By taking planar 3-DOF parallel mechanism as an example ,the mechanism is divided intopole unit and plane triangle unit,and a differential motion equation of the mechanism is established by applying FEM theory.Then the situations of the modal frequency and main vibration mode with the changes of the location and gesture are analyzed-Furthermore ,the dynamics response of mechanism is studied under the driving of the active force and inertia force,and the type of instantaneous vibration is revealed as well as main flexible links are obtained through comparing reality motion with rigid body motion.Thus the variation of location and attitude errors of moving platform is researched under accelerating, uniform velocity and decelerating respectively,from which the dynamic characteristics of velocity and acceleration are acquired, which results show that attitude error and dynamic stress are noticeably increased in the process of accelerating and decelerating of mechanism.%以平面3自由度并联机构为例,将机构划分成杆单元和平面三角形单元,用有限元理论建立机构微分运动方程.分析机构模态频率和主振型随机构位姿的变化情况.研究机构在主动力和惯性力激励下的动力响应,将机构真实运动与其刚体运动比较,揭示了机构瞬时振动的型态,找出了机构主要柔性环节.研究机构在加速、匀速和减速运动状态下,动平台的位置和姿态误差的变化规律,清楚了机构速度和加速度的动力特性,结果显示,在机构加速或减速过程中位姿误差和动应力显著增大.
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