The study deals with stability and dynamic problems in bar structures using a probabilistic approach. Structural design parameters are defined as deterministic values and also as random variables, which are not correlated. The criterion of structural failure is expressed by the condition of non-exceeding the admissible load multiplier and condition of non-exceeding the admissible vertical displacement. The Hasofer-Lind index was used as a reliability measure. The primary research tool is the FORM method. In order to verify the correctness of the calculations Monte Carlo and Importance Sampling methods were used. The sensitivity of the reliability index to the random variables was defined. The limit state function is not an explicit function of random variables. This dependence was determined using a numerical procedure, e.g. the finite element methods. The paper aims to present the communication between the STAND reliability analysis program and the KRATA and MES3D external FE programs.
Anisotropic rotor configurations influenced by the presence of a large number of geometrical parameters in a permanent magnet assisted synchronous reluctance (PMASR) motor pose design challenges in obtaining a robust geometry satisfying the requirements of reduced torque ripple and high torque density. Therefore, the purpose of this work is to perform detailed geometrical sensitivity analysis of a 36 slot/4 pole permanent magnet assisted synchronous reluctance (PMASR) motor using h-indexing and level sensitivity analysis in order to specify a guideline for designers to prioritize the design variables for optimization. Systematic multi-level design optimization for multiple objectives is implemented by an NSGA-II algorithm aided by the finite element analysis tool, hardware prototyping and experimental validation. The optimized designs also exhibit better structural and thermal characteristics.
In this paper, the sensitivity analysis of the elliptic filters realized by using biquadratic structures was carried out. The influence of spread the structure parameter values on the shape of the frequency characteristic of the filter transmittance modulus was analyzed. The analysis was limited to the case of even order low-pass filter. Defining the proper class of the sensitivity coefficients, the changes influence of individual structure parameters on the deviation of basic parameter values of the characteristic was considered. The considerations were illustrated by the numerical example.
The paper presents definitions and relative measures of the system sensitivity and sensitivity of its errors. The model of a real system and model of an ideal measuring system were introduced. It allows to determine the errors of the system. The paper presents also how to use the error sensitivity analysis carried out on the models of the measuring system to the correction of the nonlinearity error of its static characteristic. The corrective function is determined as a relation between the input variable of the tested system and its chosen parameter. The use of the proposed method has been presented on the example of a phase angle modulator. The obtained results have been compared with the results of analytic calculations. The idea of a phase angle modulator is also presented.
The first order variation of critical loads of thin-walled columns with bisymmetric open cross-sectiondue to some variations of the stiffness and location of bracing elements is derived. The con-siderations are based on the classical linear theory of thin-walled beams with non-deformablecross-section introduced by Vlasov . Both lateral braces and braces that restraint warping andtorsion of the cross-section have been taken into account. In the numerical examples dealing withI-column, the functions describing the influence of location of the braces with unit stiffness on thecritical load of torsional and flexural buckling are derived. The linear approximation of the exactrelation of the critical load due to the variation of the stiffness and location of braces is determined.
Accurate force and torque calculations are fundamental to being able to predict the operation of an electromechanical device or system. The Maxwell stress tensor and the virtual work principle are the two major theories for force and torque calculation. However, if local distributions of torque are needed to couple to structural and vibration analyses, the conventional Maxwell stress approach cannot provide this easily. A recently developed approach based on sensitivity analysis has the capability to deliver local stress and torque as well as accurate global results. In addition, this approach divides the total torque into different components which are essential to the design of electrical devices. This paper includes several numerical examples of torque calculations of different electrical machines. The results are verified by a commercial software package using the Maxwell stress based force calculation.
The purpose of the present research relates to the sensitivity analysis of road vehicle comfort and handling performances with respect to suspension technological parameters. The envisaged suspension being of semi-active nature, this implies first to consider an hybrid modeling approach consisting of a 3D multibody model of the full car - an Audi A6 in our case - coupled with the electro-hydraulic model of the suspension dampers. Concerning parameter sensitivitie, the goal is to capture them for themselves - and not necessarily for optimization purpose - because their knowledge is of a great interest for the damper manufacturer. An important issue of the research is to consider objective functions which are based on complete time integrations along a given trajectory, the goal being - for instance - to quantify the sensitivity of the carbody rms acceleration (comfort) or of the vehicle overturning character (handling) with respect to suspension parameters. On one hand, the accuracy of the various partial derivatives computation can be greatly enhanced thanks to the symbolic capabilities of our ROBOTRAN multibody program. On the other hand, the computational efficiency of the process also takes advantage of the recursive formulation of the multibody equations of motion which must be time integrated with respect to both the generalized coordinates and their partial derivatives in case of the so-called direct method underlying sensitivity analysis.
In the paper, a general topology of continuous-time Active-RC filter is presented. The model includes all possible Active-RC filter structures as particular cases and allows us to analyze them using a unified algebraic formalism. This makes it suitable for use in computeraided analysis and design of Active-RC filters. By its construction, the model takes into account the finite DC gain and the finite bandwidth as well as non-zero output resistance of operational amplifiers. Filters with ideal OPAMPs can be treated as particular cases. Sensitivity and noise analysis of Active-RC filters is also performed in the proposed general setting. The correctness of the model is verified by comparison with SPICE simulation.
The area of environmental protection concern minimises the impact that technical objects have on the environment. Usually the most effective way of protecting the environment is to influence the source of the problem. For this reason studies are conducted to modify the construction of machines, power machines in particular, so as to minimise their impact on the environment. In the case of environmental protection from noise it is most convenient to carry out measurements in an anechoic chamber. Unfortunately, this is possible only in very limited circumstances. In all other cases measurements are performed using an engineering method or the survey method, both of which are described in the standards and by taking into account the so-called environmental corrections. The obtained results are burdened with greater error than those of measurements in an anechoic chamber. Therefore, it would seem advantageous to develop a method of obtaining similar and reliable results as those in an anechoic chamber, but in a reverberant field. The authors decided to use numerical modelling for this purpose. The main objective of this work is a comprehensive analysis of the numerical model of a laboratory designed for acoustic tests of selected power machines. The geometry of a room comprising an area of analysis is easy to design. The main difficulty in modelling the phenomena occurring in the analysed area can be the lack of knowing the boundary conditions. Therefore, the authors made an attempt to analyse the sensitivity of various acoustic parameters in a room in order to change these boundary conditions depending on the sound absorption coefficient
This paper describes multiple electric field control methods for foil coils in high-voltage coreless linear actuators and their sensitivity to misalignment. The investigated field control methods consist of resistive, refractive, capacitive and geometrical solutions for mitigating electric stress at edges and corners of foil coils. These field control methods are evaluated using 2-D boundary element and finite element methods. A comparison is presented between the field control methods and their ability to mitigate electric stress in coreless linear actuators. Furthermore, the sensitivity to misalignment of the field control methods is investigated.
This work deals with the inverse problem associated to 3D crack identification inside a conductive material using eddy current measurements. In order to accelerate the time-consuming direct optimization, the reconstruction is provided by the minimization of a last-square functional of the data-model misfit using space mapping (SM) methodology. This technique enables to shift the optimization burden from a time consuming and accurate model to the less precise but faster coarse surrogate model. In this work, the finite element method (FEM) is used as a fine model while the model based on the volume integral method (VIM) serves as a coarse model. The application of the proposed method to the shape reconstruction allows to shorten the evaluation time that is required to provide the proper parameter estimation of surface defects.