Purpose The purpose of this study is to develop a cylindrical capacitive sensor that has the advantages of high resolution, small size and designability and can be easily installed on lubricant pipeline to monitor lubricant oil debris. Design/methodology/approach A theoretical model of the cylindrical capacitive sensor is presented to analyze several parameters’ effectiveness on the performance of sensor. Numerical simulations are then conducted to determine the optimal parameters for preliminary experiments. Experiments are finally carried out to demonstrate the detectability of developed capacitive sensors. Findings It is clear from experimental results that the developed capacitive sensor can monitor the debris in lubricant oil well, and the capacitance values increase almost linearly when the number and size of debris increase. Research limitations/implications There is lot of further work to do to apply the presented method into the application. Especially, it is necessary to consider several factors’ influence on monitoring results. These factors include the flow rate of the lubricant oil, the temperature, the debris distribution and the vibration. Moreover, future work should consider the influence of the oil degradation to the capacitance change and other contaminations (e.g. water and dust). Practical implications This work conducts a feasibility study on application of capacitive sensing principle for detecting debris in aero engine lubricant oil. Originality/value The novelty of the presented capacitance sensor can be summarized into two aspects. One is that the sensor structure is simple and characterized by two coaxial cylinders as electrodes, while conventional capacitive sensors are composed of two parallel plates as electrodes. The other is that sensing mechanism and physical model of the presented sensor is verified and validated by the simulation and experiment.

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In order to facilitate dynamic analysis of spindle, improve the vibration characteristics of the spindle and achieve the goal of control of spindle motion stability. A spindle vibration testing system is developed with necessary sensor, signal conditioner and data acquisition card based on Labview software in this paper. The spindle vibration testing and analysis system is formed based on virtual instrument graphical programming language Labview. The hardware is reduced in testing process. At the same time, acquisition, processing and analysis for vibration signal are realized, and the costs of hardware are greatly reduced. The testing work is made more convenient and quick by this system, and test is made more intuitive by its real-time display function. It will provide a scientific basis for searching for measures to reduce the spindle vibration and developing a new generation of mechanical structure of the spindle.

In this paper, a set of spindle vibration test equipment has been designed by using modern design method, on the basis of in-depth study of spindle vibration source .The device includes three parts: machinery, detection and control .In the mechanical part, using sensor fixed machine mobile systems, the design of the spindle drive part and test board was carried on respectively .In the detection part ,the virtual instrument Labview graphical programming language was adopted to form a spindle vibration test and analysis system, realizing the acquisition, processing and analysis of the vibration signal .In the control part, Yan Hua movement control cards are adopted to realize control of motor speed, through Labview programming.