Multi-mode Vibration Research Articles

Comparison of Formulas Obtained for Analytical and LQ Idea Approaches to Determine the Optimal Actuator Location in Active Multimodal Beam Vibration Reduction

Abstract In this paper an active multimodal beam vibration reduction via one actuator is considered. The optimal actuator distribution is analyzed with two methods: an exact mathematical principles and the LQ problem idea. It turned out that the same mathematical expressions are derived. Thus, these methods are equivalent.

Analysis of hydroelastic slamming through particle image velocimetry

Predicting the hydrodynamic loading experienced by lightweight structures during water impact is central to the design of marine vessels and aircraft. Here, hydroelastic effects of flexible panels during water entry are studied through particle image velocimetry. Experiments are conducted on a compliant wedge entering the water surface in free fall for varying entry velocities, and the pressure field is indirectly evaluated from particle image velocimetry. Results show that the impact is responsible for prominent multimodal vibrations of the wedge, and, vice versa, that the wedge flexibility strongly influences the hydrodynamic loading. With respect to rigid wedges, the hydrodynamic loading exhibits marked spatial variations, which control the location of the minimum and maximum pressure on the wetted surface, and temporal oscillations, which modulate the direction of the hydrodynamic force. These experimental results are expected to aid in refining computational schemes for the analysis of hydroelastic phenomena and provide guidelines for structural design.

Adaptive synchronized switch harvesting: A new piezoelectric energy harvesting scheme for wideband vibrations

This paper proposes a new energy harvesting architecture that optimizes the energy conversion under broadband vibrations, which is called adaptive synchronized switch harvesting (ASSH) technique. This technique is derived from the enhanced synchronized switch harvesting (ESSH) technique and based on a new and effective switch control law, which can prevent the switch in energy transferring circuit from over-frequent on-and-off and accordingly enhance the extracted power under multimode vibration. Compared with the ESSH technique, theoretical and experimental results demonstrate the new technique can improve electromechanical conversion efficiency when the piezoelectric energy harvester is excited under two-mode vibration, especially in the case of higher vibration amplitude of the second mode. The extracted power with the new technique is more than three times the ESSH technique in the case of the exciting signal of amplitude ratio (3:6). Furthermore, a self-powered circuit which implements the technique (ASSH) is proposed, which validates that the new technique can be truly self-powered, thus addressing the issue of harvesting environmental energy by autonomous devices.

Hybrid PD and effective multi-mode positive position feedback control for slewing and vibration suppression of a smart flexible manipulator

A hybrid control strategy for slewing and vibration suppression of a smart flexible manipulator is presented in this paper. It consists of a proportional derivative controller to realize motion control, and an effective multi-mode positive position feedback (EMPPF) controller to suppress the multi-mode vibration. Rather than treat each mode equally as the standard multi-mode PPF, the essence of the EMPPF is that control forces of different modes are applied according to the mode parameters of the respective modes, so the vibration modes with less vibration energy receive fewer control forces. Stability conditions for the close loop system are established through stability analysis. Optimal parameters of the EMPPF controller are obtained using the method of root locus analysis. The performance of the proposed strategy is demonstrated by simulation and experiments. Experimental results show that the first two vibration modes of the manipulator are effectively suppressed. The setting time of the setup descends approximately 55%, reaching 3.12 s from 5.67 s.

Influence of low-spatial frequency ripples in machined potassium dihydrogen phosphate crystal surfaces on wavefront errors based on the wavelet method

In using a fly cutter to machine potassium dihydrogen phosphate (KDP) crystals, rippling in machined surfaces will remain that will have a significant impact on the optical performance. An analysis of these low-spatial frequency ripples is presented and its influence on the root-mean-squared gradient (GRMS) of the wavefront discussed. A frequency analysis of the machined KDP crystal surfaces is performed using wavelet transform and power spectral density methods. Based on a classification of the time frequencies for these macroripples, the multimode vibration of the machine tool is found to be the main reason surface ripples are produced. Improvements in the machine design parameters are proposed to limit such effects on the wavefront performance of the KDP crystal.

Two-Stage Wideband Energy Harvester Driven by Multimode Coupled Vibration

This study develops a piezoelectric vibratory energy harvester intended for wideband operation at low frequencies. The harvester features a two-stage vibratory structure. The first stage picks up ambient low-frequency vibration and excites the second stage to vibrate at its resonant frequency, thereby realizing frequency upconversion and improving power-generation capability. The first stage is designed as a multimode resonator to adapt to a wide frequency band by multimode vibration coupling. Finite element simulation and lumped-element modeling indicate that the multimode coupled vibration at the first stage can excite the second stage into wideband resonance that well adapts the electric power generation to the wideband ambient vibrations. The micro harvesters are fabricated, with the testing results validating the design concept. The harvester can operate under acceleration amplitude of 1 g and frequency from 10 to 30 Hz. A peak power of 24.56 μW and a maximum average power of 3.62 μW are achieved at 1 g and 20 Hz. The harvester also exhibits power generating capability under excitation of the vibration from a running bus, where a peak power of 6.89 μW is generated.

Adaptive positive position feedback for multi-modal vibration control of a flexible beam

The multi-modal vibration control of flexible structures is recognised as a significant challenge owing to the well-known phenomenon of spillover and frequency varying. Spillover phenomenon and variation in the modal dynamics may cause instability and degradation in performance. To overcome these defects, an adaptive positive position feedback (PPF) method is proposed for controlling the vibration of a flexible beam with bonded piezoelectric sensors and actuators. Finite element method is used for dynamic modelling of an experimental flexible beam. An online adaptive parameter estimator based on the gradient algorithm with parameter projection and a dead zone is presented to identify the modal frequencies in the presence of disturbances. Multi-modal PPF controller is adjusted with estimated frequencies and is able to damp the target modes quickly. Simulation results show that modal frequencies are estimated quite accurately and the vibration of the structure is significantly suppressed.

1512 多モード振動制御を目的としたセンサ・アクチュエータ最適配置方法に関する一検討(OS3-3 設計と最適化III,OS3 設計と最適化)

1512 多モード振動制御を目的としたセンサ・アクチュエータ最適配置方法に関する一検討(OS3-3 設計と最適化III,OS3 設計と最適化)

<b>Reduction of Carbody Flexural Vibration by the High-damping Elastic Support of Under-floor Equipment</b>

This paper presents a method for reducing flexural vibrations in a railway vehicle carbody by supporting under-floor equipment using high-damping elastic mounts. This is a kind of dynamic vibration absorber utilizing under-floor equipment as a mass element which has been introduced based on the inspiration of the damping effect of passengers. A series of excitation tests were conducted in the rolling stock testing plant using a Shinkansen type test vehicle by applying the proposed method. As a result of the tests, good vibration reduction performance, including multi-modal vibration reduction and vibration isolation from the equipment, was observed.

Piezoelectric Multimode Vibration Control for Stiffened Plate Using ADRC-Based Acceleration Compensation

Considering the variety of uncertainties and disturbances in real active vibration control systems, a novel piezoelectric multimode control strategy for an all-clamped stiffened plate (ACSP) structure is proposed in this paper. First, an active disturbance rejection control (ADRC) method, i.e., the extended state observer (ESO)-based vibration control scheme, is employed to ensure the performance of the vibration suppression and rejection of the lumped disturbances of the closed-loop system. Second, a proportional differential controller and an acceleration feedforward controller produce the control law for each vibration mode. Moreover, a chaos optimization method based on a logistic map is introduced to automatically tune the parameters of the feedback channel. The stability and superiority of the proposed controller are theoretically analyzed. Compared with the classical ADRC method, the multimode vibration experimental results demonstrate that the control performance of the first mode is improved from 12.04 to 14.06 dB; meanwhile, the performance of the second mode is also improved, having changed from 11.1 to 13.68 dB.

Fuzzy neural network multi-modal vibration control of thin cylindrical shells laminated with photostrictive actuators

In this paper, the multi-modal vibration control of a simply supported thin cylindrical shell laminated with photostric- tive actuators is studied. First, the photo-electric/shell coupling equations of a cylindrical shell laminated with the multi-layer actuator configuration are presented. Moreover, in view of the nonlinear and time-variant characteristics of photostrictive actu- ators, a fuzzy neural network (FNN) controller with adaptive learning rates is developed to attenuate multi-mode vibration of photo-electric laminated thin cylindrical shells. This approach has learning ability for responding to the time-varying charac- teristic of the multi-mode vibration induced by disturbance. Its control rule bank can be established and modified continuously by on-line learning. Finally, numerical simulation results are provided to show that the proposed intelligent controller could effectively suppress multi-mode vibration of photo-electric laminated thin cylindrical shells.

Semi-active vibration control of an aircraft panel using synchronized switch damping method

Withthe rapid development of the aerospace industry, the control of aircraft structural vibration becomes increasingly important. Semi-active vibration control method based on synchronized switch damping have been attracted more attention due to its robustness compared with passive approaches and simplicity compared with active approaches. In this paper, three SSD semi-active control methods combined with a modal observer were applied to multimodal vibration suppression of an aircraft panel with stiffeners, and their effectiveness was verified by experimental results. A state observer was built based on the experimentally identified state-space model of the panel. Modal displacement of the panel was identified on line using the state observer and used in switch control of different piezoelectric actuators. Since the vibration characteristics of the panel with stiffeners was very complicated and its natural frequencies were distributed densely, use of the identified modal displacement as the reference signal for voltage switching in SSDI, SSDV and SSDNC improved the control effect for some specific modes and simplified the system. Good performances of vibration suppression were achieved in both single-mode control and multimodal control.

Structural multimode vibration absorbing with electromagnetic shunt damping

This paper presents multimode vibration absorbing methods which employ negative resistance (NR) and negative inductance negative resistance (NINR) electromagnetic shunt damping vibration absorbers. The NR and NINR shunts can change the impedance of an electromagnet so as to change the control force of the absorber. The governing equation of the coupling system is established. What is more, some numerical simulations are carried out and the results show that the absorbers with NR or NINR shunt can effectively suppress the multimode vibration. Furthermore, the root locus is analyzed to design the resistance of a shunt.

Multi-mode electro-mechanical vibrations of a microtubule: In silico demonstration of electric pulse moving along a microtubule

Microtubules are known to be involved in intracellular signaling. Here, we show in silico that electrically polar collective vibration modes of microtubules form electric oscillating potential which is quasi-periodic both in space and in time. While single mode microtubule vibration excites an electric field with spatially stationary local minima and maxima of the electric field, the multimode excitation causes the formation of an electric pulse and many transient local electric field minima. The biophysical mechanism we describe lends support to the view that microtubules may comprise a substrate for ultra-fast electrical signaling in neurons or other living cells.

Multi-modal vibration energy harvesting utilizing spiral cantilever with magnetic coupling

Most vibration energy harvesters use conventional cantilever configuration and typically perform well for a specific frequency at the first resonant mode, this makes the devices less effective in ambient vibrations with varying frequencies. This paper presents a multi-modal vibration energy harvester achieving multiple peaks in the frequency response and causing the possibility of widening the operation frequency range. A spiral-shaped cantilever with tip mass in the form of magnets coupling with a magnetoelectric (ME) transducer is adopted in this harvester. The spiral-shaped beam is shown to be conductive to presenting multi-modal responses and lowering the natural frequencies of the harvester. Furthermore, due to the magnetic coupling between the magnets and the transducer, the peak frequencies are tunable and the frequency spacing between the adjacent modes can be obviously reduced. The operating principle of energy conversion is based on the relative movement of the magnets and the transducer, and the effects of magnetic coupling working on the peak frequencies are experimentally determined. The experimental results indicate that the proposed harvester can obtain five obvious peak values in the range of 15–70Hz, which are concentrated around 20.7, 26.1, 32.3, 42.2 and 63.7Hz, respectively.

2A24 Comprehensive assessment of smart energy-harvesting from multimodal vibrations(The 12th International Conference on Motion and Vibration Control)

2A24 Comprehensive assessment of smart energy-harvesting from multimodal vibrations(The 12th International Conference on Motion and Vibration Control)

Development of Active Mass Dampers for Reducing Multi-modal Flexural Vibrations of Carbody

The vertical flexural vibrations of railway vehicle carbodies are needed to be reduced from the viewpoint of ride quality. In particular, plural flexural vibration modes - having natural frequencies around 10Hz - are known to have a major impact on ride quality. To reduce these flexural vibrations, this paper proposes a vibration control method using active mass dampers (AMDs). The feasibility of this method was verified by carrying out excitation tests using a test vehicle with existing actuators at the rolling stock testing plant at RTRI. Following this, a more practical AMD system was designed based on numerical analysis and an actual AMD system with two smaller and lighter actuators was developed. The effectiveness of the vibration control using the newly developed AMD system was confirmed by means of excitation tests using an actual vehicle.

硅基半导体芯片激光红外显微成像系统研究

The visible micro-imaging technology cannot observe the chip internal structure.In order to sovle this issue,a silicon-based semiconductor chip laser infrared microscopy imaging system was designed.The characteristic of 1 064nm wavelength of infrared laser that has a certain penetration depth for silicon material was applied for the design.A microscope objective with numerical aperture of 0.42 was adopted in this system.The multimode silica fiber vibration method was used to eliminate the speckle noise.The track pitch of CD-RW disk image was observed by microscope infrared imaging.The results showed that the system resolution can reach 1.6μm and close to the theoretical value.So it can achieve internal structure observation of static RAM of which the thickness of the chip is 70μm.

Active Vibration Suppression of a 3-DOF Flexible Parallel Manipulator Using Efficient Modal Control

This paper addresses the dynamic modeling and efficient modal control of a planar parallel manipulator (PPM) with three flexible linkages actuated by linear ultrasonic motors (LUSM). To achieve active vibration control, multiple lead zirconate titanate (PZT) transducers are mounted on the flexible links as vibration sensors and actuators. Based on Lagrange’s equations, the dynamic model of the flexible links is derived with the dynamics of PZT actuators incorporated. Using the assumed mode method (AMM), the elastic motion of the flexible links are discretized under the assumptions of pinned-free boundary conditions, and the assumed mode shapes are validated through experimental modal test. Efficient modal control (EMC), in which the feedback forces in different modes are determined according to the vibration amplitude or energy of their own, is employed to control the PZT actuators to realize active vibration suppression. Modal filters are developed to extract the modal displacements and velocities from the vibration sensors. Numerical simulation and vibration control experiments are conducted to verify the proposed dynamic model and controller. The results show that the EMC method has the capability of suppressing multimode vibration simultaneously, and both the structural and residual vibrations of the flexible links are effectively suppressed using EMC approach.

Optimal Placement of Piezoelectric Plates to Control Multimode Vibrations of a Beam

Damping of vibrations is often required to improve both the performance and the integrity of engineering structures, for example, gas turbine blades. In this paper, we explore the possibility of using piezoelectric plates to control the multimode vibrations of a cantilever beam. To develop an effective control strategy and optimize the placement of the active piezoelectric elements in terms of vibrations amplitude reduction, a procedure has been developed and a new analytical solution has been proposed. The results obtained have been corroborated by comparison with the results from a multiphysics finite elements package (COMSOL), results available in the literature, and experimental investigations carried out by the authors.