Research On Nonlinear Dynamic Characteristics And Reliability Analysis Method Of Hydraulic Cylinder

At present,with the development of hydraulic cylinder drive control device to the direction of high precision,the demand for its dynamic characteristics is getting higher and higher.In the process of system motion,many performance parameters often have implicit and nonlinear characteristics.In order to improve the reliability of implicit nonlinear structures,scholars at home and abroad have carried out a lot of research work and achieved a lot of results.In this paper,the generation mechanism of system nonlinear spring stiffness and the change of time-varying friction force are expounded,and the essential causes of the phenomenon of self-excited vibration and forced vibration of hydraulic cylinder drive control device are explored.Main research contents include:(1)Analysis of nonlinear dynamic characteristics of hydraulic cylinders under static load and alternating load : When the hydraulic cylinder moves at a low speed,the phenomenon of slow and rapid self-excited vibration will appear,and the phenomenon of forced vibration will occur under the action of alternating and impact load,which seriously affects the stability and accuracy of its drive control.Through in-depth in this paper,the system with time-varying friction mechanism of nonlinear spring stiffness change situation,to explore the cause hydraulic cylinder drive control device of self-excited vibration and forced vibration phenomenon of the nature of reason,on the basis of this theory based on differential equation and dynamics model,using modern computer technology to the numerical simulation analysis and research,to reveal the effect of the hydraulic cylinder dynamic characteristic in the working process of the factors and change rules.(2)A reliability sensitivity analysis method for implicit engineering structures is proposed : Many dynamic performance parameters of hydraulic cylinders have implicit characteristics.For implicit engineering structures,on the basis of a reliability analysis method,through the forward or center difference method for gradient information,and iterative search structure equation of state(or functions)limit state checking point on the surface,using a check point hyperplane instead of the original,the structure of the implicit limit state surface for reliability and reliability sensitivity to solve.Examples show that the proposed method has less sampling times and higher accuracy.Thus,it provides a reference for the reliability analysis of large implicit engineering structures.(3)A reliability sensitivity analysis method for implicit and strongly nonlinear engineering structures is proposed:Due to the complexity of the engineering structure,the model has not only implicit feature,but also strong nonlinear feature.A new sampling fitting method is proposed to analyze the reliability sensitivity of engineering structures with implicit and strong nonlinear characteristics.Firstly,the checking points are obtained based on the reliability analysis method.After that,the other training sample points near the limit state surface were found repeatedly through the high-gradient search method.Finally,the limit state equation of the structure is fitted by polynomial function or response surface function,and then the reliability sensitivity of the engineering structure is analyzed.Numerical and engineering examples show that the proposed method has high accuracy and efficiency.