Sovan Sundar Dasgupta

Bio: Sovan Sundar Dasgupta is an academic researcher from VIT University. The author has contributed to research in topics: Energy source & Mechanical energy. The author has an hindex of 3, co-authored 4 publications receiving 18 citations.

Attenuation of Sommerfeld effect in an internally damped eccentric shaft-disk system via active magnetic bearings

Abstract: Eccentric shaft-disk system with internal damping driven by a non-ideal power source exhibits Sommerfeld effect characterized by nonlinear jump phenomena of amplitude and rotor speed upon exceeding a critical power input around the critical speed. This effect causes instability in high speed rotors. So the diminution of such effect is extremely important in order to smooth running of the rotors at high speeds. The aim of this paper is to attenuate the Sommerfeld effect of an internally damped unbalanced flexible shaft-disk system via linearized active magnetic bearings. The shaft-disk system is excited through a brushed DC motor which acts as a non-ideal energy source. The characteristic equation of fifth order polynomial in rotor speed is obtained through energy balance of supplied power and the mechanical power dissipated at steady-state condition. Using MATLAB simulations, amplitude frequency responses are obtained close to system resonance for several values of bias current of active magnetic bearings. Thus the Sommerfeld effect is found to be attenuated as bias current increases gradually. The complete disappearance of Sommerfeld effect is also reported when the bias current reaches a specific value under certain conditions. A few numerical results are validated with established results when bias current is made to zero.

Dynamic characterization of a flexible internally damped spinning shaft with constant eccentricity

Abstract: In the present study, the dynamic characterization of a flexible spinning shaft with constant eccentricity driven by a non-ideal energy source (DC motor) with external and internal damping has been focused. It is well established that the structural response of a vibratory system to which a non-ideal drive is connected may act as an energy sink under certain conditions such that a part of the energy supplied by the source is spent to vibrate the structure rather than to increase the drive speed. This phenomenon is formally known as the Sommerfeld effect. The Sommerfeld effect characterized by jump phenomena is studied through the steady-state amplitude obtained by instantaneous power balance method and further verified through numerical simulation. Finally, power balance equation is transformed into a characteristic equation through which jump phenomena and Sommerfeld effect are predicted numerically for the first and third modes using root loci method. The break-in and breakaway points of the root loci represent the values of the supply voltage at which jumps in shaft speed and flexural vibration amplitudes take place during coast-up and coast-down operation.

Dynamic Characterization of a Bistable Energy Harvester Under Gaussian White Noise for Larger Time Constant

Abstract: In this paper, the system parameters of a nonlinear bistable energy harvester excited by Gaussian white noise was investigated. Using Fokker–Planck–Kolmogorov equation, the probability distribution functions of displacement and velocity of the oscillator are obtained. The effect of various system parameters on the probability distributions of displacement and velocity of the oscillator and the mean square of the output voltage are investigated when the time constant of the piezoelectric circuit takes a larger value to achieve maximum voltage gain. The maximum peak values of the joint probability distribution of displacement and velocity of the oscillator decrease with the larger values of noise strength. The effect of parameters of bistable potential function on mean square of output voltage was also investigated. The system equations are numerically solved and mean square value of output voltage is numerically estimated and is seen to be increased as noise intensity increases and decreased as viscous damping increases. The result also shows that better power output can be achieved when the time constant takes larger value.

A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008–2018)

Abstract: Energy harvesting technologies have been explored by researchers for more than two decades as an alternative to conventional power sources (e.g. batteries) for small-sized and low-power electronic devices. The limited life-time and necessity for periodic recharging or replacement of batteries has been a consistent issue in portable, remote, and implantable devices. Ambient energy can usually be found in the form of solar energy, thermal energy, and vibration energy. Amongst these energy sources, vibration energy presents a persistent presence in nature and manmade structures. Various materials and transduction mechanisms have the ability to convert vibratory energy to useful electrical energy, such as piezoelectric, electromagnetic, and electrostatic generators. Piezoelectric transducers, with their inherent electromechanical coupling and high power density compared to electromagnetic and electrostatic transducers, have been widely explored to generate power from vibration energy sources. A topical review of piezoelectric energy harvesting methods was carried out and published in this journal by the authors in 2007. Since 2007, countless researchers have introduced novel materials, transduction mechanisms, electrical circuits, and analytical models to improve various aspects of piezoelectric energy harvesting devices. Additionally, many researchers have also reported novel applications of piezoelectric energy harvesting technology in the past decade. While the body of literature in the field of piezoelectric energy harvesting has grown significantly since 2007, this paper presents an update to the authors' previous review paper by summarizing the notable developments in the field of piezoelectric energy harvesting through the past decade.

Attenuation of Sommerfeld effect in an internally damped eccentric shaft-disk system via active magnetic bearings

Abstract: Eccentric shaft-disk system with internal damping driven by a non-ideal power source exhibits Sommerfeld effect characterized by nonlinear jump phenomena of amplitude and rotor speed upon exceeding a critical power input around the critical speed. This effect causes instability in high speed rotors. So the diminution of such effect is extremely important in order to smooth running of the rotors at high speeds. The aim of this paper is to attenuate the Sommerfeld effect of an internally damped unbalanced flexible shaft-disk system via linearized active magnetic bearings. The shaft-disk system is excited through a brushed DC motor which acts as a non-ideal energy source. The characteristic equation of fifth order polynomial in rotor speed is obtained through energy balance of supplied power and the mechanical power dissipated at steady-state condition. Using MATLAB simulations, amplitude frequency responses are obtained close to system resonance for several values of bias current of active magnetic bearings. Thus the Sommerfeld effect is found to be attenuated as bias current increases gradually. The complete disappearance of Sommerfeld effect is also reported when the bias current reaches a specific value under certain conditions. A few numerical results are validated with established results when bias current is made to zero.