A feedback control method for phase signal demodulation in fber-optic hydrophones

In the realm of acoustic signal detection,the identification of weak signals,particularly in the presence of negative signal-to-noise ratios,poses a significant challenge.This challenge is further heightened when signals are acquired through fiber-optic hydrophones,as these signals often lack physical significance and resist clear systematic modeling.Conventional processing methods,e.g.,low-pass filter(LPF),require a thorough understanding of the effective signal bandwidth for noise reduction,and may introduce undesirable time lags.This paper introduces an innovative feedback control method with dual Kalman filters for the demodulation of phase signals with noises in fiber-optic hydrophones.A mathematical model of the closed-loop system is established to guide the design of the feedback control,aiming to achieve a balance with the input phase signal.The dual Kalman filters are instrumental in mitigating the effects of signal noise,observation noise,and control execution noise,thereby enabling precise estimation for the input phase signals.The effectiveness of this feedback control method is demonstrated through examples,showcasing the restoration of low-noise signals,negative signal-to-noise ratio signals,and multi-frequency signals.This research contributes to the technical advancement of high-performance devices,including fiber-optic hydrophones and phase-locked amplifiers.

Research on Teaching Methods of Flight Control Principles

With the rapid development of China’s civil aviation industry,the teaching method of operating knowledge of flight principles has changed greatly,which creates a good implementation environment to improve the safety of civil aviation in our country.At present,the main training content of air route transport pilots in China is basic aviation theory,initial flight training,airline modification,etc.The principles of flight control are an important part of basic aviation theoretical knowledge training,which will involve a large number of flight technology training content,instructors will also be based on the pilot type.Teaching flight control theory and practical knowledge requires relatively high theoretical learning ability of students,and the learning effect of this part of theoretical knowledge will directly affect the quality of subsequent learning,but also directly affect the effectiveness of flight training.This paper focuses on the analysis of the basic concepts of flight control,studies the existing problems in the teaching of flight control principles,summarizes the teaching measures of flight control principles,aiming to provide a reference to teaching personnel.

含时滞的不确定性交直流微电网直流母线电压H_∞控制

针对含通信网络延时的不确定性交直流微电网的直流母线电压稳定问题,提出了一种将状态空间法和阻抗分析法相融合的方法,构建具有时滞的范数有界不确定交直流微电网模型。基于系统鲁棒二次稳定的求解,获得了满足H_∞控制性能的时滞无关型状态反馈控制器的条件。然后应用S-procedure定理,提出一种降低时滞依赖型Lyapunov方法的泛函构造难度且无须再次求导的方法,引用Wirtinger积分不等式和自由矩阵的积分不等式,得到时滞依赖型的H_∞控制器。仿真分析验证了所提控制方法能在一定的通信延时约束下抑制不确定参数对直流母线电压的影响。

Performance enhancement of a viscoelastic bistable energy harvester using time-delayed feedback control

This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting efficiency. Firstly, to obtain the dimensionless governing equation of the system, the original bistable system is approximated as a system without viscoelastic term by using the stochastic averaging method of energy envelope, and then is further decoupled to derive an equivalent system. The credibility of the proposed method is validated by contrasting the consistency between the numerical and the analytical results of the equivalent system under different noise conditions. The influence of system parameters on average output power is analyzed, and the control effect of the time-delayed feedback control on system performance is compared. The output performance of the system is improved with the occurrence of stochastic resonance(SR). Therefore, the signal-to-noise ratio expression for measuring SR is derived, and the dependence of its SR behavior on different parameters is explored.

Failure evaluation and control factor analysis of slope block instability along traffic corridor in Southeastern Tibet

The instability of slope blocks occurred frequently along traffic corridor in Southeastern Tibet(TCST),which was primarily controlled by the rock mass structures.A rapid method evaluating the control effects of rock mass structures was proposed through field statistics of the slopes and rock mass structures along TCST,which combined the stereographic projection method,modified M-JCS model,and limit equilibrium theory.The instabilities of slope blocks along TCST were then evaluated rapidly,and the different control factors of instability were analyzed.Results showed that the probabilities of toppling(5.31%),planar(16.15%),and wedge(35.37%)failure of slope blocks along TCST increased sequentially.These instability modes were respectively controlled by the anti-dip joint,the joint parallel to slope surface with a dip angle smaller than the slope angle(singlejoint),and two groups of joints inclined out of the slope(double-joints).Regarding the control effects on slope block instability,the stabilization ability of doublejoints(72.7%),anti-dip joint(67.4%),and single-joint(57.6%)decreased sequentially,resulting in different probabilities of slope block instability.Additionally,nearby regional faults significantly influenced the joints,leading to spatial heterogeneity and segmental clustering in the stabilization ability provided by joints to the slope blocks.Consequently,the stability of slope blocks gradually weakened as they approached the fault zones.This paper can provide guidance and assistance for investigating the development characteristics of rock mass structures and the stability of slope blocks.

Research trends in methods for controlling macro-micro motion platforms

With ongoing economic,scientific,and technological developments,the electronic devices used in daily lives are developing toward precision and miniaturization,and so the demand for high-precision manufacturing machinery is expanding.The most important piece of equipment in modern high-precision manufacturing is the macro-micro motion platform(M3P),which offers high speed,precision,and efficiency and has macro-micro motion coupling characteristics due to its mechanical design and composition of its driving components.Therefore,the design of the control system is crucial for the overall precision of the platform;conventional proportional–integral–derivative control cannot meet the system requirements,and so M3Ps are the subject of a growing range of modern control strategies.This paper begins by describing the development history of M3Ps,followed by their platform structure and motion control system components,and then in-depth assessments of the macro,micro,and macro-micro control systems.In addition to examining the advantages and disadvantages of current macro-micro motion control,recent technological breakthroughs are noted.Finally,based on existing problems,future directions for M3P control systems are given,and the present conclusions offer guidelines for future work on M3Ps.

四旋翼悬挂负载系统预设有限时间H_∞容错控制

在实际飞行中,四旋翼飞行器悬挂负载系统容易受到负载摆动以及外部扰动的影响,且可能出现执行器故障。针对此问题,本文基于反步法设计有界H_(∞)容错控制器来抑制外部扰动并消除执行器故障的影响,利用神经网络逼近系统中负载的不确定性,同时引入预设有限时间性能函数,使得四旋翼飞行器即使在负载和外部扰动的影响下,其跟踪误差仍能被约束在预先给定的范围内。所设计的控制器能够保证系统在较精确地跟踪参考轨迹的同时具有较高的抗干扰性能。仿真验证了所设计的控制器的有效性。

A new optimal adaptive backstepping control approach for nonlinear systems under deception attacks via reinforcement learning

In this paper,a new optimal adaptive backstepping control approach for nonlinear systems under deception attacks via reinforcement learning is presented in this paper.The existence of nonlinear terms in the studied system makes it very difficult to design the optimal controller using traditional methods.To achieve optimal control,RL algorithm based on critic–actor architecture is considered for the nonlinear system.Due to the significant security risks of network transmission,the system is vulnerable to deception attacks,which can make all the system state unavailable.By using the attacked states to design coordinate transformation,the harm brought by unknown deception attacks has been overcome.The presented control strategy can ensure that all signals in the closed-loop system are semi-globally ultimately bounded.Finally,the simulation experiment is shown to prove the effectiveness of the strategy.

Respiratory Mechanics, Respiratory Muscle Strength, Control of Ventilation and Gas Exchange in Patients with Autoimmune Liver Disease

Objectives: To assess respiratory elastance and resistive properties in patients with autoimmune liver disorders using the passive relaxation expiration technique and compare findings to a group of patients with non-autoimmune liver disease and control subjects. These findings were then related to control of ventilation and gas exchange. A secondary objective was to assess respiratory muscle strength and gas exchange and their relation to respiratory mechanics. Methods: Measurements included respiratory elastance and resistance using the passive relaxation method. Pulmonary function, gas exchange and control of ventilation were assessed using standard methods. Results: a) Compared to control subjects, Ers in patients with liver disease was on average 50% greater than in controls;b) mean respiratory resistance, expressed as the respiratory constants, K1 and K2 in the Rohrer relationship, Pao/V’ = K1 + K2V’, was not different from control resistance;c) mean maximal inspiratory and maximal expiratory pressures averaged 36% and 55% of their respective control values;d) inspiratory occlusion pressure in 0.1 sec (P0.1) was increased and negatively associated with FVC;and e) increases in P0.1, mean inspiratory flow (Vt/Ti) and presence of respiratory alkalosis confirmed the increase in ventilatory drive. Despite inspiratory muscle weakness in patients, P0.1/Pimax averaged 5-fold higher than in control subjects. Conclusions: Despite inspiratory muscle weakness and a V’E similar to that in normal subjects, central drive is increased in patients with chronic liver disease. The increase in ventilatory drive is related to smaller lung volumes and weakly associated with increase in respiratory elastance. Findings confirm that P0.1 is a reliable measure of central drive and is an approach that can be used in the evaluation of control of ventilation in patients with chronic liver disease.

Dynamic modelling and chaos control for a thin plate oscillator using Bubnov–Galerkin integral method

The utilization of thin plate systems based on acoustic vibration holds significant importance in micro-nano manipulation and the exploration of nonlinear science. This paper focuses on the analysis of an actual thin plate system driven by acoustic wave signals. By combining the mechanical analysis of thin plate microelements with the Bubnov–Galerkin integral method, the governing equation for the forced vibration of a square thin plate is derived. Notably,the reaction force of the thin plate vibration system is defined as f=α|w|, resembling Hooke’s law. The energy function and energy level curve of the system are also analyzed. Subsequently, the amplitude–frequency response function of the thin plate oscillator is solved using the harmonic balance method. Through numerical simulations, the amplitude–frequency curves are analyzed for different vibration modes under the influence of various parameters. Furthermore, the paper demonstrates the occurrence of conservative chaotic motions in the thin plate oscillator using theoretical and numerical methods. Dynamics maps illustrating the system’s states are presented to reveal the evolution laws of the system. By exploring the effects of force fields and system energy, the underlying mechanism of chaos is interpreted. Additionally, the phenomenon of chaos in the oscillator can be controlled through the method of velocity and displacement states feedback, which holds significance for engineering applications.

Controllable Modulation of Morphology and Property of CsPbCl_(3)Perovskite Microcrystals by Vapor Deposition Method

As a direct wide bandgap semiconductor,CsPbCl_(3)has great potential applications in the eld of near-ultraviolet photodetectors,lasers and higher-order multiphoton uores-cent detectors.In this work,we synthesized CsPbCl_(3)micro/nanocrystals by vapor depo-sition method with CsCl and PbCl_(2)powders as the source materials.It was con rmed that the formation of CsPbCl_(3)perovskite through the chemical reaction of CsCl with PbCl_(2)occurred in the quartz boat before the source evaporation,not in vapor or on sub-strate surface.The evaporated CsPbCl_(3)can form micro/nanocrystals on substrate surfaces under appropriate conditions.Various morphologies including irregular polyhedrons,rods and pyramids could be observed at lower temperature,while stable and uniform CsPbCl_(3)single crystal microplatelets were controllably synthesized at 450℃.Prolonging the growth time could modulate the size and density of the microcrystals,but could not change the morphology.Substrate types made little di erence to the morphology of CsPbCl_(3)crystals.The photoluminescence spectra indicated that the crystallinity and morphology of CsPbCl_(3)micro/nanocrystals have signi cant e ects on their optical properties.The work is expected to be helpful to the development of optoelectronic devices based on individual CsPbCl_(3)microcrystal.

Mixed H_2/H_∞ State Feedback Attitude Control of Microsatellite Based on Extended LMI Method

For the appearance of the additive perturbation of controller gain when the controller parameter has minute adjustment at the initial running stage of system,to avoid the adverse effects,this paper investigates the mixed H_2/H_∞ state feedback attitude control problem of microsatellite based on extended LMI method.Firstly,the microsatellite attitude control system is established and transformed into corresponding state space form.Then,without the equivalence restriction of the two Lyapunov variables of H_2 and H∞performance,this paper introduces additional variables to design the mixed H_2/H_∞ control method based on LMI which can also reduce the conservatives.Finally,numerical simulations are analyzed to show that the proposed method can make the satellite stable within 20 s whether there is additive perturbation of the controller gain or not.The comparative analysis of the simulation results between extended LMI method and traditional LMI method also demonstrates the effectiveness and feasibility of the proposed method in this paper.

STATE SPACE METHODS FOR DECENTRALIZED H_∞ CONTROL

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VARIATIONAL METHOD AND COMPUTATION FOR H_∞ CONTROL

The variational approach is further applied to the measurement feedback H ∞ control problems. Based on the induced norm description of the system Γ,the variational functionals J c and J p of state feedback H ∞ control for the future time interval (t,t f ], and of H ∞ filter for the past time interval [0,t), respectively, are combined together to generate the variational functional of the measurement feedback for the whole time interval [0,t f ]. The connection condition at the present time t is that the estimated state vector (t) must be continuously extended to be the initial condition of the future state vector estimation. Another connection condition for the dual vector λ(t) can be naturally derived from the variational principle. The equations thus derived show that the third condition for the optimal parameter γ -2 cr is again a bound of the smallest Rayleigh quotient. Therefore, the precise integration method developed formerly to determine the optimal parameter γ -2 cr of H ∞ control and of H ∞ filter respectively can be further applied to the determination of the optimal parameter.

具有介质访问约束的网络化控制系统H∞状态估计

研究了一类存在介质访问约束和信号量化的网络化控制系统的H∞状态估计问题。首先,考虑到介质访问约束和信号量化的影响,将信号量化误差转化为扇形有界的不确定性,对由于访问约束而未获得网络传输的系统输出采用加权补偿策略,根据网络介质的随机访问机制将网络化系统建模为具有不确定性的马尔可夫跳跃系统。然后,在此基础上借助李雅普诺夫稳定性理论和H∞性能约束条件,利用线性矩阵不等式(linear matrix inequality,LMI)方法给出状态估计器存在的充分条件,所设计的状态估计器使得估计误差系统渐近稳定且具有给定的H∞性能。最后,通过仿真实例验证了该设计方法的有效性。

基于自抗扰控制的H桥逆变器的混沌研究

为了解决新能源发电系统逆变器出现混沌的问题,提出了一种基于自抗扰控制的H桥逆变器的调节方案。针对处于混沌状态的逆变器的稳态和动态特性差的现象,构建了逆变器的离散模型,并通过建立跟踪微分器、扩张状态观测器以及状态误差反馈控制律进行混沌控制。通过分岔图、折叠图以及仿真分析,结果可知基于自抗扰控制的H桥逆变器比基于比例控制的H桥逆变器的稳定范围扩大了45%,有效地抑制了混沌现象的发生。通过分析可得出:该控制策略对系统的混沌行为能够进行抑制,拓宽了系统稳定工作范围。

基于截面增大法的扣放角钢焊接加固负载H型钢的轴压承载力研究

负载下焊接加固是既有结构加固的重要形式,然而当前对加固形式及加固效果的研究仍然较为缺乏.因此,提出了一种新型负载焊接加固构造,设计了8组扣放角钢焊接加固H型钢试验.研究了焊接过程中的截面应力重分布规律以及焊接加固H型钢柱的轴压力学性能.试验中加固构件的截面为加固前的1.53倍~1.55倍,焊接加固后构件极限承载增大为加固前的1.74倍~1.90倍;加固构件和原构件协同工作,获得了良好的加固效果,虽然焊接热输入降低了构件焊缝间隔处的屈曲应力,但负载加固的构件表现出相对零载加固构件更高的极限承载力.随后建立并验证了一种新型焊接加固H型钢柱的数值模拟方法,探究了不同截面面积加固构件的加固效果;揭示了不同焊缝间隔以及焊接热效应对加固构件极限承载力的影响,并建立了相应的设计方法.

带扰动补偿的永磁同步电机鲁棒H∞控制

为了提高永磁同步电机调速系统的抗干扰能力,提出了一种鲁棒H∞控制方法。首先,根据鲁棒H∞控制原理,提出了永磁同步电机H∞速度控制设计方法,并介绍了求解方法。设计加权函数时考虑了跟踪性能、干扰抑制、输出限制和模型不确定性。通过伯德图详细说明了性能加权函数对动态性能的影响,并给出了加权函数的设计方法。然后,在考虑参数不确定性和未建模动态的情况下,为进一步提高系统的抗干扰能力,通过Luenberger扰动观测器将扰动作为前馈补偿观测,并将其反馈到速度控制器中,以加速动态响应,增强对扰动的抑制能力。最后,通过试验对比了传统比例积分控制器、H∞速度控制器和所提的复合速度控制器,试验结果验证了所提复合速度控制器的有效性。

基于最小二乘法和BP神经网络的磁流变阻尼器H-B模型参数辨识方法

针对Bingham模型磁流变阻尼器由于剪切稀化效应带来的阻尼力计算误差,在理论和仿真分析的基础上,提出一种最小二乘法和BP神经网络相结合的方法,对磁流变阻尼器H-B模型进行参数辨识,获得各参数与电流的关系,从而对磁流变阻尼器的阻尼力进行准确计算。最后通过磁流变阻尼器实验对理论方法进行验证。结果表明:借助于磁流变阻尼器的仿真分析,最小二乘法和BP神经网络相结合的磁流变阻尼器H-B模型参数辨识方法精确度高、吻合性好,验证了参数辨识结果的通用性及准确性。

碳纤维板加固H型钢梁抗剥离夹具研制及应用试验

外贴碳纤维板是钢梁抗弯加固的常用方法,但其端部易因界面应力集中导致剥离破坏,严重影响高性能材料的有效利用,特别是结构加固后的安全服役.为此开发出一种适用于H型钢梁的简易夹具——C形槽板夹,以加强碳纤维板的端部锚固.通过多根带夹碳纤维板加固梁的静力加载试验,验证了此夹具的可靠性,并考察了碳纤维板伸入剪跨段长度与剪跨段长度之比及锚固方式(纯粘、端锚和混锚)对加固效果的影响.研究发现端锚加固不同于纯粘,只要梁的控制截面仍在夹具之间,碳纤维板的极限应力、加固效果及利用效率均随其长度缩短而提高,当碳纤维板长度分别为600、750 mm时,前者极限应变和承载力比后者分别高27.3%和8.1%.由于钢梁表面处理质量较差,混锚加固梁均发生突然剥离,后期退化为端锚加固梁,因而相比端锚加固梁加固效果改善不大,需要提高表面处理质量再做类似研究.尽管如此,相比纯粘加固梁,混锚加固梁采用C形槽板夹后剥离破坏被延迟,抗弯性能大为改善.试验过程中还用压电阻抗法对界面剥离情况进行了检测,结果符合实际.