of the prior art, because it is apparent that CPU 1 takes over all of the control functions, and downstream external module 6 performs the control commands of the central data processing unit only as a slave. However, this means that there is the drawback that, if CPU 1 fails, external module 6 suddenly enters an emergency mode and stops, whereby damage can be caused to motor 13 or to the system moved by the motor.
In accordance with an exemplary embodiment of the present invention, as shown in
The partial applications 20-23 are loaded by development environment 17, for example, via programming interface 24, into the now “slimmed down” central data or ADMIN data processing unit (CPU) 15. This now has only a superordinate sequence control or operating system 16, which is considerably simplified compared to the sequence control of the general data processing unit 1, according to the prior art shown in FIGS. A and B.
The individual applications 20-23 are now stored in memory in this ADMIN data processing unit 15 and loaded into the individual input/output modules 31, 32, 33 in the arrow directions 27-29, for example, via internal system bus 25.
It is now important that each input/output module 31-33 is independently executable, as is shown in
The important thing is that all of the input/output modules 31-33 are arranged in a decentralized automation system 34, so that these input/output modules maintain an internal exchange of communication 35-38 only among themselves, without ADMIN data processing unit 15 having to be switched on for this purpose. This unit has only superordinate administration functions and operates as a decentralized CPU, so that decentralized automation system 34, with input/output modules 31-33, is independently executable. It thus operates autonomously.
An exemplary embodiment of this type according to
All data are exchanged via internal system bus 25. The exchange of information between the partial applications is carried out independently via the internal system bus according to the information exchange demand of the partial applications. These communication exchanges 35-38 were explained based on
While a plurality of input and output modules is present, only a few are described. For example, input module 31 is embodied as a digital input (DI), which is controlled by a switch as an input quantity 43, and two application programs execute in this input/output module 31, namely, a pure signal filter and a so-called safe input.
Arrows 38 running horizontally between, for example, DI 31 and DI 32, show that a communication exchange between adjacent modules takes place, which likewise is embodied as a digital input. DI 32 also contains a digital filter, the validity of which is checked with the filter of the first input and output module 31 and wherein, in turn, a switch is provided as input quantity 44.
Two different partial applications execute here, too, wherein in the third input/output module 33, a partial application executes, which generates a specific position indicator command when there is an emergency situation. Likewise with the other partial application, the valid position of a rotary encoder is detected and verified with the adjacent module via communication exchange 38. Input quantity 45 is hereby embodied as a rotary encoder.
The representation according to
Individual function blocks 40, 41, 42 are part of decentralized automation system 34. In the exemplary embodiment shown, function block 40, with the input/output modules shown, is used for monitoring. Function block 41, with other input/output modules, can be used for the positioning of an azimuth position of a wind turbine, for example, and function block 42 could be used to brake the rotation of a wind turbine nacelle.
It is further shown in
This is therefore a decentralized autonomous sequence control, which executes in decentralized automation system 34 independently of a failure of ADMIN data processing unit 15.
| Number | Date | Country | Kind |
|---|---|---|---|
| A 1992/2009 | Dec 2009 | AT | national |
