Simple and safe: Focus on control technology

By OEM Update Editorial August 14, 2017 12:07 pm IST

Machine builders need appropriate, customised control concepts in order to meet rising demands on productivity and plant and machine availability. Interaction between the control functions for automation and safety are the key to success.

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. With intelligent, safe control architectures, users have the freedom they need for customised implementation of the safety requirements for design, operating and service concepts, as well as operator regulations.

The result is a specific requirement profile based on the machine type, application area and necessary safety concept – depending on the prescribed risk assessment. It may make sense, therefore, to operate existing machine control systems and safety control systems separately or even to merge them within one joint automation system. Not every concept is equally suitable for all machines.

Standardising safety
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 do 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.

Ease of use is one of the strengths of the configurable control systems PNOZmulti. Instead of carrying out the wiring manually, the user creates a safety program quickly and simply using the software tool PNOZmulti Configurator and the certified function blocks for safety-related functions that are stored within it. Compared with conventionally wired solutions, users save time and money on design, configuration, commissioning, diagnostics and maintenance.

The configurable control systems PNOZmulti are also powerful enough to assume complete machine control on smaller machines. As a result, the machine builder has no need for an additional control system and so can make savings in a range of areas, from hardware costs and space in the control cabinet to procurement and stock holding costs.

Safety and automation in one system

Distributing intelligence
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. Instead of a centralised control system, a user program distributed in runtime is made available to the user within a centralised project. 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.

For more details, visit www.pilz.in