On Dynamic Modeling Of Mechanical Pair Clearance

The dynamic effects of flexibilities of members and joint clearances in the mechanisms are a challenge to theoretical analysis and yet are among the most important factors that must be considered when designing and manufacturing a spacecraft. The research on the theory of multi-body system with joint clearances and the dynamics of deployable mechanism will provide the analysis method and theoretical basis for the design of space mechanisms and prediction of their dynamic behavior. Study on these problems has profound theory and application value.In this thesis, the limitation of the existing clearance models are discussed.To overcome the limitations, a new surface-to-surface contact clearance model is proposed. This new clearance model, considering the effects of the figure of joint, the magnitude of clearance, the property of material and speed of impact,accurately simulates the impact behavior, including the phenomena of stick-slip and rolling friction. In order to investigate the dynamic effects of flexibilities of members and joint clearances, the equation of flexible multi-body system with joint clearances was derived based on the flexible multi-body theory. Further, a deployable mechanism was studied through simulations.The two-link robot manipulator mechanism was studied using numerical simulation. The simulation results show that the flexibility of members, the magnitude of clearances at the joints, material damping, impact damping, friction and gravity affect the dynamics of the mechanism. The joint clearances cause severe impact. The coupling of the clearances, flexibility and friction enhance the nonlinear behavior, and even cause chaotic vibration.