Using safety control systems to achieve safe control technology: Safe control technology

The model of safety technology as a pure “monitoring function” is changing drastically: Safety technology may have been almost exclusively associated with emergency off/emergency stop, light curtains and interlocks for a long time, but it would now be unthinkable not to regard the issue of safety on drives, for example. Other areas will include safe pneumatics and hydraulics. Applications will emerge from areas which are not yet the focus of our attention, but one thing is clear: Safety is an integral part of the overall plant and machine function, so it must
be considered appropriately, right from the start. In simple language, safe control technology means: Make the control function safe! Safe control technology becomes reality when safety enjoys the same mechanisms, the same handling and the same flexibility as the standard section, at all levels of automation technology.

This does not mean that safety and standard functions have to be combined inside one device. What's important is that they work together to process tasks as a system, without impeding each other. Each device, each control system, should do what it does best. The system's backbone is an extremely powerful bus system, which manages data traffic in the background. The result of this technological development is a system which uses the intrinsic benefits of technology control systems. For example, it makes no sense for a safety control system to have to carry out motion functions, when that's a specific task of the motion technology control system.

Safety and standard control systems combined in one system.

Ultimately however, this means that all the control systems have to be able to share access to the same data, without the user being required to organize it this way. The system must perform this task automatically in the background. In future, even the tools must have the same look and feel, plus standardized handling. Whether it's motion, control or visualization: Handling of the various functions and tasks must be seamless.

Using safety control systems to achieve safe control technology: An overview

In which direction is safety technology developing? Which control systems provide the highest user benefits? How will the various disciplines of safety, control, motion, CNC and visualization work together in future? Will it be possible to implement economical solutions, despite the increasing complexity? Even in future there will be a number of different approaches to take to resolve requirements. One potential approach is to modularize plant and machinery into functional units. This is already happening today, albeit primarily for the mechanical part of plant and machinery. This approach has only partially been used in control technology as yet.

Whether the issue is safety-related or automation functions: The demands on plant and machinery continue to grow, so there's an increasing need for techniques which will allow applications to be well structured and therefore manageable. The requirement for minimum effort and associated cost reductions is increasingly the focus. The aim is to reduce engineering times still further.

The graphic below illustrates the compromise that has previously been reached between minimum costs, maximum quality and rapid implementation:

However, excellent support during the engineering phase, through an appropriate programming model, a user-friendly programming environment and an extensive library, can lead to higher quality in shorter time and at a lower overall cost.

Today's safety control systems

Function blocks in safe control systems

Function blocks for safety-related functions are key to the success of safety control systems. Although initially they were more or less an image of the functions and properties found on safety relays, gradually the range has been developed to include blocks for special uses such as press applications or burner management. Today, function blocks are available for almost every conceivable safety-related application. All of these have been tested by certified bodies and offer users optimum safety for everyday use.

The concept of function blocks was originally intended for the safety control system, but was then developed to form configurable function blocks for configurable safety relays as described, making applications more customer-friendly. This approach of using configurable function blocks will also be part of a continually developing programming environment for the safety control systems. The user can choose between classic programming e.g. in IEC 61131 and a configuration similar to that of the configurable safety relays.

Certified function blocks in hardware and software.