Design And Characteristics Of An Inductive Debris Sensor Based On High-gradient Magnetic Field

Compared with traditional methods such as vibration and temperature detection,oil debris detection technology can effectively advance the time point of mechanical equipment failure detection and provide real-time wear information,which is of great significance to the intelligent operation and maintenance of major equipment.The inductive method is widely used in mechanical equipment failure monitoring due to its strong penetrability,ability to distinguish the ferromagnetic debris characteristics and not robustness for the oil color and non-metallic particles.However,most of inductive sensors have the disadvantages of low magnetic field strength,weak anti-interference,and small throughput.Therefore,it is necessary to study the inductive debris detection sensor and develop online debris detection methods with high sensitivity and stability.The inductive debris detection sensor based on a planar high-gradient magnetic field is proposed in this thesis,and the sensor model which uses the air gap to increase the magnetic field gradient is established.Through the equivalent magnetic circuit method,the equivalent magnetic circuit of the sensor is established,and the mathematical output model is further derived.The magnetic field distribution and output characteristics are verified by simulations and experiments.Meanwhile,the advantages and disadvantages of the sensor are discussed,then the working schemes that can be applied to working conditions are introduced.Subsequently,based on the planar high-gradient magnetic field,a debris detection sensor based on the rotational symmetry high-gradient magnetic field is proposed to improve the flow rate and detection accuracy.The mathematical output model of the sensor is further improved.The magnetic pole parameters and magnetic field distribution of the sensor are simulated and calculated.At the same time,an experimental rig is built to analyze the relationship between sensor output and coil parameters and debris parameters.The detection performance of the sensor was also verified through oil experiments.Finally,to reduce the influence of the magnetic field weakening in the radial position inside the sensor on the output,a multi-inductive coil structure is proposed.The output signal is analyzed through simulation,and the crosstalk phenomenon between inductive coils is discussed.Some experiments are adopted to verify the signal crosstalk phenomenon under working conditions,and feasible signal processing and circuit methods are provided.In this thesis,inductive sensors based on high gradient magnetic field are proposed.Different optimized structures are built,the distribution characteristics and the output signals of different sensors are analyzed.Experiments show that the optimized sensor can detect ferromagnetic wear particles smaller than 13?m,which provides a high-precision detection method for detecting oil debris and judging the wear status of mechanical equipment.