Barun Pratiher

Bio: Barun Pratiher is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Nonlinear system & Multiple-scale analysis. The author has an hindex of 11, co-authored 35 publications receiving 307 citations. Previous affiliations of Barun Pratiher include Indian Institute of Technology Dhanbad & Indian Institutes of Technology.

Non-linear dynamics of a flexible single link Cartesian manipulator

Abstract: The present work deals with the non-linear vibration of a harmonically excited single link roller-supported flexible Cartesian manipulator with a payload. The governing equation of motion of this system is developed using extended Hamilton's principle, which is reduced to the second-order temporal differential equation of motion, by using generalized Galerkin's method. This equation of motion contains both cubic non-linearities of geometric and inertial type in addition to linear forced and non-linear parametric excitation terms. Method of multiple scales is used to solve this non-linear equation and study the stability and bifurcations of the system. Influence of amplitude of the base excitation and mass ratio on the steady state response of the system is investigated for both simple and subharmonic resonance conditions. Critical bifurcation points are determined from the fixed-point responses and periodic, quasi-periodic responses are also found for different system parameters. The results obtained using the perturbation analysis are compared with the previously published experimental work and are found to be in good agreement. This work will be useful for the designer of a flexible manipulator.

Parametric instability of a cantilever beam with magnetic field and periodic axial load

Abstract: The present work deals with the parametric instability regions of a cantilever beam with tip mass subjected to time-varying magnetic field and axial force. The nonlinear temporal differential equation of motion having two frequency parametric excitations is solved using second-order method of multiple scales. The closed-form expressions for the parametric instability regions for three different resonance conditions are determined. The influence of magnetic filed, axial load, damping constant and mass ratio on the parametric instability regions are investigated. These results obtained from perturbation analysis are verified by solving the temporal equation of motion using fourth-order Runge–Kutta method. The instability regions obtained using this method is found to be in good agreement with the experimental result.

Nonlinear vibrations and frequency response analysis of a cantilever beam under periodically varying magnetic field

Abstract: In this paper, nonlinear vibration of a cantilever beam with tip mass subjected to periodically varying axial load and magnetic field has been studied. The temporal equation of motion of the system containing linear and nonlinear parametric excitation terms along with nonlinear damping, geometric and inertial types of nonlinear terms has been derived and solved using method of multiple scales. The stability and bifurcation analysis for three different resonance conditions were investigated. The numerical results demonstrate that while in simple resonance case with increase in magnetic field strength, the system becomes unstable, in principal parametric or simultaneous resonance cases, the vibration can be reduced significantly by increasing the magnetic field strength. The present work will be very useful for feed forward vibration control of magnetoelastic beams which are used nowadays in many industrial applications.

Nonlinear modeling and vibration analysis of a two-link flexible manipulator coupled with harmonically driven flexible joints

Abstract: The present paper deals with the theoretical studies to determine the modal parameters and investigate the dynamic instability of a harmonically driven planar two-link manipulator with flexible joints. An appropriate dynamic model incorporating both link and joint flexibilities subjected to a harmonic motion has been developed while joint flexibility has been modeled as a combination of torsional spring-inertia elements. Modal parameters for various modes of vibration have been evaluated and graphically demonstrated. Then, method of multiple scales has been employed to further analyze the vibration attributes of steady state responses and their stability under resonance condition. The comparative mode shapes and bifurcation diagrams those describe the vibrating system have been illustrated to demonstrate the dynamics of the flexible manipulator. The effect of geometric and inertial coupling existing between the flexible arms on bifurcation states and stability of the obtained solutions has been thoroughly investigated. Analytically obtained results have been verified numerically and found to be in good agreement. The present theoretical results deliver a useful insight into the attributes of vibration characteristics along with the nonlinear dynamic behavior and operational stability of two-link flexible manipulator under joint motion.

Vibration control of a transversely excited cantilever beam with tip mass

Abstract: The problem of controlling the vibration of a transversely excited cantilever beam with tip mass is analyzed within the framework of the Euler–Bernoulli beam theory A sinusoidally varying transverse excitation is applied at the left end of the cantilever beam, while a payload is attached to the free end of the beam An active control of the transverse vibration based on cubic velocity is studied Here, cubic velocity feedback law is proposed as a devise to suppress the vibration of the system subjected to primary and subharmonic resonance conditions Method of multiple scales as one of the perturbation technique is used to reduce the second-order temporal equation into a set of two first-order differential equations that govern the time variation of the amplitude and phase of the response Then the stability and bifurcation of the system is investigated Frequency–response curves are obtained numerically for primary and subharmonic resonance conditions for different values of controller gain The numerical results portrayed that a significant amount of vibration reduction can be obtained actively by using a suitable value of controller gain The response obtained using method of multiple scales is compared with those obtained by numerically solving the temporal equation of motion and are found to be in good agreement Numerical simulation for amplitude is also obtained by integrating the equation of motion in the frequency range between 1 and 3 The developed results can be extensively used to suppress the vibration of a transversely excited cantilever beam with tip mass or similar systems actively

Review of Control and Sensor System of Flexible Manipulator

Abstract: Over the last few decades, extensive use of flexible manipulators in various robotic applications has made it as one of the research interests for many scholars over the world. Recent studies on the modeling, sensor systems and controllers for the applications of flexible robotic manipulators are reviewed in order to complement the previous literature surveyed by Benosman & Vey (Robotica 22:533---545, 2004) and Dwivedy & Eberhard (Mech. Mach. Theory 41:749---777, 2006) . A brief introduction of the essential modeling techniques is first presented, followed by a review of the practical alternatives of sensor systems that can help scientists or engineers to choose the appropriate sensors for their applications. It followed by the main goal of this paper with a comprehensive review of the control strategies for the flexible manipulators and flexible joints that were studied in recent literatures. The issues for controlling flexible manipulators are highlighted. Most of the noteworthy control techniques that were not covered in the recent surveys in references (Benosman & Vey Robotica 22:533---545, 2004; Dwivedy & Eberhard Mech. Mach. Theory 41:749---777, 2006) are then reviewed. It concludes by providing some possible issues for future research works.

A multi-stable energy harvester: Dynamic modeling and bifurcation analysis

Abstract: A theoretical investigation is conducted on the dynamic and energetic characteristics of a multi-stable bimorph cantilever energy harvester that uses magnetic attraction effect. The multi-stable energy harvester under study is composed of a bimorph cantilever beam with soft magnetic tip and two externally fixed permanent magnets that are arranged in series. With this configuration, the magnetic force and the moment that are exerted on the cantilever tip tend to be highly dependent on the magnetic field induced by the external magnets. Such an energy harvester can possess multi-stable potential functions, ranging from mono-stable to penta-stable. The mechanism that governs the formation of this multi-stability is thoroughly identified and examined thorough a bifurcation analysis performed on the system׳s equilibrium solutions. From this analysis, it is found that the transitions between these multi-stable states occur through very complicated bifurcation scenarios that include degenerate pitchfork bifurcations and mergers of pitchfork bifurcations or saddle-node bifurcations. Bifurcation set diagram is obtained, which is composed of five separate parametric regions, from mono- to penta-stability. The resulting stability map satisfactorily describes the multi-stable characteristics of the present energy harvester. In addition, the dynamic and energetic characteristics of the present multi-stable energy harvester are more thoroughly examined using its potential energy diagrams and a series of numerical simulations, and the obtained results are compared with those for the equivalent bi-stable cases.

Redox-Active Quasi-Solid-State Electrolytes for Thermal Energy Harvesting

Abstract: Thermoelectrochemical cells (TECs) are a promising and cost-effective approach to harvesting waste thermal energy. For the widespread uptake of this new technology and the development of flexible, leak-free devices, solidification of the redox electrolyte is key. Thus, here we report the first quasi-solid-state electrolyte incorporating the ferri/ferrocyanide redox couple within a cellulose matrix. The electrolyte with 5 wt % cellulose achieved an optimum balance of mechanical properties, Seebeck coefficients, and diffusion coefficients and supported power outputs comparable to those of the liquid electrolyte systems.