Research On Rotary Channel Modeling Based On Markov Chain For Wireless Sensor Monitoring On Motorized Spindle

Nowadays, motorized spindle has become a critical part of modern machine tools, and its condition monitoring technologies take a very important role in machining accuracy improvement. Wireless sensor monitoring, which sets free the layout of sensors from the limitation of rotating shaft, is of non-comparable advantages among many methods of spindle condition monitoring. The most essential part of wireless sensor monitoring for electric spindle, is the reliable communication between rotary wireless sensor and static receiver. Therefore, this thesis mainly researched on the characteristics of rotary wireless channel for motorized spindle. This thesis is supported by National Natural Science Foundation of China (51105336). The thesis analysed the characteristic of electromagnetic wave transmission in electric spindle rotary state, and established a model for rotary channel base on Markov chain.There are two mainly effects for the wireless communication for spindle condition monitoring:the multipath effect produced by reflection of electromagnetic wave in machine tool environment, and the Doppler Effect produced by high-speed rotation movement of the wireless sensor module. This thesis made a deep research on these two effects. On the base of that, the wireless communication process is divided into two states:line-of-sight communicaiton and non-line-of sight communication. These two states are identifid by whether there is direct signal between transmitter and receiver. And then, the stochastic characteristic of the obstructions in actual environment of spindle monitoring system is researched. According to the stochastic characteristic of obstructions, a markov chain model is established for describing the state switch process between line-of-sight and non-line-of-sight state. The model has good adaptability to different installation modes and machine tool environments.In the last, simulation and experiment are conducted for channel model verification. A rotary channel detection system was developed for channel detection experiment. The channel characteristic data is collected in the experiment and used to fit the parameters of the channel model. The result demonstraes the efficiency and practical value of the channel model.