Parameter Mismatch Research Articles

Chaos secure communication based on free-running VCSEL system

Abstract In this paper, we propose a parallel injection chaotic system involving three free-running 
vertical-cavity surface-emitting lasers (VCSELs). First, the chaotic synchronization 
performance of the system is evaluated using the cross-correlation function. Then, we analyze 
in detail the effects of injection strength, frequency detuning, and parameter mismatch on the 
chaotic synchronization and information transmission of the system. Numerical studies 
indicate that the proposed parallel injection chaotic system based on three VCSELs can 
achieve high-quality chaotic synchronization over a wide bandwidth and a broad range of 
input parameters. Furthermore, even in the case of parameter mismatch, high-quality chaotic 
synchronization and communication can still be achieved. Additionally, with appropriate 
injection strength, the system can compensate for the efficiency reduction caused by 
parameter mismatch.

Experimental validation of model-free predictive control based on the active vector execution time for grid-connected system

The application of Model-Free Predictive Control (MFPC) in power electronic systems has garnered increasing attention. In this paper, MFPC control based on replacing the classical factory model with an ultra-local model (ULM) is studied. Generally, the Integral Sliding Mode Observer (ISMO) is used to estimate the unknown part in the ULM where the non-physical factor in the ULM is selected with approximate values ​​ranging from the nominal value of the system which is contrary to the concept of MFPC control. In this research, an improved adaptive integral sliding mode observer (AISMO) based MFPC (AISMO-MFPC ) is proposed to estimate this factor with the unknown function in the ULM equation. The new observer design enables the estimation of this factor based on the current error, which allows for independent prposedcontrol of the system parameters.To obtain the lowest current ripple, the concept of active vector execution time (AVET ) has been incorporated into the proposed control where two vectors are selected in the sampling period to minimize the cost function instead of selecting a single vector. ULM is also used to calculate AVET which facilitates the implementation of the imposed control. The combination of the proposed AISMO-MFPC and AVET gives faster system response and reduces the current ripple and lower harmonics, especially in case of mismatch parameters. Finally, the effectiveness of the proposed control is confirmed under various conditions by the presented simulation and experimental results.

SPMSM Adaptive Control With Guaranteed Dynamic Response Under Parameter Mismatch

SPMSM Adaptive Control With Guaranteed Dynamic Response Under Parameter Mismatch

Challenges and strategies in estimating soil organic carbon for multi-cropping systems: a review

Multi-cropping systems play a crucial role in global agricultural production. Accurately estimating the soil carbon sequestration capacity of multi-cropping systems is of significant importance for enhancing agricultural productivity, mitigating greenhouse gas emissions, and reducing carbon footprint. However, soil carbon cycling is more complex in multi-cropping systems compared with single-cropping systems, and existing assessment methods cannot accurately estimate soil carbon sequestration in multi-cropping systems with high operability. Here, we reviewed the accuracy and efficiency of the three primary global soil carbon assessment methods, including statistical models, process-based models, and the Intergovernmental Panel on Climate Change (IPCC) steady-state method. Our study concludes that it is difficult to simulate the dynamic evolution of soil organic carbon (SOC) using the statistical models, while the well simulation through process-based models demands a large amount of data. Additionally, the IPCC Tier 2 method cannot be directly applied to estimate SOC in multi-cropping systems due to mismatches in parameters and time steps. We suggest modifying the structures and parameters of the IPCC Tier 2 method by revising the inventory unit and redetermining the parameter values, which should efficiently address its bottleneck in estimating SOC for multi-cropping systems. Moreover, long-term experimental observations and multi-model ensemble simulations are beneficial for determining the parameter values to address the data deficiencies in IPCC Tier 2. This study aims to explore pathways for improving the accuracy of SOC estimation in multi-cropping systems and, thus, carbon footprint calculation worldwide.

Improved sliding mode disturbance observer-based model-free finite-time terminal sliding mode control for IPMSM speed ripple minimization

The model-free sliding mode control with sliding mode disturbance observer (SMDO) for interior permanent magnet synchronous motor (IPMSM) is affected by feedback delays caused by mismatch of motor parameters. The observer is lagged behind the change of external disturbances, the speed tracking accuracy and transient control performance for IPMSM drives are reduced. In order to solve the issues, an improved higher-order sliding mode disturbance observer-based model-free finite-time terminal sliding mode control (HOSMDO-MFFTTSMC) strategy is proposed in this paper. First, a finite-time terminal sliding mode surface (FTTSMS) is designed, and a rotation speed-loop-based MFFTTSMC strategy is designed by combining the ultra-local model. The system control state is converged in finite time and the accurate tracking of observation error is realized. In addition, the non-singular fast terminal sliding mode is introduced into the observer, the higher-order SMDO is designed. The unknown part of disturbances is observed and compensated in real time, the fast-tracking response capability and anti-disturbance capability for IPMSM are improved, and the stator current harmonics are effectively suppressed. Finally, the proposed HOSMDO-MFFTTSMC strategy is experimentally demonstrated with a 6.6kW motor. The correctness and effectiveness of the HOSMDO-MFFTTSMC strategy are verified by simulation and experimental results.

Investigation of the kinematics of turning a wheeled vehicle with a variable track

BACKGROUND: The trapezoidal lever mechanism used in the steering drive for turning steerable wheels to change the direction of movement of a wheeled vehicle does not fully meet the conditions for observing rolling wheels without slipping and conforming to the correct kinematics of rotation, which is especially evident when adjusting the track. AIMS: assessment of the degree of discrepancy between the actual kinematics of the turn and the kinematics of the correct turn when changing the track of the tractor. MATERIALS AND METHODS: Analytical methods were used in the work, which made it possible to obtain some computational dependencies, perform a numerical analysis of the curvilinear motion of a tractor with a variable track for different parameters of the steering trapezoid, and on this basis establish patterns between the geometric characteristics of the steering trapezoid and the kinematic parameters. RESULTS: Rational geometric characteristics of the steering trapezoid, which make it possible to obtain the kinematic parameters of rotation closest to the required ones, are set for the most commonly used value of the width of the pivot track. For the Belarus-80.1 tractor, it corresponds to 1.02 m. At the same time, for example, at an angle of rotation of the inner steerable wheel of 25°, the minimum turning radius realized by the steering trapezoid is 0.6521 m (10.44%), and at 40° by 0.2829m (9.27%) differs from their values obtained from the pure rolling condition. When changing the track width of the machine, there is a violation of the initial geometric characteristics of the trapezoid and the corresponding mismatch of the kinematic parameters of the rotation carried out by the steering trapezoid and by the correct rotation increases. A comparison of the minimum turning radii at an angle of 25° and a pivot track of 1.42 m showed an increase of 3.2340 m (35.83%), and at 40° — by 0.8956 m (20.21%). CONCLUSION: To ensure the correct turn, it is necessary to conduct a thorough theoretical analysis of the never mechanism of the steering trapezoid and improve its design on this basis.

Heterogeneity-provoked pulse generation in coupled excitable elements.

Pulse generation in a spatially extended system is studied numerically. Using an array of coupled excitable oscillators, pulse generation is achieved by introducing a parametric heterogeneity between the two partitions of the array. The profile of the propagating pulses can be regulated using the parameter mismatch between these two partitions. It is realized, using a simplified two linearly coupled model, that the coupling flux between the excitable elements plays a vital role in enabling the observed pulse propagation. Analytical treatment, involving linear stability analysis, validates the simulation results.

SSO optimized FOFPID regulator design for performance enhancement of doubly fed induction generator based wind turbine system.

A wind turbine system (WTS) is a highly coupled and nonlinear system where the output power depends upon highly uncertain wind speed. Therefore, the quality of produced power becomes a challenging problem for researchers. Direct Vector Control (DVC) is a powerful and widely utilized power control strategy to deal with winds that vary rapidly and randomly. As a result, this article employed the newly developed Social Spider Optimization (SSO) technique to optimize the design parameters of Fractional-Order Fuzzy Proportional-Integral with Derivative (FOFPID) regulator to maintain the output power of the studied DFIG-based WTS at the rated value under dynamic wind conditions. The suggested FOFPID controller integrates the capabilities of the Fuzzy intelligent regulator and the Fractional-Order controller, enhancing DFIG current control while allowing independent control of active and reactive power. The approach is incorporated within the DVC strategy of the DFIG's rotor-side converter (RSC), replacing the conventional Proportional-Integral (PI) regulator in the internal current loops. Extensive performance evaluations are conducted under various operating conditions, including active power reference changes, parameter uncertainties, and rapid wind speed variations. Comparative analyses with SSO-optimized PID and Fuzzy regulators show that the FOFPID regulator performs better in terms of maximum overshoot, extreme undershoot, settling time, Total Harmonic Distortion (THD), and Weighted Total Harmonic Distortion (WTHD). The suggested FOFPID regulator also displays stronger robustness against parameters mismatch and weather change than other regulator architectures.

Deadbeat predictive current control for high-speed permanent magnet synchronous motor based on extended state observer

Abstract Addressing the serious issue of delays in the high-speed controlling area and the impact of motor parameter mismatches on current loop performance, this paper proposes a high-speed PMSM current control method based on an extended state observer (ESO). To improve the angle delay, a leading phase angle is introduced for compensation. Additionally, a one-step-ahead predictive compensation for time delay is included in the control method to reduce the time delay. The ESO is also employed to estimate electrical parameters and compensate for control errors, enhancing the robustness. The simulation validates the effectiveness of the method.

Effect of Thermal Processing on the Structural and Magnetic Properties of Epitaxial Co2FeGe Films.

The structure and magnetic properties of epitaxial Heusler alloy films (Co2FeGe) deposited on MgO (100) substrates were investigated. Films of 60 nm thickness were prepared by magnetron co-sputtering at different substrate temperatures (TS), and those deposited at room temperature were later annealed at various temperatures (Ta). X-ray diffraction confirmed (001) [110] Co2FeGe || (001) [100] MgO epitaxial growth. A slight tetragonal distortion of the film cubic structure was found in all samples due to the tensile stress induced by the mismatch of the lattice parameters between Co2FeGe and the substrate. Improved quality of epitaxy and the formation of an atomically ordered L21 structure were observed for films processed at elevated temperatures. The values of magnetization increased with increasing TS and Ta. Ferromagnetic resonance (FMR) studies revealed 45° in-plane rotation of the easy anisotropy axis direction depending on the degree of the tetragonal distortion. The film annealed at Ta = 573 K possesses the minimal FMR linewidth and magnetic damping, while both these parameters increase for another TS and Ta. Overall, this study underscores the crucial role of thermal treatment in optimizing the magnetic properties of Co2FeGe films for potential spintronic and magnonic applications.

Exponential Quasi-Synchronization of Fractional-Order Fuzzy Cellular Neural Networks via Impulsive Control

This paper investigates the exponential quasi-synchronization of fractional-order fuzzy cellular neural networks with parameters mismatch via impulsive control. Firstly, under the framework of the generalized Caputo fractional-order derivative, a new fractional-order impulsive differential inequality is established. Secondly, based on this fractional-order impulsive differential inequality, a general criterion for the quasi-synchronization of fractional-order systems is obtained. Then, specific to the fractional-order fuzzy cellular neural network model in this paper, the criteria and error estimation of the exponential quasi-synchronization of fractional-order fuzzy cellular neural networks can be obtained. Finally, two numerical examples are given to illustrate the effectiveness of the obtained results.

Stability of networked control systems under malicious attacks and bit rate constraints

This article investigates the stability of networked control systems under two types of malicious attacks and bit rate constraints. The malicious attacks may lead to parameter mismatches, including scaling variable mismatches between the encoder and decoder sides and discrepancies between the data sent by the encoder and received by the decoder, causing system instability. To address these issues, scaling variable update rules are proposed for the encoder and decoder sides separately to mitigate the adverse effects of malicious attacks. A control strategy featuring a compensation term is designed to counteract the detrimental impacts of the mismatch. A lower bound on the bit rate is established to prevent quantization saturation and achieve exponential stability of the system. Finally, confirmatory and comparative simulations showcase the effectiveness of the theoretical insights and the merits of the proposed strategies, respectively.

Fourier Transform Approach to Boundary Domain Integral Equations for Elastic Composites With Domain Decomposition and Multi Reference Parameters

ABSTRACTIn this article, displacement and strain periodic boundary domain integral equations for homogenization problems of elastic composites are derived in the context of FFT homogenization methods. The resolution methods based on regular grids and discrete Green's tensors are presented. The displacement based equations can be used to solve problems in arbitrary domains under periodic and non‐periodic boundary conditions. The strain based integral equation is obtained from the combination of the displacement based equations for different domains, each one having its own reference elasticity tensor. In the latter, the strain values inside every phases are connected to material mismatch parameters on the phase boundary. It was shown that by decomposing suitably domains by stiffness and using adapted reference parameters, the iteration schemes converge faster.

Integrated Motion Control Strategy Considering Parameter Robustness for Distributed Vehicle by Wire

<div>To address the issues of functional conflicts in execution subsystems and the deterioration of control performance due to model parameter uncertainties in the motion control of distributed vehicle by wire, this article proposes an integrated control strategy considering parameter robustness. This strategy aims to compensate for model mismatch, resolve functional conflicts, and achieve motion coordination. Based on the over-actuation characteristics of distributed vehicle by wire, this article constructs the dynamic model and utilizes the tire cornering properties along with phase portraits to delineate the working regions of the execution subsystems. To deal with model parameter uncertainties and mismatch, tube-based model predictive control (tube-based MPC) is applied to the control strategy design, which compensates for model deviations through state feedback and constructs a robust positively invariant set (RPI) to constrain the system state. Correspondingly, the weights of control inputs are adjusted adaptively, according to the working regions, to optimize the coordination logic of integrated control. In order to verify the effectiveness and feasibility of the strategy, extreme driving condition tests are executed on hardware-in-the-loop (HIL) and real vehicle test platforms. The test results indicate that the strategy proposed in this article is able to reduce the sideslip angle and tracking error of yaw rate, improve driving stability under extreme conditions through integrated control, and especially, it can still maintain precise stability control performance under severe model mismatch, exhibiting strong robustness facing parameter uncertainties.</div>

Robust deadbeat predictive current control for unipolar sinusoidal excited SRM with multi-parameter mismatch compensation

In the control of unipolar sinusoidal excited switched reluctance motors (SRMs), deadbeat predictive current controllers (DPCCs) have gained attention for their enhanced dynamic performance. However, periodic disturbances caused by mismatches between the predictive model’s nominal and actual system parameters degrade the control performance of SRMs. To address this issue, a robust DPCC with multi-parameter compensation is proposed to improve dq0-axes current control performance. By analyzing the impact of parameter mismatches, a Kalman filter (KF) is developed to compensate for inductance coefficient mismatches, mitigating periodic disturbances. Additionally, a disturbance estimator with measurement noise suppression is integrated into the DPCC for both state and disturbance estimation to handle residual uncertainties, including winding resistance mismatches, magnetic saturation, and unmodeled dynamics. Compared simulation and experimental results validate the effectiveness of the proposed robust DPCC.

Chaotic laser time series prediction based on an improved logistic mapping algorithm echo state network

Chaos synchronization plays vital functions in the fields of optical chaos secure communication. The synchronization performance can be significantly degraded by parameter mismatches between the chaotic transmitter and receiver. In this paper, the Deep-Logistical Mapping Echo State Network (D-LMESN) is proposed to enhance the performance of chaos synchronization. The network is upgraded by using an improved logical mapping algorithm and a deep reserve pool structure with phase space reconstruction. Results show that D-LMESN exhibits better performance in the prediction of chaotic time series, thanks to the adaptive parameter adjustment, which increases the ability to capture the dynamic characteristics of complex systems. Compared with ESN, the mean square error of this model is reduced by 55% and 72%, respectively, in chaotic laser simulation and actual data experiments. This provides a new possibility, to our knowledge, for the development of chaotic secure communication.

Current disturbance compensation of continuous model predictive control scheme for PMSMs

During the operation of a permanent magnet synchronous motor, limitations imposed by digital chips inevitably result in certain delays. Additionally, external environmental factors introduce variations in motor parameters. This study aims to comprehensively analyze these issues. Firstly, the control delay and disturbances caused by motor parameter changes are transformed into current disturbances using a uniform approach. Secondly, various sliding mode model predictive controllers are designed to effectively suppress the current disturbances arising from aforementioned reasons. Moreover, considering controller implementation aspects, this paper thoroughly discusses the influence of core controller parameters on current disturbances and their adaptability toward different parameter mismatches. Furthermore, extensive examination is conducted on global stability conditions for controller realization. Finally, experimental results validate that the proposed methods successfully optimize current disturbances originating from aforementioned causes.

Foetal Microchimerism Correlates With Foetal-Maternal Histocompatibility Both During Pregnancy and Postpartum.

Foetal cells are detectable in women decades postpartum, a state termed foetal microchimerism. The interplay between these semi-allogeneic foetal cells and the mother could be affected by genetic mismatches in the HLA loci. Here, we relate HLA allele and molecular mismatch values to the presence and quantity of foetal microchimerism in the maternal circulation during pregnancy and postpartum. A total of 76 pregnant women were included, of which 59 were followed up 1-8 years postpartum. Maternal and foetal DNA was genotyped for HLA class I and II loci. Foetal cells in maternal buffy coat were detected by qPCR, targeting inherited paternal alleles. Antibody-verified eplet mismatch and Predicted Indirectly Recognisable HLA Epitopes (PIRCHE) scores were calculated to quantify foetal-maternal histocompatibility from the mother's perspective. Circulating foetal cells were detected in 50.0% (38/76) of women during pregnancy, and 25.4% (15/59) postpartum. During pregnancy, HLA class II antibody-verified eplet mismatch load and PIRCHE scores correlated negatively with the presence and quantity of foetal cells in the maternal circulation. Postpartum, HLA class I allele mismatches correlated negatively with foetal microchimerism presence, while HLA class II allele mismatches, HLA class I and II antibody-verified eplet mismatch load, and PIRCHE-I and PIRCHE-II scores correlated negatively with both microchimerism presence and quantity. The correlation between mismatch parameters aimed at evaluating the risk of humoral and T cell-mediated allorecognition and foetal microchimerism was more evident postpartum than during pregnancy. The observed predictive effect of foetal-maternal histocompatibility on foetal microchimerism suggests that circulating foetal cells are subject to clearance by the maternal immune system. We propose that allorecognition of foetal cells in the maternal circulation and tissues influences any long-term effect that foetal microchimerism may have on maternal health.

Transition among oscillation death, amplitude death, and revival of oscillation in coupled time-delayed systems with diffusivity and common environment

In this paper, we study the transition between different oscillation suppression, revival of oscillation, and oscillatory states in time-delayed chaotic oscillators coupled through simultaneous diffusive and environmental coupling. The present paper, for the first time, reports the occurrence of oscillation death and nontrivial amplitude death states in coupled intrinsic time-delayed systems. Moreover, we explore the revival of the oscillations from these diverse oscillation suppression states. We analyze the stability of the coupled time-delayed system and through extensive numerical investigations, we delineate all the dynamical states in the parameter space. The study is extended to a network of time-delayed oscillators and identical transition scenarios have been obtained. Finally, we support our results in an electronic hardware circuit-based experiment and demonstrate that all the transition scenarios are robust enough in a real world system where the presence of noise, fluctuations, and parameter mismatch are inevitable.

ENHANCED MODEL-FREE PREDICTIVE CONTROL FOR VOLTAGE SOURCE INVERTERS USING AN ADAPTIVE OBSERVER

In this paper, a free model predictive control based on the active vector execution time (AVET-MFPC) using an adaptive observer is proposed for two-level voltage source inverters. The traditional model-free predictive control (MFPC) uses the sampling period to select one voltage vector for all candidate vectors according to the minimizing cost function principle. With the proposed control, two vectors are selected at one sampling period. The first vector is an active vector that uses the execution time of the active vector to select it, while the second one is a zero vector as it is applied after the active vector. The execution time is calculated using the ultra-local model (ULM) equation. In the traditional MFPC, the factor in the ULM is chosen with approximate values ranging between ±50 % of the nominal value. This paper proposes an adaptive sliding mode observer (ASMO) with an improved design to observe the variation of this factor, especially in case of mismatch parameters and during a step change in the reference signal. Combining the proposed ASMO observer and the AVET-MFPC controller gives faster system response, good tracking results, and less computational burden. Finally, the effectiveness of the proposed control model is approved and confirmed under various conditions, as well as the simulations carried out and the results obtained.