Bulletin of the Polish Academy of Sciences Technical Sciences

The paper describes a nonlinear controller design technique applied to a servo drive in the presence of hard state constraints. The approach presented is based on nonlinear state-space transformation and adaptive backstepping. It allows us to impose hard constraints on the state variables directly and to achieve asymptotic tracking of any reference trajectory inside the constraints, despite unknown plant parameters. Two control schemes (with and without integral action) are derived, investigated and then compared. Several examples demonstrate the main features of the design procedure and prove that it may be applied in case of motion control problems in electric drive automation.

The article proposes a new method of reproducing the angular speed of the rotor of a cage induction machine designed for speed observers based on the adaptive method. In the proposed solution, the value of the angular speed of the rotor is not determined by the classical law of adaptation using the integrator only by an algebraic relationship. Theoretical considerations were confirmed by simulation and experimental tests.

In this paper an application of extended Kalman filter (EKF) for estimation and attenuation of periodic disturbance in permanent magnet synchronous motor (PMSM) drive is investigated. Most types of disturbances present into PMSM drive were discussed and described. The mathematical model of the plant is presented. Detailed information about the design process of the disturbance estimator was introduced. A state feedback controller (SFC) with feedforward realizes the regulation and disturbance compensation. The theoretical analysis was supported by experimental tests on the laboratory stand. Both time- and frequency-domain analysis of the estimation results and angular velocity were performed. A significant reduction of velocity ripple has been achieved.

This paper presents a state feedback controller (SFC) for position control of PMSM servo-drive. Firstly, a short review of the commonly used swarm-based optimization algorithms for tuning of SFC is presented. Then designing process of current control loop as well as of SFC with feedforward path is depicted. Next, coefficients of controller are tuned by using an artificial bee colony (ABC) optimization algorithm. Three of the most commonly applied tuning methods (i.e. linear-quadratic optimization, pole placement technique and direct selection of coefficients) are used and investigated in terms of positioning performance, disturbance compensation and robustness against plant parameter changes. Simulation analysis is supported by experimental tests conducted on laboratory stand with modern PMSM servo-drive.

In this paper, the issue related to control of the plant with nonconstant parameters is addressed. In order to assure the unchanged response of the system, an adaptive state feedback speed controller for permanent magnet synchronous motor is proposed. The model-reference adaptive system is applied while the Widrow-Hoff rule is used as adjustment mechanism of controller’s coefficients. Necessary modifications related to construction of the cost function and formulas responsible for adjustment of state feedback speed controller’s coefficients are depicted. The impact of adaptation gain, which is the only parameter in proposed adjustment mechanism, on system behaviour is experimentally examined. The discussion about computational resources consumption of the proposed adaptation algorithm and implementation issues is included. The proposed approach is utilized in numerous experimental tests on modern SiC based drive with nonconstant moment of inertia. Comparison between adaptive and nonadaptive control schemes is also shown.

The paper presents a method for designing a neural speed controller with use of Reinforcement Learning method. The controlled object is an electric drive with a synchronous motor with permanent magnets, having a complex mechanical structure and changeable parameters. Several research cases of the control system with a neural controller are presented, focusing on the change of object parameters. Also, the influence of the system critic behaviour is researched, where the critic is a function of control error and energy cost. It ensures long term performance stability without the need of switching off the adaptation algorithm. Numerous simulation tests were carried out and confirmed on a real stand.

In industrial drive systems, one of the widest group of machines are induction motors. During normal operation, these machines are exposed to various types of damages, resulting in high economic losses. Electrical circuits damages are more than half of all damages appearing in induction motors. In connection with the above, the task of early detection of machine defects becomes a priority in modern drive systems. The article presents the possibility of using deep neural networks to detect stator and rotor damages. The opportunity of detecting shorted turns and the broken rotor bars with the use of an axial flux signal is presented.

In this paper deep neural networks are proposed to diagnose inter-turn short-circuits of induction motor stator windings operating under the Direct Field Oriented Control method. A convolutional neural network (CNN), trained with a Stochastic Gradient Descent with Momentum method is used. This kind of deep-trained neural network allows to significantly accelerate the diagnostic process compared to the traditional methods based on the Fast Fourier Transform as well as it does not require stationary operating conditions. To assess the effectiveness of the applied CNN-based detectors, the tests were carried out for variable load conditions and different values of the supply voltage frequency. Experimental results of the proposed induction motor fault detection system are presented and discussed.

This paper presents simulation and laboratory test results of an implementation of an infinite control set model predictive control into a three-phase AC/DC converter. The connection between the converter and electric grid is made through an LCL filter, which is characterized by a better reduction of grid current distortions and smaller (cheaper) components in comparison to an L-type filter. On the other hand, this type of filter can cause strong resonance at specific current harmonics, which is efficiently suppressed by the control strategy focusing on the strict control input filter capacitors voltage vector. The presented method links the benefits of using linear control methods based on a space vector modulator and the nonlinear ones, which result in excellent control performance in a steady state as well as in a transient state.

The paper presents a novel model predictive flux control (MPFC) scheme for three-level inverter-fed sensorless induction motor drive operated in a wide speed region, including field weakening. The novelty of the proposed drive lies in combining in one system a number of new solutions providing important features, among which are: very high dynamics, constant switching frequency, no need to adjust weighting factors in the predictive cost function, adaptive speed and parameter (stator resistance, main inductance) estimation. The theoretical principles of the optimal switching sequence predictive stator flux control (OSS-MPFC) method used are also discussed. The method guarantees constant switching frequency operation of a three-level inverter. For speed estimation, a compensated model reference adaptive system (C-MRAS) was adopted while for IM parameters estimation a Q-MRAS was developed. Simulation and experimental results measured on a 50 kW drive that illustrates operation and performances of the system are presented. The proposed novel solution of a predictive controlled IM drive presents an attractive and complete algorithm/system which only requires the knowledge of nominal IM parameters for proper operation.

Most of the basic control methods of the grid-connected converter (GCC) are defined to work with a sine wave grid voltage. In that case if the grid voltage is distorted by higher harmonics, the grid current may be distorted too, which, in consequence, may increase the value of the THD of the grid voltage. The paper deals with an improved finite control set model predictive control (FCS-MPC) method of an LCL-filtered GCC operating under distorted grid conditions. The proposed method utilizes supplementary grid current feedback to calculate the reference converter current. The introduced signal allows to effectively improve the operation when the grid is subject to harmonic distortion. The paper shows a simulation analysis of the proposed control scheme operating with and without additional feedback under grid distortions. To validate the practical feasibility of the proposed method an algorithm was implemented on a 32-bit microcontroller STM32F7 with a floating point unit to control a 10 kW GCC. The laboratory test setup provided experimental results showing properties of the introduced control scheme.

This paper presents an analysis and simulation studies of three-phase matrix converter with GaN HEMT bidirectional switches with predictive control of grid currents and converter output currents. Two methods of grid currents shaping are described and compared. The first method is based on calculations of instantaneous grid reactive power and the second one uses the active power of the load. The analyzed converter works with the resistive-inductive load, and from the grid side the LC filter with damping resistor has been used.

Distributed generation is an issue intensively studied in recent years. It concerns, among others protection systems of distributed generation units connected to electric power grids. The main goal of this paper is to present the issue of functional reliability of selected passive loss of mains (LoM) protection systems, i.e. methods of detecting island operation in distribution power grids, which are implemented in PV inverters installed in sample MV and LV grids, typical for Polish conditions. First, different methods of detecting island operation have been distinguished and shortly characterized. Some problems concerning their action have also been presented. Then commonly used passive methods of island grid operation detection have been described. Next sample distribution grid has been presented and chosen disturbances modelled in the grid to test mentioned passive methods have been defined. For each of the determined type of disturbance the dynamic simulation has been carried out, as well as voltage and frequency plots for two selected RES nodes have been recorded and observed. All considered passive methods of island grid operation detection have been implemented in a Matlab/Simulink environment. Models of RoCoF, U/OVP and U/ OFP algorithms have been presented in diagrams. Then, results of carried out extensive studies have been shown in tables and discussed. The results are a consequence of a realized research project concerning electric grids in rural areas. Summary, final conclusions, and future research possibilities constitute the last part of the paper. The conclusions are mainly concentrated on evaluation of action of passive methods of island operation detection as well as possibility of using the methods in Polish conditions, particularly in rural distribution grids.

The complexity of power system phenomena challenges power system protection testing to obtain the required adequacy of the testing environment. Hardware-in-the-loop simulation in real-time substantially increases testing capabilities. However, there is still the question of the availability of commercial solutions. To address the challenges, a new hardware-in-the loop system has been designed and implemented utilizing the easily available Matlab/Simulink environment and Linux RT Preempt OS. The custom software part prepared for the presented system is based on the Matlab/Simulink s-function mechanism, Embedded Coder toolbox and Advantech biodaq library as the interface for the utilized I/O cards. The simulator’s real-time performance limits on Linux RT Preempt have been verified, and it was shown that its performance is sufficient to conduct successful tests of protection relays. Consequently, a simple power system protection relay testing example is provided, including a discussion of results. Finally, it has been proven that the presented system can be utilized as a simpler and more accessible hardware-in-the-loop testing alternative to commercial simulators.

Commonly known DC-AC switching converters are commonly used in compensator branches. One example of this is a static synchronous compensator (STATCOM). It consists of a voltage source converter (VSC) and acts as an inverter with a capacitor as a DC power source. These compensators use the PWM switching scheme or space vector modulation (SVM) method. Both methods require the desired signal to be generated. In some cases, as during the synthesis of self-excited systems or active energy-compensators, it is necessary to perform the desired branch immittance, e.g. negative capacitance, inductance, resistance or irrational impedance. In such cases, it is necessary to control the universal branch on the basis of a formula. This article presents the implementation method for the convolutional type impedance operators.

Currently, overhead lines dominate in the Polish medium and low voltage distribution networks. Maintaining their high reliability constitutes a very important challenge, especially under the severely changing climate conditions. An overhead power line exposed to high ice and rime loads has been considered. Using the finite element method (FEM), mechanical reliability of the distribution infrastructure was examined under various atmospheric conditions. Loads under the stressful conditions of rime, ice and wind were determined for the weakest section of the 30 kV overhead line, which consisted of concrete poles and ACSR conductors. SAIDI and SAIFI reliability indices and costs were determined for several variants of object reconstruction. The results allowed for determination of a solution relying on relocating the cables of all lateral branches and main line ice protection, through a system based on a weather-coordinated increase of the electrical load. To verify the solution proposed, a field experiment was conducted. The experiment confirmed the effectiveness of the solution proposed that appears to be universal. The paper is a result of synergic cooperation of two academic teams, i.e. a mechanical and electrical power engineering one, and the distribution system operator (DSO).

This article aims to explain the capability of describing three-phase systems powered from the source with asymmetrical nonsinusoidal voltage waveforms. Indicating the physical components of the currents associated closely with specific physical phenomena facilitates separating the unbalanced components from the active and reactive ones. All those currents, excluding the active current and the scattered current, contribute to the existing unbalanced and reactive power. This article presents the decomposition of currents based on the Currents’ Physical Components Theory. When decomposing currents, it is assumed that the load is linear and unchanging in time, and the voltage supply is asymmetrical and nonsinusoidal.

The paper presents the issue of container handling processes at a railroad intermodal terminal. The main purpose of this paper is the assessment of the handling equipment utilization and the associated energy consumption. The authors analyze how the road vehicle availability at the moment specified in the containers loading schedule influences the total handling equipment operation time as well as the necessary number of handling equipment. It is assumed that vehicles planned for loading of import containers may be late for loading, which causes some interruptions in the loading schedule. Such interruptions are identified with the necessity to handle the next container for which the road vehicle is already waiting, which influences the handling equipment utilization and, finally, energy consumption. The general mathematical model of the problem developed in the FlexSim simulation software was presented. Based on the simulation research, it pointed out that proper road vehicles loading sequencing can significantly reduce handling equipment operation time, and thus energy consumption, costs, and CO₂ emissions. The literature analysis presented in the paper indicates that most of the research in the field of intermodal transport is focused on operations optimization in container ports. There are differences between two types of intermodal terminals in operation procedures and rules. That is why the authors decided to undertake the problem of road vehicle sequencing including their random availability and its influence on handling device operation time, which has not been considered in the literature so far.

The paper presents the analysis of strength and stiffness of metric threaded steel rods glued in glulam obtained by using two different gluing methods. The first method is used when the threaded steel rod is glued into a groove larger than the rod’s diameter, while the second method is applied when the diameter of the groove is smaller than the diameter of the threaded steel rod. The steel rod is covered with glue before it is inserted into the smaller diameter groove. The first method investigates the 2-mm-thick glue-line, while the second method analyses the contact when the groove’s diameter is 2 mm smaller than the outer diameter of the rod. Epoxy-type resin is used for both gluing methods. Different gluing methods present different interactions between the steel rod and glulam which result in different failure modes. The second method presents a plastic failure between the steel rod and glulam caused by the local compression and shear of glulam. The presented studies are made using metric threaded steel rods of diameters M12 and M16. In total, 20 specimens are experimentally tested in tension-to-tension tests performed according to EN 26891. The interaction between glulam and glued steel rods is also investigated using the 3D finite element modelling. The results obtained using the proposed 3D finite element model with different contact conditions between steel and glulam and the failure criterion for timber shear are well in line with the experimental findings.

The subject of the article is a comparison of two types of concrete carbonation models: self-limited carbonation and infinite carbonation. The results of the research on the progress of carbonation during six years of sample exposure in natural atmospheric conditions were used to determine the detailed models for a set of concretes with different w/c and different types of cement, and two scenarios of initial curing. It has been established that the model of self-limiting carbonation (i.e. hyperbolic) is more adequate for describing laboratory tests results in natural conditions.

The main objective of this article is to obtain equations of motion of the spin–stabilized projectile in the presence of non–constant wind. Introducing models allowing utilization of inhomogeneous wind is dictated by new possibilities created by the use of e.g. lidars in the Fire Control Systems (FCS). Constant feed of wind data can replace meteorological messages, increasing the FCS effectiveness. Article contains results of projectile flight simulations which indicate the positive effect that the derived explicit form of the model has when considering software development for modern Fire Control Systems.

The work discusses numerical and experimental researches, which are focused on developing a coherent model of magnetic interactions causing the levitation of the starting trolley of the unmanned aerial vehicle (UAV) catapult. The starting trolley is levitating over the catapult’s tracks, which generate the magnetic field. The levitation is made possible by the diamagnetic properties of high-temperature superconductors, placed in supports of the starting trolley. The introduction of the article briefly analyzes the catapult structure. Next, it explains the nature of associated with the Meissner and flux pinning effect magnetic interactions which causes the levitation phenomenon. The paper presents the results of numerical analysis of the magnetic field, generated by the catapult’s tracks arranged in two configurations: a “chessboard” and a “gutter” pattern. The numerical model was solved, using the finite element method. Parameterization of the numerical model was made based on the measurements of the magnetic field, generated by a single magnet.

Convenient human-computer interaction is essential to carry out many exhausting and concentration-demanding activities. One of them is cyber-situational awareness as well as dynamic and static risk analysis. A specific design method for a multimodal human-computer interface (HCI) for cyber-security events visualisation control is presented. The main role of the interface is to support security analysts and network operators in their monitoring activities. The proposed method of designing HCIs is adapted from the methodology of robot control system design. Both kinds of systems act by acquiring information from the environment, and utilise it to drive the devices influencing the environment. In the case of robots the environment is purely physical, while in the case of HCIs it encompasses both the physical ambience and part of the cyber-space. The goal of the designed system is to efficiently support a human operator in the presentation of cyberspace events such as incidents or cyber-attacks. Especially manipulation of graphical information is necessary. As monitoring is a continuous and tiring activity, control of how the data is presented should be exerted in as natural and convenient way as possible. Hence two main visualisation control modalities have been assumed for testing: static and dynamic gesture commands and voice commands, treated as supplementary to the standard interaction. The presented multimodal interface is a component of the Operational Centre, which is a part of the National Cybersecurity Platform. Creation of the interface out of embodied agents proved to be very useful in the specification phase and facilitated the interface implementation.

The paper presents new ensemble solutions, which can forecast the average level of particulate matters PM10 and PM2.5 with increased accuracy. The proposed network is composed of weak predictors integrated into a final expert system. The members of the ensemble are built based on deep multilayer perceptron and decision tree and use bagging and boosting principle in elaborating common decisions. The numerical experiments have been carried out for prediction of daily average pollution of PM10 and PM2.5 for the next day. The results of experiments have shown, that bagging and boosting ensembles employing these weak predictors improve greatly the quality of results. The mean absolute errors have been reduced by more than 30% in the case of PM10 and 20% in the case of PM2.5 in comparison to individually acting predictors.

This paper investigates whether a quantum computer can efficiently simulate the non-elastic scattering of the Schrödinger particle on a stationary excitable shield. The return of the shield to the ground state is caused by photon emission. An algorithm is presented for simulating the time evolution of such a process, implemented on standard two-input gates. The algorithm is used for the computation of elastic and non-elastic scattering probabilities. The results obtained by our algorithm are compared with those obtained using the standard Cayley’s method.

This paper presents the results of studies concerning the production and characterization of Al-SiC/W and Cu-SiC/W composite materials with a 30% volume fraction of reinforcing phase particles as well as the influence of corrosion and thermal shocks on the properties of selected metal matrix composites. Spark plasma sintering method (SPS) was applied for the purpose of producing these materials. In order to avoid the decomposition of SiC surface, SiC powder was coated with a thin tungsten layer using plasma vapour deposition (PVD) method. The obtained results were analysed by the effect of the corrosion and thermal shocks on materials density, hardness, bending strength, tribological and thermal properties. Qualitative X-ray analysis and observation of microstructure of sample surfaces after corrosion tests and thermal shocks were also conducted. The use of PVD technique allows us to obtain an evenly distributed layer of titanium with a constant thickness of 1.5 µm. It was found that adverse environmental conditions and increased temperature result in a change in the material behaviour in wear tests.

The aim of this study was to determine the hardness and reduced modulus of elasticity of juvenile wood of Scots pine (Pinus sylvestris L.) using the nanoindentation method, and then to compare the results obtained with those of mature wood. The hardness of juvenile pine wood determined by means of the nanoindentation method was 0.444 GPa while for mature wood it was 0.474 GPa. Statistically significant differences between the values were found. The reduced modulus of elasticity in juvenile wood was 14.0 GPa and 16.4 GPa in mature wood. Thus, the hardness values obtained were about 7% higher, while the modulus of elasticity was 17% higher in mature wood. All determinations were made in the S2-layer of the secondary cell wall.