Vibration reduction of a pipe conveying fluid using the semi-active electromagnetic damper

Kavianipour, Omid Techno-Press 2017 Coupled systems mechanics Vol.6 No.2

This paper deals with a uniform cantilever Euler-Bernoulli beam subjected to follower and transversal force at its free end as a model for a pipe conveying fluid under electromagnetic damper force. The electromagnetic damper is composed of a permanent-magnet DC motor, a ball screw and a nut. The main objective of the current work is to reduce the pipe vibration resulting from the fluid velocity and allow it to transform into electric energy. To pursue this goal, the stability and vibration of the beam model was studied using Ritz and Newmark methods. It was observed that increasing the fluid velocity results in a decrease in the motion of the free end of the pipe. The results of simulation showed that the designed semiactive electromagnetic damper controlled by on-off damping control strategy decreased the vibration amplitude of the pipe about 5.9% and regenerated energy nearly 1.9 (mJ/s). It was also revealed that the designed semi-active electromagnetic damper has better performance and more energy regeneration than the passive electromagnetic damper.

Reduction of the actuator oscillations in the flying vehicle under a follower force

Kavianipour, O.,Khoshnood, A.M.,Sadati, S.H. Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.2

Flexible behaviors in new aerospace structures can lead to a degradation of their control and guidance system and undesired performance. The objectives of the current work are to analyze the vibration resulting from the propulsion force on a Single Stage to Orbit (SSTO) launch vehicle (LV). This is modeled as a follower force on a free-free Euler-Bernoulli beam consisting of two concentrated masses at the two free ends. Once the effects on the oscillation of the actuators are studied, a solution to reduce these oscillations will also be developed. To pursue this goal, the stability of the beam model is studied using Ritz method. It is determined that the transverse and rotary inertia of the concentrated masses cause a change in the critical follower force. A new dynamic model and an adaptive control system for an SSTO LV have been developed that allow the aerospace structure to run on its maximum bearable propulsion force with the optimum effects on the oscillation of its actuators. Simulation results show that such a control model provides an effective way to reduce the undesirable oscillations of the actuators.

Effects of damping on the linear stability of a free-free beam subjected to follower and transversal forces

Kavianipour, O.,Sadati, S.H. Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.6

In this paper a free-free uniform beam with damping effects subjected to follower and transversal forces at its end is considered as a model for a space structure. The effect of damping on the stability of the system is first investigated and the effects of the follower and transversal forces on the vibration of the beam are shown next. Proportional damping model is used in this work, hence, the effects of both internal (material) and external (viscous fluid) damping on the system are noted. In order to derive the frequency of the system, the Ritz method has been used. The mode shapes of the system must therefore be extracted. The Newmark method is utilized in the study of the system vibration. The results show that an increase in the follower and transversal forces leads to an increase of the vibrational motion of the beam which is not desirable.

Effects of damping on the linear stability of a free-free beam subjected to follower and transversal forces

O. Kavianipour,S.H. Sadati 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.6

In this paper a free-free uniform beam with damping effects subjected to follower and transversal forces at its end is considered as a model for a space structure. The effect of damping on the stability of the system is first investigated and the effects of the follower and transversal forces on the vibration of the beam are shown next. Proportional damping model is used in this work, hence, the effects of both internal (material) and external (viscous fluid) damping on the system are noted. In order to derive the frequency of the system, the Ritz method has been used. The mode shapes of the system must therefore be extracted. The Newmark method is utilized in the study of the system vibration. The results show that an increase in the follower and transversal forces leads to an increase of the vibrational motion of the beam which is not desirable.

Reduction of the actuator oscillations in the flying vehicle under a follower force

O. Kavianipour,A.M. Khoshnood,S.H. Sadati 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.2

Flexible behaviors in new aerospace structures can lead to a degradation of their control and guidance system and undesired performance. The objectives of the current work are to analyze the vibration resulting from the propulsion force on a Single Stage to Orbit (SSTO) launch vehicle (LV). This is modeled as a follower force on a free-free Euler-Bernoulli beam consisting of two concentrated masses at the two free ends. Once the effects on the oscillation of the actuators are studied, a solution to reduce these oscillations will also be developed. To pursue this goal, the stability of the beam model is studied using Ritz method. It is determined that the transverse and rotary inertia of the concentrated masses cause a change in the critical follower force. A new dynamic model and an adaptive control system for an SSTO LV have been developed that allow the aerospace structure to run on its maximum bearable propulsion force with the optimum effects on the oscillation of its actuators. Simulation results show that such a control model provides an effective way to reduce the undesirable oscillations of the actuators.

Investigation of the semi-active electromagnetic damper

Morteza Montazeri-Gh,Omid Kavianipour 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.13 No.3

In this paper, the electromagnetic damper (EMD), which is composed of a permanent-magnet rotary DC motor, a ball screw and a nut, is considered to be analyzed as a semi-active damper. The main objective pursued in the paper is to study the two degrees of freedom (DOF) model of the semi-active electromagnetic suspension system (SAEMSS) performance and energy regeneration controlled by on-off and continuous damping control strategies. The nonlinear equations of the SAEMSS must therefore be extracted. The effects of the EMD characteristics on ride comfort, handling performance and road holdingfor the passive electromagnetic suspension system (PEMSS) are first analyzed and damping control strategies effects on the SAEMSS performance and energy regeneration are investigated next. The results obtained from the simulation show that the SAEMSS provides better performance and more energy regeneration than the PEMSS. Moreover, the results reveal that the on-off hybrid control strategy leads to better performance in comparison with the continuous skyhook control strategy, however, the energy regeneration of the continuous skyhook control strategy is more than that of the on-off hybrid controlstrategy (except for on-off skyhook control strategy).

Investigation of the semi-active electromagnetic damper

Montazeri-Gh, Morteza,Kavianipour, Omid Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.13 No.3

In this paper, the electromagnetic damper (EMD), which is composed of a permanent-magnet rotary DC motor, a ball screw and a nut, is considered to be analyzed as a semi-active damper. The main objective pursued in the paper is to study the two degrees of freedom (DOF) model of the semi-active electromagnetic suspension system (SAEMSS) performance and energy regeneration controlled by on-off and continuous damping control strategies. The nonlinear equations of the SAEMSS must therefore be extracted. The effects of the EMD characteristics on ride comfort, handling performance and road holding for the passive electromagnetic suspension system (PEMSS) are first analyzed and damping control strategies effects on the SAEMSS performance and energy regeneration are investigated next. The results obtained from the simulation show that the SAEMSS provides better performance and more energy regeneration than the PEMSS. Moreover, the results reveal that the on-off hybrid control strategy leads to better performance in comparison with the continuous skyhook control strategy, however, the energy regeneration of the continuous skyhook control strategy is more than that of the on-off hybrid control strategy (except for on-off skyhook control strategy).

Visible light photo-and bioactivity of Ag/TiO_2 nanocomposite with various silver contents

Ali Akbar Ashkarran,Seyed Mahyad Aghigh,Mona kavianipour,Neda Jalali Farahani 한국물리학회 2011 Current Applied Physics Vol.11 No.4

Ag/TiO_2 nanocomposite with various silver contents was synthesized by combination of sol-gel and the novel arc discharge methods in liquid. The Ag/TiO_2 nanoparticles were characterized by X-Ray diffraction (XRD), Brunauer Emmett Teller (BET), transmission electron microscope (TEM) and ultra violet-visible absorption spectroscopy (UV-Vis). The visible light antibacterial activities and photocatalytic properties were successfully demonstrated for the inactivation of Escherichia coli (E-coli) bacteria and Rhodamine B (Rh. B). The results revealed that the Ag/TiO_2 nanoparticles extended the light absorption spectrum toward the visible region and significantly enhanced the inactivation of E-coli bacteria under visible light irradiation. 0.15 gr Ag/TiO_2 nanoparticles revealed best antibacterial activity while 0.05 gr Ag/TiO_2nanoparticles exhibited highest photocatalytic efficiency. The significant enhancement in the photocatalytic activity and antibacterial properties of Ag/TiO_2 nanoparticles under visible light irradiation can be ascribed to the effect of noble metal Ag by acting as electron traps in TiO_2 band gap. A mechanism for photocatalytic degradation of organic pollutants and antibacterial activity over Ag/TiO_2 nanoparticles was proposed based on our observations.