Journal of Vibroengineering
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Study on an elastic lever system for electromagnetic energy harvesting from rail vibration
Get PDFEnergy harvesting from rail vibration is a promising approach to solve the power supply problem in remote and off-grid areas. The major issue of current energy harvesting techniques and devices is the limited power generating capacity. In this paper, the authors put forward an elastic lever system to enhance the performance of an electromagnetic energy harvester. A vehicle-track coupling dynamics model is established to simulate the service condition of the energy harvester. The Power Amplification Factor (PAF), which is defined as the ratio between the output power with and without a lever system, is introduced to quantify the Enhanced Energy Harvester (EEH). It is found that the PAF can be greater than n2 with a leverage ratio of n. Simulation shows that the output power can be magnified by 430 times with an elastic lever system with a leverage ratio of 10. The amplification effect of the output power comes from two aspects, one is the magnifying effect of leverage itself and the other is the resonance effect. Additionally, it is found that a single EEH will increase the wheel-rail contact force slightly, which indicates the EEH is impractical for use as an approach for rail vibration reduction. Nevertheless, it will not have a significant negative effect on rail vibration
Utilizing the time delayed PPF controller to suppress vibrations of a nonlinear system containing real power exponents in damping and restoring forces
Get PDFThe time delayed Positive Position Feedback (PPF) controller is utilized to suppress the primary resonance of vibrations of an excited base oscillator by real power exponents of the restoring and damping forces. Multiple scales method is conducted to get the frequency response equations. The stability of the system is studied by using the Lyapunov first method. The influences of system parameters and time delay on the system response are investigated to avoid the jump phenomenon for better system performance. Time margin is deduced for most possible values of controller gain. Analytic results are verified by numerical integration of the original system equations
A novel hybrid topology for power quality improvement using multilevel inverter for the reduction of vibration and noise in brushless DC motor for industrial applications
Get PDFThe proposed research involves the design and implementation of a novel hybrid Topology for Power Quality Improvement using Multilevel Inverter to reduce vibration and noise in BLDC motor for industrial applications. The utility of power electronics device plays a vital role for various applications in recent days. Similarly, the power consumption is also important for all processing units. The power electronic devices contain a lot of converters for processing the energy. During such cases, the harmonics are produced in different ways. Hence, a system analysis is necessary to find the problem at conventional methods. Hence the problem is identified on the distribution static compensator (DSTATCOM) component module whose harmonics are high, and it is important module for the circuit, hence preventive action to be taken to reduce the harmonics. To limit or reduce the harmonics, it is required to modify the triggering mechanism and control unit of Multi level inverter. Hence, the proposed hybrid method is implemented with the developed H-bridge and diode clamped topology with a brushless dc motor. In addition, the vibrations and the noise level are also reduced due to the reduced total harmonic distortion. The proposed module is simulated on MATLAB Simulink, and an experimental analysis is carried out to verify functionality tools with various operating conditions, the proposed method proves more efficient than the switches and complex networks present in traditional methods
Stochastic P-bifurcation in a tri-stable Van der Pol system with fractional derivative under Gaussian white noise
Get PDFIn this paper, we study the tri-stable stochastic P-bifurcation problem of a generalized Van der Pol system with fractional derivative under Gaussian white noise excitation. Firstly, using the principle for minimal mean square error, we show that the fractional derivative term is equivalent to a linear combination of the damping force and restoring force, so that the original system can be transformed into an equivalent integer order system. Secondly, we obtain the stationary Probability Density Function (PDF) of the system’s amplitude by the stochastic averaging, and using the singularity theory, we find the critical parametric conditions for stochastic P-bifurcation of amplitude of the system, which can make the system switch among the three steady states. Finally, we analyze different types of the stationary PDF curves of the system amplitude qualitatively by choosing parameters corresponding to each region divided by the transition set curves, and the system response can be maintained at the small amplitude near the equilibrium by selecting the appropriate unfolding parameters. We verify the theoretical analysis and calculation of the transition set by showing the consistency of the numerical results obtained by Monte Carlo simulation with the analytical results. The method used in this paper directly guides the design of the fractional order controller to adjust the response of the system
Ultimate bearing capacity of circular shallow foundations in frozen clay
Get PDFThis paper presents a study on the ultimate bearing capacity of circular shallow foundation in frozen clay. The bearing capacity were determined by model test, numerical simulation and analytical solution. In numerical simulation, the temperature field considering the phase transition was transformed into a temperature load and applied to a three-dimensional solid model. The generalized Kelvin model was used to describe the creep of frozen clay, and step loading was used. Based on the tests results that frozen soil fails because of local shear, we proposed an analytical model to estimate the ultimate bearing capacity of circular shallow foundation with local shear failure mechanisms. Based on the limit equilibrium theory, it was assumed that the fracture plane of the model only develops to the boundary between the transition zone and the passive zone. The results from present study and some other method are presented and compared, which has shown and verified the feasibility of our method. And the analytical solution is in good consistent with the results of the model test and numerical simulation
Transmission characteristics of planetary gear wear in multistage gear transmission system
Get PDFGear tooth surface wear is a common failure mode. It takes a long time and can cause other major faults. The wear fault signal is weak and hard to identify. This paper reveals the transmission characteristics of the planetary gear wear and the relationship between multistage gear meshing through the transmission characteristic analysis. Taking the multistage gear transmission system fault simulation test rig as the research object, a three-dimensional solid rigid-flexible coupling model of the system was established. The contact force signals from each pair of gears in the state of planetary gear wear were obtained by dynamic simulation. The test signals of the fixed-axis gearbox and planetary gearbox were obtained under normal and planetary gear wear states. Comparing the transmission characteristics of the system under normal and planetary gear wear states, the vibration mechanism of the wear fault and the correlative characteristic between gearboxes were revealed
Bearing degradation assessment based on entropy with time parameter and fuzzy c-means clustering
Get PDFBearings are one of the most crucial elements in rotating machine. The condition of bearings decides the operation of machine. Consequently, it is necessary to study the assessment of bearing degradation in order to develop condition-based maintenance. This paper improves an indicator based on entropy which is calculated by wavelet packet decomposition and auto-regressive model. By introducing time parameter, the indicator solves the problem of instability in the initial stage of operation and it is less influenced by the operational conditions. Then, fuzzy c-means clustering can evaluate the process of degradation. Moreover, it can provide the threshold adaptively and help to repair by unit replacement. To ensure the applicability, the data of this paper comes from two laboratories, FEMTO-ST Institute and Intelligent Maintenance System Center. The result indicates that the method is effective to assess bearing degradation process
Ground vibration propagation and attenuation of vibrating compaction
Get PDFWhen a high-power vibrating roller compact the subgrade, the vibration wave will quickly propagate along the surface of the subgrade and generate hazards to surrounding environment and structure. To study the vibration propagation rules of the roller, the vibration acceleration of the high-power vibrating roller was measured on the surface of the rock subgrade, coarse-grained soil subgrade and fine-grained soil subgrade. The respective relations between vibration acceleration and the distance from a vibration source in the vertical, horizontal radial and horizontal circumferential direction have been discovered. The research results show that the vibration peak frequency generated by the vibrating roller on the subgrade approximates vibration frequency. The vibration effective influence distance varies from 10m to14m, and the horizontal radial vibration is greater than that of vertical and horizontal circumferential direction. The vibration of the rock subgrade attenuates the most slowly and propagates the most remotely
Geotechnical monitoring and safety assessment of large-span triple tunnels using drilling and blasting method
Get PDFThe excavation of large-span triple tunnels using drilling and blasting method inevitably causes complicated load transfer effects and induces potentially damaging ground vibrations. In this study, the structural responses (including the surrounding rock pressure, normal-contact pressure between the primary and secondary linings, internal forces in the secondary lining) and the seismic responses (including peak particle velocity and corner frequency), are systematically recorded. It is found that the first-excavated left tunnel is influenced heavily by the excavation of the last-excavated middle tunnel, whereas it is hardly affected by the excavation of the second-excavated right tunnel. The load carried by the primary lining is approximately three times as that carried by the secondary lining. The middle tunnel was in the least desirable state due to the formation of the large Protodyakonov’s equilibrium arch (PEA). Based on timely feedback of the comprehensive monitoring system, a series of vibration-reducing techniques were applied and effectively guaranteed safety during blasting construction. By referring to Chinese codes, the minimum safety factor of the secondary lining is 1.3; the maximum PPV (0.15 cm/s) is lower than the allowable value; and the corner frequency (40-140 Hz) will not cause resonant vibration of the Great Wall
Implementation of standalone dynamic solar array fed permanent magnet synchronous motor drive using zero voltage switching resonant converter for the reduction of switching losses and oscillations
Get PDFThe Proposed research deals implementation of standalone dynamic solar array fed permanent magnet synchronous motor drive using zero voltage resonant switch converter for the reduction of switching losses and oscillations. The closed loop control voltage strategy has been proposed for power flow management between solar photovoltaic (PV), battery, motor load and to maintain constant load voltage to perform continuous MPPT operation of solar PV. For improving the efficiency and to reduce vibration across the load SPV array fed Zero Voltage Switching (DISOZVS) Resonant Converter with permanent magnet synchronous motor (PMSM) drive is proposed. The DISOZVS resonant converter with suitable switching operation accomplishes for the purpose of reducing the Switching losses. The ZVS converter is constructed by a buck-boost circuit, which is operated as a buck circuit when charging and a boost circuit when discharging. So, we can use many power related systems, which improves efficiency, lower losses and higher performance. The various dynamics and oscillations of standalone SPV array is analysed in the proposed research. The performance of the proposed system is simulated in MATLAB/Simulink atmosphere and various parameters outputs are carried. A hardware prototype of the proposed system has been fabricated for the proposed converter and various analysis were incorporated. The working of the proposed scheme for the different levels of input solar insolation and Load power demand has been satisfactorily demonstrated for both simulation and experimental compared to conventional it results more efficient with reduced losses and oscillations