Interference Compensation Research Articles

Micro Aspheric Convex Lenses Fabricated by Precise Scraping.

An easy, fast, inexpensive, and simple method utilizing a microshaper with a very small knife nose is used to fabricate microconvex aspherical lenses. The microshaper is mounted on a computer numerical control (CNC) machine. To achieve an accurately designed profile of the lens surface, a cutter-path planning algorithm with compensation for knife interference is developed. Exerting this algorithm in CNC machining, the microconvex aspheric surface is precisely scraped. To verify the precise machining of the cutter path planning algorithm, three aspheric surfaces of conic sections (ellipsoid, paraboloid, and hyperboloid) are successfully fabricated. The profiles scraped by the microshaper agree well and precisely with the designed theoretical conic section curve. Using a simple polishing method to make the machined surface smoother, the roughness is reduced from 143 and 346 nm to 52 and 44 nm for the path line direction and its transverse direction, respectively. The micro-aspherical lenses have moderate machining properties using a simple polishing method. The results show that the designed profiles of micro-aspheric convex lenses can be machined precisely and efficiently by the microshaper with the cutter-path planning algorithm developed in this work. From the image comparison formed by the aspherical and spherical microlenses, the aspherical lenses provide a better image. It is feasible that the designed profile of the micro-aspherical lenses with specific functions could be machined using the cutter-path planning algorithm developed in this work.

Trajectory tracking control based on memory data for robots with imprecise dynamic properties and interference

AbstractIn this article, a new controller design method is proposed for the trajectory tracking problem of robots with imprecise dynamic properties and interference. By using the tracking error memory data of state variables to construct control law, the tracking errors caused by the system interference and inaccurate system modeling can be eliminated, and interference compensation can be realized, so that the system has the desired dynamic performance. The proposed method comes from the tracking control design of an affine nonlinear system. The controller is based on the error function of the control input in the ideal state and the actual state. According to the Lyapunov stability principle, it is proved that the proposed controller has good robustness under the conditions of bounded interference and inaccurate modeling. MATLAB was used to establish the controller and dynamic equation of the two‐joint planar robot for trajectory tracking simulation. Simulation results are presented to illustrate the performance of the proposed controller.

The response suppression method of electromagnetic vibration exciters based on the compensation current

Aiming at the problem that the vibration calibration accuracy is seriously affected by the additional dynamic magnetic field interference and eddy current effect of the electromagnetic vibration exciters, a suppression method based on magnetic field tracking compensation is proposed. The influence of the dynamic magnetic field interference of the driving current on the total harmonic distortion of the driving coil output electromagnetic force waveform and the characteristics of the eddy current effect are studied. The compensation current set on the central yoke, its direction opposite to the driving current, to realize the dynamic tracking compensation and suppression of the additional dynamic magnetic field interference and eddy current loss of the driving coil, and effectively improve the vibration waveform accuracy and eliminate the temperature change of the working platform caused by eddy current effect. The simulation results show that the eddy current loss may be reduced by 53 % and the total harmonic distortion of the driving electromagnetic force waveform may be reduced by 0.12 % though the method in this paper.

Research on attitude measurement compensation technology under the influence of solar infrared radiation interference

Aiming at the problem that the dual-band infrared radiation attitude measurement cannot be used all day long, the dual-band solar infrared radiation interference analysis and compensation technology are studied. The proportion of solar direct and scattered infrared radiation in the total atmospheric radiation is counted by MODTRAN, and the influence of solar infrared radiation interference on dual-band attitude measurement is simulated. It shows that the medium wave infrared sensor cannot work normally under the influence of solar infrared radiation. When the long wave infrared sensor is facing the solar infrared radiation, it will produce an attitude angle error within 18 degrees, but when it is not facing the solar infrared radiation, the impact is small, and the attitude angle error is within 1 degree. Based on the solar infrared radiation interference law on long wave infrared radiation sensor, a four-axis attitude compensation algorithm with long wave infrared radiation sensor is designed. The semi-physical experimental results show that the attitude solution accuracy of the four-axis attitude compensation algorithm is within ±1 degree, which effectively improves the infrared radiation attitude test accuracy under the interference of solar infrared radiation. The algorithm is proved to be a solution with strong anti-interference ability for the dual-band infrared radiation attitude measurement of rotating projectile under all-day situation.

Interference compensation discrete control based on memory data for a class of nonlinear systems

AbstractIn this article, in order to solve the interference compensation control problem of a class of nonlinear systems, we propose a method based on memory data to suppress interference greatly. Firstly, the continuous time model of nonlinear system is discretized to obtain the discrete model of the system, then, which is simplified by zero‐order hold. On this basis, the interference at the previous moment is calculated by using the system states measured and stored at the previous moment, which is added to the systems input to compensate for the interference at the current moment. Finally, the simulation results show that our method has a good inhibitory effect on interference, and the attenuation rate of interference is more than 98.

Effectiveness Analysis of the Method of Measuring the Parameters of Network Elements and Signals in the Conditions of Concentrated Interference Spectrum

The measurement method of network elements and communication signals parameters in the conditions of the extraneous signals is developed. The possibility of using adaptive noise compensators in mobile network parameters is considered. In adaptive noise compensators, a reference signal is generated in a reference reception channel without the desired signal. Deleting the desired signal from the reference receiving channel is a problem, especially in a mobile network. In an actual situation, in the mobile network, installing the antenna of the reference channel of the reception in the right way is hardly possible. In addition, the direction of arrival of the reference signal can constantly be changing, which requires adjusting the zero pattern of the antenna of the reference reception channel in the direction of its arrival in real-time. To solve the problem of adaptive interference compensation, it is necessary to find such technical solutions that all these actions for the organization of the reference channel of reception are as simple as possible, formalized, and automated. The work proposes using an elemental adaptive antenna array in the reference receiving channel N. Using mathematical modeling in the MATLAB environment, the efficiency of removing the reference signal from the reference reception channel was analyzed. As a criterion for the effectiveness of the adaptive antenna array in the reference receiving channel, the traditional indicator of spatial-temporal processing, namely the SNR ratio of the reference signal levels to the sum of the levels of interference and noise, is taken. The dependences of the SNR in the reference receiving channel on the interference power level were obtained. The analysis showed that with the help of a 3-element AAA, it is possible to reduce the reference signal level in the reference channel of the adaptive interference compensator by 28 dB. The dependence of the SNR in the reference receiving channel on the number of antenna elements was obtained. The analysis showed that the SNR in the reference receiving channel decreases linearly with an increase in the number of antenna elements. That is, it can be concluded that the more antenna elements the reference receiving channel contains, the more effectively the reference signal is removed in the reference receiving channel of the adaptive interference compensator.

Optimal nonlinear filtering of M-PSK signals against a background of harmonic interference with a random initial phase

Objectives. The widespread use of radio data transmission systems using signals with multiposition phase shift keying (MPSK) is due to their high noise immunity and the simplicity of constructing the transmitting and receiving parts of the equipment. The conducted studies have shown that the presence of non-fluctuation interference, in particular, harmonic interference, in the radio channel significantly reduces the noise immunity of receiving discrete information. The energy loss in this case, depending on the interference intensity, can range from fractions of dB to 10 db or more. Therefore, interference suppression is an important task for such radio systems. The aim of the work is to synthesize and analyze an algorithm for optimal nonlinear filtering of MPSK signals against a background of harmonic interference with a random initial phase.Methods. The provisions of the theory of optimal nonlinear signal filtering and methods of statistical radio engineering are used.Results. The synthesis and analysis of the algorithm of optimal nonlinear filtering of MPSK signals against the background of harmonic interference with a random initial phase are carried out. The synthesized receiver contains a discrete symbol evaluation unit, two phase-locked frequency circuits of reference generators that form evaluation copies of the signal and interference, and cross-links between them. Analytical expressions are obtained that allow calculating the dependences of the bit error probability on the signal-to-noise ratio and the interference intensity µ. It is established that uncompensated fluctuations of the initial phase of the useful signal have a greater effect on the receiver noise immunity than similar fluctuations of the phase of harmonic interference, especially with low positional signals.Conclusions. Comparison of the obtained results with the results obtained in the case when there are no harmonic interference compensation circuits shows that the use of the obtained phase filtering algorithms allows for almost complete suppression of harmonic interference. Thus, if µ = 0.5 and the probability of error is 10−2, the energy gain at M = 2 is about 2.5 dB, at M = 4 – about 6 dB, at M = 8 and M = 16 – at least 10 dB.

Оптимізація поляризаційно-доплерівської селекції малорозмірних об’єктів на тлі підстильної поверхні

Using the method of maximum likelihood, the optimal algorithm of polarization-Doppler selection of objects on the background of the underlying surface, hydrometeors, urban buildings from aerospace carriers of radio electronic equipment has been synthesized. To solve the problem polarimetric properties of the scattered electromagnetic radiation of natural environments and anthropogenic objects were analyzed.The functional-deterministic mathematical model of the useful signalis determined. When solving the optimization problem, the method of maximum likelihood functionality and likelihood functionality for correlated processes were used, which contains the inverse matrix of inverse correlation functions of the observation equation. The obtained signal processing algorithm includes operations of spectral resection of passive interference. Polarization compensation of passive interference is performed by a combination of interchannel subtraction of the reflected signals of different polarizations. The quasi-optimal features of the synthesized algorithm, which has an obvious physical value and is optimal in the absence of internal noise, are considered. Based on the obtained results, a block diagram of the polarization-Doppler noise compensator and selection of useful signals against the background of noise reflections from the earth's surface has been developed. The study of the physical characteristics of the elements of the polarization covariance matrix of interferences at a high level of correlation of reflections of passive interferences of different polarizations is conducted.Based on the obtained results, it is proposed to introduce indicators of efficiency of passive interference compensation and selection of useful signals. The results of the analysis of the obtained indicators depending on the coefficient of the ratio of variances of passive interference indicate the need to use the polarization differences between signals and interference for selecting objects against the background of the underlying surface. The results obtained can be used to create ground-based and aerospace-based radar systems for detecting moving objects and objects with pronounced polarization features.

Дослідження якісних показників поляризаційної селекції об’єктів на фоні пасивних завад в поляризаційно-доплерівській радіолокаційній системі

The optimal algorithm of polarization-Doppler selection of targets against the background of passive interference is considered. The polarimetric properties of scattered electromagnetic radiation of objects. The functionally-determined mathematical model of the useful signal, structure and correlation characteristics of the internal radiation of the receiver is determined. The algorithm of optimal processing, synthesized within the method of maximum likelihood, is considered for two limit cases. Algorithmic actions in the processing of passive interference and methods of their compensation are considered and investigated. Based on the obtained results, the expression for the algorithm of compensation of interferences reflected from the earth's surface is written. The obtained algorithm equalizes the variance of the input signals and compensates the residual variance with the help of weight coefficients. On the basis of the developed algorithm the scheme of the structurally simplified optimum compensator of passive disturbances is formed. Feature processing of useful signals in the compensation scheme is investigated. To ensure the adaptability of the generated algorithm, the coefficient of the variance ratio is based on the results coming from the variance meter. It is proposed to introduce quality indicators of polarization object selection on the background of the underlying surface, which combines indicators of efficiency of passive interference compensation and indicators of efficiency of useful signal-processing against the background of internal noise of receivers. The corresponding dependence of the indicators on the correlation coefficients of passive interference of different polarizations, as well as on the coefficients that separately characterize the level of difference in signal intensities and interference in the reception channels. The information value of each indicator of the efficiency of polarization signal selection from the ratio of the input variances, the correlation coefficient of passive interference and the ratio of the input signals is investigated.The obtained results are proposed to be used to improve the quality of polarization selection of objects in ground-based and aerospace-based radar systems.

Increasing the accuracy of the directional survey when drilling oil and gas wells

Introduction. The method оf directional survey is currently widely used when drilling horizontal and directional wells for oil and gas. The method includes a relatively cumbersome and complex system of 40 “Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal”. No. 6. 2021 ISSN 0536-1028 sequential operations of converting the components of the Earth’s magnetic field into proportional electrical signals using magnetometers, amplifying and scaling sensor signals, integrating analog-todigital conversion of electrical signals, determination of the three components of magnetic fields from the measured output signals of geosteering sensors, and additional introduction of various kinds of corrections to determine the survey parameters of the bottom. Methods of research. The main objective of the research is to improve the accuracy of the directional survey while drilling directional wells for oil and gas. The process of drilling provides accurate online compensation for interference from large ferromagnetic complexes in the bottomhole assembly acting on the sensors of the inclinometer magnetic field components. The developed method for increasing the accuracy of the directional survey when drilling directional wells online eliminates the need for various additional corrections in the course of the drilled well bottom geometric position measurement. Results and analysis. Analytical studies of the structure of the noise created by various magnetic blocks included in the drillsting assembly during installation have been carried out. A specialized device has been developed to control the directional survey process when drilling directional wells. A relatively simple set of processes reduced to magnetic blocks location data and geometric parameters introduction has been developed together with a working system including a microprocessor and compensation solenoids. It made it possible to obtain actual data on the spatial location of the drill string bottom in real time

Interference Mitigation for Two-Path Successive Relaying Systems

A key issue in the two-path successive relaying (TPSR) communications systems is the interference, which is caused by the concurrent transmission of the source and one of two relays. The previously reported investigations show that interference cancellation is required at the relays and destination to avoid severe performance degradation. In this work, we introduce a different approach that does not require interference compensation for decode-and-forward TPSR systems, while maintaining diversity gain and full rate. At the listening relay, the proposed approach enables the separation between the source and the forwarding relay transmissions by using two carriers of the same frequency but in phase quadrature. Therefore, a maximum-likelihood data detector can be adopted without being interfered by the inter-relay link. At the destination node, we make use of the interference signal to develop optimal and sub-optimal data detectors. Furthermore, we derive a theoretical lower bound on the bit-error-rate performance. Simulation and analytical results demonstrate the superiority of the proposed approach compared to the conventional schemes reported in the literature.

Performance of Two Different Flight Configurations for Drone-Borne Magnetic Data.

The compensation of magnetic and electromagnetic interference generated by drones is one of the main problems related to drone-borne magnetometry. The simplest solution is to suspend the magnetometer at a certain distance from the drone. However, this choice may compromise the flight stability or introduce periodic data variations generated by the oscillations of the magnetometer. We studied this problem by conducting two drone-borne magnetic surveys using a prototype system based on a cesium-vapor magnetometer with a 1000 Hz sampling frequency. First, the magnetometer was fixed to the drone landing-sled (at 0.5 m from the rotors), and then it was suspended 3 m below the drone. These two configurations illustrate endmembers of the possible solutions, favoring the stability of the system during flight or the minimization of the mobile platform noise. Drone-generated noise was filtered according to a CWT analysis, and both the spectral characteristics and the modelled source parameters resulted analogously to that of a ground magnetic dataset in the same area, which were here taken as a control dataset. This study demonstrates that careful processing can return high quality drone-borne data using both flight configurations. The optimal flight solution can be chosen depending on the survey target and flight conditions.

Research on aeromagnetic three-component error compensation technology for multi-rotor UAV

Aeromagnetic three-component data contain a large amount of geomagnetic information, which can help to obtain a quantitative interpretation of a magnetic anomaly and to improve the identification accuracy of an abnormal body. However, aeromagnetic three-component data of an unmanned aerial vehicle (UAV) include the carrier fixed interference error, inductive interference error, eddy current interference error, and attitude error. Therefore, carrier interference compensation and attitude compensation are necessary to obtain three-component data in a geographical coordinate system. This paper analyzes the difference of six types of attitude conversion matrices for the mutual conversion between the geographic and carrier coordinate systems. Based on the analysis results, the yaw-pitch-roll sequence has the smallest error when calculating the attitude conversion, so the compensation sequence of the roll-pitch-yaw is selected for attitude compensation. The characteristics of the UAV carrier interference error are also analyzed. A low-pass filter is set up for data preprocessing according to the high-frequency characteristics of the carrier eddy current interference, and carrier fixed interference and induction interference compensation models are constructed based on the Tolles-Lawson model. The aeromagnetic three-component comprehensive compensation error objective function is established by integrating attitude compensation and carrier interference compensation. In addition, an adaptive step-size cuckoo algorithm is proposed to obtain the minimum value of the objective function to solve 12 compensation parameters so that the accurate three-component data can be obtained quickly, efficiently, and accurately. Finally, a comprehensive compensation experiment is performed on the three-component aeromagnetic data, and the mean error of the three-component data after compensation is reduced to less than 0.72 nT.

Compensation for mobile carrier magnetic interference in a SQUID-based full-tensor magnetic gradiometer using the flower pollination algorithm

The improving quality of ultra-sensitive superconducting quantum interference devices has led to the construction of advanced full-tensor magnetic gradiometers (FTMGs) integrated on mobile carriers such as aircraft, vehicles and ships. FTMGs measure the smallest spatial magnetic gradients, possessing many practical advantages compared to conventional scalar surveys and three-component surveys. However, the magnetic interference field caused by the magnetic sources associated with the carrier significantly decreases the precision of measurement. In this paper, a novel method is proposed to compensate for the magnetic interference field. Specifically, a mathematical model containing compensation coefficients of the mobile FTMG system is constructed by extending the Tolles–Lawson model. By formulating the task into nonlinear problems, unknown compensation coefficients in the model can be solved by the flower pollination algorithm, which has the advantages of insensitivity to iterative initial values, less parameter tuning and strong global search abilities. Both the finite-element simulation results based on COMSOL Multiphysics and the results of a field experiment show that the proposed method provides a useful way for the optimal estimation of compensation coefficients and the reduction of the magnetic interference field.

Reduction of electromagnetic interferences in measurements of fast-changing air velocity fluctuations by means of hot-wire anemometer

Air flow velocity measurements are the key issues in examining the condition and progress of mine ventilation process. In addition to standard measurements carried out in the stock exploitation process, it is necessary to conduct cognitive scientific research in this area. One of the important issues here is the measurement of fast-changing fluctuations of air velocity, enabling the knowledge of the spectral structure of the tested flow. Hot-wire anemometers are used for such measurements both in laboratories and in industrial conditions. A frequent metrological problem is the presence in the measuring area of a high level electromagnetic interference (EMI) from electrical networks and devices. Due to the metrological properties of hot-wire anemometers, such as high gain and wide frequency bandwidth, measuring signal in the presence of electromagnetic interferences may be subject to strong disturbances. Therefore, it is necessary to develop methods for reducing or eliminating these disturbances. The article presents such a new method based on the use of an additional induction loop in the anemometric sensor for compensation or reduction of interferences.

Robust Quadrotor Control through Reinforcement Learning with Disturbance Compensation

In this paper, a novel control strategy is presented for reinforcement learning with disturbance compensation to solve the problem of quadrotor positioning under external disturbance. The proposed control scheme applies a trained neural-network-based reinforcement learning agent to control the quadrotor, and its output is directly mapped to four actuators in an end-to-end manner. The proposed control scheme constructs a disturbance observer to estimate the external forces exerted on the three axes of the quadrotor, such as wind gusts in an outdoor environment. By introducing an interference compensator into the neural network control agent, the tracking accuracy and robustness were significantly increased in indoor and outdoor experiments. The experimental results indicate that the proposed control strategy is highly robust to external disturbances. In the experiments, compensation improved control accuracy and reduced positioning error by 75%. To the best of our knowledge, this study is the first to achieve quadrotor positioning control through low-level reinforcement learning by using a global positioning system in an outdoor environment.

Adaptive interference compensation method

The article is devoted to the consideration of the method of adaptive compensation of interference to information transmission systems using space-time coding technology. When such systems use two or more antennas for transmitting information and the same number of antennas for receiving, it becomes possible to compensate for interference signals. The investigated compensation method is based on the introduction of adaptive filters into each of the input channels of the information transmission system. Adaptive filters are tuned to the process of the mixture of the useful signal and interference so that after the processing the sum of the interference components at the output of the compensator is minimized, and the useful signal does not deteriorate on average. The expressions that determine the algorithm of the adaptive noise compensator are given. The compensator for interference signals coming from a powerful airfield radar was built for the ground radio relay communication system with double antenna spacing. It has been shown experimentally that the compensator suppresses radio impulse interference from 30 to 40 decibels in different frequency channels of the microwave link.

Periodic disturbance suppression method in position domain for rotating telescope

In order to suppress influence of the periodic interference signal’s fluctuation on the rotating telescope scanning system speed stability and imaging effect, the interference compensation control was carried out by establishing the interference torque model and error compensator. Firstly, it was obtained that the periods of the disturbances were time-varying but position-fixed through experiment. Secondly, by measuring the current of quadrature axis \begin{document}${I_q}$\end{document} , a set of disturbance torque model acquisition system based on Fourier theory was established, and the specific expression of the disturbance torque model was extracted through eight steps. Then, the periodic error was compensated according to the expressions through four steps. Finally, the effectiveness of control compensation was verified by the actual system. The experimental results show that angle error of the telescope can be reduced to less than ±5.5″ of the angle error every 10 ms when the telescope is running at the speed of 68 （°）/s, and the reduction amplitude is more than 30%, which can meet the requirement of ±7″, and the speed stability is greatly improved.

Features of signal transmission through a fiber-optic system for an interference compensation module for an active phased array antenna

The article describes the operation of the X-band radar under the influence of active and passive interference. The rationale for using the interference compensation module in a radar station with a small-sized active phased array antenna is presented. A fiber-optic system has been developed for transmitting a signal from a compensation module. The results of experimental studies of the transmission system are presented. The advantages of using a fiber-optic system in a radar station in comparison with a coaxial cable are shown.

Low complexity joint equalization and interference compensation in fractional Fourier domain for DCT-OFDM system with CFO

Orthogonal frequency division multiplexing (OFDM) systems based on discrete fractional Fourier transform (DFRFT) chirp basis replacing the complex exponential basis of discrete Fourier transform (DFT) is extensively studied in the literature. Authors of this paper have recently proposed fractional Fourier domain equalization (FFDE) for an OFDM system with a discrete cosine transform (DCT) multicarrier basis. The proposed DCT-OFDM system with FFDE nearly achieves the performance of the DFRFT-OFDM system without requiring any chirp rate feedback to the transmitter. This is enabled by separately performing the tasks of multicarrier modulation/demodulation with IDCT/DCT kernels at transmitter/receiver and FFDE using DFRFT/IDFRFT kernels both at the receiver. However, in the presence of a high value of CFO and also with higher modulation order, the residual interference power existing after channel equalization in fractional Fourier domain (FFD) using the channel decomposed with DFRFT significantly degrades the error rate performance. In this paper, the equalization and interference compensation is treated as a joint and linear problem in FFD after DFRFT at the receiver. Full compensation by performing direct matrix inverse can ensure the performance free from CFO for the DCT-OFDM system with both FDE and FFDE, but will drastically increase the computational cost to the O(N3) for implementing the joint equalizer at the receiver for N subcarriers. Therefore, low complexity joint equalization and interference compensation (JEIC) schemes are proposed for the DCT-OFDM system with FFD decomposition utilizing the banded implementation of joint ICI matrix after DFRFT at the receiver. The banded JEIC can closely preserve the interference-free performance and only requires operations in the O(N) to implement the joint equalizer.