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Vibration measurements for copper ore milling and classification process optimization
Get PDFThe paper presents a new approach to optimize the comminution process by using accelerometer measurements of the mill shell. An installation performed in the KGHM Polska Miedź Division – Ore concentration Plant Lubin – one of the largest producers of copper and silver in the world – has been used. It is shown that the measurements are correlated with the lithological structure of the ore, and they can be used in a control system to improve effectiveness of the milling and classification processes
Identification of second-order kernels in aerodynamics
Get PDFVolterra series is one of the powerful system identification methods for representing the nonlinear dynamic system behavior. The methods of step response and impulse response are commonly applied to a discrete aerodynamic Computational Fluid Dynamic (CFD) to identify the first- and second-order Volterra kernels. A critical problem, however, is the difficulty of identifying the second-order Volterra kernels correctly in CFD-based method. In this paper the second-order Volterra kernel function is expanded in terms of Chebyshev functions to reduce the size of the problem and the accuracy of the identification is also improved based on a third-order reduced model of Volterra series
Vibroacoustic symptom of the exhaust valve damage of the internal combustion engine
Get PDFModern vehicles are equipped with highly developed electronic computer systems allowing diagnostics of control system elements, but – notwithstanding – deprived of the diagnostic function of purely mechanical defects. The reason of this situation is less and less number of breakdown vehicles. However, mechanical defects still occur, which is confirmed by the information from car repair workshops, and their too late finding increases repair costs. From the economic point of view, supplementing computer systems with diagnostics functions seems justified. The existence of such gap was the reason for undertaking several active experiments, aimed at explaining whether there is a possibility of improving the existing systems by an additional diagnostics function. The results of the possibility of applying quantitative estimation measures of the selected vehicle state are presented in the paper. Directions of further investigations and stages of diagnostic experiments, which would confirm the effectiveness of the proposed measures are provided in the hereby paper. This paper also constitutes the attempt of answering the question whether the similar algorithm application is possible in vehicles of the newest generation, equipped with adaptive systems of on board diagnostics
Experimental characterization of gear-rattle in a quick-return mechanism
Get PDFGear rattle in a quick-return mechanism is studied. Rattling is characterized by experimental work in a mechanical system with two gears driven by an electric motor. The acceleration of the mechanical vibrations and the variations in the electrical current of the motor were measured by means of sensors connected to a data acquisition system. The results obtained are presented in time-domain plots, and analyzed in the frequency domain by power spectra. It is shown that rattling is well identified in the time-domain plots for both parameters, while it is only evident in the motor electrical current signal in the frequency-domain analyses
An analysis of the equipotential surface waves of the Earth’s gravity field
Get PDFA detailed analysis is performed on the influence that the celestial bodies have on the equipotential surface of the Earth’s gravity field. The necessary background is developed in order to progress a new more intelligent methodology of estimating the influence that the celestial bodies have on the geodetic measurements. Previous studies demonstrate that this impact strongly depends on the elasticity of the solid Earth. It is also unequal on different equipotential surface waves. Some results of current investigations are presented, which demonstrate the waves of the Earth’s gravity field influenced by the celestial bodies. The assessment of changes in an equipotential surface is required when reducing the measurement data into a common coordinate system of a definite epoch
On an inline conveyor resonantly driven by piezoelectric actuators
Get PDFThis paper aims to propose a novel inline conveyor driven resonantly by piezoelectric actuators, such that its advancing distance can be maximized, and the energy consumption can be reduced. First, the proposed conveyor is presented, and its operating principle is addressed. Then, the optimal dimensional synthesis of the conveyor is conducted. Furthermore, the approaches for resonance analysis and modal analysis by using ANSYS software are presented. In addition, a design example is given for illustration, and a motion simulation with resonance input is conducted by using ADAMS software. Finally, experiments are carried out to verify the effectiveness of the proposed design. The result shows that the advancing distance of the conveyor operating at the resonance frequency can be significantly increased. Therefore the required energy could be reduced
Research on source location of micro-seismic event based on dynamic cluster velocity model
Get PDFA new velocity model based on dynamic cluster was proposed in this paper. During the process of iteration, the sensors can be formed a cluster according to the velocity similitude degree. Based on the assumption that the speeds from source to each sensor in the same cluster are equal, the corresponding objective function was proposed to solve the source location, which didn’t include the velocity parameter. It not only avoided the error from field measurement and the inversion, but also appropriated for the actual situation that the speeds from every source to different sensors are different. By analyzing 24 different cases, the positioning accuracy based on the velocity model proposed in this paper was verified to be preferable and stable, no matter the source is within the region of the sensor’s array or not. Even for the cases of different velocity variation ranges, the velocity model was still reliable.
A new nonlinear longitudinal vibration model of belt driving system applied in energy saving
Get PDFA belt driving system (BDS) of beam pumping unit is of the following characteristics: 1) energy can flow bidirectional freely; 2) the equivalent rotational inertia is a function of the pulley angle and the stiffness is a function of time. Take account of the above characteristics, a new mathematical model of nonlinear longitudinal vibration is built for BDS. The nonlinear relationship between the equivalent rotational inertia and driven-pulley angle as well as the equivalent stiffness and slipping angle is obtained. Comparing experiment results with simulated results, good agreement is found, which shows the simulation model is feasible. The amplitude-frequency curves are given, which show the jumping phenomenon. In addition, the amplitude-frequency curves are very sensitive to the system parameters, such as Young’s modulus, the preload force, the rotational inertia and load torque. In the details, with increasing Young’s modulus as well as decreasing the preload force, the jumping phenomenon moves the high frequency region, and the amplitude-frequency curves of the system move their mutational direction with load torque increasing. The jumping phenomenon of equivalent stiffness suggests that the jumping phenomenon of steady-state response of the pulley is influenced by the nonlinear dynamic stiffness of the belt. Real application indicates that the system energy consumption is increasing with the preload force decreasing, and it is also increasing with the load torque increasing. Therefore, the simulation analysis of nonlinear longitudinal vibration of BDS plays an important role in understanding the effects of the system parameters on the nonlinear steady-state response and saving energy by parameter optimization in practical application
Experimental investigation of the vibration transmissibility of a magnet-spring vibration isolator under random excitation
Get PDFA magnet-spring vibration isolator comprised of several magnets and mechanical springs has been proved to be highly effective for overcoming the major limitation of a conventional linear vibration isolator in such a way that the stiffness of the isolator is sufficiently large to hold the weight of a load, but becomes much softer under dynamic motion. The vibration transmissibility of this magnet-spring vibration isolator is usually examined using a sinusoidal excitation with a specific frequency because the system is nonlinear. In this paper, the isolation performance of the magnet-spring vibration isolator is further investigated experimentally for the case of random base excitation. The experimental results are compared with the cases of sinusoidal excitation obtained by computer simulations considering both jump-up and jump-down transmissibility curves. The results are interesting: the vibration isolation performance improves as the RMS (Root Mean Square) amplitude of the random base excitation increases; the experimental vibration transmissibility curve of the random excitation is bounded by the jump-up transmissibility curve of the corresponding sinusoidal excitation case
Noise and vibration assessment of permanent-magnet synchronous motors based on matching pursuit
Get PDFThis paper presents a noise and vibration assessment scheme for the elevator permanent-magnet synchronous motors (PMSMs) based on matching pursuit (MP) with carefully selected atoms. The atomic dictionary is developed by considering of the complication of electromagnetic noise and vibration of the elevator PMSMs. After identifying the natural frequencies by modal testing and computing the characteristic electromagnetic frequencies of the PMSMs, the impulse energy ratio based on transient components, which are extracted by projecting on the selected atoms based on the MP method, are computed and used to assess the machines. The assessing results indicate that the transient components can accurately represent the electromagnetic impulse since the distorted magnetic fields and the features are robust for quality inspection of the elevator PMSMs