Industry 4.0 integrates a series of emerging technologies, such as the Internet of Things (IoT), cyber-physical systems (CPS), cloud computing, and big data, and aims to improve operational efficiency and accelerate productivity inside the industrial environment. This article provides a series of information about the required structure to adopt Industry 4.0 approaches and a brief review of related concepts to finally identify challenges and research opportunities to envision the adoption of so-called digital twins. We want to pay attention to upgrading older systems aiming to provide the well-known advantages of Industry 4.0 to such legacy systems as reducing production costs, increasing efficiency, acquiring better robustness of equipment, and reaching advanced process connectivity.

In recent years, dc microgrid (MG) is increasing rapidly in electric power grids and other isolated systems, integrating more efficiency and suite better some of the renewable energy sources, storage units, and dc loads. However, dc MG stability analysis becomes a challenge when constant power loads (CPLs) are applied to dc bus, which introduces destabilizing effects in the system due to its negative impedance characteristics. This paper presents a novel robust controller, based on linear programming based on the Chebyshev theorem as a robust control technique considering the Kharitonov’s theorem that ensures the minimization of the total deviation from the desired performance in a closed-loop system, specified by a family of characteristic polynomials. The purpose of the proposed controller is to tightly regulate the dc bus voltage, ensuring MG stability due to the effects of power variation on CPLs. The simulation and experimental tests are performed by using a MATLAB/Simulink simulator and a developed prototype of the DC MG system, respectively, to ratify the robustness and effectiveness of the proposed method of robust controller design.

Multi-converter electronic systems are becoming widely used in many industrial applications; therefore, the stability of whole system is a big concern to real-world power supplies applications. A multi-converter system comprised of cascaded converters has a basic configuration that consists of two or more converters in series connection, where the first is a source converter that maintains a regulated DC voltage on the intermediate bus while remaining are load converters that convert the intermediate bus voltage to tightly regulated outputs for the next system stage or load. Instability in cascaded systems may occur due to the constant power load (CPL), which is a behavior of the tightly regulated converters. CPLs exhibit incremental negative resistance behavior causing a high risk of instability in interconnected converters. In addition, there are other problems apart from the CPL, e.g., non-linearities due to the inductive element and uncertainties due to imprecision of mathematical model of DC-DC converters. Aiming to effectively mitigate oscillations effects in output of source converter loaded with a CPL, in this paper, an interval robust controller, by Linear Programming based on Kharitonov Rectangle, is proposed to regulate the output of source converter. Several tests were developed by using an experimental plant and simulation models, when the multi-converter buck-buck system is subjected to a variation of power reference. Both simulation and experimental results show the effectiveness of the proposed controller. Furthermore, the performance indices computed from experimental data show that the proposed controller outperforms classical control technique.

This study presents the design and evaluation of robust controllers, based on linear programming, Kharitonov's theorem and Chebyshev's theorem, in order to enhance the performance of a typical structure of multi-stage converters present in direct current (dc) systems. In such electric power distribution systems, point-of-load converters act as a constant power load (CPL), which introduces a destabilizing nonlinear effects to their supply bus voltage. The multi-stage converter system uses a simplified scheme based on cascaded converter, which is comprised of two dc-dc buck converter in series connection. The robust controllers evaluated overcome the negative incremental impedance instability problem due to CPL, which causes a high risk of instability in interconnected converters. Thereby, the robust controllers evaluated ensure robust control performance and stability with a minor performance degradation compared to a conventional controller when the cascaded converter system is subjected to parametric uncertainties. The control methodologies evaluated are applied in both dc-dc buck converters. Assessments on the performance of the control methodologies evaluated are conducted. Experimental validations on a 150-W dc-dc cascaded converter system test board are carried out to verify the theoretical claims.

This research work aims to develop a comprehensive methodology for retrofitting legacy industrial automation systems, encompassing hardware and software updates, testing, and validations, to ensure that the system aligns with current and future needs. The proposed methodology not only addresses the technical aspects but also takes into account the integration of emerging technologies such as the Internet of Things (IoT), cyber-physical systems, cloud computing, and digital twins. The main goal of the retrofitting process is to enhance the efficiency, integration, security, and interoperability of the legacy system, enabling it to remain competitive in the long term. Legacy systems may require retrofitting due to various reasons, including incompatibility with new devices or technologies, inability to meet the current needs of the manufacturing process, vulnerability to security threats, or non-compliance with current industry standards and regulations. Through the proposed methodology, step-by-step guidance will be provided, enabling organizations to successfully update their legacy systems using retrofitting techniques and capitalize on the advantages offered by Industry 4.0.

This paper describes a simulator for the three-tank system process named Sim3Tanks. This process presents a hybrid and nonlinear behavior and it is subject to different kinds of perturbations, faults, and noises. Sim3Tanks was developed in the MATLAB/Simulink environment and can be used via graphical user interface, Simulink block diagram, and command-line. Sim3Tanks is suitable for studying and developing process control, fault detection and isolation, and fault tolerant control strategies for nonlinear multi-variable systems. In order to illustrate the potential of Sim3Tanks, four scenarios are discussed throughout this paper: PID control strategies for the level and flow rates; a fault detection algorithm based on unscented Kalman filter and generalized likelihood ratio; a fault isolation system based on Bayesian networks; and a control reconfiguration based on static virtual actuator and sensor. A video demonstration of Sim3Tanks can be found at https://github.com/e-controls/Sim3Tanks.