Abstract:This paper proposes a combined dynamic vibration absorber and establishes a coupled dynamic model of an elastic simply-supported beam equipped with a dynamic vibration absorber. Using the modal superposition method, analytical expressions for the amplitude-frequency response of different vibration modes are derived. Focusing on the first-order mode of the elastic beam, analytical solutions for the optimal tuning ratio, optimal stiffness ratio, and optimal damping ratio are obtained based on the H∞ optimization criterion and fixed-point theory, along with the corresponding optimal operating range of the inerter . The validity of the derived design formulas is further verified through the finite difference method. The results indicate that connecting the inerter between the primary and secondary systems does not enhance the vibration reduction performance. In addition, the proposed dynamic vibration absorber demonstrates exhibits excellent vibration suppression capability for the first-order mode of the elastic beam and effectively broadens the vibration absorption frequency band.

Abstract:Quasi-zero stiffness (QZS) isolators have been widely studied owing to their superior low-frequency vibration isolation performance. However, the heavy damping in prototypes will lead to no relative motions between the isolated mass and the excitation at low frequencies, thus the vibration isolation is of failure at low frequencies. To address this limitation, compression springs are replaced with tension springs to reduce system damping in the prototype. These tension springs are configured to form both positive and negative stiffness structures arranged in parallel, thereby enabling the design of a QZS isolator utilizing exclusively tension springs. The QZS condition is derived from the static analysis, and the influence of key parameters on QZS features is analyzed. Wide QZS ranges around the static equilibrium position can be achieved. For dynamic analysis, the harmonic balance method is employed to validate the displacement transmissibility results calculated by the incremental harmonic balance method combined with a continuation algorithm. Theoretical predictions calculated by both methods demonstrate close agreement within the effective isolation frequency band. Finally, a prototype had been designed, fabricated and dynamically tested. Meanwhile, a corresponding simulation model was analyzed using ADAMS. Both the tested and simulated displacement transmissibilityexhibit strong consistency with theoretical predictions. The findings demonstrate that the proposed QZS isolator achieves the initial frequency of 1.5 Hz for vibration isolation and the corresponding linear isolator without negative stiffness is 6 Hz. The results verify the superior performance of the vibration isolation of the QZS isolator based on the parallel mechanism of the positive and negative stiffness structures constructed by tension springs.

Abstract:This paper investigates the problem of adaptive fuzzy periodic event-triggered control for output-feedback interconnected switched nonlinear systems under arbitrary switching. Fuzzy logic systems are employed to approximate the unknown nonlinear terms. A state observer and fuzzy adaptive laws are constructed by using only the sampled output information. To reduce the waste of communication results, a novel controller is developed that only uses the information at the event-triggered instants. Furthermore, the proposed discrete-time event-triggering mechanism performs intermittent monitoring at the sampling instants. It is finally proven that all states of the closed-loop system remain bounded under arbitrary switching, and the effectiveness of the proposed scheme is verified through simulation results.

Abstract:Based on the Linyi Yellow River Bridge in Shanxi Province, experiments and computational fluid dynamics (CFD) numerical simulations were conducted to study the mechanism of vortex induced vibration (VIV) and aerodynamic countermeasures (AC) for a steel box- concrete composite girder with sound barriers. Firstly, wind tunnel tests were conducted on the original design scheme of the girder section using a segment model with a geometric scale ratio of 1:60. Then, experimental studies were conducted to investigate the influence of the installation position of horizontal guide plates on the VIV control performance, including installing 2.0 m-wide horizontal guide plates on both webs of the steel box–concrete composite girder at a height of 2.6 m above the bottom plate (AC-1), as well as installing 2.0 m-wide horizontal guide plates at the ends of the flange plates (AC-2) . Finally, CFD simulations were performed to analyze the vortex-induced vibration and control mechanism of the original design scheme of the steel box-concrete composite girder section with/without AC-1 and AC-2, respectively, based on flow field characteristics. The results show that the original design scheme of the steel box-concrete girder section exhibits both vertical and torsional VIV at 0 ° and+3 ° angles of attack, and the maximum amplitude exceeds code-specified limits. After adopting the aerodynamic control measure AC-1 on both sides of the steel box-concrete composite girder at a height of 2.6 m above the bottom plate, the torsional VIV response of the girder section is eliminated, while the vertical VIV amplitude slightly increases. Furthermore, after adopting the aerodynamic control measure AC-2, the VIV amplitude of the girder section was effectively suppressed, and the torsional VIV of the girder disappeared. Moreover, the mechanism of VIV and aerodynamic control of the steel box-concrete girder section with sound barriers can be summarized as follows: the airflow passing over the girder section induces alternately shedding vortices on the downstream side, which leads to vortex-induced vibration. The vortex intensity shows no significant reduction after adopting the aerodynamic control measure AC-1, while the vortex intensity is weakened to to a certain extent after adopting the aerodynamic control measure AC-2, whichc ontributes to the effective suppression of the VIV response of the girder section.

Abstract:To solve the problem of large volume and storage difficulty of bridge health monitoring data, the deep convolutional autoencoder is proposed to compress data. By designing a damage indicator, structural damage location is identified from the compressed data, thereby ensuring the effectiveness of the data compression. Firstly, an appropriate deep convolutional autoencoder model is designed, and the autocorrelation functions of acceleration responses under the healthy state of the bridge are used as training data to obtain appropriate model parameters. Secondly, the real-time monitored acceleration autocorrelation functions are input into the trained deep convolutional autoencoder model to obtain compressed data. Then, the Euclidean distance between the compressed data under both healthy and real-time states is calculated as a damage indicator, with each damage indicator corresponding to a specific structural location. Next, the damage condition at the corresponding location is determined according to whether the indicator changes. Finally, numerical models of a simply supported beam and a continuous beam, as well as a simply supported beam test in laboratory, are adopted to verify the effectiveness and noise robustnessof the proposed method.

Abstract:Spacecraft micro-vibrations, characterized by multiple excitation sources, broadband frequency, and complex transmission, challenge conventional suppression methods and threaten mission reliability. To address the trade-off between lightweight design and vibration mitigation in passive damping structures, this paper proposes a topology optimization design methodology for maximizing the modal damping ratio of a free-layer damping structure. Utilizing the variable density method, the optimization model is established with sensitivity and density filtering techniques to achieve optimal material distribution under multi-modal targets. Case studies on two-end fixed and cantilever plates demonstrate that the optimized layouts enhance target modal damping ratios and reduce vibration transmissibility peaks.

Abstract:The Z-Tilt-Torsion (ZTT) precision motion platform is a core component of semiconductor inspection equipment, and its control performance directly affects the yield of semiconductor inspection. Due to the fact that the ZTT precision motion platform is a multi-axis motion platform composed of flexible hinge guides, the nonlinearity and disturbance problems inherent in the system pose challenges to the design of controllers. Therefore, the research on the controller for the ZTT precision motion platform is very important. Currently, the existing controllers mainly include Proportional-Integral-Derivative (PID) control, sliding mode control, and H∞ controller. Among them, when the system is subject to strong external disturbances, the performance of the PID controller will decline, which may even lead to system instability. Although the sliding mode controller can solve the problem of external disturbances, its switching characteristics make it very sensitive to high-frequency noise and measurement errors, which may amplify these disturbances and make it difficult to implement in practical applications. To solve the above problems, this paper adopts the H∞ control method and designs an H∞ controller to make the closed-loop function of the system meet certain H∞ norm constraints, thereby ensuring the stability and performance of the system. Through experimental methods, the effects of PID control and H∞ control were compared. The results show a good suppression effect on external disturbances and could effectively suppress the fluctuations of the motion platform caused by disturbances.

Abstract:Inertial devices can convert linear motion into high-speed rotation to amplify the physical mass of the system. Combining a conventional tuned mass damper (TMD) with an inertial device results in a tuned inertial mass damper (TMDI). Previous studies by many scholars have shown that the TMDI system has certain advantages in controlling the vibration response of structures. In order to make the TMDI system fully exploit its vibration reduction potential, this paper proposes an accurate optimal parameter design formula for the single-degree-of-freedom TMDI system under harmonic load excitation. In order to verify the effectiveness of the optimal parameter design formula, a comparative study with the traditional tuned mass damper (TMD) was also carried out. The results show that when a single-degree-of-freedom structure is subjected to random seismic excitation, the parameters obtained by the TMDI optimal parameter design method proposed in this paper can effectively realize the vibration reduction potential of TMDI. When the traditional tuned mass damper (TMD) is used to control the vibration response of structures under non-stationary random seismic excitation, its vibration reduction effect is not ideal, but after the TMDI system is set with the optimal parameters, it can achieve the expected vibration reduction performance.

Abstract:Permanent Magnet Synchronous Motor (PMSM), owing to their high energy efficiency and structural advantages, has been widely adopted in high-performance motion control applications such as rail transit systems. However, chaotic behaviors inherent in PMSM systems can lead to operational instability, necessitating highly effective control strategies. This paper proposes a dual-parameter cooperative control strategy—referred to as GWO-Volterra—based on the integration of Grey Wolf Optimization (GWO) and the Volterra series, aiming to achieve precise control of chaotic motions in PMSMs. In this strategy, the distance between two adjacent projection points on the Poincaré section is selected as the control input. Furthermore, the complex coupling effects of system parameters on dynamic behavior are thoroughly considered by constructing a dual-parameter controller within the Volterra series framework. To enhance control performance, the GWO algorithm is introduced to optimize and adaptively adjust key parameters. Simulation results demonstrate that, compared with single-parameter control strategies, the proposed GWO-Volterra approach exhibits superior performance in terms of faster response, reduced overshoot, and enhanced control stability, thereby validating its effectiveness and practical applicability.