Dynamic characteristics analysis of hydraulic pipes on anti-rolling Suspension system

Abstract

Based on power bond graph-block diagram method,the general mathematical models of the suspension cylinder, hydraulic pipes and accumulator are established,and the simulation model is established based on SIMULINK control simulation software. A heavy-duty anti-rolling suspension system is used as a study object,quantitative analyzing the dynamic characteristics response of hydraulic pipes on heavy-duty anti-rolling suspension system under different frequency.The results show that the hydraulic pipes’ inertia effect, flow resistance losses and pipe wall elasticity have great impact on the dynamic performance of hydraulic system, especially the high frequency servo hydraulic system. Introduction Heavy-duty anti-rolling suspension system is used to suppress rolling trend and improve the driving safety while driving, A heavy-duty truck anti-rolling suspension system with poor running smoothness is due to the smaller size of the pipe between the external accumulator and cylinder.Hydraulic pipe is the important component of the heavy-duty anti-rolling suspension system, the hydraulic pipes’ inertia effect, flow resistance losses and pipe wall elasticity have great impact on the dynamic performance of hydraulic system, especially the high frequency servo hydraulic system. Many papers in establishing the hydraulic system models usually ignore or simplify the influence of hydraulic pipes on hydraulic system.In fact, the influence of hydraulic pipes parameters on hydraulic system, especially the high frequency servo hydraulic system dynamic response should not be ignored. Pipes have capacitive,resistive and sentimental effects which are distributed on the entire road。 At present, the main research methods on dynamic characteristics of pipes are method of characteristics,frequency method,distributed-parameters bond graph method and so on。 Sectional lumped parameter method is one of the frequency method,which is suitable when the pipeline is short,the frequency pulse is low, or a larger error occurs;For the high-precision processing on the friction,the recursive algorithm of the method of characteristics is regular and accurate,but for the boundary value problems and the difficulties in connecting to related fluid component models,the method of characteristics used in practical engineering is limited; Distributed-parameters method is one of another frequency method,which is accurate in studying pipes。 This paper uses lumped parameter pipeline impedance with limited number to replace Distributed-parameter pipeline impedance approximately and the sectional lumped parameter method which simplifies the transfer matrix to create bond graph model of hydraulic pipeline, simultaneously,referring to method including dynamic friction put forward by LI Hong-ren and CHENG Zhao-di,it amends the sectional lumped parameter model。 In this paper, a heavy-duty truck anti-rolling suspension system with external accumulator is studied as an object, studying the hydraulic pipe parameters between the cylinder and the accumulator influence on the dynamic characteristics of the anti-rolling suspension system, the 5th International Conference on Information Engineering for Mechanics and Materials (ICIMM 2015) © 2015. The authors Published by Atlantis Press 605 physical model of the anti-rolling suspension system,including pipes model is established based on power bond graph-block digram modeling throry, the dynamic simulation model is set up using SIMULINK,mainly studying the influence of pipe parameters between cylinder and accumulator on dynamic characteristic of the anti-rolling suspension system. Physical and Simulation Model Heavy-duty anti-rolling suspension system is a nonlinear system, the physical model can be simplified an equivalent dynamic model as shown in figure 1, the equivalent model compses of cylinder, accumulator, hydraulic pipe, equivalent resistance components and sprung mass, etc. Fig.1 Simplified model of anti-rolling suspension system Fig. 2 N section bond graph model of hydraulic pipe The diagram 2 is the bond graph model of pipe divided into N segments. 1 f R / 2 f R —static friction fluid resistance, 5 − ⋅ ⋅ m s N 。General expression 4 128 d l R f π ρυ = ( ρ -fluid density, 3 − ⋅m kg ;υ -fluid movement viscosity, s m / 2 ; l -pipe length,m; d -pipe diameter, m ) ; 1 d R / 2 d R — dynamic friction fluid resistance , 5 − ⋅ ⋅ m s N 。 General expression f d R r l R 6392 . 0 ) / ( 987 . 1304 − = ; 1 I / 2 I —fluid sense, 4 − ⋅m kg 。Linear expression A l I ρ = ( ρ -fluid density, 3 − ⋅m kg ;l -pipe length,m;A -pipe cross-sectional area, 2 m ); 1 C / 2 C —fluid capacity, 1 5 − ⋅ N m 。Linear expression ) 1 1 ( 2 0 f w K E l r C + = π ( w E -pipe volume elastic modulus,Pa; f K -fluid volume elastic modulus, Pa). The simulink simulation model is shown in figure 3.