The Kinetic Stiffness Analysis Method And Its Application For Mechanical Electrical And Hydraulic System

The mechanical electrical and hydraulic system(MEHS)plays an important role in the fields of civil engineering,metallurgy,mining and military industry by its high-power density,smooth movement,convenient operation and strong carrying capacity.However,the complex and changeable operating environment,the influence of nonlinear factors in the system under varying conditions makes it show performance degradation,power and rotational speed fluctuation,which brings difficulties for system condition monitoring and performance evaluation.Based on the research of the internal and external characteristic correlation analysis method of MEHS,our project group puts forward the effect transfer chain of connecting system internal parameters and instantaneous speed fluctuation.But the coupling relationship between the subsystems is weakened,so the model cannot fully reflect the coupling mechanism of the system parameters under load and power source.In this paper,a typical MEHS-variable speed pump-control motor system is used as the research object for the study,in the establishment of its mathematical model,we analyzed the impact mechanism of multi-domain parameters to the operational status,clarified the physical significance of kinetic energy stiffness.The main research contents are as follows:(1)The nonlinear modeling and multi-parameter coupling analysis of MEHS is the basis of kinetic energy stiffness analysis of MEHS.Because the mechanical,hydraulic and electrical systems carry out energy flow,material flow and information flow transfer and transformation during the operation of the equipment,the system shows strong coupling characteristics,and the nonlinear factors,such as the effective volume modulus,flow coefficient and viscous damping of the oil fluid,increase the complexity of the system.Therefore,based on the consideration of these factors,this paper establishes the lumped parameter model of the system,and based on the MATLAB/Simulink simulation environment,studies the influence of system parameters on the system characteristics,and probes into the coupling mechanism of the multi energy domain parameters of the electromechanical system under the combined action of load condition and power source.(2)The principle of kinetic energy stiffness and its detection method.Combining with the dynamic model of the lumped parameters of electromechanical system,this paper puts forward the kinetic energy stiffness analysis method of electromechanical fluid system,points out that the kinetic energy stiffness of the electromechanical system is the ability of the system kinetic energy to resist the external excitation source,and divides it into positive kinetic stiffness and inverse kinetic stiffness two parts according to the It also expounds the significance of its physical meaning and the evaluation of the performance of the MEHS.On the basis of this,the kinetic energy stiffness angle of the operating process is calculated by the variation rate of the multi-source signal in the electrohydraulic system.Using signal modulation technology,the multi-source signal is fused into Lissajous such as graph(stiffness line),and the length of the stiffness line is formatted so that its length and dip angle can measure the kinetic energy stiffness,and the stiffness matching relationship of the system is measured by the tolerance relation of kinetic energy stiffness circle.(3)Mechanism of kinetic energy stiffness change and its correlation with system state.Based on the variable speed hydraulic control platform,the mechanism of the system temperature,motor displacement and the influence of the rotational inertia of the output shaft on the system’s kinetic stiffness are explored,and the correlation between the system efficiency and the speed fluctuation is discussed.The experimental results show that the kinetic energy stiffness of MEHS changes with the variation of the parameters of the system,and the kinetic energy stiffness can be used to characterize the operation of the electromechanical system.(4)On-line measurement system of kinetic energy stiffness and system control strategy evaluation.Based on LabVIEW,the kinetic energy stiffness on-line detection system is designed,which completes the real-time detection and display of kinetic energy stiffness of various subsystems,the collection and display of multi-source signals,the motor speed,the displacement of hydraulic pump and hydraulic motor and the control of simulating loading,the data preservation and so on.Based on the condition of the test-bed,the research on the evaluation of variable speed and volume speed control strategy on the basis of kinetic energy stiffness is carried out,and the application of the theory of kinetic energy stiffness is extended,which provides a new way to carry out the monitoring and performance evaluation of MEHS running condition.