Design Of Vibration Signal Acquisition System Based On Order Ratio Analysis

The large rotating machinery is widely applied in electric power, petrifaction and machine manufacturing, and plays an important role in the social production and life. Meanwhile, it has developed increasingly for the direction of large scale, high speed and automation. It is greatly essential to conduct the condition monitoring and fault diagnosis for this kind of equipment in order to improve the security and reliability of its operation. The analysis on the features of vibration signal is an important means of condition monitoring and fault diagnosis for the rotating machinery, and the order analysis technology is the significant analytical method. Discrete Fourier transformation is adopted as the analytical approach in the present vibration signal acquisition instrument, which has relatively ideal analysis effect for the stationary vibration signals, but is short of perfect and effective characteristics analysis function for the non-stationary vibration signals of rotating machinery with the processes of speed growth and reduction as the representatives.Aimed at the current situation, the basic principle and implementation model of calculation and order tracking analytical approach is analyzed and studied in the present paper, and the software platform is utilized to imitate the order tracking for the run-up signals of rotor. According to the low-frequency and small-amplitude features of vibration signals in the rotating machinery as well as the hardware requirement of the calculation and order tracking analytical approach, a design plan of multichannel vibration signal acquisition system for the order analysis is proposed, the hardware circuits in the all parts of system are designed, PCB circuit board is drawn, and FPGA data acquisition system and ARM Ethernet transmission procedure based on UDP protocol are compiled. As the core of the data processing and control, the ARM+FPGA Framework is adopted in the system to realize the synchronous acquisition of eight-channel vibration signals and the measurement of two-channel rotational pulse signals. After the receival of acquisition order sent by the upper computer and the allocation of internal logic of FPGA, the selection of vibration signal acquisition channel, the switchover of amplification factor and the control of A/D work pattern are realized by the system. Then the FPGA reads the data acquired by A/D and sends it to ARM through AHB high-speed bus after the serial-parallel conversion and FIFO cache. Through the Ethernet, the system can implement the telecommunications with the computer.The system performance indexes are tested and analyzed. The results show that this system is able to realize the accurate sampling and revivification of signals within the frequency of 60kHz and the sampling resolution can reach 0.1 mV, and the acquisition result has low relative error below 0.5%. Rotor platform is used by the paper to create the testing environment and stimulate the fault of the rotating unbalance, then conduct the order analytical diagnosis.The operation condition of the equipment can be judged by the acquired order spectrum in an effective way, thus to achieve the desired design target.