In order to solve high torque ripple of permanent magnet synchronous motor (PMSM) for marine electric propulsion under the current control methods, the improved model predictive current control (MPCC) of PMSM for marine electric propulsion based on the mathematical model of three-phase PMSM is proposed. First, the stator current prediction model is derived based on the forward Euler method. Then the first optimal voltage vector is obtained by the value function, and the second optimal voltage vector, and the second optimal voltage vector and the first and second optimal voltage vectors' respective action times are obtained by the q-axis deadbeat control, which are directly fed back to the inverter. The proposed control method is verified by simulation and hardware in the loop simulation experiment. The experiment results show that, in comparison with the direct torque control based on space vector modulation (SVM-DTC) in the case of motor speed and torque mutation, the torque ripple of motor is reduced by 9.40% and 4.80% respectively based on improved MPCC. The feasibility and effectiveness of the proposed method are verified by the simulation and experiment results.
A deep learning-based approach in conjugation with Fourier Diffraction Theorem (FDT) is proposed in this paper to solve the inverse scattering problem arising in microwave imaging. The proposed methodology is adept in generating a permittivity mapping of the object in less than a second and hence has the potential for real-time imaging. The reconstruction of the dielectric permittivity from the measured scattered field values is done in a single step as against that by a long iterative procedure employed by conventional numerical methods. The proposed technique proceeds in two stages; with the initial estimate of the contrast function being generated by the FDT in the first stage. This initial profile is fed to a trained U-net to reconstruct the final dielectric permittivities of the scatterer in the second stage. The capability of the proposed method is compared with other works in the recent literature using the Root Mean Square Error (RMSE). The proposed method generates an RMSE of 0.0672 in comparison to similar deep learning methods like Back Propagation-Direct Sampling Method (BP-DSM) and Subspace-Based Variational Born Iterative Method (SVBIM), which produce error values 0.1070 and 0.0813 in the case of simulation (using Austria Profile). The RMSE level while reconstructing the experimental data (FoamDielExt experimental database) is 0.0922 for the proposed method as against 0.1631 and 0.1037 for BP-DSM and SVBIM, respectively.
To reduce the computational complexity of traditional model predictive torque control (MPTC) and improve the sensitivity of predictive control to disturbances, an improved three vector model predictive control strategy applied in permanent magnet synchronous motor (PMSM) is proposed. First, the principle of deadbeat synchronization between torque and flux linkage is adopted to reduce six candidate vectors in traditional torque prediction to two, and the cost function is designed to select the optimal voltage vector. In addition, disturbance observation compensation is introduced to compensate for the influence of load disturbance on the control performance of the predictive model. As experimental results show, the proposed three-vector model predictive torque control can obtain small torque ripple and current harmonics both in steady state and dynamic state.
Polarization is an essential feature of electromagnetic (EM) waves, and the variety and simplicity of polarization conversion have substantial demands in wireless systems. Metasurfaces, two-dimensional artificial electromagnetic structures, are emerging as novel modulation solutions for EM waves. In this work, a multifunction polarization converter based on a transmissive metasurface (MPC-TMS) is suggested. This planar structure is made up of a copper-clad dielectric substrate with top and bottom orthogonal slotted sheets joined by a metal via. With frequency selectivity, x- and y-linear cross-polarization transformations are efficiently achieved between 8.04-8.82 GHz (9.25%) and 7.04-9.07 GHz (25.19%), respectively. Meanwhile, the presented microstructure is capable of rotating a circularly polarized incident wave into its opposite handedness from 8.16 to 8.87 GHz (8.46%). Both peak transmission efficiency and the polarization conversion ratio exceed 0.95 simultaneously. In addition, resonance superposition and coupling effects are investigated to explain the operating mechanism. This microstructure not only has a simple construction with an ultra-thin thickness (0.06λ), but also reveals superiorities in bandwidth, transmission, and efficiency. To verify the above quadruple polarization conversion, measurement has been implemented, and the results are reasonably accordant with simulation, suggesting that the low-profile converter is conducive to future telecommunication design where polarization diversity is needed.
Wearable textile antenna is most appropriate for Wireless Body Area Network (WBAN) applications due to its flexibility, compactness, and user compatibility. Dual band antenna has advantage in duplex communication, hence it is desirable. In this paper, a dual band microstrip antenna is designed using textile material as a substrate with a circular patch and a rectangular patch Methods from literature and experimentation are compared based on performance parameters. Slots are loaded on the patch to achieve dual-band characteristics. HFSS software has been used to simulate the proposed antenna, and the results are compared with the fabricated antenna based on Voltage Standing Wave Ratio (VSWR), directivity, return loss, gain, impedance, and radiation pattern. Since the antenna operates with close proximity to the human body, the Specific Absorption Rate (SAR) is also calculated using the CST software and is found within the prescribed limits.
In this brief, an ultra-vast stopband lowpass filter with miniaturized circuit size for 26th harmonic suppression using poly-resonators and an inclined stepped-impedance transmission line (ISTL) is developed. The poly-resonators such as radial stub resonator and resonator modules constitute the significant part of the filter, and the discontinuity in the inclined angle of the ISTL is balanced by 75% chamfering. The coupling with ISTL has influence over the stopband behavior, and the equivalent circuit for the first transmission zero is analysed. The normalised circuit size is reduced to 16.6%, and additional frequency rejection is achieved using resonator modules RM1 and RM2. The relative stopband width of 185.4% is attained with a 3 dB cut-off frequency of 1.51 GHz. L band communication applications having circuit area limitations can make use of the Poly-resonator ISTL filter for achieving high-frequency noise rejection.
This paper outlines the design characterization and the electromagnetic performance of a millimeter-wave high power combining structure, which exploits the spatial power combination technique. The input matching is always below 10 dB over the entire Q band, and the overall weight of the structure is about 500 g. Multiphysics simulations show how this structure is suitable for the most challenging space missions that will arise in next few years. In fact, 100 W of RF power above the frequency of 40 GHz can be delivered while all the specifications for satellite payloads are complied. Other Spatial Power Combiner structures, such as Radial ones, cannot be implemented in space missions since they are much less compact and much heavier than the one presented in this article, and this is the major advantage of this configuration which was specially designed for a space project.
A novel EBG structure in the form of a square spiral cell with a via at its middle is presented in this work to improve the isolation between the antenna elements and also enhance the overall parameters of the proposed MIMO system. Wide BW is achieved for the 6-elements MIMO system operating in the frequency range from 3 GHz to 5 GHz which is suitable for 5G mobile applications. The single antenna element consists of four coupled sections printed on an FR4 substrate. To improve the performance and maintain the BW, the EBG structure is employed to increase the isolation between the antenna elements. The proposed EBG is designed to have a bandgap from 2.5 GHz to 6.5 GHz. The addition of the EBG structure between the radiating elements reduces the envelope correlation coefficient across the whole operating BW. SAR calculations are also performed using head and hand models. The performance of the proposed EBG loaded MIMO antenna is suitable to be a potential competitor for future 5G applications.
Arc synthetic aperture radar (ArcSAR) forms the synthetic aperture through uniform circular motion with antenna pointed outwards circular trajectory, so the point target response is different from traditional linear SAR and Circular SAR (CSAR). Due to the unique imaging mode, ArcSAR has the characteristics of large field of view and constant azimuth angular resolution. The ArcSAR system is built by vector network analyzer (VNA), rotating platform, standard gain horn antenna, and computer, and the system transmits stepped frequency continuous wave (SFCW). A Qt-based GUI is designed to realize the accurate and convenient remote control of the system. An outdoor imaging experiment was carried out with a corner reflector to investigate the point target response of SFCW-ArcSAR which has unique forms in Cartesian coordinate and cylindrical coordinate systems. In order to avoid the additional phase error introduced by coordinate transformation based on interpolation, back projection (BP) algorithm is applied in Cartesian coordinate system and cylindrical coordinate system, respectively. The point target response presents a 2-D sinc function in cylindrical coordinate system. The azimuth angular resolution is 0.0175 rad under the experimental condition of 1.9 m-rotating radius and 16˚ antenna beamwidth. The simulation results agree with measured ones, which prove the validity of SFCW-ArcSAR system and correctness of theoretical analysis. The imaging result based on BP algorithm and corner reflector can be used to evaluate other ArcSAR imaging algorithms.
A circular polarization multiplexing metasurface beam splitter operating at 15 GHz with polarization conversion effect is proposed. The unit cell is formed by alternately stacking 4 layers of metal and 2 layers of dielectric substrates cascaded along the propagation direction, separated by air. The resonant phase of the unit cell can be changed by changing the size parameters of the two arms of the metal cross patch, and the phase coverage of nearly 360° can be achieved in the direction of the two orthogonal linear polarization components, while transmission coefficient is above 85%. The circular polarization geometric phase covering 360° can be achieved by rotating the metal patch. The polarization conversion of the circularly polarized wave can be realized by setting the phase difference of the two orthogonal linear polarization components to 180°, and the polarization conversion ratio (PCR) at the working frequency is greater than 90%. The simulation and test results show that when the circularly polarized electromagnetic wave is perpendicularly incident on the metasurface beam splitter, the transmitted wave is divided into two circularly polarized waves with different exit angles and orthogonal to the polarization direction of the incident wave. This work may provide new ideas for the integration and miniaturization of traditional beam splitting devices and have important application prospects in fields such as multiple input multiple output (MIMO) systems.
A new compact CPW fed dual-band circularly polarized (CP) antenna for a broadcasting satellite application is presented. The proposed dual-band CP antenna consists of modified CPW ground structure by loading stub/slots/inverted L-strip and modified cross-shaped patch. A modified CPW ground structure can generate circular polarization (CP). The proposed antenna design provides the simulated impedance bandwidth (IBW) (S11 < -10 dB) of 81.42% (3.16-7.5 GHz) and 20.53% (11.8-14.5 GHz), respectively, and the 3-dB axial ratio BW (3-dB ARBW) for two bands are 29% (4.18-5.6 GHz) and 8.86% (11.86-12.96 GHz), respectively. The proposed CP antenna provides a maximum gain about 3.8 dBi and 5 dBi in lower and upper bands, respectively, with right hand circular polarization (RHCP) radiations. The overall size of the CP antenna is 27 × 27 × 1 mm3.
Magnetic gear has high torque density and efficiency, and has a good application prospect in the field of low speed and high torque transmission. Accurate calculation of its air gap magnetic field is the key to analyze and design the magnetic gear. In order to improve the output torque of magnetic gear, the inner rotor is slotted, and copper bar is added in this paper. The air gap magnetic field of magnetic gear with rotor copper bar is calculated by two-dimensional analytical method. The solution domain is divided into four sub-domains, i.e., permanent magnets, air gaps, slots, and rotor copper bars. The solutions of Laplace's equation, Poisson's equation, and Helmholtz's equation are obtained by boundary conditions and continuity conditions. The distributions of air gap magnetic field, the induced current of rotor copper bars, and electromagnetic torque are obtained. The calculation results of this method are basically consistent with those of the finite element method, which proves the correctness and rationality of the analytical model.
This study provides an alternative and straightforward approach to determining buried dielectric objects underground by employing the method of auxiliary sources. In the direct scattering problem, the Brewster angle is determined, and then the electromagnetic properties of the ground are determined. Later, the scattered field above the ground due to the buried object is evaluated. The localization of the buried object is obtained by the continuity of the field components while solving the inverse problem. The numerical experiments are done, and outcomes of the numerical experiments are compared with a commercial full-wave computational electromagnetic software. The outcomes reveal less than 1% deviation between the proposed approach and the commercial tool.
The impact of permanent magnet (PM) properties such as magnetremanence and coercive force or coercivity on the electromagnetic output of flux-switching permanent magnet machine having C-core stator topology is presented and compared in this work. A two-dimensional finite-element analysis (2D-FEA) approach is implemented using ANSYS-MAXWELL software package. Three-dimensional (3D) FEA calculations are also conducted, in order to realize more accurate results, and its results are compared with the 2D-FEA predicted results. The investigated machine elements are: airgap flux-density, torque ripple, total harmonic distortion (THD) of the voltage, cogging torque, unbalanced magnetic pull (UMP) or force, winding inductances, direct- and quadrature-axis flux, electromotive force and output torque. The analyses show that undesirable qualities such as large amount of cogging torque and UMP are predominant in the machine having rare-earth magnets i.e. neodymium and samarium-cobalt, although they have larger flux linkage and superior average torque compared to its non-rare-earth magnet equivalents i.e. the ferrite- and alnico-made machines. Moreover, the alnico- and ferrite-made machines exhibit larger winding inductance values, and consequently lower saturation withstand capability, though with better field-weakening capability. Further, the predicted efficiencies of the compared machine types having alnico, ferrite, neodymium and samarium materials, at rated current and speed conditions are: 79.8%, 75.76%, 87.22% and 86.58%, respectively. More so, the generated electromagnetic output power of the compared machine types at the operating base speed is: 206.57 Watts, 186.57 Watts, 449.67 Watts and 396.40 Watts, respectively. The investigated machine is suitable for high torque in-wheel direct-drive applications.
A novel ultra-wideband (UWB) antenna with triple band rejection capabilities operating in quad bands is presented. The proposed UWB antenna is derived from a planar rectangular shaped monopole antenna. In order to improve the bandwidth ratio of the antenna, a partial ground is maintained with a slot at centre along with truncated slots made at bottom two corners and a rectangular slot at top side centre of the radiating patch. In order to achieve the required triple notch characteristics and the multiband operation, a single meander line slot is made in the middle of the patch. The dimensions of the meander line slot are varied to change the notch band characteristics of the antenna. The FR4 substrate with dielectric constant 4.4 with thickness of 1.6 mm is used to design the antenna. The overall size of the antenna is maintained compact with dimensions 40 mm×38 mm. The proposed UWB antenna rejects triple bands 3.29 GHz-4.83 GHz (WiMAX), 5.15 GHz-6.84 GHz (WLAN), & 7.94 GHz-8.49 GHz (X-band satellite uplink). The operational bands of the UWB antenna with triple notch bands are as follows, 2.38 GHz-3.29 GHz, 4.83 GHz-5.15 GHz, 6.84 GHz-7.94 GHz, and 8.49 GHz-13.15 GHz. The measured peak gains at 2.7 GHz, 5 GHz, 7.3 GHz, 8.7 GHz, and 11.5 GHz are 3.4 dBi, 2.8 dBi, 3.6 dBi, 3.3 dBi, & 3.88 dBi, respectively. The step-by-step implementation of the triple notch band UWB antenna and the comparative analysis is presented. The proposed antenna performance is presented with the help of reflection coefficient, VSWR, gain, field distributions and radiation pattern curves. The simulated and measured analysis comparison shows good agreement making the designed antenna a good candidate for UWB applications that require multiband operations with selected bands rejection.
Six-pole hybrid magnetic bearing is a multiple input-output system with strong coupling between the degrees of freedom, a state feedback linearization dynamically decoupling the fuzzy immune PID controller for the subsystem after linear resolution coupling is proposed in this paper. Firstly, the basic theory of linear resolving coupling is expounded. Secondly, the proposed decoupling theory and control strategy are simulated in Matlab. Finally, the experimental platform is built, and the suspension experiments and coupling experiments are performed. It can be seen that the fuzzy immune PID controller has good performance, and the state feedback linearization method can realize the decoupling between the radial degrees of freedom of six-pole magnetic bearings.
This paper proposes a novel miniaturized interdigital capacitor loaded interdigital filter, which is applied in C-band (3.2 GHz~4.2 GHz). By loading an interdigital capacitor on the open end of the resonator of the interdigital filter, the length of the resonator is shortened by 28%. The resonant frequency offset caused by tap introduction is adjusted by using the method of impedance compensation at the open end of resonator 1 and resonator 5, which further reduces the size of the filter. The miniaturized filter is fabricated on a 0.254 mm-thickness alumina substrate with relative dielectric constant of 9.8 by thin film process. Measured results are as follows: the passband of the filter is 3.2 GHz~4.2 GHz; the insertion at center frequency is -1 dB; the return loss is less than -18.3 dB. The size of the filter is 4.98 mm*6.45 mm (0.15λg*0.20λg), which is 37.8% smaller than that of the traditional interdigital filter.
This paper explores a loaded conductor backed coplanar waveguide (CB-CPW) split ring resonator (SRR) fed U-slot planar antenna used for healthcare monitoring via the wireless scientific industrial medical (ISM) band and medical service band at fifth generation (5G-MSB). The antenna has been designed with bio-tissue layers, muscle layers, skin, and fat. The parameters of the designed antennas, such as miniaturization, increased gain, and enhanced bandwidth, are presented. The proposed prototype results in the total size of 640 mm3. Such designed antenna has been operated at (3.4-3.6) GHz - fifth-generation medical service band and at (2.38-2.48) GHz - industrial scientific band and can realize proximately omnidirectional radiation pattern over the operating bands.
Based on the principle of bionics, this paper combines the design of flexible bionic antenna with Chinese culture, and proposes a dual-material bionic antenna with Electromagnetic Band Gap(EBG) structure. The antenna uses a polyimide flexible substrate. Radiation patch of this antenna is shaped like a ``pear flower'', and the ``CHINA'' shaped slot is etched on the ground to form a Logo mark. In order to reduce the impact of antenna radiation on human body, the introduction of an EBG structure made of Polydimethylsiloxane (PDMS) material makes the front-to-back ratio of the antenna radiation significantly increased. The antenna was bent in different ways and was placed on human body model for simulation and testing. The results showed that the antenna achieved an impedance bandwidth of 18.8% (2.22-2.46 GHz), the peak gain was 4.02 dBi, and the antenna was low sensitive to deformation, which makes it suitable for modern flexible electronic equipment.
Birds and bats are at risk when they are flying near wind turbines (WT). Hence, a protection of bats and birds is postulated to reduce their mortality e.g. due to collisions with the rotor-blades. The use of radar technology for monitoring wind energy installations is becoming increasingly attractive for WT operators, as it offers many advantages over other sensor systems. Timely localization and classification of the approaching animal species is very crucial about the reaction measures for collision avoidance. In this work, a localization, classification and flight path prediction technique has been developed and tested based on simulated radar signals. This allowed us to classify three different birds and one bat species with an accuracy of 90.18%. For accurate localization and target tracking, five frequency modulated continuous wave (FMCW) radars operating in Ka-Band were placed on the tower of the WT for 360˚ monitoring of the WT.