Dynamic Research Of The Flexible Mechanism Involving Joint Damping

With the increment of the operation speed of machines and the reduction of the mass of components, the joint damping has already been the important factor in the mechanism's dynamic research. Therefore, How to provide an effective model to describe the dynamic characteristics of the system with joint damping is the focus of current dynamic study of mechanism.In this thesis, by means of the Lagrange function, the finite element dynamic equations of the beam element are deduced. Then all the element dynamic equations are assembled into the system dynamic equation through using the Kineto-Elastodynamics theory. The dissipation force derived from joint damping is applied as excitation force of the linkage system. Substituting it into the established system dynamic equation, the system dynamic equation with the equivalent viscous damping coefficient of the joint damping is derived.In order to obtain the equivalent viscous damping coefficient of the joint damping, the angular velocity of the shaft of joint is measured during attenuation. Based on the experiment data of the angular velocity, the expression of the angular velocity is fitted by means of the least square method. Comparing the fitted expression with the established theory expression of the angular velocity, the equivalent viscous damping coefficient is gained.The closed form algorithm of the state space method is employed to solve the system dynamic equation with time-varying coefficients. The dynamic problem of a linkage mechanism with four joints is taken as example to show that the presented models and methods are correct and practicable.The time series method is introduced to identify the modal parameters of a clamed beam. A spring-mass system with three degree-of-freedom is taken as example to show the correctness of the method and the program compiledfor this method.Lastly, computer programs for the dynamic analysis and time series method are compiled in Matlab.