On The Dynamics of Intermittent-Motion Mechanisms. Part 1: Dynamic Model and Response

1983 ◽  
Vol 105 (3) ◽  
pp. 534-540 ◽  
Author(s):  
Ting W. Lee ◽  
A. C. Wang
Keyword(s):  
Dynamic Models ◽  
Damping Ratio ◽  
Relative Displacement ◽  
Dynamical Response ◽  
Damping Force ◽  
Damping Material ◽  
Proposed Model ◽  
Maximum Relative Displacement ◽  
Motion Characteristics ◽  
Intermittent Motion

This paper deals with a basic problem regarding intermittent-motion mechanisms, namely, how to formulate a predicative model for the study of the dynamics of these mechanisms. A mathematical model is developed in this investigation. The model, which includes clearance, damping, material compliance, and mechanism elasticity, is basic to the determination of the dynamical response such as force amplification and motion characteristics of mechanisms with intermittent motion. A new approach in the modeling of system damping is presented. Instead of using damping ratio, which is difficult to estimate accurately, a new damping function is introduced, which characterizes the speed and load dependent nature of damping. Two types of damping functions are proposed and both of their corresponding damping forces satisfy the expected hysteresis boundary conditions, i.e., zero damping force at zero and maximum relative displacement of contact. A comparative study of the present model with conventional dynamic models is performed. It demonstrates the characteristics and the usefulness of the proposed model for the study of the dynamics of intermittent-motion mechanisms.

Shock isolation characteristics of a bistable vibration isolator with tunable magnetic controlled stiffness

2021 ◽  
pp. 1-28
Author(s):  
Bo Yan ◽  
Peng Ling ◽  
Yanlin Zhou ◽  
Chuan-yu Wu ◽  
Wen-Ming Zhang
Keyword(s):  
Damping Ratio ◽  
Excitation Amplitude ◽  
Relative Displacement ◽  
Vibration Isolator ◽  
Maximum Acceleration ◽  
Vibration Isolators ◽  
Displacement Ratio ◽  
Shock Isolation ◽  
Maximum Relative Displacement ◽  
Isolation Performance

Abstract This paper investigates the shock isolation characteristics of an electromagnetic bistable vibration isolator (BVI) with tunable magnetic controlled stiffness. The theoretical model of the BVI is established. The maximum acceleration ratio (MAR), maximum absolute displacement ratio (MADR) and maximum relative displacement ratio (MRDR) are introduced to evaluate the shock isolation performance of the BVI. The kinetic and potential energy are observed to further explore the performance of the BVI. The effects of the potential barrier, shape of potential well, damping ratio on the BVI are discussed compared to the linear vibration isolators (LVI). The results demonstrate that the intrawell oscillations and snap-through oscillations are determined by the excitation amplitude and duration time of main pulse. MADR and MRDR of the BVI are smaller than those of the LVI. The maximum acceleration peak amplitude of the BVI is far below that of the LVI, especially when the snap-through oscillation occurs. In brief, the proposed BVI has a better shock isolation performance than the LVI and has the potential to suppress the shock of space structures during the launch and on-orbit deploying process.

Investigation into Central-Difference and Newmark’s Beta Methods in Measuring Dynamic Responses

2013 ◽  
Vol 831 ◽  
pp. 95-99 ◽  
Author(s):  
Behzad Mohammadzadeh ◽  
Hyuk Chun Noh
Keyword(s):  
Damping Ratio ◽  
Relative Displacement ◽  
Dynamic Responses ◽  
Dynamic Loads ◽  
Ground Acceleration ◽  
Central Difference ◽  
Earthquake Force ◽  
Central Difference Method ◽  
Require Response ◽  
Maximum Relative Displacement

Studies in the structural systems include two main approaches, design and analysis, which require response evaluation of structures to the external loads including live and dead loads. Structures behave statically and dynamically for static and dynamic loads, respectively. One of the most important dynamic loads acting on a structure is earthquake force. In order to find responses of structures subjected to earthquake, several schemes of direct integration can be used. This study deals with two methods of calculating dynamic responses of a single-degree of freedom oscillator, i.e., central difference method (CDM) and Newmarks beta method (NBM), using recorded ground acceleration for 60seconds. The maximum relative acceleration is obtained to determine maximum relative displacement by which estimation of quality and quantity of failure occurred to a structure for a given earthquake is provided. Firstly both CDM and NBM are discussed. Second, for a specific damping ratio dynamic responses are evaluated for periods of range in between 0.1sec to 1.5sec to evaluate the effects of period on responses of system. Third, the effects of damping on dynamic responses of SDOF system are evaluated by considering different damping coefficients from ζ=0 to 0.5. The results are compared and discussed to investigate the range of periods and damping factors where methods can provide a better estimation of responses.

Longitudinal Flight Dynamics of Baseline-II BWB UAV

2012 ◽  
Vol 433-440 ◽  
pp. 6636-6640 ◽  
Author(s):  
Rizal E.M. Nasir ◽  
Wahyu Kuntjoro ◽  
Wisnoe Wirachman ◽  
Zurriati Ali
Keyword(s):  
Pitch Angle ◽  
Control Algorithm ◽  
Dynamic Models ◽  
Damping Ratio ◽  
Flight Dynamics ◽  
Proposed Model ◽  
Short Period ◽  
Level 3 ◽  
Level 1 ◽  
Mode Response

The objective of this paper is to investigate longitudinal flight dynamics of the said aircraft at loitering flight condition near sea level. Three mathematical dynamic models are used to compute transient response of Baseline-II E-2 BWB along with a proposed model known as Model-N. Model-N is derived to incorporate as many important derivatives, including gravitational and pitch angle factor, as possible. While all these four dynamic models are different in a sense where one model is more simple or complex than the others, the basic architecture of all these models are the same. This paper shows the short-period mode needs serious attention. A control algorithm is needed to overcome its handicap which is below Level 3 damping ratio according to MIL-F-8785C. Improvement to phugoid can be considered secondary, but one must ensure that bringing short period mode to Level 1 flying quality does not make phugiod mode response worse than it is now.

scholarly journals Predicting the Energy Consumption of a Robot in an Exploration Task Using Optimized Neural Networks

Electronics ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 920
Author(s):  
Liesle Caballero ◽  
Álvaro Perafan ◽  
Martha Rinaldy ◽  
Winston Percybrooks
Keyword(s):  
Neural Network ◽  
Energy Consumption ◽  
Mobile Robot ◽  
Energy Budget ◽  
Dynamic Models ◽  
Pearson Correlation ◽  
Experimental Conditions ◽  
Grid Map ◽  
Proposed Model ◽  
Exploration Task

This paper deals with the problem of determining a useful energy budget for a mobile robot in a given environment without having to carry out experimental measures for every possible exploration task. The proposed solution uses machine learning models trained on a subset of possible exploration tasks but able to make predictions on untested scenarios. Additionally, the proposed model does not use any kinematic or dynamic models of the robot, which are not always available. The method is based on a neural network with hyperparameter optimization to improve performance. Tabu List optimization strategy is used to determine the hyperparameter values (number of layers and number of neurons per layer) that minimize the percentage relative absolute error (%RAE) while maximize the Pearson correlation coefficient (R) between predicted data and actual data measured under a number of experimental conditions. Once the optimized artificial neural network is trained, it can be used to predict the performance of an exploration algorithm on arbitrary variations of a grid map scenario. Based on such prediction, it is possible to know the energy needed for the robot to complete the exploration task. A total of 128 tests were carried out using a robot executing two exploration algorithms in a grid map with the objective of locating a target whose location is not known a priori by the robot. The experimental energy consumption was measured and compared with the prediction of our model. A success rate of 96.093% was obtained, measured as the percentage of tests where the energy budget suggested by the model was enough to actually carry out the task when compared to the actual energy consumed in the test, suggesting that the proposed model could be useful for energy budgeting in actual mobile robot applications.

Optimal Design of Vibration Absorber Systems Supported by Elastic Base

1991 ◽  
Author(s):  
Hashem Ashrafiuon
Keyword(s):  
Dynamic Models ◽  
Damping Ratio ◽  
Equations Of Motion ◽  
Elastic Base ◽  
Design Parameters ◽  
Primary System ◽  
Vibration Absorbers ◽  
Equivalent Damping ◽  
System Equations ◽  
Different Levels

Abstract This paper presents the effect of foundation flexibility on the optimum design of vibration absorbers. Flexibility of the base is incorporated into the absorber system equations of motion through an equivalent damping ratio and stiffness value in the direction of motion at the connection point. The optimum values of the uncoupled natural frequency and damping ratio of the absorber are determined over a range of excitation frequencies and the primary system damping ratio. The design parameters are computed and compared for the rigid, static, and dynamic models of the base as well as different levels of base flexibility.

Equivalent circuit model of eddy current damping regarding frequency-dependence with test validation

2021 ◽  
pp. 136943322110509
Author(s):  
Zhiguo Shi ◽  
Cheng Ning Loong ◽  
Jiazeng Shan
Keyword(s):  
Equivalent Circuit ◽  
Eddy Current ◽  
Dynamic Testing ◽  
Equivalent Circuit Model ◽  
Time History ◽  
Circuit Model ◽  
Theoretical Expression ◽  
Fe Model ◽  
Damping Force ◽  
Proposed Model

This study proposes an equivalent circuit model to simulate the mechanical behavior and frequency-dependent characteristic of eddy current (EC) damping, with the validations from multi-physics finite element (FE) modeling and dynamic testing. The equivalent circuit model is first presented with a theoretical expression of the EC damping force. Then, the transient analysis with an ANSYS-based FE model of an EC damper is performed. The time-history forces from the FE model are compared with that from the proposed equivalent circuit model. The favorable agreement indicates that the proposed model can simulate the nonlinear behavior of EC damping under different excitation scenarios. A noncontact and friction-free planar EC damper is designed, and its dynamic behavior is measured by employing shake table testing. The experimental observations can be reproduced by the proposed equivalent circuit model with reasonable accuracy and reliability. The proposed equivalent circuit model is compared with the classical viscous model and the higher-order fractional model using a complex EC damper simulated in ANSYS to show the advantages of the proposed model regarding model simplicity and prediction accuracy. A single-degree-of-freedom (SDOF) structure with different EC damping models is further analyzed to illustrate the need for accurate EC damping modeling.

Dynamical Modeling of Gear Transmission Considering Gearbox Casing

2018 ◽  
Author(s):  
Yang Luo ◽  
Natalie Baddour ◽  
Ming Liang
Keyword(s):  
Dynamic Models ◽  
Signal Propagation ◽  
Gear Transmission ◽  
Gear System ◽  
Dynamical Model ◽  
Contact Friction ◽  
Dynamical Response ◽  
Dynamic Simulations ◽  
Friction Forces ◽  
Frequency Domains

Much research has been carried out to investigate the dynamical response of a gear system because of its importance on vibration feature analysis. It is well known that the gearbox casing is one of the most important components of the gear system and plays an important role in signal propagation. However, its effects have widely been neglected within the dynamic simulations and few dynamic models have considered the gearbox casing when modeling a gear transmission. This paper proposes a gear transmission dynamical model with the consideration of the effects of gearbox casing. The proposed dynamical model incorporates TVMS, a time-varying load sharing ratio, as well as dynamic tooth contact friction forces, friction moments and dynamic mesh damping coefficients. The proposed gear dynamical model is validated by comparison with responses obtained from experimental test rigs under different speed conditions. Comparisons indicate that the responses of the proposed dynamical model are consistent with experimental results, in both time and frequency domains under different rotation speeds.

Effects of Lumbar Spine Assemblies and Body-Borne Equipment Mass on Anthropomorphic Test Device Responses During Drop Tests

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Daniel Aggromito ◽  
Mark Jaffrey ◽  
Allen Chhor ◽  
Bernard Chen ◽  
Wenyi Yan
Keyword(s):  
Lumbar Spine ◽  
Federal Aviation Administration ◽  
Relative Displacement ◽  
Drop Tower ◽  
Test Device ◽  
Hybrid Iii ◽  
Drop Tests ◽  
Occupant Injury ◽  
Maximum Relative Displacement ◽  
The Impact

When simulating or conducting land mine blast tests on armored vehicles to assess potential occupant injury, the preference is to use the Hybrid III anthropomorphic test device (ATD). In land blast events, neither the effect of body-borne equipment (BBE) on the ATD response nor the dynamic response index (DRI) is well understood. An experimental study was carried out using a drop tower test rig, with a rigid seat mounted on a carriage table undergoing average accelerations of 161 g and 232 g over 3 ms. A key aspect of the work looked at the various lumbar spine assemblies available for a Hybrid III ATD. These can result in different load cell orientations for the ATD which in turn can affect the load measurement in the vertical and horizontal planes. Thirty-two tests were carried out using two BBE mass conditions and three variations of ATDs. The latter were the Hybrid III with the curved (conventional) spine, the Hybrid III with the pedestrian (straight) spine, and the Federal Aviation Administration (FAA) Hybrid III which also has a straight spine. The results showed that the straight lumbar spine assemblies produced similar ATD responses in drop tower tests using a rigid seat. In contrast, the curved lumbar spine assembly generated a lower pelvis acceleration and a higher lumbar load than the straight lumbar spine assemblies. The maximum relative displacement of the lumbar spine occurred after the peak loading event, suggesting that the DRI is not suitable for assessing injury when the impact duration is short and an ATD is seated on a rigid seat on a drop tower. The peak vertical lumbar loads did not change with increasing BBE mass because the equipment mass effects did not become a factor during the peak loading event.

scholarly journals Topology Optimization and Performance Calculation for Control Arms of a Suspension

2014 ◽  
Vol 6 ◽  
pp. 734568 ◽  
Author(s):  
Liang Tang ◽  
Jie Wu ◽  
Jinhao Liu ◽  
Cuicui Jiang ◽  
Wen-Bin Shangguan
Keyword(s):  
Topology Optimization ◽  
Ride Comfort ◽  
Constitutive Law ◽  
Fea Model ◽  
Proposed Model ◽  
Rubber Bushing ◽  
And Performance ◽  
Motion Characteristics ◽  
Ball Joints ◽  
Performance Calculation

Control Arm (CA) of a suspension plays an important role in the automotive ride comfort and handling stability. In this paper, the topology optimization model including ball joints and bushing for topology optimization of an aluminium CA is established, where a ball joint is simplified as rigid elements and the elastic properties of a rubber bushing are estimated using Mooney-Rivlin constitutive law. A method for treating with multiple loads in topology optimization of CA is presented. Inertia relief theory is employed in the FEA model of the CA in order to simulate the large displacement motion characteristics of the CA. A CA is designed based on the topology optimization results, and the strength, natural frequency, and rigidity of the optimized CA are calculated. The calculated results show that the performances of the optimized CA with the proposed model meet the predetermined requirements.

Study of Snubbing Mechanism Using Finite Element Method

2014 ◽  
Author(s):  
Jingming Chen ◽  
Paolo Pennacchi ◽  
Dongxiang Jiang ◽  
Steven Chatterton
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Forced Vibration ◽  
Excitation Frequency ◽  
Relative Displacement ◽  
Rotor Blades ◽  
Motion Pattern ◽  
Motion Characteristics ◽  
The Time Domain ◽  
Element Method

In the rotating machineries, large vibrations of a blade would result in fatigue crack, which is a great threaten to the safety. Therefore, it is of great importance to reduce the blade vibrations. Snubbing technique is a possible solution to this problem. A tiny gap is left between the shrouds of adjacent blades. While the forced vibration makes the relative displacement between two neighboring blades exceed the gap, the contact happens at the contact face of the shrouds, accompanied with friction and energy dissipation, which restricts the vibration. In this paper, a simplified model for a set of rotor blades is established, by using finite element method. The contact between the adjacent shrouds is considered. In this way, snubbing phenomenon can occur under forced vibration. Based on the model, modal analysis has been conducted. The 8x rev. frequency has been chosen as the excitation frequency. Under a certain amplitude of sine excitation, the circumferential vibration of the blades has been simulated. The vibration has been analyzed in the time domain. As expected, the blade motion is divided into four different states in one period. They are: non-contact, rebounding, sticky and escaping state. The four states had different mechanical and motion characteristics. The motion pattern for the set of blades has been also analyzed and the wave spreading along the bladerow has been described. Because of the snubbing mechanism, the waveform was distorted into serrated shape.

Sign in / Sign up

Export Citation Format

Share Document