Journal of Vibroengineering
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Introduction to the Special Issue: Futuristic trends and emergence of technology in biomedical, nonlinear dynamics and control engineering
Full text linkIn the current era of emerging technologies such as deep learning, artificial intelligence, multimedia data analysis, Internet of Things (IoT), the significant role of vibration analysis can be seen in biomedical, nonlinear dynamics, and control engineering. Despite the numerous applications, lots of challenges and issues are still needed to address like nonlinearity, fault diagnosis, vibration spectrum analysis, and biomedical data monitoring and processing. The aim of this Special Issue is to cover and address all the aforesaid challenges and issues and practical solutions for such emerging technologies. We have received 21 manuscripts in total for this Special Issue across the globe and after the rigorous review process, only 10 manuscripts have been accepted for publication. A brief overview of contributions to this Special Issue is as underneath
Study on torsional vibration of a harmonic driver based on time-varying stiffness caused by manufacturing error
Full text linkThe torsional vibration of Harmonic reducer is concerned with the positioning accuracy and trajectory accuracy of industrial robots. A study on the parametric torsional vibration based on time-varying stiffness will improve the mechanical performance of Harmonic reducer. In this paper, the phenomenon of time-varying stiffness caused by manufacturing error is investigated on a Harmonic driver through mechanism analysis and experimental investigation. Meanwhile, a model of forced parametric vibration is set up for the Harmonic driver transmission system with an inertia load. The parametric vibration response is simulated by the Runge-Kutta method, and the issue of bi-spectra, combined harmonic group, and the envelope of system sweeping frequency response are analyzed in detail. The influence of double periodic time-varying stiffness on vibration is emphasized with simulation data. To observe the characteristic of parametric vibration in Harmonic driver, a test device has been developed for the measurement of torsional vibration. The dynamic characteristics can be confirmed through signal processing on torsional vibration. An engineering example is given to illustrate that the manufacturing defect can be on-line diagnosed in Harmonic driver by using the characteristic of bi-spectra. As a result, the magnitude of torsional vibration is eliminated to one half of the original case through the reassembly process, and one of the mechanical performances, i.e., the property of torsional vibration-speed, is improved obviously. The dynamic characteristics caused by time-varying stiffness, i.e., bi-spectra, can be used as a new clue of manufacturing quality assurance for Harmonic driver
Modelling of transient and steady-state modes of a vertical rotor with an automatic balancing device
Full text linkThe authors of the study work out the differential equations of motion of a vertical rotor model on an elastic-dissipative suspension, balanced by a ball-type automatic balancing device. Often, the cross-section of the cavity of the body of the automatic balancing device is rectangular and during rolling the balls have two points of contact, in one of which the balls slide along the surface of the cavity. To prevent the balls from sliding, the inner surface of the cavity of the automatic balancing device is made in the shape of a torus, which provides one point of contact. The forces of gravity and the forces of resistance to the movement of the correcting weights are taken into account, and the model is drawn up for both viscous and dry friction forces inside the body of the automatic balancing device. The obtained mathematical model of the rotor makes it possible to study the transient and steady-state modes of motion of the rotor system
Impact coefficient analysis on long-span beam bridge
Full text linkThis paper presents a numerical study on the impact coefficient calculation of a straight-line π-shaped composite beam and a curved box girder beam. A numerical model of vehicle-bridge coupling system is established, where the random irregularity of bridge surface is considered in the model. The effect of lane numbers, bridge surface flatness, vehicle speed, vehicle weight and primary beam stiffness on the impact coefficient are considered. The results indicate that the lane numbers have certain influence on the impact coefficient; the impact coefficient presents nonlinear increment as the bridge surface flatness becomes from grade A to grade D; the vehicle-bridge coupling system can resonate at both low speed and high speed; the vehicle weight has little influence on the impact coefficient; whilst the displacement impact coefficient is decreased with an increment in the primary beam stiffness. Besides, the local and global impact coefficients, the displacement, moment and shear force impact coefficients are also comprehensively discussed
Toltén Bridge’s response under extreme conditions analysis through numerical models
Full text linkThis article presents the structural health analysis of a full-scale vehicular bridge, using a twin model calibrated with experimental information. This structure consists of concrete arches, built more than 80 years ago, and reinforced in the 1990s with a steel structure. Different load combinations were evaluated in this model to determine the strength of the structure according to current design standards. Finally, it was found that several of its components do not meet the current design requirements, putting the structure in a vulnerable condition to seismic hazards and restricting its service to traffic loads
Casing vibration signal characteristic extractions and applications in rolling bearing
Full text linkA method of combining autocorrelation function with cyclostationary theory and Hilbert envelope analysis is proposed and applied to extract characteristic frequency of rolling bearing. Meanwhile, mean power ratio is calculated and used to identify the fault types of aero-engine rolling bearing based on single-channel casing vibration signal. To verify the effectiveness of proposed method, a comparing analysis is carried out between traditional studies and proposed new method. Furthermore, the influences on the extraction of characteristics and calculation of mean power ratio are taken into account, including the ones of sensor installation position, fault types, type of experiment rigs, failure mode and rotational speed of rolling bearing. The result shows that the proposed method can diagnose running conditions and identify fault types of rolling bearing accurately and effectively just by single-channel casing vibration signal
Research on fault diagnosis of rolling bearings based on conditional variance statistic and cross-correlation spectrum
Full text linkIn this paper, relationships between conditional variance statistic and the center frequency as well as the bandwidth of the filter are researched, and we find that conditional variance statistic is suitable for selecting the center frequency of the filter, but undesirable for selecting the bandwidth. Meanwhile, considering that the traditional iterative way to select the optimal resonance frequency band will be affected by the step size, we choose to fix the bandwidth at five times fault characteristic frequency, then Whale Optimization Algorithm (WOA) is utilized to select the optimal center frequency so as to give consideration to both computing efficiency and accuracy of the selection of center frequency. To further suppress the in-band noise, the filtered signal is analyzed by high order energy operator, and the optimal two energy operators are chosen based on Fault Characteristic Index (FCI) for cross-correlation spectrum analysis. Simulation and experimental results indicate that the proposed algorithm can extract the fault feature of rolling bearings under strong background noise effectively
The shock absorption efficiency of the newly developed neutral equilibrium mechanism in building
Full text linkWhen a structure is hit by an earthquake, the resultant dynamic amplification threatens the safety of the structure. To counteract the seismic force and also reduce structural deformation, a control force, which requires a huge actuator, can be exerted. To avoid the use of excessively large actuators, the power capacity of the actuator needs to be reduced. To overcome these problems, the Neutral Equilibrium Mechanism (NEM) has been developed. The NEM can achieve changes in control with minimal output. The test results of the NEM confirm the following: 1. The total strength of the inner spring is equal to the total strength of the main control spring. 2. The deformation of the main control spring is zero when the angle of the linkage is zero. 3. When the angle of the linkage is +/–90 degrees, the deformation of the inner spring is zero. Considering time delay, the results of analysis show the following: 1. The time delay should be controlled to less than 0.020 seconds, and this mechanism can exert an excellent structural displacement reduction effect. 2. Comparison of the unbalanced force, the maximum output power and the maximum control power of the NEM to those of the direct control method under the same control parameters shows that when the time delay is 0.001 seconds, the unbalanced force of the NEM is only 1/230 and 1/236 of the maximum control force and the maximum output power of direct control respectively. 3. When the time delay is 0.005 seconds, the unbalanced force of the NEM is only 1/150 and also 1/150 of the maximum control and maximum output power of direct control respectively; 4. When the time delay is 0.010 seconds, the unbalanced force of this mechanism is 1/85 and 1/80 of the maximum control force and the maximum output power of direct control. The advantages of the NEM are that the control effect of a building with the NEM under a small unbalanced force and the maximum output power of a small NEM can achieve the same control effect of direct control under the same control parameters
The influence of structural configurations and operating speeds on the sorting arm during high frequency reciprocating operation
Full text linkUnder high-frequency reciprocating operation, the dynamics of the sorting arm are different between operating status and standstill status. First of all, the energy of inertial impact and frequency band depend on the actual motion state, which are closely related to the dynamics of the arm structure. Secondly, during the high-frequency reciprocating operation, the positions of sorting arm change, which causes its configurations changes. At the same time, the acceleration and deceleration in each stage of operation are also inconsistent. These factors make the vibration of the sorting arm structure more complicated. Therefore, the dynamics of the sorting arm mechanism must be analyzed under the actual operating conditions. The paper takes the sorting arm of LED chip sorter as the research object, and it is pointed out that the sorting arm structure has the characteristics of multi-mode high-low frequency during operation. However, the structural configurations and operating parameters of the sorting arm are the main influencing factors of its vibration, which have different characteristics of the high-low frequency response. In this paper, the use of sequential sub-section design to determine the configurations and the corresponding time-series during the operation. Through the analysis of multi-mode frequency response of the sorting arm, the characteristics of high-low frequency range corresponding to the two kind of work excitation are obtained. This paper verifies that the dynamics of the sorting arm are affected by the excitation of structural configurations and the excitation of operating speed during high-speed operation. The laws of high-low frequency response of the sorting arm under different operation parameters and configurations are found out, which provides guidance for the vibration suppression of the sorting arm under operation
Study of anti-swing control of ship cranes based on time delay feedback
Full text link2 tons 3 meters ship crane as the research object, establish the complete mathematical model of ship crane, and design the time-delay feedback control algorithm to eliminate payload swing on the basis of the built mathematical model. First, a high-precision potentiometer is used to measure the in-plane and out-of-plane oscillation of the payload. Measuring devices for the rotary angle and variation amplitude angle are created, and the anti-swing control hardware system is built by the sensing unit and the High-Speed Data Acquisition hardware system. Secondly, the control software on the VB platform is developed using the time-delay feedback algorithm. Experimentally study the effect of time-delayed feedback controller on payload swing elimination, and use induction method to get the optimal control parameters of the time-delayed feedback control algorithm. At last, the AMEsim-ADAMS co-simulation platform was built to evaluate the payload sway of the ship crane under simulated working conditions. The results show that: the hardware and software systems for anti-swing control built-in the paper can give the real-time and the exact payload swing angles. The method of adding time-delay feedback control signal to the slewing operation signal can achieve better anti-swing effects than the others. At the same time, the delayed feedback control algorithm still has a nice control effect in the case of virtual ship deck motion