Tom 71 (2020): Zeszyt 3 (June 2020)

In this paper, based on the fusion of Lidar and Radar measurement data, a real-time road-Object Detection and Tracking (LR_ODT) method for autonomous driving is proposed. The lidar and radar devices are installed on the ego car, and a customized Unscented Kalman Filter (UKF) is used for their data fusion. Lidars are accurate in determining objects’ positions but significantly less accurate on measuring their velocities. However, Radars are more accurate on measuring objects velocities but less accurate on determining their positions as they have a lower spatial resolution. Therefore, the merits of both sensors are combined using the proposed fusion approach to provide both pose and velocity data for objects moving in roads precisely. The Grid-Based Density-Based Spatial Clustering of Applications with Noise (GB-DBSCAN) clustering algorithm is used to detect objects and estimate their centroids from the lidar and radar raw data. Then, the estimation of the object’s velocity as well as determining its corresponding geometrical shape is performed by the RANdom SAmple Consensus (RANSAC) algorithm. The proposed technique is implemented using the high-performance language C++ and utilizes highly optimized math and optimization libraries for best real-time performance. The performance of the UKF fusion is compared to that of the Extended Kalman Filter fusion (EKF) showing its superiority. Simulation studies have been carried out to evaluate the performance of the LR ODT for tracking bicycles, cars, and pedestrians.

Multiple sound source localization in noisy and reverberant conditions is one of the important challenges in the speech signal processing. The aim of this article is three-dimensional sound source localization in undesirable scenarios. For the localization algorithms, the spatial aliasing is one of the destructive factors in reducing the accuracy. Firstly, a 3D quasi-spherical nested microphone array (QSNMA) is proposed for eliminating the spatial aliasing. Since the speech signal has the windowed-disjoint orthogonality property, the speech information differs in terms of the frequency bands. Then, the Gammatone filter bank is introduced for the speech subband processing. In the following, the multiresolution steered response power (SRP) algorithm is adaptively implemented on subbands with the phase transform (PHAT)/maximum likelihood (ML) weighted functions based on the levels of the noise and reverberation. The peaks of the multiresolution adaptive SRP (MASRP) algorithm are extracted in each subband based on the number of speakers for continuous time frames. Finally, the distribution of these peaks are calculated in each subband and they are merged by the use of weighted averaging method. The final 3D speakers locations are estimated by extracting the peaks in the final distribution. The proposed QSNMAMASRP(PHAT/ML) algorithm is evaluated on real and simulated data for 2 and 3 simultaneous speakers in noisy and reverberant conditions. The proposed method is compared with SRP-PHAT, spectral source model-deep neural network, and spherical harmonic temporal extension of multiple response model sparse Bayesian learning algorithms on different range of signal-to-noise ratio and reverberation time. The mean absolute estimation error, averaged standard deviation for absolute estimation error, and computational complexity results show the superiority of the proposed method.

In large-scale power systems, the wide-area damping controller (WADC) using remote input signals is an effective device that can be applied to deal with poor inter-area oscillation damping. However, its control effect will be degraded by communication uncertainties such as variable time delays in both input and output sides of WADC, partial and complete communication failures. This paper focuses on a new WADC design by regarding communication uncertainties. Such uncertainties are mathematically formulated and analyzed in order to signify its impact on the oscillatory stability. The signal restoration of input and output pairs of WADC is proposed to alleviate an adverse effect of communication uncertainties. Simulation study in an IEEE 50-machine 145-bus test system elucidates that the proposed WADC is superior to that of the conventional WADC without considering communication uncertainties in both performance and robustness.

Estimation of the direction-of-arrival (DOA) and parameters of polynomial phase signal (PPS) impinging on the uniform linear array (ULA) of sensors in heavy-tailed noise environments is considered in this paper. To estimate signal parameters, a recently proposed quasi maximum-likelihood (QML) estimator is adopted. The proposed algorithm consists of two successive steps: (1) noise influence mitigation by using the proposed normalization strategy and (2) signal parameters estimation using the DOA-QML approach. The algorithm performance is evaluated for both monocomponent and multicomponent signals.

The aim of this paper proposes an orthogonal frequency-division multiplexing (OFDM) with network coding to improve the error performance of the system when the messages are transmitted from user to receiver. Two-way relay (TWR) networks are applied to reduce the transmission time slots. The exclusive-OR (XOR) coding is used for network coding in which source nodes exchange their information via TWR nodes. The XOR coded bits provides redundancy to achieve the transmit diversity gain which improves the error performance of the TWR network. OFDM is exploited for TWR to obtain the frequency selective fading nature of wireless channels. The different modulation schemes such as Quadrature Phase Shift Keying (QPSK), 16-Quadrature Amplitude Modulation (QAM) and 64-QAM with OFDM system are simulated and QPSK is selected as it gives the lowest bit error rate (BER). The multiple relaying schemes with different numbers of the information packets are also considered in this paper. Simulation results show that multiple relay schemes provide faster transmission time and better error rate performance. Moreover, different kinds of channel coding schemes such as Convolutional, Reed-Solomon (RS) and turbo codes are applied in OFDM system with network coding to compare and evaluate the BER performance of the proposed system. From the simulation results, network coded OFDM scheme with turbo codes give better BER performance for given Signal-to-Noise Ratio (SNR) in relaying scheme with different numbers of information packets compared to those of convolutional and RS codes. It shows that, the error rate performance and transmission time is reduced 10 percent than the conventional scheme at even at low SNR value.

Slotless permanent magnet machines theoretically do not produce any cogging torque, provided the stator inner surface reluctance remains unchanged. However, a cogging torque may occur due to a change in the electromagnetic design following material cost reduction in the manufacturing process. When the electromagnetic design is changed to reduce the waste in the manufacturing process (stamping of the laminations) by dividing the stator toroidal ferromagnetic core into two equal parts, gluing them together introduces a very small non magnetic gap between them, which affects the stored magnetic energy along the circumference and consequently gives rise to occurrence of a cogging torque. Using the finite element method its value is analyzed analytically and verified by a laboratory measurement. Results of our work, presented in this paper, will help scientists and engineers to understand and avoid the causes for the occurrence of the cogging torque in designing slotless permanent magnet machines, where the design itself is subjected to the manufacturing process.

In this work, signal space diversity (SSD) method is exploited for a simple two-way relay channel (TWRC) with two end users mutually exchanging information. In order to ensure simplicity, the same rotation angle and interleavers are used under SSD framework. Also the well known decode-and-forward (DF) and amplify-and-forward (AF) protocols are adapted for the proposed TWRC. The analytical symbol error rate (SER) performance of the proposed scheme is evaluated for DF and AF protocols individually and evaluated through simulation results. The proposed scheme is shown to improve the performance of TWRC in terms of SER for both two protocols.

MIMO radars employ multiple transmitting and receiving antennae. For each transmitting antenna, an independent and easily distinguishable signal is required, and appropriate filters must be used by the receiver. For this, the transmitted signals should have characteristics, enabling their effective separation. In this paper the correlation characteristics of selected signals are compared, and the appropriate signal coding is suggested. For differentiation, we address signals with basic linear or nonlinear frequency modulation (LFM or NLFM) multiplied by Gold, PRN, or frequency diversity (FD) codes. The analysis shows that better signal characteristics are achieved using the FD than the other codes. Using matched filters with filter length of 511, sidelobes and cross-correlations are suppressed by 40 dB with FD codes, while with the other codes only 20 dB was achieved. It was also proven, that the FD codes are more tolerant to the Doppler shift. On the other hand, the FD codes application leads to an extension of the overall transmitted signal bandwidth. This however, only represents a serious barrier for very broadband radar systems.

A compact microwave lowpass filter based on defected ground structure (DGS), consisting of Yagi slot DGS resonators etched on the metallic ground plane of a microstrip line, is studied in this paper. The proposed lowpass filter was analyzed by parameter sweeping and optimal parameters were selected to design a prototype demonstrator filter. Measurements show the developed lowpass filter exhibits a 3dB cuto frequency of 3.07 GHz with a sharp transition between the passband and the stopband, low insertion loss of less than 0.6 dB in the passband and an in-band group delay of 0.4 ns. Moreover, an ultra-wide suppression band from 3.68 to over 20 GHz with a suppression level generally better than 20 dB is also observed from measurements.

The Gaussian multiple-input multiple-output (MIMO) orthogonal relay channel (ORC) is investigated. The transmission from source to relay is done over a channel that is orthogonal to source-destination and relay-destination channels. Practically, this assumption is made such that many communication devices from different technologies are exploited in relaying the source’s signal into its destination. For this channel model, the capacity is initially derived. Thereafter, we propose a transmission algorithm to achieve the derived capacity. Further, to support our theoretical results, many numerical examples are presented.