High-performance Vibration Isolation Research Articles

Low-frequency vibration isolation via an elastic origami-inspired structure

This paper presents a new elastic origami-inspired structure with quasi-zero-stiffness (QZS) characteristics to provide effective low-frequency vibration isolation performance. The geometric structure of the origami mechanism is first introduced, followed by the establishment of its mechanical model through the integration of elastic joints with compression springs. The derived strong nonlinear stiffness characteristics of the elastic origami mechanism are conducive to exploring a QZS isolator with high performance. Then by using the multiscale method, the dynamic behavior of the origami-inspired isolator is obtained, and the parameter influencing investigations validate that the proposed vibration isolation system has strong design flexibility and superior vibration suppression capability. An experimental prototype was fabricated and a series of vibration testing experiments under different working conditions were carried out. The experimental results demonstrated the effectiveness of the established theoretical model. Furthermore, the comparison with typical nonlinear passive isolators verified the advantages of the developed origami-inspired vibration isolation system. This work has the potential to advance the practical applications of origami-based mechanisms and also provides a new technical candidate for high-performance vibration isolation systems.

Ultra-low frequency active vibration isolation in high precision equipment with electromagnetic suspension: Analysis and experiment

High performance vibration isolation requirement in the ultra-low frequency band for high precision equipment becomes more and more stringent. An active vibration isolation method is investigated to broaden the frequency band of isolation and improve the performance, in which an electromagnetic suspension is adopted to provide a static lifting force and an active control force. Naturally, the suspension is accompanied by a controllable negative stiffness. Two factors that might cause instability of the suspension system, i.e., the bias current and the base disturbance, are analyzed to give the stable region. The matching relationship between the currents in the upper and lower coils, and the mapping rules among the current, relative displacement, force and stiffness are discussed, respectively. The maximum base disturbance that the system can withstand is analyzed. On the basis of the theoretical analysis, the active position stabilization and vibration control methods are built and the performance is evaluated. Furthermore, experiments were conducted to verify the effectiveness of the active vibration isolation method. Numerical and experimental results demonstrate that the electromagnetic suspension is able to improve the vibration isolation performance in the ultra-low frequency range, where the transmissibility is below 0 dB in the entire frequency band and the initial vibration isolation frequency is less than 1Hz.

Filtered-error RLS for self-tuning disturbance feedforward control with application to a multi-axis vibration isolator

High performance vibration isolation can be realized by disturbance feedforward control with a self-tuning generalized FIR filter and residual noise shaping. For this application, filtered-error recursive least squares (FeRLS) self-tuning is proposed in a multi-input multi-output context. In comparison to filtered-error least mean squares (FeLMS), FeRLS achieves faster and more uniform parameter convergence without the need of pre-whitening. Efficient implementation is realized by exploiting sparsity in the involved matrices. Feasibility of implementation is demonstrated on a multi-axis hard-mount vibration isolation setup. Experimental results show the better parameter convergence and the ability to track changes in the floor vibration spectrum. A reduction of the transmissibility of floor vibrations up to 40 dB in the frequency range of interest is obtained, reducing vibration power by 90–94% in the 1–300 Hz frequency band in multiple directions.

Desired Compensation Adaptive Robust Control of an Active Vibration Isolation System

Active vibration isolation system (AVIS) has attracted increasing attention of researchers in precision engineering. In this paper, a desired compensation adaptive robust controller (DCARC) is proposed for an AVIS developed in our laboratory. The AVIS composed of one platform and three active isolators is required to achieve high-performance vibration isolation as well as low trajectory tracking error for positioning. The vertical three degrees of freedom (DOFs) and horizontal three DOFs are decoupled by the joint bearing of the isolators. The dynamic model of the system is built and is simplified to three single-input-single-output (SISO) systems. The DCARC control scheme is then proposed, which contains a deterministic robust control (DRC) term and an adaptive control (AC) term. The high performance in vibration isolation and positioning can be subsequently achieved, even the actual load and system stiffness are unknown and there exists direct bounded disturbance on the platform. The AC term is designed to estimate the unknown parameters of the system. The DRC term can improve the robustness of the system, which is used to reject the direct disturbance and the parameter estimation error. Furthermore, the computing time and the influence of the measurement noise can be reduced effectively by reason of desired compensation. The numerical simulation and comparative experiments are carried out under the conditions of using DCARC, DRC, and AC controllers. The experimental results validate that the proposed DCARC control strategy outperforms other control method and possesses both high-performance vibration isolation and low tracking error.

Two-sided damping constraint control strategy for high-performance vibration isolation and end-stop impact protection

In this paper, a two-sided damping constraint control strategy is proposed to improve the performance of the quasi-zero stiffness isolator. The new control policy is achieved through switching the damping of isolator between the soft and hard modes that depend on a preset value of the relative displacement (PRD). This control approach can largely lower the isolation frequency while enhancing the effectiveness of isolation in high frequencies and preventing the severity of end-stop impacts. To realize such control objective, two key issues are solved including the suppressing of period-3 solutions that coexist with the desired period-1 orbits and the optimization of PRDs based upon the analysis of two-parameter bifurcations and basins of attraction. Finally, the capability of the proposed system in end-stop impact protection is studied, which shows that it can successfully prevent the impact and quickly stabilize the large-amplitude response into the ideal steady-state motion.

State observers and Kalman filtering for high performance vibration isolation systems

There is a strong scientific case for the study of gravitational waves at or below the lower end of current detection bands. To take advantage of this scientific benefit, future generations of ground based gravitational wave detectors will need to expand the limit of their detection bands towards lower frequencies. Seismic motion presents a major challenge at these frequencies and vibration isolation systems will play a crucial role in achieving the desired low-frequency sensitivity. A compact vibration isolation system designed to isolate in-vacuum optical benches for Advanced Virgo will be introduced and measurements on this system are used to present its performance. All high performance isolation systems employ an active feedback control system to reduce the residual motion of their suspended payloads. The development of novel control schemes is needed to improve the performance beyond what is currently feasible. Here, we present a multi-channel feedback approach that is novel to the field. It utilizes a linear quadratic regulator in combination with a Kalman state observer and is shown to provide effective suppression of residual motion of the suspended payload. The application of state observer based feedback control for vibration isolation will be demonstrated with measurement results from the Advanced Virgo optical bench suspension system.

Influence of flexible solar arrays on vibration isolation platform of control moment gyroscopes

A high-performance vibration isolation platform (VIP) has been developed for a cluster of control moment gyroscopes (CMGs). CMGs have long been used for satellite attitude control. In this paper, the influence of flexible solar arrays on a passive multi-strut VIP of CMGs for a satellite is analyzed. The reasonable parameters design of flexible solar arrays is discussed. Firstly, the dynamic model of the integrated satellite with flexible solar arrays, the VIP and CMGs is conducted by Newton-Euler method. Then based on reasonable assumptions, the transmissibility matrix of the VIP is derived. Secondly, the influences of the flexible solar arrays on both the performance of the VIP and the stability of closed-loop control systems are analyzed in detail. The parameter design limitation of these solar arrays is discussed. At last, by selecting reasonable parameters for both the VIP and flexible solar arrays, the attitude stabilization performance with vibration isolation system is predicted via simulation.

Three-Dimensional Analytical Calculation of the Torque Between Permanent Magnets in Magnetic Bearings

In the high-precision industry, accurate vibration isolation and magnetic levitation are extremely important. As a result, high-performance vibration isolation and magnetic bearings based on permanent magnets are increasingly considered. This paper proposes improved analytical expressions for the torque on cuboidal permanent magnets applied to a magnetic bearing. These novel expressions are valid for any relative magnet position, especially when surfaces of the different magnets are in the same plane. Further, the torque can be obtained with respect to any reference point. Although these equations seem rather complicated, they enable an extremely fast and accurate calculation of the torque on a permanent magnet in the presence of a magnetic field of another permanent magnet. These properties enable a fast design and optimization process of such bearings using fully analytical expressions.

An anti-windup strategy for active vibration isolation systems

An anti-windup augmentation technique for active vibration isolation systems is considered in this paper and shown to lead to high-performance vibration isolation through simulations and experiments. First, the anti-windup construction is described and desirable properties of the augmented closed-loop system are illustrated. Then, the anti-windup technique is tested on a simulation example and finally shown to perform excellently on a commercial vibration isolation device: Newport Corporation's Elite 3 TM active vibration isolation system which has been patented and is now commercialized with this architecture. Both simulation and experimental results confirm the effectiveness of the anti-windup scheme.

Radiation pressure actuation of test masses

In this paper, we investigate the use of radiation pressure force as test mass actuation for laser interferometer gravitational wave detectors. It is shown that it is viable to provide radiation pressure control on test masses for frequencies above ∼0.2 Hz in high performance vibration isolation systems. A very low mass, low frequency resonator has been used to verify that radiation pressure force is not corrupted by other forces such as due to radiometer effects.

Australia's Role in Gravitational Wave Detection

AbstractAn enormous effort is underway worldwide to attempt to detect gravitational waves. If successful, this will open a new frontier in astronomy. An essential portion of this effort is being carried out in Australia by the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA), with research teams working at the Australia National University, University of Western Australia, and University of Adelaide involving scientists and students representing many more institutions and nations. ACIGA is developing ultrastable high-power continuous-wave lasers for the next generation interferometric gravity wave detectors; researching the problems associated with high optical power in resonant cavities; opening frontiers in advanced interferometry configurations, quantum optics, and signal extraction; and is the world's leader in high-performance vibration isolation and suspension design. ACIGA has also been active in theoretical research and modelling of potential astronomical gravitational wave sources, and in developing data analysis detection algorithms. ACIGA has opened a research facility north of Perth, Western Australia, which will be the culmination of these efforts. This paper briefly reviews ACIGA's research activities and the prospects for gravitational wave astronomy in the southern hemisphere.