This paper describes the new concept of a semi-active tuned mass damper with magnetorheological damper (MR-STMD). The real-time controlled MR damper force emulates controlled damping and a superimposed controllable stiffness force to augment or diminish the force of the passive spring stiffness which enables us to control the MR-STMD natural frequency. Both the damping and natural frequency are tuned according to Den Hartog’s formulae to the actual dominant frequency of the main structure irrespective of whether it is a resonance or a forced frequency. The MR-STMD is experimentally validated on the Empa bridge with a 15.6 m main span for different added masses to shift its resonance frequency 12.2% andC10.4% away from its nominal value. The experimental results are compared to those obtained when the MR-STMD is operated as a passive TMD that is precisely tuned to the nominal bridge. The comparison shows that the MR-STMD outperforms the TMD both in the tuned and all de-tuned cases by up to 63%. Simulations of the MR-STMD concept point out that the proposed semi-active control algorithm is most suitable for MR-STMDs due to the small amount of clipped active forces. A sensitivity analysis demonstrates that the real MR-STMD could be even more powerful if the force tracking errors in the MR damper force due to the current driver and MR fluid dynamics and remanent magnetization effects could be further reduced. The MR-STMD under consideration represents the prototype of the 12 MR-STMDs that have been running on the Volgograd Bridge since late fall 2011. (Some figures may appear in colour only in the online journal)

https://iopscience.iop.org/article/10.1088/0964-1726/21/5/055011/pdf

Frequency and damping adaptation of a TMD with controlled MR damper

This paper presents a new adaptive tuned mass damper (TMD) whose stiffness and damping can be tuned in real-time to changing frequencies of a target structure. The adaptive TMD consists of a tuned mass, a tuned passive spring and a magnetorheological (MR) damper. The MR damper is used to emulate controlled friction?viscous damping and controlled stiffness. The controlled positive or negative stiffness emulated by the MR damper works in parallel to the stiffness of the passive TMD spring. The resulting overall TMD stiffness can therefore be varied around the passive spring stiffness using the MR damper. Both the emulated stiffness and friction?viscous damping in the MR damper are controlled such that the resulting overall TMD stiffness and damping are adjusted according to Den Hartog's formulae. Simulations demonstrate that the adaptive TMD with a controlled MR damper provides the same reduction of steady state vibration amplitudes in the target structure as a passive TMD if the target structure vibrates at the nominal frequency. However, if the target structure vibrates at different frequencies, e.g.?due to changed service loads, the adaptive TMD with a controlled MR damper outperforms the passive TMD by up to several 100% depending on the frequency change.

https://iopscience.iop.org/article/10.1088/0964-1726/20/1/015012/pdf

An adaptive tuned mass damper based on the emulation of positive and negative stiffness with an MR damper

A wound field synchronous machine includes direct oil cooling along a conductive sleeve with elongated semi-arcuate shaped channels which alternate with damper bar channels containing tie-rod supports structures. With a reduction in sleeve thickness permitted by the direct cooling, the overall weight of the machine is reduced.

Rotor cooling system for synchronous machines with conductive sleeve

To achieve strong power coupling, a resonance-type magnetoelectric (ME) transducer with high quality factor is developed to achieve strong ME coupling. The ME transducer employs a type of iron–nickel-based ferromagnetic alloy with constant elasticity and piezoelectric Pb(Zr,Ti)O3 (PZT8) material. The dynamic magnetomechanical behavior of the ferromagnetic alloy is investigated. The result indicates that the strain coefficient of the ferromagnetic alloy at resonance achieves 557.07 nm/A due to the high effective mechanical quality factor of the alloy. The transducer is designed to operate as a half-wavelength, longitudinal resonator. The dynamic performance of the transducer is evaluated by measuring its electrical and vibrational characteristics. The results reveal that (1) the resonance of the transducer occurs at the frequency of 26.9336 kHz with a strain coefficient of 314.74 nm/A, an effective mechanical quality factor of 1600; (2) the ME voltage coefficient achieves 30.07 V/Oe (i.e., 375.875 V/cm Oe) at resonance; (3) the ME output power density at optimal load resistance of 25 kΩ achieves 0.956 mW/cm3 under 0.3 Oe root-mean-square AC magnetic field. The performances indicate that the transducer is promising for ME energy conversion application.

Magnetoelectric transducer with high quality factor for wireless power receiving

Ultrasonic Particle Manipulation

A vibration feeding apparatus comprises a receptacle for holding and conveying components, and first and second linear motors coupled to the receptacle. The first and second linear motors are spaced from each other and have respective coils that are aligned parallel to each other. The first and second linear motors are operative to be driven at a first operation mode whereby to impart rotary vibration to the receptacle, and at a second operation mode whereby to impart linear vibration to the receptacle.

Vibratory feeder for conveying components

A 64-kHz sandwich transducer employing a tube-shaped Terfenol-D/epoxy pseudo 1-3 magnetostrictive composite with 0.61 Terfenol-D volume fraction was developed to alleviate the intrinsic eddy-current losses in magnetostrictive alloy-based transducers. The transducer was designed to operate as a half-wave, longitudinal, mass-spring-mass, linear vibrator. It had a length of 15.7 mm and consisted of a magnetic circuit and a prestress mechanism. The magnetic circuit was composed of the composite tube, a pair of ring-shaped NdFeB permanent magnets, a drive solenoid, and a Ni-based magnetic flux guide. The distributions of the dc magnetic flux lines and magnetic field strength of the transducer were determined using an ANSYS finite-element model. The dynamic performance of the transducer was evaluated by measuring its electrical and vibrational characteristics. The results revealed that the transducer resonates at a frequency of 64.3 kHz with a strain coefficient of 39.2 nm/A, a mechanical quality factor of 39.6, and an effective coupling coefficient of 0.21. Eddy-current losses in the transducer were insignificant in the measured frequency range of 40 Hz-100 kHz. The good transducer performance indicated that Terfenol-D/epoxy pseudo 1-3 composites would be a promising magnetostrictive material for ultrasonic applications.

A 64-kHz sandwich transducer fabricated using pseudo 1-3 magnetostrictive composite

An ultrasonic transducer driver has a giant magnetostrictive element, a fastener for holding the giant magnetostrictive element under mechanical pressure, a first field generator for providing a magnetic bias field, a second field generator for providing a magnetic drive field and a magnetic circuit for channelling the magnetic fields in the magnetostrictive element. An ultrasonic transducer for a bonding apparatus has a horn having a bonding tool at its smaller end and a mounting barrel adjoined onto it. The driver coupled to the larger end of the horn.

/pdf/driver-for-an-ultrasonic-transducer-and-an-ultrasonic-3uw242g60t.pdf

Driver for an ultrasonic transducer and an ultrasonic transducer

The development of a novel piezoelectric induced-strain actuator possessing an innovative internal amplifying structure is presented in this paper. This actuator basically consists of a metal frame and two lead zirconate titanate (PZT) piezoelectric ceramic patches. The metal frame is bent to form an open trapezoid, where its center part has a specially designed saddle-like unit and its slanting legs are attached with PZT patches. The saddle-like unit has an amplifying-lever mechanism at the corners to increase the displacement output of the whole actuator even its legs are mechanically clamped. When an electric field is applied across the thickness of the PZT patches, the patches induce deformations on the whole actuator through the piezoelectric d31 effect. The saddle-like unit can relax the constraints at the joints between the unit and the legs by stretching itself during bending. Piezoelectric finite element analysis is used to maximize the work output of displacement and blocked force of the actuator under different geometric parameters. The results are in good agreement with those obtained from quasi-static measurements, showing that the actuator has work output comparable to and larger than the existing induced-strain actuators (e.g., THUNDER) under fixed mounting conditions. Therefore, the actuator has great potential for use in various practical smart structures and integrated systems, including active-passive vibration isolation and micro-positioning.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Development of a piezoelectric induced-strain actuator with an innovative internal amplifying structure

A novel tunable mass damper (TMD) is developed using the sensitivity of transversal bending stiffness and resonance frequencies of a beam to its axial force. This smart TMD consists of a force actuator-sensor unit suspended in a rigid frame by two flexible beams coupled to the axial ends of the unit and the frame. The force actuator-sensor unit is composed of a giant magnetostrictive composite-based force actuator for producing an axial force to the beams and a pair of piezoelectric ceramic-based force sensors for generating a tuning signal. Through adjusting the magnetic field strength applied to the force actuator to change the axial force exerted on the beams, the transversal bending stiffness of the beams and hence the natural frequency of the smart TMD is tuned. In this paper, the design, fabrication, and characterized of the smart TMD is described. The measured resonance frequency of the smart TMD is 65 Hz at zero magnetic tuning field and 50 Hz at an applied magnetic field of 686 Oe. Tunability of the resonance frequency as high as 23 % is achieved with the reasonably low magnetic tuning field. The frequency response functions as measured using the force sensors agree well with those obtained using a commercial accelerometer, indicating a great possibility of directly deploying the force sensors for active or semi-active tuning or control purposes.

Chung Sheung Yung

Papers

Vibratory feeder for conveying components

A 64-kHz sandwich transducer fabricated using pseudo 1-3 magnetostrictive composite

Driver for an ultrasonic transducer and an ultrasonic transducer

Development of a piezoelectric induced-strain actuator with an innovative internal amplifying structure

A novel tunable mass damper based on giant magnetostrictive composite and piezoelectric ceramic