A Modified Iterative Learning Control Approach for the Active Suppression of Rotor Vibration Induced by Coupled Unbalance and Misalignment

This paper proposes a modified iterative learning control(MILC)periodical feedback-feedforward algorithm to reduce the vibration of a rotor caused by coupled unbalance and parallel misalignment.The control of the vibration of the rotor is provided by an active magnetic actuator(AMA).The iterative gain of the MILC algorithm here presented has a self-adjustment based on the magnitude of the vibration.Notch filters are adopted to extract the synchronous(1×Ω)and twice rotational frequency(2×Ω)components of the rotor vibration.Both the notch frequency of the filter and the size of feedforward storage used during the experiment have a real-time adaptation to the rotational speed.The method proposed in this work can provide effective suppression of the vibration of the rotor in case of sudden changes or fluctuations of the rotor speed.Simulations and experiments using the MILC algorithm proposed here are carried out and give evidence to the feasibility and robustness of the technique proposed.

Wind-Vortex-Induced Vibrations of a Deepwater Jacket Pipe and Vibration Suppression Using a Nonlinear Energy Sink

The purpose of this study is to investigate the suppression effect of a nonlinear energy sink(NES)on the wind-vortex-induced pipe vibration and explore the influence of damping,stiffness,and NES installation position on the suppression effect.In this work,the wind-vortex-induced vibration of an elastic pipe of a deepwater jacket was studied,and vibrations were suppressed by using an NES.A van der Pol wake oscillator was used to simulate vortex-induced force,and the dynamic equation of the pipe considering the NES was established.The Galerkin method was applied to discretize the motion equation,and the vortex-induced vibration(VIV)of the pipe at reduced wind speeds was numerically analyzed.The novelty of this research is that particle swarm optimization was used to optimize the parameters of the NES to improve vibration suppression.The influence of the installation position,nonlinear stiffness,and damping parameters of the NES on vibration suppression was analyzed.Results showed that the optimized parameter combinations of the NES can effectively reduce wind-vortex-induced pipe vibration.The installation position of the NES had a significant effect on vibration suppression,and the midpoint of the pipe was the optimal NES installation position.An increase in stiffness or a 10% decrease in damping may cause vibration suppression failure.The results of this study provide some guidance for VIV suppression in deepwater jacket pipes.

Vibration Suppression for Active Magnetic Bearings Using Adaptive Filter with Iterative Search Algorithm

Active Magnetic Bearing(AMB) is a kind of electromagnetic support that makes the rotor movement frictionless and can suppress rotor vibration by controlling the magnetic force. The most common approach to restrain the rotor vibration in AMBs is to adopt a notch filter or adaptive filter in the AMB controller. However, these methods cannot obtain the precise amplitude and phase of the compensation current. Thus, they are not so effective in terms of suppressing the vibrations of the fundamental and other harmonic orders over the whole speed range. To improve the vibration suppression performance of AMBs,an adaptive filter based on Least Mean Square(LMS) is applied to extract the vibration signals from the rotor displacement signal. An Iterative Search Algorithm(ISA) is proposed in this paper to obtain the corresponding relationship between the compensation current and vibration signals. The ISA is responsible for searching the compensating amplitude and shifting phase online for the LMS filter, enabling the AMB controller to generate the corresponding compensation force for vibration suppression. The results of ISA are recorded to suppress vibration using the Look-Up Table(LUT) in variable speed range. Comprehensive simulations and experimental validations are carried out in fixed and variable speed range, and the results demonstrate that by employing the ISA, vibrations of the fundamental and other harmonic orders are suppressed effectively.

Experimental study of suppressing the unbalanced response vibration of rotor system with a G-type integral squeeze film damper

Conventional squeeze film dampers have numerous challenges including lock up,bistable response and incoordinate precession.In order to resolve these nonlinear problems,a novel G-type integral squeeze film damper(GISFD)is proposed in this research.The experimental test rig is provided to investigate the rotor system with an unbalanced single disk.Numerical simulation results show that the structural design of GISFD is reasonable,which can ensure its safe and stable operation.The influence of different support stiffnesses on the first-order speed of the rotor system is analyzed.Experimental results show that GISFD can effectively suppress the unbalanced response vibration of the rotor.In a certain range,it is found that the suppression effect of GISFD increases with the increase in the kinematic viscosity of the damping fluid.When the silicone oil with kinematic viscosity coefficients v=30.0 cm^(2)/s is employed,the vibration reduction of GISFD is approximately 71.51%.Furthermore,the experimental results show that with the increase of the unbalance,there is a linear relationship between the unbalance and the corresponding amplitude of the unbalanced response.It is concluded that GISFD has excellent linear damping characteristics and reduces the sensitivity of the rotor system to the unbalanced mass.

Effects of time-delayed vibration absorber on bandwidth of beam for low broadband vibration suppression

The effects of time-delayed vibration absorber(TDVA) on the dynamic characteristics of a flexible beam are investigated. First, the vibration suppression effect of a single TDVA on a continuous beam is studied. The first optimization criterion is given,and the results show that the introduction of time-delayed feedback control(TDFC) is beneficial to improving the vibration suppression at the anti-resonance band. When a single TDVA is used, the anti-resonance is located at a specific frequency by the optimum design of TDFC parameters. Then, in order to obtain low-frequency and broad bands for vibration suppression, multiple TDVAs are uniformly distributed on a continuous beam,and the relationship between the dynamic responses and the TDFC parameters is investigated. The obtained relationship shows that the TDVA has a significant regulatory effect on the vibration behavior of the continuous beam. The effects of the number of TDVAs and the nonlinearity on the bandgap variation are discussed. As the multiple TDVAs are applied, according to the different requirements on the location and bandwidth of the effective vibration suppression band, the optimization criteria for the TDFC parameters are given, which provides guidance for the applications of TDVAs in practical projects such as bridge and aerospace.

Enhanced vibration suppression and energy harvesting in fluid-conveying pipes

A novel vibration absorber is designed to suppress vibrations in fluidconveying pipes subject to varying fluid speeds.The proposed absorber combines the fundamental principles of nonlinear energy sinks(NESs)and nonlinear energy harvesters(NEHs).The governing equation is derived,and a second-order discrete system is used to assess the performance of the developed device.The results demonstrate that the proposed absorber achieves significantly enhanced energy dissipation efficiency,reaching up to 95%,over a wider frequency range.Additionally,it successfully harvests additional electric energy.This research establishes a promising avenue for the development of new nonlinear devices aimed at suppressing fluid-conveying pipe vibrations across a broad frequency spectrum.

Adaptive PI Control Strategy for Flat Permanent Magnet Linear Synchronous Motor Vibration Suppression

Due to low damping ratio, fiat permanent magnet linear synchronous motor＇s vibration is difficult to be damped and the accuracy is limited. The vibration suppressing results are not good enough in the existing research because only the longitudinal direction vibration is considered while the normal direction vibration is neglected. The parameters of the direct-axis current controller are set to be the same as those of the quadrature-axis current controller commonly. This causes contradiction between signal noise and response. To suppress the vibration, the electromagnetic force model of the flat permanent magnet synchronous linear motor is formulated first. Through the analysis of the effect that direct-axis current noise and quadrature-axis current noise have on both direction vibration, it can be declared that the conclusion that longitudinal direction vibration is only related to the quadrature-axis current noise while the normal direction vibration is related to both the quadrature-axis current noise and direct-axis current noise. Then, the simulation test on current loop with a low-pass filter is conducted and the results show that the low-pass filter can not suppress the vibration but makes the vibration more severe. So a vibration suppressing strategy that the proportional gain of direct-axis current controller adapted according to quadrature-axis reference current is proposed. This control strategy can suppress motor vibration by suppressing direct-axis current noise. The experiments results about the effect of Kp and Ti on normal direction vibration, longitudinal vibration and the position step response show that this strategy suppresses vibration effectively while the motor＇s motion performance is not affected. The maximum reduction of vibration can be up to 40%. In addition, current test under rated load condition is also conducted and the results show that the control strategy can avoid the conflict between the direct-axis current and the quadrature-axis current under typical load. Adaptive PI control strategy can effectively suppress the flat permanent magnet linear synchronous motor＇s vibration without affecting the motor＇s performance.

Multi-resonator coupled metamaterials for broadband vibration suppression

In this study,multi-resonator coupled metamaterials(MRCMs)with local resonators are proposed to obtain the multiple and wide band gaps.Kinetic models of the MRCMs are established,and the boundary conditions of the unit cell are obtained with Bloch's theorem.The effects of structural parameters,including the mass of the resonator and the spring stiffness,on the distributions of the band gaps are studied.Furthermore,the frequency domain responses and the time domain responses are calculated for analyzing the structural vibration characteristics and the effects of damping on structural vibration.The results show that the frequency domain response can accurately express the distributions of the band gaps of the MRCMs,and we can increase the number and the width of the band gaps by using the MRCMs for the superior vibration suppression capability.

Experimental study on vibration suppression in a rotor system under base excitation using an integral squeeze film damper

Base excitation is one of common excitations in rotor system.In order to study the dynamic characteristics of rotor systems under base excitation and the effect of integral squeeze film dampers(ISFDs)on their dynamic characteristics,a single-disk rotor test rig,where mass imbalance and base excitation could be applied,is developed.Experimental research on the rotor system response under sinusoidal base excitation conditions with different frequencies and excitation forces is performed and the effect of ISFD on the dynamic characteristics of the rotor is investigated.The experimental results demonstrate that when the sinusoidal base excitation frequency approaches the first critical speed of the rotor system or the natural frequency of the rotor system base,strong vibration occurs in the rotor,indicating that the base excitation of the two frequencies has a greater impact on rotor system response.In addition,with the increase of the base excitation force,the vibration of the rotor will be increased.ISFDs can significantly inhibit the vibration due to unbalanced forces and sinusoidal base excitation in rotor systems.To a certain extent,ISFDs can improve the effect of sinusoidal base excitation with most frequencies on rotor system response,and they have a good vibration reduction effect for sinusoidal base excitation with different excitation forces.

Synchronous Vibration Suppression of Magnetic Bearing Systems without Angular Sensors

Active Magnetic Bearing(AMB)levitates rotor by magnetic force without friction,and it can provide active control force to suppress vibration while rotating.Most of vibration suppressing methods need angular speed sensors to obtain rotating speed,but in many occasions,angular speed sensor is difficult to install or is difficult to guarantee reliability.This paper proposed a vibration suppressing strategy without angular speed sensor based on generalized integrator and frequency locked loop(GI-FLL)and phase shift generalized integrator(PSGI).GI-FLL and high-pass filter estimate frequency from control current,PSGI is applied to generate compensating signal.Firstly,model of AMB system expressed by transfer function is established and effect of centrifugal force is analyzed.Then,principle and process of vibration suppressing strategy is introduced.Influence of parameters are analyzed by root locus and bode diagram.Simulation results display the process of frequency estimation and performance of displacement.Experiments are carried on a test rig,results of simulations and experiments demonstrate the effectiveness of proposed vibration suppressing strategy.

Finite-time tracking control and vibration suppression based on the concept of virtual control force for flexible two-link space robot

The dynamic modeling, finite-time trajectory tracking control and vibration suppression of a flexible two-link space robot are studied. Firstly, the dynamic model of the system is established by combining Lagrange method with assumed mode method. In order to ensure that the base attitude and the joints of space robot can reach the desired positions within a limited time, a non-singular fast terminal sliding mode(NFTSM) controller is designed, which realizes the finite-time convergence of the trajectory tracking errors. Subsequently, for the sake of suppressing the vibrations of flexible links, a hybrid trajectory based on the concept of the virtual control force is developed, which can reflect the flexible modes and the trajectory tracking errors simultaneously. By modifying the original control scheme, a NFTSM hybrid controller is proposed. The hybrid control scheme can not only realized attitude stabilization and trajectory tracking of joints in finite time, but also provide a new method of vibration suppression. The simulation results verify the effectiveness of the designed hybrid control strategy.

Experimental Investigation of Disturbing the Flow Field on the Vortex-Induced Vibration of Deepwater Riser Fitted with Gas Jetting Active Vibration Suppression Device

An experimental investigation on the disturbance effect of jet-type active vibration suppression device on vortexinduced vibration of deep-sea riser was carried out in the wave-flow combined flume.The vibration suppression device was designed in which the jet pipe was horizontally fixed to the front end of the riser.By varying three different excitation spacings and multi-stage outflow velocities,the influence law of the dominant frequency,dimensionless displacement and other dynamic response parameters was studied under different excitation spacings,and the mechanism and sensitive characteristics of the disturbance suppression were explored.The results indicate that the variation of excitation spacing makes gas curtain enter the strong disturbed flow region at different velocities and angles,and the coupling relationship between excitation spacing and reduced velocity is the key factor to enter the strong disturbed flow region to achieve the optimal disturbance suppression.In the strong disturbed flow region,the influence of gas curtain on the dominant frequency is obviously affected by the flow velocity,while the vibration displacement is stable at the same amplitude and is weakly affected by the flow velocity.Gas curtain can effectively disturb the formation of vortex shedding,destroy the strong nonlinear coupled vibration of the riser,and achieve better vibration suppression effect.In the weak disturbed flow region,the vortex length of the riser tail is prolonged,the strong nonlinear coupled vibration of the riser is gradually restored,and the vibration suppression effect of the device gradually decreases.

Vibration suppression of magnetostrictive laminated beams resting on viscoelastic foundation

The vibration suppression analysis of a simply-supported laminated composite beam with magnetostrictive layers resting on visco-Pasternak’s foundation is presented.The constant gain distributed controller of the velocity feedback is utilized for the purpose of vibration damping.The formulation of displacement field is proposed according to Euler-Bernoulli’s classical beam theory(ECBT),Timoshenko’s first-order beam theory(TFBT),Reddy’s third-order shear deformation beam theory,and the simple sinusoidal shear deformation beam theory.Hamilton’s principle is utilized to give the equations of motion and then to describe the vibration of the current beam.Based on Navier’s approach,the solution of the dynamic system is obtained.The effects of the material properties,the modes,the thickness ratios,the lamination schemes,the magnitudes of the feedback coefficient,the position of magnetostrictive layers at the structure,and the foundation modules are extensively studied and discussed.

Research on Vibration Suppression of the Finite Plate with Square Steel Beams Using Traveling Wave Method

The vibration suppression of the finite plate with square steel beams is studied using traveling wave method. The finite plate with square beams is modeled as the coupling systems between the plate flexural motion and the flexural and torsional motions for the square beams. The vibration response at any position of the coupling structure can be obtained by wave method. Numerical results show that comparing to finite element method (FEM), not only the low frequency but also the medium-high frequency vibration response of the finite plate with square beam can be effectively calculated by wave method. The suppression effect can be increased as the square beam is located at one-third of the length of plate or increasing the height of the beam. The study provides reference for arranged square beams applying to vibration suppression of ship and train structures.

ACTIVE VIBRATION CONTROL AND SUPPRESSION FOR INTEGRATED STRUCTURES

The finite element dynamic model for integrated structures containing distributed piezoelectric sensors and actuators ( S/As ) is formulated with a new piezoelectric plate bending element in this paper. The problem of active vibration control and suppression of integrated structures is investigated under constant gain negative velocity feedback control law. A general method for active vibration control and suppression of integrated structures is presented. Finally, numerical example is given to illustrate the validity of the method proposed in this paper.

Vibration Absorption Efficiency and Higher Branches Elimination of Variable-Stiffness Nonlinear Energy Sink

Vibration absorption efficiency of a variable⁃stiffness nonlinear energy sink(NES)was investigated when the main oscillator was subjected to harmonic and impulse excitations.The slow flow equations of the coupled system were derived by using the complexification⁃averaging method,and the nonlinear equations which describe the steady⁃state response were obtained.As the harmonic excitation force increased,the system which comprises constant⁃stiffness NES generated higher branch responses,greatly reducing the vibration absorption efficiency.The influence of nonlinear stiffness on the responses of the system was investigated.Results show that,with the increase of harmonic exciting force,a reduction of NES stiffness can eliminate the higher branch responses and even the frequency band of strongly modulated responses.The vibration absorption efficiency of variable⁃stiffness NES attached to the linear oscillator for different amplitudes of impulse excitation was investigated.Results show that the proper reduction of nonlinear stiffness under increasing impulse excitation can greatly increase the vibration absorption efficiency of NES,and the variable⁃stiffness design can effectively mitigate the negative influences of the increase of the excitation amplitude on the efficiency of constant⁃stiffness NES.

Hybrid vibration isolation optimization of a flexible manipulator based on neural network agent model

Segmented Active Constrained Layer Damping(SACLD)is an intelligent vibration-damping structure,which could be applied to the sectors of aviation,aerospace,and transportation engineering to reduce the vibration of flexible structures.Moreover,machine learning technology is widely used in the engineering field because of its efficient multi-objective optimization.The dynamic simulation of a rotational segmental flexible manipulator system is presented,in which enhanced active constrained layer damping is carried out,and the neural network model of Genetic Algorithm-Back Propagation(GA-BP)algorithm is investigated.Vibration suppression and structural optimization of the SACLD manipulator model are studied based on vibration mode and damping prediction.The modal responses of the SACLD manipulator model at rest and rotation are obtained.In addition,the four model indices are optimized using the GA-BP neural network:axial incision size,axial incision position,circumferential incision size,and circumferential incision position.Finally,the best model for vibration suppression is obtained.

基于零点配置的分力合成主动振动抑制方法研究(英文)

The component synthesis active vibration suppression method （CSVS） can be applied to suppress the vibration of flexible systems. By this method, several same or similar time-varying components are arranged according to certain rules along the time axis. The synthesized command can suppress the arbitrary unwanted vibration harmonic while achieving the desired rigid body motion. The number of the components increases rapidly when the number of harmonic vibration is growing. In this article, the CSVS based on zero-placement technique is used to construct the synthesized command to suppress the multi-harmonics simultaneously in the discrete domain. The nature of zero-placement method is to put enough zeros to cancel system poles at necessary points. The designed synthesized command has equal time intervals between each component and which is much easier to be implemented. Using this method, the number of components increases linearly with the increasing of the number of being suppressed harmonics. For the spacecraft with flexible appendages, CSVS based on zero-placement is used to design the time optimal large angle maneuver control strategy. Simulations have verified the validity and superiority of the proposed approach.

Combined control of fast attitude maneuver and stabilization for large complex spacecraft

In remote sensing or laser communication space missions, spacecraft need fast maneuver and fast stabilization in order to accomplish agile imaging and attitude tracking tasks. However, fast attitude maneuvers can easily cause elastic deformations and vibrations in flexible appendages of the spacecraft. This paper focuses on this problem and deals with the combined control of fast attitude maneuver and sta- bilization for large complex spacecraft. The mathematical model of complex spacecraft with flexible appendages and momentum bias actuators on board is presented. Based on the plant model and combined with the feedback controller, modal parameters of the closed-loop system are calculated, and a multiple mode input shaper utilizing the modal information is designed to suppress vibrations. Aiming at reducing vibrations excited by attitude maneuver, a quintic polynomial form rotation path planning is proposed with constraints on the actuators and the angular velocity taken into account. Attitude maneuver simulation results of the control systems with input shaper or path planning in loop are sepa- rately analyzed, and based on the analysis, a combined control strategy is presented with both path planning and input shaper in loop. Simulation results show that the combined control strategy satisfies the complex spacecraft＇s require- ment of fast maneuver and stabilization with the actuators＇ torque limitation satisfied at the same time.

MECHANICAL-ELECTRIC COUPLING DYNAMICAL CHARACTERISTICS OF AN ULTRA-HIGH SPEED GRINDING MOTORIZED SPINDLE SYSTEM

On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply, taking high-frequency converting current of inverter power switches into further consideration, a modified mechanical-electric coupling model is created. The created model consists of an inverter, a motorized spindle, a grinding wheel and grinding loads. Some typical non-stationary processes of the grinding system with two different supplies, including the starting, the speed rising and the break in grinding loads, are compared by making use of the created model. One supply is an ideal sinusoidal voltage source, the other is an inverter. The theoretical analysis of the high-order harmonic is also compared with the experimental result. The material strategy of suppressing high-order harmonic mechanical-electric coupling vibration by optimizing inverter operating parameters is proposed.