The Bulletin of the Polish Academy of Sciences Technical Sciences is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred:
Artificial and Computational Intelligence,
Biomedical Engineering and Biotechnology,
Control, Informatics and Robotics,
Electronics, Telecommunication and Optoelectronics,
Mechanical and Aeronautical Engineering, Thermodynamics,
The eigenvalues assignment problems for descriptor linear systems with state and its derivative feedbacks are considered herein. Necessary and sufficient conditions for the existence of solutions to the problems are established. The Euler and Tustin approximations of the continuous-time systems are analyzed. Procedures for computation of the feedbacks are given and illustrated by numerical examples.
This paper presents the control design framework for the hybrid synchronization (HS) and parameter identification of the 3-Cell Cellular Neural Network. The cellular neural network (CNN) of this kind has increasing practical importance but due to its strong chaotic behavior and the presence of uncertain parameters make it difficult to design a smooth control framework. Sliding mode control (SMC) is very helpful for this kind of environment where the systems are nonlinear and have uncertain parameters and bounded disturbances. However, conventional SMC offers a dangerous chattering phenomenon, which is not acceptable in this scenario. To get chattering-free control, smooth higher-order SMC formulated on the smooth super twisting algorithm (SSTA) is proposed in this article. The stability of the sliding surface is ensured by the Lyapunov stability theory. The convergence of the error system to zero yields hybrid synchronization and the unknown parameters are computed adaptively. Finally, the results of the proposed control technique are compared with the adaptive integral sliding mode control (AISMC). Numerical simulation results validate the performance of the proposed algorithm.
The wind energy conversion systems (WECS) suffer from an intermittent nature of source (wind) and the resulting disparity between power generation and electricity demand. Thus, WECS are required to be operated at maximum power point (MPP). This research paper addresses a sophisticated MPP tracking (MPPT) strategy to ensure optimum (maximum) power out of the WECS despite environmental (wind) variations. This study considers a WECS (fixed pitch, 3KW, variable speed) coupled with a permanent magnet synchronous generator (PMSG) and proposes three sliding mode control (SMC) based MPPT schemes, a conventional first order SMC (FOSMC), an integral back-stepping-based SMC (IBSMC) and a super-twisting reachability-based SMC, for maximizing the power output. However, the efficacy of MPPT/control schemes rely on availability of system parameters especially, uncertain/nonlinear dynamics and aerodynamic terms, which are not commonly accessible in practice. As a remedy, an off-line artificial function-fitting neural network (ANN) based on Levenberg-Marquardt algorithm is employed to enhance the performance and robustness of MPPT/control scheme by effectively imitating the uncertain/nonlinear drift terms in the control input pathways. Furthermore, the speed and missing derivative of a generator shaft are determined using a high-gain observer (HGO). Finally, a comparison is made among the stated strategies subjected to stochastic and deterministic wind speed profiles. Extensive MATLAB/Simulink simulations assess the effectiveness of the suggested approaches.
In the present paper, the model of multi–server queueing system with random volume customers, non–identical (heterogeneous) servers and a sectorized memory buffer has been investigated. In such system, the arriving customers deliver some portions of information of a different type which means that they are additionally characterized by some random volume vector. This multidimensional information is stored in some specific sectors of a limited memory buffer until customer ends his service. In analyzed model, the arrival flow is assumed to be Poissonian, customers’ service times are independent of their volume vectors and exponentially distributed but the service parameters may be different for every server. Obtained results include general formulae for the steady–state number of customers distribution and loss probability. Special cases analysis and some numerical computations are attached as well.
Maritime Autonomous Surface Ships (MASS) perfectly fit into the future vision of merchant fleet. MASS autonomous navigation system combines automatic trajectory tracking and supervisor safe trajectory generation subsystems. Automatic trajectory tracking method, using line-of-sight (LOS) reference course generation algorithm, is combined with model predictive control (MPC). Algorithm for MASS trajectory tracking, including cooperation with the dynamic system of safe trajectory generation is described. It allows for better ship control with steady state cross-track error limitation to the ship hull breadth and limited overshoot after turns. In real MASS ships path is defined as set of straight line segments, so transition between trajectory sections when passing waypoint is unavoidable. In the proposed control algorithm LOS trajectory reference course is mapped to the rotational speed reference value, which is dynamically constrained in MPC controller due to dynamically changing reference trajectory in real MASS system. Also maneuver path advance dependent on the path tangential angle difference, to ensure trajectory tracking for turns from 0 to 90 degrees, without overshoot is used. All results were obtained with the use of training ship in real–time conditions.
The increasing concern for the safety and sustainability of structures is calling for the development of smart self-healing materials and preventive repair methods. This research is carried out to investigate the extent of self-healing in normal-strength concrete by using
Sporosarcina aquimarina – NCCP-2716 immobilized in expanded perlite (EP) as the carrier. The efficacy of crack-healing was also tested using two alternative self-healing techniques, i.e. expanded perlite (EP) concrete and direct introduction of bacteria in concrete. A bacterial solution was embedded in EP and calcium lactate pentahydrate was added as the nutrient. Experiments revealed that specimens containing EP-immobilized bacteria had the most effective crack-healing. After 28 days of healing, the values of completely healed crack widths were up to 0.78 mm, which is higher than the 0.5 mm value for specimens with the direct addition of bacteria. The specimen showed a significant self-healing phenomenon caused by substantial calcite precipitation by bacteria. The induced cracks were observed to be repaired autonomously by the calcite produced by the bacteria without any adverse effect on strength. The results of this research could provide a scientific foundation for the use of expanded perlite as a novel microbe carrier and
Sporosarcina aquimarina as a potential microbe in bacteria-based self-healing concrete.
Readiness and reliability is a special attribute of rescue systems (army, police, fire service), where performance at the highest level is more important than economic efficiency. For this reason, special attention is given to the process of renewal of technical objects. In such systems, a preventive strategy is most often used. Though this is a safe model, it does not always take into account the specifics of the use of a technical object. Moreover, in some situations, it forces the end of life of a device that could still continue to operate as intended. The article analyzes precisely such technical objects, removed from operation after just 10 years of use. It was shown that such approach is not justified and that modern management strategies must be implemented also in relation to machinery and equipment operating in rescue systems. The most important achievements of the article are the use of reliability analysis methods in the systems where it is not common, and the indication of the benefits of such analysis. It has been shown that knowing the characteristics of reliability, you can consciously control each process and make decisions in this regard based on the technical condition of the facility and not on instructions. In the case under study, this would make it possible to undermine the decision to withdraw the analyzed objects from operation.
The article presents the results of research on polymer composites based on polypropylene filled with various fillers. The physical and thermal properties of the composites are the result of the used polymer matrix as well as the properties and geometric features of the used filler. The geometric shape of the filler is particularly important in the processing of plastics in which the flow is forced, and high shearing tension occurs, which determines the high macromolecular orientation and specific arrangement of the filler particles. Thermal analysis (STA) was used in the research and photographs were taken using a scanning electron microscope (SEM) of fractures of polymer composites. The following fillers were used: talc, fibreglass, glass beads, and a halogen-free nitrogen-phosphorus flame retardant. The test material was obtained by extrusion. Shapes for strength tests, which were subjected to scanning microscopy tests after a static tensile test, were obtained by injection. The carried-out tests allowed us to determine the influence of the type and shape of individual fillers on structural changes in the structure of polypropylene composites and the degree of sample weight loss in a specific temperature range, depending on the used filler.
The present work investigated the properties of rubber vulcanizates containing different nanoparticles (Cloisite 20A and Cloisite Na+) and prepared using different sonication amplitudes. The results showed that a maximum improvement in tensile strength of more than 60% over the reference sample was obtained by the nanocomposites containing 2 wt.% Cloisite 20A and 1 wt.% Cloisite Na+ and mixed with a maximum amplitude of 270 µm. The modulus at 300% elongation increased by approximately 18% and 25% with the addition of 2 wt.% Cloisite 20A and 3 wt.% Cloisite Na+, respectively. The shape retention coefficient of rubber samples was not significantly affected by the mixing amplitude, while the values of the softness measured at the highest amplitude (270 µm) were higher compared to those of mixtures homogenized with lower amplitudes. The loading-unloading and loading-reloading processes showed similar trends for all tested nanocomposites. However, they increased with increasing levels of sample stretching but were not significantly affected by filler content at a given elongation. More energy was dissipated during the loading-unloading process than during the loading-reloading. SEM micrographs of rubber samples before and after cycling loading showed rough, stratified, and elongated morphologies. XRD results showed that elastomeric chains were intercalated in the MMT nanosheets, confirming the improvement of mechanical properties. The difference between the hydrophilic pristine nanoclay (Cloisite Na+) and organomodified MMT (Cloisite 20A) was also highlighted, while the peaks of the stretched rubber samples were smaller, regardless of the rubber composition, due most probably to the decrease of interlayer spacing.
The high pressure die casting (HPDC) is a technique that allows us to produce parts for various sectors of industry. It has a great application in such sectors as automotive, energy, medicine, as the HPDC allows us to produce parts very fast and very cheaply. The HPDC casting quality depends on many parameters. The parameters among others, are cast alloy alloy metallurgy, filling system design, casting technology elements geometry and orientation, as well as, machine operation settings. In the article, different plunger motion schemes of the HPDC machine were taken into account. Analyses lead to learning about plunger motion influence on the casting porosity and solidification process run. Numerical experiments were run with the use of MAGMASoft® simulation software. Experiments were performed for industrial casting of water pump for automotive. Main parameter taken into account was maximal velocity of the plunger in the second phase. The analysis covered porosity distribution, feeding time through the gate, temperature field during whole process, solidification time. Cooling curves of the casting in chosen points were also analysed. Obtained results allow us to formulate conclusions that connect plunger motion scheme, gate solidification time and the casting wall thickness on the solidification rate and porosity of the casting.
The paper presents a proposition of the theoretical-experimental method of determination of power losses in the transversely vibrating rubber V-belt of continuously variable transmission. The article comprises the results of experimental tests conducted on a special test stand with a complete scooter drivetrain powered by a small two-stroke internal combustion engine. Such a configuration allows ensuring real CVT working conditions. A high-speed camera was used for the contactless measurement of belt vibrations and time-lapse image analysis was performed in dedicated software. An axially moving Euler–Bernoulli beam was assumed as the mathematical model. Longitudinal vibrations and nonlinear effects were omitted. Additionally, it was assumed that the belt material behaves according to the Kelvin–Voigt rheological model. Analysis of the damped free vibrations of the cantilever beam, made of the belt segment, allowed to determine the equivalent bending damping coefficient. The CVT power losses, due to bending in the rubber transmission belt, were obtained for the fixed working conditions after numerical calculations. The proposed methodology is a new approach in this research area, which allows to obtain results impossible to achieve with other measurement methods.
In the paper we compare the geometric descriptions of the deformed sphere (i.e., the so-called λ-sphere) and the standard spheroid (namely, World Geodetic System 1984’s reference ellipsoid of revolution). Among the main geometric characteristics of those two surfaces of revolution embedded into the three-dimensional Euclidean space we consider the semi-major (equatorial) and semi-minor (polar) axes, quartermeridian length, surface area, volume, sphericity index, and tipping (bifurcation) point for geodesics. Next, the RMS (Root Mean Square) error is defined as the square-rooted arithmetic mean of the squared relative errors for the individual pairs of the discussed six main geometric characteristics. As a result of the process of minimization of the RMS error, we have obtained the proposition of the optimized value of the deformation parameter of the λ-sphere, for which we have calculated the absolute and relative errors for the individual pairs of the discussed main geometric characteristics of λ-sphere and standard spheroid (the relative errors are of the order of 10−6 – 10−9). Among others, it turns out that the value of the,sup>
flattening factor of the spheroid is quite a good approximation for the corresponding value of the deformation parameter of the λ-sphere (the relative error is of the order of 10−4).
Over the past two decades, numerous research projects have concentrated on cognitive radio wireless sensor networks (CR-WSNs) and their benefits. To tackle the problem of energy and spectrum shortfall in CR-WSNs, this research proposes an underpinning decode-&-forward (DF) relaying technique. Using the suggested time-slot architecture (TSA), this technique harvests energy from a multi-antenna power beam (PB) and delivers source information to the target utilizing energy-constrained secondary source and relay nodes. The study considers three proposed relay selection schemes: enhanced hybrid partial relay selection (E-HPRS), conventional opportunistic relay selection (C-ORS), and leading opportunistic relay selection (L-ORS). We present evidence for the sustainability of the suggested methods by examining the outage probability (OP) and throughput (TPT) under multiple primary users (PUs). These systems leverage time switching (TS) receiver design to increase end-to-end performance while taking into account the maximum interference constraint and transceiver hardware inadequacies. In order to assess the efficacy of the proposed methods, we derive the exact and asymptotic closed-form equations for OP and TPT & develop an understanding to learn how they affect the overall performance all across the Rayleigh fading channel. The results show that OP of the L-ORS protocol is 16% better than C-ORS and 75% better than E-HPRS in terms of transmitting SNR. The OP of L-ORS is 30% better than C-ORS and 55% better than E-HPRS in terms of hardware inadequacies at the destination. The L-ORS technique outperforms C-ORS and E-HPRS in terms of TPT by 4% and 11%, respectively.