scholarly journals SLOW OSCILLATIONS IN DRIVES OF MACHINE ASSEMBLIES

2021 ◽  
pp. 106-110
Author(s):  
Nikolay P. Yaroshevich ◽  
Тetjana S. Yaroshevych ◽  
Оlexander V. Shovkomud
Keyword(s):  
Degrees Of Freedom ◽  
Rotation Frequency ◽  
Vibration Exciter ◽  
Load Torque ◽  
Vibration Machine ◽  
Slow Oscillations ◽  
Resonance Effects ◽  
Direct Separation ◽  
Motion Mode ◽  
Machine Assembly

Machine assembly with additional degrees of freedom is considered. The method of direct separation of motions was used for research. It was shown that the braking vibration moment occurring by the reason of resonance effects in the driven object can lead to excitation of rotor oscillations of the assembly with a occurrence of slow oscillations of the vibration exciter rotor is demonstrated. frequency lower than the rotation frequency. Slow rotor oscillations represent a transient process to the stationary motion mode, which is established when an additional load torque occurs. Moreover, the maximum oscillation amplitudes will be relatively large. By the example of a vibration machine with an inertial drive, the occurrence of slow oscillations of the vibration exciter rotor is demonstrated.

ROTATIONS AND VIBRATIONS OF FULLERENES IN THE MOLECULAR COMPLEX C20@C80

2021 ◽  
pp. 35-48
Author(s):  
M.A. Bubenchikov ◽  
◽  
A.M. Bubenchikov ◽  
D.V. Mamontov ◽  
◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Classical Mechanics ◽  
Rotation Frequency ◽  
Dynamic State ◽  
Large Molecules ◽  
Rotational Degrees Of Freedom ◽  
Rotational Motions ◽  
Centers Of Mass ◽  
The Moment

The aim of this work is to apply classical mechanics to a description of the dynamic state of C20@C80 diamond complex. Endohedral rotations of fullerenes are of great interest due to the ability of the materials created on the basis of onion complexes to accumulate energy at rotational degrees of freedom. For such systems, a concept of temperature is not specified. In this paper, a closed description of the rotation of large molecules arranged in diamond shells is obtained in the framework of the classical approach. This description is used for C20@C80 diamond complex. Two different problems of molecular dynamics, distinguished by a fixing method for an outer shell of the considered bimolecular complex, are solved. In all the cases, the fullerene rotation frequency is calculated. Since a class of possible motions for a single carbon body (molecule) consists of rotations and translational displacements, the paper presents the equations determining each of these groups of motions. Dynamic equations for rotational motions of molecules are obtained employing the moment of momentum theorem for relative motions of the system near the fullerenes’ centers of mass. These equations specify the operation of the complex as a molecular pendulum. The equations of motion of the fullerenes’ centers of mass determine vibrations in the system, i.e. the operation of the complex as a molecular oscillator.

Kinematics Analysis and Motion Control of a Mobile Robot Driven by Three Tracked Vehicles

2018 ◽  
Author(s):  
Xin-Jun Liu ◽  
Zhao Gong ◽  
Fugui Xie ◽  
Shuzhan Shentu
Keyword(s):  
Mobile Robot ◽  
Motion Planning ◽  
Degrees Of Freedom ◽  
Inverse Kinematic ◽  
Planning Method ◽  
Tracked Vehicles ◽  
Loop Control ◽  
Point Motion ◽  
Point To Point ◽  
Motion Mode

In this paper, a mobile robot named VicRoB with 6 degrees of freedom (DOFs) driven by three tracked vehicles is designed and analyzed. The robot employs a 3-PPSR parallel configuration. The scheme of the mechanism and the inverse kinematic solution are given. A path planning method of a single tracked vehicle and a coordinated motion planning of three tracked vehicles are proposed. The mechanical structure and the electrical architecture of VicRoB prototype are illustrated. VicRoB can achieve the point-to-point motion mode and the continuous motion mode with employing the motion planning method. The orientation precision of VicRoB is measured in a series of motion experiments, which verifies the feasibility of the motion planning method. This work provides a kinematic basis for the orientation closed loop control of VicRoB whether it works on flat or rough road.

An Overview on a Nonideal System With Three and a Half Degrees of Freedom

2005 ◽  
Author(s):  
Karen de Lolo Guilherme ◽  
Jose´ Manoel Balthazar ◽  
Paulo Roberto Gardel Kurka ◽  
Masayoshi Tsuchida
Keyword(s):  
Degrees Of Freedom ◽  
Averaging Method ◽  
Dynamical Behavior ◽  
Mathematical Formulation ◽  
Rotation Frequency ◽  
Steady State Solution ◽  
Dc Motor ◽  
Physical Parameters ◽  
Phase Coordinates ◽  
Limited Power

The present paper studies a system comprised of two blocks connected by springs and dampers, and a DC motor with limited power supply fixed on a block, characterizing a non-ideal problem. This DC motor exciting the system causes interactions between the motor and the structure supporting it. Because of that, the non-ideal mathematical formulation of the problem has one and a half extra degree of freedom than the ideal one. A suitable choice of physical parameters leads to internal resonance conditions, that is, its natural frequencies are multiple of each other, by a known integer quantity. The purpose here is to study the dynamic behavior of the system using an analytical method based on perturbation techniques. The literature shows that the averaging method is the more flexible method concerning non-ideal problems. Summarizing, an steady state solution in amplitude and phase coordinates was obtained with averaging method showing the dependence of the structure amplitudes with the rotation frequency of the motor. Moreover, this solution shows that on of the amplitude coordinates has influence in the determination of the stationary rotation frequency. The analytical solution obtained shows the presence of the rotation frequency in expressions representing the oscillations of the structure, and the presence of amplitude coordinates in expressions describing the dynamic motion of the DC motor. These characteristics show the influence not only of the motor on structure but also of the response of the structure on dynamical behavior of the motor.

scholarly journals Kolmogorov Unstable Stellar Oscillations

1983 ◽  
Vol 66 ◽  
pp. 297-321
Author(s):  
J. Perdang
Keyword(s):  
Numerical Analysis ◽  
Internal Resonance ◽  
Degrees Of Freedom ◽  
High Surface ◽  
Broad Band ◽  
Resonance Effects ◽  
Stellar Oscillations ◽  
Noise Type ◽  
Non Linear ◽  
Equipartition Of Energy

AbstractWe survey the mathematics of non-linear Hamiltonian oscillations with emphasis being laid on the more recently discovered Kolmogorov instability. In the context of radial adiabatic oscillations of stars this formalism predicts a Kolmogorov instability even at low oscillation energies, provided that sufficiently high linear asymptotic modes have been excited.Numerical analysis confirms the occurrence of this instability. It is found to show up already among the lowest order modes, although high surface amplitudes are then required (ǀδrǀ/R ~ 0.5 for an unstable fundamental mode – first harmonic coupling). On the basis of numerical evidence we conjecture that in the Kolmogorov unstable regime the enhanced coupling due to internal resonance effects leads to an equipartition of energy over all interacting degrees of freedom. We also indicate that the power spectrum of such oscillations is expected to display two components: A very broad band of overlapping pseudo-linear frequency peaks spread out over the asymptotic range, and a strictly non-linear 1/f-noise type component close to the frequency origin.It is finally argued that the Kolmogorov instability is likely to occur among non-linearly coupled non-radial stellar modes at a surface amplitude much lower than in the radial case. This lends support to the view that this instability might be operative among the solar oscillations.

Advance Control Experiment of Vibration Machine with High Vibration Intensity Based on SCM – Dynamics Characteristics and Advanced Control

2014 ◽  
Vol 912-914 ◽  
pp. 554-558
Author(s):  
Xiao Lan Yang ◽  
Ji Feng Liu ◽  
Meng Nan Si ◽  
Jia Wei Li ◽  
Biao Huang
Keyword(s):  
Frequency Conversion ◽  
Frequency Converter ◽  
Vibration Exciter ◽  
Vibration Machine ◽  
Vibration Intensity ◽  
Strongly Nonlinear ◽  
Advanced Control ◽  
Vibration Stress ◽  
Double Mass ◽  
Intensity Characteristic

The vibration-stress field could be formed by high vibration intensity in vibration machine to improve the ability of the collision, shock, shear and extrusion for the system, and it also can avoid plugging screen for vibration screening machine, which could make for solving some special requirements of the vibration machine. To research the vibration machines strongly nonlinear and high vibration intensity characteristic such as certain excitation and uncertain response, the vibration machine with its double-mass is built, and its vibration exciter uses two partial blocks as vibration motor. In addition, dynamic vibration differential equation is established. To achieve high vibration intensity results based on the vibration machines safe working, the advanced control based on the SCM and Intelligent frequency conversion is put forward, and the advanced control system with its host computer, frequency converter, SCM, charge-amplifier, sensor and the vibration machine is been established.

scholarly journals Dynamics of a rigid rotor in the elastic bearings

2004 ◽  
Vol 31 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Inga Arkhipova
Keyword(s):  
Linear System ◽  
Mechanical System ◽  
Degrees Of Freedom ◽  
Rotation Frequency ◽  
Rigid Rotor ◽  
Plane Parallel ◽  
Vertical Rotor ◽  
Parallel Motion ◽  
Non Linear ◽  
Unlimited Growth

As a rule in the studies of a rigid rotor in the elastic bearings the authors consider the linear system corresponding to the plane-parallel motion and the effect of self-centring under unlimited growth of the rotation frequency. In the present paper rotor is considered as a mechanical system with four degrees of freedom. Different motions of a statically and dynamically unbalanced vertical rotor supported in the non-linear bearings are studied.

scholarly journals PIPELINE ROBOTS WITH ELASTIC ELEMENTS

Transport ◽  
2002 ◽  
Vol 17 (5) ◽  
pp. 177-181 ◽  
Author(s):  
Arvydas Matuliauskas ◽  
Bronislovas Spruogis
Keyword(s):  
Mathematical Model ◽  
Mathematical Models ◽  
Degrees Of Freedom ◽  
Vibration Exciter ◽  
Motion Equations ◽  
Two Degrees Of Freedom ◽  
One Dimensional ◽  
The Mathematical Model ◽  
Original Construction ◽  
Elastic Elements

In the article constructions of the pipeline robots with elastic elements are reviewed and the scheme of new original construction is presented. The mathematical models of a robot with one-dimensional vibration exciter with two degrees of freedom were developed and the equations of movement were formed and written. The mathematical model of the pipeline robot with circular elements is formed and its motion equations are presented.

Measurement System for Multiple Degrees of Freedom Moving Robot

1993 ◽  
Vol 5 (5) ◽  
pp. 453-456
Author(s):  
Kiyoshi Takamasu ◽  
Keyword(s):  
Measurement System ◽  
Degrees Of Freedom ◽  
Laser Interferometer ◽  
Positioning System ◽  
Two Dimensional ◽  
Multiple Degrees Of Freedom ◽  
Absolute Motion ◽  
Measurement Mode ◽  
High Flexibility ◽  
Motion Mode

The multiple degrees of freedom (multi-DOF) moving robot and its measurement system have been developed realize a positioning system with high flexibility. The multi-DOF robot is driven by six piezo-electric devices; and it moves in two modes, an absolute motion mode and a relative motion mode. In the absolute motion mode, it walks on a surface plate by a two-dimensional inchworm method having 3-DOF, in X and Y directions and a rotation. After a frame body is fixed, a center table can be positioned on 6-DOF. For measuring its position, the novel position measurement system has been developed. It has two measurement modes; an absolute measurement mode and a relative measurement mode. In the absolute mode, the two-dimensional position of the robot can be calculated from the length of a laser interferometer and the angle of a tracking mirror. After the tracking mirror is fixed, the relative displacement of the center table is measured by the laser interferometer, and the position of a reflecting laser beam is measured on a Position Sensitive Detector (PSD). We conclude that the high flexibility positioning system can be realized using the multi-DOF robot and the measurement system.

Resonances of elastic rotor induced by roller bearing with consideration of cage vibration

2017 ◽  
Vol 232 (4) ◽  
pp. 446-456
Author(s):  
Dawei Huang ◽  
Yi Liu ◽  
Heng Liu ◽  
Jun Yi
Keyword(s):  
Degrees Of Freedom ◽  
Resonance Effect ◽  
Roller Bearing ◽  
Coupling Model ◽  
Flexible Rotor ◽  
Resonance Effects ◽  
Nonlinear Springs ◽  
Modal Synthesis ◽  
Coupling Dynamic ◽  
Variable Compliance

The rotor system supported by rolling bearings usually provides a resonance effect due to the nonlinearity of bearings. In this paper, the causes of these anomalous resonance effects are discussed by establishing coupling dynamic model of the flexible rotor-roller bearings system. The 4-degrees of freedom (DOF) Timoshenko finite element and the free interface modal synthesis technique are used to model the elastic rotor. Then, a piece-wise flexible rotor model coupling with a 5-DOF dynamic bearing model is obtained by fixing the inner race to rotor. And waterfall plots are mainly obtained using the method of adaptive Runge-Kutta. Comparisons are made between the simulated response of the rotor-simplified bearing and rotor-bearing coupling models. Firstly, the vibration of cage can cause supercritical anomaly vibration except for the subcritical vibration induced by the variable compliance vibration. Secondly, the vibration amplitude of the coupling model is lower than the rotor-nonlinear springs model.

Non-Linear Dynamics of a Simplified Model of an Overhung Rotor Subjected to Intermittent Annular Rubs

2014 ◽  
Author(s):  
Andrea Zilli ◽  
Robin J. Williams ◽  
David J. Ewins
Keyword(s):  
Degrees Of Freedom ◽  
Piecewise Linear ◽  
Stable Limit Cycle ◽  
Rotation Frequency ◽  
Forced Response ◽  
Stable Limit ◽  
Simple Relationship ◽  
Synchronous Motion ◽  
Numerical Bifurcation ◽  
The Time Domain

The dynamic forced response of a two-degrees-of-freedom model of an unbalanced overhung rotor with clearance and symmetric piecewise-linear stiffness is examined in the time domain. The stiffness nonlinearity is representative of the contact between the rotor and a concentric stator ring. This rubbing interaction comes as a result of the rotor transient motion initiated by the sudden application of a static unbalance, such as in a blade loss scenario. The focus of this study is on the range of rotor speeds above resonance, where the contact between rotor and stator is characterised by a “bouncing” or intermittent type of behaviour. Brute-force numerical bifurcation analysis on the long-term forced response revealed ranges of rotation frequency for which there is bi-stability between non-impacting synchronous equilibrium and impacting sub-synchronous motion. It is found that, for sufficiently high levels of transient energy in the rotor, there exists the possibility for the solution to jump into a stable limit cycle characterised by three non-harmonically related frequencies, namely the synchronous response frequency and the forward and backward whirl frequencies. A simple relationship defining the point of synchronisation between these three components is proposed as an explanation to the region of bi-stability detected. The stiffening effect induced by the contact non-linearity enables this synchronisation to be maintained over a range of forcing frequencies rather than just at the single condition determined from the nominal whirl mode frequencies.

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