考虑SSI效应的升降作业平台惯容减振优化设计

Optimal design of an inerter dynamic vibration absorber for control of a lifting platform considering SSI effect

升降作业平台在野外工地、河滩等环境中高空作业时,其支腿底盘的明置基础与软土地基会发生动力相互作用,从而改变作业平台系统的动力特性。提出了考虑土与结构相互作用效应下的含3种不同惯容减振系统(SIS,SPIS-1,SPIS-2)的升降作业平台动力学模型,推导了作业平台在简谐激励下的振幅放大因子以及在随机激励下的响应均方值的解析表达式。利用遗传算法分别求解了位于中硬土、中软土以及软弱土3种地基表面的作业平台在H_(∞)和H_(2)优化准则下,惯容减振系统的最优设计刚度比和阻尼比。对最优状态下的各减振系统进行减振效果分析,结果表明:SPIS-2减振系统效果最佳,不仅最大程度地抑制了升降作业平台的共振效应,而且更有效地拓宽频带范围;SSI效应可以降低简谐激励下作业平台的位移振幅放大因子和随机激励下作业平台绝对位移的均方值;SSI效应对简谐激励和随机激励下惯容减振系统的最优设计参数影响很小,因此针对3种惯容减振系统位于不同地基表面下的最优设计参数拟合出经验公式,为升降作业平台的研发和减振设计奠定了理论基础。

When the lifting platform works at heights in the outside field,river beach and other environments,the dynamic interaction between the soft soil and outriggers of lifting platform will change the dynamic characteristics of the lifting platform system.In this paper,three dynamic models of lifting platform,which are incorporated with three different inerter dynamic vibration absorber(I-DVA)systems defined as SIS,SPIS-1 and SPIS-2,are presented with the consideration of soil-structure interaction.The expression of the amplification factor and the displacement mean square value of the operating platform is derived under harmonic and random force excitation,respectively.The optimal stiffness ratios and damping ratios of the I-DVAs are obtained based on H_(∞)and H_(2) optimization criteria by genetic algorithm in terms of three different soil foundations.The vibration reduction performance of three I-DVA systems is evaluated under the conditions of their optimal design parameters.The numerical studies show that:SPIS-2 performs the most effective vibration reduction,which not only suppress the resonance amplitude of the lifting platform,but also widen the frequency bandwidth.The soil-structure interaction can reduce the amplification factor under harmonic excitation and the mean square value under random excitation of the operating platform.The soil-structure interaction influences the optimal design parameters of the inerter systems insignificantly under harmonic and random excitation.Therefore,some empirical formulations of the optimal parameters for I-DVAs are fitted in order to provide reference for the vibration reduction design of lifting platform.