The Profinet/Interbus proxy with integrated safety control is the basic component of the Interbus Safety system. The proxy exchanges standard data with the connected participants via the Profinet IO device interface.

 

Further, it provides the safety I/O data to the standard control for diagnostics. The safety input and output components form the interface to the peripherals. Using the safety-oriented Profinet/Interbus proxy, they communicate using a transparent safety protocol transferred based on the standard Interbus protocol. The Black Channel principle used with Interbus Safety allows safety-oriented data to be transferred via the standard network.

 

As a consequence the bus system does not handle any safety-oriented tasks, but only acts as a data transfer medium. In this way, safety-oriented and non-safety-oriented components can be connected to one and the same network cable. A two-cable solution can be alternatively used with separate cabling for the standard and safety communication. When using Interbus Safety technology, there are absolutely no restrictions when it comes to cabling the safety network. This also applies when using copper or fiber-optic cables, which offer tried and tested robustness as well as a comprehensive range of diagnostics inherent to the standard Interbus system.

The control integrated in the Profinet/Interbus proxy processes the safety-oriented inputs and accepts the standard control when setting an output or resetting the output. This technique, which essentially corresponds to the mode of operation of separately executed safety technology, reduces the complexity of the application. Further, freedom from any reaction is ensured as the safety technology is separated from the standard control. This means that changes can be made to the standard control - such as changing a device or expanding the hardware or parts of programs - independently and without the safety technology having to be additionally tested.

The one-bit data transfer also plays a role in simplifying safety-oriented communication. It ensures the diagnostics capability of the peripherals on the input and output components using an internal logic, and provides the programmer with the signal – for instance, "Emergency stop is pressed" – as a bit in the programming interface.

 

The efficient shift register protocol of the standard Interbus system and the integration of the safety technology into the interface module results in short response times. As a result of its system architecture, presently, Interbus Safety is the only safety fieldbus system available in the market that is in a position to monitor the response time of the complete safety circuit from the input terminal and the safety control through to the output terminal for individual channels. What’s more, when the response time is exceeded, the corresponding output is shutdown. The shutdown time to be monitored is parameterized and is guaranteed by the system along the entire safety circuit.

The safety control is programmed using the SafetyProg software that is in compliance with the international standard IEC 61131. Not only this, the user is supported by certified safety function blocks. The blocks, developed in accordance with the PLCopen standard, address standard safety applications such as emergency stop, two-hand operation, guard door with locking mechanism as well as light grid and scanner applications. As a consequence, not only are programming costs reduced, but verification and validation of the application are also simplified.

The combination of Diag+ diagnostic tool, the Interbus Safety system and the safety function blocks, increases the integrated diagnostics as well as the cost-effectiveness and the availability of the application. Diag+, which can be integrated as an ActiveX component in other software tools – such as process visualization systems – automatically supplies the control with all of the diagnostics data in plain text. This means that the diagnostics and the communication do not have to be programmed and users don’t have to generate their own visualization systems.

In safety-oriented applications, short circuits and cross-circuit faults, an actuated emergency stop switch or an open guard door must be identified. This is mandatory. If a function such as an emergency stop is requested in the Interbus Safety system, the diagnostics software provides plain text information about the location and the cause. In addition, the operator is provided with clear instructions on how to resolve the fault. The necessary operator actions required to resolve the fault - for instance, to release the emergency stop switch and acknowledgement - are accompanied and tracked by the tool.

Separating the standard and safety controls means that the systems are reaction free – and as a consequence, users can operate control systems from different manufacturers connected to one I/O system. Tried and proven Interbus Safety functions are made available to the Profibus world via the proxy. These functions include short response times, comprehensive diagnostics, parameterizable and fixed shutdown times, simple installation and high availability as well as the plug & play functionality, which eliminates the need to set addresses.

For the standard control, the Profinet/Interbus proxy represents a separate network card, which provides it with all sensor and actuator signals. Additional information of the safety-oriented process is available as process or communication data. The output data of the non-safety PLC are sent directly to the output modules, while the safety control only influences the safety-oriented outputs or accepts these – and automatically transfers parameter data to the safety-oriented participants after the system boots. This means that expert knowledge is not required if a device has to be replaced.

Using the proxy functionality, users can sub-divide the complete application into individual cells or function units, while the higher-level line controls smoothly interoperate with the distributed safety-oriented processes. This significantly simplifies commissioning individual areas as well as expanding existing applications.

Large plants and systems – such as those used in the automotive sector – are not the only areas where it makes sense to use safety-oriented fieldbus solutions like Interbus Safety. As a result of the advantages mentioned above, when compared to conventional safety technology, numerous manufacturers of smaller machines and plants have decided to use the safety-oriented bus system. Some examples include projects in the area of canal locks and fire simulation systems as well as in high-bay racking systems and various research and development facilities.