LCMP Beamforming Algorithm And Application

Acoustic measurement technology based on microphone array can enhance the desired direction signal and suppress interference and background noise,which is widely used in structural NVH analysis,and ultrasonic inspection in power and petrochemical industry.However,most mechanical machining is operated in a reverberation and strong background interference environment,which brings challenges to the development of acoustic detection.The linear constraint minimum power(LCMP)beamforming algorithm can flexibly select different linear constraints according to requirements and has better application performance.Therefore,for online acoustic detection of machining process,considering reverberation sound field environment,LCMP beamforming algorithm and its application in machining detection are studied in this dissertation.The research work of this dissertation is summarized as follows:(1)The LCMP robust adaptive beamforming algorithm is studied.The basic model of LCMP beamforming algorithm is described,and the influence of linear constraints on the performance of LCMP algorithm is investigated by numerical simulation.Furthermore,for the algorithm performance degradation caused by errors such as steering vector mismatch and array perturbation,two robust adaptive algorithms are studied-implementation of generalized sidelobe cancellation based on scaled projection and variable diagonal loading.Finally,it is found that the variable diagonal loading algorithm has better robustness by testing far-field sound source location under different signal-to-interference ratio conditions.(2)The LCMP algorithm based on spatio-temporal model is studied.Based on the sound reverberation model,the source localization performance of the variable diagonal loading algorithm under different reverberation levels is investigated by simulation,and the selection of its key control parameter is discussed.Considering dereverberation requires true channel impulse response(which is difficult to obtain),the LCMP acoustic signal enhancement algorithm based on the spatio-temporal model is studied,and the effectiveness of this algorithm is verified by simulation and experiment.(3)The application study of machining testing is carried out.Combined with the developed LCMP acoustic signal enhancement algorithm,the testing and signal enhancement experiment of automobile flywheel rattle vibration noise and grinding noise in reverberation environment are undertaken,and the applicability of the developed method for mechanical machining detection is discussed.Through the development of the research work in this dissertation,the acoustic signal enhancement approach in reverberation environment is established,which has certain application value for on-line acoustic detection of the machining process.