国际机械系统动力学学报(英文)最新文献

To enable message transmission among sensors and equipment, power line communication (PLC) is a widely adopted smart grid. However, due to the occurrence of impulsive noise (IN), reliable transmissions over PLC channels in the smart grid are challenging. Therefore, in this paper, we propose an adaptive noise mitigation scheme to clip the IN with the sliding window-based method, where the altitude of the received signal in the current time slots is obtained by computing the average altitude of signals in the previous and next time slots. To detect the states of IN and dynamically estimate the power threshold of signals for the IN mitigation scheme, we develop an intelligent algorithm based on the long short-term memory network. To prevent the useful signals from being eliminated as IN signals, we propose the accelerated proximal gradient method (APGM) based on tone reservation to reduce the peak-to-average power ratio (PAPR) for the transmitting signals with low computational complexity. In addition, the closed-form expression of the bit error rate (BER) is derived for the proposed sliding window-based IN mitigation scheme according to the probability density function of the IN. Simulation results demonstrate that the proposed IN mitigation scheme achieves a better BER performance than the conventional IN mitigation schemes. In addition, the APGM aided by IN mitigation can further improve BER performance due to the PAPR reduction.

Cover Caption: A velocity-based space–time finite element method (v-ST/FEM) is presented for analyzing dynamic soil–structure interaction in earth structures such as dams, tunnels, and embankments subjected to vibrational loading from high-speed trains, road traffic, underground explosions, and earthquakes. The method incorporates the Lysmer–Kuhlemeyer viscous boundary conditions to truncate the unbounded soil domain and includes time-dependent boundary conditions to model energy flow. The v-ST/FEM is third-order accurate in time. It introduces negligible numerical dispersion error, thus enabling precise computation of the dynamic responses of soils and structures during long-duration earthquake motions.

To improve the dynamic balancing accuracy of the micro-motor rotor, an unbalanced vibration feature extraction based on an all-phase fast Fourier transform (APFFT) method is proposed. The amplitude and phase of the signal are extracted by spectrum analysis after windowing the unbalanced signal. The mathematical model is derived to simulate the weak signal of rotor unbalance. The simulation results show that this method is accurate in extracting the weak signal of the rotor under different noise levels. The micro-motor rotor unbalanced test system is developed for experimental validations. The accuracy and stability of the vibration amplitude and phase extracted by the APFFT are better than the accuracy and stability from the hardware filtering method. The rotor unbalance is reduced by more than 80%. Furthermore, secondary balance of the rotor after the first balance is carried out. The proposed method can still extract the residual unbalance of the rotor. The results demonstrated that the proposed method can achieve a reduction rate of 90% and the accuracy is within 5 mg, verifying the effectiveness of the proposed method for high-precision rotor dynamic balance.

In recent decades, the design of complex systems like launch vehicles in the aerospace industry has presented engineers with challenges that go beyond system complexity. Issues such as time-to-market pressures and intricate industrial processes have underscored the increasing significance of agile design methodologies. Agile design is derived from the simplification of the design process and enhancing cross-domain data transmission and feedback. While methods based on model-based system engineering have improved iteration times in system architecture design, challenges persist in cross-domain data transmission. Due to the diversity of complex system models and data, a single-mode integration method is difficult to realize the data link construction of all tools used. To address this challenge, this paper proposes a dual-mode data integration framework with expansibility, universality, and cost-efficiency which leverages the benefits of Remote Procedure Call and Intermediate Exchange Module, addressing the challenge of constructing cross-domain data links under single-mode integration. In this study, two critical requirements of the first- and second-stage separation systems, namely, weight and minimum separation gap, are selected for data feedback. A Modelica-based multiphysics simulation model is developed in MWorks; visualization and computation of the minimum gap are carried out in CoppeliaSim. To bridge the gap between domain-specific tools, Matlab and Functional Mock-up Unit modules are introduced as middleware, facilitating data feedback linkage. The entire simulation process is orchestrated using activity diagrams in the MagicDraw tool. The study delves into the influence of critical design parameters, such as the initial angular velocity of separation and the thrust of the retro rocket, on the minimum separation gap. It provides an analysis of minimum separation gap variations under uncertain operating conditions and examines design margins. Significantly, the paper highlights the significance of controlling the initial angular velocity during separation and the reliability of the retro rocket, providing essential decision supports and valuable insights to agile the process of system design.

A three-magnet-ring quasi-zero stiffness (QZS-TMR) isolator is designed to solve the problem of low-frequency vibration isolation in the vertical direction of precision equipment. QZS-TMR has both positive and negative stiffness structures. The positive stiffness structure consists of two mutually repelling magnetic rings and the negative stiffness structure consists of two magnetic rings nested within each other. By modulating the relative distance between positive and negative stiffness structures, the isolator can have QZS characteristics. Compared with other QZS isolators, the QZS-TMR is compact and easy to manufacture. In addition, the working load of QZS-TMR can be flexibly adjusted by varying the radial widths of the inner magnetic ring. In this paper, the static analysis of QZS-TMR is carried out to guide the design, and the low-frequency vibration isolation performance is studied. In addition, the experimental prototype of QZS-TMR is designed and manufactured. The static and vibration isolation experiments are carried out on the prototype. The results show that the initial vibration isolation frequency of the experimental prototype is about 4 Hz. The results show an excellent low-frequency vibration isolation effect, which is consistent with the theoretical research. This paper introduces a new approach to the design of the QZS isolator.

In this work, our primary focus centered on exploring the adaptability of the dual-rate sampling scheme proposed earlier to enhance the performance of multi-degree-of-freedom (multi-DOF) impedance-based haptic interfaces. The scheme employed independent sampling rates in a haptics controller, effectively mitigating the issue of reduced Z-width at higher sampling rates. A key aspect of our investigation was the intricate implementation of the dual-rate sampling scheme on a field programmable gate array (FPGA). This implementation on a logic hardware FPGA was challenging and led to the effective comparison of the uniform-rate and dual-rate sampling schemes of the multi-DOF haptic controller. We used an in-house developed two-DOF pantograph as the haptic interface and an FPGA for implementing the controller strategy. FPGA-based implementation presented challenges that were vital in testing controller performances at higher sampling rates. Virtual wall experiments were conducted to determine the stable and unstable interactions with the virtual wall. To complement the experimental results, we simulated the haptics force law for multi-DOF system on Simulink/MATLAB. Notably, the dual-rate sampling approach maintained the Z-width of the two-DOF haptic interface, even at higher controller sampling rates, distinguishing it from the conventional two-DOF uniform-rate control scheme. For example, employing a dual-rate sampling combination of 20–2 kHz consistently ensured the stable rendering of a maximum virtual stiffness of approximately 700 N/mm and maintained a reliable virtual damping range spanning from 0 to 5 Ns/mm. In contrast, the 20 kHz uniform-rate sampling approach failed to ensure interface stability in the presence of virtual damping, ultimately resulting in the unsuccessful implementation of any virtual stiffness at higher sampling rates. This work, therefore, establishes the potential of dual-rate sampling in the realm of haptic technology, with practical applications in multi-DOF systems.

Design of earth structures, such as dams, tunnels, and embankments, against the vibrational loading caused by high-speed trains, road traffic, underground explosions, and, more importantly, earthquake motion, demands solutions of the dynamic soil–structure Interaction (SSI) problem. This paper presents a velocity-based space–time finite element procedure, v-ST/finite element method (FEM), to solve dynamic SSI problems. The main goal of this study is to present the computation details of implementing viscous boundary conditions of Lysmer–Kuhlemeyer to truncate the unbounded soil domain. Furthermore, additional time-dependent boundary conditions, in terms of the free-field response, are included to facilitate energy flow from the far field to the computation domain at the vertical truncated boundaries. In the FEM, seismic input motion is applied to an effective nodal force vector, which can be obtained explicitly in the numerical simulations. Finally, the response of a concrete gravity dam resting on an elastic half-space to the horizontal component of earthquake motion is computed and successfully compared with the results of semidiscrete FEM using the Newmark-$$ method.

This paper presents a novel approach called the boundary integrated neural networks (BINNs) for analyzing acoustic radiation and scattering. The method introduces fundamental solutions of the time-harmonic wave equation to encode the boundary integral equations (BIEs) within the neural networks, replacing the conventional use of the governing equation in physics-informed neural networks (PINNs). This approach offers several advantages. First, the input data for the neural networks in the BINNs only require the coordinates of “boundary” collocation points, making it highly suitable for analyzing acoustic fields in unbounded domains. Second, the loss function of the BINNs is not a composite form and has a fast convergence. Third, the BINNs achieve comparable precision to the PINNs using fewer collocation points and hidden layers/neurons. Finally, the semianalytic characteristic of the BIEs contributes to the higher precision of the BINNs. Numerical examples are presented to demonstrate the performance of the proposed method, and a MATLAB code implementation is provided as supplementary material.

Axle-box bearings are crucial components of high-speed trains and operate in challenging conditions. As service mileage increases, these bearings are susceptible to various failures, posing a safety risk to high-speed train operations. Thus, it is crucial to examine the deployment methods of axle-box bearings. A dynamic model of axle-box bearings for high-speed trains with compound faults is constructed by setting up separate faults in two rows of double-row tapered roller bearings based on a single-fault model. The model's high accuracy in expressing compound faults is verified through corresponding experimental results. Then, the frequency domain diagram of system vibration response under varying rotational speed conditions is obtained, and the amplitude corresponding to the single frequency is extracted and analyzed to identify the optimal rotational speed band for composite fault diagnosis. Finally, the optimal speed band is analyzed under different faults, different load sizes, and different composite fault types. It can be concluded that the determination of the optimal speed band is solely influenced by the composite fault type and is independent of the fault and load sizes. Finally, it is concluded that the energy proportion of faults in different positions changes periodically with the change in speed, and this phenomenon is not affected by the fault sizes or load magnitude.

In this paper, we study the vibrational behavior of shells in the form of truncated cones containing an ideal compressible fluid. The sloshing effect on the free surface of the fluid is neglected. The dynamic behavior of the elastic structure is investigated based on the classical shell theory, the constitutive relations of which represent a system of ordinary differential equations written for new unknowns. Small fluid vibrations are described in terms of acoustic approximation using the wave equation for hydrodynamic pressure written in spherical coordinates. Its transformation into the system of ordinary differential equations is carried out by applying the generalized differential quadrature method. The formulated boundary value problem is solved by Godunov's orthogonal sweep method. Natural frequencies of shell vibrations are calculated using the stepwise procedure and the Muller method. The accuracy and reliability of the obtained results are estimated by making a comparison with the known numerical and analytical solutions. The dependencies of the lowest frequency on the fluid level and cone angle of shells under different combinations of boundary conditions (simply supported, rigidly clamped, and cantilevered shells) have been studied comprehensively. For conical straight and inverted shells, a numerical analysis has been performed to estimate the possibility of finding configurations at which the lowest natural frequencies exceed the corresponding values of the equivalent cylindrical shell.