Numerical methods for Engineers and Scientists

The current paper investigates the dynamical property of a pendulum attached to a rotating rigid frame with a constant angular velocity about the vertical axis passing to the pivot point of the pendulum. He’s homotopy perturbation method is used to obtain the analytic solution of the governing nonlinear differential equation of motion. The fourth-order Runge-Kutta method (RKM) and He’s frequency formulation are used to verify the high accuracy of the obtained solution. The stability condition of the motion is examined and discussed. Some plots of the time histories of the gained solutions are portrayed graphically to reveal the impact of the distinct parameters on the dynamical motion.

Periodic Property and Instability of a Rotating Pendulum System

This work focuses on vibration alleviation and energy harvesting in a dynamical system of a spring-pendulum. The structure of the pendulum is modified using an independent electromagnetic harvesting system. The harvesting depends on the oscillation of a magnet in a coil. An endeavor has been made to get both the energy harvesting and mitigation of vibration efficacy of the harvester. The governing kinematics equations are derived using Lagrange’s equations and are solved asymptotically using the multiple scales method to achieve the intended outcome as new and precise results. The resonance states are classified, and the influence of various parameters of the studied system is analyzed. Fixed points at steady states are categorized into stable and unstable. The time behavior of the solutions, the modified amplitudes, and phases are examined and interpreted in the light of their graphical plots. Zones of stability and instability are concerned, in which the system’s behavior is stable for a wide range of used parameters. This model has become essential in recent times as it uses control sensors in industrial applications, buildings, infrastructure, automobiles, and transportation.

https://journals.sagepub.com/doi/pdf/10.1177/14613484221077474

Controlling the kinematics of a spring-pendulum system using an energy harvesting device

The simplest frequency formulation for nonlinear oscillators is introduced and proved, and a modification is suggested. A fractal vibration in a porous medium is introduced, and its low-frequency property is elucidated by the frequency formulation. It reveals that the inertia force in a fractal space is equivalent to a couple of the inertia force and the damping force for the traditional differential model. 

A modified frequency–amplitude formulation for fractal vibration systems

This paper presents the motion of a harmonically excited dynamical system with three degrees of freedom (3-DOF) in which it consists of a connected rigid body with a damped spring pendulum whose suspension point moves in a Lissajous curve path. Multiple scales method is utilized to obtain the asymptotic solutions of the equations of motion up to third approximation. Some types of resonances and the conditions of solvability for the steady state solutions have been clarified in light of the achieved modulation equations. The temporal representation of the achieved solutions and resonance curves are presented in some plots to show the good effect of the distinct parameters on the dynamical motion of the investigated system. The numerical solutions of the governing system of motion are gained utilizing the Runge-Kutta method from fourth order. The comparison between these solutions and the analytical ones reflects the good accuracy of the analytical solutions and the used perturbation techniques.

On the motion of a damped rigid body near resonances under the influence of harmonically external force and moments

The dynamical motion of a gyrostat for the irrational frequency case

This paper investigates the motion of a dynamically symmetric rigid body about one of its fixed points in which it is incurred to Newtonian force field, electromagnetic field and external torques. These torques acted in the direction of the principal axes of the body and are represented by perturbing and gyrostatic torques. The body rotates initially about the symmetry dynamic axis with high angular velocity. Therefore, a small parameter can be introduced. The averaging method is applied to convert the governing system of motion into another convenient averaging one in terms of a small parameter. The asymptotic analytical solutions of the latter system are obtained for some distinct applications depending upon the perturbing torques and the restoring one. The good effect of the body parameters on the motion is clarified in the graphical representations of the obtained solutions of the considered applications. The significance of this work is due to its great implementation of practical life like submarines, devices that maintain the stability and measure the orientations of airplanes and for several physics and engineering applications.

The asymptotic solutions of the governing system of a charged symmetric body under the influence of external torques

This paper attempts to explore the general rotatory 3D motion of a magnetic heavy solid body around one fixed point under the impact of a gyrostatic moment when the body awarded initially high angular velocity about one of its inertia principal axes. The asymptotic technique of Krylov-Bogoliubov-Mitropolski and its adjustment are applied to achieve new asymptotic periodic solutions of the controlling equations of motion. Discussion of these solutions is presented taking into consideration their graphs representations. The graphical depictions of such solutions and their corresponding phase planes are plotted to give an induction about its behaviour during the interval time of motion and to reveal the good effect of the different applied forces and moments on the body's motion. The application of the achieved results of the present work can be widely found in gyroscopic devices especially that used inertia reference systems like in satellites, airplanes, and missiles. Moreover, for devices that are responsible for the stability of motion for these applications.

The 3D motion of a charged solid body using the asymptotic technique of KBM

In this article, a nonlinear dynamical system with three degrees of freedom (DOF) consisting of multiple pendulum (MP) is investigated. The motion of this system is restricted to be in a vertical plane, in which its pivot point moves in a circular path with constant angular velocity, under the action of an external harmonic force and a moment acting perpendicular to the direction of last arm of MP and at the suspension point respectively. Multiple scales technique (MST) among others perturbation methods is used to obtain the approximate solutions of the equations of motion up to the third approximation because it is authorizing to execute a specific analysis of the system behaviour and to realize the solvability conditions in view of the resonance cases. The stability of the considered dynamical model utilizing nonlinear stability analysis approach is examined. The solutions diagrams and resonance curves are drawn to illustrate the extent of the effect of various parameters on the solutions. The importance of this work is due to its uses in human or robotic walking analysis.

A. A. Galal

Papers

Periodic Property and Instability of a Rotating Pendulum System

The dynamical motion of a gyrostat for the irrational frequency case

The asymptotic solutions of the governing system of a charged symmetric body under the influence of external torques

The 3D motion of a charged solid body using the asymptotic technique of KBM

On the motion of a triple pendulum system under the influence of excitation force and torque