Ride dynamics mathematical model for a single station representation of tracked vehicle

Tracked vehicles are exposed to severe ride environment due to dynamic terrain-vehicle interactions. Hence it is essential to understand the vibration levels transmitted to the vehicle, as it negotiates different types of terrains at different speeds. The present study is focused on the development of single station representation of tracked vehicles with trailing arm hydro-gas suspension systems, simulating the ride dynamics. The kinematics of hydro-gas suspension system have been derived in order to determine the non-linear stiffness characteristics at various charging pressures. Then, incorporating the actual suspension kinematics, non-linear governing equations of motion have been derived for the sprung and unsprung masses and solved by coding in Matlab. Effect of suspension non-linear dynamics on the single station ride vibrations have been analyzed and validated with a multi-body dynamics model developed using MSC.ADAMS. The above mathematical models would help in estimating the ride vibration levels of the tracked vehicle, negotiating different types of terrains at various speeds and also enable the designers to fine-tune the suspension characteristics such that the ride vibrations are within acceptable limits. The mathematical ride model would also assist in development of non-linear ride vibration model of full tracked vehicle and estimate the sprung mass dynamics.     

Global dynamic scenarios in a discrete-time model of renewable resource exploitation: a mathematical study

Nonlinear Dynamics - We consider the two-dimensional map introduced in Bischi et al. (J Differ Equ Appl 21(10):954–973, 2015) formulated as a model for a renewable resource exploitation...     

Global stability of a delayed HIV infection model with nonlinear incidence rate

Under the assumption that the incidence rate of the infection and the removal rate of the infective by cytotoxic T lymphocytes are nonlinear, we study the global dynamics of a HIV infection model with the response of the immune system using characteristic equation, the Fluctuation lemma, and the direct Lyapunov method. The existence of a threshold parameter, i.e., the basic reproduction number or basic reproductive ratio is established and the global stability of the equilibria is discussed.     

Global qualitative analysis of tippe top dynamics

The tippe top is a dynamically and geometrically symmetric body supported by a horizontal plane. If one twists the tippe top rapidly about the symmetry axis so that the symmetry axis is vertical and its center of mass takes the lowest position, then it turns upside down by 180° and stats to rotate about the same symmetry axis with the center of mass occupying the highest position. A local analysis of tippe top dynamics (in a neighborhood of its rotations about the vertical symmetry axis) is given in [1, 2]. The simplest model of the tippe top is a dynamically symmetric inhomogeneous ball whose center of mass lies on the dynamic symmetry axis but does not coincide with its geometric center. Such a model allows global qualitative analysis of the top dynamics.     

On the stability of the solution to a gonorrhea discrete mathematical model

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Global dynamics of a multi-strain SEIR epidemic model with general incidence rates: application to COVID-19 pandemic

Nonlinear Dynamics - This paper investigates the global stability analysis of two-strain epidemic model with two general incidence rates. The problem is modelled by a system of six nonlinear...     

Global dynamics of a flexible asymmetrical rotor

Nonlinear Dynamics - Global dynamics of a flexible asymmetrical rotor resting on vibrating supports is investigated. Hamilton’s principle is used to derive the partial differential governing...     

Global dynamics perspective on macro- to nano-mechanics

Nonlinear Dynamics - In about the last two decades, global nonlinear dynamics has been evolving in a revolutionary way, with the development of sophisticated techniques employing concepts/tools of...     

Dynamic analysis of mathematical model of ethanol fermentation with gas stripping

In this paper, a mathematical model for ethanol fermentation with gas stripping is investigated. Firstly, the model with continuous substrate input is taken. We study the existence and local stability of two equilibrium points. According to Poincare–Bendixson Theorem, the sufficient condition for the globally asymptotical stability of positive equilibrium point is obtained, which implies that we can get stable ethanol product. Secondly, we study the model with impulsive substrate input and obtain the sufficient condition for the local stability of cell-free periodic solution by using the Floquet’s theory of impulsive differential equation and small-amplitude perturbation skills. In a certain limiting case, it is shown that a nontrivial periodic solution emerges via a supercritical (subcritical) bifurcation. Finally, our results are confirmed by means of numerical simulation.     

A generalized mathematical model to analyze the nonlinear behavior of a controlled gyroscope in gimbals

In this paper, the effect of the parameter variation on the stability and dynamic behavior of a gyroscope in gimbals with a feedback control system, formed by a Proportional + Integral $+$ Derivative (PID) controller and a DC motor with an ideal train gear is researched. The generalized mathematical model of the gyro is obtained from the Euler-Lagrange equations by using the nutation theory of the gyroscope. The use of approximated models of the control system are deduced from the mathematical model of the gyro, taking into account that the integral action of the PID controller is constrained and that the inductance of the DC motor may be negligible. The analysis and choice of appropriate state variables to simulate the dynamic behavior of different models of the gyro are also considered. The paper shows that from the analysis of the equilibrium points, a Bogdanov Takens and a Poincaré-Andronov-Hopf bifurcation can appear. These bifurcations are analyzed from the calculation of a parameter which is known as the first Lyapunov value, showing that it is possible to deduce a procedure to find out when a complicated model can be substituted by a simpler one. In particular, the possibility of self-oscillating and chaotic behavior for different models of the system by using the first Lyapunov value as a function of the parameters of the PID controller is researched. Numerical simulations have been performed to evaluate the analytical results and the mathematical discussions.     

Wave features related to a mathematical model describing pulse transmission in a nerve fibre

In order to describe the signal transmission in a nerve fibre, we consider a non-linear mathematical model which takes into account several dissipative mechanisms. By assuming different orders of magnitude for the relaxation times associated with each of them, we carry out an asymptotic analysis pointing out the wave features in different situations.     

A mathematical model for the waste region of a long-wall mineworking

The mechanical behaviour of the broken rock material occupying the waste region of a long-wall mineworking is investigated. A mathematical model is proposed, developed from physical considerations, which is based upon the continuum, plane strain, rigid-plastic theory for double-shearing flows of compressible granular materials. The model comprises the stress equilibrium equations, the Coulomb yield criterion, kinematic equations due to Mehrabadi and Cowin (1978) and the continuity equation, together with the waste region geometry and the boundary conditions imposed upon the field variables. Statical indeterminancy is a property of the formulation and this results in a connection between the stress and velocity fields through the boundary conditions. A strategy is presented for the iterative construction of the stress and velocity fields and approximations to solutions of the equations of the model are obtained numerically.     

A mathematical model of the ring-spinning process

This paper develops a mathematical model of the ring-spinning process that takes into account its non-stationary nature. A complex system of differential equations is obtained, which from a mathematical point of view constitutes a ‘free-boundary’ problem. Its solution involves definition of suitable boundary conditions related to the mechanical characteristics of the process and of the spinning machine itself. The boundary conditions which determine the solution are pointed out. A numerical solution of the system of differential equations can be obtained by the Finite-Segments method, as shown in an example.     

A mathematical model of the arterial system

Summary A mathematical model of the major arteries of sistemic circulation in the man is proposed. According to the model, flow is regarded as a one-dimensional whole. The numerical solution is obtained with the method of characteristics, applied to the case of an elastic, incompressible vessel wall. The model is applied to study the behaviour of six different cases. The results show that the model provide an appropriate representation of the behaviour of the major arteries in the sistemic circulation.

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Sommario Viene proposto un modello matematico per lo studio del comportamento meccanico del sistema circolatorio arterioso. Il modello utilizza lo schema di processo unidimensionale normalmente impiegato in meccanica dei fluidi; la soluzione è ottenuta con il metodo delle caratteristiche per il caso di tubi con comportamento elastico. Il modello à stato applicato a sei diverse situazioni. I risultati ottenuti mostrano la buona validità del modello matematico proposto.

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Research supported by C.N.R.     

A mathematical model of the stokes soliton

A mathematical model of a solitary wave of limiting amplitude propagating in a constant-depth channel is developed. The model is based on a conformal mapping of the domain of variation of a complex potential onto a domain approximating the domain of Stokes soliton flow. The results of the model are compared with the known numerical results. Using the model, the streamlines in both movable and fixed coordinate systems, as well as the isotachs, isoclinals, and isobars of the Stokes soliton, are constructed. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 174–180, January–February, 1999.     

Application of the nonsmooth dynamics approach to model and analysis of the contact-impact events in cam-follower systems

The dynamic modeling and analysis of planar rigid multibody systems that experience contact-impact events is presented and discussed throughout this work. The methodology is based on the nonsmooth dynamics approach, in which the interaction of the colliding bodies is modeled with multiple frictional unilateral constraints. Rigid multibody systems are stated as an equality of measures, which are formulated at the velocity-impulse level. The equations of motion are complemented with constitutive laws for the forces and impulses in the normal and tangential directions. In this work, the unilateral constraints are described by a set-valued force law of the type of Signorini??s condition, while the frictional contacts are characterized by a set-valued force law of the type of Coulomb??s law for dry friction. The resulting contact-impact problem is formulated and solved as an augmented Lagrangian approach, which is embedded in the Moreau time-stepping method. The effectiveness of the methodologies presented in this work is demonstrated throughout the dynamic simulation of a cam-follower system of an industrial cutting file machine.