Hassapis G
Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece.
ISA Trans. 2000;39(3):345-55. doi: 10.1016/s0019-0578(00)00029-x.
This paper presents a technique and the means for testing PLC-based control software outside the actual plant environment with the purpose of increasing the confidence level on the compliance of the software to functional and temporal requirements. The need to obtain a high confidence level on the correct software operation arises from the fact that in most of the cases it is quite dangerous and expensive to test unproved PLC operation by linking it with the actual facilities that it is going to control. The proposed technique relies on a combined simulation of the controlled plant and the PLC system and an analysis of the plant responses. The PLC system simulation imitates the way software is executed on a PLC that is programmed in the languages of the IEC1131-3 standard. It is based on the programming model of the IEC standard and analytical formulae for estimating the program runtime. The simulation of the plant is based on a discrete convolution model that is solved at the same rate with the rate determined by the control algorithms. A tool realizing these concepts has been developed and its use in testing the control software of three critical outputs of a distillation column is demonstrated.
本文提出了一种在实际工厂环境之外测试基于PLC的控制软件的技术和方法，目的是提高对软件符合功能和时间要求的置信度。由于在大多数情况下，将未经验证的PLC操作与它将要控制的实际设施相连进行测试是非常危险且昂贵的，因此需要对软件的正确运行获得高置信度。所提出的技术依赖于对受控工厂和PLC系统的联合仿真以及对工厂响应的分析。PLC系统仿真模仿了软件在按IEC1131-3标准语言编程的PLC上的执行方式。它基于IEC标准的编程模型和用于估计程序运行时间的解析公式。工厂的仿真是基于一个离散卷积模型，该模型以与控制算法确定的速率相同的速率求解。已经开发了一个实现这些概念的工具，并展示了其在测试精馏塔三个关键输出的控制软件中的应用。
