Volume 71 (2020): Issue 1 (February 2020)

Using the principles of Takagi-Sugeno fuzzy modelling allows the integration of flexible fuzzy approaches and rigorous mathematical tools of linear system theory into one common framework. The rule-based T-S fuzzy model splits a nonlinear system into several linear subsystems. Parallel Distributed Compensation (PDC) controller synthesis uses these T-S fuzzy model rules. The resulting fuzzy controller is nonlinear, based on fuzzy aggregation of state controllers of individual linear subsystems. The system is optimized by the linear quadratic control (LQC) method, its stability is analysed using the Lyapunov method. Stability conditions are guaranteed by a system of linear matrix inequalities (LMIs) formulated and solved for the closed loop system with the proposed PDC controller. The additional GA optimization procedure is introduced, and a new type of its fitness function is proposed to improve the closed-loop system performance.

It is necessary to find the suitable d - and q -axis reference currents to control PMA-SynRM motors with high efficiency. This paper presents the maximum torque per ampere (MTPA) to minimize the copper losses of the system and utilizes the field weakening control to operate above the rated speed of the PMA-SynRM. The copper losses equation and electromagnetic torque are used to optimize the d - and q -axis current references. A small-scale 1 kW prototype PMA-SynRM was designed and manufactured to test and examine the proposed control in the laboratory. The proposed algorithm was digitally carried out using the MicroLab Box dSPACE. The simulation results show that the copper losses of the machine with the MTPA algorithm are lower than those without the MTPA algorithm. The PMA-SynRM operates above the base speed of ~ 70 % in the constant power region by mean of field weakening control.

The regime of total internal reflection of plane wave on the boundary between a lossless dielectrics and the lossy, or gainy, medium is analysed. It is shown that in order to achieve enhanced total internal reflection (TIR), ie magnitude of the reflection factor larger than one, the existence of the second boundary, virtually maybe infinitely far away, is inevitable. Some contradictory results published in literature are discussed.

The work presents a physical model of trap-assisted tunnelling that allows assessing the impact of traps upon the total current through metal/semiconductor heterostructures. The model is based on expressing the occupation probability of the trapping centres by electrons in terms of thermal and tunnelling capture and emission times, commonly referred to as exchange times. The occupation probabilities calculated in this way are then used to evaluate the generation-recombination rates occurring in the continuity equations.

In field electron emission (FE) studies, it is important to check and analyse the quality and validity of experimental current-voltage data, which is usually plotted in one of a small number of standard forms. These include the so-called Fowler-Nordheim (FN), Millikan-Lauritsen (ML) and Murphy-Good (MG) plots. The Field emission orthodoxy test is a simple quantitative test that aims to check for the reasonableness of the values of the parameter “scaled field” that can be extracted from these plots. This is done in order to establish whether characterization parameters extracted from the plot will be reliable or, alternatively, likely to be spurious. This paper summarises the theory behind the orthodoxy test, for each of the plot forms, and confirms that it is easy to apply it to the newly developed MG plot. A simple, new, accessible web application has been developed that extracts scaled-field values from any of these three plot forms, and tests for lack of field emission orthodoxy.

This paper dealt with characteristics of partial discharge (PD) initiated by metallic particles under DC voltage in green gas for grid (g3), which is an emerging and promising eco-friendly alternative insulation gas to SF₆. Experimental setup was configured to simulate PD under DC in gas-insulated power facilities. Two types of particle, namely rectangle particle and sphere particle were used. The results indicated that the discharge inception voltages in g3 gas were 90.1-92.5% of that in SF₆. In two particles, PD occurred with higher average apparent charge and discharge repetition rate in g3 compared with those in SF₆ gas. The time-resolved partial discharge presented similar characteristics in g3 and SF₆ gas. The time interval between two successive discharge pulses were 0.1 ms-10 ms and 5 ms-15 ms in the rectangle particle and sphere particle, respectively. Results from this paper are expected to provide fundamental material for the development of SF₆ -free gas-insulated power apparatus.

We present the design of a tri-band E-shaped printed antenna with C-shaped slots. A Rectangular patch etched with an n-shaped slot is added at the back of the substrate to enhance the bandwidth and the return losses of the resonant bands - particularly, that of the second band. Our antenna is designed to operate at 1.51/2. 46/6.11 GHz. As can be observed from the experimental results, it has 10 dB bandwidths of 157 MHz (1.416 to 1.573 GHz) 358 MHz (2.221 to 2.579 GHz) and 367 MHz (5. 918 – 6. 285 GHz) The first two bands cover the LTE, Bluetooth, IEEE 802.15.4 ZigBee and IEEE 802.11 WLAN applications. The third resonant band covers the unlicensed 6 GHz band which is widely implemented in wireless power transmission, as well as, RFID and satellite communications. In order to ease wireless congestion, the 6 GHz band is also currently being considered by the FCC to be opened up for the use of WiFi applications. Our antenna is fabricated on a single-sided FR4-epoxy, and it constitutes a compact size of 34 mm × 36 mm × 1.6 mm or 0.17λ × 0.18λ times0.0081λ, (based on the 1.51 GHz lowest resonant frequency) The antenna exhibits omnidirectional radiation patterns at the three resonant bands.

A wideband transition from the coaxial TEM mode to the TM₀₁ mode of the circular waveguide with in-line input-output architecture is proposed in this paper. The transition employs multi-stage stepped impedance transformer to achieve wideband responses. Both mode transition and impedance matching characteristics are discussed in the paper. A demonstrator is developed and validated experimentally. As compared with some recently published reports, a better performance is observed. Moreover, the developed transition could facilitate the mechanical fabrication more easily. It can be found wide applications such as the circular waveguide based slot array antenna, the nondestructive detection, cracks inside the conductive pipes, and so on.

Kalman Filter (KF) is the most widely used estimator to estimate and track the states of target. It works well when noise parameters and system models are well defined in advance. Its performance degrades and starts diverging when noise parameters (mainly measurement noise) changes. In the open literature available researchers has used the concept of Fractional Order Kalman Filter (FOKF) to stabilize the KF. However in the practical application there is a variation in the measurement noise, which will leads to divergence and degradation in the FOKF approach. An Innovation Adaptive Estimation (IAE) based FOKF algorithm is presented in this paper. In order to check the stability of the proposed method, Lyapunov theory is used. Position tracking simulation has been performed for performance evaluation, which shows the better result and robustness.

Now-a-days Massive MIMO (mMIMO) become an attractive technology due to its spectral and energy efficiency by the means of simple signal processing. However, in overloaded scenario, wherein the number of users equipments (UEs) are larger than number of antennas, the spectral effciency (SE) suffers and hence error rate performance, it has been shown recently that use of code domain NOMA in mMIMO can improve the SE performance. Further, interleave division multiple access (IDMA) has been drawn much attention as a suitable code domain non-orthogonal multiple access (NOMA) for future communication standards. This paper proposes the work in two folds, first a massive multiple input and multiple output (MIMO) and IDMA communication system is jointly proposed in which antennas on the base station serves users simultaneously in the same frequency band. Both and are large in numbers. Secondly, the minimum mean square error (MMSE) based beamformer is suggested to combat the propagation loss and effect of multiple access interference (MAI), for massive MIMO-IDMA system under downlink communication constraints. With the help of simulation results, the performance of the proposed system with MMSE beamforming have been investigated in terms of BER vs SNR curve plot.