Active Vibration Control Scheme Research Articles

Active vibration control using minimum actuation power: Multiple primary sources controlled by multiple secondary sources

Minimum Actuation Power (MAP) is a novel active vibration control strategy that minimizes the total input power into the structure by monitoring the input power from the secondary source. In a previous paper, we presented the theory for MAP for a single primary source controlled by a single secondary source and demonstrated the application of MAP for rotorcraft interior noise control. In this paper, we extend the theoretical framework for MAP for multiple primary sources (excitation) controlled by multiple secondary sources (control). We show that the input power from the secondary sources is zero only when the secondary sources are located such that the phase of the cross-mobility term for each primary–secondary pair is same. This condition puts a constraint on the location of the secondary sources with respect to the primary sources so that the input power from the secondary sources is zero. We present simulations for a simply supported plate excited by two primary sources and controlled by a single secondary source that validate the theoretical findings. We also study the effect of phasing between the primary sources on MAP control performance and show that the maximum power reduction is obtained when the phase difference between the primary sources is zero. Experimental results are provided that demonstrate the feasibility of the MAP theory.

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.

Adaptive active vibration control for composite laminated plate: Theory and experiments

In this paper, an analysis model of adaptive active vibration control system of composite laminated plate using macro fiber composite (MFC) piezoelectric patches is presented, and the experimental testing is carried out. Electromechanical coupling equations of the composite laminated plate are established by considering the influence of the mass and stiffness of MFC piezoelectric patches. The adaptive active vibration control scheme for composite laminated plate based on the filtered-x least mean square (FxLMS) algorithm is proposed. The accuracy of the present analysis model is validated by the results of experimental test and finite element method (FEM). It can be found that the vibration responses nearby the first and second natural frequencies of the composite laminated plate can be rapidly and greatly suppressed by the adaptive active control system and experimental test. Moreover, the dynamic responses of the composite plate under multi-frequency excitation and random excitation can be fast controlled by the presented adaptive active control system. The novelty of this work is that a theoritical analysis model of adaptive closed-loop control system based on the MFC piezoelectric patches is presented for vibration suppression of composite laminated plate, and the effectiveness of the proposed adaptive active model are validated by experimental testing.

An adaptive feedforward method in active vibration control for the propulsion shafting system

This paper proposes a new adaptive feedforward control method for the rejection of multiple periodic disturbances in the propulsion shafting system. The active vibration control scheme of the propulsion shafting system is established by employing the equivalent-input-disturbance principle which reduces the complexity of the control system in applications. The adaptive control algorithm is designed by taking the scale transformation procedure and the frequency-tracking technique into consideration. The scale transformation normalizes the iso-surface of the optimization function by the frequency response characteristics of the control channel, which immensely improves the convergence rate of the control algorithm for multi-harmonic disturbance. Moreover, the adaptive controller tracks the fluctuating frequencies in a direct method, enhancing the efficiency and robustness of the algorithm for eliminating time-varying disturbances. Finally, numerical simulation and experimental validation are carried out to show that the proposed method has good performance on the application of the active vibration control of the propulsion shafting system.

Modeling of Piezo Stack Actuators and Their Application in Active Vibration Control

This paper presents the vibration control of a highly simplified two degree of freedom model of a helicopter. The vibration control study has been performed using both active and passive vibration control schemes. In the case of active vibration control, the feedback mechanism affects the stiffness of the system; whereas in passive vibration control, the absorber mass affects the inertia of the system. The active control is achieved using a combination of piezo stack sensor and actuator mechanism. A finite element model for the piezo stack mechanism has been developed to obtain a relation between deformation, applied/induced potential and externally applied mechanical load. The results of this study indicate that inclusion of sensor and actuator units increases the natural frequency of the system due to increase in stiffness of the system. It is observed that in the case of active vibration control, the frequency response of acceleration of the system is highly sensitive to small variations in the magnitude of gain around its optimum value and insensitive to changes in excitation frequency; whereas in passive vibration control, the frequency response does not exhibit any significant change in the characteristics with respect to the variation in the absorber mass, while it is highly sensitive to changes in operating frequency.

Multiple-Frequency Force Estimation of Controlled Vibrating Systems with Generalized Nonlinear Stiffness

An on-line estimation technique of multiple-frequency oscillatory forces combined with the Hilbert–Huang transform for an important class of actively controlled, forced vibrating mechanical systems with nonlinear stiffness forces is proposed. Polynomial parametric nonlinearities are incorporated in the significantly perturbed vibrating system dynamics. This class of nonlinear vibrating systems can exhibit harmful large-amplitude vibrations, which are inadmissible in many engineering applications. Disturbing oscillations can be also provoked due to interactions of the primary mechanical system to be actively protected against dangerous vibrations with other forced uncertain multidegree-of-freedom nonlinear vibrating systems. Taylor’s series expansion to dynamically model uncertain vibrating forces into a small time window for real-time estimation purposes is employed. Intrinsic mode functions of multiple-frequency vibrating forces can be then obtained by the Hilbert-Huang transform. Uncertain instantaneous frequencies and amplitudes of disturbing oscillations can be directly computed in temporal space. An active vibration control scheme for efficient and robust tracking of prescribed motion reference profiles based on multiple frequency force estimation is introduced as well. The presented closed-loop on-line estimation technique can be extended for other classes of nonlinear oscillatory systems. Analytical, experimental and numerical results to prove the estimation effectiveness are presented. Numerical results show reasonable estimation errors of less than 2%.

Experimental verification of active damping of powertrain vibrations with simple fuzzy logic compensation for time-varying control period

To ensure comfortability and lifetime of components, transient vibrations in a vehicle powertrain must be suppressed. This study proposes a novel active vibration control strategy with straightforward fuzzy inference compensation for time-fluctuations of control periods of engines used as actuators. First, a model prediction algorithm including a sampled-data controller (SDC) is applied for addressing the maximal phase lag of the control input caused by the fluctuated control period. Fluctuated renewal timings of the control input that are deviated from those of the periodical operated SDC are defined by fuzzy sets. These fuzzy sets are expressed as “Nearly past timing” and “Nearly future timing.” Using a human-intuition-like fuzzy compensation with only four inference rules, unknown control inputs at fluctuated update timings are reasonably determined from such fuzzy sets and periodical control signals given by the SDC. Experiments using an actual test device are performed to investigate the damping performance of the proposed control scheme. The experimental tests demonstrate that the novel active damping strategy significantly reduces transient vibrations despite the fluctuated control period. Moreover, several different test conditions newly reveal the robustness of the fuzzy compensation against fluctuations of variable regions in the control periods.

Radio Frequency Cavity’s Analytical Model and Control Design

Reduction or suppression of microphonic interference in radio frequency (RF) cavities, such as those used in Electron Linear Accelerators, is necessary to precisely control accelerating fields. In this paper, we investigate modeling the cavity as a cylindrical shell and present its free vibration analysis along with an appropriate control scheme to suppress vibrations. To this end, we first obtain an analytical mechanical dynamic model of a nine-cell cavity using a modified Fourier-Ritz method that provides a unified solution for cylindrical shell systems with general boundary conditions. The model is then verified using the ANSYS software in terms of a comparison of eigenfrequencies which prove to be identical to the proposed model. We also present an active observer-based vibration control scheme to suppress the dominant mechanical modes of the cavity. The control system performance is investigated using simulations.

Novel Model-free Optimal Active Vibration Control Strategy Based on Deep Reinforcement Learning

Neural networks (NNs) can provide a simple solution to complex structural vibration control problems. However, most past NN-based control strategies cannot guarantee an optimal policy in structural vibration control. In this study, a novel active vibration control strategy based on deep reinforcement learning is proposed, which utilizes the learning ability of NN controllers and simultaneously provides control performance comparable to traditional model-based optimal controllers. The proposed learning algorithm can determine the control policy through interaction with the environment without knowing dynamic system models. This study shows that the proposed model-free strategy can provide optimal control performance to various systems and excitations. The proposed control strategy is first verified on a single-degree-of-freedom model and subsequently extended to a multi-degree-of-freedom shear-building model. Its control performance with full-state feedback is nearly the same as that of a classical linear quadratic regulator. Moreover, the learned policy can outperform a traditional output feedback controller in a partially observed system. The robustness of the proposed control strategy against measurement noise is also tested.

Sound Radiation from a Plate with Embedded Active Acoustic Black Holes

Acoustic Black Holes (ABHs) can be realised as tapered structural features that focus and absorb vibrational energy. In a plate, the damping effect of ABHs can be used to reduce the radiation efficiency, particularly above the critical frequency of the plate. However, at lower frequencies, there is still significant radiation due to the low order modes of the plate. It has previously been shown that the combination of active control and ABHs can result in an effective broadband control solution with lower computational and power requirements compared to a standalone active configuration. This paper presents an investigation into how two different active control strategies affect structural response and radiated sound power of a plate with active ABHs (AABHs). It is shown, through an active vibration control strategy and an active noise control strategy, that the AABHs can be used to successfully control either the global structural response of the plate or the radiated sound power. However, it is also shown that controlling either response can lead to an enhancement in the other.

Active Vibration Control Strategy for Online Application in a Range Extender

Noise, vibration and harshness are a big issue for hybrid vehicles especially in range extenders. Traditional vibration control and active damping control are generally used for suppressing vibration. Compared with traditional vibration control, active damping control is more flexible and effective in suppressing vibration. The basic idea of active damping control is controlling electric motor compensating for the torque of engine and reducing the vibration from the source. The reduction of vibration is highly depended on the compensation torque of the electric motor. A differently designed compensation torque has a significant impact on the active damping control effect. In this paper, an active damping control method for online application is proposed. And several kinds of compensation torque are designed for this method. Experiments on vibration performance are conducted to compare the effect of different compensation torque design in reducing vibration. And the results show that the compensation torque in the shape of square wave has potential for reducing vibration in all directions. Finally, a guiding tool for compensation design is proposed by correlation analysis and the relationship between designing factors and vibration is revealed.

Active vibration control of large space structures: Modelling and experimental testing of offset piezoelectric stack actuators

To meet demanding mission objectives, most current satellites for Earth and Universe observation are equipped with large flexible appendages. However, due to the coupling between spacecraft rigid and elastic dynamics, unwanted elastic vibrations of such flexible elements may compromise the achievement of pointing and stability requirements. Therefore, control solutions aiming at avoiding instabilities and, at worst, the failure of the mission, are currently needed. In this scenario, growing interest has been recently devoted to Active Vibration Control (AVC) strategies relying on the use of smart materials. Among them, piezoelectric patches are the most studied and tested devices for both actuating and sensing purposes. This paper aims to contribute to this line of research by investigating a different type of actuator, namely an Offset Piezoelectric Stack Actuator (OPSA), to assess its performance in damping out elastic vibrations of large space structures. Moreover, special attention is devoted to compare OPSA performance with standard patch actuators behaviour. In order to develop the AVC system, an equivalent electro-mechanical coupled Finite Element (FE) formulation is implemented, integrating both sensors and piezo-stack elements on the passive hosting structure. The final structural model including both electrical inputs/outputs, as well as modified mass and stiffness due to the additional piezo devices, is then obtained. A parametric analysis is carried out to optimize the maximum control action exerted by the OPSA device. Finally, the OPSA numerical model is experimentally validated by mounting it on a cantilever plate, representative of a scaled solar panel. Experimental data are used not only to verify the device expected functioning, but also to tune the parameters in the OPSA FE model, which can be finally integrated in a planar satellite dynamics simulator to evaluate the AVC system efficiency when performing attitude manoeuvres.

Master-slave synchronous control method for attenuating dual mode electromechanical transmission system torsional vibration

The high-power electromechanical transmission (EMT) system is a typical dual-mode hybrid power transmission system. The torque fluctuation of internal combustion engine causes serious shock and vibration problems of EMT. Suppressing torsional vibration based on high dynamic motor torque regulation is an important way to improve the working life and stability of EMT system. First, a lbased on the lumped parameter linear dynamic model,the torsional vibration characteristics are analyzed. Second, a fluctuating speed estimation method is proposed based on the uniformly accelerated motion model and linear regression, and a digital high pass filter is designed. Then, a master-slave coupling active torsional vibration control strategy is proposed, and a PD control algorithm based on speed feedback is designed. The variation rules of control parameters is analyzed. Finally, the control effect is verified by experiments. The results show that the lever coefficient K ab and differential coefficient K d of master-slave control can change the natural frequency of torsional vibration of the system, thus significantly changing the vibration response of the system. Selecting appropriate control parameters can achieve peak clipping of EMT torsional resonance.

Control of vibration in a plate using active acoustic black holes

Acoustic black holes (ABHs) are structural features that can be embedded into plates to provide effective structural damping. However, the performance of an embedded ABH is limited by its size, which determines the ABH cut-on frequency. It is not always practicable to increase the size of an ABH to reduce its cut-on frequency, however, previous work has shown that active vibration control can instead be used to enhance the low frequency performance of an ABH beam termination. This paper presents an investigation into the potential performance benefits that can be achieved by implementing active control into an array of ABHs embedded in a plate, realising an array of active ABHs (AABHs). The potential performance advantage is investigated here through experimental investigations, where different configurations of passive and active control treatments are applied to both a plate with embedded ABHs and a constant thickness plate. The smart structures utilise piezoelectric patches to realise the control actuation and employ an active feedforward multichannel vibration control strategy that aims to minimise the structural response monitored by an array of accelerometers. The performance of each plate configuration is evaluated in terms of the attenuation in the structural response and the energy, or control effort required. The presented experimental results demonstrate that, compared to the constant thickness plate configuration, the AABHs provide considerable passive damping above the ABH cut-on frequency and significantly reduce the required control effort.

On Active Vibration Absorption in Motion Control of a Quadrotor UAV

Conventional dynamic vibration absorbers are physical control devices designed to be coupled to flexible mechanical structures to be protected against undesirable forced vibrations. In this article, an approach to extend the capabilities of forced vibration suppression of the dynamic vibration absorbers into desired motion trajectory tracking control algorithms for a four-rotor unmanned aerial vehicle (UAV) is introduced. Nevertheless, additional physical control devices for mechanical vibration absorption are unnecessary in the proposed motion profile reference tracking control design perspective. A new dynamic control design approach for efficient tracking of desired motion profiles as well as for simultaneous active harmonic vibration absorption for a quadrotor helicopter is then proposed. In contrast to other control design methods, the presented motion tracking control scheme is based on the synthesis of multiple virtual (nonphysical) dynamic vibration absorbers. The mathematical structure of these physical mechanical devices, known as dynamic vibration absorbers, is properly exploited and extended for control synthesis for underactuated multiple-input multiple-output four-rotor nonlinear aerial dynamic systems. In this fashion, additional capabilities of active suppression of vibrating forces and torques can be achieved in specified motion directions on four-rotor helicopters. Moreover, since the dynamic vibration absorbers are designed to be virtual, these can be directly tuned for diverse operating conditions. In the present study, it is thus demonstrated that the mathematical structure of physical mechanical vibration absorbers can be extended for the design of active vibration control schemes for desired motion trajectory tracking tasks on four-rotor aerial vehicles subjected to adverse harmonic disturbances. The effectiveness of the presented novel design perspective of virtual dynamic vibration absorption schemes is proved by analytical and numerical results. Several operating case studies to stress the advantages to extend the undesirable vibration attenuation capabilities of the dynamic vibration absorbers into trajectory tracking control algorithms for nonlinear four-rotor helicopter systems are presented.

Active Vibration Control of Truss Structures for Large Space Telescopes Based on Cable Actuators

The membrane diffraction is a new imaging method for space telescopes. It makes a hot research topic in space telescope technology with lots of advantages, such as light weight, easy foldability and high optical imaging accuracy. The active vibration control of the truss structure of a kind of membrane diffraction space telescope was investigated, and an active vibration control strategy was proposed based on cable actuators. Firstly, the dynamic model for the telescope truss structure was established. Then the particle swarm optimization algorithm was used to study the arrangement optimization of cable actuators. The active control law for the structure vibration was designed with the classical linear quadratic regulator method. Finally, the numerical simulation results verify the effectiveness of the proposed method. In the numerical simulations, the relationship between the number of cable actuators and the required time for the structure to regain stability was studied in detail.

Active vibration control for GyroWheel based on sliding mode observer and adaptive feedforward compensator

This article proposes an active vibration control method for the GyroWheel to ensure the attitude stability precision of the spacecraft. The method includes sliding mode disturbance observer and adaptive feedforward compensator. First, considering the disturbance torque caused by rotor imbalance, the dynamic equation adopting complex coefficients is derived with synchronous disturbances. To reduce the influence of model parameter perturbation, a finite time sliding mode observer is designed to estimate the rotor imbalance owing to its robustness. An integrator for the switching term is introduced in the sliding manifold, which attenuates the chattering phenomenon. Then, the observed unbalanced torque is utilized to generate the reference compensation tilting angle, which is fedforward to the command value to offset the synchronous frequency current. A variable step size seeking algorithm is adopted to tune the feedforward compensator gain adaptively. Finally, both numerical simulations and experiments have verified the effectiveness of the active vibration control scheme, achieving clean vibration torque.

Adaptive Deterministic Vibration Control of a Piezo-Actuated Active–Passive Isolation Structure

With the improvement of the performance of optical equipment carried by on-orbit spacecraft, the requirements of vibration isolation are increasing. Passive isolation platforms are widely used, but the ability to suppress the low-frequency deterministic vibration disturbance is limited, especially near the system’s natural frequency. Therefore, an active vibration control strategy is proposed to improve passive isolation performance. In this paper, a Youla parameterized adaptive active vibration control system is introduced to improve the isolation performance of a piezo-actuated active–passive isolation structure. A linear quadratic Gaussian (LQG) central controller is first designed to shape the band-limited local loop of the closed-loop system. Then, the central controller is augmented into a Youla parameterized adaptive regulator with the recursive least square adaptive algorithm, and the Youla parameters (Q parameters) can be adjusted online to the desired value to suppress the unknown and time-varying multifrequency deterministic vibration disturbance. In the experiment, the residual vibration with respect to the combination of multiple frequencies is effectively suppressed by more than 20 dB on average, and a quick response time of less than 0.3 s is achieved when the deterministic residual vibration changes suddenly over time. The experimental results illustrate that the proposed adaptive active vibration control system can effectively suppress the low-frequency deterministic residual vibration.

Acoustic analysis of an actively controlled pipe subject to vortex induced vibration

Pipe-like structures are utilised in a wide variety of engineering applications, which must often consider the impact of noise and vibration. This paper presents a numerical study into the Vortex Induced Vibration (VIV) of a flexible pipe in laminar flow and the resulting acoustic radiation, and explores the potential of an active vibration control strategy. The VIV is solved using a commercial CFD code, coupled with a finite element model (FEM) to obtain the pipe displacement. The hydrodynamic noise is solved using the FW-H equation based on the acoustic analogy and the vibrational noise is calculated by an acoustic FEM in the time-domain. Without control, when the vortex shedding frequency is approximately equal to the first structural natural frequency of the pipe, large amplitude vibration is induced. The fluid-pipe interaction causes hydrodynamic noise and the vibration of the pipe generates significant vibroacoustic noise. The simulations show that when the first mode of the pipe is well excited, the vibroacoustic noise dominates the sound radiation. A velocity feedback controller is then utilised to control the VIV of the pipe, which reduces both the vibrational and hydrodynamic noise, with the latter reduced to about the same level as a rigid stationary pipe.

Active vibration control of slewing drives with gear backlash

Geared transmissions with high reduction ratios are widely utilized in drive technology. Common to these drives is the occurrence of considerable gear backlash. If operating scenarios with repeated reversals of the rotational direction or changing load directions occur, the backlash will be traversed. To overcome the gear play, rotation angles of several hundred degrees can be required at the motor. As a result, unwanted vibrations can occur and high dynamic loads may arise. It is shown that an active vibration control strategy based on full state feedback (LQG) allows to reduce both the dynamic overload and the time for reversing the drive. The model-based design approach relies on two angular measurements only. Multibody system simulations of an exemplary drivetrain are used to verify the possible improvements.