摘要
蓄能器内氮气多变过程模型的精度是影响油气悬架系统特性分析的关键因素之一。为了更加精准地描述蓄能器内氮气的真实多变过程,该文利用蓄能器试验台开展了蓄能器不同振幅和频率的正弦激励试验,通过试验数据综合分析发现氮气体积压缩率和体积压缩速率与气体压力呈一定线性关系。在此基础提出了一种基于体积压缩率和体积压缩速率的真实气体多变指数模型。为了验证模型的正确性和准确性,通过蓄能器试验数据对提出的多变指数模型中的2个变量系数进行辨识和模型仿真结果的对比验证,并利用6个悬挂缸的整车油气悬架系统试验平台对模型进行试验验证,结果表明:仿真预测结果与试验数据的平均误差为5.12%,最大误差小于10.9%,满足工程设计的要求。该囊式蓄能器的气体多变指数模型为更加准确研究油气悬架系统真实特性奠定了基础。
One of the problems in the analysis of the dynamics performance of off-road vehicles is the effect of the accuracy of the hydro-pneumatic suspension model.However,the accuracy of the model for the polytropic process of nitrogen in the gas-charged hydraulic accumulator is one of the key factors,which affects the accuracy of the model for the hydro-pneumatic suspension systems.The traditional approach based on the energy equation and the Benedict-Webb-Rubin equations deduces the well-known thermal time constant model.However,researchers indicate that the thermal time constant varies with the change in the accumulator size and operating cases.Other researchers attempt to modify the multivariate index to model the real gas behavior,but the hysteresis loop representing the energy losses in a cycle can’t be described because the multivariate index is treated as a constant value.In this paper,an attempt was made to describe the hysteresis loop by adopting a variable multivariate index.On the accumulator rig,some tests excited by the sinusoidal displacement with four different amplitudes and frequencies respectively were carried out.The plots of the gas pressures versus the gas volume ratio and the gas volume rate respectively were made according to the experimental data from the accumulator test by using the Matlab software.A comprehensive analysis of experimental data showed that the relationship between the gas pressure and both the volume compression ratio and the volume compression rate were very close.To analyze the relationship between the multivariate index and the two parameters respectively,the formula of the multivariate index was deduced based on the ideal gas approach and multivariate index.By substituting the experimental data from the accumulator test into the formula,the plots of the multivariate index versus the two parameters respectively were also made.The plots illustrated that the multivariate index was closely proportional to the two parameters,respectively.Based on the analysis,a novel method was proposed to build a multivariate index model with the two parameters to describe the real gas behavior.In order to verify the correctness and the accuracy of the proposed multivariate index model,the two coefficients in the model were identified by using the experimental data from the previous accumulators test,and the coefficient of the volume compression ratio in the model was 2.4 for the test accumulator,and the coefficient of the volume compression rate was 1.5.Moreover,substituting the values of the two parameters,which were determined by the different operating cases,into the proposed multivariate index model with the two identified coefficients gave a comparison with these experimental data.Furthermore,a co-simulation model,which was based on the multivariate index model,for six hydro-pneumatic suspension systems was built to check the application of the multivariate index model in the hydro-pneumatic suspension systems of the overall vehicle.And a platform for the hydro-pneumatic suspension systems of the overall vehicle invented and designed by our laboratory,which was the first platform with the capability to test the comprehensive characteristics of multiple suspension systems,was used to test the rolling characteristics of the six hydro-pneumatic suspension systems.Several tests were carried out under the sinusoidal displacements with four different amplitudes and frequencies,respectively.The comparison of the co-simulation results and experimental data showed that the average discrepancy was equal to 5.12%and the maximum discrepancy was less than 10.9%.Therefore,a good correlation was achieved.It further demonstrated that the proposed multivariate index model can describe the behavior of the real nitrogen in the accumulator.But the proposed model should be further verified by using more experimental data from much higher frequency tests,and the influence of dissipated energy on the two coefficients in the proposed model should be explored.
作者
王云超
魏彬
杨岳霖
Wang Yunchao;Wei Bin;Yang Yuelin(College of Mechanical and Energy Engineering,Jimei University,Xiamen 361021,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2019年第20期10-16,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金资助项目(51575233)
关键词
车辆
试验
模型
悬架
蓄能器
迟滞环
vehicle
experiments
models
suspensions
hydraulic accumulator
hysteresis loops
