Hybrid Passive/Active Vibration Control of a Loosely Connected Spacecraft System

In this paper,a hybrid passive/active vibration(HPAV)controller of a loosely connected spacecraft consisting of a servicing satellite,a target and an X-shape structure isolator is first proposed to suppress vibrations of the system when subjected to the impulsive external excitations during the on-orbit missions.The passive dynamic response of the combined system can be adjusted appropriately to achieve the desired vibration isolation performance by tuning the structural parameters of the bio-inspired X-shape structure.Moreover,the adaptive control design through dynamic scaling technique is selected as the active component to maintain high vibration isolation performance in the presence of parameter uncertainties such as mass of the satellite platform,the damping and rotation friction coefficients of the X-shape structure.Compared with the pure passive system and the traditional spring-mass-damper(SMD)isolator,the HPAV strategy witnesses lower transmissibility,smaller vibration amplitude and higher convergence rate when subjected to the post-capture impact.Numerical simulations demonstrate the feasibility and validity of the proposed hybrid control scheme in suppressing vibrations of the free-floating spacecraft.

Real-time Design Constraints in Implementing Active Vibration Control Algorithms

Although computer architectures incorporate fast processing hardware resources, high performance real-time implementation of a complex control algorithm requires an efficient design and software coding of the algorithm so as to exploit special features of the hardware and avoid associated architecture shortcomings. This paper presents an investigation into the analysis and design mechanisms that will lead to reduction in the execution time in implementing real-time control algorithms. The proposed mechanisms are exemplified by means of one algorithm, which demonstrates their applicability to real-time applications. An active vibration control （AVC） algorithm for a flexible beam system simulated using the finite difference （FD） method is considered to demonstrate the effectiveness of the proposed methods. A comparative performance evaluation of the proposed design mechanisms is presented and discussed through a set of experiments.

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.

SVD Approach for Actuator and Sensor Placement in Active Vibration Control of Large Cable Net Structures

The actuator and sensor placement problem for active vibration control of large cable net structures is investigated in this paper.Since the structures exhibit closely spaced modes in the range of low frequencies,the number of modes to be considered is quite large after modal truncation,while only a limited number of actuators and sensors are to be placed.This makes it hard to determine the actuator and sensor locations with the existing placement methods in the literature such as the methods based on the controllability/observability grammian.To deal with this issue,an actuator and sensor placement method based on singular value decompositions(SVD)of the input and output matrices is proposed,which guarantees the modal controllability and observability of the system.The effectiveness of the SVD based method is verified through numerical simulations in which comparisons are conducted between randomly-chosen locations and the optimal ones obtained by a genetic algorithm.

Self-Powered Active Vibration Control:Concept,Modeling,and Testing

Despite their superior control performance,active vibration control techniques cannot be widely used in some engineering fields because of their substantial power demand in controlling large-scale structures.As an innovative solution to this problem,an unprecedented self-powered active vibration control system was developped in this study.The topological design,working mechanism,and power flow of the proposed system are presented herein.The self-powering ability of the system was confirmed based on a detailed power flow analysis of vibration control processes.A self-powered actively controlled actuator was designed and applied to a scaled active vibration isolation table.The feasibility and effectiveness of the innovative system were successfully validated through a series of analytical,numerical,and experimental investigations.The setup and control strategy of the proposed system can be readily extended to diversified active vibration control applications in various engineering fields.

NONLINEAR DYNAMIC RESPONSE AND ACTIVE VIBRATION CONTROL OF THE VISCOELASTIC CABLE WITH SMALL SAG

The problem considered is an initially stressed viscoelastic cable with small sag. The cable material is assumed to be constituted by the hereditary differential type. The partial differential equations of motion is derived first. Then by applying Galerkin's method, the governing equations are reduced to a set of third order nonlinear ordinary differential equations which are solved by Runge-Kutta numerical integration procedures. Only after the transverse vibration of the plane is considered and the nonlinear terms are neglected, can the nonlinear ordinary differential equations be expressed as a continuous state equation in the state space. The matrix of state transition is approximated stepwise by the matrix exponential; in addition, the state equation is discretized to a difference equation to improve the computing efficiency. Furthermore, an optimal control of procedure system based on the minimization of a quadratic performance index for state vector and control forces is developed. Finally, the effect of dynamic response of the cable, which is produced by viscoelastic parameters, is testified by the research of digital simulation.

Active Vibration Control of Rotating Machines with Active Machine Foot Mounts on Soft Foundations Based on a 3D-Model

The paper presents a simplified 3D-model for active vibration control of rotating machines with active machine foot mounts on soft foundations, considering static and moment unbalance. After the model is mathematical described in the time domain, it is transferred into the Fourier domain, where the frequencies response functions regarding bearing housing vibrations, foundation vibrations and actuator forces are derived. Afterwards, the mathematical coherences are described in the Laplace domain and a worst case procedure is presented to analyze the vibration stability. For special controller structures in combination with certain feedback strategies, a calculation method is shown, where the controller parameters can be directly implemented into the stiffness matrix, damping matrix and mass matrix. Additionally a numerical example is presented, where the vibration stability and the frequency response functions are analyzed.

DOUBLE LOOP ACTIVE VIBRATION CONTROL OF PNEUMATIC ISOLATOR WITH TWO SEPARATE CHAMBERS

A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.

ACTIVE VIBRATION CONTROL OF FINITE L-SHAPED BEAM WITH TRAVELLING WAVE APPROACH

In this paper, the disturbance propagation and active vibration control of a finite L-shaped beam axe studied. The dynamic response of the structure is obtained by the travelling wave approach. The active vibration suppression of the finite L-shaped beam is performed based on the structural vibration power flow. In the numerical calculation, the influences of the near field effect of the error sensor and the small error of the control forces on the control results are all considered. The simulation results indicate that the structural vibration response in the medium and high frequency regions can be effectively computed by the travelling wave method. The effect of the active control by controlling the power flow is much better than that by controlling the acceleration in some cases. And the control results by the power flow method are slightly affected by the locations of the error sensor and the small error of the control forces.

An active vibration control method based on energy-fuzzy for cantilever structures excited by aerodynamic loads

In wind tunnel tests for the full-model fixed with sting,the low structural damping of the long cantilever sting results in destructive low-frequency and large-amplitude vibration.In order to obtain high-quality wind tunnel test data and ensure the safety of wind tunnel tests,an energy-fuzzy adaptive PD(Proportion Differentiation)control method is proposed.This method is used for active vibration control of a cantilever structure under variable aerodynamic load excitation,and real-time adjustment of parameters is achieved according to the system characteristics of vibration energy.Meanwhile,a real-time method is proposed to estimate the real-time vibration energy through the vibration acceleration signal,and the average exciting power of aerodynamic load is obtained by deducting the part of the power contributed by the vibration suppressor from the total power.Furthermore,an energy-fuzzy adaptive PD controller is proposed to achieve adaptive control to the changes of the aerodynamic load.Besides,the subsonic and transonic experiments were carried out in wind tunnel,the results revealed that comparing to fixed gain PD controllers,the energy-fuzzy adaptive PD controller maintains higher performance.

Vibration analysis and active control of nearly periodic two-span beams with piezoelectric actuator/sensor pairs

The piezoelectric materials are used to investigate the active vibration control of ordered/disordered periodic two-span beams. The equation of motion of each sub-beam with piezoelectric patches is established based on Hamilton＇s principle with an assumed mode method. The velocity feedback control algorithm is used to design the controller. The free and forced vibration behaviors of the two-span beams with the piezoelectric actuators and sensors are analyzed. The vibration properties of the disordered two-span beams caused by misplacing the middle support are also researched. In addition, the effects of the length disorder degree on the vibration performances of the disordered beams are investigated. From the numerical results, it can be concluded that the disorder in the length of the periodic two-span beams will cause vibration localizations of the free and forced vibrations of the structure, and the vibration localization phenomenon will be more and more obvious when the length difference between the two sub-beams increases. Moreover, when the velocity feedback control is used, both the forced and the free vibrations will be suppressed. Meanwhile, the vibration behaviors of the two-span beam are tuned.

SIMULATION RESEARCH OF ACTIVE VIBRATION CONTROL FOR ELASTIC MISSILE WITH SWING NOZZLE THRUST VECTOR CONTROL

Aiming at the deficiencies of notch filters on the aspect of vibration suppression for elastic missile with swing nozzle thrust vector control(SNTVC),an active vibration controller(AVC)is proposed.It is composed of an optimal state feedback controller(OSFC)and an optimal minimal order state observer(OMOSO),which can be respectively designed based on the separation principle.The design rules of these two elements are successively given.Computer simulation results present that AVC can realize strong vibration suppression and good convergence property after disturbing.Moreover,it has simple design and then it is easily implemented in engineering.In addition,the AVC scheme can also resolve the poor system stability to a great extent,which is resulted from the bad static stability of missile body.

Independent modal variable structure fuzzy active vibration control of thin plates laminated with photostrictive actuators

Photostrictive actuators can produce photodeformation strains under illumination of ultraviolet lights. They can realize non-contact micro-actuation and vibration control for elastic plate structures. Considering the switching actuation and nonlinear dynamic characteristics of photostrictive actuators, a variable structure fuzzy active control scheme is presented to control the light intensity applied to the actuators. Firstly, independent modal vibration control equations of photoelectric laminated plates are established based on modal analysis techniques. Then, the optimal light switching function is derived to increase the range of sliding modal area, and the light intensity self-adjusting fuzzy active controller is designed. Meanwhile, a continuous function is applied to replace a sign function to reduce the variable structure control （VSC） chattering. Finally, numerical simulation is carried out, and simulation results indicate that the proposed control strategy provides better performance and control effect to plate actuation and control than velocity feedback control, and suppresses vibration effectively.

VIBRATION CONTROL OF FLUID-FILLED PRISMATIC SHELL WITH ACTIVE CONSTRAINED LAYER DAMPING TREATMENTS

Active constrained layer damping （ACLD） combines the simplicity and reliability of passive damping with the light weight and high efficiency of active actuators to obtain high damping over a wide frequency band. A fluid-filled prismatic shell is set up to investigate the validity and efficiency of ACLD treatments in the case of fluid-structure interaction. By using state subspace identification method, modal parameters of the ACLD system are identified and a state space model is established subsequently for the design of active control laws. Experiments are conducted to the fluid-filled prismatic shell subjected to random and impulse excitation, respectively, For comparison, the shell model without fluid interaction is experimented as well. Experimental results have shown that the ACLD treatments can suppress vibration of the fluid-free and fluid-filled prismatic shell effectively. Under the same control gain, vibration attenuation is almost the same in both cases.

Active control of an aircraft tail subject to harmonic excitation

Vibration of structures is often an undesirable phenomena and should be avoided or controlled. There are two techniques to control the vibration of a system, that is, active and passive control techniques. In this paper, a negative feedback velocity is applied to a dynamical system, which is represented by two coupled second order nonlinear differential equations having both quadratic and cubic nonlinearties. The system describes the vibration of an aircraft tail. The system is subjected to multi-external excitation forces. The method of multiple time scale perturbation is applied to solve the nonlinear differential equations and obtain approximate solutions up to third order of accuracy. The stability of the system is investigated applying frequency response equations. The effects of the different parameters are studied numerically. Various resonance cases are investigated. A comparison is made with the available published work.

Nonlinear integral resonant controller for vibration reduction in nonlinear systems

A new nonlinear integral resonant controller（NIRC） is introduced in this paper to suppress vibration in nonlinear oscillatory smart structures. The NIRC consists of a first-order resonant integrator that provides additional damping in a closed-loop system response to reduce highamplitude nonlinear vibration around the fundamental resonance frequency. The method of multiple scales is used to obtain an approximate solution for the closed-loop system.Then closed-loop system stability is investigated using the resulting modulation equation. Finally, the effects of different control system parameters are illustrated and an approximate solution response is verified via numerical simulation results.The advantages and disadvantages of the proposed controller are presented and extensively discussed in the results. The controlled system via the NIRC shows no high-amplitude peaks in the neighboring frequencies of the resonant mode,unlike conventional second-order compensation methods.This makes the NIRC controlled system robust to excitation frequency variations.

ACTIVE VIBRATION SUPPRESSION VIA LINEARIZING HYSTERESIS OF PIEZOCERAMIC ACTUATORS

A novel active vibration control technique on the basis of linearized piezoelectric actuators is presented. An experimental apparatus consisting of a cantilever beam to which are attached strain patches and piezoceramic actuators to be used for active vibration suppression is described. A dynamical model of the cantilever beam using Lagrange＇s equation and two coordinate systems are presented. Based on the Lyapunov＇s direct method, an active vibration controller with hysteresis compensation is designed. The controller is designed so that it guarantees the global stability of the overall system. The controller developed is assessed experimentally.

ACTIVE CONTROL OF FLEXIBLE BEAMS SUBJECTED TO MULTI-DISTURBANCE USING ONE CONTROLLER

The active control of vibration for a beam subjected to multi-disturbances is investigated based on wave propagating suppression. In this control system, there are the same numbers of the sensors, the signal inputting to the controller and the disturbances, but there is only one controller. It is a local control system, the system parameters depend only on the characteristics of the structure bounded by the sensors and the controller, and we need not take into account. the boundary conditions and the properties of structures outside of this held. The system is efficient when a structure vibrates in middle and high frequency regions. Some control design rules are developed from the calculation results.

PASSIVE-ACTIVE CONTROL OF POWER FLOW IN AN ISOLATION SYSTEM MOUNTED ON FLEXIBLE FOUNDATIONS

A general model of flexible isolation systems which involves both the passive and active control factors is established by inserting actuators into an passive isolation system. And the power flow transmission function in such a system as with multi disturbance, multi mounts, passive isolators and actuators is deduced. By means of the numerical simulation method, the influence of actuators on power flow transmission characteristic is studied. And as a conclusion, the passive active synthetic control strategy of power flow is summarized.