柔性机构摩擦动态自锁及其波动特性的理论与实验研究

The dynamic self-locking (jam) event, which is closely related to the famous Painlevé paradox in traditional rigid-body frictional dynamics, frequently occurs in the sliding motion of compliant mechanism. The sliding motion of mechanism will transform into a complicated oblique impact in this case. The bouncing motion will occur and the transient waves will be excited and propagate in the mechanical component. They can decrease the running precision and the strength of structure. The aim of the present application program is to solve the above transient dynamics problems by theoretical and experimental methods. Considering the deformation effect and the non-smooth characteristic of frictional contact, the dynamic substructure theory for the dynamic self-locking is developed. The transient mechanics behaviors of some typical mechanism are investigated by the present method. The problem of the establishment of ‘dynamic substructure model’ that has ability to describe wave motion, the compilation of the repeated transition algorithm between slip and stick, the determination of the region of dynamic self-locking, and the computation of contact stress are all solved. The relationship between Painlevé paradox and the dynamic self-locking is discovered. By incorporating with the theory of stress waves, the propagation of the transient waves induced by the dynamic self-locking are analyzed. The rule of the influence of wave propagation on the strength of structure is discussed. Through the above investigations, the theoretical studies on the dynamic self-locking, bouncing and the wave motion characteristic during the friction contact are completed. Meanwhile, the experimental setup and measurement system are established to measure the structure transient response. The numerical results and experemental method are validated by the experiments. The study results of the present program can be a theory basis for the dynamics control and structure optimal design of compliant mechanism.

柔性机构滑动运动时常出现与传统刚体摩擦动力学中著名的Painlevé悖论密切相关的动态自锁（卡阻）事件。此时机构运动将由滑动转变为复杂的斜碰撞，机构出现弹跳并激发瞬态波在部件中传播，易降低运行精度和结构强度。针对上述问题，本项目考虑部件的变形效应和摩擦接触的非光滑特征，提出柔性机构动态自锁动态子结构理论，研究典型机构的动态自锁瞬态力学行为。重点解决能描述波动效应的“动态子结构模型”的建立、粘滑运动状态反复切换算法的编制、动态自锁区的确定以及接触力的计算等基础理论问题。揭示Painlevé悖论与动态自锁之间的关系，并结合应力波理论分析瞬态波的激发和传播机理，探索波传播对结构强度的影响规律，实现对柔性机构摩擦接触中的动态自锁、弹跳及其波动特性的理论研究。同时，搭建实验装置和测量系统，开展动态自锁瞬态响应的实验测试，验证实验方法和理论分析结果，为柔性机构的动力学控制及结构优化设计提供科学依据。

本项目系统性完成对了柔性机构滑动运动时动态自锁（卡阻）事件的研究，尤其是对机构运动由滑动转变为复杂的斜碰撞、机构出现的弹跳以及激发瞬态波在部件中传播进行了系统研究。在理论研究方法上，本项目考虑了部件的变形效应和摩擦接触的非光滑特征，提出了柔性机构摩擦接触理论，用以研究典型机构的动态自锁瞬态力学行为。建立了“完全柔性体模型、编制了粘滑运动状态反复切换算法、确定了柔性体的摩擦动态自锁区以及计算了动态卡阻是接触力的突然跃起等。揭示了Painlevé悖论与动态自锁之间的关系，并结合应力波理论分析瞬态波的激发和传播机理，获得了波传播对结构强度的影响规律。在实验研究方面，本项目完成搭建了实验装置和测量系统，完成了机械臂和机器人相关的摩擦机构动态自锁瞬态响应的实验测试，验证了实验方法和理论分析的结果。理论和实验研究结果均表明，相比大刚度结构，柔性结构大柔度会导致动态卡阻更容易发生，发生参数区会增大，需要柔性机器人在设计时密切注意。本项目的研究成果为柔性机器人的摩擦动力学行为的控制和结构优化打下了重要的理论依据。