Research On Observer-based Incipient Fault Diagnosis Of Motorized Spindle Drive System

The motorized spindle adopts the transmission structure of the spindle motor and the machine tool spindle "combining two into one",which realizes the "zero transmission" of the machine tool.As the core component of high-end machine tools,the service performance of the motorized spindle has a decisive effect on the machining accuracy in the precision manufacturing process.Due to long-term work under severe conditions such as heavy load,fatigue,and corrosion,the stator-winding of the motorized spindle inevitably lead to direct contact with coils that should not be connected to form a low impedance loop.At this time,the unbalance of three-phase current will reduce the torque of the motorized spindle and affect the machining accuracy and efficiency of high-end CNC machine tools.Therefore,it is very necessary to conduct real-time monitoring and incipient fault diagnosis on the running status of the motorized spindle drive system.The article takes the motorized spindle drive system as the research object and studies its observer-based incipient shorted-turn fault detection and isolation methods.The main contents are as follows:(1)It is difficult to design observer for the high-order,multi-variable,and strong coupling complex motorized spindle drive system under three-phase coordinates.The coordinate transformation(Clark transformation,Park transformation)is used to reduce variables and eliminate the coupling relationship between electromagnetics,so as to simplify the statorwinding shorted-turn fault model of motorized spindle drive system.Under the two-phase rotating coordinate,the motorized spindle drive system of the stator-winding shorted-turn fault is modeled as the basis of the subsequent chapters.In addition,a quantitative description of incipient shorted-turn faults is given and the incipient faults are divided into three levels.This article realizes the second level of shorted-turn fault detection and isolation.(2)It is difficult for Luenberger observer and constant threshold to accurately detect the stator-winding incipient shorted-turn fault of motorized spindle under the influence of electromagnetic disturbance,so an incipient shorted-turn fault detection method based on modified observer is proposed.Compared with the Luenberger observer,the modified observer has more design freedom,which can make the residual generated by the modified observer have better electromagnetic disturbance robustness and incipient shorted-turn fault sensitivity in the optimization process.In addition,while the residual is generated,the positive scalar to be optimized is introduced to give the mathematical expression of the adaptive threshold,which greatly reduces the conservativeness of the incipient shorted-turn fault detection compared with the constant threshold.(3)Luenberger interval observer with better real-time performance cannot be used in the stator-winding incipient shorted-turn fault detection of the actual motorized spindle,so an incipient shorted-turn fault method based on novel interval observer is proposed.In the presence of electromagnetic disturbance,two aspects can make the stator-winding incipient shorted-turn fault of motorized spindle detected earlier.Firstly,in actual motorized spindle drive system application,the Luenberger interval observer has no solution,and the novel interval observer overcomes this shortcoming,so that the residual interval generated by it has better performance and wider range in the optimization process.Secondly,the l1/H? performance is introduced in the process of residual interval generation,which brings better electromagnetic disturbance robustness and incipient shorted-turn fault sensitivity.(4)The incipient shorted-turn fault detection and isolation of stator-winding in distributed multi-spindle system with limited communication bandwidth are not fully considered,an incipient shorted-turn fault detection and isolation method based on event-triggered interval observers is proposed.Firstly,considering the output of the local and adjacent motorized spindles,shorted-turn fault signal boundary of motorized spindle stator-winding,the influence of electromagnetic disturbance and the error of event-triggered,the new event-triggered fault detection and isolation interval observer is constructed.Secondly,the electromagnetic disturbance robustness,shorted-turn fault sensitivity and non-negativity conditions are given.These conditions can be solved by the optimized gain parameters of the new event-triggered fault detection and isolation interval observer.Finally,when the residual interval does not contain zero,it means that the stator-winding of the motorized spindle has no fault,otherwise it means fault.Under this framework,each motorized spindle not only has the ability to determine which neighboring stator-winding of motorized spindle has incipient shorted-turn fault,but also introduces an event-triggered strategy to reduce communication and computing resources.The above-mentioned observer-based incipient shorted-turn fault detection and isolation method is verified by the motorized spindle experimental platform.The results show that the method proposed in this paper has a good performance in the stator-winding incipient shortedturn fault diagnosis of motorized spindle,and is a good alternative method for incipient fault diagnosis of motorized spindle drive system.