A dynamic similitude design method is proposed for the problem of sudden unbalance of the rotor system. The dynamic differential equation requires the application of both equation analysis and dimensional analysis methods to establish the scaling laws, while also considering the damping scaling ratio. Based on the strain energy distribution criterion, a prototype rotor system is designed. The prototype is scaled according to the scaling laws to create a distorted model, and the dynamic similarity between the prototype and the distorted model is verified through simulation and test. The simulation results show that the distorted model exhibits high similarity to the prototype in terms of critical speed, strain energy distribution, and transient response. The errors for the first two critical speeds are 0.1% and 0.13%, respectively, and the error in peak amplitude is 3%. The test results show that the distorted model can accurately predict the critical speed and sudden unbalance vibration response of the prototype, with the errors for the first two critical speeds being 0.79% and 1.72%, respectively, and the error in peak amplitude being 5.98%.

Aiming at the vibration problem of rotating pre-twisted beams in engineering, an effective modeling method is proposed to study their vibration characteristics. Rotating experiments are designed to verify the accuracy of theoretical research. By adjusting the boundary spring stiffness, different boundary conditions are simulated. The displacement field is expanded using the modified Fourier series method, and the motion equation of the rotating beam is derived using the Rayleigh-Litz method. Based on the theoretical research, vibration tests of rotating straight beams and pre-twisted beams with different sizes are designed. The accuracy of this method is verified by comparing the theoretical calculations with finite element simulations and experimental results. The possibility of elastic boundaries is also verified through error analysis. The results show that the natural frequency of the beam increases with the increase in rotating speed and thickness. The increase in pre-twist angle has a minimal effect on the first-order natural frequency but significantly reduces the second-order natural frequency.

Parametric vibrations are commonly observed in microelectromechanical systems(MEMS) coupled with multi-physical fields. To study the parametric resonance nonlinear dynamics problems in electrostatically driven micromirror systems, a class of electrostatic comb-driven micromirrors is used as an example to study the parametric resonance response variation of the system under different factors by fitting a seventh-order polynomial to the comb capacitance variation and establishing a micromirror dynamics model. The influence of changes in the micromirror’s structural parameters on the torsion angle under static conditions is investigated. The multi-scale method is applied to analyze how system parameters affect the variation in resonance amplitude during the resonance state, and numerical verification of system parameter resonance is performed. Finally, the stability of subharmonic parametric resonance in the system is analyzed and verified using the Runge-Kutta method. The results show that subharmonic parametric resonance exists in the micromirror system. Factors such as excitation voltage and capacitance fitting parameters can affect the system’s resonance amplitude. Damping can alter the system’s instability region, increase the instability threshold, and influence the occurrence of subharmonic parametric resonance in the system.

To address the problem of contact between the slender rods and tubes immersed in fluid, a numerical method is established to model the coupling vibration and collision between slender rotating rods and the produced fluid, based on the overset mesh technique. The outer annulus fluid domain is divided into two overset subregions: a background mesh and a component mesh. The interpolation formula is derived to transfer fluid field boundary information in each overset region. The subdomain method is used to solve the coupling between the produced fluid domain and the rod solid domain. Additionally, the transfer method of physical variables and a normalized convergence criterion are established for the coupling interface. A coupling simulation device for a vertical rotating rod and produced fluid is established, and the numerical simulation results are compared with experimental results to validate the correctness of the numerical method presented in this paper. The coupled vibration and collision characteristics between the slender rods and tubes are studied under different fluid viscosities and rotational velocities. The results show that as fluid viscosity increases, the influence of viscous resistance on the motion of the rod becomes more pronounced, leading to lower contact pressure and reduced vibration. As the rotational speed of the rod increases, the vibration becomes more intense, the influence of torsional deformation on the rod’s motion becomes more significant, the normal acceleration during collision decreases, and the contact pressure decreases accordingly. When the collision occurs between the rods and tubes, the acceleration at each point of the rod changes abruptly, and the vibration intensity increases.

Clustering analysis is a commonly used unsupervised method in data processing. However, the difficulty in accurately determining clustering parameters limits the application of this method in structural damage identification. To address this issue, a non-parametric Bayesian clustering method is proposed in this study, which combines structural modal parameters for structural damage identification and quantitative analysis, thereby expanding the application range of the non-parametric Bayesian model.First, the natural excitation method is used to extract the natural frequency from the measured vibration data of the structure.Then, the non-parametric Bayesian clustering method is employed to cluster the data. Finally, maximum likelihood heteroscedastic Gaussian process regression and Bayesian factors are combined to quantitatively analyze the clustering results for damage quantitation analysis. The results of the damage identification method are verified by the actual engineering case of Yonghe Bridge in Tianjin. The results show that this method can accurately cluster the natural frequency data and identify the different damage states of the structure without the need to pre-set clustering parameters.

In order to evaluate the fatigue performance of the steel anchor box (SAB) when its stay cable experiences large-amplitude vortex-induced vibration (VIV) under in-service condition, continuous monitoring was conducted on a long-span cable-stayed bridge. The acceleration of the stay cable undergoing VIV and the stress at the SAB details were measured. The characteristic of stay cable vibration, as well as the stress at the SAB details due to VIV of the stay cable, vehicles loading, and thermal effects, were investigated in both time and frequency domains. Hence the loading mechanisms of VIV, vehicle loading, and thermal effects on the SAB were discussed. Based on the nominal stress method, the fatigue performance of the SAB under the joint action of VIV, vehicle loads and thermal effects were evaluated. The results show that the significant vibration of stay cable, characterized by the high-order multi-mode VIV, dominated by in-plane vibration with peak frequencies between the fifth and the seventeenth modes, occurring within a mean wind speed range of 2 m/s to 9 m/s, with observed maximum in-plane peak acceleration of 25 m/s².Thermal effects significantly contribute to the maximum stress range at the SAB details, although they only generate one stress cycle per day. Compared to the thermal action, the stress range generated by the passage of vehicles is relatively low, but trucks produce a large number of loading cycles. The inertial force generated by VIV of the stay cable applies very low stress to the SAB, making its effects on stress and fatigue negligible. It is concluded that the fatigue evaluation of the steel anchor box should consider the thermal effects. However, even when considering the combined effects of VIV loading, thermal effects and vehicle loading, the fatigue life at the critical details of the SAB—specifically the deck-side welds of the upper and lower plates to the outer web, as well as both weld ends of the bearing plate to the outer web of the steel box girder—exceeds 100 years. Therefore, the fatigue performance of the SAB under in-service conditions meets the bridge design requirements, even with large-amplitude VIV of the stay cable.

In complex hilly terrain, the wind field around interfered hills is influenced by nearby hills, which affects the wind-induced fatigue damage of the tension suspension-braced transmission structure. Therefore, the effect of occluding hills must be considered in the analysis of wind-induced fatigue. In order to analyze the influence of occluding hills on the wind-induced fatigue damage of the transmission structure in complex hilly terrain, wind tunnel tests on the wind filed characteristics of complex hilly terrain were first conducted. Based on the test results, the variation of the mean velocity correction factor and the fluctuating velocity correction factor of the wind field around interfered hills, with different slopes, heights and interval distances of occluding hills, were studied, and a corresponding distribution model was proposed. Next, a nonlinear finite element model for wind-induced vibration of the tension suspension-braced transmission structure considering the effect of occluding hills was established using the nonlinear finite element method. Then the time domain rain-flow method and the Miner’s linear cumulative damage theory were applied to estimate the wind-induced damage to the structure. Finally, a two-span tension suspension-braced transmission structure was selected as a case study, and considering the effect of occluding hills, the wind-induced fatigue damage was analyzed using the proposed model. The results show that: the fatigue damage in each part increases initially and then decreases as the slope of the occluding hills increases. The heights of occluding hills have little effect on the fatigue damage of each part, with no obvious trend. When the interval distances between occluding hills is between 0 m and 600 m, the fatigue damage in each part gradually decreases as the distance increases. However, when the interval distance is between 600 m and 800 m, the fatigue damage of each part suddenly increases as the distance increases. Under the influence of the same occluding hill, the fatigue damage of the end of the conductor and the supporting-conductor suspension cable is greater than that at the mid-span.

Tuned liquid damper (TLD) is a common type of passive damper system in high-rise buildingsl. However, the damping of a pure water TLD system is relatively small. Adding internal baffles can significantly increase its damping ratio, thereby improving its vibration control efficiency. In this study, a numerical simulation of liquid sloshing in a TLD system with vertical baffles is conducted using the open-source computational fluid dynamics(CFD) software OpenFOAM. The wind-induced response of the benchmark building for the third-generation wind-induced vibration control study is investigated using the computational structure dynamics (CSD) method. On this basis, the CFD/CSD coupling numerical simulation is conducted to evaluate the control efficiency on wind-induced vibration control of a tall building and a TLD system with built-in vertical baffles. The CFD/CSD coupling numerical simulation results show that the TLD system with three vertical baffles has a significant control effect on the wind-induced response of the benchmark building under dynamic wind loading with different return periods. The comparison with real-time hybrid test results also confirms that the proposed numerical algorithm in this paper has sufficient accuracy in estimating the wind-induced control efficiency.

A typical streamlined closed-box girder is taken as the research object in this paper. Utilizing the wind tunnel tests with a section model, vortex-induced vibration (VIV) responses of the grinder section were obtained, and the contribution values of the distributed aerodynamic torques were analyzed for both the original and improved girder designs (the improved girder with spoilers and the improved girder with guide vanes for maintenance rails) under typical wind conditions. By combining the simplified vortex method (SVM) with numerical simulation, the torsional VIV of the bridge girder and its suppression mechanism with additional aerodynamic countermeasures were further revealed. This paper provides a new methodology for analyzing the VIV mechanism of bridge girders and the VIV suppression mechanism of aerodynamic countermeasures. The results reveal that an obvious torsional VIV phenomenon was observed on the original girder, with a maximum amplitude of 0.112°. After adding guide vanes for the maintenance rail, the torsional VIV amplitude of the section was reduced by 35.7%, and the torsional VIV phenomenon disappears after the addition of the spoilers on the sidewalks’ handrails. For both the original and guide vane girders, the contribution values of the distributed aerodynamic torques on the upper surface to the global vortex excited force (VEF) were much greater than those on the lower surface. The VIVs of the original and guide vane girders were dominated by the periodic drift of the large-scale vortices generated from the leading edge to the trailing edge on the upper surface. The drift time of the vortices was approximately 2.5 vibration cycles, which corresponds to the second-order torsional simplified vortex mode. After the installation of guide vanes for the maintenance rails, the contribution values of the distributed aerodynamic forces to the global VEF were significantly reduced, and the scale and intensity of vortices around the girder were reduced, so the VIV amplitude decreased. After adding spoilers, the contribution values of the distributed aerodynamic forces to the global VEF became more evenly distributed and were greatly reduced.Spoilers inhibited the formation of separation vortices at the leading edge of the upper surface, effectively eliminating the VIV phenomena.

Higher-order harmonics of crowd loads may can lead to an increase in the dynamic response of high-frequency floors, resulting in serviceability and safety issues. This study aims to analyze the effect of different indoor layouts on the human-induced vibration of high-frequency floors. First, a random load model for high-frequency floors is established by combining the social force model (SFM) and a pedestrian load model. Next, a computational model for human-induced vibration of high-frequency floors is developed, taking into account human-structure interaction (HSI). A high-frequency floor with a fundamental frequency of 10.35 Hz is tested to validate the reasonableness of the computational model when applied to different layout configurations. Finally, the serviceability of the floor with different layout forms under random crowd walking conditions is evaluated using the global assessment method for human-induced vibration, with probabilistic results provided. The results show that for human-induced vibration problem in high-frequency floors, the influence of high-order vibration modes must be considered. Under the random walking conditions for five people, the dynamic response of the floor with different layouts is reduced after considering HIS, with a maximum reduction of 13.33% in peak acceleration and a maximum reduction of 12% in probability value of serviceability. The serviceability of the floor varies with the different layout configuration. Specifically, the probability of serviceability problems is highest for the floor with a discussion room layout, followed by the classroom layout, with the meeting room layout the lowest probability.

In order to prevent unseating during earthquakes, both domestic and foreign seismic codes for bridges require the use of unseating prevention devices. However, research on the effectiveness of these devices is limited. This article focuses on a bridge using a longitudinal barrier-type unseating prevention beam device, examining the limitations and effectiveness of such devices in preventing unseating. First, the working principle of the longitudinal barrier-type unseating prevention device is introduced. On this basis, a five-span simply supported beam bridge is studied, considering the nonlinear mechanical behavior of concrete blocks as a typical longitudinal barrier-type unseating prevention device. The study analyzes and compares the effects of block device strength, clearance, and the installation of rubber pads on the limiting and unseating prevention capabilities of the device. Research has shown that the effectiveness of the devices is closely related to its strength , initial clearance, and the intensity of seismic motion.Proper device strength and initial clearance can help reduce collision forces and frequencies, lower the risk of beam unseating, and control bridge pier damage within an ideal range. Furthermore, placing buffer rubber pads at the contact surfaces between the unseating prevention device and the substructure can effectively reduce pounding forces and minimize pier damage.

This paper presents a simplified structural model for continuous variable cross-section single-pile foundations of offshore wind turbines, considering the water-pile-soil interaction, using the Euler-Bernoulli beam theory. The simplified model is solved using the differential transform method to obtain the transverse vibration control equation. The investigation focuses on the impact of tower diameter, transition section height, water-added mass, impeller-nacelle assembly mass, and the stiffness of three springs on the transverse natural frequency. The results show that the influence of the bottom diameter of the variable cross-section tower on the natural frequency is greater than that of the top diameter. In offshore wind turbine installations with greater water depths, the effect of water-added mass on the structural natural frequency cannot be overlooked. The transverse natural frequency of the wind turbine decreases as the impeller-nacelle assembly mass increases. The sensitivity of the soil modulus to the spring stiffness is ranked as follows: horizontal spring > coupling spring > rotational spring. Similarly, the sensitivity of the natural frequency to the spring stiffness is ranked as: coupling spring > horizontal spring > rotational spring. When variations occur in the soil modulus, the primary influence on the natural frequency is predominantly exerted by the horizontal spring and the coupling spring.

To study the seismic performance of low-rise pavilion-type ancient timber structure, shaking table tests were conducted on a 1: 6 scaled model of the Xi’an Bell Tower. The Kobe wave, Lanzhou wave and Wenchuan wave with the seismic intensity levels ranging from 7-degree frequently to 9-rarely were considered as input excitations. The dynamic characteristics, dynamic responses and energy consumption of the structure were identified. The test results indicate that, as the peak ground acceleration(PGA) increased, the natural frequency of the model structure decreased marginally, while the damping ratio increased significantly. The stiffness was not uniformly distributed along the height of the structure, with the smallest stiffness found at the Dougong storey on the external gold cylinder, which also experienced the maximum inter-story drift. The acceleration amplification factors of the model were generally less than 1, exhibiting obvious seismic reduction effects. Compared with modern structures, the plastic strain energy of the ancient timber structure was relatively small, which helps reduce structural damage.

In the southwest region of China, the construction of highways has resulted in the formation of many cutting slopes due to the special terrain conditions of the region. Therefore, the stability of highway cutting slopes under earthquake conditions has become a critical issue in the stability evaluation of highway engineering. In this research, the acceleration response of stepped bedding rock slopes is analyzed by conducting large-scale shaking table tests, and the seismic response of each platform is investigated.A ratio of acceleration amplification factor is proposed to characterize the differences in dynamic responses of various slope patterns and analyzes the seismic wave propagation in the slope using Snell’s law. The test reveals that the acceleration amplification factor of the slope exhibits an elevation amplification effect as the amplitude of the excitation increases. When the excitation amplitude exceeds 0.6g, the continuous accumulation of slope shattering damage and the enhancement of the filtering effect lead to a leveling off of the acceleration amplification factor with increasing elevation. Besides, slopes with uniform step width demonstrate better aseismic performance, while stress concentration is more likely to occur at the corners of each step, making them as key fortification sites. The analysis of the monitored acceleration data is consistent with the model damage patterns recorded by a high-speed camera during the shaking table tests. Based on the cumulative shattering damage process of the slope, four stages of damage are identified: shallow creep (0.1g~0.4g), local tension (0.4g~0.6g), accelerated deformation (0.6g~0.8g), and overall instability(0.8g~1.0g), exhibiting a slip-tensile damage mode. The research findings provide essential theoretical support and technical guidance for understanding the shattering damage mechanism and seismic fortification of rock slopes with complex formations and geological structures, and offer a reference for disaster prevention and mitigation measures for stepped bedding rock slopes in mountainous areas.

When braking is applied to a heavy-haul train, the dynamic behavior of the train becomes more complex compared to when there is no braking, which poses significant challenges to the safety of train operations. In order to study the vehicle dynamics behavior at the maximum coupler force of a heavy-haul train under emergency braking conditions, a vehicle-track and longitudinal-vertical coupled dynamic model, considering the effects of shoe friction braking, is established with a 25 t axle heavy-haul wagon from China as the research object. On this basis, this study systematically examines the impact of varying running speeds and adhesion conditions on the dynamic wheel-rail interaction and vehicle vibration response during emergency braking. The results show that under braking conditions, the brake shoe pressure and longitudinal coupler force exacerbate the wheel-rail dynamic interaction and cause changes in the displacement of the under-rail structure. The low adhesion condition has a significant effect on the longitudinal interaction of the wheelsets, leading to a sharp increase in the longitudinal creep rate and wear number, thus increasing the risk of wheel slip and wear. This effect is more pronounced at low speeds. Moreover, the low adhesion condition and longitudinal coupler force significantly affect both the rotational and longitudinal motion of the wheelsets, leading to increased wheelset vibration and deterioration of vehicle dynamics.

This study addresses the complex scenario where the parameters of the powertrain mounting system (PMS) of an electric vehicle exhibit both uncertainty and correlation. A robust design optimization method for the PMS, considering parametric uncertainty and correlation, is investigated. Firstly, based on Nataf transform and Monte Carlo sampling, the Nataf-Monte Carlo(NMC) method is proposed for the uncertainty and correlation analysis of PMS inherent characteristics, where the probabilistic parameters are correlated. Then, an efficient method, the Nataf-arbitrary polynomial chaos expansion (NAPCE) method, is derived for PMS response analysis by integrating Nataf transformation with arbitrary polynomial chaos expansion. Next, based on the NAPCE method and correlation coefficient weighting method, a robust design optimization method for PMS is developed, accounting for the uncertainty and correlation of responses. Finally, a numerical example is used to verify the effectiveness of the proposed method, and the robust optimization of the system is carried out. The results show that, compared to the NMC method, the NAPCE method offers good computational accuracy and efficiency for analyzing uncertainty and correlation in PMS responses. The proposed optimization method can configure the PMS parameters reasonably and improve the robustness of system.

This study investigates the influence of installation methods on the optimization design and vibration reduction performance of a novel tuned mass damper inerter (NTMDI). Firstly, the mechanical model of NTMDI-R (reverse-installed NTMDI)is introduced in detail, and its optimization design of NTMDI-R is performed using classical fixed-point theory, resulting in analytical expressions for the optimal structural parameters of NTMDI-R. Subsequently, a comparative study is conducted to analyze the vibration reduction effects of NTMDI-R and four existing classical tuned mass dampers (TMD, TMDI, VTMD, and NTMDI)under harmonic and random excitations, while also investigating the influence of installation methods on the vibration reduction performance of NTMDI-R. The results demonstrate that the optimized parameters of the two dampers (NTMDI and NTMDI-R) differ, and the installation method has a significant impact on their vibration reduction performance. When the apparent mass ratio β is less than 0.1, NTMDI-R exhibits a lower vibration reduction effect compared to NTMDI. However, when β exceeds 0.1, the vibration reduction effect of NTMDI-R becomes similar to that of NTMDI. Therefore, when adopting NTMDI for structural vibration reduction, the installation direction should be specified. Under base acceleration and load force conditions, the vibration reduction effect of NTMDI-R is reduced by 3.9% and 4.7%, respectively, compared to NTMDI.

The narrowband active control system is suitable for controlling low-frequency harmonic noise. In practical applications, the problem of reference signal mismatch caused by the rapid frequency changes of the original noise will seriously degrade the performance of the narrowband active control system. Existing frequency estimation algorithms often struggle to balance the speed, accuracy, and computational complexity required to track the actual frequency. This paper proposes a Notch-HAQSE frequency estimation algorithm for narrowband active control, which extracts any number of line spectrum frequency components from the reference sensor signal by combining a notch filter with a high-precision single-frequency estimation algorithm based on DFT coefficients (HAQSE). The synthesized reference signal is sent to the controller to complete secondary signal updating. Simulation and experimental results show that, compared with other frequency estimation methods used in active control, the proposed method accurately identifies and rapidly tracks multiple frequencies while significantly reducing computational complexity. It effectively addresses the problem of reference signal mismatch and multi-line spectrum vibration noise control.

To gain a deeper insight into the sorting of main launching noise sources in underwater weapons, different sub-noise sources and their contribution to the overall radiation noise are analyzed through both analytical and experimental research, focusing on the typical gas-water tank launching device trial model. The acoustic transmission channels of launching noise include hull structure and the seawater-connected domain formed by the pipeline system through which the weapons travels. In the concluded thirteen sub-noise sources, the primary components include 4 structural vibration noises and one impact vibration noise. The former are caused by gas tank seat vibration, tank cylinder wall vibration, torpedo tube wall vibration and piston axial fluctuating force source, all of which radiate noise through two transmission channels. The impact vibration is induced by the piston striking the end wall of the tank and radiates noise mainly through the connected domain. The jet noise radiated by the tube exit flow is comparable to the radiation noise of a quasi-quiet submarine in navigation and makes less contribution to the overall launching noise. The airborne noise of the launching device presents broadband white noise with stepwise elevation, mainly concentrated in high-frequency band, with minimal contribution to the structural vibration noise. The vertical vibration of the gas tank seat and the radial vibration of the tank cylinder wall are significantly affected by the piston’s startup and end crash. The instantaneous vertical impact peak value is one order of magnitude higher than a typical ship diesel engine’s periodic vibration. The radial vibration pulse peak of the tube wall is corresponded to the moment of the piston’s end crash. The ranking of the average vibration levels for the three vibration sources is as follows: gas tank seat vibration, tank cylinder wall vibration, and tube wall vibration.

Research on the identification and diagnosis of high-frequency friction signals under abnormal contact conditions of mechanical seals is limited. Therefore, a seal monitoring test-bed is established using high-frequency, wide-range, and highly sensitive acoustic emission (AE) technology. Acoustic emission signals are collected under various operating conditions of the mechanical seal, including start-stop, no pressure, low pressure, high pressure, low speed, and high speed. Then the collected data are processed and analyzed using time-domain, frequency-domain and time-frequency-domain analysis methods. A method for determining the interface friction state of the mechanical seal, based on the root mean square (RMS) change of the AE signal, is established. This method reveals the corresponding relationship between the end-face friction signal and the running state of the mechanical seal, from contact to non-contact, and further proves the seal operation process. The research identifies the evolution of the friction signal during the transition from boundary lubrication (BL) and mixed lubrication (ML) in end-face contact friction to sliding contact signals under non-contact hydrodynamic lubrication(HL). The frequency band of the AE signal during seal interface friction is found to be between 240 kHz and 320 kHz. Through time-frequency analysis of the AE signal, it is shown that continuous wavelet transform (CWT) effectively represents the time-frequency characteristics of the AE signal under different working conditions of the mechanical seal. The research results of this paper provide a theoretical foundation and data support for research on mechanical seal condition monitoring and fault diagnosis.

In the assembly process of an aero-turboshaft engine, the coaxiality errors of the curvic couplings are an important technical index, significantly affecting the performance and service life of the whole system. This study takes the turbine blade-casing of an aero-turboshaft engine as an example. The coaxiality errors (including both positional and orientation errors) of the curvic couplings are introduced into the clearance function of the blade tip-casing, the nonlinear dynamic model of a rotating taper-blade casing system is then proposed based on the Hamilton variational principle and the Galerkin method. The effectiveness of the proposed model is verified using ANSYS software. Two different acceleration functions are proposed: Function 1 assumes a constant acceleration value, while Function 2 adopts a cosine wave form for acceleration. The effects of different coaxiality errors of the curvic couplings on the transient response during both acceleration functions are further investigated using Newmark-β numerical method.Simulation results show that an increase in the coaxiality error of the curvic coupling leads to a reduction in the minimum clearance between the blade tip and casing, resulting in a more serious amplitude amplification induced by blade-tip casing rubbing. Compared with Function 1, Function 2 enables the system to pass through the critical speed more quickly, which advances the start time of rubbing. In addition, the maximum rubbing force and penetration depth can be effectively reduced due to the effects of the deceleration, weakening the rising and jumping phenomena in the system.

Due to the differences in data distribution caused by different locations of multiple measuring points, the fault diagnosis of the harmonic reducer is often ineffective. A fault diagnosis method for the harmonic reducer, based on a multiple feature spaces adaptation network (MFSAN), is proposed. Firstly, the vibration signal of the harmonic reducer is transformed using continuous wavelet transform to construct a time-frequency diagram that characterizes its operational state. Secondly, the data measured by sensors at different positions are divided into multiple source domain and target domain data, which are mapped to different feature spaces to obtain feature representations for each measuring point position. Then, the adaptive network is used to automatically transfer the knowledge learned from the source domain to the target domain features and automatically align the feature distribution of a specific domain to learn multiple domain-invariant representations. Finally, a domain-specific decision boundary is used to align the output of the classifier, effectively solving the data distribution differences caused by sensor location. Experimental results of harmonic reducer diagnosis of an industrial robot show that the identification accuracy of this method is 99.72%, which is higher than that of other comparison methods. The effectiveness and feasibility of this method are thus verified.

In light of investigating the interplay between the instantaneous angular speed (IAS) signal and mechanical dynamics of bearings, alongside addressing the vulnerability of rotary arm bearings within industrial robot RV reducers to failure under lowspeed conditions, this paper presents a novel three-degree-of-freedom dynamics model to explain the IAS perturbations resultant from localized roller bearing failures. The model, rooted in the Hertz line contact theory, dissects the influence mechanism of localized deformations stemming from roller-raceway interactions on the IAS. A comprehensive approach to computing the coupled tangential force and torque is outlined. The integration of failure-induced impacts into torque analysis computes torque variations introduced by the failure zone, thereby augmenting angular degrees of freedom. As a result, a three-degree-of-freedom bearing IAS disturbance dynamic model, coupling both normal and tangential forces, is established. Employing fourth-order Runge-Kutta numerical integration, the model is solved, and its results are meticulously compared and analyzed against experimental approximations under near-approximate conditions. The findings underscore the model’s ability to effectively expound upon the origins of IAS perturbations in cylindrical roller bearings while adeptly reflecting the ramifications of outer ring failures on IAS. This work contributes to the refinement of rolling bearing dynamics theory, advancing the comprehension of intricate mechanical systems.