Sunday, July 24, 2011

Unit Testing and Coding of PLC for Plant System I&C

Unit testing and Coding will be executed concurrently. It has been established that unit testing radically improves the robustness and reliability of the code generated. This means that each FC and FB must be tested autonomously. The architecture standard makes this simpler, as the core application has no straight external interface. So any block programmed interface in the core application can be substituted by a variable in sequence to imitate the behavior of the interface. Unit testing doesn’t need a official document. Though, if too many errors are detected during the validation phases, a test of official unit document may be asked by IO.

Simulated Validation Testing
The standard is to have a simulation test carried out before the test with the system associated. There are some reasons:
• The actual system does not constant must be associated/ready for activities of testing. Their life cycles can be desynchronized until link.
• As many functional problems as possible tracking before linking to the actual system. The software will be more established at the connection time, so fewer time will be lost in troubleshooting of software during testing the system.
• It will be probable to test the I&C in its integrality level when the systems have been acquired individually when the I&C is created of few controllers.
• If simulation is accessible, corrective and adaptive maintenance will be probable without having the connected of system.

This phase is possible, as it might not make many senses for systems of small plant. For systems of large plant with a lot of controllers, simulation will involve only low functionality level. The complex algorithms of development with multiple couplings is too time consuming and does not value added. Nevertheless, it is severely suggested. The simulator development and the control units development will be completed by different people. Therefore different understandings of how the system control should run will be brought face to face at an early project phase. The simulator will be linked to the controllers throughout the network field. It will read or write the variables of joint DB identified in the layer of controller simulation. These variables will substitute the real I/Os controller. There is no specification so far relating to the technology to be used for the simulator development, but the simulator will be sent to IO after FAT.

Integrated Validation Testing
This test will be performed during FAT and will be created with the connected of real system. Since some components may not be on hand during this phase, the strategy will be applied.

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