Spatial Noise/Vibration Transmission Encoding Metamaterials:Theories And Applications

As the next-generation equipment develops in the direction of high speed,light weight,large size,heavy load,and running in the exterme environments,the vibration and noise problems of the equipment are becoming serious.Strong vibration and noise endanger human health,interfere with human life and ecological environment,reduce the performance of equipment,and affect the safe operation of equipment.At the same time,the information extracted from vibration and noise can reflect the condition of the equipment,thus providing a basis for the health monitoring and diagnosis of the equipment.Therefore,the accurate and efficient identification of vibration and noise is of great importance to achieve vibration and noise reduction,ensure the safety and comfort of human production and life,and ensure the safe operation of equipment.Traditional noise/vibration identification methods depend on large number of sensors,which leads to complex hardware and high power consumption.Therefore,developing novel noise/vibration identification theories and technologies has become a research focus.Acoustic metamaterials are artificial structures that can flexibly manipulate elastic waves and acoustic waves.The extraordinary physical characteristics provide a new way of thinking to break through the traditional noise/vibration identification technologies.At present,the research on noise/vibration identification with metamaterials is still in its infancy.The theory of encoding spatial acoustic information is not perfect.The research on the encoding of spatial vibration information still has a knowledge gap.Therefore,research work in these areas are urgently needed.Aiming at the difficulties of traditional noise/vibration identification technologies,this thesis proposes a new type of compact noise/vibration identification theory and technology.Theoretical studies on spatial noise/vibration transmission encoding with metamaterials are performed,and single-sensor noise/vibration identification technologies are developed.This work is of great significance in constructing novel sensing systems for noise/vibration detection,identification,and control.The main research contents and innovations of this thesis are provided as follows.(1)A theory of directional acoustic transmission with phononic crystal cavity resonance is proposed to solve the problem of the low angle resolution of current acoustic sensing structures.This thesis uses the band theory to analyze the principle of phononic crystal cavity resonance.The physical mechanism of the directional coupling between the acoustic cavity and the acoustic waves are investigated We achieve the 0/1 encoding of the azimuthal acoustic transmission,that is,the amplitude of acoustic waves can be amplified under the normal incidence,wheras can be suppressed under other incidences.The prototypes of directional acoustic sensing devices with desirable acoustic directivity are constructed based on the phononic crystal cavity resonance.The devices have the advantages of simple system,low cost,and high sensitivity.(2)A metamaterial single-sensor acoustic camera prototype is proposed to overcome the shortcomings of the large number of sensors and large array apertures in current acoustic imaging methods.We propose and investigate a space-coiling metamaterial with randomized structural parameters.The anisotropy of the effective parameters is the physical basis for spatial transmission encoding of acoustic waves.By combining with the compressive sensing framework,the metamaterial single-sensor acoustic camera prototype is developed.The identification and imaging of multiple sound sources are achieved.Compared with the existing acoustic sensor array,the proposed device only contains a single sensor,which does not require multi-channel data synchronous acquisition,and has the obvious advantages of simple system,small size,and low cost.(3)A randomly coupled resonator dynamics is proposed to fill the theoretical gap of knowledge of spatial vibration transmission encoding.We propose a randomly coupled resonator system and develop a dynamical method for analyzing the propagation of elastic vibrations in the system.The highly uncorrelated spatial vibration transmission encoding can be achieved.The randomly coupled relationship of resonators and the disordered distribution of effective masses are the physical basis for the highly uncorrelated vibration transmission encoding.The effects of system parameters on vibration transmission encoding is also studied.The proposed theory is a dynamical method that combines the physical properties of metamaterials,which is of great significance for analyzing the propagation characteristics of elastic waves in complex systems and designing new metamaterial devices.(4)A metamaterial single-sensor vibration identification technology is proposed to overcome the shortcomings of traditional vibration identification methods that rely on large number of sensors and complex hardware.Based on the dynamics of randomly coupled resonator system,a randomized resonant metamaterial is designed,which consists of randomly distributed local resonantors with randomized resonant frequencies.We investigate the highly uncorrelated vibration transmission encoding of elastic vibrations in the metamaterial system.By combining with the compressive sensing algorithm,the proposed metamaterial system can realize the identification of spatial multiple vibration sources with only a single sensor.The trajectory tracking of impact sequences can also be achieved.Compared with traditional methods,the proposed metamaterial system has the advantages of simple system,low cost,and low power consumption.It opens up new avenues for designing novel compact vibration sensing devices and systems,and has broad application prospects.This thesis systematically studies the transmission coding properties of acoustic metamaterials for spatial vibrations and acoustic waves.Corresponding theories and analytical methods have been developed.The prototypes of novel metamaterial devices are designed.Single-sensor identification of spatial vibration sources and sound sources are achieved.This study provides an important theoretical and technical basis for the realization of compact noise/vibration identification,and provides new technical approaches to equipment noise/vibration reduction,structural health monitoring and diagnosis,and opens up new avenues for designing metamaterial sensing devices and systems.