Magnetic Damping System Research Articles

Flow-Induced Motion and Energy Conversion of the Cir-T-Att Oscillator in a Flow Field with a High Reynolds Number

The present study aims to systematically investigate the effects of a high Reynolds number on the flow-induced motion and energy conversion of the Cir-T-Att oscillator. Experiments are conducted in six Reynolds number ranges (2.89 × 104~6.51 × 104 < Re < 7.71 × 104~15.21 × 104) in regimes of TrSL2, TrSL3 and TrBL0. The system total damping ratio (ζtotal) is adjusted by varying excitation voltages (VB) with a controllable magnetic damping system. The VB is varied from 0 V to 165 V, corresponding to 0.082 ≤ ζtotal ≤ 1.153. The amplitude, frequency, fluid force, spectral content, active power, and upper limit of power output are analyzed. The results show that the Reynolds number affects both amplitude and global response characteristics. The active power increases with an increasing Reynolds number within the upper branch. The maximum power output of the Cir-T-Att oscillator reaches 10.43 W, appearing at Re = 14.67 × 104 (D = 0.16 m, ζtotal = 0.468, Ur = 6.34), while the maximum upper limit of power output is 17.80 W at Re = 15.21 × 104 (D = 0.16 m, ζtotal = 0.678, Ur = 6.57).

Hydrokinetic energy harvesting from flow-induced motion of oscillators with different combined sections

Flow-Induced Motion (FIM) of elastically-supported oscillators with "circle-polygon-attachments"sections are experimentally investigated in a water channel to examine the effects of combined sections on hydrokinetic energy harnessing. The incoming flow velocity considered is U = 0.55 – 1.35 m/s, corresponding to reduced velocity Ur = 5.3 –13. A controllable magnetic damping system is applied to change the total damping ratio (ζtotal) of the flow-induced motion energy conversion system (FIMECS) by varying excitation voltages VB (VB = 0 – 108 V, ζtotal = 0.037 – 0.398). Particularly, to calculate fluid force with experimental results, a torque sensor is introduced into FIMECS. The amplitude, frequency, fluid force, active power and efficiency are analyzed. Results suggest that an oscillator with symmetric sharp attachments and no vortex reattachment is conducive to galloping with self-excitation under large damping, and the circle-T-attachments oscillator is optimum. Its best branch for energy conversion is the galloping branch, the peak of active power is Pharn is 19.28 W and the peak of efficiency is ηharn is 26.22% (VB = 99 V, Ur = 11.28). Under the same condition, the circular-T-attachments oscillator has a better energy conversion capacity than the existing ones (triangular prism).

Energy harvesting from and vibration response of different diameter cylinders

Energy harvesting from flow-induced vibrations (FIV) of an elastically-supported cylinder (diameter D) immersed in the wake of another cylinder with diameter d is systematically investigated. The diameter ratio of the two cylinders is d/D = 0.4. The incoming flow velocity considered is U∞ = 1.54–9.0 m/s, corresponding to Reynolds number Re = 3.3 × 103 to 1.95 × 104. A controllable magnetic damping system that can add harnessing damping ratio ξ is used to convert wind to electrical energy. The ξ is varied from 0.00091 to 0.00249. The cylinder spacing ratio L/d is varied from 1.0 to 4.0, where L is the distance from the upstream cylinder center to the forward stagnation point of the downstream cylinder. The vibration responses comprise combined vortex-induced vibration (VIV) and galloping vibration for small ξ and separated VIV and galloping for high ξ. The galloping offers harnessed power P three times larger than the VIV. The maximum efficiency η is 11.2–14.6% in the VIV regime but is only 1–2% and almost independent of reduced velocity Ur and ξ in the galloping regime.

Analysis and Synthesis of Motion of Aerodynamically Stabilized Nanosatellites of the CubeSat Design

The motion of aerodynamically stabilized nanosatellites of the CubeSat design is studied. The features of the nanosatellites behavior in low orbits are conditioned both by the atmospheric effects and their own mass and inertial characteristics: the lifetime of nanosatellites is shorter, while the angular acceleration generated by the aerodynamic moment is much higher as compared with big satellites having large mass. CubeSats may experience resonance modes of motion caused by the shape factor of a rectangular parallelepiped. In addition, the existing commercial CubeSat deployers often generate large initial angular velocities that are random in nature. The conditions that cause the specific features of the CubeSat motion are considered and analyzed. A probabilistic approach to choosing their mass and inertial characteristics is proposed. The problems of motion stabilization are studied, and recommendations are formulated on the design of aerodynamically stabilized CubeSats with a passive/active magnetic damping system.

Optimal geometry and materials for nanospacecraft magnetic damping systems

A magnetic damping system for nanospacecraft attitude stabilization is proposed, based on the use of thin strips of amorphous Fe-B-Si soft magnetic ribbons. The size, number, and location of the strips is optimized, and a predictive formulation is provided. The main result of ground tests, comparing the performance of several soft magnetic materials, is that suitably heat-treated amorphous ribbons provide the best loss performance in the whole range of magnetic fields expected in orbit.

An integrated passive magnetic damping system for high-speed compressor with flexible rotor

To provide a more reliable rotor damping system for high-speed compressor with flexible rotor, a passive magnetic damping integrated with an active axial bearing (PMDAB) system is proposed. The PMDAB system can provide active force in axial direction and also can provide damping force without control system in radial direction. To enhance the damping ability of the system, an analytical model is set up especially for the high-speed vibration rotor, and the relation between resistance of radial coils and the provided damping force is discussed for the first time. The coupling characteristic between passive radial damping coefficient and active axial bearing stiffness is also analyzed; the result shows that the coupling is too small, therefore can be neglected. Finally, a design example for a high-speed compressor is given based on electromagnetic analysis of PMDAB and dynamic analysis of the flexible rotor. The analytical and design results, which are verified by the finite element method result, show that the PMDAB is effective in controlling the first bending vibration of flexible rotor.

Active vibration control of a suspension system using an electromagnetic damper

This paper is concerned with the design and implementation of a magnetic damper system to reduce the vibration of a suspension system actively. A cylindrical-type electromagnetic actuator with a permanent magnet is analysed and an effective controller design is made. An accurate force analysis is carried out for the given system. An accurate transfer function for the total system is determined by experimental data using an error minimization method. For experiments, a simple suspension structure system is utilized, in which a magnetic damper composed of a permanent magnet and digital controller is attached. In order to drive the system, a bipolar power amplifier of the voltage control type is utilized. A stable and high speed control board is used to implement digital control logic for the given system. This paper shows that the magnetic damper system using a phase lead controller is excellent in reducing the vibration of a one-degree-of-freedom suspension system.

A Study of Rotor Vibration Reduction using Fuzzy Magnetic Damper System

This paper concerns rotor vibration reduction using magnetic damper system. The fuzzy control logic is utilized to fulfill desired motion. The fuzzy system structure and membership function were first determined by simulation results. The researched control logic contains two fuzzy controller : reference position variation according to the rotor whirling status and error compensation algorithm to minimize the rotor vibration due to unbalance and unstable fluid film force. The Sugeno type output membership function was utilized by several trials and optimized membership function constants were selected from experiments. The experimental results show that the proposed method effectively control and reduce the rotor vibration with fluid film bearings.

Dynamic finite element analysis of a magnetic damper system

In this paper, in order to develop a new magnetic damper element, we have analyzed the simplified model by using the axisymmetric finite element method. Moreover, the dynamic simulations under shifting disturbances were carried out by using the step-by-step method. And we carried out an experiment on an actual model using a displacement sensor. The experimental results were compared with the calculated result.