With the increasing application of flexible parallel manipulator in industrial production,its light weight and high speed characteristics have also fully been reflected,but it also creates problems of elastic vibration.Therefore,it is important to establish an effective dynamic model.In this paper,with planar 3-RRR flexible parallel manipulator as the research object,due to the complexity of the dynamic model of a planar 3-RRR flexible parallel manipulator,it is often difficult to achieve active vibration control algorithm based on the system precise dynamic model.In order to establish a simple and efficient dynamic model of the planar 3-RRR flexible parallel manipulator to study its dynamic characteristics and build a controller based on this model,firstly,considering the effect of rigid-flexible coupling and the moment of inertia at the end of the flexible intermediate link,the modal function is determined with the pinned-free as boundary condition of the flexible intermediate link.Then,based on the extended Hamilton principle and the assumed modal method(AMM),considering the main vibration modes of the system,a high-efficiency coupling dynamic model is established on the basis of guaranteeing the model control accuracy.According to the model,the characteristics of the first two orders vibration responses of the flexible intermediate link are analyzed.Through Fast Fourier Transform(FFT),the spectrum characteristics are studied in the frequency domain.The results show that the model can effectively reflect the main vibration modes of the planar 3-RRR flexible parallel manipulator,in addition the model can be used to analyze the effects of inertial and coupling forces on the dynamics model and the drive torque of the drive motor.It is found that the inertial force and the coupling force can cause the forced vibration,and the vibration frequencies are 24.88Hz and 49.75Hz,as well as the driving torque of the motor does not exceed 20N·m which can provide a basis for motor selection.Because this model is of the less dynamic parameters,it is convenient to carry out the control program implementation.The rigid-flexible coupling dynamics modeling method proposed in this paper is applicable to all kinds of FPM with flexible link.The model has high precision and high efficiency,which solves the problem of complexity of dynamics model and is of great significance to the controller design based on the dynamic model.