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The concept of transducer for detection of trackway surface condition basing on frictional coupling of wheel with a rail and its experimental verification
Get PDFDescription of design and rules of operation of transducer for detection of trackway surface condition in mine underground workings is the project objective. Information about the surface condition collected with use of the transducer will enable adaptive (depending on track surface conditions) control of breaking torque of wheels of rail locomotives and, in a result, shortening of braking distance by minimization of slippage. At first the requirements for braking systems of mining locomotives, with reference to real conditions of their operation, will be presented. Then selected braking systems, which are applied in the locomotives used in the coal mine industry, will be described with a special attention paid to the solutions, which potentially shorten the braking distance, including also the solutions based on ABS system used in the automotive industry. A concept of dedicated transducer, task of which is a continuous detection of surface condition of trackway, on which the locomotive moves, will be described with reference to the presented solutions. Transducer for detection is based on frictional coupling between its active component (so-called “tracking wheel”) and a rail. Presented concept will be proved by a series of verification experimental tests. Presentation of tests results and determination of further directions of R&D work as regards discussed problems will be the summary of the project
Analysis of the vertical vibration effects on ride comfort of vehicle driver
Get PDFVehicle vibrations affect the health and comfort of the driver and passengers considerably. The aim of this study is to analyze the effects of vertical vehicle vibrations on the driver. To achieve this goal, a human biodynamic model with 11 degrees of freedom was incorporated into a full vehicle model and this combined human-vehicle model was subjected to the road disturbance. After dynamic analysis of the proposed model, root mean square (RMS) acceleration responses of the human body parts over a certain frequency range were obtained. Physiological effects of the vibrations on the human body were analyzed using the criteria specified in International Organization for Standardization (ISO) 2631. Then, in order to observe the effectiveness of a controller on the vibration isolation of human body, sliding mode controller was applied to the model. Comparison of the vibration effects for the uncontrolled and controlled cases of the human-vehicle model was presented. It can be concluded from the results that sliding mode controller considerably reduces whole body vibrations compared with the uncontrolled case and thereby improves the ride comfort satisfactorily
Vibrations, stability and compression of elements of packages made from corrugated board
Get PDFThe paper considers vibrations, stability and compression of a package element made from corrugated board. The analysis is based on a model of a structure consisting from twodimensional beams taking into account the orthotropic properties of the corrugated board. The problem of initial stability was solved and the first eigenmodes of stability were obtained. Performed experimental study allowed to determine the dependence of the vertical compression force on the geometrical parameters of the multilayered board before the development of plastic deformations in the board. The results of investigation are used for the design of package elements
Establishment and safety evaluation of a flexible test platform for the vertical-axis wind turbine
Get PDFThis work intends to construct and execute the safety evaluation of an test platform for the small vertical-axis wind turbine (VAWT), which is mounted on the rooftop of a 60 mheight building. The experiment platform designed here is flexible and suitable for carrying out the systematic performance evaluation on different types of VAWT. The wind turbine performance measurement is conducted by utilizing the data acquisition system. All environmental information and power data from sensors and generator on this platform are recorded and transferred to the computer automatically. Later, these analogy signals are transformed to digital format for transmitting into computer. Also, with the aids of a visual software programming within the framework of LabVIEW, the real-time monitoring on the input/output parameters of generator and the wind condition can be accomplished simultaneously. Afterwards the data processing and in-depth analysis on the experimental outcomes are carried out via the established computer program. Consequently, the on-site performance of the wind turbine generator system is attained in an automatic and systematic manner. Moreover, to ensure for providing sufficient data and its accuracy, statistic concept is enforced to judge whether the test data are qualified or not in the data-processing procedure. Regarding the safety evaluation of wind turbine on this test platform, the numerical models of wind turbine and platform are analyzed via ANSYS Workbench to obtain the forces exerting on the main shaft and blades. This force distribution can be analyzed for checking if they can stand and meet the safety criterion under various wind speeds. Furthermore, a 2 m-diameter, multiblade vertical-axis wind turbine (MVAWT) is installed as a demonstrating case of the entire procedural test. Firstly atmospheric parameter, such as wind velocity, wind direction, air temperature, and air pressure is measured based on IEC 61400-12 standard on the rooftop of building for one year range measurement time. By collecting and observing the wind parameter data, such as mean wind velocity and wind direction distribution, the wind energy estimation of this MVAWT can be analyzed quantitatively. In summary, together with the data-acquisition software programmed under the framework of LabVIEW, this experimental system can provide the capability for monitoring, recording, and filtering these test data in an rigor manner, and is appropriate for executing the R&D and performance evaluation on different VAWTs
On the approximate analytical solution for parametrically excited nonlinear oscillators
Get PDFIn this study we have analytically analyzed the vibration of parametrically excited oscillators based on Mathieu-Duffing equation. He’s Variational iteration method (VIM) is applied to obtain analytical solution, while Runge-Kutta method is used to obtain the numerical solution. It is demonstrated that VIM is very effective and convenient therefore may find wide applicability in engineering and other sciences. Finally, to confirm the validity of the applied method, the results of VIM are compared with those obtained by Runge-Kutta method. The results from VIM indicate an excellent agreement with the numerical solutions
Wood products automatic identification based on fingerprint method
Get PDFThis paper introduces utilization of improved fingerprint method based on wood surface visual parameters for increasing wooden products identifiability for instance in wood industry and especially for automation lines. Usually the traceability of the objects in the production chain is achieved by using identification code based systems, for example visual codes, which are marked in one position and are read by a machine vision system in another position. In many cases the possible maximum readability can be quite hard to achieve due to marking problems or code background visual problems. In wood industry traceability case it is possible to exploit the fact that wood is a biological material and therefore its surface is quite volatile, each code background is unique. The parameters describing the wood branches, grain or some other specific features can be used for matching for example the saw material in different production line positions. Presuming the conditions for the vision system in the consecutive positions are similar and no processing is applied to the traceable objects between those positions, then it is possible to match most of the objects and therefore increase automatic traceability and identification of the products in different positions of the production chain
A joint stiffness identification method based on finite element modeling and frequency response functions
Get PDFAccurate finite element (FE) modeling of mechanical structures is extremely difficult with unknown joints or boundary conditions. An alternative joint stiffness identification method that involves a hybrid of FE model and frequency response functions (FRFs) is presented. Firstly, the joint stiffness is assumed by experience and the mechanical structure is modeled with the FE method. Secondly, the FRFs at the concerned nodes of the structure are simulated and measured, respectively. Then the norm of residual FRFs between the simulations and measurements is calculated. Finally, a sensitivity-based iterative algorithm is derived for minimizing the norm of residual FRFs and the least square method is used to solve over-determined iterative equation. The joints stiffness parameters are identified through the iteration process, while the FE model is updated simultaneously. The proposed joint stiffness identification method is applied on a clamped beam assembly. The first three natural frequencies calculated by the FE model are compared with the measured values. The largest relative error of the simulation deceases from 16.7 % to 2.5 % after the joint stiffness parameters are identified, which demonstrates the effectiveness of the presented method
A new density estimation neural network to detect abnormal condition in streaming data
Get PDFAlong with the development of monitoring technologies, numerous measured data pour into monitoring system and form the high-volume and open-ended data stream. Usually, abnormal condition of monitored system can be characterized by the density variation of measured data stream. However, traditional density estimation methods can not dynamically track density variation of data stream due to the limitation of processing time and computation memory. In this paper, we propose a new density estimation neural network to continuously estimate the density of streaming data in a time-based sliding window. The network has a feedforward structure composed of discretization, input and summation layer. In the discretization layer, value range of data stream is discretized to network nodes with equal intervals. Measured data in the predefined time window are pushed into input layer and updated with the window sliding. In summation layer, the activation results between input neurons and discretization neurons are summed up and multiplied by a weight factor. The network outputs the kernel density estimators of sliding segment in data stream and achieves a one-pass estimation algorithm consuming constant computation memory. By subnet separation and local activation, computation load of the network is significantly reduced to catch up the pace of data stream. The nonlinear statistics, quantile and entropy, which can be consecutively figured out with the density estimators output by the density estimation neural network, are calculated as condition indictors to track the density variation of data stream. The proposed method is evaluated by a simulated data stream consisting of two mixing distribution data sets and a pressure data stream measured from a centrifugal compressor respectively. Results show that the underlying anomalies are successfully detected
Instantaneous frequency identification of a time varying structure using wavelet-based state-space method
Get PDFThis paper presents a method to identify the instantaneous frequency of the time varying structures based on wavelet and state space methods by using free and forced vibration response data. Firstly, the second-order vibration differential equations are rewritten as the first-order state equations using state space theory. Secondly, both excitation and response signals are projected by the Daubechies wavelet scaling functions. Thus, the first-order state equations are transformed into linear algebraic equations using the orthogonality of the scaling functions. Lastly, the equivalent time varying state space system matrices of time varying structure are extracted directly by solving the linear equations. The instantaneous frequencies are determined via eigenvalue decomposition of the state space system matrices. The proposed identification algorithm is investigated with a four degrees-of-freedom spring-mass-damper model. Numerical simulations demonstrate that the proposed method is robust and effective for identification of the abruptly, smoothly and periodically changing instantaneous frequencies of time varying structures
Evaluation of the natural draught cooling tower shell using linearly and non-linearly numerical analysis
Get PDFThe shell shape of the natural cooling tower determines the sensitivity of the whole structure against wind excitation. This study analyses influence of the tower shell geometric parameters on the structural behavior, evaluated by linearly and nonlinearly numerical analyses. The goal of the study is to give an informative statement for the form-finding process of the cooling tower shell in the engineering practice. The generated 32 towers from an existing cooling tower are linearly analyzed base on the natural frequency. Further three representative models were selected, they were analyzed based on the buckling factor and the reinforced amount required according to a design guideline. The hyperbolic shell with overall radii as small as possible yielded not only a higher first natural frequency, thus less wind-insensitivity, but also a safer buckling behavior and a economical design due to less requirement of concrete and reinforcement. This advantageous structural behavior could be consistently verified in the nonlinear analysis, evaluated by load-deformation curves and damage indices based on the natural frequencies and modal contribution factors