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Reduction of surface defects by optimization of casting speed using genetic programming : an industrial case study
Miha Kovačič, Uroš Župerl, Leo Gusel, Miran Brezočnik, 2023, izvirni znanstveni članek

Opis: Štore Steel Ltd. produces more than 200 different types of steel with a continuous caster installed in 2016. Several defects, mostly related to thermomechanical behaviour in the mould, originate from the continuous casting process. The same casting speed of 1.6 m/min was used for all steel grades. In May 2023, a project was launched to adjust the casting speed according to the casting temperature. This adjustment included the steel grades with the highest number of surface defects and different carbon content: 16MnCrS5, C22, 30MnVS5, and 46MnVS5. For every 10 °C deviation from the prescribed casting temperature, the speed was changed by 0.02 m/min. During the 2-month period, the ratio of rolled bars with detected surface defects (inspected by an automatic control line) decreased for the mentioned steel grades. The decreases were from 11.27 % to 7.93 %, from 12.73 % to 4.11 %, from 16.28 % to 13.40 %, and from 25.52 % to 16.99 % for 16MnCrS5, C22, 30MnVS5, and 46MnVS5, respectively. Based on the collected chemical composition and casting parameters from these two months, models were obtained using linear regression and genetic programming. These models predict the ratio of rolled bars with detected surface defects and the length of detected surface defects. According to the modelling results, the ratio of rolled bars with detected surface defects and the length of detected surface defects could be minimally reduced by 14 % and 189 %, respectively, using casting speed adjustments. A similar result was achieved from July to November 2023 by adjusting the casting speed for the other 27 types of steel. The same was predicted with the already obtained models. Genetic programming outperformed linear regression.
Ključne besede: continuous casting of steel, surface defects, automatic control, machine learning, modelling, optimisation, prediction, linear regression, genetic programming
Objavljeno v DKUM: 25.03.2024; Ogledov: 154; Prenosov: 9
.pdf Celotno besedilo (1,19 MB)
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A PID servo control system experiment conducted remotely via Internet
R. M. Parkin, C. A. Czarnecki, Riko Šafarič, D. W. Calkin, 2002, izvirni znanstveni članek

Opis: The principles of robotics and control are widely taught in engineering subjects, however a common problem concerns the limited availability of expensive equipment with which students can work with, in order to acquire valuable practical "hands on" experience. The MuMaTE virtual robotics and control project on the World Wide Web (www) was launched to evaluate the suitability of virtual learning environments, the Internet, and multimedia technologies within an engineering-based flexible learning program. Students using networked computers can access this facility to study a wide variety of on-line course material and perform a series of interactive experiments with real world laboratory hardware. This paper presents an on-line experiment, which enabled users to successfully control and observe the response of a commercial position servo system. The development of the project web server, interface electronics and control software is also discussed.
Ključne besede: automatic control, control, control systems, virtual learning, distance learning, servo system
Objavljeno v DKUM: 01.06.2012; Ogledov: 1922; Prenosov: 83
URL Povezava na celotno besedilo

Fuzzy control strategy for an adaptive force control in end-milling
Uroš Župerl, Franc Čuš, Matjaž Milfelner, 2005, izvirni znanstveni članek

Opis: This paper discusses the application of fuzzy adaptive control strategy to the problem of cutting force control in high speed end-milling operations. The research is concerned with integrating adaptive control with a standard computer numerical controller (CNC) for optimising a metal-cutting process. It is designed to adaptively maximise the feed-rate subject to allowable cutting force on the tool, which is very beneficial for a time consuming complex shape machining. The purpose is to present a reliable, robust neural controller aimed at adaptively adjusting feed-rate to prevent excessive tool wear, tool breakage and maintain a high chip removal rate. Numerous simulations and experiments are conducted to confirm the efficiency of this architecture.
Ključne besede: automatic control, end milling, adaptive force control, fuzzy adaptive control
Objavljeno v DKUM: 01.06.2012; Ogledov: 1913; Prenosov: 91
URL Povezava na celotno besedilo

Pressure control in hydraulic systems with variable or constant pumps?
Darko Lovrec, Samo Ulaga, 2007, izvirni znanstveni članek

Opis: The paper deals with electrohydraulic supply systems with variable (adjustable( supply pressures. Two control concepts are used in practice: the pressure control concept using a variable pump and constant speed of the driving electric motor as the commonly used concept, and the pressure control concept with a constant pump and a speed-controlled electric motor as the alternative concept. The typical features and the applicability of both conceps, as well as their dynamic responses are studied in this work.
Ključne besede: automatic control engineering, hydraulic systems, pressure control, constant pumps
Objavljeno v DKUM: 31.05.2012; Ogledov: 2297; Prenosov: 0

Electrohydraulic pressure control by a self-adjusting proportional derivative controller
Darko Lovrec, Friedrich Faber, 2006, izvirni znanstveni članek

Opis: The main characteristic of an electrohydraulic pump control system is the presence of an electrical signal path. It requires at least one sensor for the controlled value (in this case pressure), delivering feedback to be compared with the electrical or numerical reference in the controller. The additonal expense penalty for the sensor and the valve is offset by the advantage of flexibility in the structure and parameters of the controller in comparison to hydraulic - mechanical concepts. Thus, the transfer response can be adapted to demands, even in the operational state. Sophisticated control structures can be implemented easily in the form of computer or microcontroller programs. The layout of electrohydraulic pressure control discussed in this study includes the presented loading unit. The variable pump is designed to act together with a proportional valve having two metering edges. It is less expensive compared to the design with a synchronizing cylinder and four metering edges. However, only inferior static and dynamic performance can be expected. Hydraulic energy is supplied to the control valve directly from the output port of the pump - with the advantage of simple assembly, as there are no additional components required - but with the drawback that there is influence on the control loop`s properties at every change in the disturbance value or reference. The aim of the study presented in this paper is a more efficient and simple concept compared to other known methods for pressure control of the above mentioned pump including the dynamics of the distribution network, and also the characteristics of the hydraulic load with special focus on improvements in steady state and dynamic behaviour.
Ključne besede: automatic control engineering, electrohydraulic systems, pressure control, self-adjusting proportional controller
Objavljeno v DKUM: 31.05.2012; Ogledov: 2175; Prenosov: 139
URL Povezava na celotno besedilo

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