A Study On The Measurement System And Technology Of Fault Diagnosis For Elevators

With the development of modern society, the elevator, transportation tool for high buildings, has been rapidly improved. The requirements to ride comfort and safety of elevators, as well as for quick access within tall buildings become higher and higher. An elevator cannot provide excellent performance without strict test and accurate alignment. It is also important to monitor and diagnose the potential faults of an elevator in advance during its operation.It is essential to develop a system for measuring the operation parameters of an elevator such as acceleration, velocity, vibration, noise expediently and accurately. It is also important to study the fault diagnosis technology of elevators, to monitor the condition of an elevator in operation, to find out the present or potential troubles and to solve them. So the research on the measurement and diagnosis system of elevators will bring great progress in this industry.This research was financially supported by Ronghong Endowment of the United Technologies Corporation, USA. Firstly, a Data Sampling Network System for OTIS Elevators is developed for improving the quality and reliability and enhancing the competence of OTIS elevators. And then, the fault diagnosis technology of elevators is studied, which focuses on the establishment of the vibration models of the cabin, the research on the mechanisms of faults and the applications of wavelet analysis and information fusion.The main work done in this research and the creative ideas of the dissertation are as follow:1) According to the requirements of UTRC and the national standard, GB/T 10059-1997, all parameters are measured in the workshop, on the floor or in the cabin to simplify the measuring job.2) A new technique is proposed, by which the accelerations, velocities, displacements and vibrations of the cabin are obtained at the same time by measuring only the accelerations of cabin without measurement in machine room and using encoders.3) The errors in speed and displacement measurements based on taking first and second integrals from the measured acceleration are greatly reduced by introducing a correction factor in accordance with the average of the original acceleration.4) The idea of virtual instrument is introduced to develop a measuring system for elevators, which could be modified, expanded easily and efficiently in case of necessity.5) The main factors causing cabin to vibrate are studied and the models for vertical and lateral vibrations of the elevator are established.6) A two-degrees-of-freedom lateral vibration model of the elevator cabin system under different types of excitations caused by the rail straightness and alignment errors is built. This mathematical model not only can be used as a design tool for analyzing the influences of various parameters to vibration and for studying vibration-reduction strategies, but also helps to monitor the performance of the elevator in operation, and to identify possible faults of the elevator.7) Based on the study of the fault diagnosis technology of elevators by vibration analysis, the wavelet analysis method is introduced for signal processing. By using wavelet transform the drive quality of an elevator can be studied easily and effectively by analyzing the vertical vibration signals of the elevator. By using wavelet transform the faults in guide rail system can be identified by analyzing the lateral vibration signals as well.8) The information fusion technology is introduced for fault diagnosis of elevators. Both information fusion method based on multi-operation mode and fusion method based on multi-resolution analysis are proposed, which can be considered as a replacement of the information fusion method based multi-sensors.Field tests have proved the high quality of the developed Data Sampling Network System for OTIS Elevators. The effectiveness of the fault diagnosis methods based on wavelet analysis and information fusion has been confirmed.