Search Results (774)

The built-in V-shaped permanent magnet motor can effectively utilize reluctance torque to improve torque density, but there is also a problem of large torque ripple causing high vibration noise. This article proposes a rotor structure with four magnetic isolation holes to reduce torque ripple in V-shaped built-in permanent magnet motors. Firstly, a finite element analysis model of the built-in V-shaped permanent magnet motor is established. The influence of slot width, rotor rib width, and magnetic bridge parameters on the torque of the permanent magnet motor was studied through parameterized scanning, and an optimization scheme was selected. Then, the position and size of the magnetic hole were optimized through an adaptive single-objective algorithm. Compared with the ordinary built-in V-shaped structure, the torque ripple of the built-in V-shaped permanent magnet motor with four magnetic isolation holes is reduced from 17.7% to 6.7%. The proposed internal V-shaped rotor structure with magnetic isolation holes and the optimization method can effectively reduce torque ripple, thus effectively solving the problem of vibration noise caused by torque ripple. Full article

Tubular pump systems (TPSs) represent a critical class of large-scale turbomachinery for low-head water transport, where mechanical reliability is often challenged by complex internal flow dynamics. Pressure pulsations in pump systems induce vibrations that adversely affect performance, emphasizing the need for effective control mechanisms to ensure stable operation. In tubular pumps, unsteady pressure pulsations are typically driven by rotor–stator interactions; however, the behavior of these pulsations in the absence of impeller rotation remains poorly understood. In this study, a novel comparative investigation is conducted to elucidate the effect of impeller rotation on pressure pulsations characteristic by examining two scenarios: normal impeller operation at rated speed and a completely stationary (zero-speed) impeller condition. Experiments were performed on a model low-head tubular pump, measuring dynamic pressures at four key locations across a range of flow rates. Time–frequency analysis using the continuous wavelet transform (CWT) and the wavelet coherence transform (WTC) was applied to delineate the unsteady pressure features. The results demonstrate that under normal rotation, pressure pulsations are dominated by pronounced periodic components at the impeller’s rotational frequency and its harmonics, with the strongest fluctuation amplitudes observed near the impeller outlet region. In contrast, with the impeller held stationary, these distinct periodic peaks vanish, replaced by broadband, irregular fluctuations. Crucially, WTC analysis revealed that significant coherence between the two operational states was confined to low frequencies (≈16.7–50 Hz), particularly at the impeller inlet, highlighting the presence of low-frequency dynamics likely associated with system-scale hydraulic compliance or inlet flow non-uniformity, independent of impeller rotation. These findings confirm the pivotal role of impeller rotation in generating periodic pressure pulsations while providing new insight into the underlying unsteady flow mechanisms in tubular pumps. Full article

This study investigates the mechanical characteristics of a multi-stage centrifugal pump rotor through fluid–structure interaction (FSI) analysis. A two-stage centrifugal pump equipped with back vanes on the trailing impeller is selected as the research object. Numerical simulations are performed based on the continuity equation and Reynolds-averaged Navier–Stokes (RANS) equations, with experimental data utilized to validate the numerical model’s accuracy. The internal flow field mechanisms are analyzed, and the effectiveness of two axial force calculation methods—formula-based and numerical simulation-based—for the rotor system is comprehensively evaluated. Employing an FSI-based modal analysis approach, the governing differential equations of motion are established and decoupled via Laplace transformation to introduce modal coordinates. Modal analysis of the pump rotor system is conducted, revealing the first six natural frequencies and corresponding vibration modes, along with critical speed calculations. The findings demonstrate that when the flow field near the back vanes exhibits complex characteristics, the formula-based axial force calculation shows reduced accuracy. In contrast, without back vanes, the hydraulic motion in the impeller rear chamber remains relatively stable, resulting in higher accuracy for formula-based axial force predictions. The calculation error between the two conditions (with/without back vanes) reaches 27.6%. Based on vibration mode characteristics and critical speed analysis, the pump is confirmed to operate within a safe region. The rotor system exhibits two similar adjacent natural frequencies differing by less than 1 Hz, with perpendicular vibration mode directions. Additionally, rotational speed fluctuations in the rotor system induce alternating critical speed phenomena when operating in this region. This study establishes a coupled analysis framework of “flow field stability–axial force calculation accuracy–rotor dynamic response”, quantifies the axial force calculation error patterns under different flow field conditions of a special pump type, supplements the basic data on axial force calculation accuracy for complex structure centrifugal pumps, and provides new theoretical insights and reference benchmarks for the study of hydraulic–mechanical coupling characteristics of similar fluid machinery. In engineering applications, it avoids over-design or under-design of thrust bearings to reduce manufacturing costs and operational risks. The revealed rotor modal characteristics, critical speed distribution, and frequency alternation phenomena can provide direct technical support for the optimization of operating parameters, vibration control, and structural improvement of pump units in industrial scenarios, thereby reducing rotor imbalance, bearing wear, and other failures. Full article

Sliding bearings–rotor systems are widely present in rotating machinery structures. The dynamic behavior triggered by friction and rub-impact faults is a key factor restricting the safe and stable operation of a rotor system. Existing studies mainly focus on analyzing dynamic characteristics but rarely explore the degree of friction and rub-impact in the system. This paper takes the sliding bearing–double-disk rotor system with friction and rub-impact as the research model, and defines the concept of the rubbing ratio. It analyzes the influence of relevant structural parameters on the system. The results reveal that the system exhibits rich nonlinear dynamics. Specifically, increasing either the rotor–stator clearance or the lubricant viscosity can drive the system into a broader regime of chaotic motion, while simultaneously reducing the extent of the rub-impact contact region. As the stator stiffness increases from 10⁷ N/m to 9 × 10⁷ N/m, the number of chaotic windows in the bifurcation diagram increases from one to three, while the maximum rubbing force rises by approximately 58% and the rubbing ratio increases from 50% to 56%. The phenomenon of coexisting attractors in the system is also revealed and analyzed. The above research results help to reveal the motion laws of this type of rotor system and have certain guiding significance for parameter matching and optimization design of the system dynamics. Full article

To mitigate rotor vibrations in magnetic bearing systems arising from mass imbalance, this study proposes a novel suppression strategy that integrates the crested porcupine optimizer (CPO) with an enhanced linear active disturbance rejection control (ELADRC) framework. The approach introduces a disturbance estimation and compensation scheme based on a linear extended state observer (LESO), wherein both the LESO bandwidth ${\omega }_0$ and the LADRC controller parameter ${\omega }_c$ are adaptively tuned using the CPO algorithm to enable decoupled control and real-time disturbance rejection in complex multi-degree-of-freedom (DOF) systems. Drawing inspiration from the crested porcupine’s layered defensive behavior, the CPO algorithm constructs a state-space model incorporating rotor displacement, rotational speed, and control current, while leveraging a reward function that balances vibration suppression performance against control energy consumption. The optimized parameters guide a real-time LESO-based compensation model, achieving accurate disturbance cancelation via amplitude-phase coordination between the generated electromagnetic force and the total disturbance. Concurrently, the LADRC feedback structure adjusts the system’s stiffness and damping matrices to improve closed-loop robustness under time-varying operating conditions. Simulation studies over a wide speed range (0~45,000 rpm) reveal that the proposed CPO-ELADRC scheme significantly outperforms conventional control methods: it shortens regulation time by 66.7% and reduces peak displacement by 86.8% under step disturbances, while achieving a 79.8% improvement in adjustment speed and an 86.4% reduction in peak control current under sinusoidal excitation. Overall, the strategy offers enhanced vibration attenuation, prevents current saturation, and improves dynamic stability across diverse operating scenarios. Full article

A precise characterization of molecular vibrations and thermodynamic properties is essential for applications in spectroscopy, computational modeling, and chemical process design. In this study, the q-deformed Tietz (qDT) oscillator is applied to examine vibrational energy spectra of diatomic molecules and thermodynamic properties of nonlinear symmetric triatomic molecules. Vibrational energy eigenvalues were obtained analytically using the improved Nikiforov-Uvarov method. The symmetric vibrational mode was described with the qDT oscillator, while asymmetric and bending modes were modeled using the rigid rotor harmonic oscillator (RRHO); translational and rotational contributions were incorporated from standard models. For diatomic molecules (BrF, CO⁺, CrO, ICl, KRb, NaBr), mean absolute percentage errors (MAPE) ranged from 0.53% to 1.73% for vibrational energy eigenvalues and 0.34% to 1.08% for potential fits. Extending the analysis to triatomic molecules, thermodynamic properties of AlCl₂, BF₂, Cl₂O, OF₂, O₃, and SO₂ were calculated with the qDT model, yielding low MAPE benchmarked against NIST-JANAF reference data: entropy 0.203% to 0.614%, enthalpy 1.792% to 5.861%, Gibbs free energy 0.419% to 1.270%, and constant-pressure heat capacity 1.475% to 4.978%. These results demonstrate the versatility and accuracy of the qDT oscillator as an analytical framework connecting molecular potentials, vibrational energies, and thermodynamic functions, providing a practical and tractable approach for modeling both diatomic and symmetric triatomic systems. Full article

Three-phase induction motors (TIMs) are widely used in industrial applications, with bearings and rotors representing the most failure-prone components. Detecting incipient damage in these elements is particularly challenging. The associated signatures are weak and highly sensitive to variations, and their identification typically demands sophisticated filters, deep learning models, or high-cost sensors. In this context, the main goal of this work is to propose a new algorithm that reduces the dependence on such complex techniques while still enabling reliable detection of realistic faults using low-cost sensors. Therefore, the proposed Discriminative Band Energy Analysis (DBEA) algorithm operates on vibration signals acquired by low-cost accelerometers. The DBEA operates as a low-complexity filtering stage that is inherently robust to noise and variations in operating conditions, thereby enhancing discrimination among fault classes, without requiring neural networks or deep learning techniques. Moreover, the interaction of concurrent faults generates distinctive amplitude-modulated patterns in the vibration signal, making the AM demodulation-based algorithm particularly effective at separating overlapping fault signatures. The method was evaluated under a wide range of load and voltage conditions, demonstrating robustness to speed variations and measurement noise. The results show that the proposed DBEA framework enables non-invasive classification, making it suitable for implementation in compact and portable diagnostic systems. Full article

Helicopter vibration is an inherent characteristic of rotorcraft operations, arising from transmission dynamics and unsteady aerodynamic loading, posing challenges to flight control and longevity of structural components. Excessive vibration elevates pilot workload and accelerates fatigue damage in critical components. Leveraging advances in optimal control and microelectronics, the active vibration control methods offer superior adaptability compared to the passive techniques, which are limited by added weight and narrow bandwidth. In this study, a comprehensive vibration analysis and optimal control framework are developed for the Bo 105 helicopter rotor blade exhibiting flapping, lead-lag, and torsional (triply coupled) motions, where a Linear Quadratic Regulator (LQR) is employed to suppress vibratory responses. An analytical formulation is constructed to estimate the blade’s sectional properties, used to compute the coupled natural frequencies of vibration by the modified Galerkin method. An orthogonality condition for the coupled flap–lag–torsion dynamics is established to derive the corresponding state-space equations for both hovering and forward-flight conditions. The LQR controller is tuned through systematic variation of the weighting parameter Q, revealing an optimal range of 10²–10⁴ that balances vibration attenuation and control responsiveness. The predicted frequencies of the vibrating rotor blade are compared with the finite element modeling results and published experimental data. The proposed framework captures the triply coupled rotor blade dynamics with optimal control, achieves modal vibration reductions of approximately 60–90%, and provides a clear theoretical benchmark for future actuator-integrated computational and experimental studies. Full article

With the increase in thrust–weight ratio of advanced aeroengines, the rotor and stator often exhibit comparable stiffness characteristics, leading to significant vibration coupling which harms the safety and reliability of operations. However, an effective vibration coupling evaluation method for complex rotor–stator systems is still lacking. This paper proposes the Vibration Coupling Evaluation Factor (VCEF) to quantitatively evaluate the interaction between the rotor and stator within the framework of the linear system. Then a new evaluation procedure is established for the structural optimization during the early design phase and the fault source localization in troubleshooting scenarios in the high-speed rotating machinery. In this paper, two typical rotor–stator systems are studied with the VCEF method: a simplified rotor–stator system is studied numerically to reveal the influence pattern of different parameters, and a complex rotor–stator system is studied numerically and experimentally to examine the validity of the evaluation method. The results show that VCEF can effectively capture rotor–stator vibration coupling. The VCEF curve with rotational speed shows a significant stepped decrease, indicating a significant strengthening of the rotor–stator vibration coupling, which aligns closely with experimental data. This evaluation method quantitatively assesses the degree of rotor–stator vibration coupling by comparing the differences in modal characteristics between the rotor system and the rotor–stator system under the gyroscopic effect. Optimizing rotor–stator stiffness and mass distribution based on VCEF mitigates operational risks in high-speed regimes. This methodology provides engineers with a systematic, quantitative tool to determine when integrated rotor–stator analysis is essential for accurate dynamic prediction and offers broad applicability to aeroengine design and other high-speed rotating machinery. Full article

A heavy-duty vibrating screen with excitation sources is a mining vibrating machine synchronized by two eccentric rotors, exhibiting typical coupled dynamic behavior. Aiming at the coupling dynamic behavior of dual excitation sources based on the nonlinear vibration of a heavy-duty mining screen, theoretical research and experimental analysis of coupling synchronization are carried out, and the dynamic reasons for the dual excitation sources to achieve vibration synchronization are discussed. Based on nonlinear vibration theory, electromechanical coupling nonlinear dynamics equations for a dual excitation source vibrating screen are established in this paper, and the coupled dynamics factors of the two eccentric rotors are analyzed. The impact of coupling strength on the equilibrium state of the nonlinear vibration system is discussed, and the evolution process of the synchronous motion of the two eccentric rotors is further investigated, revealing the causal relationship by which the dual excitation sources achieve synchronization due to coupled dynamics behavior. The results show that the coupling effect of the multi-exciter is based on the nonlinear vibration of the vibration system, and the motion characteristics and motion mode of the exciter will change, and, finally, a coupled synchronous motion state will be reached. The research results can provide ideas for the mechanical structure design of heavy-duty mining screens excited by multiple excitation sources and can provide a theoretical basis and application reference for the selection of structural parameters of this kind of mining machinery. Full article

Fatigue-related ‘rotor crack’ can cause catastrophic failure if neglected. Thus, IoT-enabled AI-based predictive maintenance for fault detection and diagnosis is explored. Training and testing AI models under similar conditions improves their prediction performance. On variable speed machines, loss of performance occurs when the testing speed differs from the training speed. This research addresses significant performance loss issues using convolutional neural network (CNN)-based transfer learning models. The main causes of performance loss are domain shift, overfitting, data class imbalance, low fault data availability, and biassed prediction. All the above difficult issues make CNN-based fault prediction systems function badly under varying operating conditions. The proposed methodology addresses all domain adaptation challenges. The proposed methodology was tested by collecting vibration data from an experimental rotor system under varied operating conditions. The proposed methodology outperforms classical machine learning (ML) and deep learning (DL) models, overcoming the overfitting issue with optimised hyperparameters, achieving a prediction accuracy of 99.5%. Under varying operating conditions, it outperforms with a prediction accuracy of 93.2%, and in the ‘data class imbalanced’ scenario, the maximal transfer learning capability achieved was 84.4% with the highest F1-Score. Thus, CNN-based transfer learning enables industrial variable speed machines diagnose rotor crack flaws better than ML and DL models. Full article

To address flight safety risks from rotor defects in rotorcraft drones operating in complex low-altitude environments, this study proposes a high-precision diagnostic model based on the Multimodal Data Input and Spatio-Temporal Feature Fusion Network (MDI-STFFNet). The model uses a dual-modality coupling mechanism that integrates vibration and air pressure signals, forming a “single-path temporal, dual-path representational” framework. The one-dimensional vibration signal and the five-channel pressure array are mapped into a texture space via phase space reconstruction and color-coded recurrence plots, followed by extraction of transient spatial features using a pre-trained ResNet-18 model. Parallel LSTM networks capture long-term temporal dependencies, while a parameter-free 1D max-pooling layer compresses redundant pressure data, reducing LSTM parameter growth. The CSW-FM module enables adaptive fusion across modal scales via shared-weight mapping and learnable query vectors that dynamically assign spatiotemporal weights. Experiments on a self-built dataset with seven defect types show that the model achieves 99.01% accuracy, improving by 4.46% and 1.98% over single-modality vibration and pressure inputs. Ablation studies confirm the benefits of spatiotemporal fusion and soft weighting in accuracy and robustness. The model provides a scalable, lightweight solution for UAV power system fault diagnosis under high-noise and varying conditions. Full article

Permanent magnet synchronous generators (PMSGs) are suitable for offshore applications due to their high efficiency and power density. Inter-turn short circuits (ITSCs) stand as one of the most critical faults in these machines due to their rapid evolution in phase or ground short circuits. It is therefore necessary to detect ITSCs at an early stage. In the literature, ITSC detection is often based on current signal processing methods. One of the challenges that these methods face is the presence of imperfections in the stator coils, which also affects the three-phase symmetry. Moreover, when the stator coils are connected in parallel, this type of fault becomes important, as circulating currents will flow between the parallel windings. This, in turn, increases the thermal stress on the insulation and the permanent magnets, while also exacerbating the vibrations of the generator. In this study, a finite-element analysis (FEA) model has been developed to simulate a dual-rotor PMSG under conditions of coil asymmetry. To further investigate the impact of this asymmetry, mathematical modeling has been conducted. For fault detection, negative-sequence current (NSC) analysis and torque monitoring have been used to distinguish coil asymmetry from ITSCs. While both methods demonstrate potential for fault identification, NSC induced small amplitudes and the torque analysis was unable to detect ITSCs under low-severity conditions, thereby underscoring the importance of developing advanced strategies for early-stage ITSC detection. The innovative aspect of this work is that, despite these limitations, the combined use of NSC phase-angle tracking and torque harmonic analysis provides, for the first time in a core-less PMSG with parallel-connected coils, a practical way to distinguish ITSC from coil asymmetry, even though both faults produce almost identical signatures in conventional current-based indices. Full article

Designed to mitigate the significant low-frequency vibration and noise inherent in conventional marine centrifugal pump systems, the magnetic levitation pump constitutes a novel form of centrifugal pump employing active magnetic bearing technology. While this fully levitated design effectively enhances vibration and noise performance, it results in the complete immersion of the rotor within a confined fluid domain, which contains narrow fluid clearances. This poses significant challenges for the accurate computation of rotor wet modes, which is crucial for the structural design of the rotor system to avoid the resonance induced by flow. Despite exerting a substantially greater influence on rotor wet modal characteristics than unconfined domains, the analysis of rotors under confined fluid conditions has received comparatively little research attention. This study focuses on two types of magnetic levitation pump rotors. From the perspective of analytical modeling, an improved analytical method for wet modal computation based on added mass correction is proposed. The validation of this method included examining two distinct computational approaches for the added mass, the thickening treatment for axially elongated disk components, and the methodology for implementing disk equivalent density. Based on this foundation, wet modal analysis was performed on both rotors utilizing the proposed analytical method, alongside acoustic fluid–structure interaction simulations. The results indicate that for the first bending mode, the errors between the analytical and experimental values are 1.2% and 4.1%, respectively, while the discrepancies between the simulated and experimental values are 0.1% and 3.2%. Finally, regularity analysis was conducted on the wet modal characteristics of the rotor under confined water, considering various fluid clearances. The results reveal that the first three bending modes generally exhibit an increasing trend with the enlargement of the fluid clearance, with a triple-size annulus serving as a transition point. However, increasing the annulus size does not always elevate the modal frequencies above their initial values. This study contributes to understanding the influence mechanisms of confined water on the wet modal properties of magnetic levitation pump rotors. Furthermore, the proposed analytical method improved computational efficiency for the early design stages of water-immersed rotors, alongside a model of greater accuracy essential for magnetic bearing control. Full article

Magnetically suspended rotor systems are widely used in high-speed and precision applications, where mass imbalance-induced synchronous vibration remains a primary challenge affecting stability and control performance. Numerous control strategies have been developed to suppress such vibrations, which can be broadly categorized into frequency-domain and time-domain approaches. Frequency-domain methods, represented by various forms of notch filters, selectively attenuate synchronous components with high robustness and clear physical interpretation. Time-domain methods, including the influence coefficient method and adaptive filtering techniques, offer strong adaptability and high suppression accuracy under varying operating conditions. This review summarizes the principles, advantages, limitations, and engineering applications of these techniques, highlighting their evolution from single-channel models to multi-channel and multi-stage implementations. Finally, current challenges and future research directions are discussed to provide guidance for the development of imbalance suppression strategies in advanced AMB systems. Full article