Active Vibration Isolation System Research Articles

Effect of inertia variations for active vibration isolation systems

Microvibrations may affect the quality and yield of products in precision processes. Therefore, vibration control is essential for minimizing position errors and improving the quality of production. Conventional active vibration isolation systems (AVISs) do not consider the effect of inertia variation, such as the movement of the stage and manipulator, on the system. Variations in inertia are associated with rotational motion, and they require a change in the modeling of an AVIS. Owing to this change, the system may not be optimal and may become unstable because the gain value is close to the critical point of the system. This results in insufficient performance. To overcome these issues, in this study, active vibration isolation was evaluated with the aim of actively controlling an AVIS while considering the effect of inertia variation. The system used in this study consists of an adaptive linear quadratic Gaussian (LQG) controller with six degrees of freedom. The inertia of the entire system changes based on the position of a stage mover. This variation in inertia alters the model of the system. The model is updated using the LQG controller, and the performance of the controller is evaluated. The LQG controller is used to evaluate the followability and transmissibility of the AVIS. The feedback loop is analyzed using Nyquist plots to determine the correlation between inertia variation and robustness. As a result, the phase margin decreases to 40°or lower as the rate of inertia variation increases. When the model is updated, the Nyquist's path is included in the unit circle. The correlation between inertia variation and performance is analyzed using Bode plots. The correlation shows a difference of approximately 10 dB depending on whether the model is updated.

A Simple Frequency Range Selector to Reduce the Unstable Behavior of Active Vibration Isolation

Abstract In an active vibration isolation system using velocity feedback, the phase–lead due to high-pass filter and the phase–lag due to time delay limit the controller gain. This paper extends and applies a simple frequency range selector to increase the critical control gain. The selector uses the isolated mass's acceleration, velocity, and displacement and is tuned by two knobs. Our proposed approach has simple static switching law, suppresses both low and high frequency control, and does not add additional phase–lead or phase–lag. A simple expression of the effective gain is presented to give insight into the influence of two tuning knobs. Numerical simulations and a simple experiment are performed to illustrate the controller's effectiveness under harmonic and random disturbances.

Active Vibration Isolation of a Diesel Generator in a Small Marine Vessel: An Experimental Study

An active vibration isolation system is retrofitted to a diesel generator set in a tugboat to determine the effectiveness of such a system in a realistic practical environment. The system consists of six bespoke inertial actuators chosen to make minimal modifications to the machinery arrangement, and a DSP-based controller. Six accelerometers are collocated with the actuators on the top of six isolators to act as error sensors, and six accelerometers are placed below the isolators to give a measure of the global vibration of the ships structure below the generator set. A hydrophone is also placed in the water to give an indication of the underwater noise due to the generator. The control strategy employed is six-input and six-output decentralized adaptive feedforward control with the reference signal being derived from the signal from an optical tachometer on shaft between the engine and the generator. To suppress the vibration at all the dominant forcing frequencies, an electrical circuit generated the half engine orders required from the measured reference signal. The experimental results show that the combination of the active control system and the passive isolators is effective in reducing the global vibration and the acoustic pressure at the hydrophone position.

Active vibration isolation system based on the LADRC algorithm for atom interferometry

A new, to the best of our knowledge, method based on the linear active disturbance rejection control (LADRC) algorithm is proposed to design and build a vertical vibration isolator below ${0.1}\;{\rm Hz}$0.1Hz for cold-atom interferometry. This system combines the control system that is used to process and to reduce feedback vibrations measured by a seismometer and a voice coil that is used to cancel the motion of a commercial passive vibration isolation platform. When the feedback is on, the vertical vibration is reduced by an additional factor of up to 1000 from 0.1 to ${5}\;{\rm Hz}$5Hz, while the system has a steady oscillation with a natural period of 66 s. The experimental results show that the LADRC is an effective control algorithm for this application and performs better than the classic lag compensation filters in our case. In addition, there are fewer parameters to adjust in this method, and we only need to tune the feedback gain of the system state error for its application.

Active stabilization of unmanned aerial vehicle imaging platform

The advancement in technology has seen a rapid increase in the use of unmanned aerial vehicles for various applications. These unmanned aerial vehicles are often equipped with the imaging platform like a camera. During the unmanned aerial vehicle flight, the camera is subjected to vibrations which hamper the quality of the captured images/videos. The high-frequency vibrations from the unmanned aerial vehicle are transmitted to the camera. Conventionally, passive rubber mounts are used to isolate the camera from the drone vibrations. The passive mounts are able to provide reduction in response near the resonance. However, this comes at the cost of amplification of response at the higher frequency. This article proposes an active vibration isolation system which exhibits improved performance at the higher frequencies than the conventional system. The active isolation system consists of a contact-less voice coil actuator supported by four springs. Experiments are carried out to study the effect of vibrations on the quality of images captured. The characterization of drone vibrations is also carried out by recording the acceleration during different flight modes. The performance of the proposed isolation system is experimentally validated on a real drone camera subjected to the recorded drone acceleration spectrum. The isolation system is found to perform better than the conventional rubber mounts and is able to reduce the vibrations to a factor of one-fourth. It can be effectively used to improve the image acquisition quality of the unmanned aerial vehicles.

Modeling identification and control of a 6-DOF active vibration isolation system driving by voice coil motors with a Halbach array magnet

The sheet current model considering the end effects is applied to design a six-degree-of-freedom (6-DOF) active vibration isolation system (AVIS) driving by the voice coil motors (VCMs). Compared with the charge model, the sheet current method represents higher calculation efficiency. Then, the hybrid functions (HFs) are employed to identify the multi-input and multi-output (MIMO) AVIS, and the identification parameters are used to design the controller. To promote the control performance, the composite nonlinear feedback (CNF) controller is designed based on the identification parameters. Consequently, the simulations and experiments are carried out, compared with PID controller, the CNF controller shows quicker response and smaller overshoot, i.e., the CNF controller achieves the dynamic damping ratio during the control. Thus, the experimental results demonstrate the better performance of the CNF controller.

The active system of vibration isolation with electrodynamic actuator

The work is devoted to the study of the possibility of developing an active vibration isolation system in which in order to compensate for the dynamic forces on the hull arising due to the oscillations of an elastically suspended vibroactive mass, the effect of inertial forces in antiphase is used. The vibroactive force compensator is an electrodynamic actuator. It is mounted on the hull close to vibroactive mass supports and produce an inertial force by controlling oscillations of the moving mass, which compensates the force on the hull from the vibroactive mass.

Simulation analysis of control system for six degrees of freedom damping platform based on MATLAB

On the basis of relevant mathematical theory inference and the observability analysis of sensor arrangement and the controllability analysis of actuator arrangement, the simplified model of the six-degree-of-freedom air spring active vibration isolation system is established. Considering the structure of the air spring damping platform and the environment interference around the vibration isolation platform, we use the simulation software named MATLAB to establish three control models: PID control, Fuzzy control and Fuzzy PID control. The simulation analysis results show that the Fuzzy PID control consequent is obviously benefit to the damping platform, in addition, the composite feedback can also greatly promote the control consequent.

Fractional-order robust model reference adaptive control of piezo-actuated active vibration isolation systems using output feedback and multi-objective optimization algorithm

Improving the control performance of active vibration isolation systems is crucial to provide an ultra-quiet environment for precision instruments. This paper presents a new fractional-order robust model reference adaptive controller for the piezo-actuated active vibration isolation systems with a relative-degree-one model. One advantage of the proposed controller lies in that its controller parameters are adjusted online by fractional proportional–integral-type adaptive laws, which not only speeds up the convergence of the closed-loop system, but also improves the control energy efficiency. Moreover, the proposed controller only uses the measurable input and output of the plant as feedback signals, which is convenient for controller implementation. The stability of the closed-loop system is proved based on the Lyapunov theory in detail. The optimal values of the fractional order and adaptive gains for adaptive laws are determined using the multi-objective genetic algorithm through off-line simulation. Comparative experiments on the piezo-actuated active vibration isolation systems are conducted to verify the effectiveness of the proposed controller. Results show that the proposed controller achieves satisfactory isolation performance in a wider frequency band of 20–500 Hz, and simultaneously reduces the control effort compared with the traditional MRAC methods.

Design and experimental validation of an annular dielectric elastomer actuator for active vibration isolation

Abstract This paper proposes annular dielectric elastomer actuators (ADEAs) for active vibration isolation. A theoretical model is developed to characterize the actuator and parametrized based on experimental data. The parametric dependence of the natural frequency of the ADEA on the actuator geometry, applied voltage, and the pre-stretch of the elastomer is analyzed. The electromechanical behavior of the ADEA is also characterized experimentally and estimated by finite-impulse-response (FIR) based adaptive filter. Vibration control with the ADEA as the active vibration isolator is implemented by employing the filtered-x least-mean-square (Fx-LMS) algorithm due to incorporating the effect of the secondary path function. The vibration isolation ratios at the 7 and 11 Hz harmonics with the amplitudes of 320 μm and 330 μm are 10.53 and 11.81 dB, respectively. For the isolated mass under the 9 Hz sinusoidal disturbance with peak-to-peak amplitude of 1400 μm, vibration attenuation of 10.74 dB is achieved. The results show that ADEAs have the potential for active vibration isolation systems even with large amplitude disturbance. It provides guidelines for the actuator design and promote the dielectric elastomers (DEs) for engineering applications.

An active actuator based on giant magnetostrictive composite pendulum for vibration isolation

This paper proposes an active actuator based on giant magnetostrictive composite pendulum for vibration isolation, laying the foundation for vertical micro-vibration isolation. The performance of a single-stage pendulum vibration isolation system can be improved by increasing the pendulum length, along with the influence of the environment on the system increases. In precise experiments, effective isolation of vertical micro-vibration improves the accuracy of the experiments. Interference caused by micro-vibration can be attenuated by designed magnetostrictive actuators. Then, a suspension actuator consists of a composite pendulum and a driving device is designed. The composite pendulum is composed of a quartz fiber coated with a giant magnetostrictive material (GMM). The GMM can achieve the desired small strain in a designed magnetic field. GMM is applied on a quartz fiber to form a composite pendulum. Therefore, low-frequency active vibration isolation of single pendulum is realized. Compared with the passive vertical vibration isolation system, the system gets better vibration isolation and anti-interference ability. Compared with the traditional active vertical vibration isolation system, it has the advantages of system simplification, high integration and high sensitivity.

Dynamic Blocks and Efficacy Bounds of Active Vibration Isolation Systems

Miscellaneous active vibration isolation systems designed for laboratory (workshop), transport, and space applications with the decoupled control of six vibration modes of the bearing plate are studied. Using the electric circuit method, a compact mathematical description of the dynamic behavior of individual mechanical and electrical units and of the control of active vibration isolators is obtained. It is shown how, given the basic parameters of a vibration isolation system (the active frequency range and maximal vibration attenuation factor, which are together called efficacy bounds), the parameters of the dynamic blocks of the device and its design characteristics can be determined. The factors that limit the active frequency range and the maximal vibration attenuation factor of vibration isolators are analyzed.

Filtered-error recursive least squares optimization for disturbance feedforward control in active vibration isolation

This paper addresses the filtered-error recursive least squares (FeRLS) algorithm for disturbance feedforward control in active vibration isolation systems. The controller structure consists of a generalized finite-impulse response (FIR) filter to include a set of pre-determined poles and self-tuning zeros. In addition, residual noise shaping is included to add frequency weighting and improve robustness. Compared to existing filtered-error least mean squares (FeLMS) algorithms, two major improvements are distinguished. First, faster convergence is obtained without the necessity of pre-whitening and an orthonormal basis. Second, the parameters are estimated without steady-state variance. These improvements are demonstrated using simulation studies, which show the potential of the algorithm in active vibration isolators.

Design and Control of a Dual-Stage Actuation Active Vibration Isolation System

Active vibration isolation system is used in various fields to reduce the vibrations transmitted. In this paper, a novel dual-stage actuator is proposed, which combines a voice coil motor and a piezoelectric actuator. The proposed dual-stage actuator maintains the advantages, in terms of the long stroke, the high precision, and the wide band. The dual-stage actuation active vibration isolation system (DSA-AVIS) with the proposed dual-stage actuator is initially modeled. The characteristic of the DSA-AVIS is subsequently analyzed. H ∞ controller is finally designed to consider the vibration isolation performance and the output range of the actuators. The experimental results indicate that the closed-loop transmissibility of the DSA-AVIS is less than -18 dB from 0 to 100 Hertz.

Active vibration suppression of a beam using piezoeffect

Operation of structures and equipment in dynamic conditions led to the problems of vibration isolation and vibration suppression. For vibration isolation and vibration suppression passive, active systems and their combinations are used. Passive vibration isolation usually consists in the fact that the protected object relies on extremely dimensional springs and vibration isolators. Vibration isolation systems containing only passive elastic and damping elements are called passive. Active vibration isolation and vibration damping systems use external energy sources. These are pneumatic, hydropneumatic and hydromechanical devices. Recently, electro-elastic and magneto-elastic systems [1], [2] began to be used for vibration isolation and active vibration suppression. As a rule, the analysis of the work of such systems consists in the development of an experimental layout and a schematic diagram. In this paper, a mathematically based model is used to solve the problem in question. The calculations are performed and the results are presented in the form of graphs.

A mobile three-dimensional active vibration isolator and its application to cold atom interferometry

Vibration noise has an influence on the sensitivity and stability for many precision instruments, especially for atom interferometers. In this paper, a mobile three-dimensional active vibration isolation system is established for portable atom interferometer that is effectively isolated from the ground vibration, thereby improving the sensitivity of the portable atom interferometer, and can be deployed and recovered to working state rapidly. With the home-developed integrated feedback algorithm, this system achieves a good vibration suppression in a wide frequency range in three directions. It suppresses the ground vibration by three orders of magnitude in the vertical direction, and one order of magnitude in the horizontal direction. In a frequency range less than 10 Hz which the atom interferometer is sensitive to, the vibration noise is suppressed to 4.8 × 10<sup>–9</sup> m/s<sup>2</sup>/Hz<sup>1/2</sup> in the vertical direction and to 2.7 × 10<sup>–7</sup> m/s<sup>2</sup>/Hz<sup>1/2</sup> in the horizontal direction. The influence of vibration noise on the sensitivity of the atom interferometer reaches to 2 μGal/Hz<sup>1/2</sup>, which is reduced by two orders of magnitude compared with the result without our system.

Flight Test Results of the Microgravity Active Vibration Isolation System in China\u2019s Tianzhou-1 Mission

The Microgravity Active vibration Isolation System (MAIS) was operated on China’s first cargo-spacecraft Tianzhou-1, which was launched on April 20, 2017 and re-entered atmosphere and burned on September 22, 2017. In this article, the flight test results of MAIS is presented. The results are evaluated in terms of the performances of microgravity acceleration and vibration attenuation under control. Firstly, the system configuration of MAIS on Tianzhou-1 is described, including operating modes, acceleration measurement, and control schemes. Then, two control performance indices, namely, microgravity acceleration and vibration attenuation, are introduced, followed by their definitions and methods of calculation. Subsequently, the flight test results of MAIS are described in detail. The microgravity acceleration under a PID (Proportional-Integral-Derivative) controller is at the order of 10−7 – 10−6 m/s2 in the frequency band of 0.01–10 Hz, and the performance of vibration attenuation reaches −20 dB at frequencies higher than 0.2 Hz. The flight test results show that MAIS in the TZ-1 mission performed well and achieved the expected control performance of microgravity vibration isolation in orbit. Finally, some experiences and lessons learned are summarized, which can serve as a benchmark reference to develop MAIS-like devices on board China’s Space Station in the near future.

Design and control of active vibration isolation system with an active dynamic vibration absorber operating as accelerometer

This paper exhibits the development of a vibration isolation system using an active dynamic vibration absorber (ADVA) as an accelerometer in a low-frequency range; whereas, it operates as a vibration control device in a high-frequency range. The control signal of the ADVA gives an information of the low-frequency acceleration. At the same time, in the active vibration isolation system, an air spring is employed as a low-frequency control device and an inexpensive MEMS-type accelerometer is used to measure the acceleration of the vibration in a high-frequency range. The sensor fusion technique is applied to integrate the output of the MEMS-type accelerometer and the acceleration estimated from the ADVA. The motions of the vibration isolation table and the absorber mass of the ADVA are controlled by PID control. The integrated acceleration by the sensor fusion is transmitted through a low-pass filter to the air spring and through a high-pass filter into the ADVA to attain additional acceleration and velocity feedback to the PID controls. Several experimentations and observations are conducted to measure the transmissibility and compliance. The experimental and simulation results demonstrate that the performance and operative precision of the developed active vibration isolation system are improved by the additional absolute acceleration and velocity feedbacks in terms of compliance as well as transmissibility characteristics.

Disturbance feedforward control for active vibration isolation systems with internal isolator dynamics

This paper presents a disturbance feedforward control strategy for active vibration isolation systems that have internal isolator dynamics. The structure of the feedforward controller follows from modeling, but to achieve robust performance the tuning of the controller parameters will be based on measurement data. More specifically, the controller poles, which correspond to internal isolator dynamics, are obtained offline from system identification experiments, while the controller zeros are obtained from online self-tuning using measured sampled-data systems. Self-tuning is used to reduce parameter uncertainty when having too limited identification possibilities, and to account automatically for the effect of noise amplification. Measurement results obtained from an industrial vibration isolation system show that residual vibrations are largely reduced up to the level of output noise limitations.

Control performance simulation and tests for Microgravity Active vibration Isolation System onboard the Tianzhou-1 cargo spacecraft

The Microgravity Active vibration Isolation System (MAIS), which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20, 2017, aims to provide high-level microgravity at an order of 10-5–10-6g for specific scientific experiments. MAIS is mainly composed of a stator and a floater, and payloads are mounted on the floater. Sensing relative motion with respect to the stator fixed on the spacecraft, the floater is isolated from vibration on the stator via control forces and torques generated by electromagnetic actuators. This isolation results in a high-level microgravity environment. Before MAIS was launched into space, its control performance had been simulated on computers and tested by air-bearing platform levitation and aircraft parabolic flight. This article first presents an overview of the MAIS’s hardware system, particularly system structure, measurement sensors, and control actuators. Its system dynamics, state estimation, and control laws are then discussed, followed by the results of computer simulation and engineering tests, including the test of the six-degree-of-freedom motion by aircraft parabolic flight. Simulation and test results verify the accuracy of the control strategy design, effectiveness of the control algorithms, and performance of the entire control system, paving the way for operation of MAIS in space. This article also presents the steps recommended for the control performance simulation and tests of MAIS-like devices. These devices are expected to be used on China’s Space Station for various scientific experiments that require a high-level microgravity environment.