Offset Compensation Research Articles

The effects of DC offset in direct-conversion receivers for WLAN systems

In this paper, the effects DC offset in direct-conversion receivers for WLAN systems are analyzed using both experimental and simulation data. DC offset estimation is performed by using data-aided methods which are based on the short training sequence of WLAN preamble. In the simulations, DC offset and frequency offset estimations are carried out on the signals affected by frequency selective Rayleigh fading channel and additive white Gaussian noise. Estimation performance of the methods is compared for different SNR levels and frequency offset values in terms of mean square error. Experimental data which is in the form of WLAN packets and transmitted through a wireless channel is captured by using a software defined radio. The experimental performance of the DC offset compensation methods is evaluated in terms of transmission success ratio.

Clustering and Markov Model of Plug-In Electric Vehicle Charging Profiles for Peak Shaving Applications

The charging profiles of plug-in electric vehicles (PEVs) have large volatility. It has brought great challenges for aggregator to accurately complete load identification and aggregated configuration. Therefore, an analysis and configuration method of responsive capacity based on clustering and the Markov model are proposed in this paper. Firstly, the adaptive two-scale clustering algorithm based on spectral clustering (ATCSC) is applied to the clustering of charging piles. The offset compensation of the extreme points is used to form the distance measurement in the clustering process. Then, the responsive aggregated power can be obtained after the change control of suitable charging piles. Finally, the variation characteristics of the actual charging profiles based on the Markov model are introduced to the reliability evaluation in the load curtailment service. Simulation results reveal the following. (1) The robustness of the proposed method is better especially for the PEV charging profiles with strong volatility. (2) The validity of the aggregated configuration is verified. Additionally, the sum of power deviation is 0.0707 kW when the change interval of control strategy is 15 min. (3) The maximum shortage of configuration is −98.0875 kW as the entropy of the volatility is 37.027.

Adaptive 2D skeleton deformation based on view agnostic network for action recognition

Research in skeleton-based human action recognition has generated great interest from the computer vision community, owing to the feasibility and popularity of skeleton data. Some broadly used 2D pose estimation methods, which can be used to generate high-quality skeletons in real time using only low-power equipment, improve 2D skeleton-based action recognition. However, view variations in action representations influence their performance. In this paper, a view agnostic network for 2D skeleton-based action recognition, which narrows the representation differences in view variations by applying an adaptive frame-level skeleton deformation before feature extraction, is proposed. Specifically, the deformation is realized by a body-level affine transformation and a joint-level offset compensation, which aims to approximatively determine a new observation viewpoint for better intragroup consistency in a learning-based data-driven manner. Meanwhile, an adaptive spatial–temporal graph convolutional LSTM (ASTGCN-LSTM), which can model the co-occurrence relationship in the spatial–temporal domain for skeleton sequences more effectively, is introduced. Experiments are conducted on Kinetics-Skeleton and NTU120 RGB+D action recognition datasets, which are used to demonstrate the effectiveness of the proposed method.

A Reduced-Order Multisensor-Based Force Observer

This article proposes a reduced-order multisensor-based force observer (RMFOB) for accurately estimating the force exerted on a load. The RMFOB excels in high-frequency noise attenuation and low-frequency time-varying measurement offset compensation by using the combination of force sensor measurements, motor encoder measurements, and motor input signals, properly fused in a Kalman filter (KF) setting, in which the dynamics of the sensors and the system is taken into account. As part of the observer design, an estimator for the force measurement offsets is also derived, so that they can be visualized and quantified. Moreover, novel tools for analyzing the KF-based observer are introduced. To evaluate its performance, the RMFOB is then implemented in both simulations and experiments. Results show that the observer can produce the accurate force estimate by compensating for the time-varying measurement offsets and attenuating the high-frequency noises. Results are presented for various experimental conditions to thoroughly assess the capabilities of the proposed observer.

Cyber-Resilient Sliding-Mode Consensus Secondary Control Scheme for Islanded AC Microgrids

In this article, a cyber-resilient consensus-based distributed control scheme is proposed for islanded ac microgrids. Considering the impacts of false data injection (FDI) attacks on the conventional consensus algorithms, a hybrid solution is presented based on the combination of multiobjective sliding-mode control and communication link quality observer to provide a reliable performance against different types of FDIs. Unlike the commonly developed distributed observer-based cyber-resilient algorithms, this approach aims to form a complete localized solution without the requirements for transmission of extra distributed signals in the secondary layer. Using the proposed method, the system reliability will not be impacted by the cyber intrusions on the distributed observer terms, and the system's dynamic performance is not deteriorated by the counteracting operation resulted from adaptive distributed observers under other system-transient conditions such as load dynamics, which can be even worsened under communication delays. Using cyber-resilient offset compensation terms, performance of the proposed sliding-mode control scheme is enhanced for multiobjective regulation. Integrating the sliding-mode control with communication link observer also ensures effective isolation of the unbounded and extreme cyberattacks. Unlike the former indirect local observers, the proposed scheme operates directly based on monitoring the affected distributed signals rather than only power terms, which enhances its reliability on detection. The effectiveness of the proposed scheme is validated through a real-time model developed in Typhoon HIL-402 real-time simulator as well as the experimental tests.

Joint DFT Precoding and Discrete Wavelet Transform in SC-FDMA NOMA System with Carrier Frequency Offset Compensation

Joint DFT Precoding and Discrete Wavelet Transform in SC-FDMA NOMA System with Carrier Frequency Offset Compensation

Rotor Flux Estimator Design With Offset Extractor for Sensorless-Driven Induction Motors

In sensorless drive of induction motors (IMs), the design of a voltage model (VM) for flux estimation is challenging because of its inherent problems with dc saturation and drift. In the implementation of VM, various strategies have been studied in the flux estimator design. The closed-loop (CL) style flux estimator is a popular scheme owing to its good performance in a wide speed range. However, the CL style suffers from dc drift problems because of an offset at the back electromotive force. Based on the fact that dc drift always persists in the CL style flux estimator, this article proposes an offset extractor (OE) using a parallel structure of two CL style flux estimators. Moreover, a crossover strategy is applied to the comparative flux used in the CL scheme. This strategy guarantees low-speed operation including zero speed. When offset compensation using the proposed OE is applied to the flux estimator in a feedforward manner, the proposed flux estimator exhibits good performance in a wide speed range with robustness to the offset. Compared with the conventional methods, the proposed OE and flux estimator are verified in various situations by simulation and experiment in a sensorless-driven IM.

Current Measurement Offset Error Compensation in Vector-Controlled SPMSM Drive Systems

Current measurement offset errors occur in current sensors and related circuits, because of various factors, such as thermal drift, aging, and nonlinearity. The current offset error results in undesired torque ripples, which deteriorate the speed and torque control performances of vector-controlled drive systems. This study proposes an online current measurement offset error compensator for vector-controlled surface permanent magnet synchronous motor (SPMSM) drive systems. The proposed compensator requires only phase current sensors and no additional hardware. This method is applicable for all systems using two and three phase current sensors. The current offset error is estimated using the motor parameters, stator current, and command voltage in the stationary reference frame. This scheme can continuously adjust the current offset during motor operation. In addition, this study analyzes the effect of parameter errors and confirms that the proposed method is robust to variations in the machine parameters. Simulation and experimental results are provided to verify the performance of the proposed current measurement offset error compensation method.

A Receiver Front-End for VCSEL-Based Optical Links With 49 UI Turn-On Time

A fast turn-on front-end (FE) for a burst-mode nonreturn to zero (NRZ) receiver targeting vertical cavity surface-emitting laser (VCSEL)-based optical links operating at 10 Gb/s/ch is presented. Its bandwidth and power are reconfigurable for energy-efficient burst-mode operation. The circuit design for 4.9 ns power-ON time using a power-gating approach is presented. Rapid power-ON is achieved using the regeneration of a high-speed latch, activated by a quarter-rate clock. Implemented in a 65-nm CMOS technology, the proposed FE consists of a shunt-feedback transimpedance amplifier (TIA), a configurable one-stage or four-stage postamplifier (PA) and an offset compensation loop. By reconfiguring the number of stages in the PA from four to one, power dissipation, and the FE bandwidth are reduced during periods of link inactivity while still maintaining sufficient gain to allow the detection of an incoming burst. The presented work is supported by simulation and measurement results with optical inputs at 10 Gb/s. The results demonstrate a 4.9-ns turn-on time, corresponding to 49 unit intervals (UIs). The overall FE dissipates 5.7 mW at 10 Gb/s (0.57 pJ/bit) and 1.9 mW during idle periods. The complete receiver of each channel occupies an area of 95 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}\,\,\times81\,\,\mu \text{m}$ </tex-math></inline-formula> . A 5% area overhead is introduced by the burst sensing circuit.

Low-Complexity Sampling Frequency Offset Estimation and Compensation Scheme for OFDM-Based UWOC System

In this paper, a simple sampling frequency offset (SFO) estimation and compensation scheme based on two phase-conjugated pilots is proposed and experimentally demonstrated in an OFDM-based underwater wireless optical communication (UWOC) system. The phase shift is obtained by simple multiplication for phase-conjugated pilots, and the results are averaged to perform more accurate phase estimation. The experimental results show that the estimation offset is limited within ±3 ppm when the SFO ranges from −1000 ppm to +1000 ppm over a 1 m tap water channel. Moreover, with the help of the proposed scheme, up to ±300 ppm SFO can be well-compensated with error vector magnitude (EVM) penalties below 1 dB after 1 m underwater transmission. In addition, the results demonstrate that, compared with the ideal case without SFO, our proposed SFO compensation scheme can provide nearly negligible bit error rate (BER) penalties in saltwater with the highly scattering property.

Improved Timing for better performance of distributed data acquisition systems - a further refinement

Continuing the works debuted in the previous work “Improved Timing for better performance of distributed data acquisition systems” the present paper refines and revisits the concept of a local oscillator with GPS corrections as a source of long-term stable reference clock signals with direct application in distributed data acquisition systems. The system as described herein can generate precise and repeatable clock source signals for trigger and sync of various data acquisition equipment when used in mixed and distributed architectures. These timing signals are a vital part of data acquisition as oftentimes raw data is processed as time series and correlations are made based on timestamps. This paper details improvements in implementation of a cost-effective high precision time base (reference clock) using a GPS receiver as a primary time source and a local high precision real time clock as a secondary oscillator. The improvements to the previous version come both from hardware refinements and from updated software with reduced latencies and reconfigured structure that allows for compensation of internal delays and internal process offsets.

Modelling and fabrication of wide temperature range Al0.24Ga0.76As/GaAs Hall magnetic sensors

Silicon Hall-effect sensors have been widely used in industry and research fields due to their straightforward fabrication process and CMOS compatibility. However, as their material property limitations, technicians usually implement complex CMOS circuits to improve the sensors’ performance including temperature drift and offset compensation for fitting tough situation, but it is no doubt that it increases the design complexity and the sensor area. Gallium arsenide (GaAs) is a superior material of Hall-effect device because of its large mobility and stable temperature characteristics. Concerning there is no specified modelling of GaAs Hall-effect device, this paper investigated its modelling by using finite element method (FEM) software Silvaco TCAD® to help and guide GaAs Hall-effect device fabrication. The modeled sensor has been fabricated and its experimental results are in agreement with the simulation results. Comparing to our previous silicon Hall-effect sensor, the GaAs Hall-effect sensor demonstrates potential and reliable benchmark for the future Hall magnetic sensor developments.

Color Balance Method of Dense Point Cloud in Landslides Area Based on UAV Images

Landslides are a natural geological phenomenon and often cause economic losses, property damage, and loss of lives. The detection and recognition based on the dense point cloud derived from Unmanned Aerial Vehicle (UAVs) images play an important role in understanding the mechanism of landslides. However, the brightness difference of UAV images with large altitude differences usually makes the dense point cloud within a landslide area show color stratification, and the processing results of popular commercial and open-source software are not ideal. In this study, a multi-view UAV image brightness compensation method based on regular 3D points is proposed, and is combined with the open-source software OpenMVG and OpenMVS to obtain a dense point cloud with balanced color on the landslide’s surface. The selected study area is located in the active landslide region caused by the Tengqing coal mining area in Guizhou Province, China. The terrain following flight method was used to acquire complete high resolution UAV images of the study area. Experimental results show that the global gain and offset compensation methods proposed in this study can effectively reduce the 22.3% brightness difference in the overlapping area of the adjacent images. The comparison results and the processing results of other commercial software show that the method can be applied to the color balance of the dense point cloud for UAV images with large-altitude differences.

6G Indoor Network Enabled by Photonics- and Electronics-Based sub-THz Technology

We propose an indoor network with a sub-terahertz- band wireless link for 6G applications. In our proposed indoor network, an optical hub unit (OHU) that controls the entire system is optically linked to THz remote nodes (RNs) over optical distribution fibers. The THz RNs communicate with the user equipment through a sub-THz wireless link. The function of the THz RNs is to provide an interface between the optical link and the sub-THz wireless link. For downlink transmission, a photonics-based sub-THz-band signal generation method is adopted to take advantage of the broadband characteristics of the optical components. An electronics-based sub-THz mixer is also used for uplink transmission because of its cost-effectiveness and low energy consumption. A digital signal processor (DSP) is designed to recover the original transmitted baseband signal. The DSP provides frequency offset compensation over a wide frequency range and reduces the probability of cyclic slip. The performance of the proposed system was investigated experimentally with commercially available optical&#x002F;electrical components. We demonstrate 100 Gb&#x002F;s 2.5-m wireless transmission with a 16-quadrature amplitude modulation (16-QAM) signal for configuring the downlink. The optical transmission distance was set to 10 km, and the power penalty measured by optical transmission was negligible. We also investigated the scalability and tunability of the photonics-based sub-THz transmitter to confirm the upgradability of our proposed indoor network to consider future capacity expansion. To establish an uplink, a 25 Gb&#x002F;s 1.5-m wireless transmission with a quadrature phase shift keying (QPSK) signal was employed. A directly modulated laser was used for cost-effective optical transmission. Unlike downstream transmission, a measured bit error rate (BER) penalty caused by the optical transmission was observed. This is due to the interplay between the frequency chirp of the directly modulated laser and the chromatic dispersion in the fiber. Despite this penalty, BERs less than the soft-decision forward error correction (FEC) threshold (2&#x00A0;&#x00D7;&#x00A0;10^&#x2212;2) with 20&#x0025; overhead were achieved. We discuss several remaining technical challenges in real-field deployment. These include THz Tx power improvement, photonic integration, reducing form-factor, polarization insensitivity, and automatic beam steering. Our recent efforts to address these issues are also introduced and examined.

Micro-grooving of brittle materials using textured diamond grinding wheels shaped by an integrated nanosecond laser system

Freeform surfaces including both the aspherical and prismatic concave/convex have been widely utilized in optical, electronical, and biomedical areas. Most recently, it is reported that grinding with structured wheels provides new possibility to generate patterns on hard and brittle materials. This paper reports the latest research progress on micro-grooving glass ceramic using laser structured diamond grinding wheels. A nanosecond pulse laser is firstly integrated into an ultra-precision machine tool and used for the in-line conditioning of super abrasive grinding wheels, i.e., truing, dressing, and profiling/texturing. Meanwhile, an offset compensation method, considering the shifting depth of focus (DoF) at different laser irradiation positions, is proposed to accurately generate various profiles on the periphery of the grinding wheels. Three types of patterns (riblets, grooves, and pillars) are successfully fabricated on the ceramic substrate using the laser textured grinding wheels. The results indicate that the integrated laser system offers high flexibility and accuracy in shaping super abrasive grinding wheels, and the grinding using textured grinding wheels provides a promising solution to generate functional microstructures on hard and brittle materials.

ВИСОКОЛІНІЙНІ ДВОТАКТНІ БУФЕРНІ ПРИСТРОЇ НАПРУГИ З ПАРАМЕТРИЧНОЮ КОМПЕНСАЦІЄЮ ЗСУВУ НУЛЯ

The method of structural and functional organization of high-performance two-stroke voltage buffer devices with parametric zero offset compensation is considered. The relevance and practical feasibility of using a zero offset compensation generator in the buffer voltage devices to obtain low linearity error are substantiated.

A Comparison Between Tone-Based and Code-Based Cell Search Schemes for Multipath Division Multiple Access

Cell search procedure is an essential and critical process in an early stage when the user equipment (UE) is powered on. It mainly comprises symbol and frame timing synchronization, frequency offset compensation, and base station (BS) identification. Among the current exiting 3G, 4G and 5G mobile networks, the UE completes the initial cell search based on different code sequences. In this paper, we investigate and compare two kinds of cell search methodology. Tone-based and code-based methods are explored for massive antenna systems. The detailed description and analysis are offered for two approaches. Simulation results indicate that the tone-based cell search not only possesses stable performance with respect to path numbers but also outperforms the code-based one in general channel realizations in terms of cell search error probability. The results suggest that the tone-based cell search could be used for 5G communication systems.

Frequency-domain seismic data transformation from point source to line source for 2D viscoelastic anisotropic media

We have developed a simple yet effective transform function to convert 3D point-source seismic data to equivalent 2D line-source data, which is required when applying efficient 2D migration and full-waveform inversion to field data collected along a line. By numerically comparing the 3D and corresponding 2D Green’s tensors in various media, the phase shift approximately 45° and the offset amplitude compensation factor, as well as small fluctuations of the amplitude ratios, are observed in all nonzero components of the wave-equation solutions. Based on these observations, we derive a transform function consisting of (1) a simple filter for compensating amplitude and phase shift and (2) stretching scalars for scaling amplitude differences for different components. We use the 3D and 2D analytical wave solutions in various homogeneous media to demonstrate the accuracy of our transform function, and then apply it to a heterogeneous viscoelastic anisotropic model and a modified Marmousi model. All of these results indicate that our transform function is applicable for the conversion of point-source data to equivalent line-source data for imaging 2D subsurface structure.

Design of a Novel Wearable System for Foot Clearance Estimation.

Trip-related falls are one of the major causes of injury among seniors in Canada and can be attributable to an inadequate Minimum Toe Clearance (MTC). Currently, motion capture systems are the gold standard for measuring MTC; however, they are expensive and have a restricted operating area. In this paper, a novel wearable system is proposed that can estimate different foot clearance parameters accurately using only two Time-of-Flight (ToF) sensors located at the toe and heel of the shoe. A small-scale preliminary study was conducted to investigate the feasibility of foot clearance estimation using the proposed wearable system. We recruited ten young, healthy females to walk at three self-selected speeds (normal, slow, and fast) while wearing the system. Our data analysis showed an average correlation coefficient of 0.94, 0.94, 0.92 for the normal, slow, and fast speed, respectively, when comparing the ToF signals with motion capture. The ANOVA analysis confirmed these results further by revealing no statistically significant differences between the ToF signals and motion capture data for most of the gait parameters after applying the newly proposed foot angle and offset compensation. In addition, the proposed system can measure the MTC with an average Mean Error (ME) of −0.08 ± 3.69 mm, −0.12 ± 4.25 mm, and −0.10 ± 6.57 mm for normal, slow, and fast walking speeds, respectively. The proposed affordable wearable system has the potential to perform real-time MTC estimation and contribute to future work focused on minimizing tripping risks.

Research on position offset compensation of underwater manipulator

A compensation method for end position offset of underwater manipulator is presented in this paper. Firstly, the end deformation of the underwater manipulator is obtained by ANSYS analysis, and then the end position offset equation is obtained by MATLAB curve fitting. Finally, the equation is added to the kinematic model of the underwater manipulator, which improves the accuracy of the kinematic model of the underwater manipulator and lays a foundation for the accurate position control of the underwater manipulator.