With the recent advancement in Industrial Internet of Things (IIoT), general programmable logic controllers (PLCs) have been playing more and more critical roles in industrial control systems (ICSs), such as providing local data processing, decentralized control and fault diagnosis. These so called edge-PLCs, directly receive the raw data from sensors embedded in factory equipments, put them into predefined memory space and perform analysis using programs such as the ladder logic. The challenge is how to allocate blocks in the fixed-size memory to different sensors so as to match irregular data flows. In this paper, we try to conduct performance analysis of different partition instances of the memory in the edge-PLC by modeling this problem as a multiple single-server queueing systems. We assume every sensing flow is independent of each other and has its dedicated processer. Changes can be made to partition instances to adapt to the external environment, such as the rising of order numbers or product category switching. Each state of the environment is defined by the finite state Markov chain and arrival of sensing data flows follow the stationary Poisson process. The data in the queue will expire after staying in the memory for a while. The duration of availability and service is modeled as the exponential distribution. The performance measured under different system states are analyzed in the simulation.

中文翻译：

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边缘PLC的性能分析支持工业物联网

随着工业物联网（IIoT）的最新发展，通用可编程逻辑控制器（PLC）在工业控制系统（ICS）中扮演着越来越重要的角色，例如提供本地数据处理，分散式控制和故障诊断。这些所谓的Edge-PLC，直接从工厂设备中嵌入的传感器接收原始数据，将其放入预定义的存储空间，并使用梯形逻辑等程序执行分析。挑战在于如何将固定大小的内存中的块分配给不同的传感器，以匹配不规则的数据流。在本文中，我们通过将问题建模为多个单服务器排队系统，尝试对Edge-PLC中的内存的不同分区实例进行性能分析。我们假设每个传感流都相互独立，并具有专用的处理器。可以对分区实例进行更改以适应外部环境，例如订单号的增加或产品类别的切换。环境的每个状态均由有限状态马尔可夫链定义，传感数据流的到达遵循平稳的泊松过程。队列中的数据在内存中保留一段时间后将过期。可用性和服务的持续时间被建模为指数分布。在仿真中分析了在不同系统状态下测得的性能。环境的每个状态均由有限状态马尔可夫链定义，传感数据流的到达遵循平稳的泊松过程。队列中的数据在内存中保留一段时间后将过期。可用性和服务的持续时间被建模为指数分布。在仿真中分析了在不同系统状态下测得的性能。环境的每个状态均由有限状态马尔可夫链定义，传感数据流的到达遵循平稳的泊松过程。队列中的数据在内存中保留一段时间后将过期。可用性和服务的持续时间被建模为指数分布。在仿真中分析了在不同系统状态下测得的性能。