scholarly journals Bifurcation of the roots of the characteristic polynomial and the destabilization paradox in friction induced oscillations

2007 ◽  
Vol 34 (2) ◽  
pp. 87-109 ◽  
Author(s):  
O.N. Kirillov
Keyword(s):  
Characteristic Polynomial ◽  
Analytical Description ◽  
Conservative System ◽  
Conveyor Belt ◽  
Disc Brake ◽  
Multiple Roots ◽  
Paradoxical Effect ◽  
Gyroscopic Forces ◽  
The Stability ◽  
Destabilization Paradox

Paradoxical effect of small dissipative and gyroscopic forces on the stability of a linear non-conservative system, which manifests itself through the unpredictable at first sight behavior of the critical non-conservative load, is studied. By means of the analysis of bifurcation of multiple roots of the characteristic polynomial of the non-conservative system, the analytical description of this phenomenon is obtained. As mechanical examples two systems possessing friction induced oscillations are considered: a mass sliding over a conveyor belt and a model of a disc brake describing the onset of squeal during the braking of a vehicle.

Attitude reconstruction from strap-down rate gyros using power series

2021 ◽  
pp. 1-19
Author(s):  
Habib Ghanbarpourasl
Keyword(s):  
Power Series ◽  
Taylor Series ◽  
Direction Cosine ◽  
Analytical Description ◽  
Double Precision ◽  
Angular Velocity Vector ◽  
Higher Order Terms ◽  
Direction Cosine Matrix ◽  
The Stability ◽  
Better Than

Abstract This paper introduces a power series based method for attitude reconstruction from triad orthogonal strap-down gyros. The method is implemented and validated using quaternions and direction cosine matrix in single and double precision implementation forms. It is supposed that data from gyros are sampled with high frequency and a fitted polynomial is used for an analytical description of the angular velocity vector. The method is compared with the well-known Taylor series approach, and the stability of the coefficients’ norm in higher-order terms for both methods is analysed. It is shown that the norm of quaternions’ derivatives in the Taylor series is bigger than the equivalent terms coefficients in the power series. In the proposed method, more terms can be used in the power series before the saturation of the coefficients and the error of the proposed method is less than that for other methods. The numerical results show that the application of the proposed method with quaternions performs better than other methods. The method is robust with respect to the noise of the sensors and has a low computational load compared with other methods.

Vibration and Stability Control of Spinning Flexible Shaft via Integration of Smart Materials Technology

2000 ◽  
Author(s):  
Ohseop Song ◽  
Liviu Librescu ◽  
Nam-Heui Jeong
Keyword(s):  
Smart Materials ◽  
Stability Control ◽  
Rotational Axis ◽  
Rotating Shaft ◽  
Nonconservative System ◽  
Gyroscopic Forces ◽  
Points Of View ◽  
The Stability ◽  
Spinning Speed ◽  
Static Character

Abstract Within this paper problems related with the vibration and stability control of circular flexible shafts spinning about their rotational axis are addressed. Due to the occurrence, as a result of the spinning speed, of gyroscopic forces in the system, the rotating shaft can experience, in some conditions, instabilities of the same nature as any nonconservative system, namely divergence and flutter instabilities. Whereas the former instability is of a static character, the latter one is of dynamic character and the results of its occurrence are catastrophic. By including collocated sending and actuating capabilities via integration in the system of piezoelectric devices and of a feedback control law, it is shown that a dramatic enhancement of both the free dynamic response and of the stability behavior from both the divergence and flutter points of view can be achieved. This implies that via the implementation of this technology an increase of the spinning speed can be achieved without the occurrence of these instabilities. Numerical simulations documenting these findings are provided and pertinent conclusions are outlined. It is also worthy to mention that the shaft is modeled as a thin-walled cylinder made of an anisotropic material and incorporating a number of non-classical features.

Esse? Percipi? Referentiality and Subjectivity in Footfalls

2018 ◽  
Vol 27 (1) ◽  
pp. 40-53
Author(s):  
Julie Gaillard
Keyword(s):  
Proper Names ◽  
The Body ◽  
Paradoxical Effect ◽  
Personal Pronouns ◽  
The Stability

This article analyzes how, in Footfalls, Beckett erodes subjective certainty as well as bodily evidence by calling into question the stability of referential mechanisms. Focusing on proper names and analyzing closely how they articulate (or rather disarticulate) personal pronouns and bodily referents, it shows how their unhinging produces a de-stabilization of reality, which has the paradoxical effect of calling into question the subjective unity and permanence of the body present on stage. This article follows the various movements of this short play to trace series of shifts and glitches in the pragmatics of enunciation, and shows how these glitches call into question the identity of the enunciating ‘I’ as well as the reality of its links to the body that it refers to.

scholarly journals Multi Body Dynamic Equations of Belt Conveyor and the Reasonable Starting Mode

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1489
Author(s):  
Yongbo Guo ◽  
Fansheng Wang
Keyword(s):  
Finite Element ◽  
Recursive Formula ◽  
Conservative System ◽  
Conveyor Belt ◽  
Dynamic Equations ◽  
Lagrange’S Equation ◽  
Rigid Finite Element Method ◽  
Potential Capacity ◽  
Multi Body ◽  
Body Dynamic

Based on the rigid finite element method and multibody dynamics, a discrete model of a flexible conveyor belt considering the material viscoelasticity is established. RFE (rigid finite element) and SDE (spring damping element) are used to describe the rigidity and flexibility of a conveyor belt. The dynamic differential equations of the RFE are derived by using Lagrange’s equation of the second kind of the non-conservative system. The generalized elastic potential capacity and generalized dissipation force of the SDE are considered. The forward recursive formula is used to construct the conveyor belt model. The validity of dynamic equations of conveyor belt is verified by field test. The starting mode of the conveyor is simulated by the model.

Control synthesis by full state vector in systems with fractional-order derivatives using Caputo-Fabrizio operator

2020 ◽  
Vol 8 (1) ◽  
pp. 106-115
Author(s):  
A. O. Lozynskyy ◽  
◽  
O. Yu. Lozynskyy ◽  
L. V. Kasha ◽  
◽  
...  
Keyword(s):  
Characteristic Polynomial ◽  
Fundamental Matrix ◽  
State Vector ◽  
Fractional Derivatives ◽  
Initial Conditions ◽  
Control Synthesis ◽  
Multiple Roots ◽  
System Operation ◽  
Full State ◽  
Control System Synthesis

In the paper, the control system synthesis by means of the full state vector is considered when using fractional derivatives in the description of this system. To conduct research in the synthesized system with fractional derivatives in the Caputo--Fabrizio representation, a fundamental matrix of the system is formed, which also allows us to analyze the influence of initial conditions on the processes within the system. In particular, the finding of the fundamental matrix of the system in the case of multiple roots of a characteristic polynomial, which are obtained by transforming the synthesized system to the binomial form, is demonstrated. The influence of the fractional derivative index and the location of the roots of the characteristic polynomial transformed to the binomial form on the system operation is analyzed.

Domains and Types of Aeroelastic Instability of Slender Beam

2007 ◽  
Author(s):  
Jirˇi´ Na´prstek
Keyword(s):  
Stability Boundary ◽  
Stability Loss ◽  
Stability Domain ◽  
Theoretical Explanation ◽  
Point Of View ◽  
System Response ◽  
Physical Point ◽  
Model Response ◽  
Gyroscopic Forces ◽  
The Stability

Slender structures exposed to a cross air flow are prone to vibrations of several types resulting from aeroelastic interaction of a flowing medium and a moving structure. Aeroelastic forces are the origin of nonconservative and gyroscopic forces influencing the stability of a system response. Conditions of a dynamic stability loss and a detailed analysis of a stability domain has been done using a linear mathematical model. Response properties of a system located on a stability boundary together with tendencies in its neighborhood are presented and interpreted from physical point of view. Results can be used for an explanation of several effects observed experimentally but remaining without theoretical explanation until now.

scholarly journals Squeal Frequency of a Railway Disc Brake Evaluation by FE Analyses

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
F. Cascetta ◽  
F. Caputo ◽  
A. De Luca
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Experimental Tests ◽  
Numerical Approach ◽  
System Stability ◽  
Brake System ◽  
Physical Parameters ◽  
Disc Brake ◽  
Complex Eigenvalues ◽  
The Stability

This paper deals with the development of a numerical model, based on the Finite Element (FE) theory for the prediction of the squeal frequency of a railway disc brake. The analytical background has been discussed and presented, as well as the most efficient methods for evaluating the system stability; the attention has been paid particularly to the complex eigenvalues method, which has been adopted within this paper to investigate the railway disc brake system. Numerical results have been compared with measurements from experimental tests in order to validate the proposed numerical approach. At the end of this work, a sensitivity analysis, aimed at understanding the effects of some physical parameters influencing the stability of the brake system and the squeal propensity, has been carried out.

The Loading-Frequency Relationship in Multiple Eigenvalue Problems

1971 ◽  
Vol 38 (4) ◽  
pp. 1007-1011 ◽  
Author(s):  
K. Huseyin ◽  
J. Roorda
Keyword(s):  
Eigenvalue Problems ◽  
Stability Boundary ◽  
Conservative System ◽  
Free Vibrations ◽  
Degree Of Freedom ◽  
External Loading ◽  
Loading Frequency ◽  
Multiple Loading ◽  
The Stability ◽  
Frequency Relationship

The free vibrations of a linear conservative system with multiple loading parameters are studied, attention being restricted to pure eigenvalue problems. It is shown that the smallest frequency and external loading parameters of such a system constitute a strictly convex (synclastic) surface which cannot have convexity toward the origin of the “parameter space.” It is further proved that in the case of systems with one degree of freedom only, the surface takes the form of a plane. The practical implications of these results regarding the estimation of the frequencies and/or the stability boundary of the system are discussed. Thus it is observed that, on the basis of the established theorems, lower bounds to the frequencies at any stage of external loading and/or upper bounds to the stability boundary are readily obtainable. A two-degree-of-freedom illustrative example is discussed.

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