Stelian Oltean | G.E. Palade UMPhST of Targu Mures (original) (raw)

Papers by Stelian Oltean

2008 IEEE International Conference on Automation, Quality and Testing, Robotics, 2008

ABSTRACT Electron beams have many special properties which make them particularly well suited for... more ABSTRACT Electron beams have many special properties which make them particularly well suited for use in materials processing, wherever conventional techniques failed or proved to be inefficient. The entire process has many time varying parameters, but some of the most important for the quality of the material processing are given by the directing parts. The paper presents a 3D control system of the electron beam spot which contains the focusing and deflecting components. Due the nature of the process we used a PI control for the deflecting system and an adaptive fuzzy control for the focusing system.

The 15th International Conference Interdisciplinarity in Engineering

2006 IEEE International Conference on Automation, Quality and Testing, Robotics

A significant role in obtaining a comfortable environment in a residential, office, factory or ot... more A significant role in obtaining a comfortable environment in a residential, office, factory or other public interest buildings is conferred in a large measure to the lighting and the heating. These two components through their efficiency can assure important benefits to the users of that environment. Estimating the lighting and heating efficiency can be achieved through attending the qualitative and

Scientific Bulletin of the ''Petru Maior" University of Tîrgu Mureș, 2017

The process of manufacturing parts with additive technologies has seen tremendous growth in recen... more The process of manufacturing parts with additive technologies has seen tremendous growth in recent years, and the emergence of more 3D open source printers has led to complex and personalized shapes at a lower price. For these reasons, 3D printers that form parts by extruding a filament of molten plastic are becoming standard equipment in many laboratories and workshops. In this context, the paper aims to present some theoretical aspects about the implementation and testing of a low cost 3D printer using open source technologies, the description of its main components and the stages to be taken from the 3D modelling of an object to the proper printing.

Scientific Bulletin of the ''Petru Maior" University of Tîrgu Mureș, 2011

Electron beams have many special properties which make them particularly well suited for use in m... more Electron beams have many special properties which make them particularly well suited for use in materials processing, wherever conventional techniques failed or proved to be inefficient. The entire process has a lot of time varying parameters, so using a distributed control system for 3d position of the electron beam spot may improve the quality of the material processing. Matlab environment was used for model implementation and simulations of the control system which contains the focusing and deflecting components. Due the nature of the process and knowing the electron beam equipment we proposed for the simulations scenarios with a 3D virtual surface.

Scientific Bulletin of the ''Petru Maior" University of Tîrgu Mureș, 2012

The effects of shunt compensation on power system transmission stability and modern approach of t... more The effects of shunt compensation on power system transmission stability and modern approach of the reactive power control scheme have been investigated in this paper. Reactive power compensation is realized in shunt connection with two components: thyristor controlled reactor (TCR) and thyristor switched capacitor (TSC). A special attention has been given in the following paragraphs to a modern control approach for power system stability enhancement which uses fuzzy logic. In the final part of the paper the modern control block scheme of static VAR compensator for reactive power in transmission systems is presented.

Scientific Bulletin of the ''Petru Maior" University of Tîrgu Mureș, 2009

Electron beam material processing is an important nonconventional technique used in many industri... more Electron beam material processing is an important nonconventional technique used in many industrial fields where the conventional methods proved to be inefficient. The entire process has many time varying parameters, but some of the most important for the quality of the material processing are given by the directing part of the equipment which contains the focusing and deflecting systems. These systems modify the beam diameter, focus distance and beam penetrations in the material. One of the first stages for the control system design is the modelling and simulation of the process, in this case the focusing and deflecting systems. The study and simulations results help the engineers to know the process characteristics and what type of control is needed. After simplifying, the resulted focusing model is nonlinear and the deflecting model is considered linear on small angles. The simulations shown in the paper are obtained using Matlab environment.

In the industrial domain, a large number of applications is covered by slow processes, including ... more In the industrial domain, a large number of applications is covered by slow processes, including the flow, the pressure, the temperature and the level control. Each control system must be treated in steady and dynamic states and from the point of view of the possible technical solutions. Based on mathematical models of the processes and design calculations, PC programs allow simulation and the determination of the control system performances.The paper presents a part of an industrial process with classical control loops of flow and temperature. The mathematical model of the flow control process was deducted, the control structure, based on experimental criterions, was designed and the version witch ensure the imposed performances was chosen. Using Matlab, the robustness performances were studied.

2010 IEEE International Conference on Automation, Quality and Testing, Robotics (AQTR), 2010

Scientific Bulletin of the ''Petru Maior" University of Tîrgu Mureș, 2016

The proportional integral derivative (PID) controller has a known structure used in feedback cont... more The proportional integral derivative (PID) controller has a known structure used in feedback control of industrial processes. One of the most common applications is the control of the DC motor. The paper presents a didactic system designed for educational purposes used for studying various conventional PID structures and the influence of the PID components in the control process of the DC motor's speed. The system contains a low cost acquisition board based on PIC 16F628A microcontroller. The experimental results are shown graphically using a PC application made in Matlab environment.

of the PhD Thesis Modelling and Control of the Nonconventional Material Processing Technologies w... more of the PhD Thesis Modelling and Control of the Nonconventional Material Processing Technologies with Electron Beam PhD Student: eng. Stelian Emilian OLTEAN Thesis advisor: Prof.dr.eng. Mihail ABRUDEAN

Processes with large time constants, like the level process, represent a large number of applicat... more Processes with large time constants, like the level process, represent a large number of applications in industry. These systems must be treated in both steady and dynamic state and effective control solutions should be proposed. In a PI controller working under saturation, problems like windup appear. This paper presents a classical PI-controlled feedback loop, which is part of an industrial level control system. Based on the existing PI controller, antiwindup and feedback compensation schemes are proposed in order to improve the system’s performances. Matlab-Simulink models are implemented to validate the control system design.

The paper describes the behavior of three automatic lighting control systems (ALCS), the first ba... more The paper describes the behavior of three automatic lighting control systems (ALCS), the first based on a fuzzy controller, the second - on a fuzzy-neural controller and the third - on a neural controller. The ALCSs attempt to maintain the illuminance on working plane at the desired constant level even if the daylight contribution is variable. Therefore, the daylight will represent the perturbation signal for ALCSs. For all systems, we have considered the same process and the same trajectory of daylight contribution. The fuzzy-neural and neural ALCSs need the inverse mathematical model of the process. These ALCSs uses a neural net trained to reproduce the inverse mathematical model of the process. From an automatic theory point of view the ALCSs have different behaviors. But, considering the human eye perception, all ALCSs have the same behavior. The advantage of fuzzy ALCS consists on the fact: does not need the inverse mathematical model of process. This type of ALCS do not need t...

Procedia Manufacturing, 2020

The paper presents a study of a hydraulic turbine control, considering that the gate opening depe... more The paper presents a study of a hydraulic turbine control, considering that the gate opening depends on the velocity of the water. The behavior of the mechanical power of the turbine and speed control of the generator affected by parameter uncertainties have been simulated using the Matlab/Simulink environment. The time domain step responses and frequency analysis of two designed control algorithms emphasize the performances of the system with the hydraulic turbine and load affected by uncertainties. The paper can be used also by electrical engineering students as a guideline in order to model, simulate, study and tune the controllers for a hydraulic turbine unit.

Proceedings

An important stage in robust control design is to define the desired performances of the closed l... more An important stage in robust control design is to define the desired performances of the closed loop control system using the models of the frequency sensitivity functions S. If the frequency sensitivity functions remain within the limits imposed by these models, the control performances are met. In terms of the sensitivity functions, the specifications include: shape of S over selected frequency ranges, peak magnitude of S, bandwidth frequency, and tracking error at selected frequencies. In this context, this paper presents a study of the effects of the specifications of the weighting functions on the performances of robust control systems.

Journal of Control Engineering and Applied Informatics, 2008

The material processing with the electron beams solves great topical problems, wherever conventio... more The material processing with the electron beams solves great topical problems, wherever conventional techniques proved to be inefficient. Material processing involves many complex phenomenons like the electrons generation, beam forming and transport, heat absorption in the workpiece. The information about the heated surface with electron beam is obtained only using the electrons reflected from the material surface. So, modern control strategies using artificial intelligence, adaptive and expert systems implemented on digital systems are required to produce high quality material processing. In this paper we present advanced methods used to control the energy density of the electron beam transmitted to the workpiece. The multivariable control system has three directing components: the focusing system dedicated to focus distance control and two deflecting systems for the joint tracking. The desired references for these components are determined from the digital images constructed using...

Adaptive controllers are used for plants with unknown or time varying parameters. The robotic arm... more Adaptive controllers are used for plants with unknown or time varying parameters. The robotic arm is a classical case of plant with unknown parameters because the load modifies in time. Using the Lyapunov theory for the parameters adaptation law assures the global stability and robustness of the system and superior performances in presence of the disturbance or in case of plant parameters changes. An alternative to global control of the robot is the local compensation of the load and interdependencies for every arm, which means a D.C. motor adaptive control problem. The paper presents the design of the local adaptive control of the robotic arm driven by a D.C. motor using Lyapunov stability theory. The globally model of the designed system is implemented in Matlab Simulink and simulated to different references.

The Inverted Pendulum is one of the most important classical problems of Control Engineering. Bro... more The Inverted Pendulum is one of the most important classical problems of Control Engineering. Broom Balancing (Inverted Pendulum, pole on a cart) is a well known example of nonlinear, unstable control problem. The basic control objective of the inverted pendulum problem is to maintain the unstable equilibrium position, by controlling the force applied to the mobile cart in the horizontal direction. In this paper we provide a comparative analysis of two model reference adaptive control (MRAC) methods, the first one based on the stability theory of Lyapunov and the other one based on fuzzy logic (FMRLC - Fuzzy Model Reference Learning Control). The performances of the proposed control algorithms are evaluated and shown by means of digital simulation.

The static var compensators SVC are FACTS devices in shunt connection which can be used for power... more The static var compensators SVC are FACTS devices in shunt connection which can be used for power system enhancement. The paper investigates a modern approach for SVC control using fuzzy logic based controller. The simulations and effects of shunt compensation on power system transmission stability are also presented. The SVC modeled in the paper is a TCR-FC type with two components: the thyristor controlled reactor (TCR) and the fixed capacitor (FC). The performances of fuzzy based control of the SVC are compared with a conventional compensation and the advantages of modern control to offer significant damping to the system oscillations are highlighted. Matlab Simulink environment was used for system modeling and simulations.