Vibration Study Of The 6-UCU Stewart Platform

The parallel mechanism is a closed loop mechanism with two or more than two degrees of freedom.And the parallel mechanism has the advantages of compact structure,high rigidity and strong carrying capacity.It is widely used in aerospace,automotive engineering,biomedical engineering,etc.The Stewart platform is a six-degree-of-freedom parallel mechanism that is well for situations where the operating range is small and the load is large.Many scholars have carried out a lot of work on the performances,structures,optimization and controls of the Stewart platform.Vibrations caused by parallel mechanism will bring many problems.If the parallel machine tool has vibration during operation,it will affect the motion accuracy,reduce the tool life and reduce the production efficiency.It is important to analyze its vibration and to reduce vibration.If we need to study the vibration of the Stewart platform,then we need to study its kinematics and dynamics.This paper studies the 6-UCU Stewart platform.The upper leg and the movable platform are connected by universal joints.The lower leg and the fixed platform are also connected by universal joints.Firstly,the Kane method is used to establish the dynamic equation of the Stewart platform,and the first six natural frequencies are obtained.The virtual prototyping model of the Stewart platform was obtained by using the interface technology of Adams and UG,and then the simulation of kinematics and dynamics was performed by Adams.Secondly,the dynamic model of rigid-flexible coupling of Stewart platform is established to solve the dynamic equation of rigid-flexible coupled Stewart platform.Flexing the six legs of the Stewart platform and adding a spring unit between the upper and lower legs to obtain a "mass-spring-damping" discretization model of the Stewart platform.The equation can be used to simulate the vibration response of Stewart platform,and Adams is used to solve its natural frequency,modal participation factor,transfer function,power spectral density function and so on.Finally,based on the rigid-flexible coupling simulation model of the Stewart platform,the vibration model is damped by adding an appropriate hydraulic damping mechanism to the Stewart platform.The passive vibration reduction analysis of the rigid-flexible coupledStewart platform is carried out to compare the vibration response before and after optimization.Provide theoretical basis for the design of actual institutions in the future.