Journal of Vibration and Control

Vortex-induced vibration (VIV) of the main girder is a prominent issue affecting coastal long-span bridges. Long term VIV can lead to structural fatigue damage and local component deterioration. In this paper, the VIV performance of a curved cable-stayed bridge with a bluff body section was studied through wind tunnel tests. The bridge features a cross-section with a one-way slope and asymmetric structures along the longitudinal and transverse directions. Wind tunnel tests were conducted on a sectional model with a geometric scale ratio of 1:50, along with a full-bridge aeroelastic model, to examine the VIV behavior of the bridge. In addition, the effects of structural damping ratio, aerodynamic shape of section, and other factors on the VIV performance were analyzed. The test results reveal that the VIV performance of one-way slope asymmetric cross-section bridge varies significantly under different side incoming flows. Therefore, wind tunnel tests should be conducted under two-side incoming flow. The addition of a vertical guide plate, inclined web, and air nozzle to the original design section shows limited effectiveness in inhibiting VIV. However, increasing the structural damping ratio can effectively suppress the VIV response. The installation of eddy-current tuned mass dampers (ECD-TMD) proves to be a significant improvement in enhancing the structural damping ratio. Properly designing the technical parameters of ECD-TMD can successfully curb VIV response. There exists a certain deviation between the dynamic characteristics of the actual structure and the finite element model. Therefore, before formal installation, the ECD-TMD parameters should be adjusted based on the actual parameters. The measured modal damping ratio after the installation of ECD-TMD in this project meets the requirements for VIV control, indicating that the ECD-TMD is in good condition and effectively fulfills its purpose.

The nonlinear dynamics equation governing the behavior of axially moving viscoelastic beams is established in this paper, based on Hamilton’s principles. The Galerkin method is employed to discretize the equation for numerical analysis. Nonlinear parametric vibration control for axially moving viscoelastic beams is explored using piezoelectric laminated actuators based on LQR optimal linear control and SMC sliding mode control strategies. The stability of the moving beam is examined in respect of moving speed and active control. The influence of actuator position and control schemes on vibration control performance for the moving beam is also examined. In respect to linear and nonlinear equations, two control strategies of LQR are given to illustrate the control performances. The sliding mode control (SMC) is also given to reduce the vibration of the moving viscoelastic beam and exhibit the control performance and its robustness.

This paper addresses the time-varying formation control problem of second-order networked multi-agent systems consisting of a virtual leader and multiple followers, where random communication constraints in the forward and feedback channels as well as actuator and sensor faults are considered. A state observer is designed to estimate the system state and the potential faults, based on which a time-varying formation active fault-tolerant predictive control scheme is proposed. Then, a necessary and sufficient condition is derived to guarantee the stability of the closed-loop system and to achieve the time-varying formation, which is independent of random communication constraints as well as actuator and sensor faults. Finally, simulation results of three contrastive cases are presented to verify the effectiveness of the proposed control scheme.

It is generally accepted that semi-actively (S/A) controlled dampers can significantly improve the behaviour of a road or rail vehicle. In the case of a railway vehicle, it is possible to increase comfort using S/A control of vertical or lateral secondary dampers. On another way, S/A control offers the possibility of solving a contradiction in the damping requirements for different driving modes, in the case of control of bogie yaw dampers. However, this case has not yet been sufficiently investigated. This paper deals with applying magnetorheological dampers with semi-active control in the locomotive bogie to reduce hunting oscillation. The magnetorheological bogie yaw damper design, new algorithms for its control and application on a complex multi-body locomotive model that simulates fast running on a real straight track are shown. An essential part of the paper focuses on the effect of the damping force level and damper force transient response time. The results have shown that using the semi-active control of the yaw dampers makes it possible to reduce vehicle body lateral oscillation by 60% and improve running stability for higher equivalent conicity and subcritical speed. The critical speed can be increased by more than 250 km/h. The efficiency of the proposed semi-active control increases with increasing damping force level and decreasing transient response time. The control is most effective under conditions of low equivalent conicity.

In strong impact environment, traditional impact test platform cannot obtain high peak acceleration, resulting in products being hindered in the testing process. The objective of this paper is to build the rebound-collision impact amplifier that can be used in a strong impact environment and to investigate its mechanism, influencing factors, and amplification effect. The kinematic model of the rebound-collision impact amplifier was established by combining dynamic contact theory with classical collision theory, considering energy loss, and introducing collision recovery coefficient. A theoretical formula for calculating acceleration and acceleration magnification was derived. The effects of the collision duration ratio, the mass ratio of the amplification platform to the falling platform, and the reserved clearance on the acceleration magnification were investigated, respectively. Finally, the feasibility test was verified. The test results show that the rebound-collision impact amplifier motion model is in good agreement with the theoretical model. Acceleration magnification decreases with increasing mass ratio and increases with increasing collision duration ratio. The ideal reserved clearance can be found to make the acceleration of the amplification platform obtain the maximum value. Selecting the ideal reserved clearance is more conducive to impact amplification.

In order to study the dynamics in a dual-rotor system in the presence of a bearing pedestal early looseness fault, a 12-degree-of-freedom dual-rotor system bearing pedestal looseness fault dynamic model considering gyroscopic moments is developed. The Newmark-β method is used to solve the developed model. The dynamic response characteristics of the dual-rotor system when the bearing pedestal is loosened are analyzed. A dual-rotor fault simulation test bench is built to carry out bearing pedestal looseness fault simulation experiments. The comparative results show that the fault frequency distribution pattern in the simulation analysis envelope spectrum is consistent with the experimental results, which proves the validity of the proposed dynamics model. It is found that there is clippings in the rotor vibration signal when there is a bearing pedestal early looseness fault in the dual-rotor system. In the envelope spectrum there are high and low pressure rotor rotation frequency, the sum of frequencies and 2-fold the characteristic frequency of rotor rotation frequency. With the increase of rotational speed ratio, the amplitude of envelope spectrum characteristic frequency increases. When the bearing pedestal is loose, the loose rotor axis trajectory is elliptical-like, and the rotor axis trajectory has a tendency to be more chaotic. Capturing the vibration signal characteristics of a dual-rotor system at very small loosening angles is necessary for preventing larger looseness, which is crucial for fault prediction.

This manuscript is devoted to presenting a new approximate method to solve two-dimensional (2D) fractional optimal control problems, which include Caputo and Atangana–Riemann–Liouville fractal (ARL-F) fractional derivatives. Due to our purpose, we design a numerical algorithm based on the generalized Lucas wavelets (GLWs) and the least squares and collocation methods. GLWs are good choices in this scheme because they have two more parameters (α and β), compared with some existing classical wavelets. On the other hand, we have various types of wavelets (orthogonal and non-orthogonal) by selecting different parameters α and β. According to the impressive feature of the GLWs, we derive Caputo and ARL-F fractional derivative pseudo-operational matrices for the generalized Lucas polynomials and then, for GLWs. The combination of Caputo and ARL-F pseudo-operational matrices with the least squares and collocation methods makes that the considered problems lead to systems of algebraic equations. A brief discussion of the error estimation is investigated. We provide some numerical examples to demonstrate the validity, effectiveness, and applicability of the suggested technique. The proposed algorithm is easy to implement and presents accurate results.

A laminated permanent magnet array eddy current damper (LPMAECD) is proposed to achieve excellent performance for large-scale precision micro-vibration isolation. It improves the damping coefficient by perpendicular magnetized permanent magnet arrays (PMPMA) and laminar arrangement. The PMPMA forms a magnetic field with unilateral characteristics that increase the air gap magnetic flux density and decrease the magnetic flux density near the yoke, thus achieving a high damping coefficient and a low magnetic leakage. Furthermore, the laminar arrangement increases the damping coefficient further and linearly. The theoretical model of LPMAECD is established and validated, and the effect of its geometrical parameters is analyzed. Experimental results show that the damping ratio of the vibration isolation system is raised from 0.12 to 0.32 by LPMAECD, and the peak transmissibility is attenuated by 66%, with the isolation level improved from VC-D to VC-E. It provides an effective method for solving the weak throttling damping of large-scale precision micro-vibration isolation.

This article addresses the optimization of a Vehicle Active Suspension System (VASS) through the application of a Linear Quadratic Regulator (LQR) controller. The primary objective is to enhance ride comfort and ensure vehicle stability by addressing the divergent needs of vibration control. The research identifies key issues in existing optimization algorithms, namely, the exploration stage inefficiency in Big Bang Big Crunch Optimization (B³C) and the slow convergence rate in Coyote Optimization (CO). To overcome these challenges, a novel hybrid algorithm, Hybrid Coyote optimization based Big Bang Big Crunch (HB³C), is proposed. The research objective is to optimize the LQR weighting matrices using the HB³C algorithm, aiming for improved ride comfort and vehicle safety. The problem statement involves the inadequacies of existing algorithms in addressing the exploration and convergence issues. The motivation lies in enhancing the efficiency of VASS through optimal control, leading to better ride comfort and safety. The methodology involves integrating CO within a loop with B³C to compute the optimum reduction rate for the algorithm. Since, B³C algorithm’s success is highly dependent on selecting the ideal reduction rate. This hybrid approach is then applied to optimize the existing LQR weighting matrices. The results are evaluated in terms of time domain and frequency domain response analysis, with a focus on ride comfort based on ISO 2631-1 standards. The study demonstrates a maximum reduction of approximately 74% achieved by the optimized HB³C-LQR controllers.

This paper presents an exact H _∞ tuning methodology for a positive position feedback (PPF) controller applied to a single-degree-of-freedom (SDOF) system. To this end, an equivalence between the closed-loop receptances of a PPF controller and a resistive–inductive shunt with a negative capacitance is put forward, which, in turn, enables us to adopt the existing shunt tuning rule in the active control case. The resulting tuning procedure is demonstrated using two numerical examples, namely, an SDOF system and a finite element model of a cantilever beam. Based on the results obtained on the cantilever beam, it is shown that the influence of higher-frequency modes cannot be neglected to obtain effective vibration damping. The design procedure proposed for the PPF controller is then extended to this case and validated using an experimental cantilever beam.

Motion planning is an effective tool for the suppression of residual oscillation in underactuated mechanical systems, and in particular, model-based method can be used to virtually eliminate any unwanted oscillation after the completion of a motion task. Here, a novel motion planning method, aimed at maximizing robustness to model uncertainties and based on a direct formulation, is proposed and tested. The choice of a direct formulation is aimed at overcoming the numerical problems often encountered when dealing with indirect trajectory planning methods, including the limited robustness to any model-plant mismatch. The proposed direct method is based on three different motion profiles, and is tested for the rest-to-rest motion of a slender beam, with and without parametric robustness constraints, but the same framework can be adapted to countless other situations and formulations. The experimental results showcase good accuracy and a sensible improvement in mitigating the effects of unmodeled perturbations on the system sported by the proposed robustified method over its non-robust counterpart. Experimental results show also the outcome is very similar to the one resulting from a more numerically challenging solution formulated as an indirect problem by means of a two-point boundary value problem.

In the realm of large-scale systems, the complexity of controller design has long been exacerbated by the proliferation of decision variables and inherent conservatism. This study introduces a novel approach to address these challenges, presenting a new distributed robust controller design methodology tailored for large-scale systems grappling with disturbances, uncertainties, and actuator saturations. The primary objectives include reducing conservatism, minimizing decision variables, and significantly curtailing computation time. To surmount these hurdles, the research leverages descriptive and reciprocally convex methods, formulating the design procedure using linear matrix inequalities. This enables the adjustment of uncertain parameters and robust disturbance rejection, thereby ensuring stability in large-scale systems. Additionally, a feedback control law is proposed to accommodate saturation constraints and ensure the closed-loop system’s stability. Notably, the effectiveness of the proposed control scheme is demonstrated through the evaluation of a full-car active suspension system, which is partitioned into interconnected subsystems to a large-scale system. Comparative analyses underscore the superior performance and technical advancements offered by the proposed methodology over existing approaches.

One of the main applications of shape memory alloy (SMA) concerns vibration control, especially superelastic SMA (SMA-SE), which presents a significant stress hysteresis and can work as a damper while adding minimal weight to the structure. In helicopters, vibration is a phenomenon inherent to their operation, and although cannot be eliminated, must be minimized to acceptable levels of safety and comfort. In this context, this paper aims to present the design, testing, and dynamic behavior of a new device entitled smart pitch link, a device with superelastic material for passive vibration control. The paper depicts the design process, assembly, and device testing using a whirl tower that simulates a helicopter rotor in hover. The approach adopts a comparative analysis of the dynamic response on the prototype in reference condition, with a stiff pitch link, with the modified prototype, and with the superelastic pitch link installation. In addition, beyond hover tests, cyclic commands and an asymmetrical lateral gust were employed to observe the output response of the device under transient loadings. Contrary to the literature data about the low time response of SMA, the device presents satisfactory time response and attenuation in frequencies close to main rotor frequencies, with signal attenuations between 2 to 4 dB without any external energy consumption, which, in a comparative analysis, may exceed more than 50% of vibrational amplitude attenuation.

Configuration-controllable phononic crystals (CCPCs) have broad application prospects in engineering because of their adjustable vibration-reduction properties. Owing to the complicated constitutive relationship and nonlinear geometric deformation, it is difficult to accurately predict the dynamic characteristics of CCPCs using the finite element method (FEM) or theoretical methods. In this study, we employed a nonlinear autoregressive with exogenous input (NARX) artificial neural network (ANN) to identify the dynamic model of the CCPC under an impact load, using data from over 100 experiments and numerous accumulated samples. The corresponding experimental data for the CCPC were used to train the ANN and determine the rational ANN model. The identification results indicate that appropriate number of neurons and time-delay orders can effectively reduce the identification errors. Compared with the response predicted by the FEM, the identification model can describe the nonlinear characteristics emerging from phononic crystal (PC) experiments more accurately. This study provides an efficient and accurate online identification approach for PC-modeling.

The imbalance in the number of healthy and faulty samples poses a significant hindrance to the successful implementation of multi-bolt looseness monitoring and fault classification in engineering applications. The Synthetic Minority Oversampling Technique (SMOTE) is widely used in addressing data imbalance issues. However, traditional SMOTE methods and their improvements have not taken into account the problem of sensor network signals with multiple paths. In this paper, an improved oversampling technique, namely Gaussian Mixture Model (GMM)-SMOTE, is introduced. The proposed SMOTE method is based on GMM and aims to solve the sample imbalance problem under different bolt states and different sensor paths in sensor networks. The GMM is utilized to cluster the minority classes in multi-bolt looseness data. The assignment of weights to different clusters is based on the clustering density function, which is subsequently followed by oversampling. The KL distance is utilized to screen the SMOTE sample data, which improves the quality of the data by achieving inter-class balance and intra-class balance. To verify the effectiveness of the method, a multi-bolt looseness monitoring procedure is implemented. The experimental results demonstrate that the proposed method can improve the accuracy of diagnosing early-stage bolt looseness.

The analytical–numerical approach has been adopted to investigate the nonlinear planner response of an axially accelerating beam with the coexistence of additive-type combination parametric resonance and internal resonance. This study includes geometric nonlinearity developed due to the stretching of the neutral layer, longitudinally varying tension, harmonically fluctuating speed, material, and modal dampings. For the suitable value of the system parameters, the second natural frequency of the moving system is approximately equal to three times of first mode, consequently, three-to-one internal resonance activates for a specific range of mean axial speed. The perturbation method of multiple time scales is adopted to solve the beams governing integro-partial differential equation motion with associated end conditions, resulting in complex variable modulation equations that control amplitude and phase modulation. The continuation algorithm technique is used to compute these modulation equations to study the impact of various control parameters, such as internal frequency detuning parameter, variable speed, pulley stiffness parameter, and axial stiffness through the frequency and amplitude response curves. Trivial state stability plots are also presented to illustrate the impact of material and external dampings on the stability of the system. The findings of this analysis are unique and still need to be addressed in the literature.

Resonance can enhance energy conversion and transmission efficiency in mechanical systems. However, maintaining effective resonant behavior by tracking the resonant frequency can be challenging due to load fluctuations. This study introduces a software-based phase-locked loop (SPLL) control method for three-degree-of-freedom acoustic resonant systems (3DOFARS). Initially, the dynamic equation governing the behavior of 3DOFARS is provided, followed by a frequency domain analysis based on the amplitude-phase frequency characteristic curve. Subsequently, the SPLL control method is developed by considering the phase relationship between the system’s excitation signal and response signal, and a control model is then established using Simulink. For the step, slope, and sinusoidal disturbances with specific amplitude and frequency variations, the SPLL control method can track the excitation frequency to the resonant frequency in real time. Among these disturbances, step disturbances pose a greater risk of system instability compared to slope and sinusoidal disturbances. Finally, simulation verification and statistical analysis are carried out by introducing quality interferences of varying types, amplitudes, and frequencies to assess the SPLL control method’s impact on different interferences. Under stable conditions, the SPLL method has better control capabilities against low-frequency interference and better robustness against high-frequency interference. In comparison to conventional methods, the SPLL control method effectively maintains real-time tracking of the excitation frequency to the resonant frequency while upholding process flow integrity.

In this work, a novel meandered 6DoF stepped beam energy harvester that can operate over a broad frequency range is proposed. The hybrid structure has regular beams and zigzag sections that promote greater deformation and bending. The reduced width section in the middle of the beam maintains a low resonance bending frequency and creates a concentrated stress structure. The placement of the piezoelectric layer in this region results in a high-power density. It is found to be a favorable structure to develop using standard microfabrication techniques compared to other broadband harvesters. Also, it can withstand higher mechanical stress and deformation. The proposed structure exhibits wide band characteristics at low frequency and generates higher power output against an array of cantilevers for a given area. The numerical analysis was carried out to select the optimal proof mass that would result in resonance frequencies closely spaced together and yield high output power. Experimental validation on a prototype subsequently confirms the accuracy of the frequency response predicted by the models. When tested under harmonic base excitation of 0.35 g, the harvester generates an average DC power of 374 μ W including signal conditioning losses in the frequency range of 12–27 Hz. The proposed structure offers excellent design flexibility to adjust resonant frequencies by varying the number of beams, the shape of the stepped section, and the proof mass of individual beams. Thus, it has the potential to generate sufficient power output from wideband, low frequency, and low amplitude vibration sources and can be easily optimized for a specific application.

A vibration isolator for a floating slab track, based on a locally resonant phononic crystal, has been designed to suppress vibrations caused by the wheel-rail interaction. In this isolator, a circular vibrator is connected to a connector through a rubber layer uniformly embedded in holes. The finite element method is utilized to compute the energy band structure and transmission loss of the vibration isolator, while the mechanism of bandgap is elucidated through the analysis of modes. The static stiffness and dynamic stiffness of the vibration isolator are calculated, which proves that the vibration isolator meets the requirements of engineering applications. The influence of the number of circular holes and the geometric parameters of the vibration isolator on the bandgap is examined. It is discovered that augmenting the number of holes and the hole diameter in the rubber layer leads to a decreased bandgap. A low-frequency locally resonant bandgap of 38.2–97.1 Hz and a relative bandgap bandwidth of 86.9 % are obtained by optimizing the vibration isolator. The vibration isolation performance of a floating slab track equipped with vibration isolators is analyzed and more robust vibration attenuation performance is obtained in the bandgap. The multi-hole phononic crystal vibration isolator is employed in floating slab tracks for rail transportation, effectively mitigating vibrations transmitted to tunnels, thus further minimizing the effects on the surrounding environment.

High-temperature superconducting (HTS) pinning maglev systems have emerged as promising solutions for high-speed transit, offering self-stability, simplicity, and reliability. These systems utilize the pinning effect between superconducting bulks beneath the vehicle and a permanent magnet guideway (PMG) to achieve levitation and guidance, with propulsion provided by a linear motor. However, the train is subjected to random excitations due to geometric and magnetic field irregularities of the PMG. While much of the existing research has concentrated on mitigating car body vibration for enhanced ride comfort, the issues related to frame vibration and the maintenance of consistent linear motor air gaps are still not fully addressed. This study introduces a secondary semi-active suspension device aimed at attenuating frame vibration in the HTS pinning maglev system. The research initially establishes a vehicle model based on an existing HTS pinning maglev test line and obtains track irregularity time-domain samples using the power spectral density (PSD) function. Classic semi-active control algorithms and the electromagnetic shunt damper (EMSD), enabling the implementation of semi-active control strategies, are then introduced. Subsequently, employing the groundhook linear (GH linear) control strategy, a vibration suppression model for the frame is established using the UM/Simulink co-simulation method. Finally, a comparison is made between the passive suspension system and the semi-active suspension system, with the Sperling index calculated to evaluate performance. The results affirm that this secondary semi-active suspension device not only significantly reduces frame vibration but also complies with ride comfort requirements, offering practical insights for future engineering applications.

A passive vibration absorber is proposed to mitigate tremors induced by Parkinson’s disease or essential tremor to replace costly and invasive alternatives. The proposed device is a wristband that, instead of classic spring–damper pairs, incorporates a shape memory alloy spring that acts as a nonlinear energy sink due to its hysteretic behavior. The mathematical models for the SMA spring and the patient’s forearm and hand are developed. To demonstrate the superiority of the SMA absorber, the proposed absorber’s performance is compared to a classic viscous absorber and also tested under unexpected harmonic forces. The simulations were performed in two parts. The first part used harmonic excitations as tremors to optimize SMA and viscous absorbers. The results indicated a 91% and 92% reduction in forearm and wrist tremors by the SMA absorber. The second part used real-world tremor data to compare the absorbers. Simulation results indicated that the viscous absorber reduces tremor power to an average of 55% in the 3–25 Hz range. In comparison, the SMA absorber has an average 92% tremor PSD reduction in the said range, which is significantly higher than the viscous absorber.

This research article investigates the attenuation patterns of acoustic waves within waveguide structures featuring flexural boundaries. By employing advanced methods in vibrations and controls, the study aims to enhance our understanding of waveguide behavior and offer valuable insights for optimizing acoustic wave propagation in diverse applications. The entire waveguide structure is tuned through cooperative interactions involving elastic plates, membranes, and rigid boundary surfaces. The lower boundary of the expansion chamber consists of a rigid plate, with elastic membranes covering the upper surfaces of the cavity. The problem is formulated in terms of transmission and reflection coefficients of the modes, enabling the solution of the scattering problem. Matching acoustic pressure and velocity at the waveguide junction yields the scattering coefficients. The results reveal that the scattering coefficients are intricately influenced by both the geometric characteristics of the waveguide and the frequency of the incident waves. Notably, the first higher-order mode of the cut-off frequency of the waveguide structure corresponds to the frequency at which the dissipation coefficient reaches its maximum value. This research provides valuable insights into the scattering behavior of acoustic waves in waveguide configurations, contributing to the design of acoustic devices and systems. Rigorous support and justification for all aspects of the mode-matching method, including pressure and velocity matching, eigen properties, physical edge conditions, convergence criteria, and energy conservation, are provided through thorough algebraic and numerical analyses, confirming the validity of the solution methodology.

As a novel type of non-mechanical contact rail transit, the maglev vehicle is stabilized by actively controlled levitation forces without contact. The steel bridge exhibits complex self-vibration characteristics with dense high-frequency vibration modes. The levitation gap and force are disturbed by the complex vehicle-induced deformation of the steel bridge, and significant moving maglev vehicle–steel bridge coupled vibration phenomena occur. To solve this problem, the vibration mechanism of a maglev vehicle moving on a steel bridge should be understood. This paper establishes detailed models of the theoretical dynamic interactions between a moving maglev vehicle and double-span steel and steel–concrete composite continuous bridges with active levitation control. The vehicle-induced vibration characteristics of the two bridges and the vehicle dynamic responses were compared, and the influence mechanism of the steel bridge on the maglev vehicle’s operation stability was examined. The influences of different high-order modes and modal stiffnesses on the coupled system’s dynamic performance were analyzed. The results demonstrated that the numerous high-order local vibration modes present in the steel top slab were responsible for the maglev vehicle’s smooth operation. High-order local vibration modes and short wavelengths were prone to the large fluctuations in the levitation gap and force. The greater the modal stiffness for a given local vibration mode was, the lower the vehicle-induced deformation became. Minimizing local high-frequency vibration modes of the steel top slab and increasing the local vibration mode stiffness could effectively reduce the excitations to the levitation control system.

Joints are effective in absorbing the ground impact and isolating the vibrations caused by the impact when goats jump over the cliff to find food. A bionic vibration isolator for low-frequency vibration inspired by the goat hind limb joint is proposed. The quadrilateral mechanism of the bionic vibration isolator of varying sizes is used to mimic the vibration suppression effect of multiple joints in the hind limbs of goats. The rigid rods in the bionic mechanism are used to mimic the role of the bones in the joint, and the springs are used to mimic the function of the muscles or tendons near the joint. In addition, the slider mechanism of the bionic mechanism brings nonlinear damping and mass, which could effectively help the system to reduce the resonant frequency and enhance the vibration isolation performance. The natural frequency of the bionic mechanism is 1.2 Hz, while the natural frequency of the linear mechanism under the same conditions is 5.1 Hz. When the external vibration exceeds 2.4 Hz, the proposed bionic mechanism begins to perform vibration isolation performance. Compared with the linear vibration isolation device, the bionic mechanism has lower natural frequency, better vibration isolation performance, and wider vibration isolation frequency band. Therefore, this study creatively proposed a vibration control mechanism inspired by animal limbs and proposed a high-stability and low-cost bionic structures in the field of vibration control.

This paper presents a new nonlinear dynamic model and analysis of a viscoelastic beam mounted on viscoelastic supports and excited by a reciprocating moving load. The equation of motion is derived by the extended Hamilton’s principle and solved utilizing the harmonic balance method. The nonlinear frequency response and force transmissibility characteristics for various loads and boundary conditions are demonstrated. Parametric analysis is performed to explore the influence of several nondimensional quantities on the frequency response and transmissibility. The effect of rigid–flexural motion interactions on the nonlinear dynamic behavior of the system is investigated. Moreover, the effects of the supports’ stiffness symmetry and magnitudes on the nonlinear response and force transmissibility characteristics are thoroughly examined. The influence of internal damping is found to be minimal for low support stiffness, whereas a significant effect is observed for high support stiffness.

This paper considers the modeling and control of the rigid–flexible satellite in large-range planar motion. Employing Hamilton’s principle, a novel modeling of planar motion is obtained to describe the relationship between vibration and planar motion. Furthermore, nonlinear terms in the vibration dynamics are analyzed, and the influence of rotation on the stiffness of the flexible appendage is discussed through numerical computation and theoretical deduction. We proposed the all-modal control method to control the vibration completely, and real vibration control load is synthesized with all-modal controllers. Eventually, numerical simulations are presented to validate the effectiveness of the controller in planar motion.

This paper proposes an adaptive feature extraction method based on mathematical morphology enhancement to extract effective and stable features under strong ocean noise. Firstly, the traditional mathematical morphology method is improved and a new mathematical morphology filtering method is proposed for feature enhancement of underwater target signals. Secondly, the artificial fish swarm algorithm (AFSA) is improved using weighted power spectral kurtosis (WPSK) to achieve parameter adaptivity. Five measured underwater target signals are used to validate the extracted method, and cosine similarity (CS), signal to noise ratio (SNR), and refined composite multiscale fluctuation dispersion entropy (RCMFDE) are used as evaluation metrics to assess the results and verify the effectiveness of the proposed method. Compared with average filtering (AVGF) and closing opening filtering (COF), the proposed method shows better capability in adaptive feature extraction. Therefore, the proposed mathematical morphological filtering can enhance underwater target features and is very important for adaptive feature extraction of underwater targets.

In this paper, transient response of commensurate fractional-order systems with non-zero initial conditions is investigated in the viewpoint of the existence of deviation from initial condition. In particular, firstly peak effect for a class of linear fractional order systems is inspected by presenting a lower bound for their responses. Such a lower bound is described by an elementary function, where the commensurate order of the system is considered as a rational number. Furthermore, it has been demonstrated that under particular circumstances the derived lower bound can be extended to apply for deviation analysis in response of a class of fractional-order nonlinear systems. Moreover, included are various illustrative examples intended to assess the applicability of the obtained lower bound in prediction of the deviation value and the time instance at which the peak effect occurs.

A novel iterative model updating method is developed to identify the local nonlinear joint properties using the frequency response functions (FRFs) of assembled structures. In this paper, the least-squares fitting method was used to transform the sensitivity matrix into a square iteration matrix to match the dimensions of the objective functions and nonlinear joint model parameters. Leveraging the Newton’s iteration, the adaptive successive over-relaxation (A-SOR) was used to ensure iteration convergence while the multi-scale parameter adjusting (MPA) strategy was developed to degrade the ill-condition of the iteration matrix. Two updating examples of phenomenological equivalence models were applied to demonstrate the effectiveness of the proposed method. The nonlinear FRFs of a lap-type bolted joint beam system with Iwan model were simulated as the objective functions to identify the local nonlinear joint properties, as well as experimental investigations of a metal rubber isolation system with a high-order polynomial model. The proposed method was validated by the good agreement of the comparison results, and it indicated a better model updating performance with a much smaller condition number of the iteration matrix.

This paper investigates the vibration behavior of a 10-story benchmark building controlled with an active tuned mass damper (ATMD) under earthquake loads. An ATMD, typically installed on the top floor, is a modified form of a tuned mass damper (TMD) that includes a mass, spring, damper, and an actuator enhancing system performance and structural damping. The force and movement direction of the ATMD are controlled by a processor and actuator. In the ATMD system, control algorithms determine the magnitude and direction of the applied force. This research introduces a new control algorithm based on the structure’s dynamic response and ATMD stiffness. To evaluate the performance of this algorithm, linear–quadratic regulator (LQR) and fuzzy logic controller (FLC) algorithms were designed and presented for comparison. The results indicate that the proposed algorithm outperformed the other algorithms, reducing the structure’s displacement and acceleration responses by an average of 40% and 28.16%, respectively, compared to the uncontrolled state.

Aiming at the problem of the control performance degradation of a permanent magnet synchronous motor (PMSM) drive system due to permanent magnet demagnetization, which is caused by mechanical vibration and high temperature, this paper presents an equivalent-input-disturbance (EID) fault-tolerant control method based on an integral sliding-mode observer (ISMO). The mathematical model of a PMSM with demagnetization fault in dq-axis coordinate system is first established. Then, the model is transformed into an EID system one. An ISMO is used to estimate the state variables of the EID system and an equivalent-input-demagnetization fault. The estimate of the equivalent-input-demagnetization fault is compensated in a feed-forward manner. Thus, the fault-tolerance control of PMSM demagnetization is achieved. Finally, the stability analyses of the ISMO and the entire EID system are given. The comparative results of a hardware-in-the-loop experiment show that the designed method effectively improves the fault-tolerant control performance of a PMSM drive system with demagnetization fault.

Morphing structures are re-configurable structures that can change its geometry to perform multiple functions in multiple operating conditions. Morphing beam structures have considerable applications in industrial robots, morphing aircraft, deployable space structures, etc. In this study, dynamic modelling and analysis of a telescopic type morphing beam, modelled as moving load problem with inertia effects, is performed. The moving loads are assumed to travel along the length of the beam, from fixed to free end and free to fixed end. The material and geometric parameters of the beam are assumed to be constant. The Rayleigh beam theory is used to model the beam, taking into account the rotating inertia effects. Dirac Delta function is used to model the moving loads in the governing equation. A hybrid analytical and numerical approach that couples eigenfunction expansions and Laplace transformation, along with the Crank–Nicholson numerical scheme, is developed to solve the coupled differential equations. The number of oscillations per unit travel time of the moving load and the Dynamic Amplification Factor (DAF) of the beam’s tip response are used to quantify the dynamic effects. Numerical results are investigated for the various non-dimensionalized speeds defined in terms of the moving loads’ critical speed. Numerical result shows that loads moving at low speeds have a more pronounced impact on the dynamic response compared to high speeds. Moving moment induces significant oscillatory behaviour for both (Fixed-free and Free-fixed) boundary conditions. In contrast, the moving mass induces oscillation only when it travels from free-end to fixed-end.

In the field of intelligent machinery fault diagnosis, overcoming challenges arising from scarce labeled data and the demand for deployment on resource-constrained edge devices is imperative. To address these hurdles, this work aims to improve the ability of deep learning models to learn strong feature representations from limited data, while also reducing the model complexity. We presenting a novel network named TEdgeNeXt, the approach begins with a new signal-to-image conversion method, which is proved to be able to acquire less training data quantity. Structurally, the Convolutional (Conv.) Encoder initially is employed with depth-wise separable convolution to control the size of model rather than the traditional convolution, and the Split Depth-wise Transpose Attention (SDTA) encoder is consequently utilized by leveraging a multidimensional processing approach and the Multi-head Self-Attention which is across the channel dimensions instead of the spatial channel. By doing so, it effectively handles challenges such as high multiply-additions (MAdds) and increased latency through Flops and params. On the other hand, the fine-tune-based transfer learning technique is able to be extended in our approach for improving the capacity of generalizing. Ultimately, it indicates the noticeable improvements in Top-1 Accuracy (T1A), Mean Precision (MP), Mean Recall (MR), and Mean F1 score (MF1) across three distinct datasets.

This paper explores the qualitative behavior of a discrete fractional–order Brusselator model. We analyze the local dynamics of the model around its fixed point and determine its topological classification. We perform the bifurcation analysis for both codimension-one and codimension-two cases to examine the system behavior near critical parameter values. Using normal form theory and center manifold theorem (CMT), we prove that the model exhibits period-doubling bifurcation around its interior fixed point. We also study the existence and direction of Neimark–Sacker bifurcation using normal form theory. For codimension-two bifurcation, we show that the model undergoes 1:2, 1:3, and 1:4 resonances by applying normal form theory and suitable affine transformations. The system displays a rich variety of bifurcations, including quasi–periodicity, periodic orbits, chaotic behavior, and resonance bifurcation. Furthermore, the existence of chaos is discussed in the sense of Marotto, and a novel chaos control method is proposed for discrete Brusselator model using an extended pole–placement approach. This modified approach is more suitable for codimension-two bifurcation situations. Numerical simulations are used to illustrate the theoretical discussion.