An Analytical and Experimental Study of Automobile Dynamics With Random Roadway Inputs

1977 ◽  
Vol 99 (4) ◽  
pp. 284-292 ◽  
Author(s):  
A. J. Healey ◽  
E. Nathman ◽  
C. C. Smith
Keyword(s):  
Experimental Study ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Vertical Direction ◽  
Degree Of Freedom ◽  
Vehicle Body ◽  
Acceleration Response ◽  
Wide Range ◽  
Frequency Components ◽  
The Common

This paper presents the results of an analytical and experimental study of ride vibrations in an automobile over roads of various degrees of roughness. Roadway roughness inputs were measured. Three different linear mathematical models were employed to predict the acceleration response of the vehicle body. The models used included two, four, and seven degrees of freedom, primarily for vertical direction motion. The results show that the prime source of errors in predicting responses of this type lies in the common assumptions made for roadway roughness spectra. With adequate description of the roadway inputs, the results showed that the seven degree of freedom model accurately predicted the low frequency response (up to 10 Hz). Using the seven degree of freedom model, predicted accelerations compare well with measured data for a wide range of roadways in the low frequency range. Higher frequency components in the measured acceleration response are significant and are illustrated here.

scholarly journals Analisis Getaran Kendaraan Sistem Satu Roda dalam tinjauan Dua Derajat Kebebasan

2019 ◽  
Vol 2 (01) ◽  
pp. 31-36
Author(s):  
Pipit Wahyu Nugroho
Keyword(s):  
Experimental Study ◽  
Degrees Of Freedom ◽  
Vehicle Body ◽  
Acceleration Response ◽  
Vehicle Modeling ◽  
The Road ◽  
Wheeled Vehicle ◽  
Road Profile ◽  
Vibration Responses ◽  
Suspension Stiffness

The comfort of the vehicle passenger of the vehicle and its stability are the important variables that are always needed by everyone who uses transportation. In order to achieve this goal, the suspension of the vehicle will play an important role because its function is to isolate passengers from the effects of excitation from outside the vehicle and also to control the wheels attached to the road surface. Therefore in this study, the influence of various types of suspensions on vehicle vibrations is observed in terms of comfort and stability. The type of suspension in this study is related to the level of suspensión stiffness namely the spring and the damper. Vehicle modeling to be applied in a one-wheeled vehicle with two degrees of freedom. The experimental study is conducted by loading of vehicle body weight and passengers to three type of suspension, soft, medium and hard. Vibration responses to be analyzed on the vehicle equation using Matlab to obtain the acceleration response of the displacement and the defelction. This research obtains a vibration response graph for each type of suspension for  some kind of road profile.

scholarly journals A Two-Degree-of-Freedom Cantilever-Based Vibration Triboelectric Nanogenerator for Low-Frequency and Broadband Operation

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1526 ◽  
Author(s):  
Gang Tang ◽  
Fang Cheng ◽  
Xin Hu ◽  
Bo Huang ◽  
Bin Xu ◽  
...  
Keyword(s):  
Output Voltage ◽  
Low Frequency ◽  
Degree Of Freedom ◽  
Triboelectric Nanogenerator ◽  
Energy Harvesters ◽  
Harvesting Technique ◽  
Wide Range ◽  
Operating Bandwidth ◽  
Self Powered ◽  
Two Degree Of Freedom

With the continual increasing application requirements of broadband vibration energy harvesters (VEHs), many attempts have been made to broaden the bandwidth. As compared to adopted only a single approach, integration of multi-approaches can further widen the operating bandwidth. Here, a novel two-degree-of-freedom cantilever-based vibration triboelectric nanogenerator is proposed to obtain high operating bandwidth by integrating multimodal harvesting technique and inherent nonlinearity broadening behavior due to vibration contact between triboelectric surfaces. A wide operating bandwidth of 32.9 Hz is observed even at a low acceleration of 0.6 g. Meanwhile, the peak output voltage is 18.8 V at the primary resonant frequency of 23 Hz and 1 g, while the output voltage is 14.9 V at the secondary frequency of 75 Hz and 2.5 g. Under the frequencies of these two modes at 1 g, maximum peak power of 43.08 μW and 12.5 μW are achieved, respectively. Additionally, the fabricated device shows good stability, reaching and maintaining its voltage at 8 V when tested on a vacuum compression pump. The experimental results demonstrate the device has the ability to harvest energy from a wide range of low-frequency (<100 Hz) vibrations and has broad application prospects in self-powered electronic devices and systems.

On the Problem of Lexicographical Representation of Productive Phraseological Patterns (As Shown by Modern Greek Constructional Phrasemes)

2021 ◽  
Vol 20 (9) ◽  
pp. 34-43
Author(s):  
Elizaveta S. Onufrieva ◽  
Irina V. Tresorukova
Keyword(s):  
Low Frequency ◽  
Variable Component ◽  
Unified Approach ◽  
Common Pattern ◽  
New Approach ◽  
Modern Greek ◽  
Wide Range ◽  
Form Part ◽  
The Common ◽  
Linguistic Usage

This paper discusses the problems of lexicographical representation of Modern Greek constructional phrasemes – productive phraseological patterns with one or more variable components (slots). The analysis of Modern Greek general and phraseological dictionaries has shown that, in Modern Greek lexicography, there is no unified approach towards the description of this type of phraseologisms. One of the significant problems associated with lexicographical treatment of Modern Greek constructional phrasemes is that some of them are registered in dictionaries as fully fixed expressions with their slot(s) filled with a specific lexeme or a specific proposition, without any indication that these expressions possess a variable component. Such lexicographical representation of productive phraseological patterns does not reflect the real linguistic usage and does not allow the reader of the dictionary to understand that the expressions described in the dictionary as fully fixed show considerable variation and possess one or two slots that can be filled with a wide range of words or word combinations. The corpus analysis of the constructional phraseme Ούτε να Ρ (literally, ‘neither if’), which is registered in Modern Greek dictionaries in five different, all fully lexically specified forms, has shown that the specific realizations of this productive phraseological pattern included in the dictionaries either have relatively low frequency of occurrence in the corpus, or are not encountered in the corpus at all. Other realizations of this phraseological pattern account for over 92 % of all the cases of its use in the corpus, but the common pattern behind them can hardly be identified with the help of the existing lexicographical descriptions, as it is registered in the dictionaries under the lemmas of five different lexemes that do not form part of its fixed component. Based on the findings of this study, the paper raises the issue of developing a new approach towards the description of productive phraseological patterns that currently pose a significant challenge for adequate lexicographical representation.

On Instability Pockets and Influence of Damping in Parametrically Excited Systems

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Ashu Sharma ◽  
S. C. Sinha
Keyword(s):  
Degrees Of Freedom ◽  
State Transition ◽  
Degree Of Freedom ◽  
Transition Matrices ◽  
Stability Boundaries ◽  
Parametrically Excited ◽  
Parametric Space ◽  
Stability Diagrams ◽  
Wide Range ◽  
The Stability

In most parametrically excited systems, stability boundaries cross each other at several points to form closed unstable subregions commonly known as “instability pockets.” The first aspect of this study explores some general characteristics of these instability pockets and their structural modifications in the parametric space as damping is induced in the system. Second, the possible destabilization of undamped systems due to addition of damping in parametrically excited systems has been investigated. The study is restricted to single degree-of-freedom systems that can be modeled by Hill and quasi-periodic (QP) Hill equations. Three typical cases of Hill equation, e.g., Mathieu, Meissner, and three-frequency Hill equations, are analyzed. State transition matrices of these equations are computed symbolically/analytically over a wide range of system parameters and instability pockets are observed in the stability diagrams of Meissner, three-frequency Hill, and QP Hill equations. Locations of the intersections of stability boundaries (commonly known as coexistence points) are determined using the property that two linearly independent solutions coexist at these intersections. For Meissner equation, with a square wave coefficient, analytical expressions are constructed to compute the number and locations of the instability pockets. In the second part of the study, the symbolic/analytic forms of state transition matrices are used to compute the minimum values of damping coefficients required for instability pockets to vanish from the parametric space. The phenomenon of destabilization due to damping, previously observed in systems with two degrees-of-freedom or higher, is also demonstrated in systems with one degree-of-freedom.

scholarly journals Association of autonomic dysfunction and clozapine

2001 ◽  
Vol 179 (2) ◽  
pp. 167-171 ◽  
Author(s):  
Hagit Cohen ◽  
Uri Loewenthal ◽  
Michael Matar ◽  
Moshe Kotler
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Psychiatric Patients ◽  
Low Frequency ◽  
Power Spectral Analysis ◽  
Rate Analysis ◽  
Power Spectral ◽  
Wide Range ◽  
Frequency Components ◽  
Heart Rate Analysis

BackgroundAntipsychotic medications cause a wide range of adverse effects and have been associated with sudden death in psychiatric patients.AimsTo supply power spectral analysis of heart rate variability as a tool to examine the arrythmogenic effects of neuroleptics.MethodHeart rate analysis was carried out in patients with schizophrenia on standard doses of neuroleptic monotherapy − 21 were on clozapine, 18 on haloperidol and 17 on olanzapine – and in 53 healthy subjects.ResultsPatients with schizophrenia on clozapine had significantly higher heart rate, lower heart rate variability and lower high-frequency and higher low-frequency components compared with patients on haloperidol or olanzapine and matched control subjects. Prolonged QTc intervals were more common in patients than controls.ConclusionsPatients treated with neuroleptic medications, especially clozapine, showed autonomic dysregulation and cardiac repolarisation changes. Physicians should be aware of this adverse reaction.

scholarly journals Noise rich in low frequency components, a new comorbidity for periodontal disease? An experimental study

2014 ◽  
Vol 18 (4) ◽  
pp. 503
Author(s):  
Pedro MiguelAntunes Oliveira ◽  
Jose Brito ◽  
Artur ManuelPerez Neves Aguas ◽  
Jose AntonioMesquita Martins dosS antos ◽  
JoseJoao Baltazar Mendes
Keyword(s):  
Experimental Study ◽  
Periodontal Disease ◽  
Low Frequency ◽  
Frequency Components

IMPROVED MULTIPLE ATTENUATION IN COMMON DEPTH POINT STACKING

1974 ◽  
Vol 14 (1) ◽  
pp. 107
Author(s):  
John Wardell
Keyword(s):  
Random Noise ◽  
Low Frequency ◽  
Detailed Knowledge ◽  
Multiple Reflections ◽  
Response Curves ◽  
Seismic Section ◽  
Multiple Attenuation ◽  
Common Depth Point ◽  
Wide Range ◽  
The Common

Since the introduction of the common depth point method of seismic reflection shooting, we have seen a continued increase in the multiplicity of subsurface coverage, to the point where nowadays a large proportion of offshore shooting uses a 48 fold 48 trace configuration. Of the many benefits obtained from this multiplicity of coverage, the attenuation of multiple reflections during the common depth point stacking process is one of the most important.Examinations of theoretical response curves for multiple attenuation in common depth point stacking shows that although increased multiplicity does give improved multiple attenuation, this improvement occurs at higher and higher frequencies and residual moveouts (of the multiples) as the multiplicity continues to increase. For multiplicities greater than 12, the improvement is at relatively high frequencies and residual moveouts, while there is no significant improvement for the lower frequencies of multiples with smaller residual moveouts, which unfortunately are those most likely to remain visible after the stacking process.The simple process of zeroing, or muting, certain selected traces (mostly the shorter offset traces) before stacking can give an average 6 to 9 decibels improvement over a wide range of the low frequency and residual moveout part of the stack response, with 9-15 decibels improvement over parts of this range. The cost of this improvement is an increase in random noise level of 1-2 decibels. With digital processing methods, it is easy to zero the necessary traces over selected portions of the seismic section if so desired.The process does not require a detailed knowledge of the multiple residual moveouts, but can be used on a routine basis in areas where strong multiples are a problem, and a high stacking multiplicity is being used.

scholarly journals Auxetic vibration behaviours of periodic tetrahedral units with a shared edge

2021 ◽  
Vol 8 (10) ◽  
Author(s):  
H. Tanaka ◽  
S. Asao ◽  
Y. Shibutani
Keyword(s):  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Low Frequency ◽  
Slow Motion ◽  
Frequency Mode ◽  
Linear Elastic ◽  
Wide Range ◽  
Strain Relationship ◽  
Relationship Of ◽  
Low Frequency Mode

A very low-frequency mode supported within an auxetic structure is presented. We propose a constrained periodic framework with corner-to-corner and edge-to-edge sharing of tetrahedra and develop a kinematic model incorporating two types of linear springs to calculate the momentum term under infinitesimal transformations. The modal analysis shows that the microstructure with its two degrees of freedom has both low- and high-frequency modes under auxetic transformations. The low-frequency mode approaches zero frequency when the corresponding spring constant tends to zero. With regard to coupled eigenmodes, the stress–strain relationship of the uniaxial forced vibration covers a wide range. When excited, a very slow motion is clearly observed along with a structural expansion for almost zero values of the linear elastic modulus.

A fast technique using output only to localize and quantify multiple damages for multi-degree-of-freedom systems

2020 ◽  
pp. 147592172093281
Author(s):  
Liangliang Cheng ◽  
Wenshan Fang ◽  
Yunpeng Zhu
Keyword(s):  
Experimental Studies ◽  
Low Frequency ◽  
Degree Of Freedom ◽  
Theoretical Derivation ◽  
Structural Dynamic ◽  
Damage Indicators ◽  
Frequency Components ◽  
Output Only ◽  
Mass Spring ◽  
Local Stiffness

Vibration-based methods for identifying and evaluating structural damages have been widely studied in the last decades. However, in the state-of-art methods, there are some practical limitations owing to the complicated calculation process and low damage sensitivities. A new method for localizing and quantifying the damages of a beam-like structure based on low-frequency components, including direct current component, of the output signal subject to an arbitrary input excitation, is proposed in this article. The relationship between the low-frequency components of any two adjacent measurement points is investigated, in order to help to understand the link between damages and low-frequency components of outputs. The theoretical derivation of this method begins with a multi-degree-of-freedom structure of the mass–spring–damper chain, and the damage is considered to be a linear combination of local stiffness losses, resulting in changes in structural dynamic behaviors. The validity and feasibility of the proposed damage indicators are proved by numerical and experimental studies. It is further shown that the severity of the damage can be properly identified using the proposed damage indicator. Moreover, a discussion concerning potential detection on multiple nonlinear damages is presented at the end of this article.

Research on Pedestal Looseness Faults of Rotating System Based on Wavelet Analysis

2007 ◽  
Author(s):  
Zhaohui Ren ◽  
Hui Ma ◽  
Naihui Song ◽  
Feng Wen ◽  
Bang Chun Wen
Keyword(s):  
Critical Speed ◽  
Low Frequency ◽  
Vertical Direction ◽  
Elastic Stiffness ◽  
Nonlinear Phenomena ◽  
Test Rig ◽  
Rotating System ◽  
Vibration Signals ◽  
Frequency Components ◽  
Set Up

A model test rig of single-span rotor system is set up. By loosing tap bolts at one side of bearing housing to weaken elastic stiffness of supporting structure, the pedestal looseness faults existing in rotating machinery are simulated. The collected vibration signals with looseness faults at vertical direction are analyzed by the 3D waterfall spectra, wavelet scalogram and trajectory. The analytical results show that the chaotic low frequency components occur near the first critical speed and the complicated nonlinear phenomena appear, such as quasiperiodic motions and bifurcations etc. When the rotational speed exceeds double critical speed, the low frequency components tend towards stability.

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