Application of Particle Dampers on a Scaled Wind Turbine Generator to Improve Low-Frequency Vibro-Acoustic Behavior

The purpose of this paper is to introduce a honeycomb damping plate (HCDP) concept based on the particle damping technique to reduce the low-frequency vibration response of wind turbine generators. The HCDP cells contain granular materials and are mounted at different positions on the generator to reduce the transmission of vibrations from stator ring to stator arm. To investigate the efficiency of the HCDP concept in the laboratory, a small-scale replica inspired by the original wind turbine generator is used as reference geometry. The efficiency of the vibration attenuation by using the HCDP concept is experimentally investigated with the help of a laser scanning vibrometer device. In this contribution, the influence of four different granular materials on the vibration attenuation is experimentally investigated. Furthermore, the influence of HCDP positioning on the transmission path damping is analyzed. Apart from this, the effect of single-unit (SU) and multi-unit (MU) HCDP on the frequency response of the generator is also studied. The experimental approach in this paper shows good damping properties of the HCDP concept for reducing the vibration amplitude.

Modal analysis and demonstration of metastructure combining local resonators and an autonomous synchronized switch damping circuit

A locally resonant metastructure is a promising approach for low-frequency vibration attenuation, whereas the attachment of many resonators results in unnecessary and multiple resonance outside the bandgap. To address this issue, we propose a damping metastructure combining local resonators and an autonomous synchronized switch damping circuit. On the basis of modal analysis, we derive an electromechanically coupled equation of the proposed metastructure. The piezo ceramics, which are attached on a small portion of the metastructure and connected to the circuit, remarkably decrease the magnitude of the resonant vibration with no extra sensors, signal processors, or power sources. The displacement at unnecessary resonance was decreased by approximately 75%. The results of the coupled analysis were similar to the experimentally observed results in terms of the location and width of the bandgap on the frequency axis and the decreased displacement for the circuit. The proposed technique can overcome the disadvantage of the metastructure.

A Statically Balanced Compliant Ortho-Planar Mechanism for Low-Frequency Energy Harvesting

The usually high eigenfrequencies of miniaturized oscillators can be significantly lowered by reducing the stiffness through static balancing. In this work, a mechanical design for a statically balanced compliant ortho-planar mechanism is proposed. The mechanism was prototyped using laser micro-machining and subsequently preloaded through packaging. The statically balanced property of the mechanism was experimentally validated by a measurement of the force-deflection relation. A piezoelectric transducer was added and the resulting energy harvesting device was tested at low-frequency vibration of 2Hz. Compared to a reference device, an almost sixfold increase in performance was observed due to the static balancing. Therefore, it was found that the use of static balancing can improve the power output of piezoelectric energy harvesters for low-frequency vibrations.

Textronics spacer knitted material tests as a key element of the diagnostic system that monitors above the proper level of seat vibration

This research is focused on the construction and examination of a prototype of a spacer knitted material with integrated sensors. The combination of textiles with elements of electronics, computer science, and a knowledge of automation is called textronics. This type of material has been proposed as a component of diagnostic systems to monitor the extension level of vibration in employee seats at selected workstations or in children’s chairs. The purpose of the diagnostic system is to improve personal protective equipment (PPE) and increase employee safety. The spacer knitted material was tested with vibration frequencies in the range of 0–40 Hz to develop metrological properties under reproducible and repeatable conditions. The tested spacer knitted material meets the requirements of sensory properties such as vibration. The tested material is characterized by the following metrological parameters: total uncertainty U = 4.5%, sensitivity Sa = 0.64 [V/s2/m] and excitability threshold of 5 Pa with simultaneous high coefficient of low-frequency vibration damping of effective amplitude transmissibility (SEAT) = 2.3. Spacer knitted materials are modern constructs that enable the creation of new hybrid structures that have other properties, e.g., sensory suppression, in addition to spatial form.