scholarly journals Response of a Two-Degree-of-Freedom Vibration System with Rough Contact Interfaces

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Zhiqiang Huang ◽  
Xun Peng ◽  
Gang Li ◽  
Lei Hao
Keyword(s):  
Natural Frequency ◽  
Degree Of Freedom ◽  
Element Analysis ◽  
Chaotic Motions ◽  
First Order ◽  
Vibration Properties ◽  
Ground System ◽  
Jump Frequencies ◽  
Two Degree Of Freedom ◽  
Seismic Vibrator

This paper is focused on the influence of the rough contact interfaces on the dynamics of a coupled mechanical system. For this purpose, a two-degree-of-freedom model of a coupled seismic-vibrator-rough-ground system is proposed with which the nonlinear vibration properties are analyzed. In this model, the force-deflection characteristic of the contact interfaces is determined by finite element analysis. By analyzing the undamped free vibration, it was found that the variation of the second-order natural frequency with amplitude increases with rougher contact interfaces; however, the amplitude has little influence on the first-order natural frequency of the system. For the harmonic excited analysis, the jump frequencies and hysteretic region both decrease with rougher contact interfaces. Moreover, it is inferred from the bifurcation diagrams that, increasing the excitation force, the system can bring about chaotic motions on rough contact interfaces.

A Two Degree of Freedom Nanopositioner With Electrothermal Actuator for Decoupled Motion

2011 ◽  
Author(s):  
Yong-Sik Kim ◽  
Nicholas G. Dagalakis ◽  
Satyandra K. Gupta
Keyword(s):  
Design Concept ◽  
Degree Of Freedom ◽  
Motion Platform ◽  
Element Analysis ◽  
Electrothermal Actuators ◽  
Electrothermal Actuator ◽  
Decoupled Motion ◽  
Moving Platform ◽  
Two Degree Of Freedom ◽  
Novel Design

Building a two degree-of-freedom (2 DOF) MEMS nanopositioner with decoupled X-Y motion has been a challenge in nanopositioner design. In this paper a novel design concept on making the decoupled motion of the MEMS nanopositioner is suggested. The suggested nanopositioner has two electrothermal actuators and employs a fully nested motion platform with suspended anchors. The suggested MEMS nanopositioner is capable of delivering displacement from the electrothermal actuator to the motion platform without coupled motion between the two X-Y axes. The design concept, finite element analysis (FEA) results, fabrication procedures and the performance of the 2 DOF nanopositioner is presented. In order to test the nanopositioner moving platform decoupled motion, one actuator moves the platform by 60 μm, while the other actuator is kept at the same position. The platform position cross talk error was measured to be less than 1 μm standard deviation.

Application on Two Degree of Freedom Model Driven PID in Liner First-Order Inverted Pendulum

2013 ◽  
Vol 433-435 ◽  
pp. 1000-1004
Author(s):  
Jing Jing Shi ◽  
Li Xiang Zhang ◽  
Ai Qin Jiang
Keyword(s):  
Control System ◽  
Pid Control ◽  
Inverted Pendulum ◽  
Degree Of Freedom ◽  
Control Technology ◽  
Pendulum System ◽  
First Order ◽  
Model Driven ◽  
Inverted Pendulum System ◽  
Two Degree Of Freedom

The inverted pendulum system is a high order, strong coupling, multi-variable and absolutely unstable nonlinear system. Its optimal control has been the hotspot in the field of study. A new two degree of freedom model driven PID control system is introduced in this paper.It will state the structure of the control technology and design steps.The control technology is applied to control linear inverted pendulum in this paper. The simulation results prove that two degree of freedom model driven PID control system has the feasibility and superiority.

The Onset of Chaos in a Two-Degree-of-Freedom Impacting System

1989 ◽  
Vol 56 (1) ◽  
pp. 168-174 ◽  
Author(s):  
Jinsiang Shaw ◽  
Steven W. Shaw
Keyword(s):  
Piecewise Linear ◽  
Global Bifurcation ◽  
Degree Of Freedom ◽  
Chaotic Motions ◽  
Impact Damper ◽  
Onset Of Chaos ◽  
Spring System ◽  
Stability And Bifurcations ◽  
Mass Spring ◽  
Two Degree Of Freedom

The dynamic response of a two-degree-of-freedom impacting system is considered. The system consists of an inverted pendulum with motion limiting stops attached to a sinusoidally excited mass-spring system. Two types of periodic response for this system are analyzed in detail; existence, stability, and bifurcations of these motions can be explicitly computed using a piecewise linear model. The appearance and loss of stability of very long period subharmonics is shown to coincide with a global bifurcation in which chaotic motions, in the form of Smale horseshoes, arise. Application of this device as an impact damper is also briefly discussed.

Vibration Control of Two-Degree-of-Freedom Structures Utilizing Sloshing in Nearly Square Tanks

2017 ◽  
Vol 12 (5) ◽  
Author(s):  
Takashi Ikeda ◽  
Yuji Harata ◽  
Shota Ninomiya
Keyword(s):  
Vibration Control ◽  
Equations Of Motion ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Degree Of Freedom ◽  
Response Curves ◽  
Chaotic Motions ◽  
Installation Angle ◽  
Two Degree Of Freedom ◽  
Theoretical Results

This paper investigates the vibration control of a towerlike structure with degrees of freedom utilizing a square or nearly square tuned liquid damper (TLD) when the structure is subjected to horizontal, harmonic excitation. In the theoretical analysis, when the two natural frequencies of the two-degree-of-freedom (2DOF) structure nearly equal those of the two predominant sloshing modes, the tuning condition, 1:1:1:1, is nearly satisfied. Galerkin's method is used to derive the modal equations of motion for sloshing. The nonlinearity of the hydrodynamic force due to sloshing is considered in the equations of motion for the 2DOF structure. Linear viscous damping terms are incorporated into the modal equations to consider the damping effect of sloshing. Van der Pol's method is employed to determine the expressions for the frequency response curves. The influences of the excitation frequency, the tank installation angle, and the aspect ratio of the tank cross section on the response curves are examined. The theoretical results show that whirling motions and amplitude-modulated motions (AMMs), including chaotic motions, may occur in the structure because swirl motions and Hopf bifurcations, followed by AMMs, appear in the tank. It is also found that a square TLD works more effectively than a conventional rectangular TLD, and its performance is further improved when the tank width is slightly increased and the installation angle is equal to zero. Experiments were conducted in order to confirm the validity of the theoretical results.

Tuned mass damper and high static low dynamic stiffness isolator for vibration reduction of beam structure

2019 ◽  
Vol 234 (1) ◽  
pp. 95-115 ◽  
Author(s):  
Meysam Raei ◽  
Morteza Dardel
Keyword(s):  
Natural Frequency ◽  
Dynamic Stiffness ◽  
Excitation Amplitude ◽  
Tuned Mass Damper ◽  
Degree Of Freedom ◽  
Negative Stiffness ◽  
Low Frequencies ◽  
First Case ◽  
Mass Damper ◽  
Two Degree Of Freedom

In this work, the combination effect of tuned mass damper and high static low dynamic stiffness (HSLDS) isolator is investigated in reducing the vibration amplitude of Euler–Bernoulli beam with a nonlinear attachment. The performance of the absorber is studied in two cases; the first case, HSLDS isolator is one degree of freedom and the second case, two degree of freedom isolator is combined of HSLDS isolator and tuned mass damper absorber. By comparing the performance of these two isolators, it is revealed the two degree of freedom isolator has much better performance in direct force excitation and also improves the system performance in the base excitation. This isolator reduces the system amplitude at all frequencies, especially ultra-low frequencies, which is the main advantage to this isolator with respect to other isolators and reduces the natural frequency until the phenomenon of resonance occurs at a lower frequency. Moreover, decreasing the natural frequency increases the damping and in quasi zero stiffness and negative stiffness structure, the system has supercritical damping. This isolator is studied for positive, quasi zero and negative stiffness. The results show that the system with quasi zero stiffness has the best performances. Also, by increasing the excitation amplitude, the isolator loses its effectiveness.

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