Theoretical And Experimental Research On Electromagnetic Metallic Wear Debris Sensor

Oil monitoring is an important means in equipment condition monitoring and fault diagnosis which gets more and more attention. As an important part of oil monitoring, on-line oil debris monitoring which can obtain the debris information of complex mechanical system is of great significance for wear evaluation and potential fault diagnosis of the critical component. Due to the simple of structure, real time monitoring, high sensitivity and rapid response, the electromagnetic oil debris monitoring sensors have a broad application prospects in oil monitoring. An on-line oil debris monitoring sensor based on the electromagnetic theory is theoretically and experimentally studied in this thesis, the main research contents include:1. The theoretical model of the inner magnetic field of the sensor is built based on the three-phases double-drive solenoid. Then the theoretical model of the output signal is obtained. In the process of building the theoretical model, we give a serious consideration on the effect of the copper coil’s diameter to the multi-layer solenoid. Then numerical simulation is carried out and the influence rules of the structure parameter, the debris size and its motion parameter on the output signal of the measured coil are obtained,2. The electromagnetic simulation is conducted by the magnetic simulation software. The influences of the exciting source voltage, frequency, size of debris and oil flow velocity on the measured coil are analyzed. The results provide the theoretical reference for the structure optimizing and signal processed circuit designing.3. According to the theoretical model and the result of the electromagnetic simulation, the electromagnetic oil debris monitoring sensor is designed which includes two main part, the solenoid structure and the signal process circuit. For the performance test of the sensor, the experimental program is designed and the experimental platform is built. The metallic debris detection performance is validated by both single metal particle sample experiment and lubrication oil loop experiment simulating the actual working conditions.4. For the oil condition signals, the main issue is that the weak signals of small particles are often contaminated by the background and interference signals which make the measured coil output signal’s SNR(Signal to Noise Ratio) low. In order to solve this problem, on the basis of preprocessing and spectral analysis of the experimental data, wavelet de-noising method is mainly studied to enhance the SNR of out signal, and finally to improve the distinguishing ability of the sensor for micro metallic debris.