This paper presents a practical method for engineering test on the base of mechanical eccentricity principle, and a new vibration test equipment for testing the quality of pavement is designed. A sensor was installed on the exciting bar for measuring the exciting force and frequency which generated by the equipment. The mechanical performance could be detected according to the deformation of object. The equipment has the merits such as small volume, light weight and compact conformation. It can be used not only in laboratorybut also in field and has great practical value.
The mechanical equipments driven by induction motor are widely used in manufacturing. Aiming at this type of equipment, some holes are advisedly drilled on the bars to simulate the broken bar faults of the motor, and with on-off loads changes of output circuit of the load generator, forced torsional vibration of rotor was generated. Using the above simulation test ways, the typical faults of motor and its driven equipment are tested and analyzed. In addition, an signal analysis method using Hilbert conversion envelope spectrum and real modulation zoom envelope spectrum is proposed, this method can effectively extract the faults information of stator current, reject the useless power frequency. The experimental results indicate that: this method can identify not only the faults of the motor itself, but also municipal fault types of the motor’s driven equipment. Especially, through the contrastive experiments on the unbalance and the torsional vibration of the rotor, the conclusion is made that the method is more sensitive to torsional vibration detection. Also, it develops a new direction for the application and the research of sensorless detection and diagnosis method.
It is first to make Empirical Mode Decomposition (EMD) and achieve Hilbert-Hung transform (HHT) of envelope spectrum after Hilbert transformation, which can resolve the cross fault existing in Hilbert transformation is utilized merely. However, it can’t improve the resolution of envelope spectrum, which doesn’t adapt the characteristic of high resonant frequency of rolling bearing and low fault frequency. The paper utilizing the principle of real modulation shift frequency moves the EMD decomposition components of high frequency section to low frequency section and makes analysis of envelope spectrum after Hilbert transformation, which resolves the problem of low frequency resolution of pure HHT.
ntrinsic mode function component (IMF) has been effectively decomposed by using empirical mode (EMD) decomposition method, and the high-frequency resonance frequency band the rolling bearing components is extracted. Then the high frequency component of the IMF is shifted to the lower frequency by using real frequency modulation principle, and a new envelope refining spectrum is obtained through the Hilbert transform after low frequency sampling. The method not only simplifies the design of band-pass filtering process but improves refinement computational efficiency of the envelope spectrum. The method verifies the correctness of the theory and practical method through the analysis of the fault diagnosis of rolling bearing inner ring experiment.
In order to research the possibility of Motor Current Signature Analysis (MCSA) applied to fault diagnosis of double fed wind turbine generator system and overcome the defect of sensor stalled installed inconveniently with regular vibration inspection method constructs a simulation model of double fed wind turbine generator with SIMULINK, which uses PWM module for stator excitation and the signal of rotating speed and torque of external dynamic changes to simulate the fault of wind turbine motor transmission system, and then verifying the accuracy of fault features of stator current when generator system has fault by emulating and analyzing the response process of signal in the stator current of generator with different situations.
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