Observer-based robust high-order fully actuated attitude autopilot design for spinning glide-guided projectiles

This paper investigates the design of an attitude autopilot for a dual-channel controlled spinning glideguided projectile(SGGP),addressing model uncertainties and external disturbances.Based on fixed-time stable theory,a disturbance observer with integral sliding mode and adaptive techniques is proposed to mitigate total disturbance effects,irrespective of initial conditions.By introducing an error integral signal,the dynamics of the SGGP are transformed into two separate second-order fully actuated systems.Subsequently,employing the high-order fully actuated approach and a parametric approach,the nonlinear dynamics of the SGGP are recast into a constant linear closed-loop system,ensuring that the projectile's attitude asymptotically tracks the given goal with the desired eigenstructure.Under the proposed composite control framework,the ultimately uniformly bounded stability of the closed-loop system is rigorously demonstrated via the Lyapunov method.Validation of the effectiveness of the proposed attitude autopilot design is provided through extensive numerical simulations.

Laser shaping and optical power limiting of pulsed Laguerre–Gaussian laser beams of high-order radial modes in fullerene C60

We study the strong nonlinear optical dynamics of nanosecond pulsed Laguerre–Gaussian laser beams of high-order radial modes with zero orbital angular momentum propagating in the fullerene C60molecular medium. It is found that the spatiotemporal profile of the incident pulsed Laguerre–Gaussian laser beam is strongly reshaped during its propagation in the C60molecular medium. The centrosymmetric temporal profile of the incident pulse gradually evolves into a noncentrosymmetric meniscus shape, and the on-axis pulse duration is clearly depressed. Furthermore, the field intensity is distinctly attenuated due to the field-intensity-dependent reverse saturable absorption, and clear optical power limiting behavior is observed for different orders of the input pulsed Laguerre–Gaussian laser beams before the takeover of the saturation effect;the lower the order of the Laguerre–Gaussian beam, the lower the energy transmittance.

Integrated of Proximity-Coupling High-Order Modes Patch Antenna with Solar Cells for Sustainable Communication

An integration of single-layer proximitycoupling patch antenna and solar cells with bandwidth enhancement and optical energy harvesting is proposed for sustainable communication.For this purpose,many dual-function components are selected for designing the miniaturized solar cell antenna.On the one hand,by greatly affecting the current flow of the rectangular patch,vias and proximity-coupling are introduced to control the resonance modes frequency and matching,respectively,for wideband application,and the radiation performance property can be achieved by high-order mode.On the other hand,vias and proximity-coupling are beneficial to complete direct-current(DC)loop of solar cell and improve compatibility of DC-RF(radio frequency),whereas a high-order mode is beneficial to increase the area of collected light energy.To prove the working principle,fabricated and manufactured solar cell antenna.The measured and simulated results illustrate that the solar cell antenna gain is raised to as high as 9.27 d Bi in4.37 to 5.06 GHz applied to fifth generation communication(5G).

Micro-Sized Pinhole Inspection with Segmented Time Reversal and High-Order Modes Cluster Lamb Waves Based on EMATs

Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspection method based on segmented time reversal(STR)and high-order modes cluster(HOMC)Lamb waves.First,the principle of defect echo enhancement using STR is introduced.Conventional and STR inspection experiments were conducted on aluminum plates with a thickness of 3 mm and defects with different diameters and depths.The parameters of the segment window are discussed in detail.The results indicate that the proposed method had an amplitude four times larger than of conventional ultrasonic guided waves inspection method for pinhole defect detection and could detect micro-sized pinhole defects as small as 0.5 mm in diameter and 0.5 mm in depth.Moreover,the segment window location and width(5-10 times width of the conventional excitation signal)did not affect the detection sensitivity.The combination of low-power and STR is more conducive to detection in different environments,indicating the robustness of the proposed method.Compared with conventional ultrasonic guided wave inspection methods,the proposed method can detect much smaller defect echoes usually obscured by noise that are difficult to detect with a lower excitation power and thus this study would be a good reference for pinhole defect detection.

High-order sliding mode attitude controller design for reentry flight

A novel high-order sliding mode control strategy is proposed for the attitude control problem of reentry vehicles in the presence of parametric uncertainties and external disturbances, which results in the robust and accurate tracking of the aerodynamic angle commands with the finite time convergence. The proposed control strategy is developed on the basis of integral sliding mode philosophy, which combines conventional sliding mode control and a linear quadratic regulator over a finite time interval with a free-final-state and allows the finite-time establishment of a high-order sliding mode. Firstly, a second-order sliding mode attitude controller is designed in the proposed high-order siding mode control framework. Then, to address the control chattering problem, a virtual control is introduced in the control design and hence a third-order sliding mode attitude controller is developed, leading to the chattering reduction as well as the control accuracy improvement. Finally, simulation examples are given to illustrate the effectiveness of the theoretical results.

A Self-Consistent Model on Cylindrical Monopole Plasma Antenna Excited by Surface Wave Based on the Maxwell-Boltzmann Equation

The paper analyzes the motion of electron in plasma antenna and the distribution of electromagnetic field power around the plasma antenna, and proposes a self-consistent model according to the structure of cylindrical monopole plasma antenna excited by surface wave;calculation of the model is based on Maxwell-Boltzmann equation and gas molecular dynamics theory. The calculation results show that this method can reflect the relationships between the external excitation power, gas pressure, discharge current and the characteristic of plasma. It is an accurate method to predicate and calculate the parameters of plasma antenna.

Effects of Magnetic Shear on the Resistive Wall Mode Instability in a Cylindrical Model

The linear evolution of a resistive wall mode(RWM)with magnetic shears was analytically studied in a cylindrical geometry.The incompressible magnetohydrodynamic(MHD)equations were solved by the Fourier analysis method,and various equilibrium magnetic fields were considered.The shear in the magnetic field had an unstable effect on the linear evolution of the RWM.The linear growth rate increased obviously with increase of the magnetic shear rate for higher magnetic shears.Slow plasma rotation could stabilize the RWM with low magnetic shears,but the plasma rotation could not stabilize the RWM with high magnetic shears.The stabilizing effects of the wall conductivity on the RWM are more efficient for lager magnetic shear.

Fast self-adapting high-order sliding mode control for a class of uncertain nonlinear systems

A fast self-adapting high-order sliding mode(FSHOSM)controller is designed for a class of nonlinear systems with unknown uncertainties.As for uncertainty-free nonlinear system,a new switching condition is introduced into the standard geometric homogeneity.Different from the existing geometric homogeneity method,both state variables and their derivatives are considered to bring a reasonable effective switching condition.As a result,a faster convergence rate of state variables is achieved.Furthermore,based on the integral sliding mode(ISM)and above geometric homogeneity,a self-adapting high-order sliding mode(HOSM)control law is proposed for a class of nonlinear systems with uncertainties.The resulting controller allows the closed-loop system to conduct with the expected properties of strong robustness and fast convergence.Stable analysis of the nonlinear system is also proved based on the Lyapunov approach.The effectiveness of the resulting controller is verified by several simulation results.

Decay Mode Solutions to (2 + 1)-Dimensional Burgers Equation, Cylindrical Burgers Equation and Spherical Burgers Equation

Three (2 + 1)-dimensional equations—Burgers equation, cylindrical Burgers equation and spherical Burgers equation, have been reduced to the classical Burgers equation by different transformation of variables respectively. The decay mode solutions of the Burgers equation have been obtained by using the extended -expansion method, substituting the solutions obtained into the corresponding transformation of variables, the decay mode solutions of the three (2 + 1)-dimensional equations have been obtained successfully.

SCATTERING FAR FIELD SOLUTION OF SH-WAVE BY MOVABLE RIGID CYLINDRICAL INTERFACE INCLUSION

The Green's function is used to solve the scattering far fieldsolution of SH-wave by a mov- able rigid cylindrical interfaceinclusion in a linear elastic body. First, a suitable Green'sfunction is devel- oped, which is the fundamental displacementsolution of an elastic half space with a movable rigid half-cylin-drical inclusion impacted by out-of-plane harmonic line source loadedat any point of its horizontal surface.

FORMULATION AND EVALUATION OF AN ANALYTICAL STUDY FOR CYLINDRICAL HELICAL SPRINGS

The free vibration analysis of cylindrical helical springs is carried out by means of an analytical study. In the governing equations of the motion of the springs, all displacement functions are defined at the centroid axis and also the effects of the rotational inertia, axial and shear deformations are included in the proposed model. Explicit analytical expressions which give the vibrating mode shapes are derived by rigorous application of the symbolic computing package MATHEMATICA and a process of searching is used to determine the exact natural frequencies. Numerical examples are provided for fixed-fixed boundary conditions. The free vibrational pa- rameters are chosen as the number of coils （n = 4- 14）, the helix pitch angle （a = 5 - 30°） and as the ratio of the diameters of the cylinder and the wire （D/d = 4 - 18） in a wide range. Validation of the proposed model has been achieved through comparison with a finite element model using two-node standard beam elements and the results available in published literature, which in these cases indicates a very good correlation.

Natural dynamic characteristics of a circular cylindrical Timoshenko tube made of three-directional functionally graded material

The natural dynamic characteristics of a circular cylindrical tube made of three-directional(3 D)functional graded material(FGM)based on the Timoshenko beam theory are investigated.Hamilton’s principle is utilized to derive the novel motion equations of the tube,considering the interactions among the longitudinal,transverse,and rotation deformations.By dint of the differential quadrature method(DQM),the governing equations are discretized to conduct the analysis of natural dynamic characteristics.The Ritz method,in conjunction with the finite element method(FEM),is introduced to verify the present results.It is found that the asymmetric modes in the tube are controlled by the 3 D FGM,which exhibit more complicated shapes compared with the unidirectional(1 D)and bi-directional(2 D)FGM cases.Numerical examples illustrate the effects of the axial,radial,and circumferential FGM indexes as well as the supported edges on the natural dynamic characteristics in detail.It is notable that the obtained results are beneficial for accurate design of smart structures composed from multi-directional FGM.

THE FREE BENDING VIBRATION OF CYLINDRICAL TANK PARTIALLY FILLED WITH-LIQUID AND SUBMERGED IN WATER

This paper studies the free bending vibration of cylindrical tank partially filled with liquid and submerged in water. The depths of liquid and water may be completely arbitrary. The exact calculating formulae of mode shape functions and inherent frequencies are deduced. The results can be gained by means of computer. The analysis shows that the effect of liquid and water on vibration of cylindrical tank is respectively equivalent to a generalized distributive mass attached to the tank.

Study of hysteresis behavior in reactive sputtering of cylindrical magnetron plasma

In order to make sufficient use of reactive cylindrical magnetron plasma for depositing compound thin films, it is necessary to characterize the hysteresis behavior of the discharge. Cylindrical magnetron plasmas with different targets namely titanium and aluminium are studied in an argon/oxygen and an argon/nitrogen gas environment respectively. The aluminium and titanium emission lines are observed at different flows of reactive gases. The emission intensity is found to decrease with the increase of the reactive gas flow rate. The hysteresis behavior of reactive cylindrical magnetron plasma is studied by determining the variation of discharge voltage with increasing and then reducing the flow rate of reactive gas,while keeping the discharge current constant at 100 m A. Distinct hysteresis is found to be formed for the aluminium target and reactive gas oxygen. For aluminium/nitrogen, titanium/oxygen and titanium/nitrogen, there is also an indication of the formation of hysteresis; however, the characteristics of variation from metallic to reactive mode are different in different cases. The hysteresis behaviors are different for aluminium and titanium targets with the oxygen and nitrogen reactive gases, signifying the difference in reactivity between them. The effects of the argon flow rate and magnetic field on the hysteresis are studied and explained.

NONLINEAR STABILITY ANALYSIS OF A SANDWICH SHALLOW CYLINDRICAL PANEL WITH ORTHOTROPIC SURFACES

In this paper, the large deflection theory is adopted to analyse the geometrical nonlinear stability of a sandwich shallow cylindrical panel with orthoiropic surfaces. The critical point is determined and the postbitckling behaviour of the panel is studied.

Vibration Spectrums of Polar Interface Optical Phonons in GaAs／AlAs Cylindrical Quantum Dots

The dispersions of the top interface optical phonons and the side interface optical phonons in cylindrical quantum dots are solved by using the dielectric continuum model. Our calculation mainly focuses on the frequency dependence of the IO phonon modes on the wave-vector and quantum number in the cylindrical quantum dot system.Results reveal that the frequency of top interface optical phonon sensitively depends on the discrete wave-vector in z direction and the azimuthal quantum number, while that of the side interface optical phonon mode depends on the radial and azimuthal quantum numbers. These features are obviously different from those in quantum well, quantum well wire,and spherical quantum dot systems. The limited frequencies of interface optical modes for the large wave-vector or quantum number approach two certain constant values, and the math and physical reasons for this feature have been explained reasonably.

Study on applicability of modal analysis of thin finite length cylindrical shells using wave propagation approach

Donnell’s thin shell theory and basic equations based on the wave propagation method discussed in detail here, is used to investigate the natural frequencies of thin finite length circular cylindrical shells under various boundary conditions. Mode shapes are drawn to explain the circumferential mode number n and axial mode number m, and the natural frequencies are cal-culated numerically and compared with those of FEM (finite element method) to confirm the reliability of the analytical solution. The effects of relevant parameters on natural frequencies are discussed thoroughly. It is shown that for long thin shells the method is simple, accurate and effective.

柱状药包侧向爆破下抵抗线对岩石破碎特性的影响研究

为研究抵抗线对柱状药包侧向爆破下岩石破碎特性的影响,采用波动理论,分析了自由面处的应力状态;采用直铜丝电爆炸模拟柱状药包爆破,开展了侧向爆破破岩的物理模型试验;再借助超高速摄像技术,观测了试件表面裂纹网的演化过程;结合爆破漏斗区形态、尺寸和碎块分布特征,研究了不同抵抗线下柱状药包爆破破岩特性。结果表明,抵抗线是控制岩石爆破破裂模式、破坏区形态和碎块块度大小的重要因素。随抵抗线增加,裂纹发育速度与密度减小,裂纹网覆盖范围增加,优先贯穿裂纹由横向转变为环向裂纹。此外,模型试验结果表明,破裂区短轴随抵抗线增加而增加。结合自由面处应力状态,利用最大拉应变准则对此进行了解释。建立了碎块块度与能量单耗之间的关系,研究成果为岩石工程爆破设计优化提供参考。

圆形流管内高阶混合模态激发的全局标定方法

声模态发生器是通过调控扬声器阵列,进而在管道内激发特定阶次声模态的一种装置,可用于流管内气动噪声传播和环形声衬的降噪研究。使用多圈布置的扬声器阵列模态发生器,通过调节各个声源的幅值和相位,可实现高阶周向、径向和混合模态的激发。然而,扬声器阵列系统的通道输出偏差会在目标模态激发时产生显著的干扰模态。为消除扬声器系统通道输出差异对模态激发的影响,提出了基于最小二乘全局标定的流管内高阶混合模态激发方法。通过对扬声器声源的通道输出偏差进行全局建模,引入激励补偿因子和流场校正因子,将有流情况下各扬声器的系统输出偏差求解问题转换为无流情况下单个扬声器工作时的模态识别问题,通过矩阵变换和最小二乘法求解各扬声器的激励补偿因子,最终实现扬声器的幅值和相位激励修正。将所发展的模态激发与全局标定方法应用于所研制的圆形流管模态激发装置,结果表明:干扰模态的强度被显著抑制,且在工作频率范围内,目标激发模态的相对目标模态系数不低于10 dB。

圆柱壳体动力响应中的模态参与问题研究

以两端简支圆柱壳体为例,研究了考虑正、余弦模态成分影响的圆柱壳体动力响应中的模态参与问题,提出了根据模态参与因子的分布特征判定模态截断阶次的方法,采用正、余弦模态叠加得到了圆柱壳体在冲击激励及旋转行波激励作用下的动力响应,基于响应的收敛性验证了判定方法的可靠性。理论计算与有限元仿真结果表明,与圆柱壳体模态特性分析不同,在求解圆柱壳体动力响应时必须同时考虑正、余弦模态成分的影响;冲击激励作用下,圆柱壳体各阶正、余弦模态在响应中的参与程度与激振点和观测点的位置相关;旋转行波激励作用下,圆柱壳体各阶正、余弦模态在响应中的参与程度与激励的阶次和频率密切相关。