Separated active vibration isolation technology for ultra-quiet scientific satellite

A compact stable vibration isolation system is designed to isolate vertical ground motions. Active vibration isolation technology has made rapid development in recent years. At present, it is in the stage of laboratory verification and trial application. In the early stage of the research, the theoretical research on control algorithm, control strategy and actuator has gradually turned to the integrated system research. Based on the active vibration isolation bench system, the design, development, detection and evaluation of the active vibration control system are completed by using the model development mode, and a set of simulation platform is built to verify and evaluate the design process. Active vibration isolation structure consists of signal pick-up system, excitation and monitoring system, actuator, power amplifier and passive vibration isolation platform, forming an integrated active vibration isolation platform, namely active control object. Based on the second-order active disturbance rejection control algorithm, the simulation model and experimental model of the control system are researched and developed, and the rapid development of the controller is realized by using the active disturbance rejection control technology. Based on the passive vibration isolation bench system and control system, the active vibration control experiment is completed, which verifies the correctness and effectiveness of the developed controller. At the same time, the experimental engineering file package is established in the experiment to realize the centralized management of the control experiment.

Passive vibration isolation has the advantages of simple structure, high reliability, and strong ability to absorb high-frequency vibration. Active vibration isolation has wide application range, strong controllability, and good vibration suppression effect for specific frequency band. Active and passive integrated vibration isolation technology combines the characteristics of both and has obvious advantages in dealing with the complex vibration environment in modern engineering practice. In this work, piezoelectric stack actuator is selected as the active control output source and vulcanized butyl rubber is used as the passive vibration absorber. The dynamic model of the novel active and passive integrated isolator is established, then the effects of different parameters on its vibration transmission performance are studied. Furthermore, a typical two-degree-of-freedom vibration isolation system model is established. By comparing the change of vibration transmissibility under different feedback forms, the design of the feedforward–feedback composite controller is applied. Finally, a double-layer vibration isolation test platform is built to verify the vibration reduction capability of the active and passive integrated isolator. The experimental results show that both the passive vibration absorption and active vibration suppression functions of this novel vibration isolator are particularly effective.

In modern industries, high-speed machinery occupies a fundamental place. However, rotating machinery will inevitably produce a variety of structural noise and vibration. Generally, vibration isolation means can be divided into active vibration isolation and passive vibration isolation, among which the most representative are active magnetic bearings (AMBs) and vibration isolators, respectively. The combination of active magnetic bearings and vibration isolators is widely used in rotating machinery because of its excellent effect in vibration and noise reduction. This paper concentrates on the analysis of the vibration transmission mechanism of the active magnetic bearings coupled with the vibration isolators. A 30 kW prototype pump is taken as an example to help describe the research method. The model of the pump is first established. The stationary pump components and the rotor are respectively modeled through the finite element method and converted to substructure modal expression after low-order modal extraction. The bearing force is simplified to spring-dampers with equivalent stiffness and equivalent damping relating to the exciting frequency. The vibration isolators are simplified as three-dimensional spring-dampers. Based on the model, this paper then investigates the matching relation of the AMBs and the vibration isolators and proposes a dynamic vibration isolation design method for the rotor-AMBs-flexible support system. On the basis of the frequency-domain response of the original design, this design method gives the frequency-domain curves of the desired stiffness and damping of the suitable active vibration isolation, which can be used to guide the controller design of the AMBs and isolators selection. According to the design, we have done laboratory experiments on the prototype pump. The results show that the design method based on matching relation has good performance in vibration isolation.

Submarine acoustic stealth technology is very important for national defense constructions. vibration isolation technology is the key technology to realize submarine acoustic stealth. In this paper, the development of vibration isolation technologies in recent years is reviewed. The characteristics of several important active and passive vibration isolation technologies and vibration isolators are analyzed in detail. Besides, the latest research directions are discussed. Afterwards, the deficiencies of current intelligent vibration isolation technology and personal views on the development of intelligent vibration isolation technology are presented.

An ultra-low frequency vibrational noise isolation apparatus from external vibration can be a critical factor in many fields such as precision measurement, high-technology manufacturing, scientific instruments, and gravitational wave detection. To increase the accuracies of these experiments, well performed vibration isolation technology is required. Until recently the cold atom gravimeter has played a crucial role in measuring the acceleration due to gravity and earth gravity gradient. The vibration isolation is one of the key techniques in the cold atom gravimeter. To reduce the vibrational noise caused by the reflecting mirror of Raman beams in the cold atom gravimeter, a compact active low-frequency vibration isolation system based on sliding-mode robust control is designed and demonstrated. The sliding-mode robust control active vibration isolation method is used to solve the vibration problem of Raman mirror in the cold atomic gravimeter. The purpose of vibration control is that the controller enables the system to be at zero state as the system states are away from the equilibrium due to vibration disturbance. In this system, the mechanical setup is based on a commercial passive isolation platform which only plays a role at higher frequency. A sliding-mode robust control subsystem is used to process and feed back the vibration measured by a seismometer which can measure the velocity of the ground vibration. A voice coil actuator is used to control and cancel the motion of a passive vibration isolation platform. The simulation and experiment results of vibration isolation platform show, on the one hand, that the vibration noise power spectral density decreases by up to 99.9%, and that the phase noise in cold atom interferometry produced by vibration decreases by up to nearly 85.3% compared with the results of the passive vibration isolation platform. On the other hand, compared with the lead-lag control method, the vibration noise power spectral density decreases by up to 83.3% and the phase noise in cold atom interferometry produced by vibration decreases by nearly 40.2%. Therefore, the sliding-mode robust control has the advantages of less tuning parameters, strong anti-interference ability, and more obvious vibration isolating effect.

An atomic interference gravimeter (AIG) is of great value in underwater aided navigation, but one of the constraints on its accuracy is vibration noise. For this reason, technology must be developed for its vibration isolation. Up to now, three methods have mainly been employed to suppress the vibration noise of an AIG, including passive vibration isolation, active vibration isolation and vibration compensation. This paper presents a study on how vibration noise affects the measurement of an AIG, a review of the research findings regarding the reduction of its vibration, and the prospective development of vibration isolation technology for an AIG. Along with the development of small and movable AIGs, vibration isolation technology will be better adapted to the challenging environment and be strongly resistant to disturbance in the future.

Six-dimensional broadband vibration isolation is necessary for precision manufacturing, testing and assembly. A six-dimensional nearly zero-stiffness mechanism based on singular parallel mechanisms was proposed, which was taken as the main structure of the vibration isolator to reduce the system's natural frequency. Then control methods of configure maintenance and active vibration isolation were researched using feedback linearization and H ∞ robust control means. Finally six-dimensional active and passive vibration isolation control simulations were carried out respectively. The simulation results show that the vibration isolator has higher six-dimensional broadband vibration isolation capability and feasibility.

Active vibration isolation technology can overcome the defects of passive vibration isolation technology that the poor vibration isolation performance in low and resonant frequencies. Compared with other active vibration isolation technologies, magnetic suspension isolation technology has shown useful characteristics, such as wide response frequency range, fast response, high reliability and long-life. However, the control of MSVI is still one of the areas that require further investigation. This paper presents a Fuzzy Neural Networks(FNN) control algorithm for a magnetic suspension isolation vibration system, which is optimized by improved Genetic Algorithm(GA). The output force responses of the FNN and passive vibration isolation system under same excitation are simulated. The simulation results show that the fuzzy control system has much better performance in vibration isolation.

Floor vibrations and acoustic excitation may limit the performance of precision equipment, that is used for example to produce computer chips or to make images of very tiny structures. Therefore, it is common to mount a vibration isolator in the suspension of such equipment to isolate it from these vibration sources. Most often, a vibration isolator with a low suspension stiffness is used to limit the transmission of floor vibrations onto the suspended equipment. However, a low suspension stiffness introduces problems with leveling of the equipment and it increases its susceptibility to acoustic excitation. The objective of this thesis is to develop an alternative solution based on an active hard mount vibration isolator, which provides a much stiffer suspension such that the problems mentioned before can be circumvented. An active control system, that consists of sensors, actuators and a controller, is used to keep a low transmission of floor vibrations. An additional advantage is that the damping of internal modes of the equipment can be increased, such that its accuracy is improved. Several feedback control strategies for the active hard mount vibration isolator are presented. In both models and experiments it is shown that the best control strategy is using a combination of acceleration and force sensors. Formulas for adjusting the control parameters to obtain the desired vibration isolation performance have been derived. Furthermore, a demonstration setup of a six-axes active hard mount vibration isolator is developed. Unfortunately, due to some hardware problems, the usable control bandwidth is limited and the noise level of the sensors is too high, which results in a vibration isolation performance that is less than desired. Despite these problems, the transmission of floor vibrations is reduced by a factor 18, while simultaneously the suspension stiffness is about 100 times higher as compared to a vibration isolator with a low suspension stiffness. In addition, the damping of the internal modes is increased significantly. Further research should focus on improving the mechanical design of the active hard mount vibration isolator, such that the control bandwidth can be increased, and on using sensors with ultra-low noise levels.

During the flight, the airship load will be subject to various external disturbances, which will make the load camera unclear. To solve this problem, we have established a passive and vibration isolation platform, and used the characteristic model control method in the active vibration isolation system and the stable platform system. Firstly, the super magnetostrictive actuator is selected as the active control component to establish the active-passive integrated vibration isolation platform model. Then the internal relationship of the stable platform is analyzed, and the stepping motor control model of the stable platform is established. Finally, the characteristic modeling is carried out. The identified characteristic parameters are combined with the designed adaptive tracking controller, golden section controller and logic differential controller to control the active vibration isolator and the stable platform. The simulations show that the designed controller is effective.

An active vibration isolation equipment for isolating low frequency ground vibration of cold atom interferometry is demonstrated experimentally. This system combines the passive vibration isolator of negative stiffness elements and voice coil motor actuator can be used to counteract the ground vibration force measured by the seismometer. The processor with high integration and fast computation can be applied to the algorithm of active vibration isolation. Passive vibration isolation equipment can handle vibration above 10 Hz With the feedback path closed, the vertical vibration noise is greatly reduced by a factor of 100 from 0.1 to 10Hz With the help of active vibration isolation equipment, cold atom gravimeter can measure gravity precisely.

For absolute gravimeters, which play important roles in geophysics and geological exploration, an ultra-low-frequency vertical vibration isolator is necessary to achieve the required measurement precision. A novel active vibration isolator that uses a geometric anti-spring (GAS) structure has been proposed by our team at Tsinghua University previously, but its performance is mainly limited by the large-scale drift in the detection signal of the system. In this paper, after a brief theoretical introduction to the overall system, recent improvements in this novel vibration isolator are presented. The main improvements to the isolator are the use of new blades in the GAS structure and the addition of an extra compensation circuit to eliminate the drift. The improved prototype has a resonance period of 29.2s and a continuous working time of several days, as compared with the resonance period of 19.2s and a working time lasting only several minutes of the previous prototype. Experiments show that the improved prototype performs well in the homemade T-1 laser-interferometry absolute gravimeter. The standard error of the mean (SEM) of a 50-drop measurement performed in Tsinghua University is reduced significantly from 404 μGal (1 μGal = 1 × 10-8ms-2) without the vibration isolator to 10.8 μGal with the improved prototype at its best level. Additionally, the SEM of a 50-set measurement (including 800 drops) lasting for 25 h achieves 5.9 μGal with the improved prototype.

In order to meet the g-level vibration isolation requirement of the narrow linewidth laser, which is one key component in high-precision time-frequency scientific experiments, a high-performance active vibration isolation system needs to be designed. This paper synthetically adopts the magnetic sus-pension based active vibration isolation technology, and propose a new active vibration isolation method. The active vibration isolation as well as the position and attitude control are realized by eight voice coil actuators between the ultra-quiet platform and the base. In this paper, the design of the vibration isolation platform, dynamics model, dual-loop coupling control scheme and simulation results are provided sequentially. The simulation results show that after the active vibration isolation control, the 4mg micro-vibration level in the space station is attenuated to 5g, and the vibration isolation capability is 58dB, which meets the requirements of narrow linewidth laser isolation.

In some precision manufacturing processes, like the transportation of TFT-LCD or solar-energy panels, the vibration control of the transportation platform is the key technology to prevent the panels from being damaged. Nowadays, passive vibration isolator is still widely used in the design of the transportation platform because of its simple structure and easy maintenance. The disadvantage, however, is its limited performance become it has no means of adding extra energy to the system. Therefore, the advanced active vibration isolator becomes the effective solution to suppress the vibration of the transportation platform. In this paper, a brand new modeling methodology for an active pneumatic vibration isolator is developed. This mathematical model is based on the international standard ISO 6358. Finally, after comparing the results by experiment and simulation, it is proved that the mathematical model based on ISO 6358 can accurately simulate the dynamic response of the active pneumatic vibration isolator.

In this chapter, based on the Halbach magnetic array, the active and passive hybrid vibration isolation technology for WD618 diesel engine is studied. Firstly, the active and passive hybrid vibration isolators based on Halbach magnetic array is designed. The content includes design requirements, scheme design, and design method; design suitable power amplifier for isolators and verify whether the performance index requirements are met and test the resistance, inductance, stiffness, and static thrust of isolators; the vibration isolation effect of the vibration isolator was tested through a single-degree-of-freedom vibration isolation experiment.