| Metal debris detection technology is essential for maintaining and extending the healthy and stable operation of mechanical equipment.Inductive debris monitors(IDMs)have been widely used in the industry due to their compact structure,low cost,fast measurement speed,and rich information on metal debris.However,due to the restricted relationship between the resolution and the flow rate of IDMs,it is difficult to achieve high resolution under the premise of ensuring a high flow rate.Various noise interference also limits the sensor resolution.The current technology cannot meet the online monitoring requirements of actual equipment.This dissertation takes the IDM as the research object and carries out a series of research work,aiming to improve its detection resolution of metal particles and increase the flow rate of detected liquid without reducing the detection resolution.The main research contents and innovations of this dissertation include:1)Based on the equivalent model of metal particles,the mathematical expression of the output response of the three-coil sensor is established.On the basis of theoretical analysis,the influence of excitation parameters and probe parameters on sensor performance is systematically studied with the help of finite element simulation,which provides theoretical guidance for the subsequent design of the high-resolution IDM.The concept of the technical factor and spatial resolution of the IDM is proposed,which is beneficial to improve the performance evaluation system of the IDM.2)Aiming at the limitation of the resolution and flow rate in the IDM with the traditional three-coil probe,a parallel high-sensitivity probe based on the high-Q resonance method is proposed for the first time,which provides an effective means for the realization of the high-resolution IDM.The high-Q resonant circuit composed of a specially designed large inductance,sensing coils,and an external capacitor is suitable for debris detection in a small channel,which can significantly improve the sensitivity of the probe,thereby realizing the high-resolution IDM.At the same time,the parallel multi-channel design also meets the large flow requirements of the sensor.Every detection channel in the developed sensor prototype has an outer diameter of 3 mm,and the flow rate of 7 channels in parallel is 148.4 L/min;the Q value is up to 104.The sensor can detect iron particles as small as 23 μm and copper particles as small as 64μm,with a technical factor as high as 434,which is much higher than the technical level in the existing literature.3)On the basis of comprehensive analysis of IDM system noise and high current excitation characteristics,an intermittent current excitation method is developed for the first time and a high-resolution circuit system based on intermittent excitation is designed and implemented,which further improves the detection resolution,range,and temperature stability of the IDM.The design process of the circuit system based on intermittent excitation is introduced in detail,and its detection performance is obtained by experiments.The sensor prototype has good temperature stability and can detect iron particles of 48 μm-1426 μm and copper particles of 112 μm-3802 μm in a detection channel with an outer diameter of 10 mm.The technical factor is 208.3.Compared with the traditional constant excitation sensor,the sensor using intermittent excitation has obvious advantages in detection resolution,range,and stability.4)For several common interference sources in the IDM,the generation mechanism of interference noise is analyzed in detail and corresponding noise suppression measures are proposed.Firstly,for impurity interference,a new low-voltage excitation scheme is proposed,which is theoretically analyzed and experimentally verified.The experimental results show that the scheme can effectively suppress the interference noise caused by impurities such as water droplets and bubbles without sacrificing the detection sensitivity of metal particles.The theoretical calculation and simulation analysis of the single-degree-of-freedom vibration isolation system are carried out,and a double-layer vibration isolation system is designed to maintain the working stability of the IDM under external mechanical vibration conditions.Finally,the electromagnetic noise suppression measures in the design of probes,circuits,and transmission cables are explored to improve the detection resolution and reliability of IDM for metal debris.In this dissertation,the influencing factors of the detection resolution of the IDM are systematically studied,and the relationship between the output of the sensor probe and various related parameters is given.The research results help to further improve the level of mechanical equipment health monitoring and fault diagnosis using IDM,and also provide new ideas for the research of metal debris detection sensors based on other principles. |
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