The automation pyramid, going forward systematically
Particularly in complex systems, there is never a single level on which a process and its intermediate steps take place. In most cases, this process takes place on several levels, so that smooth communication between the components is required. This is made possible by the so-called bus systems. A system bus is the bundling of these buses or data rails that permit the main processor (CPU – Central Processing Unit) to function with the remaining devices inside the microcomputer. Coming back to the subject of different levels, various patterns can be noticed, which illustrate how the data exchange within a pyramid and systems takes place. In particular, one constant can be found. At the same time, this also illustrates the nature of the problem: Between the different levels occurring in the automation pyramid, the rule is that the transmission speed decreases with higher levels, however the quantity of the data to be transmitted always increases. The following division is performed for the different levels:
- Field level – this is also called the sensor or actuator level. It is at the lowest position in the control process and as such, the lowest level of the automation pyramid. At this point, the control of the processes relating to production and manufacturing takes place. This can be done via the corresponding sensors and actuators that give the name to the level. In the field level, data are collected which relate to the process, e.g. the fill level, the temperature, the rotation speed and the pressure. However, data that is relevant for the safety and the quality of the process also are processed in addition to these process data. As soon as the data arrives at the lowest level of the automation pyramid, it is then read at this point and processed. However, the subsequent data exchange does not take place within the level, but is fed to the second level, the control and process level. This connection within the automation pyramid is reached via the field bus, which is normally a PROFIBUS, an AS-Interface, a CANopen or a DeviceNet.
- Control and/or process level – this is the second level within the automation pyramid. Here, the different task areas typically are handled via PLCs, i.e. controls with programmable storage, or in addition, a CNC computer. In addition to the collection, subsequent preparation and finally, the processing of the data from the field level, the tasks areas handled on the second level also include the general management of the control groups and regulation groups, as well as the execution of the corresponding processes from these groups and the forwarding of selected data to the higher level, the system level. Further, the collected and processed data also are visualized within the control and processor level. In a way that is different from the first level, the exchanging of data here does not take place between two levels, but within this part of the automation pyramid. Just as is the case with the field bus, the same control elements are found in the sensor level as well as the industrial Ethernet.
- System or cell level – this is the level in which the functions of monitoring, regulation control, and control take place simultaneously for several processes. Here, tasks similar to those in the control level are executed, but in a more qualified and comprehensive way. Here the specified data are transferred to the control level and as such, there is central visualization of the received data. Moreover, several control and regulation groups are managed. In addition to the PLC, a PC is typical of the equipment that is used. The data exchange and the field bus that is used are the same as in the second level of the automation pyramid.
- Control and operation level – these two levels are mainly found in large production set ups and in conjunction with plant and operating facilities. Here, these levels ensure the control function and detailed planning. In a way that is different from the components of the automation pyramid that have already been mentioned, here the field buses and their systems hardly have any relevance. As such, the industrial Ethernet is suitable for use.
The conceptual history of the automation pyramid
The concept of the automation pyramid has been known in the field of automation technology already since the 80s. However, at that time this construct still covered three subordinate levels: the “I/O level”, “automation” and “man-machine interface”. The term CIM pyramid was used for the upper levels. Although this term still is encountered in automation technology in some cases, the more succinct term became more widespread through the increased use of modern techniques in production and manufacturing plants. The function for which the automation pyramid was developed is the classification of systems from control technology. Furthermore, thanks to the division of the processes into different levels, this form of industrial communication facilitates the visualization of industrial manufacturing and its techniques. As such, this model can demonstrate the flowing boundaries within a production department. Here, a breakdown is made into analog data transmission and data processing, as well as the digital pendant.