Research On Speed Fluctuation Feature Extraction Method Of Motor Controlled By Variable Speed Hydraulic Pump

With the strong adaptiveness for complicated working condition,wide speed range and simple structure,the hydraulic system has been widely used in national defense equipments,aerospace,material processing,engineering machinery and other fields,the research on the operation safety assurance of these devices is very significant.However,the monitoring signals of flow,pressure and vibration commonly used in hydraulic system are susceptible to noise interference especially under variable speed operation,which result in difficulty in condition monitoring of hydraulic system under varying speed operation.The research on the kinetic stiffness degradation mechanism of mechanical and electrohydraulic system showed that the variable condition impacted the internal parameter of kinetic stiffness and external parameter of speed fluctuation of instantaneous angular speed（IAS）^[1].In addition,the IAS has the characteristics of high signal-to-noise ratio and strong sensitivity for early failure.Therefore,aiming at the hydraulic system under the varying speed operation,the precise measurement of motor instantaneous angular speed（MIAS）is investigated firstly in this dissertation,and then the motor speed fluctuation features extraction（MSFFE）software and hardware technologies are developed.Finally,the relations between speed fluctuation features of plunger motor and performance of variable speed motor controlled by pump system（VSMPS）is revealed,which forms a huge foundation and technical supprot for hydraulic system condition monitoring in varying speed operation.The main contents of this dissertation are as follows:（1）The precise measurement of MIAS in varying speed operation is studied.The effectiveness of IAS measurement method which combined speed tooth-disc and magneto-electric speed sensor with software counting algorithm is tested,and then speed error sources and its suppression approaches are deeply analysis.Quantization error（QE）is the main error sources,the research on generating mechanism and calculating method of the QE is developed,and the effective suppression methods are proposed.These works improve the measurement accuracy of MIAS in varying speed condition and provide an application foundation for MSFFE.（2）MSFFE method under varying speed operation is studied.The motor speed fluctuation signal（MSFS）is characterized as frequency modulation and amplitude modulation under varying speed operations,which leads to the traditional speed fluctuation feature extraction method failure.So that the MSFFE method called order filter（OF）is established,which based on band-pass filtering and time domain flipping principle.After filtering the MSFS in angular domation and angular-time domation transform,the OF can accurately extracts and separates each component of motor speed fluctuation feature.The research not only forms a technical support for running monitoring of VSMPS based on MIAS,but also provides new ideas and new methods for the accurate extraction speed fluctuation feature of other machinery in varying speed operation.（3）Verify the validity of the method based on instantaneous speed fluctuation analysis.On the basis of hardware and software of VSMPS,the MSFFE method is conducted to extract and separate each component（0.325x and 1x）of piston motor speed fluctuation feature after precisely measuring the IAS of piston motor under varying condition experiments.The change rule of the two speed components’speed fluctuation features with the speed of power source and load is analyzed.These works form a solid foudation for hydraulic system running state monitoring under varying speed operation based on MIAS.（4）Online IAS measurement and speed fluctuation features extraction system in varying speed operation is developed.Upon the MIAS measurement,calculational method of QE and MSFFE principle,the mixed programming method of LabVIEW and MATLAB is used to develop the online IAS measurement and speed fluctuation feature extraction system for condition monitoring of VSMPS.The system can be efficiently applied to other equipments in varying speed operation through changing the parameters.