Active Vibration Research Articles

Distributed active vibration control for helicopter based on diffusion collaboration

The active vibration control technology has been successfully applied to several helicopter types. However, with the increasing of control scale, traditional centralized control algorithms are experiencing significant increase of computational complexity and physical implementation challenging. To address this issue, a diffusion collaboration-based distributed Filtered-x Least Mean Square algorithm applied to active vibration control is proposed, drawing inspiration from the concept of data fusion in wireless sensor network. This algorithm distributes the computation load to each node, and constructs the active vibration control network topology of large-scale system by discarding the weak coupling secondary paths between nodes, achieving distributed active vibration control. In order to thoroughly validate the effectiveness and superiority of this algorithm, a helicopter fuselage model is designed as the research object. Firstly, the excellent vibration reduction performance of the proposed algorithm is confirmed through simulations. Subsequently, specialized node control units are developed, which utilize STM32 microcontroller as the processing unit. Further, a distributed control system is constructed based on multi-processor collaboration. Building on this foundation, a large-scale active vibration control experimental platform is established. Based on the platform, experiments are carried out, involving the 4-input 4-output system and the 8-input 8-output system. The experimental results demonstrate that under steady-state harmonic excitation, the proposed algorithm not only ensures control effectiveness but also reduces computational complexity by 50%, exhibiting faster convergence speed compared with traditional centralized algorithms. Under time-varying external excitation, the proposed algorithm demonstrates rapid tracking of vibration changes, with vibration amplitudes at all controlled points declining by over 94%, proving the strong robustness and adaptive capability of the algorithm.

A Transportable Atomic Gravimeter with Constraint-Structured Active Vibration Isolation.

Many efforts have been taken in recent years to push atomic gravimeters toward practical applications. We demonstrate an atomic gravimeter named NIM-AGRb2 that is transportable and suitable for high-precision gravity measurements. Constraint-structured active vibration isolation (CS-AVI) is used to reduce the ground vibration noise. The constraint structure in CS-AVI ensures that the isolation platform only has vertical translation, with all other degrees of freedom (DoFs) being constrained. Therefore, the stability of active vibration isolation is enhanced. With the implementation of CS-AVI, the sensitivity of NIM-AGRb2 reached as low as 20.5 μGal/Hz1/2. The short-term sensitivity could be further reduced to 10.8 μGal/Hz1/2 in a seismologic observation station. Moreover, we evaluated the system noise of the gravimeter, and the results were consistent with our observations.

Dynamic Analysis and Optimization on Passive/Active Vibration Reduction of a Beam Structure with Distributed Smart Foams

A smart foam is a vibration absorption structure integrated with piezoelectric material and shows promise for a highly efficient structural vibration reduction both passively and actively. The arrangement of the smart foams on the primary structure is a key issue in practical engineering. In this work, the vibration reduction performances of distributed smart foams attached to a simply supported beam are investigated, and the distribution scheme is optimized. The dynamic equations of the vibration system are established for passive and active vibration reduction, respectively. The frequency responses are analyzed based on a Newmark-[Formula: see text] method, and the accuracy is verified by a finite element analysis. An optimization method based on the genetic algorithm is proposed for the smart foams’ quantity and locations. The study reveals that, with the same total attached mass (1% of the beam mass), a limited distribution of smart foams achieves a larger vibration reduction ratio than a single smart foam or uniformly distributed smart foams. For the passive reduction mode, the optimal scheme is to arrange four smart foams at the middle of the beam, and a reduction ratio of 38% is achieved. It is related to both the first-order modal shape of the beam and the mass distribution of smart foams. For the active reduction mode, the optimal scheme is to arrange two smart foams separately, and 98% of the vibration is reduced. The optimal location is no longer at the middle of the beam, because the active moment of the piezoelectric beam makes the main contribution, rather than the passive vibration absorption. This research provides an optimization method and instructions for both passive and active vibration reductions of smart foams.

A computational characterization of N-heterocyclic carbenes for catalytic and nonlinear optical applications

Abstract Very recently, N-heterocyclic carbenes (NHCs) have found a wide range of applications in the fields of catalysis and nonlinear optics. Herein, we have employed 1,3-bis-(1(S)-benzyl)-4,5-dihydro-imidazol-based carbene as a reference molecule and substituted one H atom from each CH2 of the benzyl groups in both sides by CH3, NH2, and CF3 to study the thermodynamic and opto-electronic properties of NHCs theoretically. It was observed that the enthalpy (H), Gibb’s free energy (G), specific heat capacity (C v), and entropy (S) increase significantly in the presence of the electron-withdrawing groups compared to the electron-donating groups. The IR active in-plane bending vibrations of the CH (NHC) group are shifted to the higher frequency region for the considered substituted molecules compared to the reference carbene. The analysis of the electronic properties shows that the CH3-substituted carbene is more reactive for catalytic activities compared to other NHCs. The calculated nonlinear optical (NLO) properties reveal that the NH2-substituted NHC has the largest hyperpolarizability value whereas the CH3-substituted NHC has the largest dipole moment and polarizability among all, making them potential candidates for the development of NLO materials.

State Observing Method and Active Vibration Control Based on Virtual Sensing

State feedback is mostly used in the active vibration control of structural systems. However, the most challenging problem is to achieve the whole state of the structure. Another issue in active vibration control is that, in many cases, only some particular modes need to be controlled, while the other modes can remain unchanged in order to save on the costs of the control. To solve the above issues, this paper proposes a state-observing method and conducts a non-spillover partial pole placement control using a multistep method. Using the finite element method, the electromechanical coupling equations of motion of the beam are formulated. The reduced finite element model is then obtained by using the system equivalent reduction expansion process method. Introducing the real measurements by sensors and applying the local corresponding principle, the modes of the structural system are corrected, which are then utilized to predict all the degrees of freedom without measuring by sensors. Then, the non-spillover partial pole placement based on the state feedback is conducted using the multistep method. The optimal locations of actuators are derived by the genetic algorithm to control the specific structural modes effectively. The numerical simulations and experimental studies are also carried out.

Active vibration control in robotic grinding using six-axis acceleration feedback

Industrial robots endure severe vibrations in the grinding process due to factors such as joint flexibility, low damping, and contact force fluctuations. Additionally, the motion control of the robot primarily relies on feedback signals from the motor-side encoders, while lacking motion state feedback from the load side. This exacerbates the robot vibrations, severely compromising the surface quality of the workpieces. To address this problem, an active damping control method for robotic grinding using six-axis acceleration feedback is proposed. This method realizes a simple, reliable, and efficient active vibration control without altering the robot body. A multi-sensor fusion Cartesian space six-axis accelerometer is designed and integrated into the robot end effector, achieving accurate feedback on the robot load side vibration state. The strategy of six-axis acceleration decoupling and principle of the vibration suppression with the acceleration feedback are explained. Compared with conventional sensing schemes, this reduces joint acceleration approximation errors and end vibrations. The robotic grinding experiments are carried out on aeronautic structural parts. Extensive case studies demonstrate that the proposed approach can effectively control the vibration caused by joint flexibility in the robot grinding process, and greatly improve the surface quality of workpieces. This method has great potential application in vibration suppression during robotic grinding and polishing.

Final state control-based active compensation for backlash in vibration suppression of automobile powertrain

This paper proposes an effective backlash compensation method based on the final state control (FSC) for active vibration control of an automobile powertrain. Transient vibration of the powertrain caused by sudden changes in the engine torque significantly degrades the driving performance and driver comfort. In addition, the nonlinear characteristics owing to the backlash increase the adverse effects of these oscillations. To suppress the transient vibration of the powertrain, a controller is designed based on the mixed H2/H∞ control theory. Subsequently, to adjust for the vibration amplification owing to the backlash, we propose the application of a shock-reducing controller based on the FSC. Linearly decreasing the inertia weight in particle swarm optimisation (LDWPSO) was applied to the design of this controller and parameters were optimised. Finally, simulations were conducted using the control method; the controller could prevent the occurrence of shocks owing to the gear collisions and achieved smooth an acceleration.

Individual Blade Control Approach for Active Vibration Suppression of a Lift-Offset Coaxial Rotorcraft

This study explores the best vibration reduction using an individual blade control (IBC) actuation scheme for a lift-offset coaxial helicopter in high-speed flight. The rotorcraft dynamics analysis model consists of coaxial, three-bladed counter-rotating rotors and a finite element fuselage stick model constructed based on the measured data of the XH-59A helicopter. The XH-59A helicopter is well-known for its severe vibration level encountered during the flight (over 0.5g), leading to the cancellation of the development program. A special focus is given to assessing the accuracy and efficiency of the integrated rotor–body vibration predictions evaluated between the one-way and two-way coupling methods in reference to the flight data of the vehicle. The two-way rotor–body coupled results show excellent correlations with the test data for rotor blade loads and airframe vibrations. The best actuation scenarios are then sought for the minimum vibration at the rotor hub and the pilot seat. The IBC pitch actuation effectively reduces the vibrations at both locations of the rotorcraft. Specifically, a multiple-harmonic IBC actuation enables to suppress the pilot seat vibration by 93% compared to the uncontrolled case, achieving a significantly reduced vibration level (below 0.05g).

A Time Delay Estimation Interpretation of Extended State Observer-Based Controller With Application to Structural Vibration Suppression

This paper aims to investigate the disturbance estimation mechanism of extended state observer (ESO) from a new perspective: a time-delay estimation (TDE) interpretation. By drawing the concept of input-output linearization, ESO is transformed into an equivalent TDE form in frequency domain. The establishment of this relationship can lead to an improved understanding of ESO’s principle. In addition, ESO’s parameters for disturbance estimation are given with explicitly physical meanings. Furthermore, theoretical analysis from this perspective also results in a quantitative relationship between ESO estimation performance and its two tuning parameters including control gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$b_0$</tex-math> </inline-formula> and bandwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\omega _o$</tex-math> </inline-formula> . Theoretical results are evaluated by using an all-clamped plate structure with an inertial actuator, which is considered to be a typical benchmark for active vibration control. Extensive comparative experiments validate algorithm effectiveness. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This paper was focused on the ability of extended state observer (ESO) to estimate total disturbances. The controlled system is a typical benchmark for active vibration control consisting of an all-clamped plate structure with an inertial actuator. The model uncertainties and external disturbances that bothers the system is compensated by the real-time estimation of the ESO. In order to facilitate practical engineering applications, the distinct physical meanings of ESO parameters are expounded with the help of the relationship between ESO and time delay estimation (TDE) established in frequency domain. Moreover, the influence of parameters control gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$b_0$</tex-math> </inline-formula> and bandwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\omega _o$</tex-math> </inline-formula> on ESO is qualitatively established. Therefore, the engineer can avoid fall into a trial-and-error strategy that could be laborious and time-consuming. Thus, this paper proposed a convenient way for practitioners interested in developing anti-disturbance control strategies based on ESO. The simplicity and the partial-model-based characteristics are also profitable in practice. Potential applications include robotic systems, smart structures and electrical drives. In the future, the improvements of ESO based on the proposed method to deal with the intractable disturbances should be taken in an effort.

Research of the readout electronics for X-ray beam-position feedback system of SAPS

For 4th generation synchrotron radiation (SR) light sources, the X-ray beam-position stability is one of the crucial factors in cutting-edge experiments. Instead of traditional passive vibration isolation techniques, active vibration isolation measures based on feedback control technology have begun to play an important role for stabilizing the beam-position. The readout electronics of the feedback control system is presented in the paper. The proposed design is based on the integration of proportion integral differential (PID) controller and system on chip (SoC) module. By using the ARM for analyzing the convergence speed of PID controller with different parameters and configuring it, the readout electronics flexibly adapts to different vibration environments. The readout circuits based on this method is implemented for southern advanced photon source, and tests are carried out in the laboratory to evaluate the readout electronics. The results show that it can weaken the influence of vibration sources below 5Hz on the beam-position.

Piezoceramics Actuator with Attached Mass for Active Vibration Diagnostics of Reinforced Concrete Structures.

One of the effective methods of non-destructive testing of structures is active vibration diagnostics. This approach consists of the local dynamic impact of the actuator on the structure and the registration of the vibration response. Testing of massive reinforced concrete structures is carried out with the use of actuators, which are able to create sufficiently high-impact loads. The actuators, which are based on piezoelectric elements, cannot provide a sufficient level of force and the areas where it is possible to register the vibrations excited by such actuators are quite small. In this paper, we propose a variant of a piezoactuator with attached mass, which ensures an increase in the level of dynamic impact on the structure. The effectiveness of this version is verified by numerical modeling of the dynamic interaction of the actuator with a concrete slab. The simulation was carried out within the framework of the theory of elasticity and coupled electroelasticity. An algorithm for selecting the value of the attached mass is described. It is shown that when vibrations are excited in a massive concrete slab, an actuator with an attached mass of 1.3 kg provides a 10,000-fold increase in the force compared to an actuator without attached mass. In the pulse mode, a 100-fold increase in force is achieved.

Active vibration control of rotating smart bidirectional FGPTC subjected to internal mechanical shock

This study considers the active vibration control of a sandwich truncated cone, whose intermediate layer is made of bidirectional functionally graded (FG) porous material bonded with integrated piezoelectric actuator and sensor layers on its outer and inner surfaces. The material properties of the bidirectional functionally graded porous truncated cone (FGPTC), with even and uneven porosity distributions along the length and thickness directions, are changed using a power law function. The governing motion equations utilize the two-dimensional (2D) axisymmetric theory of elasticity rather than simple shell theories. The solving of the governing motion equations is accomplished through the utilization of graded finite element and Newmark methods. The study investigates the impact of dimensions, parameters, and porosity types on transient response behavior, including the semi-vertex angle and the ratio of truncated cone length to outer radius. Furthermore, the effects of power index, porosity volume fractions, rotational velocities, and boundary conditions are examined. Active vibration control (AVC) of the piezoelectric FGPTC is achieved by employing a closed-loop control algorithm based on velocity feedback. Several numerical simulations are conducted to evaluate the effectiveness of the proposed active vibration control system in reducing structural vibrations. The results demonstrate significant reductions in vibration amplitudes and improved structural stability achieved through the active control approach.

Linear parameter-varying output-feedback for active vibration control of an elastic kinetic roof structure with experimental validation

Elastic kinetics are an approach to design transformable lightweight structures with a stable transformation process. The transformation is realized through elastic bending of structural members by exploiting the compliant material behavior. This lightweight and flexible design comes at the cost of increased sensitivity to static and dynamic disturbances. However, most of the current research focuses on the principles of elastic kinetic transformation instead of effective disturbance mitigation. This work focuses on dynamic disturbance mitigation for such transformable lightweight structures using active control. Modeling and controller synthesis are performed in the linear parameter-varying (LPV) framework, since the dynamics of elastic kinetic structures are transformation-state dependent due to geometric nonlinearities. Based on an LPV model in a grid-based representation, an LPV output-feedback control can be designed and synthesized via a gridding approach. This methodology is experimentally tested and validated for the example of an active hybrid roof structure prototype.

Analysis of the influence of mechanical vibration control strategy on structural safety

The vibration of rotating machinery has always been the focus of attention in the engineering field, because it directly affects the performance, life and safety of equipment. In this paper, the influence of vibration control strategy of rotating machinery on structural safety is deeply studied, aiming at providing scientific basis for optimizing vibration control scheme. It is found that the network identification accuracy of vibration signals of rotating machinery is above 96% under different vibration conditions by the vibration control method designed in this paper, which is higher than the traditional control method. Active vibration control strategy has high accuracy and real-time, but it challenges the cost and complexity of the system. Passive vibration control strategy is excellent in specific frequency vibration suppression, but there are some limitations in multimode vibration; Semi-active vibration control strategy has both active and passive advantages and strong adaptability, but it needs complex control algorithm. These efforts will provide useful reference for the development of vibration control field of rotating machinery and the safety improvement of engineering structures.

Novel coarse and fine stage parallel vibration isolation pointing platform for space optics payload

A coarse and fine parallel vibration isolation pointing platform (CFPP) is proposed, which can realize a wide range of motion and active vibration isolation for space optical payload. First the coarse and fine parallel connection scheme is designed based on the Stewart generalized configuration. Kinematic and constraint analyses are performed to determine the two operation modes of the platform. The platform is then structurally designed. System dynamics model is established based on the Lagrange method, and the dynamic disturbance characteristics are analyzed. Next, the active vibration isolation control algorithm based on H∞ loop shaping is designed. The stability of the control system is analyzed. Finally, the prototype is constructed, and the three-axis pointing range test and active vibration isolation experiments in four attitudes are carried out, and the experimental results show that the designed pointing vibration isolation system with coarse and fine stages in parallel can achieve a 7° movement range of the three axes, and it has a maximum vibration isolation capacity of 20 dB for the disturbance in the frequency band of 2–20 Hz. It has great application prospects in the direction of miniaturization and integration of space optical payload in the future.

Effect of mechanical vibration and its influence on thermal performance of a nanofluid heat exchanger

Many situations involve flowing fluids on nonstationary platforms. For example, moving vehicles undergo vibrations in their transit. The effect of vibration on heat exchangers with nanofluids as working fluids has not been explored systematically, and this study examines the impact of vibrations in these situations. Vibrations having amplitudes in the range of 1–5 mm, and frequencies from 6 to 25 Hz are investigated. A 2% volume fraction Al2O3 solution with water as the base fluid has been utilized as the fluid; Reynolds numbers ranging from 10,000 to 25,000 were considered. The Nusselt number, friction factor, factor of merit, and effective thermal performance have been used to assess the heat transfer augmentation caused by vibration. It is found that the heat transfer characteristics are significantly enhanced by the active vibration provided in the form of a time-dependent sinusoidal velocity perpendicular to the axis of the heat exchanger tube. An increase of up to 70% in the Nusselt number was observed compared to the case without vibration. But, the friction factor was also enhanced; hence, a factor of merit and thermal performance factor was used as a comprehensive measure for changes to the performance. It was found that for a 5 mm amplitude and a 25 Hz frequency, a 30.7% rise in the factor of merit was observed with respect to the case where the tube is static. In addition, the thermal performance factor increased by 1.3.

Online active vibration control for the magnetic suspension rotor using least mean square and polynomial fitting

Online active vibration control for the magnetic suspension rotor using least mean square and polynomial fitting

Fuzzy algorithm-based active control method for vibration of a mechanical gear transmission system

The detached raft automatic frequency isolation system is a complicated system with high exceptionally nonlinear, high electromagnetic, and multi-source vibration modes. However, it generates a statistical method and it is hard to operate the organization. The fuzzy control algorithm, as an astute control method, can give a keen path to the active management of a complicated system of floating rafts. This study uses a system identification approach to construct mathematical models for a floating raft active vibration isolation system with discrete transfer work. The fuzzy model is used in tests and simulations controller is built using two contributions of acceleration and its variation, as well as a single result of control voltage. The control isolation system is a complicated system with many moving parts. A lot of moving parts profoundly nonlinear, high electromagnetic and multi-source vibration modes, generating a statistical method and it is hard to operate the organization. The fuzzy control algorithm, as a smart control method, can give a keen path to the active management of a sophisticated floating raft system. This research uses an identification strategy to construct a floating raft active vibration isolation technology discrete transfer work mathematical models. The fuzzy controller is then put together using two contributions: acceleration and variation, as well as a single outcome of control voltage for simulations and experiments research.

Nanoscale Localized Phonons at Al2O3 Grain Boundaries.

Nanoscale defects like grain boundaries (GBs) would introduce local phonon modes and affect the bulk materials' thermal, electrical, optical, and mechanical properties. It is highly desirable to correlate the phonon modes and atomic arrangements for individual defects to precisely understand the structure-property relation. Here we investigated the localized phonon modes of Al2O3 GBs by combination of the vibrational electron energy loss spectroscopy (EELS) in scanning transmission electron microscope and density functional perturbation theory (DFPT). The differences between GB and bulk obtained from the vibrational EELS show that the GB exhibited more active vibration at the energy range of <50 meV and >80 meV, and further DFPT results proved the wide distribution of bond lengths at GB are the main factor for the emergence of local phonon modes. This research provides insights into the phonon-defect relation and would be of importance in the design and application of polycrystalline materials.

Linear active disturbance rejection control algorithm for active vibration control of piezo-actuated beams: Theoretical and experimental studies

The active vibration control (AVC) of lightweight thin-walled structures on spacecraft has been a proven solution for vibration suppression. In this study, a linear active disturbance rejection control (LADRC) algorithm is presented for vibration suppression of piezo-actuated beams. Firstly, the governing equation of a piezo-actuated beam is obtained by using the Euler–Bernoulli beam theory and the Lagrange equation. The LADRC algorithm is designed for the piezo-actuated beam based on the governing equation. Then, the accuracy of the piezo-actuated beam model is confirmed by comparison with ANSYS and experiments. Finally, numerical simulations and experiments are carried out on the active vibration suppression of the piezo-actuated beam under the fixed harmonic excitation, variable harmonic excitation, and fixed harmonic excitation with measuring noise, respectively. The results show that the LADRC algorithm has an excellent control effect on structural vibration suppression, strong adaptability to various external excitations, and anti-noise ability.