Homogeneous-redundant programmable controllers in failsafe technique

Status:

completed 01/1996

Aims:

Applying the new German standard DIN V VDE 0801 "Principles for computers in safety-related systems" was a difficult task for the manufacturers of controls. The project was intended to show that compliance with the requirements of the above standard allows for the realisation of a safety level which is comparable to that of conventional contact operating control systems. The investigations aimed to prove that homogeneous-redundant programmable controllers can generally be used to ensure the safety of press controls.

Activities/Methods:

Test methods for homogeneous-redundant programmable controllers are developed. Fault-avoiding measures in accordance with DIN V VDE 0801 were applied: e.g. inspection, walk-through, white-box-test, extended functional tests and tests relating to the effect of environmental factors.

Results:

The basic investigations yielded a number of important results for the certification of computerised controls covered by the Machinery Directive and the Low Voltage Directive. Stored programme controls make proof of a high level of hardware quality, including the operating system. If such controls are used, testing can be limited to the user programme and the correct parametric system design.

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