Study On Coupling Dynamics Characteristics Of Mechanism With Multiple Joint Clearances And Component Flexibility

With the development of mechanism in the direction of light, high-speed and precision constantly, some components with light mass and flexible characteristics are applied to mechanism widely. But the coupling effect between elastic deformation and large overall motion of flexible componet has a bad influence on dynamic characteristics of mechanism. Meanwhile, mechanism usually contains multiple joint clearances that make the dynamic response of mechanism deviated the ideal state of motion, and the coupling effect between clearance and elastic deformation of flexible component further affect working accuracy and stability of mechanism. Therefore, multiple joint clearances and component flexibility have become a hot issue in the study of mechanism dynamics, and this paper studies the coupling dynamics of mechanism with multiple joint clearances and component flexibility in order to provide analysis method and theoretical guidance for mechanism design and dynamic behavior prediction of mechanism.The component flexibility of mechanism is considered, and on the basis of flexible multi-body system dynamics theory, the multi-body system dynamics model with flexible component is established. Then joint clearance of mechanism is described reasonably, furthmore the vector model and mathematical model of joint clearance are established. Meanwhile, clearance model is embedded in the flexible multi-body system dynamics model, and the coupling dynamics model of mechanism with clearance and flexible component is established to lay a foundation of subsequent study on coupling dynamics of mechanism with multiple clearances and componet flexibility finally.In order to describe contact-impact process of joint clearance, the normal contact-impact force model and tangential friction force model are established and analyzed. Then on the basis of L-N nonlinear spring-damp contact-impact force model and improved Coulomb friction force model, combining the coupling dynamics model of mechanism with clearance and flexible component, dyna mics of planar four-bar linkage with multiple clearances and flexible linkage is studied, then the effect of clearance and linkage flexibility on dynamic characteristics is studied.Furthmore, the coupling dynamics model of mechanism with clearance and flexible component is applied to aerospace mechanism in order to study the effect of multiple clearances and component flexibility on dynamic characteristics of aerospace mechanism. Firstly, the coupling dynamics characteristics of rigid two-axis-position mechanism with azimuth axis and pitch axis clearance is studied, then the effect of driving moment, friction coefficient, equivalent damping coefficient and contact stiffness coefficient on dynamic characteristics is studied respectively, and the effect law of various factors on pointing accuracy and working stability of mechanism is studied on the basis of health index and dimensionless amplitude effect index.Finally, the coupling dynamics characteristics of driving mechanism with multiple clearances and reflector flexibility is studied. The elastic deformation law of reflector is studied by discretization treatment, and the effect of Elastic Modulus and constraint form on elastic deformation is studied deeply. Furthmore, the effect of clearance on elastic deformation and dynamic characteristics of reflector as well as the effect of reflector flexibility on pointing accuracy and dynamic characteristics of mechanism with clearance are studied. The effect law of constraint form of reflector on dynamic characteristics of mechanism considering clearance and not considering clearance are studied.