Load and Response Identification for a Nonlinear Flexible Structure Subject to Harmonic Loads

2013 ◽  
Vol 9 (1) ◽  
Author(s):  
Maria Chierichetti
Keyword(s):  
Dynamic Response ◽  
Control Systems ◽  
Numerical Approach ◽  
Reference Points ◽  
Structural Performance ◽  
Flexible Structure ◽  
Complete Structure ◽  
Full Field ◽  
Complete Knowledge ◽  
Load Distributions

Experimental monitoring of dynamic response is generally limited to few locations in the system. However, the analysis of structural performance and design of control systems would benefit from a complete knowledge of the system dynamic during service. A numerical approach is developed to numerically reconstruct the load and response of a complete structure from few reference points, based on a modal approach for projecting the response at few points on the domain of the structure. This methodology is particularly advantageous when full-field monitoring of a structure is not a possible solution. An assembly of two beams joined by a nonlinear torsional spring is analyzed in case of different load distributions acting on its span. The approach is shown to be robust and reliable.

Efficient Response Monitoring of Flexible Structures

2014 ◽  
Author(s):  
Maria Chierichetti ◽  
Vahid Rahneshin
Keyword(s):  
Dynamic Response ◽  
Flexible Structures ◽  
Numerical Approach ◽  
Initial Guess ◽  
Response Monitoring ◽  
Entire Body ◽  
Simple Task ◽  
Full Field ◽  
Flexible System ◽  
Applied Forces

The definition of an accurate model to represent the dynamic behavior of a flexible system has a significant impact on the understanding of its current health. However, due to lack of information on the physical properties as well as complexity of applied loads, accurate modeling is not usually a simple task, and inaccuracies in predicting the response of the flexible structure arise. In this work, a combined experimental and numerical approach, called Extended Load Confluence Algorithm (ELCA), is presented to improve the accuracy in the estimate of the dynamic response using an iterative approach that corrects the initial model. The objective is to accurately estimate the displacements, strains, and accelerations of the entire body. The full-field dynamic response is reconstructed from a limited set of experimental data, with little knowledge about the applied loads. ELCA estimates the state of the structure by defining fictitious applied forces that depend on the error of the estimate. The proposed algorithm is based on an initial numerical model for the prediction of the system s behavior. This model is updated based on a modal expansion of the response in the frequency domain. The algorithm starts with an initial guess of the applied loads and updates them in few iterations in order to match the numerical dynamic response with the experimental measurements at the sensors locations. Numerical and experimental analyses will show the feasibility of the proposed approach. It will be shown that a few sensors are sufficient to represent the overall behavior of the system and ELCA converges in a few iterations.

The Role of Simulation in the Development of a Fast-Actuation Solenoid C.R. Injection System

2004 ◽  
Author(s):  
Gian Marco Bianchi ◽  
Piero Pelloni ◽  
Giovanni Osbat ◽  
Marco Parotto ◽  
Rita Di Gioia ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Control Strategies ◽  
Fluid Dynamic ◽  
Numerical Approach ◽  
Linear Analysis ◽  
Operating Conditions ◽  
System Model ◽  
Injection System ◽  
Multiple Injection ◽  
Pressure Regulator

Upcoming Euro 4 and Euro 5 emission standards are increasing efforts on injection system developments in order to improve mixture quality and combustion efficiency. The target features of advanced injection system are related to their capability of operating multiple injection with a precise control of amount of fuel injected, low cycle-by-cycle variability and life drift, within flexible strategies. In order to accomplish this task, performance must be optimised since injection system concept development by acting on. The extensive use of numerical approach has been identified as a necessary integration to experiments in order to put on the market high quality injection system accomplishing strict engine control strategies. The modelling approach allows focusing the experimental campaign only on critical issues saving time and costs, furthermore it is possible to deeply understand inner phenomena that cannot be measured. The lump/ID model of the whole system built into the AMESim® code was presented in previous works: particular attention was devoted in the simulation of the electromagnetic circuits, actual fluid-dynamic forces acting on needle surfaces and discharge coefficients, evaluated by means 3D-CFD simulations. In order to assess new injection system dynamic response under multiple injection strategies reproducing actual engine operating conditions it is necessary to find to proper model settings. In this work the integration between the injector and the system model, which comprehends the pump, the pressure regulator, the rail and the connecting-pipes, will be presented. For reproducing the dynamic response of he whole system will be followed a step-by-step approach in order to prevent modelling inaccuracies. Firstly will be presented the linear analysis results performed in order to find injection system own natural frequencies. Secondly based on linear analysis results will be found proper injection system model settings for predicting dynamic response to external excitations, such as pump perturbations, pressure regulator dynamics and injection pulses. Thirdly experimental results in terms of instantaneous flow rate and integrated injected volume for different operating conditions will be presented in order to highlight the capability of the modelling methodology in addressing the new injection system design.

Paper 12: Design of an Experimental Arm Prosthesis: Engineering Aspects

1968 ◽  
Vol 183 (10) ◽  
pp. 68-73
Author(s):  
S. R. Montgomery
Keyword(s):  
Dynamic Response ◽  
Control Systems ◽  
Position Control ◽  
Velocity Control ◽  
Design Specification ◽  
Design And Construction

Externally powered arm prostheses have, to date, with few exceptions been made with simple velocity control of each movement. In order to make such devices controllable the dynamic response must be relatively poor. A prosthesis is being built experimentally for which the specification is based on the biological requirements discussed in McWilliam's paper (see Paper 13). The arms are pneumatically powered and provided with position-control systems. The paper describes the design and construction of such a pair of arms, including a discussion of the problems involved in meeting the design specification while making the device acceptable in terms of weight and appearance.

Forced Vibration of Surface Foundation on Viscoelastic Isotropic Multi-Layered Stratum

2016 ◽  
Vol 16 (09) ◽  
pp. 1550061 ◽  
Author(s):  
Lin Chen
Keyword(s):  
Dynamic Response ◽  
Forced Vibration ◽  
Numerical Approach ◽  
Contact Forces ◽  
Precise Integration ◽  
Irregular Shapes ◽  
Layered Stratum ◽  
Surface Foundation ◽  
Soil Foundation ◽  
Impedance Functions

A numerical approach is presented for analyzing the forced vibration of a rigid surface foundation. In the analysis, the foundation is discretized into a number of sub square-elements. The dynamic response within each sub-element is described by the Green’s function, which is obtained by the Fourier–Bessel transform and the precise integration method (PIM). Then, a system of linear algebraic equation in terms of the contact forces within each sub-element is derived, which leads to the desired dynamic impedance functions of the foundation. Numerical results are obtained for the foundation not only with a simple geometry, such as circular one, but also with irregular shapes. Comparisons between the results obtained by the proposed approach and the thin layered method are made, for which good agreement is achieved. Also, parametric studies are performed on the dynamic response of the foundation, considering the effects of the material damping, stratum depth, Poisson’s ratio and the contact condition of the soil–foundation interface. Several conclusions are drawn concerning the significance of each parameter. Further application of the method can be easily extended to the analysis of a foundation on a viscoelastic anisotropic multi-layered stratum because no further complexity is introduced except the constitutive matrix needs to be modified.

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