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2024 | Book

Advances in Applied Nonlinear Dynamics, Vibration, and Control – 2023

The Proceedings of 2023 International Conference on Applied Nonlinear Dynamics, Vibration, and Control (ICANDVC2023)

Editors: Xingjian Jing, Hu Ding, Jinchen Ji, Daniil Yurchenko

Publisher: Springer Nature Singapore

Book Series : Lecture Notes in Electrical Engineering


About this book

This book provides readers with up-to-date advances in applied and interdisciplinary engineering science and technologies related to nonlinear dynamics, vibration, control, robotics, and their engineering applications, developed in the most recent years. All the contributed chapters come from active scholars in the area, which cover advanced theory and methods, innovative technologies, benchmark experimental validations and engineering practices. Readers would benefit from this state-of-the-art collection of applied nonlinear dynamics, in-depth vibration engineering theory, cutting-edge control methods and technologies and definitely find stimulating ideas for their on-going R&D work. This book is intended for graduate students, research staff, and scholars in academics and also provides useful hand-up guidance for professionals and engineers in practical engineering missions.

Table of Contents

Study on the Dynamic Performance of X-shaped Vibration Isolator with Friction Damping Based on Incremental Harmonic Balance Method

In order to improve the vibration isolating performance of the existing X-shaped vibration isolator, a novel X-shaped vibration isolator is constructed by adding plate-type friction damping element which does not decrease the overall stiffness of the isolating system. First of all, the geometrical relationships of the X-shaped isolator with friction damping are presented, then the mathematical model of the isolating system is established. Furthermore, to validate effectiveness of the proposed dynamic model, the incremental harmonic balance method is utilized to derive steady-state solutions of the isolating system under base excitation, and the accuracy of the theoretical solutions is verified through numerical simulation method. At last, the vibration suppression performance of the isolating systems with and without the plate-type friction damping element are evaluated in terms of displacement transmissibility. The calculation results reveal that the developed X-shaped vibration isolator with plate-type friction damping has a better vibration reduction performance near the resonance frequency.

Zhongren Yang, Haiping Liu, Hongbo Li, Tian Wang
Vibrations Induced by Rubbing Between Labyrinth and Rubber-Coating for Rotating Engine in Experiment

Rotor-stator rubbing is common in rotating engines, and the induced vibrational characteristics of the rotor and stator are affected by the rubbing materials. The soft coating made by vulcanized rubber is considered for rubbing case, followed by the experimental investigations on the kind of progressive rubbing between the seal-labyrinth and the seal-case of a rotor. The vibrational waveforms and the spectral features of the rotor and stator, together with the shaft orbits during the rubbing process are analyzed. The center of the rotor is forced to shift from the balance point of zero displacement, in the meanwhile, the vibrational acceleration of the stator is increased radically and finally nonlinear instability is excited during the rubbing. The shaft orbit varies from stable to unstable, and recovers to be stable eventually. Rotor-stator coupling resonance is captured both in the rotor and stator vibrational signals. High-order super-harmonics (corresponding to the resonance of the rotor and stator), the modulations of the fundamental rotating frequency are excited by the soft rubbing.

Ruixian Ma, Yaqing Wei, Quankun Li, Rui Wang, Mingfu Liao, Kaiming Wang, Pin Lv
Semi-analytical Expression of Force and Stiffness of Perpendicular Polarized Ring Magnets for Nonlinear Dynamic Analysis

Magnetic coupling arrays composed of ring permanent magnets have been widely applied in industrial occasions for achieving nonlinearity, such as passive magnetic bearings, quasi-zero stiffness isolators and multi-stable energy harvesters. These magnetic couplings can be divided into basic configurations including axial magnetization, radial magnetization, and perpendicular magnetization. For the purpose of structure design and parameter optimization, the semi-analytical expressions of first two configurations have been analyzed to obtain high accuracy and low computational cost in previous literatures, while the semi-analytical calculation of perpendicular magnetization has not still been investigated. Therefore, the semi-analytical expressions of magnetic force and stiffness for perpendicular polarized ring magnets are proposed. Then, the magnetic forces calculated by the proposed method, numerical simulation, and COMSOL software under different parameters are obtained. The results show that the proposed semi-analytical calculation has higher accuracy and less computational time than numerical simulation. Moreover, the influence of structural parameters on magnetic stiffness is analyzed. It can be demonstrated that with the increase of air gap, the decrease of the width of axial magnetized magnet, and the decrease of the height of axial magnetized magnet, the magnetic force and magnetic stiffness are both reduced. In general, the proposed semi-expression model can be applied for the design and optimization in the practical applications of ring permanent magnets.

Ying Zhang, Wei Wang, Junyi Cao
On-Orbit Reconfiguration Dynamics and Control of Heterogeneous Intelligent Spacecraft

An ultra-large space structure constructed by modular intelligent spacecraft can meet the mission requirements of variable environment and multiple working conditions through reconfiguration. This paper focuses on the dynamics and control problems in the on-obit reconfiguration of heterogeneous intelligent spacecraft, which consists of 125 rigid spacecraft modules and 2 flexible spacecraft modules. The relative position motion of the spacecraft is described by the Clohessy-Wiltshire (C-W) equations, and the attitude dynamics is expressed on SO(3). The reconfiguration mission is decomposed into three distinct phases: separation, unit reconfiguration and reassembly, where the unit reconfiguration phase is further divided into three steps: separation, pre-assembly and docking. The reassembly phase can also be divided into two steps: pre-assembly and docking. To ensure the safety of the reconfiguration mission, a compound controller which combines a collision avoidance controller and a PD controller is designed for the pre-assembly steps, while only PD control is used for the docking steps. Some numerical results are shown to verify the effectiveness of the proposed controller.

Dengliang Liao, Xingyi Pan, Xilin Zhong, Zhengtao Wei, Ti Chen
Study on the Effect of Angular Misalignment on the Contact Load and Stiffness of Cylindrical Roller Bearings

Cylindrical Roller Bearings (CRB) find extensive application in rotating machinery. However, the issue of bearing angular misalignment has received limited research attention. Therefore, a four-degree-of-freedom quasi-static model of CRB is introduced, specifically considering angular misalignment in two directions. The model enables an investigation into the impact of angular misalignment on load distribution, contact moment, and bearing stiffness. The obtained results reveal that angular misalignment in two radial directions only marginally affects load distribution but significantly influences the contact moment. Furthermore, it is observed that misalignment angles in different directions have varying effects on rollers positioned at distinct azimuths. Moreover, the influence of angular misalignment on angular stiffness is considerably more substantial than its impact on radial stiffness. These findings carry significant implications for addressing misalignment concerns in CRB.

Zihang Li, Xilong Hu, Choangyang Wang, Haoze Wang, Lihua Yang
Dynamic Modeling and Features of GTF Engine Rotor System

To consider the problem that coupling, support position, bearing form and connection mode of the rotor system caused by adding a gear system between the fan and the compressor in the Geared Turbo Fan (GTF) engine, dynamic modeling and features of the GTF engine rotor system are studied in this paper. For the modelling, a star gear meshing model including herringbone teeth and five-way shunt is designed for star gear train; the inner gear ring connected to the fan rotor and the sun gear connected to the low-pressure turbine rotor are meshed through the gear meshing unit, and then the rotor dynamic model including disk, shaft, support structure and membrane disk coupling is established by finite element method. After that, some dynamic features like modal properties and unbalanced responses are analyzed through the proposed dynamic model of the GTF engine rotor system. The combined model of low-pressure unit and star gear unit is established, which can provide an efficient method for the dynamic analysis and design of GTF engine.

Heyu Hu, Bin Shi, Tianxiang Wang, Quankun Li, Mingfu Liao, Kang Zhang, Fali Yang
Nonlinear Dynamic Analysis of Rub-Impact Rod-Fastening Combined Rotor Systems with Internal Damping

The objective of this study is to examine the nonlinear dynamic behavior of the rod-fastening combined rotor-bearing (RFCR) system with rub-impact, with a specific focus on the influence of internal damping. A dynamic model for the RFCR system is formulated using the finite element method based on the Lagrange equation. This model takes into account the system’s nonlinear characteristics, including rub-impact forces and oil-film forces. Through the analysis of bifurcation diagrams, Poincaré maps, time-domain plots, and frequency spectra, the effects of internal damping and stator stiffness on the system’s instability and nonlinear response are investigated. The findings reveal that both internal damping and stator stiffness have a significant impact on the vibration and instability of the RFCR system at varying speeds. Particularly, systems with rubbing faults exhibit pronounced nonlinearity and instability in high-speed regions. Furthermore, the presence of internal damping disrupts the stability of the P3 motion in the system, and the effect of divergence becomes more pronounced as the friction coefficient increases. In conclusion, considering internal damping is crucial when undertaking dynamic modeling and analysis of such complex rotors, as it plays a vital role in fault diagnosis and vibration control for practical RFCR systems.

Chongyang Wang, Zihang Li, Haoze Wang, Xilong Hu, Lihua Yang
A Multiscale Fracture Model to Reveal the Toughening Mechanism in the Bioinspired Bouligand Structure

The Bouligand structure has been observed in a variety of biological materials, such as lamellar bone and arthropod cuticles. It is a hierarchical architecture that exhibits excellent damage-resistant performance, which arouse many interests for the mechanists and structure engineers. However, there still lacks a deep understanding of the toughening mechanisms in the Bouligand structure. For the purpose of revealing the toughening effect of twisting cracks, this paper developed a multiscale fracture mechanics model with considering the non-homogeneity and anisotropic properties. Firstly, the macro and micro constitutive properties of the Bouligand structure are analyzed. Then, a multiscale fracture model is established to characterize the energy release rates and the local stress intensity factors at the crack front of twisting cracks which are formed within the Bouligand structure. Based on the model, serious of digital calculations are carried out. The digital results demonstrate that the decrease of the local energy release rate can be attributed to two mechanisms. One is that the multiscale structure causes the stress release of the crack tip nearby. The other is that the twisting crack leads to the loading mode transformation from the single-mode to the mixed-mode, which is the main reason of the fracture toughness increasing. The research results shown in this paper can provide structure engineers some suggestive guidelines for the design of high-performance composites.

Yunqing Nie, Dongxu Li, Luojing Zhou
Decoupled Multi-mode Controllable Electrically Interconnected Suspension for Improved Vehicle Damping Performance

This paper proposes a new multi-mode controllable electrically interconnected suspension (EIS) system to further improve the driving smoothness and stability of passive suspension vehicles. The multi-mode controllable EIS utilizes the bi-directional conversion of mechanical and electrical energy of the electromagnetic damper and adds an active energy dissipation control circuit module to the semi-active EIS, which can realize active and semi-active multi-mode switching control of the EIS. Due to the decoupling characteristics of interconnected suspension, the switch in the designed active control circuit can achieve the effect of active segment decoupling control in conjunction with the adjustable resistor in the semi-active electrical network, which will greatly reduce the control difficulty of the EIS system. To deeply study the performance of each part of the multi-mode controllable EIS, the dynamics model, multi-mode controllable circuit model, and state equation of the semi-vehicle EIS are established. The target force required to improve the performance of the suspension is solved by an H∞ state feedback controller, and the control logic is designed for the coordination relationship between the bridge switch and the adjustable resistor module of the multi-mode controllable EIS so that the force generated by the EIS can better track the target force and achieve the purpose of semi-vehicle vibration control. The acceleration, body attitude, and power consumption information of the semi-active EIS only, active EIS only, and multi-mode controllable EIS are compared and analyzed by numerical simulation.

Pengfei Liu, Donghong Ning, Guijie liu, Haiping Du
Adaptive Robust Sliding-Mode Control of a Semi-active Seat Suspension Featuring a Variable Inertance-Variable Damping Device

This article introduces a novel mechanical variable inertance-variable damping (VIVD) seat suspension based on an adaptive robust sliding-mode (ARSM) controller, including its characteristics validation and performance experiment. In this paper, a variable damping (VD) device and a flywheel are connected in series to form a variable inertance (VI) device with real-time controllable inertance, which is connected in parallel with another VD device to form a VIVD device. A two-layer control scheme is proposed where an upper desired controller is designed based on adaptive robust sliding-mode control and the desired control force is calculated; then a force tracking control strategy with energy priority storage (EPS) is designed as the lower layer controller. Under road random excitation, the VIVD seat suspension exhibits 21.89% and 9.56% lower RMS acceleration values compared to the passive seat suspension and a semi-active traditional sliding-mode control seat suspension. The new system demonstrates advantages in controllability and energy efficiency, with energy consumption falling within the milliwatt range. The proposed semi-active VIVD device shows potential in vehicle vibration control.

Guangrui Luan, Pengfei Liu, Donghong Ning, Guijie Liu
An Adaptive Controller for Payload Swing Suppression of Ship-Mounted Boom Cranes

The ship-mounted crane is a typical system for completing marine projects, which often need to work in complex sea conditions. Besides, it has complex nonlinearity and is also a typical underdrive system. These factors increase the difficulty of the controller design. Traditional control strategies based on gravity compensation are mostly used in full-drive systems, which can effectively reduce the influence of gravity uncertainty on the system positioning error and save driving energy. However, the actuator oscillation problem of underdrive systems, such as the swing of the payload of ship-mounted crane systems, has not been fully solved. This paper proposes an adaptive swing suppression controller based on the gravity compensation of a (3-DOF) ship-mounted boom crane. Specifically, the influence of gravity on system stability is reduced by estimating unknow gravity parameters through adaptive functions. Combine the swing angle information of the payload with the control output to eliminate the remaining swing of the payload. The auxiliary term in the controller reduces the difficulty of subsequent stability analysis, and also has a certain resistance effect to steady-state oscillation. Next, with the help of the Lyapunov stability theory and LaSalle’s invariance theorem, the proof of the asymptotic stability of the closed-loop system is completed. Finally, this paper verifies the effectiveness of the proposed control method successively through numerical simulations, and the simulation data has the potential to improve the robustness of the proposed controller in different marine environments.

Bincheng Li, Peng Liao, Menghua Zhang, Donghong Ning, Guijie Liu
Study on Dynamic Modeling and Vibration Noise Suppression Method of AUV

This paper focuses on the key technical problems of the autonomous underwater vehicle (AUV) vibration and noise reduction. The dynamic model of AUV with propeller-shaft-motor by the second Lagrange method is established. The nonlinear bearing and other connecting parts are fully considered, which is solved by Runge-Kutta method, the dynamic behavior mechanism of AUV is revealed. Taking the vibration amplitude of the shell as the cost function and according to the amplitude-frequency response characteristics of the system, the resonance changer (RC) device by parameter design is designed. The results show that the resonance response amplitude can be greatly reduced. The theoretical model of this paper reveals the dynamic response characteristics of AUV. The results can provide new improvement ideas for the optimization design of vibration and noise reduction of AUV, and have theoretical guiding significance.

Kangyu Zhang, Chao Fu, Kuan Lu, Kaifu Zhang, Hui Cheng, Dong Guo
Simultaneous Vibration Absorbing and Energy Harvesting Mechanism of the Tri-Magnet Bistable Levitation Structure: Modeling and Simulation

This paper investigates efficient simultaneous vibration absorbing and energy harvesting utilizing a bistable electromagnetic vibration absorber (BEVA). The vibration absorber employs a tri-magnet levitation structure, where the magnetic mechanism between the cylindrical and ring magnets achieves the symmetric bistable characteristic. Furthermore, it is attached to the free end of a cantilever beam subject to transient external excitation. The equivalent model of the cantilever beam with the BEVA system is obtained by exploiting the extended Hamilton’ s principle, while the magnetic forces are derived based on the equivalent magnetic charge method. The dry friction of the BEVA and the mechanical damping of the cantilever beam are obtained by parametric identification of the experimental data for accurate numerical simulations. From the vibration attenuation and energy dissipation viewpoints, the performance of the absorber under transient excitation is assessed. It is observed that inter-well oscillations occur at certain excitation levels, while the energy dissipation efficiency of the BEVA is improved substantially compared to the intra-well oscillations.

Junjie Xu, Yonggang Leng
Design and Research of Triboelectric Energy Harvester for Low Frequency Nonlinear Vibration

Although great progress has been made in the study of triboelectric energy harvesting, most of the efforts are aimed at the manufacturing and experimental demonstration of the harvesters. For simultaneous energy harvesting and vibration control, there is still a strong need of structural design and in-depth theoretical research of structural dynamics of triboelectric harvesters.In this paper, a harvester in the form of a cantilever beam and two curved surfaces as constraints is proposed. When the cantilever beam vibrates under a low-frequency excitation, the contact between the cantilever beam and one of the curved surfaces is gentle and gradual. Compared with a triboelectric harvester working in the traditional contact-separation mode, this contact can achieve energy harvesting while avoiding the introduction of vibro-impact of the structure, but introduces complex nonlinear vibration. Through the planar rigid body kinematics and a quasi-static analysis, the differential equation of motion for the cantilever beam including the ninth-order geometric nonlinearity for the contact is established. The mathematical model for combining the structural dynamics and electrical dynamics is established. Finally, the approximate analytical solution of the model is obtained by using the harmonic balance method, and the stability of the model under different structural parameters is analyzed by Floquet theory.Numerical simulation results show that when the frequency excitation is 5.72 Hz, the peak output voltage is 6.9 V and the average power is 1.9 μW. When the frequency is between 5.72 Hz and 5.93 Hz, the response exhibits bifurcation. Compared with the traditional cantilever beam absorber, the frequency response curve of this structure is deflected due to the nonlinear factors brought about by the curved surface, and the frequency band of vibration hysteresis is narrow. The broadband capacity of the nonlinear spring is proven in the frequency domain for two chosen surface curvature orders, with one low and one high amplitude of excitation. Therefore, the structure proposed in this paper can maintain a larger amplitude in the broadband, thus playing a role in broadening the working frequency band of vibration absorption. In summary, the structure can not only realize vibration energy harvesting without hard impact, but also work as a vibration absorber with nonlinear characteristics.

Yinqiang Huang, Huajiang Ouyang, Zihao Liu
Energy Harvesting Study of Piezoelectric Vibration Harvester with Double Parallel Slender Structure

In this paper, we use a cantilevered double parallel slender structure single deformation piezoelectric energy harvester as a model and combine it with the Lamb-Oseen vortex model, where the effect from fluid vortices is used as an external load, and a metal sheet is attached to the free end of the energy harvester for capturing the shear force generated by wind-generated vortices on the double beams model. The closed-form solution of the bending forced vibration of the piezoelectric energy harvester is solved by establishing the relevant model and deriving the equations. Euler- Bernoulli beam assumptions are used to develop a coupled electromechanical model for the harvester with an intermediate spring layer and a transverse damping is considered, and Green's functions and Laplace transform techniques are used to solve the vibration equations for the coupled piezoelectric vibration system. By solving for the voltage as a function of Green's functions and using Matlab software, we can obtain the functional relationship between the voltage of the harvester and the elastic coefficient of the interlayer and the position of the metal plate setting.

Xiang Zhao, Haotian Jiang
A Broadband Energy Harvester with Three-to-One Internal Resonance

In this study, we present a novel two-degree-of-freedom (TDOF) nonlinear energy harvester with internal resonance. To show the performance, a TDOF nonlinear electromagnetic harvester is designed and the mathematical model is derived. The electromechanical coupling system is solved by adopting the harmonic balance method, and the first-order harmonic solutions of the system are provided. The displacement and current frequency response curves are created along with the modulation equations. The advantage of the proposed harvester is that compared to the conventional single-degree-of-freedom (SDOF) nonlinear model and the corresponding TDOF linear system, the results achieve that the proposed scheme can enhance the bandwidth of the harvesting energy. The influences of different excitation amplitudes $${f_1}$$ f 1 and $${f_2}$$ f 2 on the response are discussed. The accuracy of the analytical first-order harmonic results is demonstrated by numerical simulations, and the existence of multiple periodic solutions for time history at the same external force frequencies is quantitatively proved.

Le Yang, Wenan Jiang, Xingjian Jing, Liqun Chen
Optimization Design of High-Pressure Simulated Rotor

Combined elastic support which include squirrel cage and squeeze film damper (SFD) are widely used in aero-engines, gas turbine, and steam turbine. Squirrel cage can vary the critical speed and strain energy distribution of the rotor system by changing the stiffness. SFD can effectively suppress rotor vibration and reduce transmitted forces. Given the inherently nonlinear behavior of SFD, a poorly designed damper has the potential to exacerbate rotor vibrations, posing a significant safety risk to engine operation. The influence of axial width of the SFD on dynamics behavior of the rotor-SFD system, such as critical speed, mode shape, vibration response has been developed in this paper. The Newton method was employed to optimize the critical speed and vibration response. The results of optimization reduced the 2nd critical speed by 24%, reduced the vibration amplitude of acceleration by 92%, and reduced the vibration amplitude of displacement by 88.3%. The contents and methods of this paper can provide guidance for the vibration optimization of rotor-squeeze film damper system.

Zhongyu Yang, Jiali Chen, Yinli Feng
Energy Transfer of Particle Impact Damper Systems

In this work, investigations on energy transfers from a linear oscillator (called primary structure) forced by a shock to a strongly nonlinear attachment, namely a particle impact damper (PID) are carried out. The granules inside the cavity of the PID are arranged in initial topology with clearances. The granular interactions are realistically modeled by combining a Hertzian dissipative contact model and a Coulomb-tanh friction model, which is useful to accurately explore the strong and highly discontinuous nonlinear characteristics of this system subject to shocks of varying intensities. The discrete element method is employed for these simulations, considering granular translations and rotations. Generally, by optimizing the size of the cavity one can improve the shock mitigation performance. The capacity of energy transfer and energy dissipation in the granular medium is enhanced and maintained by a collect-and-collide regime. Intense nonlinear contacts via granule-to-granule and granule-to-wall interactions result in intense and irreversible energy transfer of shock energy from the directly forced primary structure to the PID. Once this energy is transferred, it gets efficiently scattered to high frequencies and dissipated by the inelastic granular collisions and frictional effects due to relative granular rotations. The energy transfer reported herein provides strong motivation for developing the next generation of PID technology.

Xiang Li, Li-Qun Chen, Lawrence A. Bergman, Alexander F. Vakakis
An Empirical Control Research on the Lexical Approach to Business Correspondence Writing in Vocational Colleges

With the trend of economic globalization, business correspondence plays an increasingly important role in transmitting information, dealing with business activities and better cooperation. However, the current business correspondence teaching approach hasn’t come to a better effect to meet the above requirements. With the development of philosophy, psychology and corpus linguistics, more and more linguists have been aware of the limitation of the traditional approach. Lewis (1997) conducted a series of studies on lexical chunks and considered language is composed of chunks producing continuous coherent texts when they are combined. Chinese scholars have done some research on the appliance of lexical chunks, but how to implement this approach to business correspondence writing for vocational college students, is still at the margins. Accordingly, based on the lexical approach proposed by Lewis, this paper combines characteristics of languages used to compose business correspondence with the current learning status of vocational college students and processes the analyses of significant differences and the relationship between kinds of lexical chunks and the writing competence of vocational college students with the assistant of SPSS. The results indicate that lexical approach could effectively enhance students’ of business correspondence writing competence.

Jin Zhang
Analytical Analysis of Nonlinear Vortex-Induced Vibration of Pipes Conveying Fluid

In this paper, the vortex-induced vibrations of a long flexible pipe conveying steady fluid are investigated via a two-mode discretization of the governing differential equations. The governing nonlinear partial differential equations (PDEs) are transformed into ordinary differential equations (ODEs) by applying the Galerkin’s method, which are then studied numerically for the pipe with primary resonances during lock-in for each of the first two modes. The method of multiple scales is utilized to obtain the steady-state responses of the coupled equations. It is found that the frequency-amplitude relationships present typical nonlinear phenomena, including jumping and multi-value. Numerical integrations are directly implemented in the vibration equations to verify the aforementioned analytical results. Furthermore, an analytical expression that predicts the lock-in phenomenon range of external fluid velocity is derived. The influences of the velocity of internal and external fluids on the dynamical characteristics are discussed in detail. It is shown that the values of the external fluid velocity triggering the start and stop of the lock-in phenomenon will change with the value of the internal fluid velocity of the pipe.

Jian Liu, Yu Wang
RBF Neural Network for Feature Selection Using Sparsity Method

The simplicity of RBF neural network (RBFNN) mainly depends on the input (feature) and hidden nodes. To compact the structure of RBFNN, in this paper, a weight decay regularizer based integrated feature selection (FS) strategy is proposed to prune the input nodes. The training procedure of our FS method is explainable: firstly using clustering algorithm, the initialization process of RBFNN is detailedly described; then a novel memory based gradient method is used to promote the process of feature selection and parameter optimization; finally, the weight decay terms for FS will tend to different values. Using two regression problems, the validation of our model to realize feature selection and predict the real outputs is proved.

Tao Gao, Jun Yang, Yongyong Xu, Baosheng Qian, Bin Wang, Ruoxi Yu
Periodic Motions and Bifurcations of a Spring-Driven Joint System with Periodic Excitation

Spring-driven joint system is a nonlinear dynamic system that is applied in flexible robot arms. Similar to the forced pendulum system, it has state variable in the sinusoidal function, but are more complicated with driven spring length coupling with the joint angle. With traditional analytical approaches, it is difficult to analyze such a nonlinear system since both the system state and the excitation are correlated with the nonlinear sinusoidal term. In this paper, a spring-driven joint system with periodic excitation will be discussed. The implicit discrete maps approach will be applied to solve the periodic motions for such a joint system, and the stability condition will be discussed. The analytical expressions for periodic motions for such a spring-driven system can be recovered with a series of Fourier functions. The bifurcation diagram for such a system will be given to show the complexity of the motions when the frequency of the excitation varies. From analytical bifurcation for period-1 and period-2 motions, the jump phenomenon and the continuity of periodic motion can be analytically explained.

Yufan Zhou, Zhongliang Jing, Jianzhe Huang, Xiangming Dun, Hailei Wu
Enhanced Vibration Characteristics of Honeycomb Plates Composed of Metamaterials with NTE

Mechanical metamaterials with tailorable negative thermal expansion (NTE) are significant and potential to be applied in stability control, precise instrument, space equipment, etc. This paper established the honeycomb plates which are composed of metamaterial lattices consisting of trapezoid units with NTE. The vibration characteristics of these honeycomb plates were analyzed by Euler beam elements in finite element analysis. The frequency characteristics and harmonic response analysis of these honeycomb plates were investigated under uniform temperature increments. In addition, the effects of geometric parameters on the fundamental frequency and thermal stress were discussed. Finally, the fundamental frequency and thermal stress were compared between the present metamaterials with trapezoid units and the corresponding metamaterials with triangular units. These results indicate that the NTE effect in metamaterials can enhance the fundamental frequency and reduce the deflection dynamic amplification factor of structures under uniformly raised temperatures. The present metamaterials provide a thought for designing and developing heat-resistant structures.

Qiao Zhang, Yuxin Sun
Vibration Reduction of Limited Series Nonlinear Energy Sink

In engineering, vibration is ubiquitous. In order to avoid damage caused by vibration to some devices, passive vibration absorbers are usually used for vibration reduction in engineering. The concept of nonlinear energy sink (NES) has been proposed for a long time. However, most previous studies on NES have typically conducted vibration reduction research by coupling a single-degree-of-freedom (1DOF) NES with a single-degree-of-freedom primary system. This paper proposes a vibration control strategy using a limited amplitude series NES. A dynamic model using a limited series NES was established for the two-degree-of-freedom (2DOF) primary system. The influence trend of the parameters of the limited series NES parameters on the vibration control effect was studied through dynamic analysis. The results show that the amplitude-limiting series NES has a better vibration absorption effect and stability than the ordinary series NES under the same mass of the total vibration absorber. This study provides a new and efficient vibration control strategy.

Ting-Kai Du, Hu Ding
Understanding Neural Rhythmic Mechanisms Through Self-oscillations of Complex Neural Networks and Their Adaptation

This study delves into the self-oscillation properties of complex neural networks to elucidate the intrinsic mechanisms driving biological rhythm generation and adaptation to external periodic signals. We scrutinize the influence of electrical coupling and Spike-Timing-Dependent Plasticity (STDP) on network synchronization. Employing a neural network characterized by scale-free topology, we observe that neurons with higher node degrees necessitate activation by an increased number of fellow neurons. Central neurons emerge as pivotal in facilitating swift excitation propagation. In contrast, low-degree circuits sustain activity during burst intervals, with circuit length inherently dictating the rhythmic period. Notably, despite their inherent complexity and diverse rhythm generation, neural networks can adaptively select a low-degree loop congruent with external input rhythms via Hebbian learning principles. These insights offer profound implications for comprehending the variances in human biological rhythms across different environments and hold significant value for planning extended space expeditions.

Peihua Feng, Luoqi Ye, Xinaer Adilihazi, Zhilong Liu, Ying Wu
Multi-attention Based Multi-scale Temporal Convolution Network for Remaining Useful Life Prediction of Rolling Bearings

Remaining useful life (RUL) prediction is the key to prognostic health management (PHM) of rolling bearings. Multiple sensors are usually used to monitor the comprehensive data of the rolling bearing operation. To the best of our knowledge, most of the existing research work does not consider the effects of different sensors and different features to RUL prediction results, so they cannot accurately understand more comprehensive information about rolling bearings. Therefore, it is necessary to weigh the information of different sensors and assign weights to the features extracted by the neural network. This paper proposes a RUL prediction method of rolling bearings based on multi-attention and multi-scale temporal convolution network (MA-MTCN). Specifically, the channel attention mechanism is used to weigh different sensors and the feature attention mechanism is used to weigh different features which extract by multi-scale temporal convolutional networks. The temporal convolutional networks are used to extract the complete features and time series features between data. Finally, the feasibility of this method is verified by PHM2012 dataset. Experimental results prove that the MA-MTCN method can reduce the error of RUL prediction to less than 5%.

Yiwen Cong
Dynamics Analysis of the Cooperative Dual Marine Lifting Systems Subject to Sea Wave Disturbances

Strong coupling and complex nonlinearities increase the difficult of the dynamic modeling of the cooperative dual marine lifting system (DMLS). Moreover, it is a great challenge for DMLS model analysis while considering complex sea wave disturbances. To solve these issues, this paper establishes an accurate model of the DMLS by Lagrangian method without any simplifications. The dynamic relationship among the dual horizontal mechanism displacement, the dual lifting boom heights and the payload attitudes is analyzed accurately. The dynamic model considers ship rolling, heave and sway motion induced to sea wave disturbances. Finally, the simulation results are verified the effectiveness of the proposed dynamic model.

Gang Li, Xin Ma, Yibin Li
Nonlinear Hierarchical Control for Unmanned Quadrotor Transportation Systems with Saturated Inputs

An unmanned quadrotor presents excellent mobility to fly freely in complex environments, which makes it an ideal choice for aerial transferring tasks. During the transferring process, it is very challenging to eliminate the swing, since there is no direct control on the payload. The quadrotor transportation system presents the great challenge of the cascaded underactuated–underactuated property, which makes it extremely difficult to simultaneously implement accurate quadrotor positioning and efficient payload swing suppression. In this paper, a nonlinear hierarchical control scheme is proposed for a quadrotor transportation system, which takes full advantage of the cascade property of the system and separates the controller design for the inner loop and the outer loop, respectively, to facilitate the design procedure. More specifically, for the outer loop subsystem, based on the proposed energy storage function, a virtual control vector is designed, which introduces a saturation function to make the desired attitude free of any singularities. For the inner loop, a coordinate-free geometric attitude tracking controller is designed on the Lie group to drive the quadrotor to its desired attitude. Based on that, an energy control law is proposed by taking the practical input constraints into account, which achieves both precise quadrotor positioning and efficient payload swing elimination, and so on.

Lincong Han, Menghua Zhang
Predicting the Endless Stop-Band Behaviour of the NS-MRE Isolator

The periodic structure of the MRE isolator could generate special frequency range in which the waves cannot be propagated. This paper proposed a Negative Stiffness Magnetorheological Elastomer (NS-MRE) isolator with acoustic metamaterial characteristics. This particular structure generates an endless stop-band to restrict the transmission of the vibration. Furthermore, the permanent magnet arrays in the periodic structures of the NS-MRE isolator add dynamic negative stiffness to reduce the overall stiffness in the horizontal vibration direction without sacrificing vertical load-bearing stiffness. That can solve contradictory requirements for large load-bearing capacity and excellent vibration isolation performance at low frequencies as the former requires for large stiffness and the later requires for small stiffness. Using the mass-spring model, the generation mechanism of the stop-band was theoretically analysed. This paper deeply analyses the difference between the NS-MRS isolator and MRE isolator, in particular the stop-band of the single-mass periodic structure from the perspectives of finite period and infinite period, and its potential application for attenuating vibration amplitudes.

Qun Wang, Zexin Chen, Jian Yang, Shuaishuai Sun
Human-Mechanical Biomechanical Analysis of a Novel Knee Exoskeleton Robot for Rehabilitation Training

Exoskeleton robots are a new kind of wearable assistive and rehabilitation training equipment, with user adaptability and assistive effectiveness being important performance indicators. To improve the comfort of wearers and the effectiveness of rehabilitation training, this paper designs a knee rehabilitation training exoskeleton robot and analyzes its performance. Firstly, the exoskeleton robot is designed to reduce the lower limb movement load by placing the power source and motors at the wearer’s waist, and transmitting power to the knee through Bowden cables. A three-dimensional model of the exoskeleton robot is established. Secondly, a human-exoskeleton robot biomechanical simulation environment is constructed, including scenarios of the human body alone, the human body wearing a passive exoskeleton, and the human body wearing an active exoskeleton. Biomechanical simulations of the human-exoskeleton interactions are conducted in these three scenarios. The results show that the designed exoskeleton does not significantly impede human movement. When wearing the exoskeleton, the force and torque of the knees during squatting exercises are significantly reduced, and the muscle force and muscle activation of the quadriceps and gluteus maximus are significantly decreased, while the impact on the calf muscles is minimal. This verifies the good user adaptability and assistive effectiveness of the designed exoskeleton.

Mengmeng Yan, Guanbin Gao, Xin Chen, Yashan Xing, Sheng Lu
Adaptive Sliding Mode Control for Active Suspensions of IWMD Electric Vehicles Subject to Time Delay and Cyber Attacks

This paper addresses the control problem for active suspensions of the in-wheel motor driven electric vehicle with consideration of time delay and cyber attacks. The main purpose is to develop an adaptive sliding mode control (SMC) method to improve the suspension performances by handling the issues of time delay and cyber attacks. Firstly, by considering a dynamic vibration absorber to mitigate vibrations, an active suspension model is constructed, in which both the spring dynamic nonlinearity and the damper dynamic segmentation are approximated by the Takagi-Sugeno fuzzy model. Secondly, by introducing an integral-type sliding surface, sufficient conditions are developed to ensure the sliding motion satisfies the asymptotical stability and desired performance requirements despite the occurrence of time delay. Based on the reachability to the sliding surface, a SMC approach is developed such that the closed-loop suspension system can achieve the desired performances of the sliding surface. For a better calculation of the controller gains, the controller design condition is converted to an optimization problem. Finally, various simulation tests are implemented to verify the merits of the proposed adaptive control method.

Wenfeng Li, Jing Zhao, Mengqi Deng, Zhijiang Gao, Pak Kin Wong
Generative Adversary Network Based on Cross-Modal Transformer for CT to MR Images Transformation

Acquiring Magnetic Resonance (MR) images in the current medical imaging tasks is expensive and time-consuming. We need technology to acquire multi-contrast MR images. Nowadays, studying the synthesis of MR images through deep learning algorithms to improve diagnostic efficiency is a hot topic. However, cross-modal translations are very challenging. This paper proposes an efficient and effective generative adversary network based on Cross-Modal Transformer (C-M Transformer) to address the issues of blurred synthetic images and unstable training, in order to achieve the conversion from Computed Tomography (CT) images to MR images. Firstly, the original input CT image is filtered to generate high-frequency detail images, and then the high-frequency detail images and the original images are respectively fed into the U-shaped network structure for feature extraction. After four downsamplings, the features are sent to the C-M Transformer for feature fusion. In C-M Transformer, the detail feature stream is Q, and the original feature stream is K and V. We added a Masked Attention to provide an average feature representation of two streams. The fused feature image is fed to the upsampling portion of the U-shaped structure to generate the MR image. It can be shown through the experimental results that the method outperforms mainstream algorithms in terms of Mean square error (MAE), Peak signal-to-noise ratio (PSNR), and Structural similarity (SSIM). This method generates MR images that show bone marrow signals in the vertebral body more clearly and accurately than other methods. It can clearly show the position of the lumbar vertebral plate and so on. The results of this method can be used to assist in orthopedic diagnosis after approval by the physician.

Zhenzhen Wu, Weijie Huang, Xingong Cheng, Hui Wang
A Novel Robust Finite-Time Control for Active Suspension Systems with Naturally Bounded Inputs

This paper focuses on a novel robust finite-time control for active suspension systems with external disturbance where the control inputs are naturally bounded by a prior known range to avoid input saturation. To achieve finite-time stability, a novel nonsingular terminal sliding mode variable with an integral term is designed. More importantly, the control inputs are naturally bounded all the time due to the characteristics of hyperbolic tangent functions such that extra saturation compensation methods can be avoided. A disturbance compensation technique is deliberately designed in the proposed control to enhance the robustness of the system while the bounded property can be ensured simultaneously. The whole control structure is relatively simple yet effective compared with existing control techniques which is much easier to implement in practical active suspension systems. Additionally, the overall stability of the closed-loop system is verified by the Lyapunov theorem. Various simulation results are provided to demonstrate the robustness and effectiveness of the proposed control design.

Zengcheng Zhou, Xingjian Jing, Menghua Zhang
Quasi-Zero Stiffness Magnetic Vibration Absorber

A magnetic-enhanced nonlinear energy sink with quasi-zero stiffness (QZS-ME-NES) is proposed, which mainly focuses on the influence of linear stiffness on vibration reduction. Quasi-zero stiffness is generally used in the field of vibration isolation. In terms of vibration absorption, it is inevitable that there is linear stiffness in nonlinear stiffness. Based on the magnetic force expression of permanent magnet, the dynamic equations of the linear oscillator (LO) equipped with the novel NES are established. Its dynamic characteristics are analyzed by numerical and approximate analytical solutions. The transient response and steady-state response of the LO equipped with the NES are studied. Moreover, the vibration attenuation performance of the novel NES is compared with that of the triple-magnet magnetic suspension dynamic vibration absorber (TMSDVA). The results show that the novel NES not only has the ability of adaptive broadband vibration suppression, but also significantly enhances the vibration attenuation of LO. In summary, the proposed NES is a reliable and effective vibration attenuation strategy.

Xuan-Chen Liu, Hu Ding
New Software Bionic Haptic Actuator Design Based on Barometric Array

To address the limitations of single-point tactile perception in soft biomimetic actuators, such as fixed positioning, limited coverage area, low resolution at long distances from the geometric center, and challenges in maintaining high sensitivity and stability over a broad range, a novel soft biomimetic tactile actuator based on a pneumatic array is designed and manufactured. Using liquid silicone rubber and BMP280 pressure sensor, the actuator was crafted by an injection molding process. Silicone gel was injected into the pressure sensor array, and vacuum extraction created a sealed space within the sensor cavity. The pressure excitation applied on the surface of the actuator could be converted into electrical signals, enabling tactile pressure detection. An STM32 microprocessor is utilized for building haptic information acquisition and processing system, with sensitivity assessed using the Kalman filter algorithm. Experimental results show that the soft biomimetic tactile actuator has high sensitivity and minimal repetition error, which can effectively detects changes in tactile force output, mitigates noise interference, and enhances the precision and stability of physiological pressure data feedback in physiotherapy applications.

Zige Yu, Sai Li, Mengying Lin, Hang Hu, Yingying Li, Qian Lei, Zixin Huang
Adaptive Robust Tracking Control for Aerial Work Platform Vehicle with Guaranteed Prescribed Performance

An aerial work platform vehicle (AWPV) plays a crucial role in conducting industrial activities at elevated heights, but its tracking control presents significant challenges due to complex nonlinearities and uncertainties. This study introduces a constraint-based adaptive robust control approach for AWPV that reliably achieves trajectory tracking while ensuring prescribed transient and steady-state performance (PTSSP). The control strategy takes into account time-variant uncertainties with unknown bounds, which may change rapidly and irregularly. The desired trajectories and PTSSP are respectively formulated as equality and inequality servo constraints. To incorporate the inequality servo constraints into the equality ones, a diffeomorphism approach is employed, leading to the formulation of new equality servo constraints. Consequently, the control task transforms into guiding the AWPV to adhere to the new equality servo constraints. Accordingly, an adaptive robust control method is designed to follow these constraints, incorporating an adaptive law for estimating online uncertainty bounds and compensating for uncertainties. Notably, no approximations or linearizations are utilized. The effectiveness and robustness of the proposed AWPV tracking control approach are rigorously validated through proofs and simulation results. This represents a pioneering effort in uncertain AWPV tracking control while ensuring PTSSP.

Jiawen Dai, Zheshuo Zhang, Bangji Zhang, Jie Bai, Hui Yin
A Novel Model Predictive Control Strategy for Continuum Robot: Optimization and Application

It is very important for continuous robots to achieve accurate and rapid control. However, the current continuum robot control faces many challenges. First, they often have complex nonlinear dynamics, including kinematics and dynamics equations, which makes it difficult to build accurate models, and conventional control methods do not work well on these complex systems. Secondly, the motion of a continuous robot system is continuous and coherent, requiring real-time control strategies to maintain stability and accuracy. These problems bring great challenges to the control of continuum robots. In this paper, the nonlinear system of continuum robot is modeled, and then the real-time control of continuum robot is realized by the model predictive control method. The real-time control problem of continuum robot is effectively solved and satisfactory control effect is obtained. In other words, for the continuous robot system, nonlinear modeling is first carried out, and then a new linear model of the system is obtained by linearizing and discretizing the nonlinear system model with feedback linearization method. On this basis, model prediction method is applied to the linearized model to achieve effective control of the target Angle. By solving the constraints of the model predictive control method, the control problem of the target Angle is successfully realized. The simulation also verifies the feasibility of the model predictive control method, which can realize the target Angle approaching the target value quickly. Compared with the traditional PD control method, the superiority of the model predictive control method is also proved.

Yakang Wang, Yuzhe Qian, Weipeng Liu
Finite Element Analysis and Error Compensation for Wrinkled Bellow-Like Soft Robotic Manipulator Kinematics Modeling

In this paper, a finite element analysis (FEA) and error compensation method are conducted for the wrinkled bellow-like soft robotic manipulator (WBSRM) kinematics modeling. Firstly, WBSRM is designed, which has good axial expansibility and radial bending deformation. The link and restriction of the interference plate make the WBSRM have better motion effect and can be better used implemented for FEA. The wrinkled bellow actuator has good axial scalability. Then, the model of WBSRM based on the constant small curvature (CSC) methodology is established. To verify the accuracy of the established kinematics model, the FEA approach is employed, in which the local coordinate system is established to obtain the local coordinate value and the curve length is calculated by curve fitting and integration, such that the idealized constraint limit of the common actuator length can be avoided. Finally, the FEA simulation result and the established kinematics model are compared and analyzed. Concerning on the modeling error between the established mathematical model and the simulation result, the back propagation neural network (BPNN) technique is introduced to realize the error compensation. The obtained method results show that the compensation method can effectively eliminate the modeling error and then dedicates to characterize the detailed kinematics model of the WBSRM.

Haibin Huang, Yingjie Li, Yingbo Huang, Jing Na
Suppression of Galloping Oscillations Using Perforated Bluff Bodies

This study explores the potential effect of utilizing perforated bluff bodies on suppressing galloping oscillations. Six types of perforated bluff bodies with vertically parallel two holes, four holes, and six holes are proposed, and three kinds of surface treatments including all-sided and non-all-sided designs are implemented to vary the perforated shape. A comprehensive aero-electromechanical mathematical modelling is established for better analysing the proposed passive vibration suppression system. Wind tunnel experiments and numerical simulations reveal that increasing the number of holes on perforated bluff bodies can effectively reduce the vibration amplitude and increase the galloping cut-in wind speed. Furthermore, only the all-sided six-hole perforated bluff body has the greatest potential to suppress galloping oscillations. Further wind tunnel computational fluid dynamics (CFD) simulations are also performed to obtain the transverse force coefficients so as to investigate the underlying aerodynamic reasons behind the observed phenomena. Compared with most of the existing galloping oscillations suppression methods, this technique has the advantages of no external energy, lightweight, and simple design, etc., which makes it promising for possible practical applications.

Juntong Xing, Masoud Rezaei, Huliang Dai, Wei-Hsin Liao
Motion Planning for Wave-Like-Actuated Manta-Inspired Amphibious Robots

Inspired by manta rays, an amphibious robot is designed by utilizing a wave-like mechanism for propulsion. In terms of robot design, the swimming characteristics of the manta ray are analyzed, and mechanical structures such as flexible biomimetic fins and wave-like propulsion mechanisms are designed, enabling the robot to move both in water and on land. Furthermore, the kinematic model of the wave-like-actuated manta-inspired amphibious robot is established. Then, a path planning method based on the improved Rapidly-exploring Random Tree (RRT) algorithm is proposed, and combined with S-curve acceleration and deceleration planning to achieve velocity planning for robots. Experiments are conducted to validate the robot’s motion performance and the effectiveness of the motion planning algorithm.

Yixuan Wang, Qingxiang Wu, Xuebing Wang, Ning Sun
Time-Optimal Anti-swing Trajectory Planning of Double Pendulum Crane Based on Chebyshev Pseudo-spectrum Method

As a typical underdrive system, an overhead crane has been widely used in modern industrial production and transportation. However, when the load volume in the crane system is too large or the hook quality is too large, the bridge crane system will show the characteristics of double-pendulum, increasing the difficulty of control. Based on this, this paper proposes a time-optimal trajectory planning method for the double-pendulum bridge crane system, which can be obtained. Specifically, the paper first transforms the system kinematics model; based on this basis Then, considering the various constraints including the two-level swing angle and the trolley speed and acceleration limit, the optimization problem is transformed into a nonlinear programming problem which is easier to solve, and the trajectory constraints can be considered very conveniently in the conversion process. Solving the nonlinear programming problem yields the time-optimal trolley trajectory. Finally, the simulation results show that the time-optimal trajectory planning method has satisfactory control performance.

Ken Zhong, Yuzhe Qian
Nonlinear Inertia and Its Effect Within an X-shaped Mechanism

This paper presents a new understanding and development related to nonlinear inertia and its effect in coupling with an X-shaped anti-vibration mechanism, which is validated by prototyping and experiments. The new inertial unit integrated in a well-designed X-shaped mechanism allows larger excitation displacements and more adjustable inertia ratios, resulting in significantly lower vibration transmissibility and resonance peak, and produces three different typical nonlinear inertia forms. A key parameter indicator (Ratio of Inertia) is proposed to identify and indicate the different types of nonlinearities, and the resulting beneficial effects are explored. The performance improvement in dynamics with respect to the linear counterpart is evaluated for different nonlinear inertia forms. The results show that: (a) The U-shaped symmetrical nonlinear inertia coupling with X-shaped mechanisms can provide better vibration isolation performance at low frequency; (b) High-frequency transmissibility can be tuned to different level, indicating a tunable band-suppress property, which is a unique property discovered in this study; (c) the nonlinear inertia contributes significantly to tune the interactive force between vibration source and object in the low frequency range (<10 Hz in our prototype) and obviously helpful and robust to stronger excitations. This study provides new insights into the application of nonlinear inertia in various engineering systems to achieve better passive vibration suppression or isolation.

Zhenghan Zhu, Xingjian Jing
Metamaterial Beam with Bistable and Monostable-Hardening Attachments for Broad-Band Vibration Attenuation and Energy Harvesting

Dynamic local resonating (LR) metastructures possess the ability to suppress the propagation of vibrations within a specific frequency range known as a bandgap. However, metastructures with pure linear local resonators have limited bandgap size and inevitably form new resonating peaks close to the bandgap. This paper proposes a metastructure that features alternatively arranged oscillators with bistable and monostable cubic hardening nonlinearities, as well as electromechanical coupling. This design effectively suppresses high-amplitude resonating transmission peaks near the bandgap and maintains the bandgap at high excitation levels. In addition, it can create a broad bandwidth with high power output, which can be applied as a practical source of electrical energy, thereby forming a well-balanced and performance-enhanced dual-functional metastructure for vibration suppression and energy harvesting. The proposed metastructure is established and calculated using a distributed-parameter model. The influence of nonlinearity stiffness and electrical-mechanical coupling index are investigated. Results show that enhanced performance of both vibration attenuation and energy harvesting can be realized with the proposed metastructure at a large range of excitation level. The parametric results offer a valuable reference for the development of dual-functional metastructures for simultaneous vibration suppression and energy harvesting.

Che Xu, Liya Zhao
An Improved Incremental Classifier and Representation Learning Method for Elderly Escort Robots

Elderly escort robots are gradually becoming one of the important roles of elderly care services. The problem that restricts the wide application of elderly escort robots in practical scenarios is how to make them have the ability of continual learning, so that they can autonomously learn and respond in dynamic service scenarios. To this end, we propose a continual learning network based on an improved Incremental Classifier and Representation Learning (iCaRL) method for robots. The network uses replay and regularization strategy to train a ResNet with incremental classes. We mainly focus on improve the replay method in two aspects. Firstly, a density-peaks-based prototype selection strategy is proposed, which allow the network to obtain accurate prototype for arbitrary-shaped data distribution. Secondly, A self-organizing incremental neural network is introduced for each class as exemplar memory to replay in the ResNet training process. It can not only learn generalized representations of each class to enhance the diversity of its exemplars, but also learn any number of classes due to its dynamic architecture. Experimental results demonstrate that our method can achieve better learning effectiveness and efficiency over several state-of-art algorithms.

Ke Huang, Mingyang Li, Yiran Wang, Weijie Huang, Menghua Zhang
Exact Dynamic Analysis of Viscoelastic Double-Beam System Using Dynamic Stiffness Method

Double-beam structure with a viscoelastic core has a wide range of application scenarios in engineering. To investigate the dynamic behavior of this type of structures, the dynamic stiffness method and Wittrick-Williams algorithm are employed to obtain the dynamic characteristics of the double-beam system. Besides, the modal superposition method is utilized to calculate the dynamic response. By comparing with finite element solutions, the accuracy of proposed method is verified. Results show that the damping coefficient of the connection layer and the axial tension of the upper beam have a significant effect on reducing the structural response in a certain range. The methods and conclusions in this paper will be helpful to structural design and vibration suppression of practical structures.

Fei Han, Nianfeng Zhong, Tao Yang
Nonlinear Control Strategy for Tower Cranes with Variable Cable Lengths and Multivariable State Constraints

Tower cranes play a crucial role in construction, but their complex dynamics and under-actuation pose significant control challenges. This research proposes a sophisticated multi-variable state-constrained controller for tower cranes with varying cable lengths. By introducing auxiliary terms, the controller effectively constrains the actuated variables, underactuated variables, and specific composite variables, ensuring precise cargo positioning and swing suppression. The control approach for tower cranes in this paper enhances both safety and operational efficiency. Finally, the proposed method's feasibility and robustness are validated through simulation experiments.

Hui Guo, Wei Peng, Menghua Zhang, Chengdong Li, Fei Jiao
Design and Dynamic Analysis of a Flexible Inertia Device for Vehicle Suspensions

The inertia device has gained widespread utilization in vibration isolation systems owing to its capability of effectively changing the inherent frequencies of the system. This paper presents a flexible inertia (FI) device that consists of the transmission device, electromagnetic damping device and flywheel. The inertial characteristics of the FI device can be designed in series with an electromagnetic damper and a flywheel. Through this design, FI device can reduce the rigid impacts during severe vibrations and can set different initial damping to get different equivalent inertance. The dynamic model of the proposed FI device is integrated into the quarter-vehicle suspension. The parametric analysis is carried out to determine the key inertia parameters that influence the vibration isolation performance. Simulation results indicate that the suspension system with the FI device can obtain better vibration isolation performance compared with the passive vibration isolation system.

Bohuan Tan, Xingui Tan, Jingang Liu, Hai Li, Yilong Xie
A Quasi-Zero Stiffness Nonlinear Absorber Based on Centrifugal Force

A design approach for quasi-zero stiffness (QZS) nonlinear absorbers for rotor system vibration suppression is proposed in this paper. An example of the QZS nonlinear absorber is designed for a single-disc rotor system considering gyroscopic. The nonlinear absorber consists of a rigid mass ring and four circumferentially distributed nonlinear springs, which are coaxially mounted and rotated together with the disc. The equations of motion of the rotor system with the QZS nonlinear absorber are derived by the Lagrange’s equation. According to the motion equations, it shows that the rigid mass ring reveals a negative stiffness due to the centrifugal forces generated by its vibration. The quasi-zero stiffness is realized by combining the positive stiffness provided by the nonlinear springs and the negative stiffness generated by the centrifugal forces. The stability of the rotor system is compromised at high rotational speed due to the speed-dependent negative stiffness provided by the centrifugal force. Thus, the influence of the linear and nonlinear stiffness on vibration suppression and stability of the rotor system are discussed. The present results indicate that increasing the linear stiffness appropriately can enhance the decay rate of the peak vibration and improve the stability of the rotor system.

Hulun Guo, Zhiwei Cao
A Cellular Strategy for Eliminating the Failure of Nonlinear Energy Sinks Under Strong Excitation

Nonlinear energy sinks (NES) have numerous advantages, such as wide vibration bandwidth and excellent vibration reduction performance. However, under high excitation intensity, its high vibration attenuation effect often becomes ineffective. Therefore, exploring methods to address this issue and broaden their application range remains a subject for further research. This paper investigates the dynamic characteristics of systems composed of linear oscillators and multiple NES cells and studies the vibration reduction effect of NES cells using the Complexifiction-Averaging (CxA) method, and the obtained results were numerically verified using the Runge-Kutta (R-K) method. The results show that when NES cells are present in the form of cells, increasing the number of cells can reduce the system's saddle-node (SN) bifurcation region, especially shrinking the frequency island region produced by the system under strong excitation. When the number of cells reaches a certain value, the frequency island of the system disappears. Additionally, regardless of whether the system generates frequency islands or not, increasing the number of cells generally improves the vibration reduction efficiency of NES cells. Thus, the cellular strategy proposed in this paper effectively addresses the ineffectiveness of traditional NES under strong excitation and expands its application range.

Sun-Biao Li, Hu Ding
A Stable Adjustable Nonlinear Energy Sink

The nonlinear energy sink (NES) is very sensitive to external excitation intensity, which seriously hinders the application of NES in engineering practice. In this paper, a stable adjustable NES model is proposed, which is consisted of a pair of axially compressed clamped beams, guide rods, mass blocks, and flexible hinges. By adjusting the length of the guide rod, the distance of the clamped beams, and the geometric relationship between the buckling deflection, it is convenient to convert between three different types of NES: monostable, bistable, and tristable. The Lagrange equation is used to derive the dynamic equation of the system, and the approximate analytical solution is obtained by using the harmonic balance method, which is then mutually verified with the numerical solution. Through theoretical calculation and experimental verification, three different types of NES dynamic responses and vibration reduction mechanisms are studied under different excitation intensities. The results show that NES can achieve good vibration reduction effects by strong modulation response (SMR) under appropriate excitation amplitudes; Bistable NES can reduce the energy threshold of NES and effectively suppress small amplitude vibrations by performing chaotic inter well oscillations. The tristable NES can perform chaotic inter well oscillations and eliminate detached resonance curve, which has a good vibration suppression effect on large vibrations. The device proposed in this paper can conveniently adjust the type of NES based on different external excitation intensities, providing a way to address the sensitive issue of excitation intensity in engineering applications of NES.

You-cheng Zeng, Hu Ding, Jinchen Ji
Gait-Planning-Based Path Planning for Crocodile-Inspired Pneumatic Soft Robots

In many cases, soft robots with their inherent flexibility, ease of interaction, and high adaptability in complex environments, receive widespread attention. Among them, gait planning is a key technology to ensure the performance of soft robots. This paper proposes a gait-planning-based path planning method for crocodile-inspired pneumatic soft robots. Based on the crocodile-inspired pneumatic soft robots, the motion characteristics of the robot with different gaits are analyzed. Then, a path planning method using A* algorithm is proposed according to the environmental characteristics of road width, obstacles, and other road information. The experimental environment is built independently to complete robot path planning and gait selection and verify the effectiveness of the proposed gait-planning-based path planning method.

Yize Ma, Qingxiang Wu, Zehao Qiu, Ning Sun
Research on Nonlinear Energy Sink Vibration Reduction of Floating Raft System

The floating raft vibration isolation system has the problem of multi-frequency vibration in the process of vibration. The existence of multi-frequency vibration makes it difficult to apply linear vibration absorption. In this paper, the nonlinear vibration absorption is applied to the floating raft vibration control, and the floating raft vibration control strategy using multiple nonlinear energy sinks (NESs) distributed arrangement is proposed for the first time. Considering that the base of the original floating raft system has elastic support, the natural frequencies and modes of the floating raft system are analyzed, and the dynamic models of the floating raft system with different distribution modes of NES are established. Through dynamic analysis, the influence laws of NES distribution on floating raft vibration control are compared. Based on the vibration reduction of low-order and high-order modes, the NES layout mode is analyzed. The results show that the distributed nonlinear energy sinks arrangement can effectively control the vibration of floating raft, and has good vibration damping effect on all modes of floating raft. The floating raft vibration attenuation for low-order and high-order modes should be arranged in different NES placement modes. In conclusion, the study of this paper provides a new and efficient control strategy for floating raft vibration.

Hong-Li Wang, Hu Ding
X-mechanism Guided Elastic QZS Vibration Isolator Design for Beneficial Nonlinear Stiffness

Mechanical metamaterials are emerging vividly in recent decades elevating the limits of mechanical properties. Compared to traditional mechanical materials with classical elastic theory, the state-of-the-art mechanical metamaterials possessed many unconventional mechanical properties, such as negative stiffness, zero stiffness, ultra-toughness, negative Poisson’s ratio, etc. As stiffness being the natural property of all materials, modification on material stiffness to achieve quasi-zero stiffness attracts many research attentions. In this research, an X-mechanism guided design paradigm on elastic isolator with quasi-zero stiffness was explored by integrating both softening and hardening mechanisms from rigid body X-mechanism into soft elastic isolator of small dimension. The synergistic effect of softening and hardening mechanisms was investigated analytically and numerically. While the finite element analysis models illustrated the mechanism on reaching quasi-zero stiffness, experimental test on 3D printed elastic isolator samples demonstrates the promising results of quasi-zero stiffness range and explores favorable engineering features. The printed elastic isolator possessed a size comparable to a coin. Furthermore, the loading capacity of proposed elastic isolator are quantified with both finite element analysis and experimental test. With both finite element analysis and experimental testing, 3D printed elastic isolator samples with promising quasi-zero stiffness behavior illustrates the possibility of performing superior vibration isolation and actuator control within one-piece tiny devices.

Chuanping Liu, Xingjian Jing
Design and Vibration Control of Secondary Suspension for Maglev Train Based on Magnetorheological Fluid Damper

When the maglev train with a speed of 600 km/h runs at high speeds, the vertical carriage vibrations caused by irregularity of tracks are intensified, affecting passenger comfort and even safety. Therefore, it is necessary to find new damping devices to reduce carriage vibrations. Magnetorheological fluid dampers have advantages such as continuously adjustable damping, low-power consumption, high damping force output, and fast response speed. This paper firstly discusses the feasibility of applying magnetorheological fluid dampers to the secondary suspension system of maglev vehicles. It investigates the working mode, installation position, and stroke of magnetorheological fluid dampers for high-speed maglev trains. Based on a simplified suspension model for maglev trains, a magnetorheological fluid damper control system based on fuzzy logic is designed. The effectiveness of the proposed semi-active secondary suspension system based on magnetorheological fluid dampers is verified through numerical simulations, demonstrating its ability to effectively improve the vibration reduction performance and ride comfort of maglev trains.

Yougang Sun, Dandan Zhang, Hongyu Ou, Guobin Lin, Haiyan Qiang
Nonlinear Dynamic Analysis of Flywheel Rotor Systems with Multiple Fit Clearances

Dynamic analysis of a flywheel rotor system with multiple bearing clearances is conducted in this study. Firstly, Jones-Harris method is used to deduce the equivalent nonlinear support stiffness of angular contact high-speed ball bearing with preload considered. Ignoring the structural deformation, the contact model of inner and outer rings with clearance is used to describe the clearance fit between the outer ring and the sleeve, and between the sleeve and the bearing pedestal. Based on Hertz contact theory, the discontinuous and nonlinear support stiffness is then obtained. The lumped parameter model of rotor-bearing-pedestal system is established and verified based on dynamic test results. Based on this, the influence of clearance fit parameters and external excitation parameters on the vibration response amplitude of the system is analyzed. When the radial displacement is greater than the fit clearance, the radial support stiffness changes abruptly and increases rapidly. If it increases to a certain value, the increase of radial stiffness would slow down. The vibration response curve appears sub-harmonic resonances and amplitude jump. The increase of the fit clearance aggravates the vibration response level, the resonance speed of the system moves to the low speed, and the jumping phenomenon becomes more prominent, which is not conducive to the stable operation of the rotor system.

Qinkai Han, Zhaoye Qin, Fulei Chu
Comparison Studies of Dynamic Characteristics for Coupled Bearing-Rotor Systems with Fixed and Pivot-Supported Pads

The coupled bearing (including four-pad tilting pad journal bearings and six-pad tilting pad thrust bearings) is mainly used in a nuclear power circulating pump to support the high axial loads and radial loads from a vertical rotary system with minimum power loss, low vibration, and high load capacity. Its lubrication and vibration characteristics have significant effects on the dynamic performance and operation reliability of the nuclear power circulating pump. In this paper, an original mixed-lubrication dynamic model for the coupled bearing-rotor system is proposed to study the dynamic characteristics of the system considering the effects of the pivot clearance, asperity contact, and elastic deformation. The innovation of the proposed model is that it integrates the horizontal-rocking vibrations of the rotor and pivot pads with the mixed lubrication of the coupled bearing. The coupling effects between the dynamic characteristic of the rotor and the lubrication behavior of the coupled bearing are revealed. In addition, the time-dependent dynamic performance of the fixed pad coupled bearing and the tilting pad coupled bearing are compared. Numerical results indicate that the self-adaptive tilt of the pad makes the oil film pressure more evenly distributed on each pad of the journal and thrust bearings. The tilting pad coupled bearing can effectively improve vibration resistance, system stability, and load-sharing capacity compared to the fixed pad coupled bearing. It is expected that the proposed mixed-lubrication dynamic model can provide guidance for improving the lubrication performance of the coupled bearing and the stability of the system.

Wennian Yu, Chaodong Zhang, Lu Zhang
Nonlinear Dynamic Performance and Analysis Model of Pump Valve System of Diaphragm Pump Hydraulic End

The analysis of the dynamic lift performance and valve gap flow characteristics of the diaphragm pump hydraulic end valve has an important impact on the safety and stability of the diaphragm pump valve design. In this paper the dynamic performance of valve and valve gap flow of a new diaphragm pump is calculated and analyzed in Chongqing pump industry. Firstly, the nonlinear motion equation of a new type of cone valve, and the dynamic lift curve of the pump valve is calculated. Calculated valve gap flow of the pump valve and compare it with the actual flow data to verify the correctness of the dynamic analysis model of the pump valve. Based on the dynamic model and the main functions of diaphragm pump valve established in this paper, maximum flow rate, ending speed and hydraulic loss, are calculated and analyzed. Meanwhile, the effects of erosion failure and collision failure on the service life of diaphragm pump cone valve are analyzed. At the same time, the influence of impulse and spring stiffness on the volume efficiency of diaphragm pump is calculated and discussed. Through the above research and analysis, the practical engineering guiding significance is provided for the geometrical optimization and design of the hydraulic end cone valve of the new mine diaphragm pump.

Jiameng Zhang, Wensheng Ma, Chunchuan Liu, Zicheng Zhao
Bird-Inspired Nonlinear Oscillator with Triboelectric Nanogenerator for Vibration Control and Energy Harvesting

A bird-inspired nonlinear oscillator (BINO) is proposed for low-frequency vibration control and energy harvesting of bridges. By integrating the spring into the oscillator, the space utilization rate and reliability are further improved. Theoretical analysis and experimental results show that BINO with triboelectric nanogenerator damper (BINO-TENGD) with quasi-zero stiffness (QZS) has excellent low-frequency vibration isolation performance and stable output voltage. In addition, BINO-TENG can produce resonance phenomenon in the frequency range of 3-8 Hz under bistable condition, and obtain high output. Finally, BINO-TENGD under QZS condition is applied to the beam bridge, and the results show that adding BINO-TENGD to the beam bridge is beneficial to suppress vibration. Therefore, BINO has a certain application prospect in the fields of bridge low-frequency vibration control, vibration detection and energy harvesting.

Jiayi Liu, Yingxuan Cui, Tao Yang, Xingjian Jing
Improvement of Small Target Detection Algorithm Based on YOLOV5

Target detection has always been a difficult problem in computer vision. The commonly used target detection algorithms are Two stage and One stage. In order to address small ground targets and reduce the storage of UAV, the paper present an improved method on the basis of YOLOV5. All C3 modules are replaced by in the backbone network. It can improve the speed and accuracy of the network target detection, and improve the efficiency of the model training and inference. A new feature fusion mechanism is proposed, which greatly improves the feature acquisition and fusion capabilities for networks. A 160*160 detection head is added at the end of the network. Experimental Specific improvements resulted in a 3.6% increase in recall, a 3.9% increase in mAP_0.5, and a 2.8% increase in mAP_0.5:0.95.

Shoujun Lin, Lixia Deng, Huanyu Chen, Lingyun Bi, Haiying Liu
Aerodynamic Analysis of a Double Elastic Panel-Cavity with One Side Exposed to Supersonic Flow

In this paper, the aeroelastic stability and nonlinear response of a structural-acoustic system that consists of two panels with an acoustic cavity between them is investigated. A non-linear higher-order shear deformation zig-zag theory is adopted to model the composite laminated panel, and the linear wave equation is employed for modeling the compressible fluid in the cavity. Based on the Piston aerodynamic theory, a theoretical approach with the finite element method for solving instability modes and the transient response of the panel-cavity aerodynamic system is suggested. The aeroelastic instability boundary under different dynamic pressures is calculated, and the influence of the stiffness ratio between the top and bottom elastic panels is analyzed.

Hao Liu, Yegao Qu, Guang Meng
Observer-Based Robust Control for Active Suspension Systems by Employing Beneficial Disturbances and Coupling Effects

In this paper, a novel observer-based robust control method is designed for an active suspension system with inevitable disturbances as well as coupling effects. The difference from the existing control methods is that the designed control method specifically investigates the influences of disturbances as well as couplings. This method effectively mitigates the negative disturbance and coupling effects while retaining the positive effects, leading to enhanced robustness. To achieve this, a nonlinear disturbance observer is employed to accurately estimate both parametric/uncertainties and external disturbances. And on this basis, positive or negative effect indicators that assess the impact of disturbances and couplings on the active suspension system, thereby incorporating them into the controller design. The entire suspension system’s asymptotic stability is ensured by the Lyapunov technique. Experimental results are presented to validate the effectiveness of the proposed control method.

Menghua Zhang, Zengcheng Zhou, Qiang Liu, Xingjian Jing
Parametric Study on Performance of Parallel Asymmetric Nonlinear Energy Sinks

The complexification-averaging method is utilized to study the amplitude-frequency response of a system connected to a parallel asymmetric nonlinear energy sink (NES) under harmonic excitation, and the Runge-Kutta method is used to analyze the change law of the frequency band of the higher branches of response and the strongly modulated responses with the assistance of the complexification-averaging method. Under shock loading, the effect of parallel asymmetric NES parameters on its vibration absorption efficiency is investigated. The results demonstrate that the frequency band of higher branches of response is widened by reducing the stiffness ratio, mass ratio, and damping ratio of the two NES, emphasizing the fact that the frequency band of the strongly modulated response can be widened or narrowed with the reduction of these parameters. Moreover, reducing the mass ratio and damping ratio of the two NESs decreases the vibration absorption efficiency when the system is subjected to a shock load. However, the vibration absorption efficiency increases by reducing the stiffness ratio.

Huiyang Li, Jianen Chen
Harnessing LSTM for Nonlinear Ship Deck Motion Prediction in UAV Autonomous Landing Amidst High Sea States

Autonomous landing of UAVs in high sea states requires the UAV to land exclusively during the ship deck's “rest period,” coinciding with minimal movement. Given this scenario, determining the ship's “rest period” based on its movement patterns becomes a fundamental prerequisite for addressing this challenge. This study employs the Long Short-Term Memory (LSTM) neural network to predict the ship's motion across three dimensions: longitudinal, transverse, and vertical waves. In the absence of actual ship data under high sea states, this paper employs a composite sine wave model to simulate ship deck motion. Through this approach, a highly accurate model is established, exhibiting promising outcomes within various stochastic sine wave combination models.

Feifan Yu, Wenyuan Cong, Xinmin Chen, Yue Lin, Jiqiang Wang
Aircraft Anti-Skid Braking Nonlinear Control Based on ADRC

An efficient and safe landing procedure for an aircraft holds significance across economic, operational, and strategic considerations. Achieving the shortest possible landing distance without skidding necessitates a variable braking force that consistently matches the friction force. Thus, the control strategy of the Anti-skid Braking System (ABS) must encompass the ability to address pronounced nonlinearity and substantial unpredictable disturbances, while also regulating the wheel slip ratio to ensure a stable braking process. This study introduces the application of the Active Disturbance Rejection Control Technique to the anti-skid braking system. The proposed control algorithm guarantees that the closed-loop system operates within the vicinity of the peak point of the stable region on the friction curve. This optimization significantly enhances both braking performance and overall safety.

FengRui Yu, Jingting Zou, Xinmin Chen, Yue Lin, Feifan Yu
Design of Synchronous Charge Extraction Multi-input Piezoelectric Energy Harvesting Circuit

Piezoelectric energy harvesting (PEH) holds remarkable potential in energizing low-power sensors within wireless sensor networks, thereby alleviating the necessity for frequent battery replacements. Nevertheless, the output power yielded by a solitary piezoelectric element often proves inadequate to meet the demands of powering sensor nodes. Multi-input piezoelectric energy harvesters emerges as a compelling strategy to not only bolster power output but also to expand operational bandwidth. This augmentation necessitates judicious considerations in the design of energy harvesting circuits, with due regard for the distinct attributes inherent to various harvesters. A multi-input self-powered parallel synchronized switch harvesting on inductor (MISP-SSHI) circuit for piezoelectric energy harvesting is proposed in this study. The MISP-SSHI circuit adeptly addresses the divergence in voltage amplitudes and phase disparities across piezoelectric elements, while effectively obviating the mutual interference that can arise during energy extraction. A peak detection module is introduced and meticulously engineered to discern the peak of the piezoelectric output signal, which facilitates energy extraction without necessitating any external power supply. This process entails the judicious extraction of charge from both the clamped capacitance and the peak detection capacitance of the piezoelectric element, culminating in a discernible enhancement of the energy conversion efficiency. The intricate interplay between output power, efficiency, and load resistance characterizing the MISP-SSHI is rigorously examined through a combination of simulation and experimental analyses. A comparative simulation evaluation is conducted under varying excitation conditions. Substantiation of the theoretical framework is further attained through the integration of a DC-DC converter and the meticulous implementation of impedance matching across diverse load scenarios. Encouragingly, the alignment between simulation results and experimental outcomes lends credence to the efficacy of the proposed circuit design.

Bin Zhang, Hao Sun, Ruibo Chai, Shizhou Lu, Shengxi Zhou
Vibration Absorption of Nonlinear Energy Sink for Non-resonant Frequency Band of Rectangular Plate

In this paper, a nonlinear energy sink (NES) is designed to suppress the vibrations of a rectangular plate, where the vibrations within a non-resonant band of the plate are mainly investigated. The selected frequency range is 9–11 Hz with a loading frequency interval of 0.5 Hz. The harmonic excitation experiments with fixed frequency are conducted within the non-resonant band to obtain its amplitude-frequency curves. The results indicate that the NES always has effective vibration absorption with the variations in NES mass and spring stiffness under low excitation accelerations. However, the rectangular plate exhibits a higher branch of response within the low-frequency range under high excitation accelerations. Metrics such as the effective value of response acceleration and the vibration level are introduced to evaluate the experimental results to analyze the vibration absorption of the NES. The study reveals that optimal performance is achieved when a non-weighted NES with a spring having a wire diameter of 1.2 mm and an external diameter of 10 mm is attached to the rectangular plate. This device yields a reduction of vibration level by 7.29 dB.

Jie Wu, Jianen Chen
Uniform Load Assembly Method of PEMFC Under Vibration Based on the Wave Spring Suspension Support

Proton exchange membrane fuel cell (PEMFC) as an efficient energy device, has great application prospects. However, due to the assembly design, the efficiency and reliability of PEMFC are easily affected, especially the uneven distribution of bipolar plate contact pressure. Therefore, a simple and reliable assembly methodology based on the wave spring is proposed to achieve the purpose of uniform load and obtain high-performance PEMFC in this paper. The effectiveness of wave spring suspension approach is verified by experiments. This achievement represents an important step in improving the performance of PEMFC.

Biyu Pan, Dong Guan, Rui Wang, Zhen Chen, Ting Chen
Origami-Inspired Vibration Isolation with Inherent Nonlinear Inerter

Origami-inspired structures have shown strong nonlinearity on their force-displacement response, which could be used for vibration isolation by appropriate selections of structural parameters. However, the influence of the structural weight on the dynamic performance is rarely considered and discussed during the modelling and analysis of such origami-based vibration control structures. In lightweight isolation applications, the structural weights should be considered as they can bring beneficial effects on the system capability. A recent study found that the structural weight within the origami-inspired vibration system can induce strong dynamic nonlinearity as a tunable inerter. In this paper, the origami-inspired quasi-zero stiffness (QZS) vibration isolators under different tunable inerter conditions are experimentally investigated to explore their isolation performances. Compared with the corresponding system that has no self-weight considered, the resonance response of the proposed QZS system can be suppressed and also the effective isolation frequency band of the QZS system can be improved towards to a lower frequency range.

Kan Ye, J. C. Ji, Jianchun Li, Keisuke Yamada
Analytical Optimization Analysis of Inerter-Based Vibration Absorbers with Negative Stiffness

Traditional optimal design of NS-DVAs (Negative stiffness- dynamic vibration absorbers) is based on an extension of fixed-point approach, which equalizes the triple fixed points of the dynamic amplification function (DAF) to achieve approximate analytical H∞ optimization for dynamic reduction. However, this leads to stiffness matrix anomalies, resulting in a significant static amplification effect. For vibrations excited combining static and dynamic components, the static amplification may lead to adverse control effect, or even magnify the peak response, particularly, wind load. In order to solve these problems, an analytical optimal design approach for inerter-based vibration absorbers (IVAs) with NS (NS-IVAs) is proposed for balancing static amplification and dynamic reduction effects. Firstly, the characteristics of static amplification and dynamic reduction factors are analyzed. Subsequently, the relationship between the negative stiffness parameter and dynamic-static proportion is empirically formulated for practical application. Finally, the results of the numerical examples for wind-induced vibration control have shown that the proposed approach is particularly effective for the excitations dynamically characterized by low frequency and mixed with static components.

Jing Bian, Ning Su
Advances in Applied Nonlinear Dynamics, Vibration, and Control – 2023
Xingjian Jing
Hu Ding
Jinchen Ji
Daniil Yurchenko
Copyright Year
Springer Nature Singapore
Electronic ISBN
Print ISBN

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