Control Engineering in Materials Processing

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Authors: Józef Bednarczyk, Andrzej Sioma
Abstract: This paper discusses a visual method of measuring the geometric parameters of elements produced by electrodynamic stamping. This paper presents also electrodynamic method which is an unconventional machining technology, which complements the capabilities of traditional technologies, in particular as regards the formation of metal elements with low-profile dies of complex shape. The article discusses issues related to resolution of the vision system, resolution of laser beam analysis, and resolution relating to the measurement of the height profile on the surface of the product. Based on the model constructed in such a way, measurements are presented in order to assess the dimensional parameters. Based on tests and analyses of the three-dimensional model, a range of inspection tasks using 3D vision systems is indicated.
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Authors: Marek Sibielak, Waldemar Rączka, Jarosław Konieczny
Abstract: Smart materials are being applied more and more widely in semi-active vibration reduction systems. Actuators built with their use are characterized by nonlinearities and hysteretic effects. Their omission in mathematical descriptions may lead to deterioration of the vibration reduction systems. For that reason, it is important to take into account these negative phenomena associated with the actuators at the controller synthesis stage. One method for determining the control laws in semi-active vibration reduction systems that is frequently discussed in academic literature is “Clipped-LQR”. The present paper proposes modification of that method to allow inclusion in the controller synthesis of the hysteretic properties and other nonlinearities of an actuator. The method developed was verified by determining the controller for the semi-active suspension of a machine operator’s seat. A magnetorheological damper was used as an actuator. The dynamic properties of the foam covering of the operator’s seat were included in model. Simulation tests were performed on the vibration reduction system and function of vibration transmissibility was determined. The semi-active vibration reduction system tested was compared to a passive system. The considerations presented herein relate to the semi-active suspension of a machine operator’s seat, and the method presented may be applied to other controlled systems with many degrees of freedom.
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Authors: Andrzej Kot
Abstract: The paper presents description of physical phenomena arising during the process of electrodynamic forming by means of axisymetric inductors generating pulse magnetic field. Presented material shows the way for determination of pressures acting on non-ferrous pipe elements with an assumption of magnetic flux variation character in system. The paper describes also stages of energy conversion from electric energy of capacitors discharge into mechanical energy of pressure forming semi-finished product. The knowledge about presented phenomena allow to predict final shape of formed product during free forming by electrodynamic method.
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Authors: Marcin Kot, Tomasz Moskalewicz, Bogdan Wendler, Aleksandra Czyrska-Filemonowicz, Wiesław Rakowski
Abstract: The nanocomposite coatings composed of nanocrystalline TiC grains embedded in hydrogen free amorphous carbon a-C matrix (nc-TiC/a-C) were deposited by magnetron sputtering on the two substrates, oxygen hardened Ti-6Al-4V alloy and heat treated VANADIS 23 steel. The Ti-6Al-4V alloy was oxygen hardened by plasma glow discharge. Micro-mechanical and tribological properties as well as coating adhesion to the substrates were investigated. Micro/nanostructure of the coatings and the substrates were examined using scanning- and transmission electron microscopy methods as well as X-ray diffractometry. Nano-, microhardness tests performed for the coated materials showed average hardness 13.4-14.7 GPa and modulus of elasticity 160 GPa. Scratch test revealed good adhesion of coatings to the both substrates. The nanocomposite coatings significantly improved tribological properties of the titanium alloy and steel, increased wear resistance and decreased friction coefficient.
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Authors: Janusz Pluta, Marek Sibielak
Abstract: This paper aims to present the results of the testing a single-stage electrically actuated throttle valve, in which a piezoelectric stack was used for adjustment of the flow section area of the throttle aperture. The valve prototype was built based on a proprietary design, using the components of a standard manufactured overflow valve. The complete valve was designed on the basis of the results of simulation tests performed on a mathematical model. The constitutive equations presented herein, describing all critical phenomena and influences present in the component, were applied for the modelling of the piezoelectric stack. Laboratory tests were carried out to establish the valve’s characteristics, describing its usefulness for control of flow intensity. LabView software was used for measuring the data gathered. The test results, after conversion, were developed using the Matlab/Simuling software package. This paper presents the most notable results of the tests of a normally open valve equipped with a high-voltage piezoelectric stack. Based on the results obtained, the functional correlation between the volumetric flow rate, pressure drop in the throttling aperture and control signal input to the piezoelectric stack were determined. Due to the comprehensive approach involved, the material presented herein may be prove useful to designers of valves and hydraulic units using piezoelectric stacks for controlling their operating units.
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Authors: Waldemar Rączka, Jarosław Konieczny, Marek Sibielak
Abstract: The article discusses a prototype of a Shape Memory Alloy (SMA) spring intended for controlled vibration reduction systems. The spring has been subject to experiments and the article presents selected static and dynamic characteristics. The experiments were conducted at the Dynamics and Control of Structures Laboratory of the AGH University of Science and Technology. They permitted the formulation of a mathematical model for the SMA spring. The model takes into account the phenomena of energy accumulation and dissipation. The parameters of the spring model have been determined, based on the experimental data. The model takes into account the relationship of stiffness and damping to alloy temperature and the frequency of excitation. It has been demonstrated that the properties of the spring may be altered under controlled conditions. The spring model was then used in simulations. They served as the basis for the determination of the frequency response characteristics, which were then compared to the characteristics of a real spring. The mathematical model developed may be applied in the design of passive, semi-active, and active vibration reduction systems, as well as in the synthesis of adaptive smart vibration reduction systems.
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Authors: Piotr Skubisz, Piotr Micek, Jan Sińczak, Marek Tumidajewicz
Abstract: The paper presents the methodology of determination of emissivity coefficient of steel in the direct cooling temperature range, which allow self-definition of this parameter in automated temperature control system used for direct cooling of drop-forged parts. Based on the actual temperature of the surface of the workpiece, the system automatically adjusts the velocity of fan-forced air to produce desired cooling rate and course of cooling curves. To enable automatic correction of cooling rate, the system must rely on exact remote temperature measurements. This is conditioned by correct definition of emissivity in pyrometer gauge system. Traditionally, pyrometers use presets of a constant value, selected as to get optimum consistency for the temperature range concerned. As the emissivity is time-dependent, the idea of the approach presented in the paper is to use time dependent characteristics, to attain the minimum discrepancy between actual and measured values during the whole cooling cycle.
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Authors: Ireneusz Dominik
Abstract: The rotational inverted pendulum is a structure that was primarily developed by Katsuhisa Furuta. It is widely used thorough the control laboratories to demonstrate the effectiveness of nonlinear control algorithms. The rotational inverted pendulum is a nonlinear system of fourth order with a single input variable. In this article the full dynamic equations of motion of the rotational inverted pendulum are derived using Lagrangian formulation. Consequently, a comparison of obtained mathematical model with other models described and available in literature is conducted by means of computer simulations. Eventually, a complete energy build-up swing-up algorithm and fuzzy stabilization algorithm for the system are developed. The control algorithm is then implemented on a PLC device in order to control the existing laboratory stand available at the Department of Process Control [1]. The algorithm is implemented with the use of ladder logic and structured text programming language. The robustness of elaborated balancing control is verified by subsequent real-time tests conducted on the laboratory stand.
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Authors: Ireneusz Dominik
Abstract: During research on SMA wires the prototype of linear position actuator was built. The shape memory alloy (SMA) wires used in construction of the actuator are nonlinear and time variant. Thus, it was decided to use a fuzzy controller to control the actuator. However, because of the nature of SMA wires which work by changes of their temperature, after a few minutes of continuous work the actuator did not work accurately. In other words, the existing singleton values in a knowledge base were inappropriate. That is why each time after longer continuous work of the actuator it was needed to manually find and change the mentioned values. It took a lot of time and effort so eventually it was decided to create a real time auto-tuning algorithm which could identify crucial parameters of the actuator each time when it was needed. Together with initial values learning algorithm the advanced controlling of SMA actuator was created.
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