Mechanism Of The Kinetic-energy Rate Of Change And Internal-external Features Related Analysis For Mechanical And Electrohydraulic System

By integrating the multi-energy characteristics of mechanics,electrics and hydraulics,the mechanical electrohydraulic system(MEHS)is widely applied into lots of fields such as construction machinery,aerospace,marine system and so on.Therefore,it is significant to guarantee the safety of MEHS,in which the important method is to monitor the running sates and evaluate performance.However,with the process of multi-energy conversion,the mechanism of MEHS running is much complicated.Especially,during the vary-operation condition,the MEHS usually expresses low efficiency,non-linearity and non-stationary characteristics,which brings great difficulty to monitor its running states and evaluate performance.Fortunately,there is abundant information hidden into the multi-source signals from MEHS,which provides convenience for monitoring the running states of MEHS.Based on the collection of multi-source signals,bridging the gap between the running information and varying performance becomes the key to monitor the running states and evaluate the performance of MEHS.Aiming at the urgent requirement of monitoring running performance of MEHS,this work proposes a new way to monitor the running performance: internal-external features raleted analysis(IEFRA).IEFRA reveals an essential regular that the change of running performance derives from the effects of operation condition on internal parameters.Then,the varying parameters change kinetic energy stiffness(KES)inside and alter the fluctuation of instantaneous speed(ISF)outside.During the transmission of effects from operation condition,KES and ISF act as the inside and outside features respectively.Therefore,by analyzing the mechanism of running performance with operation condition from inside to outside,IEFRA provides a new idea and method to monitor the running performance of MEHS.In this work,the main contents consist of four parts as follows:(1)The important role that the kinetic-energy rate of change(KERC)plays in characterizing the running state of MEHS is discussed.Combined with the dynamic model of MEHS,the power distribution and the process of multi-energy conversion are studied.The relevant results show that the KERC is an important component in the multi-energy conversion.In addition,KERC relates to the efficiency and running smoothness of MEHS.Based on such conclusion,the dynamic power-matching principle is put forward,in which the KERC is an important parameter to evaluate the running performance of MEHS.The evaluation of KERC is able to monitor the running performance of MEHS,which is the problem source of IEFRA.(2)The internal feature that is KES and its detection method are proposed,which is used to quantify KERC.Firstly,the concept,KES is a kind of capability that the output kinetic energy of system resists the disturbance of stimulation source,is reveled.Then,the effects of system parameters on KES are analyzed,and the results show that multi-energy parameters have influence on the magnitude of KES.Finally,as a product of multi-information fusion,the KES can be detected by the technologies of signal modulation and information fusion.After fusing the multi-source signal into Lissajous-Figur,the inclination can be used to quantify the magnitude of KES.In addition,the area of the KES annulus is used to measure the loss of KES.(3)In order to expand the application of KES into the engineering,the extraction method of ISF is studied.Based on the sampling-point-counting algorithm,the instantaneous speed is captured,and it is found that quantization error is the main source for the algorithm.Therefore,the mechanism and elimination of quantization error are analyzed,and the results show that increasing sampling frequency can eliminate the quantization error effectively.After the accurate measurement of instantaneous speed,the instantaneous speed in time domain can be convert into angular domain using gear disk.Then,the extraction method of ISF based on the short-time Fourier transform and order analysis is studied,which provides a technology support to extract external feature.(4)On the basis of the extraction methods of internal feature and external feature,the IEFRA is validated by the experiments under varying operation condition.The experimental results show that the internal feature and outside is changed with the operation condition.The larger the KES loss,the bigger the ISF is.Moreover,IEFRA reveals the objective regular that the mechanism of KERC is the process of producing inside and expressing outside.the relavant results builds up the fundamention to the related analysis between positive and negative problem of MEHS.