Simpler, more flexible, more productive, more efficient, as the demands on plant and machinery rise, so too does the level of automation. And control technology has a key role. It is the playmaker; it processes the digital and analogue signals from the sensors and input devices, sends them to actuators, drives and control devices and keeps the plant running. The processes required to do this are becoming increasingly complex. The number of relationships within a machine is rising and the level of networking is also growing. This creates additional challenges in terms of handling. At the same time, in many sectors, people are moving ever closer to the process, to fit and set up machinery for example. Where man-machine interaction is as close as possible, it can help to improve plant availability and therefore increase productivity. Accordingly, safe automation is becoming increasingly important within the whole automation concept.
The determining factor when selecting the appropriate safety system is the plant’s function range. For example, by their very nature, standalone machines have fewer safety functions than interlinked machines and does not need an overriding safety function, such as a safety area shutdown. Configurable control systems are particularly suitable for this type of application. One classic application area is series machine building. In this case, manufacturers are often forced to use prescribed or country-specific machine control systems. Slight changes are continually needed to the automation concept. Openness is, therefore, essential.
As the Pilz configurable control systems PNOZmulti support all common fieldbus and Ethernet-based communication systems, for example, machine operators can choose the operational control system that best suits their individual needs and don’t need to worry about how safety is connected. Both manufacturers and users benefit from this standardisation of safety, in terms of troubleshooting, machine design and training.
Safety and automation in one system
Dynamic safety concepts, such as different operating modes or torque monitoring based on the position of one or more axes, will continue to find their way into the control architecture in future. Increasingly, that requires more complex relationships with the individual elements in the overall process chain. Machine data – whether for automation or safety – must be capable of being processed together.
The trend is for automation and safety functions to use a common control architecture – or even to functionally merge the two areas that have previously always been separate. Hybrid designs are catching on, especially in distributed systems to minimise cabling complexity and interface problems, for example.
Machine tools are one example. Safe CNC or motion controllers, for example, record safety-related information such as linear speed, rotational speed or standstill at the various axes directly via their integrated encoder systems, passing the information on to safety control systems for safe evaluation. In this case, they not only process local safety functions, but also record and forward signals, for monitoring end positions for example. Just one common periphery system is needed for the important control-related process signals as automation I/Os and the I/Os for the safety functions. Thanks to the openness of the safety control system, additional encoder systems, interface problems or adapter solutions are consigned to the past. Here, Pilz offers the control systems PSSuniversal multi.
Both PSSuniversal multi and PSSuniversal PLC are control systems in the automation system PSS 4000 from Pilz. The central idea of PSS 4000 is to merge automation and safety. Process or control data, failsafe data and diagnostic information are exchanged and synchronised via the Ethernet-based SafetyNET p. For the control function, therefore, it makes no difference where the respective program section is processed. All network subscribers are configured, programmed and diagnosed this way. So for all control tasks, the user maintains a centralised view of distributed systems. If the intelligence is distributed in the machine components, the benefits can be seen in greater availability due to local error reactions and higher productivity as a result of shorter reaction times across the whole system. Dividing the intelligence into smaller machine components also leads to improved scalability.
Such multi-master automation structures result in largely standalone cell control systems, which can interact within the network. So PSS 4000 enables the mechatronic approach to be transferred to the control level, which is a key step towards Industry 4.0. Plants can be broken down into manageable, independently functioning units. As a result, the cost of engineering, commissioning and maintenance is significantly reduced. If plants are thought out and designed mechatronically, the system and hardware can be developed in parallel, for example. To date, software development is only started once the machine specification has been established. Subsequent changes or expansions to functions are very difficult retrospectively because the program as it stands accesses the hardware directly. The degree of standardisation of elements of plant and machinery also rises, allowing them to be adapted rapidly and flexibly to changing customer requirements.