由多个空心结构的物体层层嵌套而组成的多体系统，具有其特有的动力学行为：在物体变形和包括摩擦力在内的层间接触力等因素的耦合作用下，内外层物体间的轴向相对运动会激发整个系统的纵向振荡，常常造成一些大范围伸缩机构，如高空作业车、空间机械臂等在定位控制过程中的种种障碍，迫切需要对这类嵌套多柔体系统的摩擦接触动力学进行更加系统深入的研究。由于内外层物体之间的接触类型属于面-面接触，接触区域也在物体运动过程中不断变化，分别建立每个物体的有限元模型再施加约束的传统建模方式在很多方面都遇到了难以克服的困难。针对这些难点问题，本项目将通过对嵌套多体系统整体建模理论和层间接触面力分布规律的深入研究，提出一种能使所建模型自然满足内外层物体间接触条件的建模理论，以及一种更能反映层间接触力物理本质的接触力模型和相应的离散化方法。在此基础上，结合相关控制理论提出一种能有效抑制伸缩机构中残余振荡的驱动力控制策略。

A prominent characteristic in the dynamics of the multibody system composed by several nested bodies with hollow structure, is its vertical vibration can be excitated by the axial movements of bodies in the system resulted from the deformations and contact forces including frictions, which has been inducing many difficulties in the process of accurate positioning of the work platform of large scale telescopic booms, and motivated a urgent need for the systematically and profoundly investigation in the dynamic contact analysis of such kind of multibody systems. In a nested flexible multibody system, contacts between deformed bodies are kind of surface to surface contacts and their areas change with times, resulting in many hard tasks that can't be surmounted by the traditional methodology in which bodies are discretized separately through finite elements first and then a large number of constraint equations are employed to enhance the conditions of contacts among bodies. In this project, through the study of frictional contacts in nested flexible multibody systems, we would present a quite different methodology in which all the bodies are modeled simultaneously with a common share element shape function, and present a more accurate model of distributed contact forces in the system, and then present an efficient and reliable method of the control of driving axial force in telescopic booms to restrain their residual oscillations.