Design and Analysis of Multilink Flexible Mechanisms With Multiple Clearance Connections

1977 ◽  
Vol 99 (1) ◽  
pp. 88-96 ◽  
Author(s):  
S. Dubowsky ◽  
T. N. Gardner
Keyword(s):  
Complex Systems ◽  
Dynamic Behavior ◽  
Dynamic Models ◽  
Design Guidelines ◽  
Planar Mechanisms ◽  
Elastic Links ◽  
High Speeds ◽  
Impact Forces ◽  
Flexible Mechanisms

The problem of predicting the dynamic behavior of general planar mechanisms with elastic links and multiple clearance connections is addressed using a perturbation coordinate approach. Particular emphasis is placed on studying the effects of system elasticity on the high internal impact forces generated by the presence of the clearances at high speeds. Two examples of complete systems are considered and their responses are compared to the behavior of relatively simple dynamic models: the object is the development of design guidelines. The results show that the simpler models yield useful insights into the behavior of the more complex systems.

On the Modeling of Flexible-Link Planar Mechanisms: Experimental Validation of an Accurate Dynamic Model

2004 ◽  
Vol 126 (2) ◽  
pp. 365-375 ◽  
Author(s):  
Alessandro Gasparetto
Keyword(s):  
Mathematical Model ◽  
Dynamic Model ◽  
Dynamic Behavior ◽  
Experimental Validation ◽  
Test Case ◽  
Planar Mechanisms ◽  
Flexible Links ◽  
Multi Body ◽  
The Mathematical Model ◽  
Flexible Mechanisms

The experimental validation of an accurate dynamic model of flexible multi-body planar mechanisms is presented in this paper. The proposed mathematical model, which is valid for whatever planar mechanism with any number of flexible links, accounts for the geometric and inertial nonlinearities of the mechanism, and considers coupling effects among rigid-body and elastic motion as well. In order to experimentally validate the dynamic model, a flexible five-bar planar linkage actuated by two electric motors is employed as a test case. The experimentally measured deformations and accelerations of the flexible links are compared with the numerical results obtained by simulating the system dynamic behavior through the mathematical model. It turns out that the experimental results are in good agreement with the numerical ones, thus proving that the dynamical model proposed is very effective in the difficult task of accurately representing the dynamic behavior of flexible mechanisms.

Simulation Model of the Dynamic Behavior of a Tire Running Over an Obstacle

1988 ◽  
Vol 16 (2) ◽  
pp. 62-77 ◽  
Author(s):  
P. Bandel ◽  
C. Monguzzi
Keyword(s):  
Simulation Model ◽  
Dynamic Behavior ◽  
Black Box ◽  
Box Model ◽  
Vehicle Suspension ◽  
Empirical Relationships ◽  
Static Tests ◽  
High Speeds ◽  
Dynamic Forces ◽  
Vehicle Suspension System

Abstract A “black box” model is described for simulating the dynamic forces transmitted to the vehicle hub by a tire running over an obstacle at high speeds. The tire is reduced to a damped one-degree-of-freedom oscillating system. The five parameters required can be obtained from a test at a given speed. The model input is composed of a series of empirical relationships between the obstacle dimensions and the displacement of the oscillating system. These relationships can be derived from a small number of static tests or by means of static models of the tire itself. The model can constitute the first part of a broader model for description of the tire and vehicle suspension system, as well as indicating the influence of tire parameters on dynamic behavior at low and medium frequencies (0–150 Hz).

Vibration Dissipation Characteristics of Symmetrical Piezoelectric Networks With Passive Branches

2012 ◽  
Author(s):  
Yu Fan ◽  
Lin Li
Keyword(s):  
Dynamic Models ◽  
Vibration Suppression ◽  
Vibration Reduction ◽  
Design Guidelines ◽  
Connection Form ◽  
Network Connection ◽  
Lumped Parameter ◽  
The Given ◽  
Parameter Approach ◽  
Better Than

In this paper, a new vibration reduction approach by means of symmetric piezoelectric network is proposed, combining energy harvesting and vibration reduction. The system could be constructed by several individual structures with identical mechanical parameters, such as blades of rotor machinery. Two basic forms of network-connection are studied, in which dissipation of both mechanical and electric field is considered. Dynamic models are established by the Lumped Parameter approach and Kirchhoff’s Circuit Theorem, and the normalizing process is used to make the models more general. Subsequently, the modal information and harmonic response of piezoelectric networks with an arbitrary number of components are obtained. Based on the dynamic characteristics of piezoelectric networks, the mechanism of vibration-suppression behavior of such systems is studied. Design guidelines of these vibration reduction systems are established via parameter studies. Eventually, the optimized parameters of each network-connection form are obtained analytically. It is shown that the symmetric piezoelectric network can suppress the response of the given frequency to zero, and also perform better than pure passive piezoelectric shunts in resonant frequency band.

Dynamic Behavior of Piezoelectric Recurve Actuation Architectures

2004 ◽  
Vol 126 (1) ◽  
pp. 37-46 ◽  
Author(s):  
James D. Ervin ◽  
Diann E. Brei
Keyword(s):  
Dynamic Behavior ◽  
Architectural Design ◽  
Dynamic Models ◽  
Dynamic Performance ◽  
Design Parameters ◽  
New Family ◽  
State Frequency ◽  
Actuation Scheme ◽  
The Impact ◽  
High Work

A new family of piezoelectric actuators, called Recurves, exhibits high work per volume and have the extra benefit of performance and packaging tailorability. The focus of this paper is the dynamic performance of this novel actuation scheme. Two dynamic models, a detailed transfer matrix model and a simpler rod approximation model, are presented to predict the steady state frequency response of a general Recurve actuator driving a mass and spring load. Results from a 23 design of experiments are given that validate these models and demonstrate the impact of the architectural design parameters on the dynamic behavior of a generic Recurve actuator.

Study on Application of Time Petri Net in Nursing Home Site Selection

2013 ◽  
Vol 357-360 ◽  
pp. 2775-2780
Author(s):  
Wen Zhou Yan ◽  
Ge Ye Ren
Keyword(s):  
Nursing Home ◽  
Dynamic Behavior ◽  
Empirical Analysis ◽  
Petri Net ◽  
Public Transport ◽  
Site Selection ◽  
Ant Colony Algorithm ◽  
Dynamic Models ◽  
Model Method ◽  
Time Petri Net

Time Petri net is a model method which describes the dynamic behavior of the system by the moving of token. This paper takes location of a nursing home in Xi’an as the research object. The best position is selected by building dynamic models with time Petri net, and solving the model with Ant Colony algorithm, based on considering some factors such as public transport, health and environment. Finally, the effectiveness of the method on the selecting of location is confirmed by empirical analysis.

scholarly journals Evolution, Complex Systems and the Dialectic

1999 ◽  
pp. 74-103 ◽  
Author(s):  
Peter Knapp
Keyword(s):  
Complex Systems ◽  
Systems Theory ◽  
Complex Adaptive Systems ◽  
Adaptive Systems ◽  
Large Scale ◽  
Dynamic Models ◽  
Dynamic Properties ◽  
World Systems ◽  
World Systems Theory ◽  
Systems Models

The status of large scale historical macro-theories is contested both in world-systems theory and in sociology as a whole. I distinguish three types of such dynamic models: evolutionary models, systems models and dialectical models. I define dialectical models as a family of complex systems models characterized by positive feedback (self-reinforcement or auto-catalysis). Such models lead to processes of accumulation and polarization, leading to system crisis. The games of Monopoly and Risk provide popular examples. This paper investigates the dynamic properties of three examples of such models: Myrdal's model of cumulative causation; Collins's models of Marxian transformations and geopolitics; and Chaso-Dunn and Hall's iterative model of world-systems transformations. A combination of evolutionary, complex systems and dialectical analyses has consideralble overlap with chaotic, far-from-equilibrium types of models and with analyses of complex adaptive systems. Such discontinuous, nonlinear dynamic models show great potential for solving problems of dynamic analysis both within world-systems theory and within sociology as a whole.

Investigation and Prediction of Wave Impact Loads on Ship Appendage Shapes

2007 ◽  
Author(s):  
Anne M. Fullerton ◽  
Thomas C. Fu ◽  
David E. Hess
Keyword(s):  
Wave Height ◽  
Impact Force ◽  
Design Guidelines ◽  
Impact Loads ◽  
Wave Steepness ◽  
Wave Impact ◽  
Ship Structures ◽  
Impact Forces ◽  
Hull Structure ◽  
Horizontal Wave

Navy fleet problems with damage to hatches and other appendages after operation in high sea states suggest that wave impact loads may be greater than the current design guidelines of 1000 pounds per square foot (48 kilopascal) (Ship Specification Section 100, General Requirements for Hull Structure and Guidance Manual for Temporary Alterations, NAVSEA S9070-AA-MME-010/SSN, SSBN). These large impact forces not only cause damage to ships and ship structures, they can also endanger the ship’s crew. To design robust marine structures, accurate estimates of all encountered loads are necessary, including the wave impact forces, which are complex and involve wave breaking, making them difficult to estimate numerically. An experiment to investigate wave impact loads was performed at the Naval Surface Warfare Center, Carderock Division in 2005. During this experiment, the horizontal and vertical loads of regular, non-breaking waves on a 12 inch (0.305 m) square plate and a 19.75 inch (0.5 m) diameter horizontal cylinder were measured while varying incident wave height, wavelength, wave steepness, plate angle and immersion level of the plate and cylinder. Wave heights of up to 1.5 feet (0.46 m) were tested, with wavelenghs of up to 30 feet (9.1 m). In all cases, the horizontal wave impact force increased with wave steepness. For some angles, the horizontal wave impact force increased with greater submergence. A feed-forward neural network (FFNN) developed by Applied Simulation Technologies was used to predict the horizontal forces measured during the experiment based on the values of wave height, wavelength, wave steepness, plate angle and immersion level of the plate and cyclinder. A FFNN is a computational method used to develop nonlinear equation systems that use input variables to predict output variables. Predictions of forces from the FFNN compare well with the experimental data, and may be useful in future design of ships and ship structures.

Theories of Complex Systems and Educational Change at Multiple Scales

2017 ◽  
Author(s):  
Wolff-Michael Roth
Keyword(s):  
Complex Systems ◽  
Student Development ◽  
Path Dependence ◽  
Dynamic Models ◽  
Multiple Scales ◽  
Natural Sciences ◽  
Teacher Talk ◽  
Educational Systems ◽  
Learning And Development ◽  
Qualitative Models

Theories of complex systems originated in the natural sciences, where it became necessary to move away from describing systems in simple cause–effect models to using descriptions that take into account nonlinearity, emergence, path dependence, the interrelation of continuous (quantitative) and discontinuous (qualitative) transitions, and the interrelation of phenomena at multiple scales. Although some educators have begun to explore the usefulness of complex systems theories for describing educational phenomena at the different levels of scale, the vast majority of educational research continues to be dominated by simple and simplistic (quantitative and qualitative) models. After definition and discussion of different conceptions of systems, this article presents constraint satisfaction networks, chaos theory, and catastrophe theory, as dynamic models for social processes in education. The different models are introduced with easily accessible phenomena from the natural sciences. The models not only are sources of analogies and metaphors for articulating a variety of phenomena in educational systems, including learning and development, conceptual change, decision making, categorization, and curriculum implication, but also can be used for studying real educational systems. Readers find how these models can be used to think about and predict the behavior of systems at scales as small as student–teacher talk to school systems as a whole. The concepts are used to show why educational systems tend to be stable even when policymakers intend change and why some classroom contexts do not provide the conditions for student development despite well-meaning efforts of dedicated teachers.

Rotordynamic Performance of Flexure Pivot Tilting Pad Gas Bearings With Vibration Damper

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Aaron Rimpel ◽  
Daejong Kim
Keyword(s):  
Gas Turbines ◽  
Dynamic Models ◽  
Natural Frequencies ◽  
Clean Energy ◽  
Design Guidelines ◽  
Vibration Damper ◽  
Shell Mass ◽  
Gas Bearings ◽  
Tilting Pad ◽  
Rotor Bearing

Recently, gas-lubricated bearings have drawn enormous attention for clean energy conversion/process systems such as fuel cells, micro-gas-turbines, gas compressors, etc. Among many different types of gas bearings, tilting pad gas bearings have many attractive features such as high rotor-bearing stability and less severe thermal issues (due to multipad configurations) than foil gas bearings. However, extension of the application of the tilting pad gas bearings to flexible rotors and harsh environments with external vibrations/impacts poses significant design challenges. The design problem addressed in this paper is the vibration damper to be integrated with the flexure pivot tilting pad gas bearing (FPTPGB) with and without pad radial compliance. Linear and nonlinear dynamic models of the FPTPGB with vibration damper were developed, and rotordynamic performance was evaluated to prescribe design guidelines for the selection of bearing shell mass and damper properties. Direct numerical integration (time-domain orbit simulations) and linear analyses were employed to predict rotordynamic responses and other interesting behaviors relevant of rotor-bearing systems with the vibration damper. Rotor-bearing systems showed better performance with larger damper stiffness for both with and without radial compliance. However, bearing shell mass showed different tendencies; lower bearing shell mass was shown to be ideal for bearings with radial compliance, while the opposite trend was observed for bearings without radial compliance. Although increasing the degrees of freedom of the system by allowing the bearing shell to move introduces additional natural frequencies, careful design considerations could allow the placement of the natural frequencies outside of the operating range.

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