Nonlinear Error Research Articles

Self-Commissioning of Synchronous Reluctance Motor at Standstill With Inverter Nonlinearity and Resistance Error Compensation

Self-Commissioning of Synchronous Reluctance Motor at Standstill With Inverter Nonlinearity and Resistance Error Compensation

A Calibration Scheme for a 800-Ms/s 14 Bit Pipelined ADC in 28-nm CMOS

Abstract A calibration scheme is proposed to compensate linear and nonlinear errors including offset, cap mismatch, second- and higher-order harmonics and memory induced errors in pipelined analog-to-digital converters (ADCs). The alternating minimization (AM) algorithm is proposed to accurately estimate the coefficients of the errors. As an accurate input value is hardly acquired in practical measurements, instead, the proposed scheme estimates the input and the error coefficients jointly. Once the error coefficient was calculated, it will be recorded in a lookup table (LUT). The scheme has been demonstrated in a 800-Ms/s 14-bit pipelined ADC fabricated in a 28nm CMOS process, which features a signal-to-noise ratio (SNR) and spurious-free dynamic range (SFDR) improvement of 2.49 dB and 11.49 dB at 800-Ms/s.

Development of an in-situ real-time laser targeting algorithm for a 3D LiDAR-integrated galvanometric laser scanner system

A Galvanometric laser scanner utilizes mirrors attached to dual galvanometers to direct laser beams. GLS systems are widely employed across various industrial sectors due to their compact size, high resolution, and high positional repeatability. Extensive research has been conducted to calibrate these systems to steer lasers to desired positions accurately. However, much of this research has traditionally focused on fixed working distances, which does not align well with the portable capabilities that GLS systems offer in non-destructive evaluation fields. This study explores an algorithm that enables real-time laser targeting using a 3D LiDAR camera integrated into a GLS system. The research involved developing and calculating a projection matrix that projects 3D camera coordinates into 2D bit coordinates input to each galvanometer, based on linear assumptions. To address the non-linear errors that emerge from the linear assumption process, compensation was applied through 3rd-order regression and Artificial neural networks. As a result, the algorithm facilitated highly accurate laser targeting within a range of 0.5 m to 2.5 m based on coordinates acquired by the LiDAR camera.

Nonlinearity-suppressed micro-probe fiber optic interferometer for accurate long-range displacement measurements

Fiber-optic interferometry technology has advanced rapidly in recent years. However, accurate measurement of the displacement over long ranges remains a challenge. This study reveals that fiber interferometers with Fabry–Perot cavities experience non-elliptic multi-order nonlinear errors due to parasitic interference, leading to nonlinearity correction failures in the case of reflectivity mismatch. We proposes a nonlinearity-suppressed microprobe fiber interferometer to measure long-range displacement with high accuracy. The proposed microprobe interferometer structurally avoids non-elliptic nonlinearities from higher-order harmonics and ensures the effectiveness of the nonlinearity correction method. Moreover, we optimized the micro-sensing probe parameters based on an established multimedia transmission interference model to further improve the measurement accuracy of long-range displacement. Nonlinear errors are reduced from 2.3 nm to 0.92 nm in the application range 0–700 mm. The findings of this study demonstrate that the proposed nonlinearity-suppressed microprobe fiber interferometer is suitable for sub-nanometer accuracy measurements over displacements of several hundred millimeters, especially in limited-space scenarios. It has great potential for industries seeking breakthroughs in long-range displacement measurement, such as robotics, medical devices and manufacturing.

Development of Highly Sensitive and Thermostable Microelectromechanical System Pressure Sensor Based on Array-Type Aluminum-Silicon Hybrid Structures.

In order to meet the better performance requirements of pressure detection, a microelectromechanical system (MEMS) piezoresistive pressure sensor utilizing an array-type aluminum-silicon hybrid structure with high sensitivity and low temperature drift is designed, fabricated, and characterized. Each element of the 3 × 3 sensor array has one stress-sensitive aluminum-silicon hybrid structure on the strain membrane for measuring pressure and another temperature-dependent structure outside the strain membrane for measuring temperature and temperature drift compensation. Finite-element numerical simulation has been adopted to verify that the array-type pressure sensor has an enhanced piezoresistive effect and high sensitivity, and then this sensor is fabricated based on the standard MEMS process. In order to further reduce the temperature drift, a thermodynamic control system whose heating feedback temperature is measured by the temperature-dependent structure is adopted to keep the working temperature of the sensor constant by using the PID algorithm. The experiment test results show that the average sensitivity of the proposed sensor after temperature compensation reaches 0.25 mV/ (V kPa) in the range of 0-370 kPa, the average nonlinear error is about 1.7%, and the thermal sensitivity drift coefficient (TCS) is reduced to 0.0152%FS/°C when the ambient temperature ranges from -20 °C to 50 °C. The research results may provide a useful reference for the development of a high-performance MEMS array-type pressure sensor.

Capacitive pressure sensors based on microstructured polymer-derived SiCN ceramics for high-temperature applications

Traditional silicon-based pressure sensors cannot meet demand of pressure information acquisition in high-temperature extreme environments due to their low sensitivity, limited detection temperature and complex processing. Herein, a capacitive pressure sensor is fabricated using polymer-derived SiCN ceramics with convex microstructures via a sample replication strategy. Its performance is measured at different pressures (0–800 kPa) from room temperature to 500 °C. The results show that the SiCN ceramic capacitive pressure sensor exhibits low hysteresis, good non-linearity of 0.26 %, outstanding repeatability and high sensitivity of 0.197 pF/MPa under room temperature. When the test temperature reaches 500 °C, the performance of the prepared capacitive pressure sensor has no degradation, keeping competent sensitivity of 0.214 pF/MPa and nonlinear error of 0.24 %. Therefore, benefitting from the preeminent high-temperature properties, e.g., excellent oxidation/corrosion resistance and thermal stability, SiCN ceramics capacitive pressure sensors have great potential in the application of high-temperature and harsh environments.

A semi-active adaptive pneumatic vibration isolator based on frequency response analysis and nonlinear control

In this work, an adaptive nonlinear error feedback controller based on fuzzy state observer is proposed to a novel rubber pneumatic vibration isolator (PVI) system. First, a novel rubber PVI system is designed and developed. Harmonic balance method is applied to establish the dynamic model of the PVI system, so as to analyze the frequency response characteristics of the system. Second, to improve the PVI performance in low-frequency vibration, a nonlinear state error feedback control system based on fuzzy state observer is designed for the active PVI system. Furthermore, the experiment system is established. Finally, through the experimental comparison under 5 Hz, 7 Hz, 20 Hz, and 40 Hz, an adaptive PVI strategy is proposed. The experimental results demonstrate that the adaptive PVI shows better performance in vibration isolation.

Hybrid ALM-DSP TDC in Intel Arria 10 FPGA

The article presents the first implementation of a time-to-digital converter (TDC) using a digital signal processing (DSP) block from an Intel field-programmable gate array (FPGA) device. The design and configuration capabilities of the DSP blocks of the leading FPGA manufacturers, AMD and Intel, are compared in the context of time/digital conversion. Next, three variants of TDCs are presented. The problem of ultra-wide bins observed in both the classic version of the converter based on the Adaptive Logic Modules (ALM) and the version built using only DSP blocks has been mitigated in a hybrid variant, combining both solutions. The proposed variant of the hybrid ALM-DSP TDC implemented in Arria 10 FPGA from Intel (20 nm process node) achieved a resolution of 2.1 ps, a single-shot-precision better than 6.36 ps and reduced the maximum differential nonlinearity (DNL) error from 74.5 ps to 12.7 ps.

Dead-Time Free Modulation Scheme for IM Drive System Fed by Voltage Source Inverter

During the modulation process of the VSI motor drive system, the nonlinear errors caused by the dead-time and conduction voltage drop will increase the phase current harmonic distortion and the torque ripple. To solve this problem, a novel dead-time free modulation scheme is proposed in this paper. In the non-zero crossing region of the phase current, the switching tube, whose body diode can provide a continuation path, is set as off-state, the driving signal is only implemented on another switching tube with the same bridge arm, and the errors caused by the conduction voltage drop and switching delay are compensated to the pulse duration. At the same time, to suppress the zero current clamp effect that exists near the zero crossing point of the phase current, another modulation scheme for the phase current crossing zero in advance is proposed, which avoids the complicated determination and calculation of the current polarity near the zero crossing point of the current. Both of the above modulation schemes eliminate the dead-time, and the switching principle is presented. In addition, to suppress the impact of the current ripple and high-frequency noise on the accuracy of the phase current detection, a second-order resonance digital filter without phase shift is introduced. Finally, compared to two deadtime compensation methods, the effectiveness and superiority of the proposed dead-time free modulation scheme are verified by the experimental results.

A 14-Bit Digital to Analog Converter for a Topmetal-CEE Pixel Readout Chip

The Lanzhou Heavy Ion Research Facility (LIRF) is the largest heavy ion research facility in China, providing a substantial volume of experimental data for fundamental research in nuclear physics. The Topmetal-CEE is a pixel readout chip specifically designed for tracking detectors. Within the Topmetal-CEE framework, the front-end amplifier and comparator necessitate precisely adjustable bias voltages. Hence, in this paper, a 14-bit resolution DAC with an R-2R resistor network structure is designed, along with an amplifier featuring high driving capabilities as the DAC driver, thus preventing potential impedance issues when driving large pixel arrays. Test results demonstrate that the DAC module, operating under a 3.3 V supply voltage, can consistently output voltages ranging from 0 to 1.8 V. Furthermore, the differential non-linearity error is less than 1.07 LSB, and the integral non-linearity error is less than 1.57 LSB.

Improved self-correction of nonlinearity error in 3-step phase-shifting profilometry.

The generic self-correction method for nonlinearity-induced phase error (GSCN) can effectively suppress nonlinear error. However, GSCN directly ignores the periodic error of the 2N multiplication frequency in the error analysis stage, which still leads to errors in the suppressed results. In this paper, we propose a new method named improved generic self-correction method for nonlinearity-induced phase error in three-step phase-shifting profilometry. We retain the periodic error of the 2N multiplication frequency in the error analysis stage. In addition, based on the error model, we directly use the original fringes to compute the wrapped phases with -π/6, π/6, and π/3 phase shifts, respectively. Then, we use the original wrapped phase as the target phase and shifted the other three groups of wrapped phases to the target phase. Finally, we unwrap and fuse the four sets of wrapped phases to obtain the final corrected phase. Based on experimental results, the proposed method yields excellent reconstruction results and effectively suppresses nonlinear errors, making it highly efficient and precise.

Agricultural low-cost waste adsorption of methylene blue and modelling linear isotherm method versus nonlinear prediction

AbstractThis study shows that geographically marked wheat hull, named Siyez, rice hull Sarı Kılçık, and Taşköprü Garlic stalk were used as agricultural waste to potential adsorbent materials for removing methylene blue from aqueous solution. Experimental data were evaluated in both equilibrium batch process and kinetic studies. In addition, the factors that affect the adsorption capacities, such as pH solutions, methylene blue concentration, contact time, and temperatures, were also investigated. Obtained data were subject to two constant adsorption models of Langmuir, Freundlich, Temkin, and Dubinin−Radushkevich. The kinetic models (pseudo-first-order, pseudo-second-order, intra-particle diffusion and film diffusion) and thermodynamic parameters were evaluated. The adsorption isotherms, characterized by an excellent fit with the Langmuir model (R2 = 0.99) across all adsorbents, underscore the prevalence of monolayer adsorption of methylene blue, in contrast to the Freundlich equation. Adsorption kinetics of the methylene blue onto the adsorbents followed pseudo-second-order kinetic model. According to high regression coefficient (R2) and minimal values of nonlinear error functions like RMSE; the maximum monolayer adsorption capacities of wheat hull, rice hull and garlic stalk were found to be 62.50 (mg/g), 54.94 (mg/g), and 370.37 (mg/g), respectively. The results indicated that these proposed adsorbents could be low-cost and effective adsorbents for water purification and have adsorption capacity as much as comparable with the literature. In batch equilibrium studies, the adsorption of methylene blue dye onto the wheat hull, rice hull, and garlic stalk exhibited a significant correlation with temperature, contact time, and initial concentration of methylene blue dye and Adaptive Neuro-Fuzzy Inference System algorithm for forecasting overall the system parameter well fitted with these findings with the accuracy of outputs (R2 about 0.99 for each). Consequently, the thermodynamic analysis revealed that the adsorption process takes place in bulk diffusion by liquid phase mass transfer and occurred spontaneously with endothermically except garlic stalk. Adsorption thermodynamic studies show that the adsorption of methylene blue onto the garlic stalk was spontaneous and exothermic. Graphical Abstract

Scattering effect for relative blood volume monitoring during hemodialysis

The long-term survival rate of hemodialysis patients is limited by hemodialysis-related complications, which are attributed to the inappropriate level of relative blood volume (RBV) after treatment. For the conventional optical monitoring methods, the RBV is usually overestimated, especially when the RBV varies in a wide range. Here, we find that the scattering effect of blood on incident light is the dominant factor of nonlinear measurement errors according to the numerical simulation results. Then a computational model considering both the absorption and scattering effect of blood is proposed and applied to a relative blood volume monitoring system (RBVMS). Finally, the RBVMS is validated in a commercial hemodialysis machine, showing a relatively low measurement error of 6.9 %. This result indicates the potential of the system for RBV monitoring during hemodialysis.

Geometrical misalignment-induced nonlinear error in homodyne interferometers

This paper discusses the generation of a novel periodic nonlinear error in homodyne interferometers due to geometric misalignments. These misalignments arise from cumulative assembly errors among the sensor head interior, target mirror, test platform, and detector, leading to dynamic misplacement of the measurement beam on the detector's surface. A physical model was developed to explain this error, focusing on the interference field produced by Gaussian beams under conditions of beam separation and inclined interference. Observations from misaligned setups revealed a strong correlation between the modulation of the interference signal by an envelope curve and the distorted, complex patterns of Lissajous figures, with the movement of the target mirror. Numerical simulations and experimental results demonstrated that segmented elliptical fitting effectively calibrates vortex trajectories and substantially reduces periodic nonlinear errors. However, numerical simulations also uncovered previously undetected picometer-scale second-order nonlinear errors due to the geometric misalignments. This research highlights the physical mechanisms behind new nonlinear errors, emphasizing their importance in advancing homodyne interferometers toward picometer-level accuracy.

Handheld structured light system for panoramic 3D measurement in mesoscale

Abstract The measurement of complete 3D topography in mesoscale plays a vital role in high-precision reverse engineering, oral medical modeling, circuit detection, etc. Traditional structured light systems are limited to measuring 3D shapes from a single perspective. How to achieve high-quality mesoscopic panoramic 3D measurement remains challenging, especially in complex measured scenarios such as dynamic measurement, scattering medium, and high reflectance. To overcome these problems, we develop a handheld mesoscopic panoramic 3D measurement system for such complex scenes together with the fast point-cloud-registration and accurate 3D-reconstruction, where a motion discrimination mechanism is designed to ensure that the captured fringe is in a quasi-stationary case by avoiding the motion errors caused during fringe scanning; a deep neural network is utilized to suppressing the fringe-degradation caused by scattering mediums resulting to significantly improves the quality of the 3D point cloud; a strategy based on phase averaging is additionally proposed to simultaneously correct the saturation-induced errors and gamma nonlinear errors. Finally, the proposed system with a multi-threaded data processing framework is further developed to verify the proposed method and the corresponding experiments verify its feasibility.

Comparação das distribuições Normal, Logística, Laplace e t de Student para o erro experimental na descrição bayesiana do acúmulo de matéria seca de Allium sativum

ABSTRACT: This study assessed distributions associated with Bayesian nonlinear modeling error in the description of total plant dry matteraccumulation (TDMA) of Allium sativumas a function of days after planting (DAP). According to the DIC criterion, Logistic and Gompertzmodels that use student’s t distribution error exhibited the highest DIC with logistic error distribution. In general, the difference of DIC in all the scenarios was not more than 5.The Bayes factor (BF) criterion showed no difference in the Logistic and Gompertzmodel fit when four distributions are used for the errors, where BF values do not exceed 2. Posterior distributions and the usual estimators of Logistic and Gompertz model parameters were similar even forvaried error distribution. In summary, there was no difference in the use of 4 distributions associated with the modeling error of garlic plant growth by the Bayes factor, whereby the results showed that alternating between error distributions significantly changes the number of Markov Chain Monte Carlo (MCMC) iterations.

Photodegradation, kinetics and non-linear error functions of methylene blue dye using SrZrO3 perovskite photocatalyst

The degradation of methylene blue dye-contaminated wastewater via photocatalysis is an efficient approach towards environmental remediation. The SrZrO3 perovskite photocatalyst was synthesized using the modified Pechini sol-gel method, and characterized using XRD, FESEM, FTIR, and UV–visible spectrophotometer. Crystallite size obtained by the Scherrer and Williamson-Hall methods were 45.56 and 44.50 nm, respectively. The sample exhibited an orthorhombic crystal structure. The optical bandgap was estimated to be 5.31 eV. Kinetic study for the degradation of methylene blue dye using SrZrO3 in the presence of H2O2 showed complete decontamination of the methylene blue dye in the time interval of 90–120 min under visible light irradiation. The degradation efficiency was above 80.1 % under illumination and less than 40.1 % in dark. Kinetic studies were performed by varying the dose of photocatalyst and initial concentration of methylene blue. It was observed that higher dose of the photocatalyst and lower concentration of the contaminant produced higher rate of degradation. The solution pH 3 and catalysts dosage of 200 mg yielded the highest rate of degradation. The experimental data fitted best into the Psuedosecond order kinetic model with the highest R2 value, indicating a strong linear relationship. The experimental data was subjected into nonlinear error functions, where the Psuedo-second order kinetic model demonstrated lower values of error functions. The results suggest that the prepared SrZrO3 photocatalyst coupled H2O2 is a promising photocatalyst for the decontamination of methylene blue dye under visible light irradiation.

Analysisof Beam Walk in Inter-Satellite Laser Link: Implications for Differential Wavefront Sensing in Gravitational Wave Detection

Achieving space-based gravitational wave detection requires the establishment of an interferometer constellation. It is necessary to establish and maintain stable laser interferometric links using the differential wavefront sensing (DWS) technnique. When the distant measurement beam experiences pointing jitter, it causes beam walk on the surface of the local detector. The reduced overlap between the local reference spot and the distant spot increases the nonlinear errors in the DWS technique, which need to be suppressed. Numerical analysis was conducted on the spatial beam interference signals of the DWS technique when the distant measurement beam experienced pointing jitter. An experimental measurement system was designed, and the beam walk was suppressed using a conjugate imaging system. The results show that within a range of 300 μrad, the optical path with the imaging system can reduce measurement errors by at least 83%. This way also helps to reduce pointing jitter noise in inter-satellite links, thereby improving laser pointing control accuracy.This method would provide a valuable reference for future DWS measurement systems.

Position constrained adaptive time-varying formation control of autonomous surface vessels with uncertain dynamics

This paper investigates the adaptive time-varying formation control problem of autonomous surface vessels (ASVs) with position constraints, uncertain dynamics and external disturbances under directed communication topology. Different from the existing studies, the nonlinear error transformation function is combined with formation control to achieve position constraints of ASVs. Based on dynamic surface control and backstepping method, a virtual control law is designed for each vessel. Radial basis function neural networks are employed to approximate the unknown nonlinear continuous function caused by ASVs’ model uncertainties, and the minimum learning parameter (MLP) method is applied to reduce computational complexity. Then, a time-varying formation position constrained controller and an adaptive law are proposed for each ASV. By using the Lyapunov stability theory, it is proved that all signals of the closed-loop ASV system are semi-global uniformly ultimately bounded and the position constrained objective can be achieved. Finally, simulation analyses are given to verify the effectiveness of theoretical results.

A three-dimensional fiber Bragg grating wrist force sensor with separation elastic structure

PurposeThe use of a force sensor to estimate the external force of manipulator not only needs to deal with the signal noise of the sensor itself but also needs to solve the coupling interference of the sensor itself, especially the axial force. The purpose of this paper is to develop a three-dimensional fiber Bragg grating (FBG) wrist force sensor, which has a simple structure and reduces the coupling influence between several axes.Design/methodology/approachA particular separation elastic structure with four FBGs is devised for the three-axial force sensor. One FBG is suspended on the profile of central cylinder and the other three FBGs are pasted on the elastic beam surface of the over and under measuring bodies, respectively. Finite element analysis (FEA) simulation has been implemented to the strain distribution characteristics, the output characteristics of each direction and the coupling effects of the structure. Furthermore, theoretical derivation and experimental results are used to compare, which have a good consistency.FindingsThe experiment results show that the maximum repeatability error of the sensor is 6.75%, the maximum nonlinear error is 5.36%, the maximum coupling interference is 4.73% and the minimum sensitivity is 1.58 pm/N.Originality/valueA three-dimensional force sensor based on FBG adopts a particular separation elastic structure. The sensor can reduce the coupling influence between several axes, especially the coupling interference in the z-direction is 0.