Basin of Attraction of the Simplest Walking Model

2001 ◽  
Author(s):  
A. L. Schwab ◽  
M. Wisse
Keyword(s):  
Equations Of Motion ◽  
Basin Of Attraction ◽  
Mapping Method ◽  
Walking Robots ◽  
Natural Energy ◽  
Walking Motion ◽  
The Stability ◽  
The Basin Of Attraction ◽  
General Method ◽  
Small Disturbances

Abstract Passive dynamic walking is an important development for walking robots, supplying natural, energy-efficient motions. In practice, the cyclic gait of passive dynamic prototypes appears to be stable, only for small disturbances. Therefore, in this paper we research the basin of attraction of the cyclic walking motion for the simplest walking model. Furthermore, we present a general method for deriving the equations of motion and impact equations for the analysis of multibody systems, as in walking models. Application of the cell mapping method shows the basin of attraction to be a small, thin area. It is shown that the basin of attraction is not directly related to the stability of the cyclic motion.

On the Dynamic Stability of Self-Aligning Journal Gas Bearings

1977 ◽  
Vol 99 (4) ◽  
pp. 434-440 ◽  
Author(s):  
M. J. Cohen
Keyword(s):  
Dynamic Stability ◽  
Journal Bearing ◽  
Equations Of Motion ◽  
Stability Boundary ◽  
Initial Condition ◽  
Small Motion ◽  
Gas Bearings ◽  
Loading Case ◽  
The Stability ◽  
Small Disturbances

The report presents an investigation of the dynamic stability behaviour of self-aligning journal gas bearings when subjected to arbitrary small disturbances from an initial condition of operational equilibrium. The method is based on an approach similar to the nonlinear-ph solution of the author for the quasi-static loading case but the equations of motion of the journal are the linearized forms for small motion in the two degrees (translational) of freedom of the journal center. The stability domains for the infinite journal bearing are presented for the whole of the eccentricity (ε) and rotational speed (Λ) ranges for any given bearing geometry, in the shape of stability boundaries in that domain. It is shown that a given bearing will be stable within a corridor in the (ε, Λ) parametral domain having as its lower bound the so called “half-speed” whirl stability boundary and as its upper bound another whirling instability at a higher characteristic (relative) frequency, the instability occurs generally at the higher eccentricities and lower rotational speeds.

Finding Method and Analysis of Hidden Chaotic Attractors for Plasma Chaotic System From Physical and Mechanistic Perspectives

2020 ◽  
Vol 30 (05) ◽  
pp. 2050072 ◽  
Author(s):  
Yingjuan Yang ◽  
Guoyuan Qi ◽  
Jianbing Hu ◽  
Philippe Faradja
Keyword(s):  
Chaotic Attractor ◽  
Equilibrium Points ◽  
Basin Of Attraction ◽  
The Self ◽  
Numerical Continuation ◽  
Chaotic Attractors ◽  
Phase Portrait Analysis ◽  
The Stability ◽  
Two Parameters ◽  
The Basin Of Attraction

A method for finding hidden chaotic attractors in the plasma system is presented. Using the Routh–Hurwitz criterion, the stability distribution associated with two parameters is identified to find the region around the equilibrium points of the stable nodes, stable focus-nodes, saddles and saddle-foci for the purpose of investigating hidden chaos. A physical interpretation is provided of the stability distribution for each type of equilibrium point. The basin of attraction and parameter region of hidden chaos are identified by excluding the self-excited chaotic attractors of all equilibrium points. Homotopy and numerical continuation are also employed to check whether the basin of chaotic attraction intersects with the neighborhood of a saddle equilibrium. Bifurcation analysis, phase portrait analysis, and basins of different dynamical attraction are used as tools to distinguish visually the self-excited chaotic attractor and hidden chaotic attractor. The Casimir power reflects the error power between the dissipative energy and the energy supplied by the whistler field. It explains physically, analytically, and numerically the conditions that generate the different dynamics, such as sinks, periodic orbits, and chaos.

scholarly journals Basins of Attraction for Various Steffensen-Type Methods

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Alicia Cordero ◽  
Fazlollah Soleymani ◽  
Juan R. Torregrosa ◽  
Stanford Shateyi
Keyword(s):  
Computer Algebra System ◽  
Dynamical Behavior ◽  
Basin Of Attraction ◽  
Basins Of Attraction ◽  
Numerical Tests ◽  
Derivative Free ◽  
Iteration Functions ◽  
The Stability ◽  
Programming Package ◽  
The Basin Of Attraction

The dynamical behavior of different Steffensen-type methods is analyzed. We check the chaotic behaviors alongside the convergence radii (understood as the wideness of the basin of attraction) needed by Steffensen-type methods, that is, derivative-free iteration functions, to converge to a root and compare the results using different numerical tests. We will conclude that the convergence radii (and the stability) of Steffensen-type methods are improved by increasing the convergence order. The computer programming package MATHEMATICAprovides a powerful but easy environment for all aspects of numerics. This paper puts on show one of the application of this computer algebra system in finding fixed points of iteration functions.

Stability and Motion Control of a Unicycle (1st Report: Dynamics of a Human Riding Unicycle and Its Modeling by Link Mechanisms)

1994 ◽  
Vol 6 (2) ◽  
pp. 175-182
Author(s):  
Zaiquan Sheng ◽  
◽  
Kazuo Yamafuji
Keyword(s):  
Motion Control ◽  
Nonholonomic Constraint ◽  
Control Method ◽  
Equations Of Motion ◽  
Dynamic Equations ◽  
Lateral Stability ◽  
New Model ◽  
Dynamic Motion ◽  
The Stability ◽  
General Method

In this paper, the dynamic characteristics of a human riding a unicycle are first analyzed by observation.: Based on observation and analysis, we discovered that the rider's body, thighs and shanks create two closed link loops; and this special mechanism plays an important role in the stability of the unicycle. We then developed a new model with two closed link mechanisms and one turntable to emulate a human riding a unicycle by a robot. Considering the nonholonomic constraint between the wheel and ground and applying recently developed general method to compute the multi-closed link mechanisms' dynamic motion, we obtained the dynamic equations of motion for this new model. Using these equations, simulation is conducted under the proposed control method. The simulation result indicates that both longitudinal and lateral stability of a human riding a unicycle can be satisfactorily emulated by the new model.

scholarly journals The stability of a rising droplet: an inertialess non-modal growth mechanism

2015 ◽  
Vol 786 ◽  
Author(s):  
Giacomo Gallino ◽  
Lailai Zhu ◽  
François Gallaire
Keyword(s):  
Stability Analysis ◽  
Stokes Equations ◽  
Basin Of Attraction ◽  
Boundary Integral ◽  
Shape Evolution ◽  
Transient Growth ◽  
Critical Amplitude ◽  
Perturbation Amplitude ◽  
The Stability ◽  
The Basin Of Attraction

Prior modal stability analysis (Kojimaet al.,Phys. Fluids, vol. 27, 1984, pp. 19–32) predicted that a rising or sedimenting droplet in a viscous fluid is stable in the presence of surface tension no matter how small, in contrast to experimental and numerical results. By performing a non-modal stability analysis, we demonstrate the potential for transient growth of the interfacial energy of a rising droplet in the limit of inertialess Stokes equations. The predicted critical capillary numbers for transient growth agree well with those for unstable shape evolution of droplets found in the direct numerical simulations of Koh & Leal (Phys. Fluids, vol. 1, 1989, pp. 1309–1313). Boundary integral simulations are used to delineate the critical amplitude of the most destabilizing perturbations. The critical amplitude is negatively correlated with the linear optimal energy growth, implying that the transient growth is responsible for reducing the necessary perturbation amplitude required to escape the basin of attraction of the spherical solution.

Offset Boosting for Breeding Conditional Symmetry

2018 ◽  
Vol 28 (14) ◽  
pp. 1850163 ◽  
Author(s):  
Chunbiao Li ◽  
Julien Clinton Sprott ◽  
Yongjian Liu ◽  
Zhenyu Gu ◽  
Jingwei Zhang
Keyword(s):  
Chaotic Systems ◽  
Basin Of Attraction ◽  
Two Dimensions ◽  
Symmetric Pair ◽  
Conditional Symmetry ◽  
Coexisting Attractors ◽  
One Dimensional ◽  
Offset Boosting ◽  
The Basin Of Attraction ◽  
General Method

Symmetry is usually prevented by the broken balance in polarity. If the offset boosting returns the balance of polarity when some of the variables have their polarity reversed, the corresponding system becomes conditionally symmetric and in turn produces coexisting attractors with that type of symmetry. In this paper, offset boosting in one dimension or in two dimensions in a 3D system is made for producing conditional symmetry, where the symmetric pair of coexisting attractors exist from one-dimensional or two-dimensional offset boosting, which is identified by the basin of attraction. The polarity revision from offset boosting provides a general method for constructing chaotic systems with conditional symmetry. Circuit implementation based on FPGA verifies the coexisting attractors with conditional symmetry.

Effect of Delay on the Boundary of the Basin of Attraction in a Self-Excited Single Graded-Response Neuron

1997 ◽  
Vol 9 (2) ◽  
pp. 319-336 ◽  
Author(s):  
K. Pakdaman ◽  
C. P. Malta ◽  
C. Grotta-Ragazzo ◽  
J.-F. Vibert
Keyword(s):  
Stable Equilibrium ◽  
Equilibrium Points ◽  
Basin Of Attraction ◽  
Basins Of Attraction ◽  
Transmission Delays ◽  
The Past ◽  
Graded Response ◽  
The Stability ◽  
Delay Dependent ◽  
The Basin Of Attraction

Little attention has been paid in the past to the effects of interunit transmission delays (representing a xonal and synaptic delays) ontheboundary of the basin of attraction of stable equilibrium points in neural networks. As a first step toward a better understanding of the influence of delay, we study the dynamics of a single graded-response neuron with a delayed excitatory self-connection. The behavior of this system is representative of that of a family of networks composed of graded-response neurons in which most trajectories converge to stable equilibrium points for any delay value. It is shown that changing the delay modifies the “location” of the boundary of the basin of attraction of the stable equilibrium points without affecting the stability of the equilibria. The dynamics of trajectories on the boundary are also delay dependent and influence the transient regime of trajectories within the adjacent basins. Our results suggest that when dealing with networks with delay, it is important to study not only the effect of the delay on the asymptotic convergence of the system but also on the boundary of the basins of attraction of the equilibria.

Effect of natural convection on stability of flow in a vertical pipe

1962 ◽  
Vol 14 (2) ◽  
pp. 244-256 ◽  
Author(s):  
George F. Scheele ◽  
Thomas J. Hanratty
Keyword(s):  
Heat Flux ◽  
Velocity Profile ◽  
Unsteady Flow ◽  
Flow Instability ◽  
Equations Of Motion ◽  
Constant Heat Flux ◽  
Vertical Pipe ◽  
Unstable Flow ◽  
The Stability ◽  
Small Disturbances

If water is heated or cooled while flowing through a vertical pipe with a laminar motion, the velocity profile will differ from the parabolic shape for isothermal flow due to density variations in the fluid. If a constant heat flux is used at the wall and if the changes in temperature affect only the density appearing in the gravity term of the equations of motion, a condition is attained far downstream in the heat-transfer section such that there is no further change in the velocity profile. The shape of this fully developed velocity profile depends on the ratio of the heat flux to the flow rate. The stability of flow in an electrically heated pipe 762 diameters long was studied by detecting temperature fluctuations in the effluent. By use of a carefully designed entry and a long isothermal section prior to the heat exchange section, inlet disturbances were eliminated and transition to an unsteady flow resulted from a natural instability of the distorted profiles. It was found that the stability depends primarily on the shape of the velocity profile and only secondarily on the value of the Reynolds number, if at all. For upflow heating the flow first becomes unstable when the velocity profiles develop points of inflexion. Transition to an unsteady flow involves the gradual growth of small disturbances and therefore it is quite possible to have unstable flows without observing transition because the pipe is not long enough for the disturbances to attain a measurable amplitude. For downflow heating the flow instability is associated with separation at the wall. Transition to an unsteady flow is sudden and therefore transition occurs shortly after an unstable flow occurs. It is suggested that a change from a steady symmetrical to a steady unsymmetrical flow occurs in downflow when the profile develops points of inflexion.

ACHIEVING ENERGY-EFFICIENT BIPEDAL WALKING TRAJECTORY THROUGH GA-BASED OPTIMIZATION OF KEY PARAMETERS

2009 ◽  
Vol 06 (04) ◽  
pp. 609-629 ◽  
Author(s):  
VAN-HUAN DAU ◽  
CHEE-MENG CHEW ◽  
AUN-NEOW POO
Keyword(s):  
Energy Efficient ◽  
Polynomial Interpolation ◽  
Bipedal Walking ◽  
Walking Robots ◽  
Bipedal Robot ◽  
Cartesian Space ◽  
Walking Motion ◽  
Walking Performance ◽  
Zero Moment ◽  
The Stability

This paper proposes a method of energy-efficient trajectory planning for bipedal walking robots. In this study, we plan hip and foot trajectories in Cartesian space using polynomial interpolation. The seven key parameters which define the hip and foot trajectories are optimized by genetic algorithm (GA). Since the hip trajectory is crucial to the stability and walking performance of bipedal robot, we introduce a way to increase hip trajectory's variation by extending the order of the interpolated polynomial and using a set of key parameters. To ensure stable walking motion, we employ the zero-moment-point (ZMP) as the stability criterion. The effectiveness of our proposed method is verified by two simulation examples (flat terrain walking and slope walking) of a humanoid robot named NUSBIP-II.

Lyapunov’s Stability of Nonlinear Misaligned Journal Bearings

1995 ◽  
Vol 117 (3) ◽  
pp. 576-581 ◽  
Author(s):  
P. G. Nikolakopoulos ◽  
C. A. Papadopoulos
Keyword(s):  
Journal Bearing ◽  
Direct Method ◽  
Equations Of Motion ◽  
Orbital Stability ◽  
Element Formulation ◽  
Nonlinear Stiffness ◽  
Lyapunov Direct Method ◽  
Rotor Bearing ◽  
The Stability ◽  
General Method

In this paper the stability of nonlinear misaligned rotor-bearing systems is investigated, using the Lyapunov direct method. A finite element formulation is used to determine the journal bearing pressure distribution. Then the linear and nonlinear stiffness, damping, and hybrid (depending on both displacement and velocity) coefficients are calculated. A general method of analysis based on Lyapunov’s stability criteria is used to investigate the stability of nonlinear misaligned rotor bearing systems. The equations of motion of the rigid rotor on the nonlinear bearings are used to find a Lyapunov function using some of these coefficients, which depend on L/D ratio and the misalignment angles ψx, ψy. The analytical conditions for the stability or instability of some examined cases are given and some examples for the orbital stability are also demonstrated.

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