Vasile Calofir

Temperature control of a greenhouse heated by renewable energy sources

The paper proposes a system developed to provide heat for a greenhouse using parabolic trough collectors (GHPTC). The GHPTC control system has the goal to maintain the temperature inside the greenhouse at a desired level, with the actuating variable the flow of the conducting fluid through collector pipes. Considering this aspect, the proposed model takes into account as an output variable the internal temperature of the greenhouse as it influences directly the growth of the plants. The GHTPC model consists of two individual parts: the greenhouse model and the collectors model. Both were validated using real data, considering the maxim error between the real and simulated data on a period of one day. A nonlinear and linear model were deducted for the complex GHPTC system. Based on the linearized model, a PID controller was tuned and used to control the internal temperature in the greenhouse. The control method is suited for the system according to the obtained stationary and transient response performances.

A sampled-data level control of nonlinear coupled-tanks

The object of this work is to highlight, on a physical coupled tanks system, the performances of a digital design of a continuous-time passivity based controller. The design considers the sampled-data model of the plant and provides better results compared to the emulations of given continuous-time controllers. A two-state continuous-time non-linear model is used to design the digital controller. A feedback passivating controller is developed in continuous-time from a suitable choice of the storage function V. The results show good performances of the controller when increasing the sampling period or the controllers gain.

Advanced control strategies for irrigation systems

Water management and irrigation scheduling have become the main subjects of different studies in the last decades, due to their high influence on crop performance indicators. This study presents the most important parameters that have to be monitored in an irrigation management system and the most important ones are synthesized: air moisture and temperature, soil air and moisture, evapotranspiration. Based on the monitoring of these parameters, different control strategies and methods can be applied for optimization and efficiency of irrigation systems. The synthesis in this paper starts with classical control systems and, also, advanced methods such as fuzzy concept, decision support systems and model predictive control. Considering the currently necessity of integration into the Cyber-Physical Systems (CPS) concept, the paper finally proposes an irrigation control system for vineyards. The SCADA architecture is suitable for the Romanian context, it allows flexibility and ease of use and it reduced both energy consumption and irrigation operation costs.

ASID: Advanced system for process control towards intelligent specialization in the power engineering fiele

The paper presents the system architecture, development and prototype implementation of a new integrated system for simulation of automated industrial processes using advanced technologies, in accordance with CPS/Industry 4.0 principles. The need to develop such a system is underscored by the interest of the educational stakeholders: students, faculty members, high-level industry partners, for an educational system to be used in specialized training in interdisciplinary areas including edge systems in terms of modern control technologies, open systems available to be reconfigured upon request with other technologies and mission-critical applications for different process engineering fields such as key energy applications. The process simulator can be operated in educational environments as follows: as didactic equipment for learning and deepening PLCs programming languages skills; equipment for testing various complex scenarios of some energy processes while allowing on-demand reconfiguration for some industrial systems which cannot be implemented in reality due to the high cost and/or the operational safety. Given its properties — flexibility, interoperability, open architecture, compatibility in communication, friendly human-machine interface and industrial applications, ASID is able to cover a vast array of teaching scenarios as well as serve as a platform for control algorithm implementation and testing. The modular configuration allows for increased versatility and flexibility and the long-term competitiveness of the final demonstrator is assured through hardware and software updates.

Predictive control for photovoltaic tracking optimization

This paper presents the design and implementation of a control algorithm in order to command the photovoltaic panel movement to improve the availability of solar energy and the systems total efficiency. The designed algorithm is implemented on a solar tracking experimental platform using a model predictive control algorithm. It makes use of measured values for radiation from two appropriate sensors and assures command of the platforms two positioning motors. The solution was developed as a virtual instrument, using a graphical programming environment. This allows for fast deployment, versatility and scalability.