Modal Parameters Identification Of Loading-Conveying Reducer Based On Operation Modal Analysis

With the integration of coal resources and the improvement of the safety requirement, the mechanized mining equipments usher in the golden period of development. The loading-conveying reducer of continuous miner is one of the core components of the fully mechanized coal face, its accurate design and reliable operation are important guarantees to the productive and efficient modern mines.The reducer usually has a high failure rate due to the extremely poor working conditions of the coal mine. The study about the sources of its failure find the one source is the errors in the design, manufacturing and assembly process of the new product; the other is the work fatigue, overload, and environmental pollution.Modal analysis is an important mean of studying structural dynamic characteristics, it can get the vibration response of structures under the various internal and external excitations, providing accurate references for the design optimization, fault diagnosis, condition monitoring of the structures. The finite element modal analysis of the reducer model obtains the modal frequencies and mode shapes under the free state and constraint state.The results can be the reference to the design optimization of the reducer, and the mode shapes to the corresponding modal frequencies can be used as important basis for the layout of modal test points.The traditional experimental modal analysis is under the artificial excitation, and the modal parameters are identified by the transfer function or impulse response function between the excitation and response, getting a good reflection of the modal characteristics of the structure at the stationary state. Being rotating machinery, the structural vibration characteristics of reducer varies greatly under static and working conditions, and the operational modal analysis can better analyze the dynamic characteristics of the working structural.The frequency domain decomposition technique is an extension of the peak-picking method, obtains the modal parameters by the singular value decomposition of the response signal power spectral density matrix at the discrete frequency, overcomes the shortcomings of the peak-picking method, and has higher recognition accuracy and stronger anti-noise ability. Gear meshing generates harmonic excitation when reducer working, making the modal analysis results include structural modes and the harmonic modes. The probability density analysis is a method of signal recognition, and which is applied to the analysis of these two signals, finding that the significant differences of probability density curve characteristics of the two signals exist. In this paper, the operational modal parameters are identified by using frequency domain decomposition, and the two different modes are distinguished by the solution of the probability density, thereby accurately identifying the real structural modal parameters. Compared with the result identified by using LMS Test.Lab commercial vibration analysis software, the result coincides well, proving the frequency domain decomposition technique is feasible and accurate, and its analysis result can be used as reference to the reducer optimization.Taking into account the complexity of the structure and drive of reducer, the spectrum analysis of vibration signal is done, finding the vibration characteristics of the no-load and full load are different, the resonance of the frequency of parts and harmonic frequency exist, the processing and installation errors exist, all those can provide accurate reference to the reducer optimization.