Study On Speed Measurement Algorithm By Vibration Based On Chirp Z Transform

Nowadays, rotating machines plays an important role in modern manufacturing,petroleum and petrochemical industry. The method of analyzing the vibration signalto extract characteristic parameters and diagnostic fault is widely adopted. The speedis a very important parameter, of which the accuracy is related to the judgment ofrotating machine performance. It is the premise of modern precision manufacturingand producing. In this context, the vibration signals of the three-phase asynchronousmotors and electric submersible pump units are analyzed to increase the speedaccuracy of rotating machine in this paper. Here are the contents:Firstly, the photoelectric and vibration synchronous speed measurement systemis designed. The photoelectric speed measurement system is integrated with thevibration signal acquisition system in the synchronous speed measurement system.And the former is composed of optical encoder and8254counter, while the latter isbased on the acceleration sensor and USB high-speed acquisition card. This systemcan realize the time synchronization between photoelectric speed measurement andvibration signal measurement, which is convenience to verify and compare theaccuracy and superiority of some algorithms in vibration signal analysis.Secondly, a detailed study of characteristics of Chirp Z transform is conducted.The details are focused on the relationship between CZT and spectrum leakage bysome simulations. And also the influence on CZT accuracy, which is impacted bysampling time and initial phase of signal both in the case of single-frequency andmulti-frequency.Thirdly, the superiority of CZT in practical application is verified via thesimulations designed based on the characteristic analysis above in this paper. Because of the complexity of actual vibration signal, the accuracy of CZT forknown-frequency periodic signals is analyzed by adding known-frequency signals tothe actual vibration signals. At the same time, the related function is used in thevibration analysis of known-frequency signals. The measurement accuracy isimproved to0.05Rev/min within2s sampling time.Finally, attempts of improving the accuracy are made on the basis of CZT. CycleChirp Z Transform is proposed. High accuracy of single-frequency andmulti-frequency signals can be exactly measured within a very short sampling time inthe noise free case. Meanwhile, this algorithm is used in the vibration analysis ofspeed measurement proved to be good. The measurement accuracy is improved to0.05Rev/min within2s sampling time.