| Shrinkage pin failure is a common contact failure form of locomotive electrical connector.The rapid and accurate detection of shrinkage pin failure is of great significance to the normal and stable operation of locomotive.The traditional failure detection devices have the disadvantages of low detection efficiency,poor adaptability and low detection accuracy.A kind of sensor which can be used for needle shrinking detection,based on the electromagnetic induction principle of linear differential transformer displacement sensor was designed in this paper,including multi-degree-of-freedom mechanical stages,signal processing circuit system,and an experimental study on the performance of the differential transformer displacement sensor was studied.According to the characteristics of small pin diameter and center distance of electrical connector and various shell shapes,a coil and iron core structure matching the technical requirements of detection was designed.The equivalent circuit model of differential transformer displacement sensor is analyzed,the relationship between the electrical parameters of the sensor is obtained.Based on the principle of electromagnetic induction,a three-stage Linear Variable Differential Transformer(LVDT)structure was designed to obtain the theoretical relationship between the output voltage and the core displacement.To deal with the complicated electromagnetic signal of the sensor,a set of circuit system fit with the sensor was designed.The excitation circuit and power-following circuit for the primary coil are designed.Using the signal processing chip AD698,the processing circuit of sensor differential output signal was designed,completing the function of signal recognition,computation and filtering,getting a linear dc output level related to the core position.In addition,according to the electrical requirements of the sensor,the relevant integrated stabilized voltage supply circuit,the differential following circuit for amplifying the excitation power,and the phase adjustment circuit to improve the detection trigger precision,were also designed.And the overall circuit layout and PCB board was designed,in order to improve the circuit packaging stability.Finally,a set of signal acquisition system based on ADC and single chip microcomputer was designed according to the output of signal processing circuit,and the error removal and acquisition of sensor output signal are completed.A set of multi-freedom experiment platform,which can accurately control the attitude and the space position of the sensor coil and iron core was designed,providing a good platform for the sensor performance test experiments.According to the testing requirements of the shrinkage pin detection of the electrical connector,the physical characteristics related to the sensor are experimentally studied.Firstly,the output characteristics of the actual electrical signal of the sensor were studied,and the noise components of the output signal were analyzed.Secondly,the static physical characteristics of the sensor were studied,including linearity and hysteresis.The experimental results show that the linearity of the independently developed differential transformer displacement sensor is 1.81%,and the hysteresis is 0.247%.Finally,the electromagnetic coupling law between sensors is studied for the condition of simultaneous detection of multi-sensor array layout,and the influence of the relative position of the iron core and the layout spacing of sensors on the output signal of sensors is discussed,when two pins are arranged in parallel,which provides a certain reference for the layout scheme of multi-sensor array.The thesis has 49 figures,2 tables and 82 references. |
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