Faculty of Electronic Engineering, Niš, Serbia

Faculty of Electronic Engineering, Niš, Serbia

Faculty of Electronic Engineering, Niš, Serbia

Faculty of Electronic Engineering, Niš, Serbia

Faculty of Electronic Engineering, Niš, Serbia

Faculty of Electronic Engineering, Niš, Serbia

Faculty of Electronic Engineering, Niš, Serbia

The paper is available at the following link: PDF

Abstract:

This paper shows the possibility of realizing robust control in the form of Discrete Sliding Mode Control (DTSMC) using MicroLogix 1400 and S7-1200 series PLC controllers. Both series of PLC controllers are primarily intended for less demanding applications and can only control industrial processes using PID instructions. Examples are given for processes that can be identified by first or second order models with or without delay (FOPDT), (SOPDT). Model identified in this way is translated into a model in the form of a differential equation in state space, and then, using Euler's method, it is translated into a discrete time system described by the model with and without disturbance based on a properly selected period of discretization. Based on the model in the state space, and the selection of the appropriate digital sliding mode controller (SMC), the control system is implemented using commands from the instruction set of PLC. The periodicity of the execution of the control law is made possible by the use of interrupt routines from PLC, which are executed with a period corresponding to the discretization period. With this, the field of application of the mentioned series of PLC controllers has been extended to the regulation of non-linear processes using SMC controllers.

Keywords:

MicroLogix 1400, Euler Approximation, Non- linearity process, Discrete Sliding Mode Control.

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