Mechanics and Control
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ISSN 2083-6759
e-ISSN: 2300-7079
Issue Date
2011
Volume
Vol. 30
Number
No. 2
Description
Journal Volume
Mechanics and Control
Vol. 30 (2011)
Projects
Pages
Articles
NARX model in rotating machinery diagnostics
(2011) Bednarz, Jarosław; Barszcz, Tomasz; Uhl, Tadeusz
Rotating machines are often described using linear methods with acceptable accuracy. Some malfunctions, however, are of non-linear nature. The most common examples of those malfunctions are loose bearings and rotor rubs. Accurate detection and identification of such malfunctions requires more accurate methods. One of such methods can be NARX - nonlinear systems identification. This method is based on neural networks approach and is especially efficient in modeling and diagnostics of nonlinear systems. Application of this method leads to shorter and less costly tuning of the model to the object, which is the key requirement when practical application of a method is concerned. The paper presents how NARX can be applied for modeling of rotating machinery malfunctions. Idea of the diagnostic algorithm based on such modeling is presented. The proposed algorithm was verified during research on a specialized test rig, which can generate vibration signals. The paper also presents results of an application of the NARX method for data collected at a wind turbine.
Applying neural network in computing filling coefficient of four-stroke internal combustion engine
(2011) Bera, Piotr
Neural networks consist of many simple elements operating in parallel. In supervised training they are capable of finding their own solution to a particular problem, given only examples of proper behavior. It is a very useful method of solving complex, non-linear problems. The following article discusses the usage of artificial neural network to compute the value of filling coefficient of four-stroke internal combustion engines as the function of crankshaft rotational speed and throttle opening angle. The paper presents the idea of a static, two-layer feedforward network trained with the basic backpropagation algorithm in which the weights and biases are updated in the direction of the negative gradient. The article discusses network architecture and data structure, training parameters and result analysis.
Modelling of amplitude-selective-damping valves
(2011) Gołdasz, Janusz P.
The so-called amplitude-selective-damping (ASD) valving is a relatively new approach for modifying the output of a hydraulic shock absorber. In the automotive industry ASD valves are known to improve isolation from road inputs. During more aggressive maneuvers the systems maintains the performance of a standard (non-ASD) shock absorber. In the paper, the author derives and analyzes a fairly complete state-space model of an exemplary piston-side ASD valve. The model includes key geometric and performance characteristics of the valve. The results are shown in the form of phase plane plots of force-displacement diagrams, respectively, for a twin-tube shock absorber configuration of choice.
An uncertainty analysis for developed measurement vision system aided by numerical simulations
(2011) Holak, Krzysztof; Kohut, Piotr; Martowicz, Adam; Uhl, Tadeusz
The paper presents an optical non-contact method of measuring the static deflection structure in one plane. Displacements of measurement points of the structure under the load were computed by means of digital image correlation coefficient. The application of homography mapping enabled the deflection field to be computed from two images of the structure acquired from two distinct points in space. The model of the developed vision system were implemented and simulated in the MATLAB programming tool. The impact of the corner detector inaccuracy on the measurement results was investigated. The uncertainty propagation of the developed method was examined in a series of simulations. The distance of the camera and the focal length were investigated parameters of the system. In the paper, the variability of homography components as well as variability of displacements measured in each of the points of interest are presented.
Impact of damages to welded joints in bases of powered roof supports on the operational safety
(2011) Jaszczuk, Marek; Markowicz, Józef; Szweda, Stanisław
The location and variation range of the length of damaged welds was determined on the grounds of test results on the type and size of damages to welded joints in powered roof support bases destined for repair. In the analysis of the effort of components of roof supports modeled by means of the finite elements method the impact of the length of the damages to the welds on the maximal value of reduced stresses was estimated. Cases of symmetrical and asymmetrical load used on stand tests were discussed. Due to local plasticitization of the base steel plates occurring in the course of the torsion test, elasticity and plasticity material properties were considered in the MES. Examples of designating the limit value of the length of the damaged weld at which the powered roof support maintains its operational safety were presented.